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2024 | Book

2023 Asia-Pacific International Symposium on Aerospace Technology (APISAT 2023) Proceedings

Volume I


About this book

This book is a compilation of peer-reviewed papers from the 2023 Asia-Pacific International Symposium on Aerospace Technology (APISAT2023). The symposium is a common endeavour among the four national aerospace societies in China, Australia, Korea and Japan, namely, Chinese Society of Aeronautics and Astronautics (CSAA), Royal Aeronautical Society Australian Division (RAeS Australian Division), Japan Society for Aeronautical and Space Sciences (JSASS) and Korean Society for Aeronautical and Space Sciences (KSAS). APISAT is an annual event initiated in 2009. It aims to provide the opportunity to Asia-Pacific nations for the researchers of universities and academic institutes, and for the industry engineers to discuss the current and future advanced topics in aeronautical and space engineering.

This is the volume I of the proceedings.

Table of Contents

Research on Optimization Design Method of Autonomous Deformation Decision for Intelligent Morphing Aircraft

Intelligent morphing aircraft can timely and independently change its shape according to the flight mission and environment, and meet different flight missions with different aerodynamic layouts, so as to achieve performance improvement and trajectory optimization in different flight stages. So it is also one of the development trends that is most likely to bring about the technical revolution of the future aerospace aircraft. In order to improve the trajectory characteristics, it is necessary to establish the controlled model in advance by using traditional controller to control structural changes. However, due to obvious changes in the structure of morphing aircraft, it is impossible to establish accurate mathematical model. Therefore, an intelligent trajectory optimization method is proposed to solve the problem of aircraft autonomous deformation decision control. This paper takes intelligent morphing aircraft flying at high speed in large airspace as the research object, aiming at the technical problems that the aircraft is difficult to obtain sufficient deformable flight test data in advance, which leads to the difficulty in predicting the optimal aerodynamic shape under different flight states, and the traditional controller cannot be used to optimize the deformation. A deformable decision scheme based on reinforcement learning (RL) network is proposed, which realizes that the aircraft structure can be changed independently according to the real-time state in flight, so as to improve the aerodynamic performance and optimize the flight trajectory.

Dan Xu
Research on Lateral Unmatched Nonlinear Control of UAV Based on L1 Adaptive Control Theory

Aiming at the dimension unmatched in the lateral nonlinear control of UAV system, and the problems of high-frequency oscillation and uncertainty caused by high adaptive gain in the lateral nonlinear control of UAV in the case of traditional adaptive control method, a lateral control method of UAV Based on L1 adaptive unmatched nonlinear is proposed in this paper. Firstly, taking a scaled down UAV in the laboratory as the prototype, the lateral dynamic model of the UAV system in the case of unmatched nonlinearity is derived. Through the derivation of the lateral nonlinear model, it is designed in the form of L1 control. Then, based on L1 adaptive control theory, the state observer, adaptive gain and control law of the model are designed, and it is proved that they meet the stability conditions. Finally, the designed L1 adaptive control system is simulated and verified by a scaled down UAV in the laboratory. The results show that the designed control system can not only ensure the rapidity of the system, but also have strong robust self-adaptability, make the tracking error converge quickly and have excellent transient performance.

Liangliang Wang, Shuang Zhang, Dong Wang
Reconstruction and Prediction of Multiparametric Steady Flow Field Based on POD

The technology for fast flow field reconstruction and prediction with high accuracy and efficiency is more attractive than computational fluid dynamics (CFD) from the perspective of time and computing consumption. The proper orthogonal decomposition (POD) technology has shown its capacity to reconstruct and predict various physical fields. The present study proposes a method based on POD for the reconstruction and prediction of the multiparametric flow field using a uniform POD mode set. In the traditional POD procedure, a few POD modes with maximal eigenvalues (ME) are selected to represent the original system so that the global system error is minimized. To improve the accuracy of reconstruction or prediction of the flow field under a certain condition, the POD mode selection method is modified. It’s proposed to select the POD modes with the maximum magnitudes of POD coefficient (MC) to reconstruct or predict the flow field instead of the POD modes with the maximum eigenvalues. To validate the feasibility of this POD modes selection method, the velocity and pressure distributions around a 2-dimensional aerofoil NACA0012 are adopted as the steady flow field to be reconstructed and predicted. Flight speed and angle of attack of the aerofoil are used as two independent parameters that determine the flow field. The Lagrange multivariate function interpolation is applied in this paper to calculate the POD coefficients in terms of any combination of both independent parameters. Compared with the traditional ME, a significant accuracy improvement is obtained by MC not only in the reconstruction of an individual flow field included in the original data set but also in the prediction of the flow field with a specified condition.

Jianhua Zhou, Xiangchen Du, Yu Wang, Guiying Su, Wei Li
Application and Research of Composite Parts Manufacturing and Assembly on Aircraft Engine Nacelle Torque Box

The quality of aircraft components is directly related to the quality, safety, performance and flight life of aircraft, The only way is to strictly control the quality of aircraft materials and parts processing, and strictly control the design, production and assembly of aircraft, Can control the quality and performance of the whole aircraft assembly, to ensure safety and prolong the life of the aircraft. The use of composite materials not only improves the strength and safety of aircraft, but also reduces the weight of aircraft and increases the effective load of aircraft, which is a major breakthrough in the aircraft manufacturing industry. “High performance, low cost and multi-function” is the development direction of composite materials in the future, while low-cost manufacturing technology is the development focus of composite materials in the future. Low-cost raw materials, rapid prototyping process technology, large-scale, integrated and integrated products are the core of the development of composite materials in the future.The aircraft engine nacelle torque box project is developed, produced, inspected and delivered in accordance with the numerical models and drawings provided as well as delivery specifications. The torque box of engine nacelle is an important component of aircraft, and the amount of composite material accounts is more than 60%. Advanced composite materials have the advantages of light weight, high specific strength, high specific stiffness, strong designability, good fatigue fracture resistance, corrosion resistance, good dimensional stability and easy to form a large area, at the same time, the use of integral manufacturing technology can greatly reduce the number of parts and fasteners, reduce structural weight, reduce production costs. In view of this, the research and development of aircraft torque box products to reduce the weight of aircraft, increase the payload, simplify the aircraft process equipment, reduce the assembly workload, to shorten the development cycle and reduce the cost of aircraft development is of great significance. Briefly introduces the structure of the torque box of aircraft engine, and systematically analyzes the application process of digital composite parts manufacturing and assembly on the torque box of aircraft. The manufacturing and assembling process of composite parts are studied, and some processing technologies of composite parts are analyzed.

Shengxiong Li, Jian Zhou, Zeyan Li, Deliang Li
The Roll Dynamic Instability Mechanism and Deformed Wing Improvement

In recent years, the un-commanded lateral motions at high subsonic and transonic speeds, which are able to induce the mishap of the aircraft, has become a popular research issue. However, dynamic instability mechanism and control or alleviate methods are still a key issues for the resolve of the un-commanded lateral motions. This exploratory research performed to investigate the cause of non-linearity and the destabilizing mechanism due to the presence of asymmetric body vortex or wing/body bound vortex breakdown phenomenon. The focus of the effort is on developing the free oscillation test techniques and a nonlinear dynamic analysis method for identifying the non-linear aerodynamic, combined laser vapor screen flow visualization technique for observing the flow structures and building the vortex control or alleviate methods. The results of free oscillation experiment and laser vapor screen flow observation discovered that the subcritical type asymmetric wing/body bound vortex breakdown gives rise to a key effect on the non-linearity and dynamic instability of roll motion, and proved that the innovative morphing wing could adjust the unstable roll motion of the baseline wing and delay the wing/body bound vortex breakdown by increasing wing bound vortex strength and suppressing body vortex evolvement.

Nong Chen, Guangsen Jia, Shuai Wen, Rui Ye
Coupling Dynamic Characteristics Analysis of a Dual-Rotor Aeroengine

Aiming at the typical dual aeroengine with inter-shaft bearing, the dual-rotor dynamic analysis model was established. The dynamic characteristics induced by the high pressure rotor excitation of the co-rotating, counter-rotating system and the inter-shaft bearing were thoroughly analyzed. Results show that the critical speed of the co-rotating system was much higher than the counter-rotating system, resulting from the gyroscopic moment. Consequently, the rotor strain energy was lower and the rotor unbalance would generate lower dynamic response at critical speed. More importantly, the critical speed of high pressure rotor and low pressure rotor coupling mode (HLCM) would lead to the dramatic increase of coupling vibration. To be specific, the shaft axis locus demonstrated an obvious petal-like shape and the reaction force of the inter-shaft bearing rose significantly. The findings highlight the importance of maintaining sufficient margin between the critical speed of HLCM and the engine operating speed during the rotor dynamic characteristics design.

Xiaofei Ding, Mingfu Liao, Zengde Shao, Yixiong Liu
CFD Modeling of Sustainable Aviation Fuel Sensitivity on Aero-Engine Combustor

Sustainable aviation fuels (SAFs), which is produced from alternative sources, such as bio-derived feedstocks, provide essentially identical performance to that from petroleum-derived jet fuels. SAFs are identified as the best near- to mid-term solution for reducing carbon emissions, with carbon offsetting being the other major carbon mitigation strategy. The primary objective of the research in the paper is to determine if state-of-the-art computational fluid dynamics (CFD) models could predict the fuel effects in a realistic combustor as a pathway for original equipment manufactures (OEMs) to assess the risk of their combustor designs using SAFs. In order to develop a numerical simulation method of SAFs combustion, a simplified chemical reaction kinetic model has been developed to simulate the combustion of a SAF fuel, G + FT, selected for study. In this paper, Hybrid Chemistry (HyChem) method has been referred to reduce the kinetic models to small sets of species and reaction steps that enable CFD simulations. First, a surrogate fuel which contains 56% n-dodecane and 44% iso-octane in mole fraction has been proposed to mimic the G + FT fuel. Second, the HyChem method is applied to the surrogate fuel to establish the simplified mechanism which consists of 43 species and 293 steps, and the number of steps is only 10% of that in the detailed mechanism. Then, we have validated the accuracy of the simplified model with G + FT fuel’s combustion testing data. For example, the average relative error of the predicted laminar flame speed is only 8.8%. Besides, the simplified mechanism has been successfully applied to the CFD modeling. In order to study the fuel sensitivity and verify the CFD modeling with the simplified mechanism, we have conducted a series of combustor rig tests with a conventional petroleum-derived fuel (RP-3) and a blend fuel (90% RP-3: 10% G + FT). Relative difference in simulated values of combustion efficiency, NOx emission and pattern factor due to the change from RP-3 to lend fuel is less than 5%. And fuel sensitivity error between modeling results and testing data in combustor outlet temperature profile is less than 10%. Therefore, the simulation results show that the CFD modeling approach used in this paper can reveal fuel sensitivity and predict fuel effects on a realistic combustor, which can be applied to access the risk of using SAFs in aero-engines later.

Songyang Li, Ruixin Wang, Wenjie Tao
Preliminary Study of High Mach Arc Aerodynamic Test Wind Tunnel

The construction of a high Mach number aerodynamic test wind tunnel needs to solve two technical challenges: one is to solve the problem of anti-condensation heating of the test airflow, and to develop a high-temperature heater; Another is to solve the quality problem of wind tunnel flow field. For the first issue, when the Mach number is less than 10, conventional high Mach aerodynamic test wind tunnels generally use resistance heated heaters as much as possible to reduce the impact of combustion pulsation and combustion products on the test results. When the Mach number is greater than 10, the anti condensation temperature of the high Mach wind tunnel will reach 1200–3000 K, which conventional storage-type heaters cannot reach. The Russian T-117 high Mach aerodynamic wind tunnel, as a precedent, uses arc heaters. Arc heaters are currently mainly used for aerodynamic thermal effects research in high Mach flight aerodynamic thermal tests. The aerodynamic thermal tests focus on flow field parameters such as enthalpy and pressure, while the requirements for repeatability and uniformity are not as high as those for aerodynamic tests. If a conventional arc heater is directly used as a high Mach wind tunnel heater, it will not meet the requirements for aerodynamic test flow field quality. There are some problems in solving the quality of the flow field at the outlet of the arc heater nozzle: one is to reduce the pulsation of the arc operation and improve the stability of the temperature and pressure parameters in the flow field over time. The second is to weaken the rotation of the airflow and enhance the spatial uniformity of the flow field. The third is to figure out what the test medium is, which means to investigate the gas component and proportion. This article mainly discusses the problem of insufficient flow field quality when using arc heaters for aerodynamic tests, and proposes three research directions to solve the problem of flow field quality at the outlet of arc heater nozzles, providing reference for the research work of arc heaters used for high Mach aerodynamic tests.

Tingting Zhang, Jian Lin, Zhenle Qu, Yue Guo
Preliminary Exploration of Hypersonic Wind Tunnel Inlet Test Method

Test method for inlets in general hypersonic wind tunnel FD-07 are summarized, including force measuring test, pressure measuring test, heat flux measuring tests and control tests of boundary layer transition. Force tests, which are overall tests of air-breathing hypersonic flight vehicles, mostly measured the coupling effect of inlet internal flow and outer flow around the aircraft on the overall aerodynamic force when the inlets worked under different conditions. Force tests could also simulate flight height by regulating jet flow pressure ratio. With higher pressure ratio, normal force increased and axial force decreased. Pressure tests mainly simulated the inlet working condition in different compression ratios and back pressures, which could be used to observe the change of pressure in inlet starting, critical starting, and non-starting conditions and the inverse process. With back pressure rising, shock waves were pushed out of the cowl and once surge happened, the shock waves at the cowl concussed at an unstable condition. Heat flux measurement results in general hypersonic wind tunnels showed distinct characteristics of separated flow that sharp fluctuation of heat flux are presented on the surface of channel downstream the cowl. In the tests of boundary layer control, the addition of compulsive transition strip on the fore body compression surface could eliminate the separated region efficiently, thereby maintaining the inlets capability.

Tingting Zhang, Lijun Xie, Xianzheng Zeng
Magnus Moment Calculation of M910 Spinning Projectiles

Tactical weapons such as missiles, rockets, and artillery shells (referred to as missiles and arrows) typically use a spinning flight mode around their body axis during flight to improve their flight stability. However, when the angle of attack and rotation exist at the same time, due to the distortion of the flow field boundary layer and centrifugal force factors, the pressure distribution on both sides of the missile body is asymmetric, resulting in an additional lateral force—Magnus force. The Magnus force is generally small, about 1–10% of the normal force, but the resulting Magnus torque can affect the directional dynamic stability of the projectile and reduce the shooting accuracy. Therefore, accurate prediction of spinning aerodynamic characteristics becomes an inevitable requirement for missile design, ballistic calculation and stability research. However, due to complex aerodynamic disturbances, such as the coupling of low-speed wake flow and forced rotational motion, the aerodynamic forces and moments acting on the projectile exhibit strong nonlinear and unsteady characteristics, posing a challenge for accurately predicting the aerodynamic characteristics of the projectile.Liu Zhou et al. found that there is a certain difference between the calculation results of the RANS equation for high-speed spinning projectiles with a large angle of attack range and experimental data. The calculation results using the Delayed Separation Eddy Simulation (DDES) method have shown significant improvement. Comparative studies have shown that the position of the separation point has a significant impact on the Magnus effect. This indicates that the DDES method has great potential for improving the numerical simulation accuracy of the Magnus effect of spinning projectiles.The main purpose of this article is to compare the applicability of the RANS turbulence model and the DDES turbulence model for numerical simulation of spinning projectiles. The numerical simulation of a high-speed spinning M910 projectile was conducted. From subsonic to supersonic speeds, the results calculated using RANS method for normal force, pitch moment, normal force center of pressure, and roll damping are in good agreement with experimental data, with a deviation of within 10%. The calculation results showed that for the Magnus moment, in the subsonic and transonic velocity ranges, the RANS method calculated results were significantly different from the experimental results, while the DDES hybrid method was in good agreement with the experimental results, and had better regularity compared to the DES method. The main difference between the RANS method and the DDES hybrid method is the wake flow. The RANS method produces a steady wake, while the DDES hybrid method produces an unsteady wake.

Lijun Xie, Tingting Zhang, Zhou Liu, Yunjun Yang
Numerical Simulation and Experimental Verification on the Effects of Vibration Suppression of HPT Blades

This paper aims to investigate the effects of the prism-type under-platform damper (PTUPD) for the high pressure turbine (HPT) blade using theoretical analysis and experimental approaches. The investigated HPT blade has witnessed a rupture failure at the root during the engine test. A thorough failure analysis was performed to identify the failure mode. Furthermore, the crack propagation simulation was carried out to deeply understand the failure mechanism. High cycle failure (HCF) characteristics were observed and the crack initiation life accounted for more than 80% of the total propagation life. Afterwards, the response with the deliberated PTUPD structure was compared with the baseline in both simulation and test. Results show that the maximum response was about 0.45 mm using the PTUPD whereas the response for the baseline reached 0.72 mm. Meanwhile, the frequency has shifted from 3050 to 3150 Hz, moving away from the resonance region. Dynamic response was measured by performing the rotational excitation test and a 60% stress reduction was observed with the PTUPD mounted. Finally, the parametric analysis results reveal that the additional vibration suppression effects is negligible when the PTUPD mass exceeded 6 g.

Yunwu Wu, Yixiong Liu, Xiangping Wang, Jia Li, Chuanyu Du, Tianzi Zhang
Propulsive/Aerodynamic Coupled Characteristics of the Distributed-Propulsion-Wing in Hover and Forward Flight

Based on the background of distributed hybrid electric propulsion aircraft technology, this paper conducts numerical simulation and analysis on propulsive/aerodynamic coupled characteristics of the distributed-propulsion-wing (DPW) in hover and forward flight, both the mutual interference between internal and external flow and the inner correlation between the PW unit and the overall DPW object are discussed, and the outer duct-wing camber influences on the DPW cruise performance are also studied. The results indicate that the present DPW cluster mode has little impacts on its hovering performance, but its aerodynamic performance at cruise depends on the propulsive thrust level to certain extent. Besides, the span-wise lift and drag distributions of the DPW model are very similar to that of the reference conventional wing, which means that the relationship between the PW unit and the overall DPW model is very similar to that between the conventional airfoil and wing. In addition, the outer duct-wing camber influences are mainly manifested in changing the external flow pressure distributions, and the variation trend is consistent with that caused by camber changes of conventional wings.

Kelei Wang, Zhou Zhou
Numerical Study of Flow and Heat Transfer in a Cavity by Lattice Boltzmann Method

In this paper, the aircraft cabin is abstracted as a two-dimensional cavity. To save the energy and implement the green aviation, we simulate the flow and heat transfer in the cavity to ensure the arrangement of heating device in the aircraft cabin. Based on the lattice-Boltzmann method coupled the double distribution function model, the paper adopts D2Q9 velocity discrete model, which has nine different discrete velocity directions. And then calculates and analyzes the influence on the flow and heat transfer characteristic of different heater parameters and different Rayleigh numbers, so that we can obtain the optimal arrangement of heating device in the aircraft. The result show that heating parameters and Rayleigh numbers have great influence on the flow and heat transfer in the cavity. For example, with Rayleigh number increasing and heating position lower, the convective heat transfer intensity become greater. With the Rayleigh number decreasing, the convective intensity get the maximum value gradually when the heater located in the middle of the wall. When the Rayleigh number is fixed, the heat coverage area increases, the convective intensity decreases, the central axis velocity increase gradually, the velocity gradient increases and the flow change greatly. And the variation of flow function and isotherm are greatly affected by Rayleigh number, just like the classical natural convection in the cavity. Besides that, Rayleigh number has different effects on different heater parameters for the flow and heat transfer in cavity. The effect on the velocity distribution decrease gradually with the increase of Rayleigh number, while the effect of heating position on the flow and heat transfer increase with the increase of Rayleigh number.

Xinyu Meng, Bo An, Weimin Sang
Residual Strength Evaluation of Multi-site Damage Structures with Irregular Cracks

Multi-site damage is an important damage mode to be considered in the aircraft design stage, which significantly reduces the residual strength of the aircraft structure and threatens its reliability. The objective of this paper is to propose an efficient engineering approach of residual strength for multi-site damage structures with three types of cracks: non-collinear cracks, inclined cracks and inclined hole-edge cracks. Additionally, the numerical analysis based on elastic-plastic finite element method were conducted to obtain the load-carrying capabilities of multi-site damage structures. The results obtained by elasto-plastic FE model were consistent with experimental results, and the maximum error was only 5.53%, which were more precise compared with the ones of the engineering approach. Yet we recommended to apply the engineering approach to analyze the residual strength of these typical multi-site damage structures in view of its convenience and simplicity of aeronautical application.

Shaopu Su, Xianmin Chen, Lei Li
Optimizing Hydrogen-Powered Aircraft Fleet Operations: A Mixed Integer Optimization Approach with Carbon Emission Consideration

Location selection of hydrogenation stations are critical for the operation of hydrogen-powered aircraft due to the high investment costs and aircraft operating cost. The objective of this study is developing a mixed integer optimization model to solve the integrated fleet assignment and hydrogenation station location problem. In this model, hydrogen-powered aircraft are restricted to refuel at hydrogen-powered airports with hydrogen consumption cost associated with aircraft types. Unlike traditional fleet assignment problems, we are considering pure-hydrogen fleets with the goal of minimizing costs. Due to computational challenges in large problem instances, We introduce complex networking and illustrate how it can deliver high-quality solutions for large cases in a shorter computational time. The model was tested in both regional and non-regional case studies, involving Delta Airlines in the United States, which has 200 flights and 55 airports. The compact model formulation enables fast computation. This work represents an initial step towards the integration of hydrogen energy fleets into the existing aviation market.

Jiaxuan Wu, Xiaoqian Sun, Yifan Xu, Sebastian Wandelt
Skin-Friction Topology on Axisymmetric Boattail Models by an Optical-Flow Algorithm with a Sub-grid Function

Skin friction along with pressure and temperature is an important parameter in fluid mechanics. This study presents the results of skin-friction patterns on axisymmetric boattail surfaces by a sub-grid measurement technique. The skin-friction results indicate that detailed flow fields on the surface can be obtained when numerical parameters are selected appropriately. The effect of freestream velocity on the skin-friction streamlines and skin-friction magnitude was also discussed in detail.

Gopal Sharma, The Hung Tran, Xuan Long Trinh, Jun Tanimoto
High Plateau Life-Saving and State Transition Boundary of Passenger Based on Rocket Ejection Seat

This paper centers on high-altitude rescue utilizing rocket ejection seats. It conducts a thorough examination of the technical parameters of aircrew ejection safety. It identifies the practical requirements and primary applications of high-altitude rescue technology within the realm of ejection seat survival. The paper delineates the key factors impacting passenger ejection safety at high altitudes. Furthermore, it summarizes the developmental history, technical capabilities, and specific safety prerequisites of major nations concerning critical safety parameters like the maximum allowable height for opening a rescue parachute and the maximum allowable landing speed for passengers. Additionally, the paper presents the solution strategies, technical measures, and implementation outcomes associated with first- and second-generation high-altitude ejection seat rescue technologies developed by aerospace companies. Building upon this foundation, the research paper conducts a focused analysis of crucial issues related to passenger safety in high-altitude mountainous regions. This includes topics such as local high-altitude ejection rescues and cross-regional rescues. Operating on the principle of risk management and the optimization of survival equipment performance, this paper proposes a comprehensive plan for high-altitude rescue utilizing rocket ejection seats and the transition to high plains.

Wentao Tan, Jingyu Wang
Smart Design and Optimization of a Universal and Low-Cost Double-Tailed UAV

Many kinds of UAV have been designed as universal platforms today, for the use of cargo, monitor, even bomber during the Russo-Ukrainian War, but it doesn’t mean that design of UAV is becoming so easy, especially when properties like universality, cost and capacity are taken into account meanwhile. In this paper, we developed a smart way to design a new double-tailed layout UAV named “YinRan”, which can fly in two modes (take-off and landing as multi-rotor but flying as fixed-wing) by using hybrid-power. The initial design of the configuration has been introduced firstly with a detailed analysis of aerodynamic with CFD tools, based on the results, the fuselage configuration and paddle direction were optimized to make the aerodynamic efficiency fulfil the demands. Then the Finite Element model for this UAV has been built to evaluate the strength, stiffness and vibration property. Based on the FE model, we also did some optimization works to refine the parameters and make it befit manufacture. Afterwards, the optimized design was manufactured and the total weight was 17.6 kg finally, a very critical but qualified value when compared with the design index. Finally, with ground and flying tests, we verified the performance of this UAV, and the feasibility of the smart design method.

Lilong Luo, Liang Chang, Xiaohua Nie, Likai Wang, Wenjie Guo
Design Optimization of a Honeycomb Bluff Body for Hydrogen Micromix Combustion

To achieve zero carbon and low nitrogen oxide emissions in aeroengines, this paper proposes a honeycomb bluff body with micromix scheme that is adaptable to hydrogen combustion characteristics. The combustion principles of the proposed micromix element are analyzed, and a parameter-driven micro-mixing chamber design process is established. By combining simulations using Workbench and UG, genetic algorithms and approximate models are employed to obtain the solution with the lowest NOx emissions. The numerical simulations utilize the k-ω SST turbulence model and the diffusion flame method from FGM to analyze the flow field, temperature field, and NOx emissions of both the micro-mixing single element and a 3 × 3 array. The results demonstrate that the three-dimensional wake vortex coupling of the bluff bodies in the micromix element significantly enhances the turbulence disturbance and mixing of hydrogen and air. Under the inlet conditions of 2030 kPa and 818 K, the optimum single element achieves NOx emissions below 5 ppm @ 15% O2.

Da Mo, Yuzhen Lin, Xiao Han, Yixiong Liu, Yuchen Wang
A Conceptual Sizing Method and Energy Management Strategy for Hybrid-Electric Aircraft

For the conceptual sizing of a hybrid-electric aircraft, this paper firstly initiates the discussion by sizing each system component within a given mission profile, starting from evaluating the aircraft’s maximum takeoff mass (MTOM). The calculation logic and each working path for the hybrid-electric powertrain are outlined, and the impact of energy management strategy (EMS) on the sizing method is explored and analyzed. Then, a conceptual sizing framework integrating flight performance constraints and EMS is established. Subsequently, based on this design system, a retrofitted design with hybrid-electric powertrain for a Dornier Do 228NG aircraft is performed. Also, the parameter sweeps study is conducted to further investigate the technology parameters of the battery, electric motor, and engine separately. Finally, based on the retrofitted Do 228NG, a study with six proposed EMS is performed to explore the working characteristics of powertrain and the variations in sizing parameters under different strategies.

Li Li, Junqiang Bai, Jiakuan Xu, Min Chang, Lei Qiao
Using Flight Simulator as an Effective Tool for Pilots’ Workload Assessment Certification Tests

To demonstrate compliance with China Civil Aviation Regulations (CCAR) 25.771(a), a scenario-based pilot-in-the-loop assessment test is required to verify the aircraft cockpit allows the minimum flight crew (established under CCAR 25.1523) to perform their duties without unreasonable concentration or fatigue, which means the workload of the flight crew is acceptable. In theory, measuring flight crew workload data (both subjective and objective) in real flights is a reasonable approach. However, many of the test scenarios in the certification tests for workload measurement involve abnormal and emergency scenarios, which would be difficult, risky and costly to realize in real flight. Therefore, in this paper, subjective and objective measurements of workload were obtained for 11 flight crews performing the same tasks under four identical test scenarios in simulator and real flight respectively. Independent t-tests were used to compare data of workload measurements (both subjective and objective) between simulator test and the real flight test. The results show that for workload measurement certification tests when the same crew faces the same scenario and performs the same task in simulator and real flight, there is no significant difference in values of workload measurements (both subjective and objective), and the objective value of workload measurements have similar variation characteristics. The results suggest that the simulator can be used as an effective tool for workload measurement certification tests instead of real flight tests.

Shasha Lu
Research on Dynamic Response Law of an Aeroengine Rotor Under Impact Load

To study the dynamic response law of aviation engine rotor under impact load, this paper takes a simulated power turbine rotor that well reflects the real rotor dynamic characteristics as the research object, simulates the impact load conditions when the carrier-based aircraft landing, conducts research on the vibration characteristics and dynamic response of the aviation engine rotor, and reveals the dynamic response law of rotor under large impact loads. An experimental method for conducting dynamic response research on a vibration and impact test table was proposed. A high-speed motor was used as the driving source to conduct rotor vibration characteristics tests under different impact load sizes, impact directions, and impact pulse widths at different speeds. The dynamic response of the rotor under different test conditions was obtained, and the influences of impact load size, impact direction, and impact pulse width on the dynamic response of aero-engine rotor were revealed. This paper verifies the feasibility of the experimental method, and provides technical support and reference for dynamic testing of the same type of rotor under impact load, which has important engineering application value. The results show that the dynamic response of the rotor increases with the magnitude of the impact load, the vertical dynamic response of the rotor is greater than the horizontal dynamic response at the instant of being subjected to the impact load. Besides, the dynamic response of the rotor under axial impact is greater than that under vertical impact at the same rotational speed and impact load size. Furthermore, within a certain range, the dynamic response of the rotor at the instant of impact decreases as the pulse width increases at the same rotational speed and impact load.

Weijian Nie, Xiaoguang Yang, Guang Tang, Jinshun Wang
Experimental and Numerical Study on Flow Resistance of Turbine Blade Tilted Trailing Edge Slots

Reducing the internal flow resistance of turbine blades can improve the overall efficiency of aero engines. To address the issue of the large internal flow losses in traditional horizontal exhaust slots for trailing edge cooling, structure of radially tilted trailing edge slots was proposed in previous work, and the flow resistance reduction ability of the novel scheme was investigated through numerical simulations under typical engine working conditions. Building on this, this research aimed to investigate the flow resistance of both novel and traditional schemes under ordinary pressure conditions through a combination of experimental and numerical methods. The results indicated that the tilted scheme exhibited a reduction in total pressure loss of approximately 5.7–9.1% compared to the horizontal one at the same Reynolds number. The analysis and comparison of the internal flow field details of the two schemes was conducted, which indicated that the tilted slots effectively suppressed vortex generation by reducing the coolant turning angle, resulting in lower flow losses. These research works have demonstrated the clear advantages of utilizing tilted trailing edge slots in reducing internal flow resistance, which would provide a reference for the high-performance aero engines in the future.

Xingao Kong, Dong Lv, Yingshi Liu, Lei Shi, Weilong Wu
Investigation on the Suppression of Non-synchronized Vibration of a Fan Blisk

NSV has been found in many high performance fan and compressor blades. In order to reduce the dynamic stress during NSV and find the most effective measures to prevent NSV, this paper performs both numerical simulation and experimental verification. The phase-shifted method was implemented to calculate the aerodynamic damping ratio (ADR) whereas the multi-physical field signal synchronization was employed to measure the dynamic stress and pressure. Two approaches were proposed to avoid NSV, including the VIGV angle close and blade tip cutting. Results show that the NSV occurred at the 0.7–0.75 corrected speed and two vibration modes were found to have significant vibration. The angle close in VIGV angle provides a considerable dynamic stress reduction due to the improvement of the flow condition. The blade tip cutting strategy offered nearly 59% stress reduction at 8th mode while the NSV phenomenon was eliminated at 5th mode. The findings would provide good reference for the NSV prevention and aeroelastic stability improvement in the engineering practise.

Yixiong Liu, Dingxi Wang, Xiangping Wang, Yunwu Wu, Tianzi Zhang
Steady-State Stress Prediction of Engine Components Using the State Function Method

In order to obtain the steady-state stress of the critical component for engine preliminary design, this paper performs a comprehensive investigation on the stress estimation using the proposed state function method. The basic principle is the implementation of the engine similarity criteria. To be specific, the steady-state temperature and stress fields of engine components are solely functions of height (H), Mach number (Ma), and rotational speed (N) for the specified engine. Therefore, it is possible to accurately determine the temperature and stress of the components under the desired operating condition. Four coefficients need to be calculated using the sampling points. Results show that the predicted stress of the critical part of HPT and HPC are within 5% errors compared to the finite element analysis results. The proposed method would significantly reduce computational workload and provide good reference for engine preliminary design.This method has significant practical value in engine component life prediction and management.

Wei Wang, Zhufeng Yue, Junfeng Zhang, Yixiong Liu, Yunwu Wu
An Efficient Distributed Propeller Configuration Calculation Method

Distributed electric propulsion (DEP) shows a more obvious development potential among many innovative concepts. However, it is difficult to evaluate the impact of distributed propulsion in conceptual design. In this paper, an advanced momentum source method is used to simulate the propeller. The method developed in this paper takes advantage of the fact that the momentum source method has no requirement for the computational domain itself. By loading the momentum source term into any grid in space through a UDF program, a large rectangular area is used in front of the wing as the computational domain of the propeller, avoiding repetitive and complex mesh while eliminating errors caused by grid division. The method can control all parameter changes of the propeller using a program without any modifications to the grid. The greatest benefit of the method is that it provides a convenient and efficient calculation method for the optimal design of parameters such as the number, diameter and position of propellers in distributed propeller configurations.

Chen Xue, Luo Wang, Kaiyang Zhang
Conceptual Design of an Ultra-Long-Endurance UAV Using Self-focusing Microwave Wireless Power Transmission

The limited endurance of unmanned aerial vehicles (UAVs) poses a significant challenge that hinders further development. This study presents a novel UAV design utilizing self-focusing microwave wireless power transmission technology to overcome this endurance bottleneck. Firstly, the requirements for UAV design utilizing self-focusing microwave wireless power transmission technology are analyzed, including considerations for antenna installation, electromagnetic and electrostatic protection, as well as flight trajectory planning. Subsequently, the UAV’s operational concept, overall parameters, aerodynamic layout, and electromagnetic and electrostatic protection for microwave wireless recharging are described. The operational concept involves hovering at an altitude of 10 km to safeguard high-value targets. The UAV weighs 500 kg and achieves a cruise speed of approximately 100 km/h, utilizing a 30 kW electric propeller power system. The design adopts a flying wing layout, with the rectifying antenna for the self-focusing microwave wireless power transmission system integrated into the belly of the fuselage, conforming to its shape. Finally, calculations are performed to determine the aerodynamic characteristics of the design, and the cruise performance is evaluated. The attained cruising speed and the required cruising power meet the requirements outlined in the conceptual design.

Long Zhou, Linggong Zhao, Ganglin Wang, Qian Xiang
Turbine Blade Fracture Test Method Based on Civil Aircraft Airworthiness Requirements

To study the fracture speed of power turbine blades in civil aircraft engines and its variation with the proportion of bending stress, 32 simulated blades with 4 different ratios of bending stress were designed and processed. The fracture speed of the simulated blades was calculated by finite element method. The simulated blades were grouped and fracture speed measurement experiments were conducted to obtain the actual fracture speed and fracture form of the blades. The simulated blade fracture test process was recorded by high-speed camera, and the variation law of blade fracture speed with the proportion of blade bending stress was obtained. The results show that the errors between the actual fracture speed and the calculated speed of the simulated blades are not greater than 1.10%. Within a certain range, as the percentage of bending stress decreases, the fracture speed of the blade generally shows a downward trend, and as the proportion of bending stress in the blade increases, the fracture speed of the blade decreases faster. The research provides a reference for the strength design and blade fracture test methods of real blades, which has important engineering application value.

Weijian Nie, Wangqun Deng, Wenkui Liu, Feichun Liu
Applicability Research and Improvement of Modal Method in CFD/CSD Coupling Static Aeroelastic Analysis

As same as the inertia relief method, the modal method is also widely used in the static aeroelastic analysis of the free-free system. Few studies have been conducted to analyze the impact of these two methods on the static aeroelastic results. However, in fact, when the modal method is used for the static aeroelastic analysis, the coupling between rigid-body modes and elastic modes will exist, which resulting in the rigid-body deformation included in the elastic deformation. Especially for the rigid-body pitching deformation, which will change the actual angle of attack, and thus affect the aerodynamic derivatives. In this paper, two simulation models are used to study the difference between the modal method and the inertia relief method, and the deep-seated reason of this difference is also studied, to confirm the applicability of the modal method. In addition, a rigid-body deformation corrected method is proposed for the modal method, to eliminate the effect of rigid-body deformation in the modal method, and the corrected result matches with that received by the inertia relief method quite well.

Kun Mao, Wuxing Jing, Fei Xue, Kai Chen, Yong Lu, Yingli Su, Meihong Zhang
A De-noising Method of Difference Pattern based on Combined Filtering Algorithm

If there are abnormal points in the difference pattern, the calculation results of electrical performance indicators will be affected and deviate from the true value. In order to solve the problem of large errors in the processing results of abnormal electrical performance test data, a combined filtering algorithm based on mean filtering and wavelet transform is proposed in this paper to effectively deal with isolated anomalies and speckle anomalies. First, use mean filtering to process isolated anomalies of electrical performance test data, then use wavelet transform to process speckle anomalies, and finally recover the zero depth level. Simulation results prove the effectiveness and feasibility of the combined filtering algorithm, which provides a new idea for data processing of electrical performance.

Dongwei Mao, Ping Meng, Shining Sun, Anzhen Huang
Multi-UAV Task Reallocation Based on Dynamic Window Consensus-Based Bundle Algorithm

Unmanned aerial vehicles (UAVs) have been extensively utilized in performing combat tasks due to their flexibility and low cost. The utilization of multi-UAVs can combine the strengths of each UAV, expand the search area, and enhance combat capabilities. However, the environment during task execution is not always consistent. The task allocation plan created before combat may become obsolete in the presence of unexpected changes and threats. To rapidly respond to these changes, this paper proposes a distributed dynamic window consensus-based bundle algorithm (DWCBBA) to address the task reallocation problem for multi-UAVs under sudden threats. An improved distributed task allocation framework is introduced, which allows multi-UAVs to share information and negotiate for consensus within dynamic cyclic time windows, ensuring timely handling of sudden threat events. The bidding strategy based on CBBA is optimized by factoring in the influence of threat path length to solve the model based on the effectiveness of reallocated tasks. Simulation results demonstrate that this approach facilitates the effective and rapid resolution of task reallocation under sudden threats.

Junyi Shen, Jiuli Zhou, Wenhao Bi
Optimal Fire Distribution Method of Airborne Dispenser to Airport Runway Blockade Based on NSGA-II

This paper aims to solve the optimal fire distribution problem of using airborne dispensers to block airport runways. Firstly, based on the principle of airborne dispenser attacking airport runway, the blocking probability model of single dispenser is established. On this basis, the blocking probability model of multiple dispensers is established. Secondly, the objective function with the largest blocking probability and the smallest amount of ammunition is constructed, and the optimal fire distribution model of airborne dispenser is established. Finally, the NSGA-II algorithm is used to solve the optimal fire distribution problem of the airborne dispenser, and the optimal strike aiming point is selected. The simulation results show that this method can quickly and effectively solve the optimal fire distribution problem of the airport runway blockade by the airborne dispenser. The relationship between the attack angle and the blocking probability is analyzed. Compared with the MOPSO and NSGA methods, the NSGA-II has the best optimization performance.

Jiuli Zhou, Junyi Shen, Wenhao Bi
Experimental Investigation and Aerodynamic Analysis of Supercooled Large Droplets

Until to 2014 only the Appendix C (FAA CFR Part 25) conditions were used for the certification processes in icing wind tunnel (IWT). Appendix O was introduced in 2014 to cover the supercooled large droplet (SLD) icing conditions of Freezing Drizzle and Freezing Rain, which result in a worse endangerment for flight safety. AVIC ARI FL-61 IWT has focused on the simulation of in-flight icing conditions since 2016 and increased effort was put in the simulation of SLD. The cloud parameters with different LWC and MVD characteristics were combined to achieve a SLD icing cloud with a bimodal droplet distribution. The mass distribution is achieved through modification of the existing spray system of the FL-61 IWT to allow two spray profiles to be simultaneously injected into the flow. Simulations of SLD icing environments in FL-61 IWT have been performed in which broad band mass distribution spectra are achieved that include a distinct pattern of LWC over a range of droplet sizes. Results of spray profile distributions measured in the test section have demonstrated the Freezing Drizzle conditions (FZDZ). It was shown that droplet size distributions for FZDZ MVD > 40 μm and MVD > 40 μm can be recreated droplet size distributions close to the requirements defined in Appendix O requirements, and the large droplet sizes up to 520 μm. The construction of SLD icing conditions in FL-61 IWT can be well predicted and guided through generating large and small droplet clouds with specified droplet mass distributions and combined spraying, and the main feature of SLD icing is having icing limits that extended further back on the chord of the model and the generation of relatively independent icicle. In order to determine the influence of the different droplet sizes on the aerodynamic performance, a NACA0012 airfoil was exposed to different icing clouds including Appendix C and Appendix O FZDZ. Aerodynamic of the iced NACA0012 airfoil was been analyzed by CFD. The ice accretion reduced the maximum lift and the stall angle, the drag increase was the most significant and a rapid increase. The Appendix O impact on the aerodynamics also were more severe compared to the Appendix C. The investigated FZDZ condition further reduced the maximum lift, had the most severe impact on the aerodynamics with a maximum lift reduction and the stall angle.

Fukun Zhang, Si Li, Hongyu Gu, Dongyu Zhu
Experimental Investigation on Facing Rim Cavities by Filling Treatments

An experiment on a 1/2 scaled simplified nose landing gear configuration of the LAGOON project is conducted in D5 aero-acoustic wind tunnel with the aim to explore the mechanism of the tonal noise generated by the facing rim cavities in the inner wheel. In the experiment, the geometry of facing rim cavity is changed by using poly foam to fill the inner wheel cavity. There are three configurations: conf. BS, conf. NC and conf. HC. For conf. BS, three tones are generated by facing rim cavities. Comparing with conf. HC and conf. NC, it is concluded that the generation mechanism of the first two tones is preferred to be a fluid resonant phenomenon, whereas, the third tone is more like to be governed by the coupling effect between acoustic resonant and Rossiter type.

Liang Xu, Hao Guo, Yi feng Sun
Thrust Performance Prediction of Scramjet Nozzle Based on Depth Neural Network

The depth neural network method is applied to the performance prediction of scramjet nozzle, and a network model based on the thrust coefficient corresponding to the pressure distribution unit is proposed. The convolution neural network model is established by parameterization of nozzle geometry feature extraction and pressure distribution curve, and the simulation results of computational fluid dynamics are used as training samples to predict the wall pressure distribution of scramjet nozzle. The results show that: The prediction model of nozzle performance based on neural network has good prediction accuracy, and the prediction error is less than 0.5% in training set and validation set, which is in good agreement with CFD data. The model presented in this paper is robust, and its performance will not be greatly influenced by the change of data set and initial parameters. The prediction model based on neural network takes only 1/500 of CFD, and has a great advantage in the prediction speed.

Dong Wang, Junjie Miao, Xin Jin
Research on the Method of Constructing a Meta-model for the Civil Aircraft Design Process

Civil aircraft design is a complex systems engineering practice involving multi-disciplinary coupling of aerodynamics, structure, avionics, control, etc., multiple solutions in parallel and multiple iterations. How to decouple the design process of civil aircraft, build design models from multiple perspectives and standardize the underlying description of design models has gradually become the key to promoting the further development of civil aircraft design. To address the practical problems such as the difficulty of decoupling the civil design process, the lack of theoretical support for the establishment of multi-perspective heterogeneous models, and the lack of consistency in the underlying description of design models, the method of constructing a meta-model for the civil aircraft design process is proposed. Firstly, under the guidance of MBSE methodology and relying on the authoritative source of truth centered on models and data, the civil aircraft design process driven by requirement and based on the design logic of ‘requirement-function-logic-physic’ is sorted out in detail. Secondly, based on analyzing the implementation logic and design data model of the top-level design process of civil aircraft, a perspective model of the concept definition layer, function description layer, and system implementation layer is proposed and constructed for the civil aircraft design process, which decouples the civil aircraft design process from multiple perspectives. Thirdly, the domain meta-model (DMM) is constructed at each level of the civil aircraft design by selecting and expanding the elements in the unified architecture framework (UAF) from different perspectives. Finally, the key concepts in each level of DMM are analyzed to further clarify the main lines of civil aircraft design, providing a methodological basis for the construction of metamodels oriented to the civil aircraft design process, and providing support for the establishment of heterogeneous models in multiple disciplines from different perspectives.

Qiucen Fan, Wenhao Bi, Yunong Wang, Minghao Li, An Zhang
Enhancing Flapping Wing Propulsion in Forward Flight Through Dynamic Twisting: A Numerical Investigation

To better understand the function of natural vertebrates such as hummingbirds to twist their wings, we presented a numerical investigation on the role of dynamic twisting based on a hummingbird-like flapping wing model. Computational fluid dynamic (CFD) simulations were performed to examine the effects of dynamic torsion on the unsteady flow field, generation of instantaneous aerodynamic forces, and time-averaged aerodynamic performance. This research uncovers the details of wake structures in the flow and explores the underlying mechanisms behind the positive effects of wing torsion. The results demonstrate that wing torsion can effectively maintain the favorable effective angle of attack distribution of the wing cross-section along the spanwise direction, resulting in a higher time-averaged thrust and vertical force. Further, the proper design of dynamic torsion parameters can also improve the propulsive efficiency of the flapping wing in forward flight. Dynamic torsion also showed superior ability in controlling the airflow separation over the airfoil surface and maintaining the stability of the leading-edge vortex (LEV). Under the currently specified time-varying profile of effective angle of attack variations, maintaining a constant effective angle of 9° during the downstroke and − 9° upstroke achieved the optimal propulsion performance. The findings in this paper have promising implications for both bio-inspired and robotic flapping wing applications.

Yuanbo Dong, Bifeng Song, Wenqing Yang, Dong Xue
Analysis and Design of an Impulse Pressure Test System for Aviation Hydraulic Accessories

When solenoid valves are opened or closed in the aviation system, the impact on the pipelines could far exceed the working pressure. In some cases, it could even be several times the working pressure, that is, impulse pressure. Posing a serious threat to pipelines and hydraulic components, it can reduce their reliability significantly [1]. According to the test methods and parameters as specified in the standard GJB3849-99, a pressure impulse test system is developed for the hydraulic accessories of military aviation products. In the system, proportional servo valve is taken as the element of impulse waveform control, which leads to the generation of trapezoidal wave, sine wave and water hammer wave. Also, a supercharger is applied to reach the peak pressure of 42 MPa. Developed by Lab Windows/CVI, the control system is applicable to output the given waveforms through computer closed-loop control. The actual test waveform and standard waveform are guaranteed to be highly consistent to meet different test requirements of specific test pieces. Thus, the test system can be applied in the pressure pulse test on civil or military aviation hydraulic pipelines and accessories.

Kun Li, Yufei Li, Yanyan Huai, Cheng Zhao
Aero-acoustical Optimization of a High-Lift Device Based on Hybrid RANS-LES Method

The prediction and reduction of the high-lift device noise is becoming more and more important for civil transport aircraft design. The hybrid RANS-LES method is used to simulate unsteady flow filed of a wing-flap configuration and acoustic analogy (FW-H) method is used for noise propagation. Results show that accurate characteristics of the turbulence pulsation can be captured while high computational efficiency is maintained. With this method, the optimization process is established. Flap position and deflection angle are chosen as optimized variables. Sample points randomly distributed within the given range are generated by optimal Latin hypercube design. Simulation results of sample points are based on the hybrid RANS-LES method and FW-H method. Kriging model and the radial basis function are used to construct surrogate model modules. Modified particle swarm optimization with niche count is developed as optimization searching algorithm. The optimization results are verified by the hybrid RANS-LES method and FW-H method. The correlations between aerodynamic/aeroacoustic characteristics and position and deflection parameters of the benchmark configuration are revealed. Results show that a strong linear relationship exists between the lift-to-drag ratios and flap deflection angle within the range of the optimized variables given. Another trend that the overall sound pressure level of the far field is positively correlated with the flap deflection angle is also emerged. Comparing with the benchmark configuration, the overall sound pressure level of optimized configurations are respectively 2.03 dB and 1.51 dB lower than that of the benchmark configuration (71.99 dB) while the lift-to-drag ratios of the two optimized points increase − 0.4% and 4.3%. Noise reduction and aerodynamic performance of the optimized configuration show that the developed low-noise optimization process is effective.

Zhen Wang, Lu Xie, Yiju Deng
Aero-engine Simulation Model Performance Tracking Method Based on Online Transfer Learning

Accurate simulation models of aero-engines are crucial for assessing engine status. The presence of engine performance dispersion within the fleet, along with varying degrees of degradation in individual engines during actual usage, can introduce deviations in the simulation model. These deviations may subsequently result in an increase in error between actual data and simulation parameters, leading to potential misdiagnosis. Furthermore, the limited availability of outfield engine data poses challenges in generating highly precise personalized simulation models. This paper proposes an online transfer learning method to address the issue of adaptive component performance. Firstly, a depth-domain adaptive method based on reducing geometric distance in hidden space is adopted, and a pre-trained model fitted with large amounts of historical data is migrated to obtain a personalized model reflecting the state of an individual engine using small samples of outfield flight data. Secondly, semi-supervised learning is introduced into online updating of the model, enabling real-time tracking of actual engine states as new flight data constantly arrive and ensuring that the model adapts to changes in engine states. The method effectively leverages engine operation data collected over an extended period of time in various states, thereby addressing the challenge of limited flight data availability in the field. By updating the data and model in both offline and online phases, a novel performance tracking model is developed for the target engine. Furthermore, empirical evidence validates the efficacy of our proposed algorithm in mitigating model performance prediction errors, demonstrating a significant improvement in accuracy compared with the generalized model.

Jintao Hu, Min Chen, Hailong Tang, Jiyuan Zhang
Design Optimization of Aeroengine Titanium Matrix Composite Bling

SiC fiber reinforced bling structure utilizes the advantages of SiC fibers, such as high specific strength, high specific stiffness, high temperature resistance, fatigue resistance, and creep resistance, to enhance the load-carrying capacity and reduce the weight of the rotor disc. In this study, the design optimization of a fiber-reinforced bling for a specific engine compressor stage was conducted, taking into account considerations of strength, economy, and manufacturability. The macroscopic elastic parameters of the composite material were predicted using a micromechanical finite element method. A parameterized model and multi-objective parameter optimization method were employed for the bling design. The optimized bling meets the strength assessment criteria and achieves a weight reduction of 20.38% compared to the blisk structure. The findings highlight the importance of implementing composite bling and provides good reference for engineering practise.

Tianzi Zhang, Yixiong Liu, Jia Li, Xiangping Wang, Jie Guo, Yunwu Wu
Continuous Modeling in Aircraft Mission Analysis and Simulation

Mission analysis is the initial process in aircraft development. Its goal is to understand how the aircraft will operate and interact with other systems to accomplish its mission. As a system of systems (SoS) level development process, mission analysis involves various multi-disciplinary and cross-domain models, such as battlefield plotting models, scenario visualization models, SoS architecture models, and multi-agent wargaming models. This results in a heavy modeling workload and presents a significant challenge in maintaining model consistency. To ensure model transferability and consistency, this paper introduces a continuous modeling method for aircraft mission analysis. With the help of a modeling language-independent ontology, it achieves preliminarily model transformation and data transfer between the four kinds of models used in aircraft mission analysis. According to the practice, the continuous method helps improve the continuity and consistency of models and reduce the workload of building and maintaining models.

Yuchen Zhang, Jing Zang
A UAV Visual SLAM System for Post-disaster Emergency Mapping

Post-disaster emergency surveying and mapping information is a key information resource to assist post-disaster rescue and reconstruction. In recent years, visual simultaneous localization and mapping (SLAM) technology has been expanding its application scenarios by virtue of its advantages of simple structure and good mapping effect. In this paper, an unmanned aerial vehicle (UAV) visual SLAM system for post-disaster emergency mapping is presented. Firstly, this paper analyzes the current situation of UAV mapping technology and visual SLAM technology. Subsequently, the hardware architecture and algorithm of the system are introduced. In terms of algorithm, the system first completes the construction of sparse feature point map based on ORB-SLAM2 algorithm, and then improves the algorithm through map reconstruction technology to realize the construction of dense point cloud map. After completing the system design, the whole system is applied to the real scene for experimental verification. Experimental results show that the designed system can realize the construction of a complete global graph of the real scene, and give the mapping task real-time, safe and efficient advantages.

Zhaoxi Wong, Mengqi Zhang, Wenhao Bi
Numerical Investigation of Active Flow Control of Blade Synthetic Jet on Performance and Stability of Transonic Axial Compressor Rotor

To investigate the influence of blade synthetic jet on the aerodynamic performance and stability of a transonic axial flow compressor, NASA Rotor35 was selected as the object of numerical simulation in this paper. The results show that the stability margin of the compressor is slightly reduced by the suction surface excitation at four different positions, but there is an optimal position that can improve the compressor's total pressure ratio and efficiency. At this position, the total pressure ratio of the compressor at the peak efficiency point hardly changes, with an efficiency increase of 0.58%. At the design point, the total pressure ratio and efficiency increased by 0.18% and 0.55% respectively, and the near-stall condition point is increased by 0.33% and 0.16% respectively. The reason for the analysis is that the stall of the compressor is mainly caused by blockage in the blade tip. Although synthetic jet can effectively blow and suck the migration vortex, reducing the separation loss of the suction surface, because the excitation position is only on the suction surface, the blockage of the compressor is more than that of the prototype, resulting in a slightly decreased stability margin of the compressor. Then, to balance the stability margin, the coupled flow control is carried out by combining the processing of the axial inclined slot casing treatment with the synthetic jet on the suction surface of rotor blade. The results show that after coupled flow control, the flow margin of the compressor increased by 8.76%, the total pressure ratio increased by 1.76%, and the efficiency decreased by only 0.13%. The shock wave loss, outlet loss and casing treatment loss are reduced compared to the flow control with simple casing treatment, which is the main reason for the improvement of compressor performance.

Guang Wang, Wenhao Liu, Wuli Chu
Study of Unsteady Ventilation for Aircraft Cabins

Creating a safe and comfortable air environment for aircraft cabins is important for flight passengers inside. Currently steady ventilation is commonly used in environmental control systems of the commercial aircraft cabins, but the constant air-supply parameters often bring complaints about the unsatisfactory thermal comfort and air quality in cabins. To improve the air environments in aircraft cabins, this study explored unsteady ventilation for cabins by CFD. Three strategies for unsteady ventilation with different air-supply velocities were applied to a cabin model. The air velocities, air temperatures and mean ages of air near passengers were monitored and compared, in order to validate the proposed strategies for unsteady ventilation in aircraft cabins. The results showed that compared with the conventional steady ventilation as well as the unsteady ventilation with square and sinusoidal air-supply velocities, the unsteady ventilation that simulated the natural wind could produce varied and soft airflows without draft, although the mean age of air and air temperature near passengers were not significantly improved. Optimization of the air-supply velocities and temperatures for the simulated natural wind to both improve the thermal comfort and air quality in cabins requires further exploration.

Yun Wei, Tengfei Zhang
Study on Influence of Inner Root Shape of Slat on the Aerodynamic Performance of High-Lift System

For typical large civil transport aircrafts, the improvement of aerodynamic characteristics of high lift devices can significantly improve the overall performance of the aircraft. Geometry details including a slat horn, a nacelle, slat tracks and flap track fairings do have large impacts on the aerodynamic behavior of high lift devices. This paper addresses an investigation on the influence of a geometry detail, the root shape of inner slat. The Computational Fluid Dynamics (CFD) simulations are performed with solving three-dimensional incompressible Reynolds-averaged Navier-Stokes (RANS) equations, and the turbulence is simulated with the k-omega shear stress transport (SST) turbulence model. According to the comparisons of four configurations of different inner root shapes of slat, good consistency can be found at low angles of attack but great difference at high angles of attack for lift coefficients, and different configurations did not differ a lot from each other for drag coefficients. Comparing to configuration 1 and configuration 2, configuration 3 and configuration 4 lead to a larger separation region on upper surface of the wing and thus resulting in the reduction of lift coefficient. In configuration 1 and configuration 2, the vortex caused by the inner root face of the slat have a development path of staying close to upper surface of the wing, resulting in limited separation region. Contrarily in configuration 3 and configuration 4, the vortex caused by the inner root face of the slat develop much higher and spread towards the fuselage and outer side of the wing, which ends up leading to bigger separation region. At the very leading edge of the wing, the relative locations of the inner root face of the slat and onglet of the wing play an extremely important role in affecting the development of flow. The results and analysis will provide a guidance reference in aerodynamic design of inner root shape of slat.

Mengying Chen, Longqian Zheng, Qimin Wang, Meihong Zhang
Modeling and Analysis of Forest Fire Extinguishing for Special Aircraft

As forest fires become increasingly frequent, there is a growing need for effective firefighting capabilities. Specialized aircraft have emerged as a promising solution, but executing forest firefighting missions with these aircraft entails managing numerous uncertain variables, such as adverse weather conditions, equipment failures, unpredictable water delivery, and unfamiliar flight paths. Given the challenges associated with executing specialized aircraft forest firefighting missions, including unclear processes, uncertain system requirements, and complex command work, this study adopts a multi-perspective approach based on the Department of Defense Architecture Framework (DoDAF) to propose a standardized methodology for modeling and analyzing the specialized aircraft forest firefighting system. This methodology entails the development of task execution capability requirement models, activity models, system interface models, and other related models, all aimed at optimizing the specialized aircraft forest firefighting mission procedures. Ultimately, this modeling approach aims to provide firefighting personnel with a more specific and intuitive visual conceptual model of the task at hand, allowing them to efficiently leverage specialized aircraft to suppress forest fires and minimize associated damages. The findings of this research endeavor are expected to assist decision-makers in effectively planning specialized aircraft forest firefighting missions, verifying the feasibility of task implementation, and projecting the time, manpower, and resources required to complete firefighting tasks from preparation to completion.

Mengqin Dong, Wenqing Yang, Xiwen Zhang, Wei Huang
Developing Aircraft Departure Queueing Models for a Mixed Takeoff/Landing Operational Runway

Proper management of aircraft departure queues so that the aircrafts wait at the gate rather than before the runway entry point is important for reducing fuel consumption at airports. This study proposes a method to apply an aircraft departure model on a runway with time-varying fluid queues to a mixed takeoff/landing runway. As a case study, this study applied this departure queueing model to the daily operation of runway 34R at Tokyo International Airport and estimated departure waiting times using actual departure traffic data. The results revealed that aircrafts were waiting before the runway entry point for approximately one hour per day. This is due to the inability to accurately predict the waiting time in front of the runway or to appropriately allocate waiting time at the gate according to the predicted waiting time, which results in the waste of approximately 1 ton of fuel. It was also shown that the validity of the model can be improved by changing the service time according to the number of arriving aircrafts per unit time. Furthermore, information that departure management system should obtain from the arrival management system for their future integration was discussed.

Daiki Iwata, Eri Itoh
Self-propulsive Performance of Tandem Flapping-Fixed Airfoils at Low Reynolds Number: A Case Study

Tandem airfoils or hydrofoils have been extensively observed in both natural flyers or swimmers and aircraft. Dragonflies can achieve excellent flights by adjusting the phase difference and wake interaction of their tandem flapping wings. A similar phenomenon also exists between individual fishes in a school formation. Specifically, the flapping-fixed configuration of tandem airfoils with a narrow inter-foil gap was revisited by us recently, and it was proved that the lift performance of this configuration can be improved by the strong fluid-mediated interaction at an expected propulsion performance. As a follow-up, the self-propulsive performance of this configuration is further examined using numerical simulations, and the analysis is focused on three typical cases, i.e., a high-thrust (HT) case, a high-lift (HL) case, and an enhanced high-lift (EHL) case by tilting the flapping plane. The Lattice Boltzmann method is employed to conduct the simulations and the code has been well-validated in our previous work. Results show that, compared to the fixed Strouhal number condition, the self-propulsive solution of tandem flapping-fixed airfoils can release their thrust margin and lead to a higher cycle-averaged forward speed. The forward speed also fluctuates corresponding to the dynamic thrust generation within a flapping cycle. This release of extra thrust can boost the forward speed of the HT case up to almost 1.5 times and the conventional triple vortex streets in the wake are compressed in the lateral direction to form a highly staggered wake pattern. For the HL and EHL cases, the increase in forward speed is not significant and thus the lift enhancement is marginal. The wake topology is mostly retained at the self-propelled equilibrium while the downstream convection of vortices is at a higher speed. Moreover, the lift efficiency of both HL and EHL cases can be enlarged by 10–15% at the self-propelled equilibrium. The impact of the density ratio between the airfoils and the fluid is also investigated and the aerodynamic performance is barely changed until the density ratio decreases to 10, below which an increase of cycle-averaged forward speed and lift generation is observed for both HL and EHL cases. This research presents a more practical solution for the tandem flapping-fixed airfoils within a low Reynolds number regime since micro air vehicles of this compound layout should cruise at the self-propelled equilibrium. Despite that, a further consideration of the MAV body and other components can include extra drag, these conditions can also be easily investigated using the current solution.

Gang Li, Long Chen, Yanlai Zhang, Jianghao Wu
Research on Tensile Strength and Fatigue Properties of GLARE Laminate

Glass fiber reinforced aluminum alloy laminate (GLARE) is hybrid structural materials consisting of aluminum alloy and glass fiber reinforced composites. Due to its excellent structural strength and fatigue performance, it has become the ideal choice for main load-bearing structures and fatigue-critical components in the aerospace industry. However, the presence of holes in the Glare laminates, which are often used for fastener connections and assembly, greatly reduces the structural strength due to stress concentration at the hole locations. In this study, the tensile performance and fatigue life of perforated GLARE laminate was tested using experimental methods. Additionally, the ABAQUS software was used to establish a layer-board damage failure model to analyze the injury evolution. The results show that compared to aluminum alloy specimens under the same testing conditions, GLARE laminate has a lower elastic modulus. However, after the yield point, the tangent modulus of GLARE laminate is significantly higher than that of aluminum alloy. The advantage of the fiber layer in the reinforcement direction becomes increasingly apparent with increasing strain. The fatigue fracture of GLARE laminate includes metal fracture, fiber pullout and delamination. As the ply angle changes from 0° to 45°, the yield strength and tangent modulus of the laminates gradually decrease, and the fatigue life is significantly shortened. Additionally, based on the progressive failure analysis method, the stress distribution at the hole edge of the perforated GLARE laminates and the damage evolution process of the laminates were obtained.

Weitian Zhang, Hulin Wang, Dingfeng Ma, Changliang Lin, Shaobo Gong, Chunlan Zhao
Research on Distributed Intelligent Node

The aero-engine distributed control system can overcome the problems of high complexity, long development cycle, poor maintainability, difficult iterative verification, low computing power, and excessive weight and volume of the centralized control system. It will become an important trend in the future engine control methods. The sensor intelligent node is a key node of the distributed control system, which can effectively improve the quality of signal processing, reduce the computing burden of the FADEC system, improve the maturity and maintainability of the system, and shorten the development cycle of the FADEC system. This paper proposes a general architecture of sensor intelligent nodes, based on switch matrix and SoC processor, which can adapt to different types and quantities of engine monitoring sensors. This architecture can complete the parallel high-speed acquisition and processing of multi-channel sensor signals. It can be connected to the distributed control system as a distributed bus node, and it can realize the fault diagnosis of signal conditioning and acquisition based on the surround BIT, and support the intelligent algorithm of sensor fault diagnosis. Based on multiple linear regression, neural network intelligent algorithm and embedded temperature sensor, the sensor intelligent node can perform temperature compensation and calibration for sensor signal acquisition. It can improve signal acquisition accuracy and anti-interference ability greatly, and provide a strong guarantee for the performance improvement of the control system.

Ming Yu, Wei Niu, Jianping Zhao
Operation Optimization for Cooling System of Large Aircraft

The cooling system of the large aircraft often adopts air cycle refrigeration system that uses the air as the refrigerant and supply fresh air at the same time. This paper proposed the operation optimization method for the cooling system of large aircraft to ensure the working performance of the system, which could guarantee the system operation reliability and reduce the aircraft performance compensatory loss. The dynamic simulation system was established to analyze the dynamic performance of the aircraft cooling system at first. Then its control method and system operation were optimized carefully. The system level optimization was conducted with the logic and parameter matching for the flow control valve, the ram air regulation valve and the temperature control valve. In addition, the flow control system was also optimized by steplessly regulating the engine bleed air and providing the reasonable control logic. The proposed optimization method could reduce the engine compensation loss on the premise of meeting the demand of aircraft refrigeration system.

Huicai Ma, Xiaomin Dang, Yiling Liu, Rongjun Li
Optimized Power System Layout Focusing on UERF on eVTOL Aircraft

The power system is critical for electric vertical take-off and landing (eVTOL) aircraft not only in providing propulsion but also flight control, especially during the VTOL phase. System safety assessment is necessary for the development of aircraft and its systems to ensure safe operation and compliance with certification. However, existing methods are not sufficient for more sophisticated systems and there is a lack of efficient approach for particular risk analysis (PRA) on eVTOL aircraft. This paper proposes a complete model-based safety assessment (MBSA) method, which can quantitatively evaluate the risk of uncontained engine rotor failure (UERF). The proposed method is established on the logical architecture model of the eVTOL power system, and it provides automatic generation of minimum cut sets (MCSs). Further combining the above results with the UERF model and relative battery management systems (BMSs) layout, the final probability of loss of control caused by UERF is calculated. By comparing the different probabilities of various layouts, the optimized power system layout is found.

Haoran Zheng, Ruichen He, Shuguang Zhang, Florian Holzapfel
The Preparation and Properties Study of the Microwave Absorbing Honeycomb Based Dielectric Loss Aramid Paper

In this paper, we added the carbon fiber into the aramid pulp and then prepared the dielectric loss aramid paper, which was used to prepare honeycomb-core materials. We also prepared different specifications microwave absorbing honeycomb with dielectric loss aramid paper as raw material, and investigated the relationship between honeycomb nonsteady compressive strength, horizontal shear strength, longitudinal shear strength and phenolic resin increment. The microwave absorbing property was also characterized. The results showed that, the addition of carbon fiber as absorber into the normal aramid paper could bring good microwave absorbing property for the honeycomb, and also less impact on mechanical properties. The microwave absorbing honeycomb based dielectric loss aramid paper had good nonsteady compressive strength and shear strength, especially the shear modulus. Importantly, the microwave absorbing honeycomb based dielectric loss aramid paper exhibits excellent microwave absorbing ability, and it will be a new type of application prospect in aerospace field.

Zhen Jia, Lichun Chen, Maowei Yang, Tao Su, Junxia Tian, Lixin Xuan
Experimental Researches on Electric Thermal Anti-Icing Performance and Runback Icing

Runback icing may occur on a thermal anti-icing system when the system is not fully evaporated. Most researches focused on aerodynamic characteristics at simulated runback ice shape, and icing wind tunnel test was very limited, the runback icing process, surface temperature variation, power consumption were not fully understood. Electric thermal anti-icing performance and runback icing were researched in FL-61 icing wind tunnel, and mean volume diameter was 20μm, liquid water content was 0.5–2 g/m3. An electric thermal heater was equipped on a NACA 0012 airfoil with length of 304.8 mm to simulate a thermal anti-icing system, which consists of airfoil, heat insulation, electric heater and surface, and the electric heater was controlled to maintain surface temperature a preset value. Tests were performed in dry air and simulated icing conditions, keeping the temperature, angle of attack, and mean volume diameter the same, but varying the free stream velocity and surface temperature leads to differences in the runback icing process. Videography of the runback process was captured, temperature and power consumption were measured during anti-icing process. Water running back and icing process was researched. Water film formed on the leading edge heated area, and became rivulets when running back. Rivulets turned into ice where surface temperature was lower than freezing, and ridge ice grew dramatically. A “clean zone” without water and ice was observed slightly before ice ridge, which was believed to be caused by the forward step separation induced by ridge. This clean zone phenomenon was analyzed by examining test photos and videos, partial rivulets ran spanwise instead of chordwise downstream before ridge, so the rivulets cannot reach ice ridge continuously, and less water collected by high ridge than the initial ridge. The “clean zone” was a coupled result of water film running, unsteady aerodynamics and ice ridge growth, careful close-up researches were suggested. Thermal anti-icing process was researched. Surface temperature and power consumption variation with time was analyzed, there were a rapid decrease of temperature and a sharp increase in power consumption when spray initiated during anti-icing test. Although leading edge surface was heated up to 36.7 ℃, the system performed as a running wet thermal anti-icing system, and a full evaporated anti-icing system would consume more power and need higher surface temperature. Runback ice can be affected by anti-icing power and icing conditions, a large extent of runback icing from 6% to more than 40% chord length was observed.

Dongyu Zhu, Pei Runan, Qian Zhansen, Yuan Li
GPU-Accelerated Flow Simulations on Unstructured Grids Using a Multi-colored Gauss-Seidel Method

Efficient and robust implicit solvers are often required for large-scale applications in Computational Fluid Dynamics (CFD). In this paper, we present the development and implementation of a Multi-Colored Gauss-Seidel (MCGS) method for solving flow equations within an unstructured finite volume framework on the Graphics Processing Unit (GPU). A coloring algorithm is introduced such that no two adjacent elements are painted the same color, and the colors are distributed evenly as much as possible. A reordering of elements is implemented to group elements with the same color. A Jacobian freezing technique is applied to further reduce the computational cost. The capability of the developed framework is demonstrated through transonic flow simulations of the NASA Common Research Model (CRM) Wing-Body configuration on unstructured grids.

Liu Yang, Jian Yang
Coupling Evaluation Model of Abnormal Flight Recovery Strategy

Abnormal flight operations leading to a low on-time performance rate have become a significant bottleneck in the development of civil aviation transportation. Therefore, effective management of these irregular flights is essential. Taking into account the practical experience of flight dispatchers within the airline's operations control center, it is crucial to thoroughly evaluate the effectiveness of the recovery strategy for abnormal flights and ensure that the decision-making process is highly executable. First, assess the primary factors affecting the abnormal flight recovery process. Based on this assessment, establish an evaluation system for abnormal flight recovery strategies. To mitigate uncertainty in handling evaluation indicators during the assessment, we introduce matter-element extension analysis and set pair analysis methods to construct an evaluation model. Finally, in the real-world abnormal flight management process, we have chosen to analyze abnormal flight cases involving A321 civil aviation aircraft. The findings demonstrate that the evaluation model presented in this article adeptly manages indicator uncertainties, delivering a scientifically sound and effective evaluation tool for the operation control center.

Yu-jie Wan, Guo-qing Wang, Miao Wang
Study on the Cause of Air Traffic Delay in Fukuoka Approach Control Area Using CARATS Open Data

Fukuoka Airport is one of the local airports in Japan but has been the busiest airport using a single runway in Japan. After the COVID-19 pandemic, congestion is predicted to increase again, and some solutions are required to mitigate the congestion not only for time and energy but also for environmental reasons. Approach air traffic controllers often use the method “radar vector” to make proper separations among air traffic. The extra distance flown by the airliners due to the radar vector tends to become longer as the number of traffic increases. The construction of an additional parallel runway is planned as one of the solutions, however, the simultaneous approach and departure using two runways will not be permitted under the current regulation because the lateral distance between the two runways is not large enough. Therefore, it is still important to make proper separations among traffic in the approach control area as in a single runway operation. In this paper, the situations of the air traffic in the Fukuoka approach control area from 2012 to 2020 are analyzed first, and the causes of the congestion are analyzed using multiple regression methods.

Yasutaka Kawamoto, Yota Iwatsuki, Shin-Ichiro Higashino
A Hybrid Time Synchronization Optimization Scheme for Onboard Payloads with Independent Clock

Crystal oscillators are typically selected as payload clocks, and onboard periodic time synchronization is necessary to ensure long-term stability. Time synchronization method varies for payloads with different time precision requirements, which are categorized into high precision time requirement (HPTR) and general precision time requirement (GPTR) payloads. As presented in the case of China Seismo-Electromagnetic Satellite (CSES), HPTR payloads typically employ pulse per second (PPS) signals for synchronization, whereas GPTR payloads employ onboard time broadcasts via CAN bus. Time inconsistency is unavoidable due to the differences in time synchronization methods and payload timing systems. The sources of delay in timestamp transmission are analyzed in detail, and a hybrid synchronization optimization scheme is proposed to measure the delays with two separate models. The first model is designed to minimize the internal delay of payload time synchronization system, which includes a finite state machine(FSM) and a hardware input trigger signal. The second model is designed to measure timestamp transmission delay for calculation during post-processing, by connecting to both second pulse signal and CAN bus. Performed on one of the CSES payload prototype, experiment results indicate that the optimized time difference is expected to be less than 1 ms. This hybrid optimization scheme effectively improves time consistency without additional PPS resource, which is practical and low-cost.

Yu Chen, Ying Wang
Aerodynamic Characteristics of Mars Lander Configuration

There are three main tools for hypersonic flight vehicle design, namely flight testing, CFD and ground-based testing. The flight testing cost and risk high. For reducing this risk, lots of work should been done with the CFD and ground-based testing. The impulse wind tunnel is one kind of ground-based facility. It can simulate hypervelocity flow but the test time can only last for several milliseconds. Force measurement in impulse wind tunnel is more difficult than that in continuous wind tunnel. When the impulse tunnel runs, the output of the balance includes the aerodynamic force and the inertia vibration. The vibration caused by the mass of model, balance and sting (MBS) system. Usually the frequency of the MBS is same order of magnitude with the test time, so if we want to get the pure aerodynamic force, we need to improve the frequency of the MBS. The higher the frequency is, the more test curve period we get within test time, the higher the accuracy is. For improving the frequency of the MBS, it is necessary to make the balance and the sting more rigidity, and reduce the weight of the model. For the kind of blunt body model, such as Mars lander configuration, the frontal area is several times larger than common model, so the axial force is very large during the test, even far more than the range we usually measured. Aiming at this issue, considering the Mars lander configuration is symmetrical, the mx component for improving the frequency of the MBS is removed. A five-component balance has been designed by the method of finite element simulation, considering both natural frequency and sensitivity requirements. It shows that the calibrated precision meets the military standard indicators, the accuracy of each component is within 5‰. Using the balance to measure the force of the Mars lander configuration model in FD-20a shock tunnel of China Academy of Aerospace Aerodynamics, the Mach number is 6. The model chosen to test is a 70-deg-semiangle cone of 261mm axial length, and the model material is made of LC4. The test gas are air and carbon dioxide respectively. The test results show that the repetition is well. The axial force coefficient with carbon dioxide is higher than with air, but the increment decreases when the angle of attack α changes from 0° to − 20°.The degree of trim angle decreases with the carbon dioxide test gas. Compares to the CFD, the axial force coefficient is recovered to within 3‰ and 1% in the air and carbon dioxide test gas respectively.

Huilun Wang, Junmou Shen, Dapeng Yao, Feng Ji, Xing Chen, Qi Li
Parameters Sensitivity Study on Dynamic Characteristics of Turbofan Engine Mounting System

The hinged multi-link system is often used as the mounting system of aircraft turbofan engines. It is mainly composed by multiple ball joints and links. As an important connecting structure, the dynamic performance of the mounting system directly affects the vibration transmission from engine to the cabin. In order to reduce the transmission of vibration and noise to the cabin, it is necessary to conduct parameters sensitivity study on vibration transmissibility of the mounting system, and further guide the parameter design for the mounting system. In this article, a hinged multi-link mounting system which used in a turbofan engine was selected as the research object. Then the multi-body dynamics method was used to model the mounting system, and the Hertz contact model and the Coulomb model were used to model the ball joints. Seven parameters including the ball joints parameters and the angle of the links were selected as variable factors. The influence of variable factors on the system vibration transmissibility within the engine operating frequency range was studied. The results show that, the stiffness of the main ball joint and the after ball joints have linear effect on the vibration transmissibility, and the other parameters have nonlinear effect on the vibration transmissibility. In addition, the second-order effect of the side links angle and the first-order effect of the main ball joint stiffness are the main influencing factors, so they can be used as the main design parameters. The center link angle and the after ball joints stiffness are the secondary influencing factors, which can be used as the secondary design parameters. The other parameters of the ball joints are low sensitivity factors, which can be ignored in the design. The innovation points lie in: (1) The main sensitive parameters for the vibration transmissibility of the turbofan engine mounting system were proposed in this study. (2) The nonlinear impact and friction of the ball joints in the mounting system were considered. (3) By using the self power spectrum algorithm, the total vibration transmission characteristics of the mounting system over a wide frequency range was obtained. It is beneficial for improving system robustness. The research results of this article can provide guidance for the parameters design of the turbofan engine mounting system.

Chunlan Chen, Qun Yan, Yonghui Chen, Jianqiang Wang, Jian xu
Stability and Control Characteristics Analysis and Flight Quality Assessment of One Stealth Blended Wing Body Aircraft

The development of aviation technology focuses on the continuous emergence of the new layout of the form of aircraft. Each new layout creates leap in aircraft performance, even great changes in flight quality. Compared to a conventional long range civil transport support aircraft, the stability and control characteristics of one stealth blended wing body aircraft designed with V-shaped tail and strake are significantly different in the aspects of longitudinal stability, transverse heading stability, aileron control effect, rudder control effect. In this paper firstly the general layout design features and aerodynamics properties of one stealth blended wing body aircraft designed with V-shaped tail and strake are introduced and analyzed. In order to guarantee the safety of real flight test and the following optimized flight control system design, taking the scaled flight demonstrator LingQue-B of one stealth blended wing body aircraft designed with V-shaped tail and strake as research object, longitudinal stability and transverse heading stability and control characteristics are analyzed based on the small perturbation theory of aircraft flight dynamics. According to China national military flight quality standards of manned fixed-wing aircraft, the flight quality assessment of scaled flight demonstrator LingQue-B for one stealth blended wing body aircraft designed with V-shaped tail and strake is conducted and analyzed. The flight quality assessment consists of flight mode analysis of longitudinal short period mode and Phugoid mode as well as transverse heading flight mode, which include transverse heading mode and Dutch rolling mode and spiral mode. It can be concluded from the stability and control characteristics analysis results that the longitudinal static stability varies with the angle of attack variations greatly, and the transverse heading static stability is comparable to that of one civil transport aircraft designed with a conventional layout. Through flight quality assessment, the analysis results illustrate that at the left border of flight envelope the longitudinal short period mode becomes unstable, which is consistent with the rapid pitch oscillation phenomena that occurred during virtual flight test of the scaled flight demonstrator LingQue-B in wind tunnel. And at the right border of flight envelope the Dutch rolling mode appears and presents level 2 flight quality. Against the longitudinal short period mode unstable problems during virtual flight test, longitudinal stability augmentation control design as stability improvement measure based on flight quality assessment and analysis is proposed and validated by software simulation. The innovation of this paper lies in the research method combination of virtual flight experiments in wind tunnel and aircraft flight dynamics modelling to analyze stability and control characteristics and assess flight quality of one stealth blended wing body aircraft before the real flight test. Therefore, it not only avoids the risks and unknown factors caused by the real flight test, which is developed for stability and control characteristics analysis and flight quality assessment as well as optimized control system design validation, but also saves a lot of considerable economic costs.

Qing Li
Numerical Investigation of the Effect of Aircraft Nose Wall Waviness on the Hole Pressure of the Static Pressure Probe

The existence of the aircraft nose skin waviness will affect the static pressure measurement, and then affect the altitude indication of aircraft. So it is of great significance to study the effect of waviness on the flow field around the probe. In this paper, the k-ω SST model is used to carry out numerical simulation research on the influence of the aircraft nose skin waviness on the hole pressure of the total static pressure probe. The results show that the numerical simulation method can meet the requirements of the numerical simulation of the flow field around the total static pressure probe on the nose surface. For the single aircraft nose configuration, the influence of skin waviness on the pressure in the spatial area near the pre-installation position of the probe increases with the increase of Mach number, while the influence of angle of attack can be ignored. For the nose-probe combination configuration, the influence of skin waviness on the pressure coefficient at the measuring hole of the probe increases with the increase of Mach number. The influence of skin waviness on the first group of pressure holes S1 is greater than that on the second group of pressure holes S2. At the same time, it is found that the presence of the total static pressure probe does not change the influence of waviness on pressure coefficient obviously.

Dong-Yun Zhang, Zhen-Wei Wang, Xiang Wu, Biao Wang, He-Yong Xu
Design and Simulation of Discrete Gust Load for T-Tail Aircraft Considering Control Law

In this article, a batch simulation platform for gust loads based on terms and scenario requirements was established, by which the gust loads of a T-tail aircraft under different conditions and inputs were analyzed and compared. The research showed that there were certain differences in the calculation results of gust loads with and without considering control laws, which were related to the logic of the transfer function. On the other hand, there were certain rules in the calculation results under different input parameters of gust loads. By early variable parameter analysis, we could fully consider various calculation scenarios and working conditions as well as improve the calculation and evaluation efficiency between different rounds.

Xiaochen Liu, Zhongwu Yan
Low Speed Wind Tunnel Test Method and Structural Function Verification of Variable Camber Wing Leading Edge Full Scale Prototype

In order to verify the structural function of the civil aircraft variable camber wing leading edge full-scale prototype under real wind load, the test method was studied by using the large-scale low-speed wind tunnel FL-10. Combined with the structural characteristics of the prototype, two-side support style with elliptical end plates was selected. Based on the principle of two-dimensional optical deformation measurement, an optical measurement system capable of accurately measuring the leading edge surface deformation was built. The structural function verification of the full-scale prototype was completed from two aspects of deformation and maintenance. The results show that: for the prototype with a length of 4.3 m and a width of 2.7 m, the leading edge load equivalent to the actual take-off and landing flight state can be obtained. The chordwise proportion of the leading edge that can be measured is 93%, and the displacement measurement accuracy is 0.10 mm, which can meet the structure functional verification requirements. Through the wind tunnel test, it is verified that the variable camber leading edge can accurately achieve the target shape deformation under wind load. The relative deformation of the maximum deflection shape is less than 0.5%, and the spanwise relative deformation deviation is less than 1%. The relative deformation of the intermediate deflection shape do not exceed 3%. The relative deformation of the maximum deflection shape caused by the angle of attack is less than 2%, and that caused by the wind speed is less than 0.2%.

Chunpeng Li, Zhansen Qian, Ronghuan Zhao, Jin Zhou, Zhigang Wang, Jingfeng Xue, Yu Yang
Aerodynamic Investigation of a New Layout for eVTOL Aircraft

As an important component of urban air mobility (UAM) aircraft, electric vertical take-off and landing (eVTOL) aircraft come in a variety of configurations, including Multirotor, Lift + Cruise, and Tiltrotor. However, most of these configurations use open rotors, which have certain limitations in terms of safety and noise levels. To address this issue, this paper proposes a novel aerodynamic layout for eVTOL aircraft that combines tiltable ducted fans with lift fans embedded in the wing. Numerical simulation methods are used to investigate the aerodynamic characteristics of this configuration, including the effects of step structures at the forward end of the lift fan and the effects of additional covers on the top and bottom of the lift fan on the overall lift-to-drag ratio. The research results show that the best performance is obtained when the ducts are provided with covers, but this increases the complexity of the system. To increase the reliability of the system, adding step structures to the forward end of the lift fan on the underside of the wing can cause changes in the flow field of the duct at the lift fan, improving the overall lift-to-drag ratio of the wing. This produces similar results to enclosing the duct, especially at low angles of attack.

Guotao Chen, Jun Chow, Xiaotao Qiao
A Stiffener Layout Design Method for Vibration Reduction in a Wide Frequency Band

Stiffened plates and shells are widely used in aerospace, marine, automotive, and other industries due to their high strength to weight ratio and ability to prevent buckling. In addition to these properties, stiffeners are also of great importance for vibration control. Natural frequencies can be tuned by the design of stiffeners to meet the requirements of dynamic integrity. Geometries, sizes, and layouts of stiffeners play a significant role in determining the natural frequencies of stiffened structures, among which the layout design of stiffeners has been identified as the most challenging task. In this paper, a stiffener layout design method is proposed to achieve vibration reduction in a wide frequency band. The principle of the method is to assign natural frequencies by adding stiffeners progressively according to the energy distribution of mode shapes. As a result, neighboring natural frequencies are manipulated in the opposite direction, whereupon a frequency band is opened for vibration suppression. The method is investigated in a squared plate. The gap between natural frequencies is increased during the process of iteration validating the proposed design method. The gap width of the designed stiffened plate can be enlarged by 410%.

Anlue Li, Yu Fan, Yaguang Wu, Lin Li
Analysis of the Influence of Structural Parameters on the Aeroelastic Stability of Rotor Blades

A comprehensive numerical model of a rotor blade is developed, which incorporates a coupled analysis of the blade's aerodynamic and structural behavior. The model is utilized to investigate the effects of various parameters, including blade stiffness and balance mass, on the aeroelastic stability of the blade. To validate the model, experimental data from previous studies are employed.The results of the numerical simulations demonstrate that the aeroelastic stability of the rotor blade is significantly influenced by its structural and aerodynamic properties. The study reveals that blade stiffness is the most critical parameter affecting the aeroelastic stability, followed by balance mass. Furthermore, the study highlights the substantial impact of the interaction between these parameters on the blade's stability.The innovation of this study lies in the development of a comprehensive numerical model that enables the investigation of how structural parameters influence the aeroelastic stability of rotor blades. The findings provide valuable insights for optimizing rotor blade design and enhancing rotorcraft performance. Moreover, the study emphasizes the importance of considering structural parameters in rotor blade design. It holds practical significance for researchers and engineers involved in rotor blade analysis and design. Future work could focus on exploring the influence of additional parameters, such as blade tip speed and blade twist, on the aeroelastic stability of rotor blades.

Shuangman Xia, Yong Wang, Changliang Lin, Gang Wang
Vibration Analysis of Laminated Composite Plates with Delamination Damage

Delamination damage is a prevalent form of damage observed in laminated composite plates, and its presence can significantly impact the vibration characteristics of the plate. This paper presents a numerical model based on the finite element method for analyzing the vibration behavior of laminated composite plates with delamination damage. A cohesive zone model is employed to simulate the delamination damage, assuming its distribution across the plate's thickness. The model enables the determination of natural frequencies and mode shapes of the plate. The study investigates the effects of delamination size and location on the vibration characteristics of the plate. The numerical results demonstrate that the presence of delamination can indeed influence the plate's vibration behavior. Specifically, as the size and location of the delamination increase, the natural frequencies of the plate decrease. Additionally, the mode shapes of the plate exhibit significant changes due to the delamination, resulting in large displacements within the delaminated regions. Notably, the study reveals that the mode shapes of the plate are more sensitive to changes in the location of the delamination rather than its size.Overall, the proposed numerical model serves as a valuable tool for analyzing laminated composite plates with delamination damage. It facilitates the prediction of vibration characteristics under various delamination scenarios and supports the design and optimization of laminated composite structures to enhance vibration performance.

Shuangman Xia, Zhirui Wang, Changliang Lin, Haibin Xu
Research on L-Band Interference Detection Based on UAV Aerial Monitoring System

GPS interference incidents of domestic civil aircraft have occurred frequently in recent years, seriously threatening flight safety. Accurate and efficient detection of GPS interference sources and elimination of harmful interference are essential to maintaining airwave order, protecting the rights and interests of civil aviation frequencies, and preventing unnecessary losses. The main frequency of the GPS navigation service is in the L-band, and this paper is based on the work requirements for searching for L-band interference. To fully understand the applicability of different types of monitoring tools, this paper starts with the scenario above and examines two types of surveillance means, namely the aerial monitoring platform and ground handheld devices. It completes the signal strength, directivity, monitoring environment and monitoring means through monitoring and direction finding of two signal sources. The role and advantages of different types of devices in the target scenario are examined, and the precautions and usage considerations are analyzed to provide suggestions and references for practical work.

Fu Chang, Ma Jun, Xu Yunshan, Zhu Dongdong, Sun Zongyan
A Rapid Evaluation Method for the Aero-Propulsion Coupling Characteristics of a Distributed Electric Propulsion Aircraft

Distributed Electric Propulsion (DEP) aircraft typically refer to aircraft equipped with multiple electric propulsion units, providing more design flexibility and development potential in aviation. In order to investigate the aero-propulsion coupling characteristics of the wing section, we established a DEP aircraft with a twin-fuselage and tandem wing configuration, which is equipped with a total of 24 “high-lift” Electric Ducted Fans (EDFs) distributed along the wing’s trailing edge. This paper proposes a rapid evaluation method, aiming to analyze the aero-propulsion coupling characteristics of the DEP aircraft. The results using our proposed method are compared with wind tunnel experimental data to validate its accuracy. The results show that the EDFs can generate a significant lift increment and reduce drag, consistent with the potential benefits of low-speed Boundary Layer Ingestion (BLI). The rapid evaluation method can accurately predict lift compared to experimental data but shows some deficiencies in predicting drag accurately. Finally, based on the established rapid evaluation method, an aerodynamic analysis is performed on the DEP aircraft equipped with 24 electric ducted fans. Using the rapid evaluation method, the whole DEP aircraft analysis is conducted on a computer with 12-core CPUs and 64 GB of RAM, with each state's solution time taking approximately half an hour. Compared to the time required for aerodynamic analysis using Reynolds-Averaged Navier-Stokes (RANS) methods, the computation time is significantly reduced, making it highly suitable for early-stage aircraft design requiring iterative solutions.

Haoliang Yu, Tao Lei, Ran Li, Xingyu Zhang, Xiaobin Zhang
Design and Research of Aero-Engine State Monitoring System

For aero-engine vibration monitoring, a rotor balancing method based on least squared approximation is established, an aero-engine condition monitoring system is developed, system architecture, software and hardware design are carried out, and its correctness, effectiveness and reliability are verified in the real engine bench test. The results show that the designed vibration signal and high tooth signal conditioning method, the correlation algorithm to obtain the vibration fundamental frequency amplitude and phase, and the dynamic balance vibration information screening method and the dynamic balance least square approximation algorithm are adopted, which can ensure the accuracy and stability of dynamic balance calculation, and have certain engineering application prospects.

Wen Yan, Wei Niu, Jianping Zhao
Deep Learning Based Fast Prediction and Optimization of Aerodynamic Performance for a Propeller with Gurney Flap

High-altitude and long-endurance unmanned air vehicles have placed high demands for the performance of propellers under low Reynolds numbers. Conventional propeller design methods are less efficient, making it difficult to achieve a breakthrough in propulsion efficiency. This paper explores the possibility of extending the Gurney flap on low Reynolds number propellers to achieve efficiency breakthrough. A framework based on deep learning is established to fast predict and optimize the aerodynamic performance of a propeller with Gurney flap, which can quickly obtain the optimal propeller profile airfoil shape, distribution of twist angle, and chord length at different advance ratios. The results show that the surrogate model based on Multi-Task Learning has high prediction precision and efficiency, which can obtain performance parameters within 0.06 s. At different advance ratios, the optimized propellers with Gurney flap have a significant improvement in propulsive efficiency. In particular, the optimal propeller with Gurney flap consumes 35.65% less power in cruise at the advance ratio of 0.9, resulting in a propulsion efficiency of 80.74%, an improvement of 11.14% compared to the pre-optimization period. In conclusion, Gurney flaps are important components to enhance propulsion performance for propellers, and propellers with Gurney flaps have better aerodynamic efficiency than propellers without those. This work provides a reference for accurate and efficient design of low Reynolds numbers propellers.

Liu Liu, Zeming Gao, Tianqi Wang, Jun Li, Lifang Zeng, Xueming Shao
Equivalent Beam Modeling Method for Geometric Nonlinear Static Aeroelastic Analysis

Unit load method is a commonly used way to simplify complex high-aspect-ratio wing models to beam models, which can greatly reduce the time cost of linear/nonlinear aeroelastic analysis. An improved scheme of applying loads and extracting structural stiffness in unit load method is proposed in this paper. Unit loads and fixed-end boundary condition are applied on the ends of whole wing rather than the ends of each segment of wing, then stiffness characteristics are calculated using the relative displacements and equivalent loads of two equivalent beam nodes of each wing segment. By this scheme, the number of static analyses can be decreased, and the influence of cross-section warping can be minimized. Furthermore, polynomial fitting can be used to correct the results of both ends with the results of segments far away from ends. Linear and nonlinear static aeroelastic analysis are carried out for validation. The small relative error between the results obtained by the equivalent model and the original model indicates that this method can meet the requirements of linear and nonlinear static aeroelastic analysis.

Zhiying Chen, Yang Meng, Zhiqiang Wan, Chao Yang
Performance Analysis and Optimization of Three Spool Aero Derivative Gas Turbine Fueled with Liquid Hydrogen

The aim of this paper is the performance investigation of the influence on the overall performance of three spool aero derivative gas turbine on the basis of liquid hydrogen fuel. Firstly, a mathematical model of a three spool aero derivative gas turbine was established and translated into computer language to conduct the performance simulation. Besides, an innovative physical parameter model based on hydrogen combustion was proposed during the research process and the simulation results were verified by reliable data. This study focus on the performance changing principle of the three spool gas turbine after fueled with liquid hydrogen and makes a comparison with the results obtained from engines using conventional fuels. Considering the deep cooing and high heat sink properties of liquid hydrogen, three performance optimization schemes for the three spool gas turbine were introduced and deeply analyzed the changes in engine performance parameters after optimization. At last, the investigation conducted on the optimized schemes based on cold energy of liquid hydrogen has demonstrated that performance of the three spool gas turbine can be improved apparently. Among the optimized cycles, the two-stage cooling cycle benefits most in power output while the improved scheme of cooling exhaust gas to recover water and injecting it back in to the combustion chamber can not only improve engine performance but also reduce the emission of nitrogen oxide. However, both schemes require certain modifications to the gas turbine which will affect the reliability and economy of the engine. To sum up, the scheme of combining inlet air cooling with fuel reheating is more feasible and can achieve considerable performance benefits. The research methods and conclusions mentioned in this paper are also applicable to aero gas turbines. In the future, it is necessary to make a profound research in areas such as hydrogen fuel regulation systems and hydrogen combustion stability and so on.

Shaohua Song, Ke Zhang, Jialu Yin
Influence of Model Scale on Wave Landing Characteristics of Seaplane

Using the numerical simulation method and based on the volume of fluid method and dynamic overlapping grid technology, the dynamic characteristics of the model scale and real scale seaplane landing on the wave surface are simulated. Through the analysis of the periodic operation response of seaplane landing on the water surface with waves of different scales, the laws of gravity center sinking, floating and pitching are compared. The results show that the characteristics of wave landing motion on the water surface with reduced scale and real scale are obviously different. The rear body touching the water and the front body touching the water of the reduced scale model constitute the restoring moment, which makes the motion of the aircraft show obvious periodicity. In the real aircraft model, Aerodynamic moment obviously participates in the process of aircraft pitching motion, which destroys the periodic behavior of rear body touching water and front body touching water, resulting in aperiodic pitching motion; The sinking and floating motion of the aircraft is involved by the pitching motion. They have the same motion law, but the sinking and floating motion lags slightly. The 1/10 scale model has the same conclusion as the real aircraft.

Qing Wen, Zhihang Cheng, Kangzhi Yang, Xing Liu
Wind Tunnel Model Static Aeroelastic Deformation Correction Method Based on Grid Reconstruction

High aspect ratio swept wings are commonly designed in the modern commercial airliners to meet the requirements of long range and high speed. The wind tunnel test of an aircraft model in high-speed configuration has been conducted. The Reynolds number has been kept the same at the same Mach number while changing the dynamic pressure. Wind tunnel test results show that the deflection of the wingtip can reach 5% of the semi-wingspan, and the wingtip twist angle can reach − 3° at cruising Mach number. A wind-tunnel aircraft model static aeroelastic deformation correction method coupling Reynold-Averaged Navier-Stokes computation and grid reconstruction technology has been set up. The analysis results of the integral longitudinal coefficients validated against the wind tunnel experimental data indicate that the method presented can identify the differences in aerodynamic characteristics caused by deformation and dynamic pressure correctly. Pressure distributions including shock wave position and intensity vary with the free inflow dynamic pressure. The proposed correction method, which has been successfully applied to the aircraft engineering design, is regarded as a useful way to meet the design requirements.

Chen Kai, Cheng Pan, Mao Kun, Chen Ying, Wu Dawei
Noise Analysis of Insect-Scale Flapping Wing with Fluid Structure Interaction

In recent years, researchers have made significant progress in achieving high lift and large thrust in bio-inspired flapping-wing aircraft. However, there has been relatively less attention paid to the aerodynamic noise generated by flapping wings. Whether in military or civilian bio-inspired design, it is particularly important to design an efficient aircraft with the capability of quiet flight. This paper focuses on a bio-inspired flexible flapping wing as a research model and introduces acoustic-solid interaction modal and aerodynamic noise analysis methods to investigate it. Flexible wings with different material properties and flapping frequencies are calculated. In addition to analyzing the spatial distribution of noise, the instantaneous sound pressure curve is Fourier transformed, and different methods are used to analyze low-order and high-order harmonics of the flow-solid coupling calculation results. Finally, the equal loudness curve is introduced to consider the response of human ears to the noise. Using numerical simulations, we explore the positive effects of air vibration (sound) on the aerodynamic performance of flapping wings, investigate the influence of the wing's shape parameters, motion parameters, and flexible wing parameters on the sound field, and seek the inherent connection between the aerodynamic performance of flapping wings and air vibration, revealing the mechanism of aerodynamic noise generated by flapping wings. This study aims to answer questions such as how to improve the aerodynamic performance of flapping wings by utilizing air vibration through wing flexibility and how to achieve quiet flight through effective flapping motion, and hopes to provide some reference for the aerodynamic and quiet design of flapping-wing flight.

Yueyang Guo, Wenqing Yang, Yuanbo Dong, Jinzhi Luo
Overall Design of a Submarine Launched Unmanned Aerial Vehicle

Based on the analysis of UAV mission scenarios and operational requirements, this paper designs a pure electric multi-function, long endurance submarine launched UAV, and carries out a series of design, analysis and calculation. Determine the launch form, application scenario, size constraint, design index and aerodynamic layout of the UAV, and then design the wing, fuselage, power layout and tail fin of the UAV according to the overall design goal, and determine the preliminary design scheme of the UAV. Using CATIA software to draw the overall surface model; The calculation method is explained. The flow grid is drawn by CFD and the boundary conditions are set. Fluent was used for aerodynamic analysis, and a set of data of lift, drag and pitch moment coefficients were obtained according to different angles of attack. The static stability of the whole air-craft was analyzed, and the overall aerodynamic design and analysis of the submarine-launched UAV was completed. The re-sults showed that the aerodynamic characteristics of the UAV were good and the design index requirements were met. The pa-rameter table and electronic prototype of the whole machine are given.

Furong Li, Zhanke Li, Haiyang Han
Comprehensive Optimization Technology for Composite Flexible Skin Structures with Zero Poisson's Ratio Honeycomb

Aiming at a composite flexible skin composed of zero Poisson's ratio honeycomb and elastic skin, a comprehensive optimization method was proposed. Firstly, the geometric parameters of flexible skin were taken as variables, and a parametric modeling method of flexible skin was designed; Secondly, an approximate model of the relationship between geometric parameters and mechanical properties of flexible skin was constructed based on the response surface method, and the accuracy of the approximate model was evaluated quantitatively; Finally, considering the in-plane strain, out-of-plane deflection, mass and other factors, a comprehensive optimization mathematical model is established by the weighting coefficient method, with the geometric parameters of the flexible skin as the optimization variables. Meanwhile the optimal configuration of the flexible skin structure was obtained by the genetic algorithm. This article constructs a finite element model of composite flexible skin and verifies the comprehensive optimization method. The results indicate that compared with the initial configuration, the optimized configuration has an in plane deformation capacity increase of 14.70%, an out of plane bearing capacity increase of 32.65%, and a structural mass reduction of 28.03%. This proves that the comprehensive optimization method proposed in this article has important guiding significance for the design of composite flexible skin.

Yuchao Guo, Sen Ai, Chen Song, Xiaohua Nie, Liang Chang, Chaofeng Zhang
Unsteady Aerodynamic Prediction Using Limited Samples Based on Transfer Learning

In this study, a method for predicting unsteady aerodynamic forces under different initial conditions using a limited number of samples based on transfer learning is proposed, aiming to avoid the need for large-scale high-fidelity aerodynamic simulations. First, a large number of training samples are acquired through high-fidelity simulation under the initial condition for the baseline, followed by the establishment of a pre-trained network as the source model using a long short-term memory (LSTM) network. When unsteady aerodynamic forces are predicted under the new initial conditions, a limited number of training samples are collected by high-fidelity simulations. Then, the parameters of the source model are transferred to the new prediction model, which is further fine-tuned and trained with limited samples. The new prediction model can be used to predict the unsteady aerodynamic forces of the entire process under the new initial conditions. The proposed method is validated by predicting the aerodynamic forces of free flight of a high-spinning projectile with a large extension of initial angular velocity and pitch angle. The results indicate that the proposed method can predict unsteady aerodynamic forces under different initial conditions using 1/3 of the sample size of the source model. Compared with direct modeling using the LSTM networks, the proposed method shows improved accuracy and efficiency.

Wen Ji, Xueyuan Sun, Chunna Li, Xuyi Jia, Gang Wang, Chunlin Gong
Sealing Performance Analysis of Flareless Tube Connection Under 35 MPa Pressure

In view of the current aircraft hydraulic system pressure grade of is developing to 35 MPa. Aming at the unclear sealing performance of many tube connection forms in the current hydraulic system of high-pressure system, the flareless tube connections with nominal diameters of 6 and 8 mm were selected for research. According to the theoretical analysis of metal-to-metal sealing, the simulation calculation using finite element software, and the prototype test according to the sealing test standard of aircraft hydraulic pipeline connectors, the results show that the sealing performance of the flareless tube connection form is reliable under the 35 MPa pressure system, which meets the leak-free performance requirements required by engineering applications. It should be noted that according to the recommended torque of aviation standards, when the minimum preload torque is applied, the nominal diameter of 6 mm flareless tube connection is reliable to seal, while the nominal diameter of 8 mm flareless tube connection is not reliable enough to seal. For the nominal diameter of 6 mm flareless tube connection, when the minimum equivalent axial force is 4410 N, the median equivalent axial force is 7410 N and the maximum equivalent axial force is 9870 N, the simulation calculation of the sealing length is 0.3 mm, 0.7 mm and 1.05 mm, respectively, which are greater than the theoretical (minimum) sealing length of 0.14 mm. For the flareless tube connection with a nominal diameter of 8mm, when the minimum equivalent axial force of 4710 N is applied, the simulation calculation seal length is 0.1 mm, which is less than the theoretical (minimum) sealing length of 0.14 mm, that is, the seal is unreliable; when the median equivalent axial force of 7600 N and the maximum equivalent axial force of 10,500 N are applied, the simulation calculation of the sealing length is 0.6 mm and 0.5 mm, respectively. Both are greater than the theoretical (minimum) seal length of 0.14 mm; it is worth noting that the sleeve and fitting have been damaged to varying degrees when the maximum equivalent axial force is applied. In the actual use process, it is recommended to use the median moment in the recommended torque of aviation standards to ensure that the sealing performance of the flareless tube connection is good while the structure is not damaged.

Lei Gao, Tao Chen, Zhenghong Li, Xiyu Wang, Siyang Zhao
Sealing Performance Analysis of Memory Alloy Based Flareless Tube Connections Under 35 MPa Pressure

In view of the fact that increasing the pressure grade can improve the response performance of the hydraulic system, reduce the volume of each component, reduce the weight, etc., the current hydraulic system pressure grade of military and civilian aircraft is developing to 35 MPa. Aiming at the current unclear sealing performance of many tube connection forms in the hydraulic system of the current high-pressure system, the flareless tube connections with nominal diameters of 6mm and 8mm were selected for research, and the joints and sleeves were replaced with memory alloys from stainless steel. According to the theoretical analysis of metal-metal sealing, the simulation calculation using finite element software, and the sample test according to the sealing test standard of aircraft hydraulic pipeline connectors, the joint and pipe sleeve made of memory alloy are plastically deformed under the action of preload, the contact area and sealing length are much greater than the required theoretical minimum sealing length, and the sealing performance of the flareless tube connection form is reliable under the 35 MPa pressure system, which meets the requirements of leak-free performance required by engineering applications. It should be noted that the preload required for memory alloy-based flareless tube connections is significantly less than the aviation standard recommendation, which could cause structural failure. For memory alloy-based flareless tube connections with a nominal diameter of 6mm, the recommended preload is 3000–4500 N; For memory alloy-based flareless tube connections with a nominal diameter of 8 mm, the recommended preload is 3000–5000 N. For stainless steel pipe connections with nominal diameters of 6 and 8 mm, the recommended value of preload is about 7000–9000 N according to aviation standards.

Tao Chen, Chen Chen, Yunxiu Yang, Zhiming Cai, Deqi Wang
Unsteady Aerodynamic Shape Optimization of a Vertical Axis Wind Turbine Under the Framework of DAFoam

Floating vertical axis wind turbine has become a hot topic in recent years for the potential enormous in offshore wind power generation. Aerodynamic shape optimization of blades is a relatively effective solution for increasing the efficiency of wind energy utilization of vertical axis wind turbines. In the present paper, a triple-blade H-type VAWT with a NACA0021 airfoil section is selected as the initial research object. An adjoint-based tool called DAFoam is applied for aerodynamic shape optimization of VAWT. This approach is coupled with unsteady RANS equation and discrete adjoint method. The overset mesh technology solves the unsteady rotational motion of the wind turbine blades. 2D airfoil parameterization can be achieved through the FFD method, whilst an update mesh is created by the mesh deformation approach. At the rated tip speed ratio (λ = 2.5) of VAWT, the time average wind energy utilization coefficient of the blades within a rotating cycle is set as a criterion for evaluating the aerodynamic performance of VAWT. The optimization results show that the wind energy utilization coefficient of the optimized VAWT blade increases more than 7.6% (from original 0.223 to final 0.24). In comparison to its original configuration, the airfoil's leading-edge region is evidently thicker after several optimization iterations. This article innovatively integrates the adjoint optimization method in aircraft aerodynamic design into VAWT blade efficiency improvement. On the one hand, it avoids repeated flow field calculation caused by multiple design variables. On the other hand, high-precision unsteady numerical calculations ensure optimization effectiveness.

Feng Chen, Xiaoming Cheng, Kai Zhang, Ying Chen, Xinyu Zhang
Ignition and Combustion Characteristics of Atomized Al–Mg Alloy Particles with Different Compositions

The utilization of Al–Mg alloy, which combines the advantages of aluminum and magnesium, shows promise in solid propellant applications. This study investigates the slow oxidation, ignition, and combustion characteristics of atomized Al–Mg alloy particles with various compositions. The thermogravimetry (TG)/differential thermal analysis (DTA) and a single-particle ignition experimental system are employed for analysis. Simultaneous measurements of particle size (D), ignition delay time (ti), and combustion time (tc) are captured using a two-camera system. Results demonstrate that the slow oxidation of alloy powders in an oxygen environment can be classified into three stages. The initial oxidation occurs at approximately 826 K, where both magnesium and part of aluminum are oxidized (Stage II). The remaining oxidation takes place at around 1100 K (Stage III). The concentration of magnesium in the alloy particle within the range of 10–20 at.% does not significantly affect the ignition delay time under all experimental conditions. However, alloy particles with a low magnesium content of 10 at.% exhibit relatively short combustion times at high-temperature experimental conditions. A higher effective oxidizer mole fraction in the oxidizing environment leads to a longer ignition delay time but a shorter combustion time. Furthermore, combustion time decreases with an increase in ambient temperature in most experimental conditions. The average combustion temperatures, determined using the two-color thermometry method, are 2204.7 K for Al50Mg50 particles, 2225.6 K for Al60Mg40 particles, and 2733.6 K for Al90Mg10 particles.

Yunchao Feng, Likun Ma, Yandong Liu, Zhixun Xia
An Optimal Trim Configuration Optimization Framework for Highly Flexible Aircraft

In this paper, a set of flight configuration optimization framework for high-altitude long-endurance aircraft is formed by optimizing the level flight configuration. The intrinsic beam model is used to model the formula of the whole highly flexible aircraft, coupled with unsteady aerodynamics and six-degree-of-freedom rigid body motion. The interior point method is used for optimization calculation by balancing the initial points first and optimizing the sequence of multiple initial points later. The optimal calculation results of the aircraft with wing layout studied in the literature are given and compared with the trim configuration in the literature. The results show that the proposed optimization framework can converge quickly in relatively few steps, and can significantly improve the whole plane resistance during the trim process of flexible aircraft.

Jiachen Wang, Zhou Zhou
Thermal Load Sensitivity Analysis and Mass Reduction Design of Heat Pipe Turbine Disk

Turbine disk is an important life-limited component of aero-engine and bears the high centrifugal load and extreme thermal load, which brings huge challenges to thermal protection. The heat pipe turbine disk (HPD) is a conceptual design with the potential to meet the strength and structural requirements. In this study, the effective thermal conductivity is firstly calculated by the heat pipe CFD simulation and then obtain the precise temperature and stress distribution of the HPD. To verify the performance of HPD, selecting the Chebyshev number to measure the thermal load sensitivity and comprehensively analyzing the maximum temperature at the disk rim, the maximum stress at the disk hub, and the notch stress at the heat pipe groove. The results indicate that the HPD could reduce the maximum temperature, temperature gradient, and maximum equivalent stress compared to the traditional turbine disk. At the heat flux of 450 kW/m2, embedding heat pipes reduces the maximum equivalent stress at the disk hub for 77.2 MPa, the rim equivalent stress for 422.95 MPa, and the maximum temperature is decreased for 163 K. Furthermore, the HPD could achieve structural lightweight by internal slotting and reducing the thickness of the disk hub. Within the safe usage limit of the material, the mass reduction of the turbine disk can reach 6.46%. The HPD effectively improves the performance of the turbine disk without using new materials or modifying the disk cavity configuration. It is beneficial for achieving the equal strength design of the turbine disk, improving the safety of the future aero-engine.

Yuchen Zhang, Guo Li, Guohua Zhang, Shuiting Ding
Preliminary Study on Wind Tunnel Test of Amphibious Aircraft Dropping Water

High speed, large water load, and drawing water repeatedly and quickly from the source of water are the advantages of firefighting using amphibious aircrafts, the effect of firefighting largely depends on the coverage level of the water dropped on the ground. Different firefighting aircrafts have different design characteristics that make the situations of water reaching the ground from different aircrafts obviously different. Through wind tunnel test, based on the design parameters of AG600 aircraft, the falling characteristics of water dropped from amphibious aircraft with different speed, height, and quantity were studied, and the distribution characteristics of dropped water on the ground were measured by ground water collecting devices. The results show that the higher speed and height of dropping water, the more obvious the aerodynamic influence on the dropping water is, the more significant the atomization is, and the less water mass fell on the ground.

Kangzhi Yang, Qing Wen, Zhihang Cheng, Zhongren Jia
Generation of Optimized Trajectories for Congestion Mitigation in Fukuoka Approach Control Area Using Deep Reinforcement Learning

Fukuoka airport is the busiest single runway airport in Japan and the congestion has been increasing year by year. The COVID-19 pandemic has temporarily eased the congestion, but it is expected to increase again after the pandemic. Excessive radar vector by air traffic controllers to maintain aircraft separation during congestion causes economic and environmental losses due to increased flight distances and times. We attempted to generate optimal trajectories in the approach control area of Fukuoka airport using a deep reinforcement learning method based on a centralized Deep Q Network (DQN). Wind information was considered in the trajectory optimization using Mesoscale Model (MSM) data from the Japan Meteorological Agency. As a result, the optimized trajectory was found to be useful because a radar vector reduction of 23.7% in distance and 33.6% in flight time were attained compared with the recorded radar data provided as CARATS open data. The trajectories have the characteristics that all of the Ground speed (GS) of aircraft are made slower while directed straight to the intermediate fix (IF) after entering the approach control area.

Yota Iwatsuki, Yasutaka Kawamoto, Shin-Ichiro Higashino
A Spanwise Loss Model of Turbine Cascade with Tip Clearance Based on Machine Learning

The tip clearance leakage flow of turbine cascade significantly affects the spanwise distribution of circumferential averaged total pressure loss at its outlet. Therefore, this paper aims to build a spanwise loss model, using a combination of machine learning methods, to effectively improve the simulation accuracy of through-flow calculation of S2 stream surface. Based on the blade profile of the first stage of an aeroengine at 90% span, using variables such as tip clearance height and camber angle, the flow field is calculated by numerical simulation, a database is constructed, including nearly 150 samples. Feature engineering is applied to select 8 variables such as prediction of AMDC model of tip clearance leakage loss, and 3 intermediate variables such as pressure loss coefficient of tip leakage flow and secondary flow. Then the random forest algorithm is used to screen to input variables in prediction models. And BP neural network is used as estimator, with genetic algorithm optimizing its initial weight and threshold. Finally, a spanwise loss distribution model with 10 estimators and a selector is constructed. The results show that the model has good regression and prediction ability for spanwise loss distribution curve, with R2 greater than 0.98 and MAPE less than 2.5%. Thanks to the completeness of parameter coverage in the database, the combination of machine learning methods, and knowledge related to tip leakage flow, the model in this paper has good generalization ability. It can provide effective technical support for the development of turbine through-flow design and simulation analysis methods.

Yucheng Chen, Donghai Jin, Xingmin Gui
A Multidisciplinary Model-Based Engine Rotor Integrity Assessment Approach Derived from System Safety Requirements

Rotor integrity is one of the most critical factors of aero-engine safety. It involves multiple strongly coupling disciplines, including engine overall thermodynamics, secondary air system flow distribution, rotor cavity flow pattern, heat transfer, and stress analysis. However, published research barely discusses the inter-relationships between these disciplines, which may be unsatisfactory for advanced aero-engines to evaluate the rotor’s overspeed and burst margin. To address this problem, this paper proposes a tightly coupled rotor integrity assessment approach based on a multidisciplinary aero-engine model. Firstly, this paper analyzes the safety objective and development trend of the airworthiness requirement to clarify the modeling demands. The risk-based criterion is suggested to rotor integrity assessment to take engine system safety requirements into account. Besides, this paper establishes a model-based rotor integrity assessment approach by detailed analyzing the inter-relationships between the related disciplines. Combing with the multidisciplinary model, this paper also introduces uncertainty quantification and safety analysis approaches to rotor integrity assessment to evaluate the engine-level impacts. Further, the proposed model-based assessment approach is applied to a turbine rotor loss of load assessment case. The result confirms the necessity to consider the multidisciplinary impacts during rotor integrity assessment, and validates the approach’s ability in calculating safety-critical parameters during the failure-induced transient state. The model-based approach provides an effective method of compliance in addition to conventional costly tests, which may be beneficial for ensuring advanced engine safety and airworthiness certification.

Qing-lin Ma, Shui-ting Ding, Tian Qiu, Lei Qi, Chen-yu Gan, Sheng-yu Bao
Experimental Investigation of Model Deformation on a High Aspect Ratio Aircraft at Transonic Speeds in ETW

In wind tunnel testing, especially under high aerodynamic loads, model deformation is a very important parameter which can have huge impact on the aerodynamic results. Thus it is essential to consider model deformations in wind tunnel tests. In this paper, Wing deformations of a high aspect ratio aircraft semi-span model were measured by the Stereo Pattern Tracking (SPT) system in the European Transonic Windtunnel (ETW). The principle of the system is to simultaneously track a total of 40 markers attached on the wing lower surface of the model from two directions by calibrated cameras that were mounted in the inner test section sidewall. Based on wind-off reference measurements over the entire incidence range of the model, the system can identify the displacement between loaded and unloaded conditions, which then can be finally transformed into wing bending and twist information. For the illumination of the SPT markers LED lights were installed at several positions in the test section. The estimated measurements accuracy is better than 0.1mm for wing bending and 0.1deg for wing twist. Aeroelastic bending and twist on the wing were measured for different test configurations. These data are reported that wing bending and twist deformations are raising rapidly as the lift increases when pitching the model up. Wing deformations also change significantly by the dynamic pressure variation, while they have little change with the increase of pure Reynolds number under constant dynamic pressure. The effects on model aerodynamic coefficient of tested configuration from wing bending and twist deformations are also discussed.

Yulong Ba, Ying Chen, Yang Liu, Lingfeng Zhang
Quantifying the Effects of COVID-19 on US Carriers Engaged in International Aviation from 2020–2022

The outbreak of the COVID-19 pandemic in late 2019 saw governments around the world introduce stringent disease containment measures such as the closure of national borders quickly followed by a substantial reduction in international travel. This had an immediate catastrophic effect on international aviation. This paper establishes trends in key passenger and cargo metrics for US carriers engaged in international aviation from 2011–2022, using primary operational data sourced from the US Bureau of Transportation Statistics. The downturn that resulted from the spread of COVID-19 during 2020, 2021, and 2022 is assessed here by comparing the actual reported data against extrapolated forecast data representative of the normal growth and performance that would otherwise have occurred in the absence of COVID-19. The extrapolation process used an Exponential Smoothing technique that was freely available within the MS Excel Data Forecast toolbar. The sum of the monthly differences between the reported data and the extrapolated data allows the impact of COVID-19 to be fully quantified. Overall, this research has determined from key metrics that in round figures US-centric international travel suffered a loss of 145 million passengers and 490 billion Revenue Passenger Miles as a result of travel restrictions and public safety concerns during the pandemic period of interest. In addition, the total US-centric international air cargo tonnage decreased by 410,000 short tons and the loss in Revenue Ton Miles amounted to 2,531 million short ton miles. These figures provide a salutary benchmark against which future risk mitigation and emergency planning strategies can be assessed.

Nicholas Bardell, Ziqian Zhang, Yutong Yao, Xinyue Fan, Hengli Zhao
Investigation on the Folding Method and Inflation Process of Ram Air Parachute

As a high-performance paraglider, the ram air parachute has been widely used in various fields such as aerial delivery, space recovery and life-saving. The inflation process is very important to the ram air parachute. A successful parachute inflation basically means that the mission has been almost success. The issues of the folding method, and the numerical modeling and fluid-structure interaction (FSI) during the inflation process of the ram air parachute have been explored in this paper. By using the fluid-solid interaction(FSI) method on ram air parachute, the dynamic change of shape, ess-strain, inflation load and lift/drag coefficient are all worked out. The structure model utilized the membrane finite element structure, while the numerical simulation method employed the Arbitrary Lagrange-Euler (ALE) method. Additionally, we conducted research on numerical modeling for ram air parachute folding, employing the backwards folding technique. This research not only enhances our understanding of the working mechanism of the parachute but also contributes to the advancement of ram air parachute theory. It can serve as a reference for future studies on new methods for the ram air parachute inflation process.

Jinhong Li, Liu Qi, Zhang Hui, Yuling Duan, Gang Yu
Nonlinear Aeroelastic Analysis Framework for the Large-Deformation Wing Considering Distributed Propellers’ Effects

A nonlinear aeroelastic analysis framework is presented, verified and employed to investigate the distributed propellers’ influence on the static aeroelastic response of a high-aspect-ratio wing under large deformation. In the framework, CR beam elements are applied for the large-deformation wing structure, and an efficient cylinder coordinate generation method is proposed for attached propellers at different position. Skewed vortex cylinder theory and non-planar vortex lattices are applied to capture the aerodynamic interference of propellers on the flexible wing. Meanwhile, the induced velocity distribution and static aeroelastic displacement are validated and show good agreement with reference results. For the numerical cases explored, results indicate that thrust can cause structural negative torsion, while slipstream brings the lift gain. Under the same total thrust, the lift increases with the decrease of propeller size. It is also found that compared with rigid configurations, the deformation will reduce the lift increment from propellers. The analysis methods established in this paper can provide further guidance for the coupling design of such aircrafts.

Xuan Wu, Zhou Zhou, Zhengping Wang
Numerical Simulation Analysis and Efficiency Evaluation for Skin Friction Reduction by Boundary Layer Injection

In this study, the effect of boundary layer injection for different gas on wall skin friction reduction was numerically investigated. To quantization analysis of the effect of boundary layer injection on engine performance, an evaluation way has been provided and used for the study. The sst k-ω model was employed as the turbulence model and laminar finite-rate model was chosen as the combustion model. This numerical method was firstly validated by experiment results in open domain. The numerical results showed that with increasing flight Mach number, the skin friction reduction performance of boundary layer injection improves, and fuel boundary layer injection shows significant advantages compared to inert gas injection. Especially, hydrogen fuel boundary layer injection can achieve a total performance of around 600s and still has room for further improvement. However, when the mainstream fuel injection is used with boundary layer injection and forms a non-premixed suspended flame, it significantly reduces the potential for further performance improvement in additional boundary layer injection. This highlights the importance of fully optimizing the mainstream injection strategy in real engines before designing additional boundary layer injection on the engine. Otherwise, it would be a pseudo-optimization without practical significance.

Zhenming Qu, Feiteng Luo, Yaosong Long, Wenjuan Chen
A Piezoelectric Damping Support for the Vibration Suppression of Rotors

Elastic supports are widely used in flexible rotors of aero-engines. The principal function of elastic support is to provide the rotor with reasonable stiffness, on one hand to balance the inertia force of the rotor, on the other hand to reduce the stress on the shaft. To further suppress the excessive vibration when crossing the critical speed, dampers are generally mounted on the support. Piezoelectric materials have the advantages of strong electromechanical coupling capability and wide bandwidth. When the thickness of piezoelectric material is comparable to that of the substrate structure, it exhibits good damping performance. The main drawback is that piezoelectric materials cannot withstand too much loads. In this study, we propose the concept of a piezoelectric damping support for suppressing rotor vibration. The elastic support structure, distributed with piezoelectric materials, is utilized solely for generating damping rather than providing stiffness. An S-shaped elastic ring is designed to enhance the electromechanical coupling effect. The attached piezoelectric patches are grouped and interconnected with the synchronized switch damping on inductance (SSDI) to dissipate the vibration energy. The purpose of this work is to study the feasibility of the proposed piezoelectric damping support. To do that, the following works are carried out: (1) An elastic ring support based on S-shaped spring structure is designed, which ensures both the uniformity of radial stiffness and the rotationally periodic symmetry of strain distribution; (2) a numerical simulation is conducted for the rotor system to evaluate the damping performance. Results show that the novel damping support has high electromechanical coupling factor, and the damping effect is considerable for the rotor system. Towards engineering applications, the piezoelectric damping support can be installed in areas where deformation is suitable, and it can function in parallel with traditional elastic supports that primarily provide stiffness. Moreover, in contrast to the squeeze film damper, this damping support is oil-free.

Yu Hu, Yu Fan, Yaguang Wu, Lin Li
A Practical Method for Human Factor Assessment Scenario Development

To improve aircraft flight deck human-machine interface design and to demonstrate the compliance of human-machine interfaces related airworthiness regulation, human machine interface evaluation should be implemented during the whole design phases. Traditional human machine interface evaluation means always subject to data collection method and authenticity of assessment scenario. Base on this fact, “scenario-based” human factor assessment is essential and highly recommended methodology. The “scenario-based” approach is a methodology that involves a sample of various flight crew members that are representative of the future users, being exposed to real operational conditions in a test bench or a simulator, or in the aeroplane. Assessment scenarios designing is crucial part for the “scenario-based” Methodology. This paper proposed a practical scenario development method, which includes the scenarios development processes, development principles and methods for defining trigger events. Based on the method proposed, the assessment scenarios can be well designed to identify any potential deviations between the expected behaviour of flight crew and the activities of the flight crew that are actually observed, which helps to discover the design induced flight crew error and demonstrate the compliance of specific airworthiness regulation.

Yao Zhu, Xinrong Liu, Pengyu Yang
Prospect of Aero Engine Technology Based on “Carbon Peaking and Carbon Neutrality”

With the proposal of the “Carbon peaking and carbon neutrality” goal, in order to actively respond to climate change issues, more than 140 countries and regions around the world have actively responded. In Oct. 2022, the International Civil Aviation Organization (ICAO) determined at the 41st General Assembly of the aviation industry its long-term climate goal: to achieve net-zero carbon emissions from international aviation operations by 2050. Aviation kerosene combustion accounts for 79% of the aviation industry’s carbon emissions, so the innovative development of carbon reduction technologies in aviation power is the key point. Nine departments including the Ministry of Science and Technology, the National Development and Reform Commission, and the Ministry of Industry and Information Technology recently issued the “Technology-Supported Carbon Peak and Carbon Neutral Implementation Plan (2022–2030)” (hereinafter referred to as the “Implementation Plan”). The Implementation Plan carries out scientific and technological innovation actions and guarantee measures supporting the carbon peaking goal before 2030, and make technology research and development reserves to achieve the carbon neutrality goal before 2060. By 2025, major breakthroughs will be made in key low-carbon core technologies in key industries and fields, supporting an 18% decrease in carbon dioxide emissions per unit of gross domestic product (GDP) compared with 2020, and a 13.5% decrease in energy consumption per unit of GDP compared with 2020. By 2030, further research will lead to breakthroughs in a number of carbon-neutral cutting-edge and disruptive technologies, forming a number of low-carbon technology solutions and comprehensive demonstration projects with significant influence, establishing a more complete green and low-carbon technology innovation system, and effectively supporting the ratio of carbon dioxide emissions per unit of GDP. The emission level will drop by more than 65% of 2005, and energy consumption per unit of GDP will continue to decline significantly. Based on this, traditional aero-engine technology is facing huge impacts and challenges, and the structural form of aero-engines will undergo a qualitative leap. This article focuses on the development trends of aviation gas turbine engines driven by the “ Carbon peaking and carbon neutrality” goal: modularization of the entire engine, miniaturization of the core engine, large-scale fans, structural integration, and lightweight design.

Xiao Liang, Wei Sun, Qingchao Sun, Jian Song, Tian Xie
Three-Dimensional Distributed Affine Formation Maneuver Control of Fixed-Wing UAV Swarm with Actuator Faults and Saturation Constraints

This paper tackles the challenging problem of distributed affine formation maneuver control of fixed-wing UAV swarm considering the 6-DOF flight dynamics with actuator faults and saturation constraints. The UAV swarm adopts the “multi-leader-multi-follower” structure with directed network topology. A novel multi-layer control framework is proposed to achieve 2 objectives: affine formation maneuver control and robust fault-tolerant flight control. In the upper layer, a new kind of distributed fixed-time state estimator (DFXTE) is designed for each leader and follower UAV to generate the affine formation maneuver reference trajectory. In the middle layer, the kinematics controller is designed to track the commanded maneuver reference trajectory. In the lower layer, a sliding-mode-control (SMC) based robust fault-tolerant outer-loop dynamics controller is designed to achieve speed tracking, and a robust inner-loop dynamics controller is subsequently developed based on the backstepping method to precisely track the corresponding inner-loop angles and angular velocities with actuator faults. In the inner-loop controller, a fixed-time extended state observer (FTESO) based active disturbance rejection control (ADRC) is adopted with a novel kind of adaptive super-twisting algorithm (ASTWA) to enhance the system robustness. Moreover, an auxiliary compensator is to preserve the actuator saturation constraints, and adaptive neural networks (NN) are applied to approximate and compensate the flight dynamics coupling. Finally, numerical simulations are conducted and illustrate the effectiveness of the proposed multi-layer control framework for the affine formation maneuver control of the fixed-wing UAV swarm under the actuator faults and saturation constraints.

Boyu Qin, Dong Zhang, Shuo Tang, Yang Xu
Investigation of Smart Nano Rotor with Continuous Trailing Edge Flap Driven by Electroactive Polymer

Nano Air Vehicle (NAV) is widely used in the military, production, scientific research, and other fields. Meanwhile rotor thrust control methods widely used currently include using a controllable pitch propeller hub which has a complex structure with large mass, or a variable speed motor which leads to lower energy conversion efficiency. In order to obtain a rotor thrust control method with a simple structure and low additive mass, meanwhile won’t cause overconsumption of energy, a novel electroactive polymer is used as driving material to design a smart nano rotor with continuous variable trailing edge flap. When electric field is applied to the electroactive polymer driver, the continuous variable flaps at the trailing edge of the blades are driven to bending and thus change the thrust of the rotor. The mechanical parameters and electrostriction properties of the electroactive polymer materials were studied by experiments. A fluid-electric-structure multi-field coupling method is used to study the aerodynamic characteristics of a smart nano rotor with a continuous variable trailing edge flap driven by electroactive material under the control of active electric field. It is found that when the control voltage is 1000 V, the blade trailing edge was effectively driven by electroactive polymer to produce bending deformation, which led to the pressure difference between upper and lower blade surfaces increasing significantly. The Thrust of the rotor was increased by 17.20%. The results show that the continuous variable trailing edge flaps driven by electroactive polymer can effectively control blade lift without affecting rotor aerodynamic efficiency, which is a kind of thrust control method with good potential for nano rotors.

Zihan Kang, Zhen Liu, Fengwan Zhao, Jie Zhang, Haowei Du
Influence of Kinematics on Aerodynamic Characteristics of an Albatross-Like Flexible Flapping Wing in Forward Flight

Flapping wings have attracted much attention in recent years due to various merits. Many efforts have been made to study the kinematics and flexibility of flapping wings. However, the kinematics of flapping wing with bionic geometric shape and structural flexibility are still lacking in comprehensive exploration. In this paper, the aerodynamic characteristics and dynamic response of an albatross-like flapping wing undergoing different kinds of kinematics have been numerically explored. The results revealed the assocaition among flapping degree, pitching degree, phase difference, force coefficients and displacement response. Enlarging the flapping amplitude is beneficial to lift coefficient increasement, and introducing pitching is advantageous to drag coefficient declination. Compared with no phase difference between pitching and flapping, pitching phase lead can moderate lift coefficient changes in a smaller range with a good effect on retaining thrust, while phase lag may amplify that range at the cost of the drastically increasement of drag coefficient. The results provided a reference for the kinematic design of bird-like flapping wings from the perspectives of aerodynamic characteristics and dynamic response, and proposed a feasible method for the numerical simulation and analysis of bionic flexible flapping wings based on fluid-structure interaction.

Nongyue Gao, Changchuan Xie, Chao Yang
Coupling Environment Experiment Technique of Radiation and Convection Aerodynamic Heating in Wind Tunnel

A coupling environment experiment capability has been developed that incorporates mutual interactions between radiative heating and convective heating on FD-04 arc-heating wind tunnel of China Academy of Aerospace Aerodynamics (CAAA), which to date had been unattainable. The wind tunnel contains a multi-segment arc heater to generate high-temperature and high-speed airflow to simulate the convective heating part of the aerodynamic heating. It also equipped with a solar radiation simulator to makes up the radiative heating part in the total aerodynamic heating. This experiment technique had successfully proceeded on an aerothermal evaluation test of a certain kind of thermal protection material. Test results show that with the increase of the proportion of radiative heat flux, the mass and linear ablation rate of the material and the max temperature rise on the back of the models are reduced. The surface temperature of the models, on the contrary, grows with the increase of the proportion of radiative heat flux. Overall, this experiment technique extends the performance of arc-tunnel and provides a new aspect for delicate design on thermal protection system.

Yuxiang Liu, Denghao Jiang, Zhongkai Yang, Dongbin Ou
Study on Simulated Impact Test Between Bird Body and Inlet Wall

In order to determine the effect of large-angle curved intake ducts on bird ingestion in aircraft engines, simulating specimen impact tests of bird bodies against intake duct walls were conducted to study the changes in bird velocity and integrity after impact, so as to support the anti-bird impact design of aero-engine. Aluminum alloy plates with two different thicknesses and roughness levels were designed to simulate intake duct walls. Pigeons with different masses were launched to impact the aluminum alloy plates. High-speed cameras recorded the impact process to obtain the direction of velocity changes. The experimental results showed that pigeons did not experience rebound after colliding with the plates at different angles, and their velocity directions became tangent to the plate surface. The velocity of the pigeons decreased after impact, and the magnitude of the decrease was mainly related to the impact angle, surface roughness of the test specimen, and thickness of the test specimen. A larger impact angle, greater surface roughness, and greater thickness of the test specimen resulted in a larger reduction in velocity. The integrity of the pigeon body after impact was primarily affected by the impact angle. When the pigeons collided with the plate at angles of 15° and 30°, no fragmentation occurred, but surface abrasions, tearing of muscle tissue, and exposure of organs were observed. In most cases, fragmentation occurred when the pigeons collided with the plate at a 45° angle, with lightweight parts such as the head and wings detaching from the body and significant mass loss.

Haiyang Zhang, Fengqi Zhang, Wanting Cao, Gang Luo, Gongbo Liu, Peihong Cong, Ronghui Chen
Flight Time Prediction of Arrival Air Traffic Flows Using Time-Based Airspace Model Applying Machine-Learning Methods

Efficient airport operations are required as the demand for airports is expected to increase. In this study, we focused on arrival management in an air traffic system and attempted to predict flight times using machine learning. Results from our previous study indicate that it is essential to appropriately determine the airspace where the flight time is predicted in order to improve the prediction accuracy. Therefore, we propose the “time-based airspace” concept and apply it to a case study for the Tokyo International Airport. Time-based airspace is defined as airspace established based on an “equal time curve” calculated by clustering the positions of each aircraft at a certain time prior to arrival at the airport such that the average time required to arrive at the airport is equal. First, using the flight track data of arriving aircrafts, air traffic networks were constructed by applying kernel density estimation, and time-based airspaces were then designed based on the curves connecting each network node. Our proposed model results in a 20% reduction in variance of flight time compared to the previous “distance-based” prediction model and improves flight time prediction accuracy by 10%. Future prospects of our study include predictions using other methods, introducing other evaluation index, and further improving the airspace model.

Takuya Nishida, Eri Itoh
Experimental Research in Non-equilibrium Thermochemistry Diagnosis of High Enthalpy Flow Field

The diagnosis of the thermochemical non-equilibrium state of the high enthalpy flow filed is an important method to analyze the thermodynamics of the hypervelocity aircraft. Tunable diode laser absorption spectroscopy (TDLAS) can realize non- intrusive measurement of high enthalpy flow filed. Firstly, based on FD-21 high enthalpy shock tunnel of China Academy of Aerospace Aerodynamics (CAAA), NO and H2O absorption spectrum measurement system were built, and the setting details and calibration method of the TDLAS were introduced. Subsequently, the measurement error of the TDLAS system was calibrated based on stagnation gas, and the overall error was within 2%. Finally, a series of TDLAS measurement experiments were carried out in the FD-21 high enthalpy shock tunnel, and such as flow filed pitot pressure, flow field static temperature, NO pressure and flow field velocity were obtained. The results show pitot pressure has the consistent trend with static temperature and NO pressure measured by TDLAS. In the two experiments, the deviation of the static temperature is 3.3%, the deviation of the NO pressure is 8.2%. The average speed of the two experiments was 2487 m/s and 2523 m/s respectively. The FD-21 high enthalpy shock tunnel has good flow filed repeatability. Further compared with experiment and calculation results, the thermochemical non-equilibrium process is discussed, and the origin are analyzed.

Hua-zhen Song, Shuai Wen, Junmou Shen, Yi Jin, Xing Chen, Jian Lin
Numerical Investigation on an Under-Expanded Jet from a Rectangular Nozzle with Aft Deck

There are complicated flow field interferences between the jet-flow of engine nozzle and external flow of an aircraft, especially for the nozzle with aft deck, which probably cause the distortion of the alternating flow field morphology of shock and expansion waves in the state of under-expansion. Simultaneously, the interaction have significant impact on the flow capacity, thrust characteristics, jet direction of nozzle and the load of aft deck. Numerical simulations on an under-expanded jet from a rectangular nozzle with aft deck are performed to investigate the variation law of the aerodynamic characteristics and the jet direction under different installation angle of aft deck. The results indicate that fine mesh is necessary to capture a better results such as nozzle thrust coefficient, load distribution of aft deck, and a series of shock waves and expansion waves, and jet direction is changed obviously due to deflection of aft deck. The jet deflection caused by upward deflection of rear deck is stronger than that caused by downward deflection, accordingly, aerodynamic loss caused by upward deflection of rear deck have become more severe. The investigation on jet from nozzle with aft deck provide an effective approach and basis for the integrated design of nozzle and aft deck of new generation aircraft.

Hui Zhang, Wu-tao Lei
Accurate Weight Prediction of a New Aircraft’s Electrical System Based on Neural Network

Weight prediction is essentially important in the overall design of an aircraft. A conservative weight prediction will result in uncompetitive performance of the aircraft, while an optimistic one will result in the compromise of weight limit and aircraft performance. According to the composition and characteristics of aircraft electrical system and the experience of other aircraft design, a three-step weight prediction method of the electrical system is proposed. The weight prediction of electrical system is divided into three parts: the weight prediction of newly developed airborne equipment, the weight optimization and prediction of cables, the weight prediction of equipment and cable installations. Firstly, the weight of the newly developed airborne equipment is predicted by introducing two neural network structures: generalized regression neural network (GRNN) and fitnet neural network, then the neural networks are optimized to reduce the prediction deviation. For the best case, the weighted deviation reaches 3.40%. Secondly, the electric cable weight is accurately predicted through the optimization of cable weight by using three-dimensional (3D) numerical model and empirical method. Thirdly, the auxiliary weight of the installation of cables and airborne equipment include mounting brackets, protective covers, grounding, etc. are accurately predicted by using empirical data from weight database. The results show that the weight prediction process basically realizes accurate prediction of the total weight of the electrical system, and therefore improves the reliability of aircraft technical scheme and the accuracy of aircraft performance calculation.

Juhong Dang, Yining Gao
Fluid Simulation of Aerodynamic Interference of a Multicopter Type eVTOL Aircraft

In this study, the panel method for aerodynamic analysis was applied to the Quadrotor, which was a multicopter eVTOL (Electric Vertical Takeoff and Landing) aircraft proposed by NASA as a concept aircraft for AAM (Advanced Air Mobility). The eVTOL aircraft is expected to be environmentally friendly and convenient. On the other hand, the eVTOL aircraft have some issues such as cruising performance and noise. Based on the results of simulation, aerodynamic performance of the Quadrotor during each flight phase was analyzed by using a panel method and aerodynamic theories. In hovering flight, the rotor thrust and torque of the Quadrotor are larger than those of a single rotor, and it indicates that the rotor interference affects aerodynamic performance. When the rotor spacing was reduced, the thrust became larger insignificantly. In forward level flight, the maximum range was obtained at a cruising speed of 210 km/h. It is shown that the multicopter eVTOL aircraft investigated in this study has feasibility for using as the AAM in the future.

Karin Okawa, Zhong Lei
Numerical Investigation of Flow and Flight Performance of Lift & Cruise Type eVTOL Aircraft by a Panel Method

Recently, with the development of battery technology, electric propulsion technology, and control technology, research and development of eVTOL (Electric Vertical Takeoff and Landing) aircrafts have been widely conducted in the world. The eVTOL aircrafts are attracting attention as a near-future means of air transportation, and expected in response to the growing need of AAM (Advanced Air Mobility). In this study, flow filed and flight performance of the Lift & Cruise type eVTOL aircraft proposed by NASA were investigated by the panel method and aerodynamic theories at each flight phase, such as hovering and forward level flight. From the results of each flight phase, the flight performance, cruising range and time were estimated at different cruising altitudes. The maximum cruising time and range were achieved at speeds of 180 km/h and 210 km/h, respectively. The increase in battery energy density was expected to increase range and endurance. It was shown that the aircraft satisfied the specified mission with a battery energy density of more than 230 Wh/kg.

Shin Hyodo, Zhong Lei
Learning Aircraft Pilot Skills by Adversarial Inverse Reinforcement Learning

The aging population in Japan is causing a shortage of pilots in the aviation industry. This is expected to continue, leading to a severe lack of human resources in the future. The shortage will impact airlines’ operations and pilot training. Since training is costly and time-consuming, efficient pilot training is crucial. To address these future problems, incorporating artificial intelligence tools to support instructor pilots and trainees is an effective solution.In this study, we applied Adversarial Inverse Reinforcement Learning (AIRL), a practical and scalable method for imitating expert operations, to solve a landing problem for aircraft, which is an important and difficult task in training as well as actual operations. To obtain the operation model of expert pilots, we developed a new framework based on AIRL that incorporates multimodal information. This framework allows us to build an operation model with structures similar to human recognition systems, which can infer physical information.When expert pilots try to land, it is required to keep the aircraft states desired values under changing circumstances from time to time. Before learning a model of expert pilots, we analyzed time series data of expert pilots to find out their skilled control techniques.Our learning results demonstrate the effectiveness of our framework and the successful acquisition of expert piloting skills. By learning AIRL based on multimodal information developed in this study, a model that can generate maneuvers satisfying all the research objectives (constraints of speed, glide path angle, and touchdown point) was obtained. We also aimed to improve the performance of flare operations just before touchdown by conducting pre-training.

Kaito Suzuki, Tsuneharu Uemura, Takeshi Tsuchiya, Hirofumi Beppu, Yusuke Hazui, Hitoi Ono
Evaluating Effectiveness of Fixed-Flight Path Angle Descent to Kansai International Airport Using A320 Flight Data via Machine Learning Approaches

The full flight simulator experiments in this paper show that Fixed-flight Path Angle (FPA) descent consumes less fuel than flight with current control, and that fuel consumption can be reduced by properly selecting that angle of descent. It was also suggested that the optimal angle of descent varies with weather conditions. Therefore, this study applied machine learning to develop a highly accurate fuel consumption estimation model to determine the optimal angle of descent for FPA descent. As a result, a model with higher accuracy than existing models based on physical laws, such as BADA and ICAO, was successfully constructed. However, the accuracy of fuel flow estimation during FPA descent was lower than other flight phases including climb, cruise, and non-FPA descent. This result shows that applicability of the machine learning model is limited by the actual flight envelope of the underlying training data. These results suggest our future works to add extra loss terms including physical knowledge to evaluation function of the machine-learning model. We discuss on the selecting features and evaluation functions of the model to further improve the accuracy.

Yuki Nonaka, Daiki Iwata, Eri Itoh
A Novel Optimization Approach of Transonic Buffet for a Supercritical Airfoil

Enough margin from the cruise operating condition to the buffet onset is necessary to provide a margin of maneuverability for aircraft. This paper presents a novel optimization approach of transonic buffet for supercritical airfoils based on the lift curve break method using steady Reynolds-averaged Navier–Stokes simulation to improve optimizing efficiency. Three steady results (two lift coefficients corresponding to the cruise operating conditions with different fuel quantities, and one lift coefficient larger than that of the buffet onset) are fully utilized to explore the potential for improving buffet behavior of the supercritical airfoil while maintaining the aerodynamic performance at cruise operating conditions. The optimization results of a typical supercritical airfoil show that the buffet-onset lift coefficient is increased by 4.1% compared to the original airfoil, and the shock oscillation is significantly reduced at the same lift coefficient. The unsteady Reynolds-averaged Navier–Stokes validation results indicate that the optimized airfoil can increase the time-averaged lift coefficient by 5.6% at the same buffet magnitude as the original airfoil. In conclusion, this novel approach achieves efficient and practical optimization of transonic buffet for supercritical airfoils, which has the potential to improve the design level of modern high-speed aircraft.

Tianshi Cao, Junjie Fu, Junqiang Bai, Yasong Qiu, Feng Qu, Min Zhong
Hardware-In-The-Loop Simulation Environment with a Robotic Arm for Multicopter Performance Evaluation

The drone service market has been expanding rapidly in recent years, and demand for drones is expected to increase as well. In Japan, with the lifting of the ban on Level 4 flights from FY2023, an aircraft certification and licensing system for unmanned aircraft vehicle has come into effect. In conjunction with this, a more efficient drone performance evaluation method is needed. Currently, after testing the performance of the controller using a plant model built in a computer, the main performance evaluation test is a flight test in the field. Flight tests are expensive because they require a large site and involve risks such as crashes. Although national research institutes are conducting research on drone flight simulation using a robotic arm, the use of this technology is not widespread because it requires large-scale facilities and is limited in what it can do. If a small robotic arm can evaluate the flight behavior of a drone without flying it outside, it will accelerate the development and spread of drones. This study focused on the feasibility and methodology of a flight simulation in which a multicopter attached to a small robot arm is moved, the applied force is measured, and the robot arm reproduces the flight behavior accordingly. The environment necessary for simulation implementation was built and the simulation was implemented.

Yuya Kawasaki, Takeshi Tsuchiya
Effect of Large Stagger Angle Endwall on Secondary Losses in a High-Lift Turbine

The performance of low-pressure turbine (LPT) plays an extremely important role in high-bypass-ratio aero-engine, which significantly influences the engine performance and efficiency. Because of the requirement of weight reduction of LPT, high-lift profiles have been widely used in modern axial turbines. However, the usage of high-lift profiles usually accompanies strong secondary flow. How to reduce the secondary losses in the high-lift blade design has become an important research area.This paper proposes a novel design concept, large stagger angle endwall (LSAE). This kind of new design reconstructs the blade profile around the endwall by obviously increasing the stagger angle. The results obtained show a smooth transition between cylindric leading edge and hub endwall and obviously improved the local aerodynamic performance. A detailed numerical investigation was performed in a 7-stage high-lift LPT and the LSAE technology was implemented on the 2nd guide vane. The result revealed that, without LSAE technology, the complicated secondary flow in the upcoming inlet boundary layer brought inevitable effects on the downstream flow of blade or vane. The incoming flow has a high positive incidence angle near the hub endwall and leads to a high-pressure region and a pressure blockage. This could finally intensify the inlet boundary separation and cause high secondary losses. However, LSAE is able to adapt the high deviation of inlet flow angle. With better gradual transition on geometry from the leading edge to hub endwall, it firstly optimized the pressure distribution. The static pressure recovery between leading edge and 40% axial chord length position disappeared, and the cross-pressure gradient between pressure side and suction side at leading edge decreased. The pressure blockage was eliminated and the through-flow capability was enhanced at endwall. Then, LSAE changed flow structure. It reduced the roll-up of horseshoe vortex and made the streamlines of horseshoe vortex brunches follow the vane geometry well. As a result, the passage vortex and suction side corner vortex became smaller, resulting in the disappearance of the wall vortex. Also, the deviation of exit flow angle decreased. Finally, the loss of secondary flow decreased and the spanwise mass flux was more uniform at exit plane. Mass-averaged loss was reduced by 11.3%. The efficiency of the 2nd stage increased by 0.75%.Performance experiments of a 7-stage LPT were carried out in which LSAE technology was applied to the 2nd, 3rd, 4th and 5th vanes. The experimental result verified the feasibility and reliability of LSAE for engineering application. The final result improved the turbine efficiency by 0.29%.

Fan-Yan Meng, Wei-Tao Hou, Wei-Dong Shao
Wall Pressure Fluctuation on the Aircraft Fuselage: Part 1 Flight Test and Analysis of Anomalies

One of the main source driving the cabin sound level of an aircraft is the turbulent boundary layer (TBL), specially during cruise condition. The pressure fluctuations underneath the TBL along the external fuselage of aircraft have been studied extensively. Several engineering models have been proposed, mainly semi-empirical ones for zero pressure gradient but yet reliable models are still needed. Flight test measurements are mostly performed at the window location where complete flushness is not guaranteed. Other protrusions (sensors, steps, …) are also prone to affect the TBL but its influence in the downstream region is not known to the knowledge of the authors. The authors present the effect of the aircraft sensors on the TBL spectrum measured using surface microphones. The recording of the data is continuous during the whole flight test, then stable conditions in terms of Mach number, altitude, angle of attack and engine power settings are selected. Thanks to the continuous recording, anomalies in the overall sound pressure level and spectrum versus time were discovered. Sudden increases (switch on/off) of 3dB were observed, which was due to the change in angle of attack (AOA) after systematic analysis of the flight test data at several microphones. Thus a series of steady state CFD analysis was performed at different altitude and different AOA without any sensor. The surface streamlines starting from the surface microphones, also pass through the locations of aircraft sensor at specific AOA, providing the explanation of the switch on/off behavior.

Sun Yifeng, Cen Yipeng, Gu Shuqing, Song Xiao, Li Caihua, Breard Cyrille
Mixing Layer for Incompressible Flows: A Numerical Study

This study focuses on the mixing layer of two free streams under incompressible conditions. The convective Mach number was changed between 0.05 to 0.3. The detached eddy simulation with turbulent model k-ε was used for the calculation. The results of numerical data were validated with experimental data with the same convective Mach number of 0.185. The results indicated that the numerical scheme provided sufficient accurate data. The averaged flow fields, turbulent kinetic energy, and unsteady behavior were analyzed and discussed insight in this study.

Trung Dung Nguyen, The Hung Tran, Van Khiem Pham, Gopal Sharma, Jun Tanimoto
Investigation on the Effect of Honeycomb to the Leakage of Labyrinth Seal Within Support Seal System

Numerous studies have demonstrated the value of the honeycomb structure for improved seal performance, particularly for reduced leakage.However, the majority of the related simulations are performed with single seal. In order to make better simulation, this paper imported a more realistic flow field model with multiple labyrinth seals extracted from the support seal system in the low-pressure turbine part of a turbofan engine model.First, comparison of analytical and simulation leakage was made. The results of the simulation leakage were in acceptable agreement with the results of the analytical model that accounts for flow coefficient, seal type correction coefficient, and tooth number. Then, simulation for the system with multiple seals was carried out. Less leakage for every seal can be seen. Maximum reduction of leakage is 6.83%. Further, three different honeycomb cell size lands (1.1 mm, 0.8 mm, 0.5 mm) was introduced for isolated seals and support seal system. Maximum reduction of leakage is 20.50% with 0.5 mm honeycomb size. Less leakage from honeycomb configuration can be mainly attributed to flow separation into the honeycomb cells and turbulence kinetic energy dissipation.Analyzing the leakage of the support seal system, one conclusion was drawn, when structure or parameter of one single seal changes, the flow pattern within the whole system can be affected and further have significant impact on the leakage of the entire system.

Wei Zhang, Aleksandr S. Vinogradov, Peng Sun
Crawl and Fly: A Crawling Mechatronics Design for Bionic Flapping-Wing Micro Air Vehicle

In recent years, bionic flapping-wing micro-air vehicles (FMAVs) have received increasing attention due to their unique capabilities in maneuvering through complex environments and their ability to mimic biological organisms to confuse enemies. However, traditional FMAVs are limited to flying and cannot traverse certain terrains that require crawling, which has motivated researchers to develop dual-locomotion FMAVs. In this paper, we propose a novel dual-locomotion FMAV that overcomes the limitations of traditional FMAVs by combining both crawling and flying capabilities. The proposed design not only achieves dual-locomotion with a single motor, but also avoids the additional weight and complexity associated with an extra motor for crawling locomotion. This paper first introduces the composition and design principles of the FMAV, followed by the presentation of a 3D-printed model of the FMAV. Finally, a series of crawling and flying experiments conducted on the FMAV demonstrated that this design is capable of both crawling and flying.

Zhengmiao Yuan, Wenqing Yang, Jianlin Xuan
Maneuverability and Agility Evaluation of Fighter Based on Beck Metrics

Modern fighters still emphasize strong maneuver characteristics so as to have advantages in air combat. In the field of flight dynamic, the concept of maneuver characteristics includes maneuverability and agility. The traditional evaluation method of maneuver characteristics is to select specific maneuvers and take motion time or state directly as the evaluation parameters, which cannot fully reflect the combat superiority. Therefore, in this paper, the Beck metrics established based on the motion equation of aircraft under the Frenet axes system are used. According to the principle that maneuverability is the first derivative of aircraft trajectory and agility is the first derivative of maneuverability, the evaluation parameters are extracted to form the beck metrics. Then, Beck metrics are used to typical motions even post-stall maneuvers. The results show that Beck metrics can make use of the time-domain data of flight to calculate the maneuverability and agility in different axial directions quickly, which is suitable for any maneuver of aircraft. Finally, the application of Beck metrics in the field of model-based flight test is discussed. Maneuvering data obtained from flight test can be used to evaluate the maneuver characteristics, as well as to identify and calculate the aerodynamic parameters, so as to realize model verification.

Tao Liu, YiHai Li
Investigation of Helicopter Rotor Aerodynamic Characteristics in Axial Descent with Viscous Vortex Particle Method

In the present study, numerical simulations of helicopter rotor operating in vertical descent flight conditions are performed to investigate the effects of descent rate on the aerodynamic performance, axial velocity flowfield, and vortex field characteristics using the viscous vortex particle method. The rotor will enter the vortex ring state (VRS) when the descent speed approaches the hovering induced velocity, where the rotor lift loss and power loss reach the maximum value of 25% and 48.6%, respectively, and the effects of VRS on the blade tip (r/R = 0.96) are more serious than those on the inner blade (r/R = 0.68). The flow states for the helicopter rotor can be classified into pre-VRS, incipient VRS, fully developed VRS and windmill-like flow state, depending on the structure of vortex. With the increase of the descent rate, the axial downwash area of the rotor gradually becomes smaller due to the effect of wake compression, and when the descent rate is 1.0, the rotor is completely enveloped by a low-pressure area, leading to a sudden loss in its lift, which indicates the emergence of a fully developed VRS. As the descent rate further increases to 2.0, the rotor enters a windmill-like state, and the air flow completely passes through the rotor disk plane.From the perspective of the vortex ring formation, the flow field below the rotor mainly presents helicoidal structure in the pre-VRS. When the flow enters the VRS, the helicoidal wake of the rotor breaks down into a toroidal structure near the rotor tip, and a large recirculation zone is formed above the rotor disk. During the windmill-like flow state, the vortex dominated by the incoming flow is concentrated above the rotor disk, showing a relatively stable vortex structure.

Zeming Gao, Liu Liu, Tianqi Wang, Xueming Shao, Lifang Zeng
Wall Pressure Fluctuation on the Aircraft Fuselage: Part 2 Impact of Sensor Wake on the Spectrum

One of the main source driving the cabin sound level of an aircraft is the turbulent boundary layer (TBL), specially during cruise condition. The pressure fluctuations underneath the TBL along the external fuselage of aircraft have been studied extensively. Several engineering models have been proposed, mainly semi-empirical ones for zero pressure gradient but yet reliable models are still needed. Flight test measurements are mostly performed at the window location where complete flushness is not guaranteed. Other protrusions (sensors, steps,…) are also prone to affect the TBL but its influence in the downstream region is not known to the knowledge of the authors. The authors present the impact of the sensor wake on the wall pressure fluctuation spectrum. CFD-RANS is performed using several round of adaptation using feature detection based on the normalized Q-criteria. The investigated approach models the change in TBL characteristics at the microphone location far downstream. The TBL characteristics are locally affected by the tip-vortex and are injected into semi-empirical TBL spectrum models. The difference in sound pressure show that the noise level does indeed increase and the noise level can change suddenly around the maximum. Although the tip-vortex is well captured, and the outcome of this investigation clearly demonstrates the impact of protrusion, the results are under-predicted.

Shuqing Gu, Cyrille Breard, Yipeng Cen, Xiao Song, Yifeng Sun
Experimental Investigation on the Circular Cylindrical Cavity Noise at the Locked-on State

In the locked-on state, the ratio of resonant frequency to the fundamental frequency of self-sustained oscillation is suggested to play a key role in predicting the dominant tonal noise for the square cavity. In this paper, we similarly investigate the mechanism of coupled self-excited oscillation and acoustic resonance aerodynamic noise in cylindrical cavities with different depths at low speeds. The experimental noise field results are described for a circular cavity with a diameter of 78 mm and a depth ranging from 70 mm to 120 mm at an incoming flow velocity of 5 to 35 m/s. A strong self-excited oscillatory discrete noise is generated in this cylindrical cavity flow at the locked-on state and the parameter Rd is also well proofed to evaluate and predict the dominant mode order and the total sound pressure level peak.

Yifeng Sun, Peiqing Liu, Fengzhi Fan, Hao Guo
Aerothermodynamic Characteristics of Boundary Layer Transition of the Lifting Body

In the FD-07 hypersonic wind tunnel of the China Academy of Aerospace Aerodynamics, phosphorescent thermography measurement technology was used to conduct wind tunnel tests on the lifting body model under different Mach numbers and angles of attack. The surface heat flux distribution of the lifting body model was obtained, and the effects of Mach number and angle of attack on the boundary layer transition of the hypersonic lifting body model were analyzed. The results show that: (1) For the lifting body shape, the transition end position at the centerline is further back, while the transition positions on both sides are influenced by transverse flow and reattachment and are closer to the leading edge. (2) Under Ma = 5 conditions, the heat flux rapidly increases near Y = 100mm from the head, forming a “W"-shaped division line of heat flux values and exhibiting obvious transition phenomena. With the increase of incoming Mach number, the transition position of Ma  =  8 moves further back, forming a narrow and elongated “W"-shaped division line of heat flux values near Y  =  240 mm from the head. (3) Under Ma  =  5 and different angles of attack conditions, the transition position is located near Y  =  100 from the head, and its variation is not significant with the increase of angle of attack. The shape of the division line of heat flux values changes significantly with the increase of angle of attack.

Rui Ye, Suo zhu Wang, Wenling Liu, Xin Jin
Identification of Key Factors Affecting the Safety Design of Aviation Piston Engine Based on Kriging-Sobol

Aiming at the safety of aviation piston engines and the complex issues of inefficient calculation by traditional safety evaluation methods, a model-based system safety analysis method based on Kriging-Sobol is proposed to research the design safety of piston engines and to identify key parameters. Depending on the characteristics of aviation piston engines involving multiple physical domains and model-based safety evaluation criteria, the Kriging model is used to enhance the computational efficiency, and a quantitative safety evaluation model is established by the concept of Sobol variance. Results show that the calculation method using the Kriging model could save 95.58% of the calculation costs; under the case in this study, the impact of injected mass per cycle on the safety of the overall engine is the greatest. The method not only improves the efficiency of identifying key factors of aviation piston engine safety evaluation and saves costs of iterations in design phase, but also compensates for the deficiency of engine safety evaluation in multiple physical domains.

Guo Li, Yida Teng, Mengyao Bao, Tongge Xu, Zilu Wang, Shuiting Ding
Technology of Static Test for Slat on Large-Aspect-Ration Wing

The slat is an important component of the aircraft high lift system, which play a crucial role in the takeoff and landing process of an aircraft. The slat structure of aircraft in service may undergoes significant deformation and inclination due to the wing deformation for civil airliners with high aspect ratio wings, which make the test load on the wing and the direction of the test load on the slat must be adjusted in the static strength test. To ensure the simulation of the loading boundary and the application of loads for each section of the slat structure accurately, the structure strength test schemes of slat based on high aspect ratio wing that meets airworthiness requirements was proposed, which taking into account the deformation characteristics and structure of the slat in service under various loading conditions. Through the technical research such as specimen support, boundary simulation, load processing and load application design, a comprehensive load process flow of test and principle for slat test were established, and the key technologies such as precise load application under large deformation states and complex boundary simulation were broken through at the same time. Based on the above technical scheme, multiple assessment condition of tests such as packed up and unfolded status of slat were successfully completed on a certain type of passenger aircraft. The test results showed that the proposed test scheme is reasonable, the test fixture and loading system are reliable, and the accuracy of the control system and the load system in the test meet the error requirements and airworthiness regulations. In addition, the test results can be used to evaluate the strength and stiffness performance of the slat structure, and provide support for correction of finite element model and optimization of test measurement and control parameters, which can improve the development progress and quality of the model effectively.

Liu Bing, Zhang Jianfeng, Wang Mengmeng, Luo fei, Zhou Luanliang
Study on the Fault Diagnosis Method of Compressor Instability by Fusing Multiple Time Domain Feature Parameters

To fulfil the active safety control requirements of high-performance aero-engines, an efficient, accurate, and reliable method has been developed to diagnose compressor aerodynamic instability. my the one-way ANOVA was used to optimize the time-domain parameters selection for detecting the instability precursor state. A model was then trained using a classification algorithm to detect the precursor of compressor instability, and a method for monitoring and warning the axial compressor instability by fusing multiple time-domain feature parameters was proposed. The results showed that the compressor exhibited specific precursor characteristics in the sound signal before instability at both speeds. Through validation with data from other test runs of the compressor, the method proposed in this paper effectively diagnosed and identified the aerodynamic instability precursor.

Yuxi Chen, Mingsui Yang, Zhibo Zhang, Meng Wang, Bobo Jia
Phosphor Thermography for Global Heat Transfer Measurement in High-Enthalpy Shock Tunnel FD-21

The phenomenon of self-luminescence in high enthalpy flow field will have a serious impact on all kinds of optical measurement techniques, and make the effective information completely drowned. In this paper, a comprehensive filtering method based on the physical hardware and reference point image processing is established, and the phosphor thermography experiments of total temperature is 2700K and 4700K are carried out in the high enthalpy shock wave wind tunnel FD21 of China Academy of Aerospace Aerodynamic using the compressed corner shape. The experimental results show that the interference of the self-luminescence on the phosphor thermography increases with the total gas temperature. When the total temperature is 2700 K, the heat flux distribution of the compressed corner shape surface is obtained, and the peak value of heat flux on the wedge surface is accurately captured. The phosphor thermography is consistent with the measured results of thermocouple. When the total temperature is 4700 K, the strong self-illumination almost completely submerges the effective image information, and the experimental data is seriously distorted. In this case, more effective methods should be adopted to reduce the influence of self-illumination.

Jia Guangsen, Jin Xin, Ji Feng, Chen Nong, Chen Xing
A Comprehensive Design Method for Load, Stiffness, and Strength of High Altitude Long Endurance UAV

Solar powered unmanned aerial vehicles have the characteristics of high flight altitude, light structural weight, low wing load, large geometric deformation, and significant aeroelastic effects. If traditional design methods are still used to design such aircraft, there will be problems such as multiple design iterations, long design cycles, cumbersome design work, and optimization of design objectives. This article provides a detailed introduction to load design work using existing design methods through a design example. Preliminary proposal of a comprehensive design method for load/stiffness/strength based on “load configuration”. Finally, based on the design example in this article, the comprehensive design method is used to compare the analysis methods of external and internal loads, as well as the design results of the main beam. The design results show that using this method can effectively reduce the weight of the structure.

Yingyu Hou, Qi Li, Ziqiang Liu
Effect of Mass Flow Rate on Drag Reduction with Counter-Flow Jet in Laminar Hypersonic Flow at High Reynolds Number

One of the effective ways to reduce drag is the counter-flow jet. However, the correlation of the design parameters of the counter-flow jet and the complexity of the flow field make it difficult to comprehend the mechanism of the counter-flow jet for drag reduction. In order to solve this kind of the problems, the numerical investigations were carried out in hypersonic flow to investigate the effect of the mass flow rate at a fixed Mach number of the counter-flow jet. For simulations, laminar, unsteady, axisymmetric, Navier-Stokes equations were solved by using the symmetric TVD schemes with second-order accuracy in space and explicit strong stability preserving Runge-Kutta (SSPRK) for time integration. Based on the numerical outcomes, it was discovered that the counter-flow jet’s mass flow rate can classify the flow field as LPM or SPM. The PR and mass flow rate are related to the shock structure of the counter-flow jet. The drag can be decreased by up to 48% using a counter-flow jet.

Hee Yoon, Kojiro Suzuki
Numerical Analysis on the Characteristics of the Exhaust Plume During the Re-Entry Phase of Vertical Landing Reusable Launch Vehicle Under Different Altitude

In order to examine the characteristics of the exhaust plume during the re-entry phase of vertical landing reusable launch vehicle, a supersonic high-altitude plume model is developed using two-dimensional multicomponent Navier-Stokes equations and realizable k-ε turbulence model. The flow field of the launch vehicle at altitudes of 0 km, 5 km, 10 km, 15 km, 20 km and 25 km is calculated using the discrete ordinates method and the second-order total variation diminishing (TVD) upwind scheme. The findings indicate that as altitude decreases, the length of the plume experiences an initial increase, followed by a decrease, and then increases again, while the surface temperature of the rocket gradually decreases, and the angle of the shockwave increases. The temperature on the rocket side wall decreases linearly as the distance from the nozzle increases. On the other hand, the temperature on the rocket base increases and changes parabolically as the distance from the axis decreases. This paper reveals the characteristics of the exhaust plume in the re-entry stage of the vertical landing reusable launch vehicle. The research results have theoretical and engineering significance for the design of the re-entry stage of the vertical landing reusable launch vehicle.

Dehua Cao, Zhitan Zhou, Yiqing Li, Ranhui Liang, Taiyu Cao
Investigation of Vibration Characteristics of Wind Tunnel Rigid Model Based on Material Optimization

Vibration issues in wind tunnel experiments involving rigid models significantly impact the accuracy of experimental data and structural safety. This paper aims to improve the vibration characteristics of wind tunnel test models through material optimization. By reducing model weight and adjusting weight distribution, the low-order natural frequencies of the model are optimized to avoid resonance phenomena. In this study, a high aspect ratio low-speed wind tunnel test model is chosen as the research object, and a comparative analysis is conducted between a full-metal model and an optimized carbon fiber shell model using modal analysis. Modal calculations and structural strength analyses are performed using FEM software to evaluate the vibration characteristics and structural safety of the models. The research findings demonstrate that material optimization can significantly enhance the vibration performance of wind tunnel test models, thereby improving the accuracy of experimental data and the structural safety.By improving the vibration characteristics of wind tunnel test models, researchers can obtain more accurate data, improving our understanding of the principles of fluid dynamics and advancing our ability to design more efficient and effective aircraft and other flying objects.

Si-Peng Li, Yue Xu
Research on the Effect of Front Variable Area Bypass Injector Modulation on the Adaptive Cycle Engine Performance Based on Multi-fidelity Simulation

In this paper, two types of Front Variable Area Bypass Injector (FVABI) Computational Fluid Dynamics (CFD) models for axial type and rotary type are established and their operating characteristics are generated. The performance of the two types of FVABI under two operating modes is compared considering the Adaptive Cycle Engine (ACE) matching requirements. A multi-fidelity simulation model is established based on the coupling calculation of the 2-D FVABI and 0-D ACE performance model. A throttling performance control law design method is proposed based on fitting multiple data points. The effects of different modulation settings of the FVABI on the optimum control law and performance of the ACE under various operating conditions are simulated and analyzed. Simulation results indicate that, with the same mass flow modulation capacity, the axial type FVABI could realize equal or higher total pressure recovery coefficients in both ACE operation modes. Considering the collaborative modulation of other ACE components, the different FVABI modulation states could result in up to a 3.2% reduction in maximum thrust in the intermediate conditions. For the ACE constant inlet airflow throttling performance, the FVABI modulation could reduce the Specific Fuel Consumption rate (SFC) by 2% and 1.3% in the deep throttling intervals in subsonic and supersonic cruise conditions, respectively. The FVABI modulation has less effect (relative difference less than 0.2%) on SFC in the non-deep throttling interval of the throttling process.

Zhewen Xu, Hailong Tang, Jingmei Cong, Min Chen, Jiyuan Zhang
An Improved Engine Model Adaption Method Based on Search Interval Optimization

Aeroengine performance model is an important tool to reflect the engine working condition and evaluate the engine performance. The engine model adaption method based on nonlinear component-level performance model is an important technical support to achieve accurate assessment of engine performance. However, when traditional optimization algorithm-based model adaption method is applied to the actual issues, especially when the known information for model adaption is insufficient, the accuracy of the model adaption is easily affected by the search interval of the independent variables, and problems such as smearing effects and local optimality can easily occur. In this paper, an improved engine model adaption method based on initial search interval optimization and interval adaptive adjustment is proposed. This method can effectively use the initial deviation information of model and target parameters and the feedback from the optimization algorithm in the adaption process, realizing the function of “optimizing the search interval before adaption and dynamically adjusting the search interval during adaption.” By applying these two methods to genetic algorithm (GA), the robustness of the adaption method based on nonlinear component-level performance model can be effectively improved, and the accurate evaluation of engine performance under multiple information conditions can be realized. The effectiveness of the method was verified by using ground state data of a mixed flow turbofan.

Shaochen Li, Hailong Tang, Min Chen, Huayu Fu, Jiyuan Zhang
Study on Versatile Modular Engine Performance Simulation Platform

With the development of aviation industry, advances in engine modeling have become synonymous with increased complexity. In this paper, we present a versatile modular engine performance simulation platform based on MATLAB/SIMULINK to build an integrated system for engine performance and analysis. The platform provides standard components for engine models and allows users to introduce new function modules for novel engines. Given that the Newton-Raphson method has a second-order convergence rate, the steady state model is still solved using a Newton-Raphson solver. To address the complexity of high-dimensional issue in engine modeling, several “Turbomachine-volume” systems are established to transfer it into multiple simple and linear issues. In addition, auxiliary volume modules are built to pass the downstream imbalance information upstream. Based on this component-level engine model, we developed an installed performance estimation tool that quantifies installation loss due to matching with the inlet and nozzle to reduce the iteration times of aircraft and engine co-design. By comparing with Gasturb and test values, the deviation of section parameters and performance parameters are both within 4.26%. The relative errors between simulation results and test value in acceleration process are less than 4.4%, while variable cycle engines enable mode transition processes as well. The versatile engine simulation platform established in this paper is highly accurate, expandable, and efficient, providing a flexible and efficient tool for optimizing aircraft engine design parameters, designing control systems, diagnosing faults, etc.

Li Deng, Min Chen, Hailong Tang, Jiyuan Zhang, Yudong Liu, Yi Xiao
Design and Parameters Analysis of a Solar Powered UAV for Extended Endurance

This paper presents a conceptual design methodology for solar-powered range-extending unmanned aerial vehicles (UAVs) based on the solar-powered range-extending coefficient. Solar-powered range-extending UAVs are primarily designed for daytime flight. The design methodology is based on energy and mass balance during level flight. Based on the Keidel solar irradiance model, the solar cell model, the maximum power point tracker (MPPT) model and lithium battery model, a simplified model for energy acquisition and storage is developed for the UAV. The factors influencing the solar-powered range-extending coefficient are analyzed by deriving the energy balance. The impact of the solar-powered range-extending coefficient, endurance time, and other key parameters on the overall parameters of the UAV such as cruise speed, wing load and payload coefficient is discussed. To verify the method, a hand-launchable UAV with a wingspan of 3.2 m was designed and constructed. Flight tests demonstrate that the UAV can sustain over 8 h of flight time in ecological monitoring tasks.

Zong Jia, Zhou Zhou, Shao Zhuang
Simulation of Propeller Slipstream and Its Effect on Wing

In this paper, a specific configuration of tilt-rotor eVTOL with the propeller installed in front of the wing was analyzed. We do the coupling design of pylon and wing and then unsteady RANS CFD method with sliding mesh strategy was applied for the rotation domain, and attention was paid to the propeller-wing coupling effect. For the propeller, compared with the isolated condition, the inner propeller thrust decreased slightly (about −2.1% at α = 0°) and the efficiency reduced a little (about 1% at α = 0°) in the case of coupling with the wing, but the outer propeller thrust increased by 2.3%, presenting a symmetric situation, and the cruise efficiency remains unchanged. For the main wing, the direction of rotation of the outer propeller affects its aerodynamic characteristics: When the rotation direction is inboard-up, the lift coefficient of the whole aircraft was increased by 5.6%, and the lift-drag ratio is reduced by 2.9%. The aerodynamic efficiency of inboard-up is higher than that of the inboard-down, because the propeller slipstream introduced by the propeller whose rotation direction opposite to the wingtip vortex cancels out part of the downwash effect of the wingtip vortex, resulting in lower induced drag. This counteracting effect is also transmitted to the upstream propellers in reverse. The propeller slipstream also changes the angle of attack and velocity of the local air flow on the wing, so the surface pressure distribution and circulation distribution are changed. The installation position and rotation direction of propeller have a profound effect on slipstream, wingtip vortex, etc.

Qinze Zheng, Yu Liang, Xiaowen Shan
Simulation of Carbon Dioxide Flow Field in Shock Tunnel

Martian spacecraft landing is one of the key technologies of Mars exploration and one of the challenges in the development of Mars lander. The serious challenge is that its aerodynamic environment is far different from the air in Earth’s atmosphere. The operation characteristics of the FD-20A shock tunnel under the carbon dioxide flow field are simulated by numerical calculation technology and test measurement. The generation and propagation process of the wave system and the interaction mechanism between the reflected shock wave and the contact surface are simulated by adjusting the initial parameters of the driven and driven gas in the shock tube. The aerodynamic parameters of the driver section and the driven section of the FD-20A shock tunnel are adjusted. By measuring stagnation heat flux at the nozzle exit, combining with theoretical analysis and numerical simulation results of shock tube, nozzle, and test section, the experimental conditions are analyzed with the stagnation parameters of 1140 K and 14.2 Mpa. The test flow fields with Mach numbers of 8.03 at the nozzle exit are obtained.

Dapeng Yao, Junmou Shen, Dan Wang, Huilun Wang, Feng Ji
Numerical Study on Damage Characteristics of Composite Propeller Under Blast Impact Load

The finite element program was used to establish a simulation model to simulate the dynamic response process of the composite propeller of the engine and the connected wing part under the explosion impact load. CONWEP equation of state was used in the model to simulate the explosion impact load. The failure of the composite propeller was controlled by unit removal in combination with the Tsai-Wu tensor strength theory in the VUMAT subroutine. To achieve impact damage of laminate. The damage effect of engine composite propeller under explosion load is analyzed and the dynamic response of composite propeller under different explosive charge and different distance is compared. It is concluded that the damage of composite propeller is more serious with the increase of incident overpressure. Under high incidence overpressure, the composite blade fails and deformates, the nearby skin structure festers, and can not continue to fly, which is severe damage. At this time, the peak incidence overpressure is 0.36 MPa. Under the medium incidence overpressure, the blade deforms greatly and the surrounding skin structure deforms and tears, which is moderate damage. At this time, the peak value of the incident overpressure corresponding to the skin is 0.08 MPa. The blade is slightly deformed under small incident overpressure, which has little effect on flight and is slightly damaged. The evaluation of the damage effect of anti-aircraft weapons on aircraft targets will help to grasp the damage ability of anti-aircraft munitions, improve and optimize the damage efficiency of anti-aircraft warheads, and also provide an important basis for improving the survivability of aircraft under ammunition attack.

Xin Yao, Yang Pei, Yuxeu Ge, Kefan Liu
Analysis of Structural Characteristics of a Tandem-Wing Layout Vertical Takeoff and Landing UAV

The front wing (Frt-wing) and the after wing (Aft-wing) of the tandem-wing layout vertical takeoff and landing UAV are connected by supporting connecting rods to form the wing coupled configuration. It is of great engineering significance to study the influence of the supporting connecting rods on the structural characteristics of the tandem-wing layout UAV. Based on the structural preliminary design of the UAV, the structure finite element model of the wing coupled configuration and the wing uncoupled configuration were established. The aerodynamic load calculation model based on vortex lattice method is also established. The results of structural statics analysis of UAV show that the supporting connecting rods can improve the structural stiffness of UAV to a certain extent. The regular modal analysis of UAV shows that the supporting connecting rods has a great influence on the inherent modal characteristics of the UAV. The dynamic aeroelastic analysis shows that the wing coupled configuration can improve the static aeroelastic characteristics of UAVs to some extent and has higher flutter speed.

Junlei Sun, Chunqi Li
Development and Application of a Calculation Program for the Landing Distance of Civil Aircraft

The landing distance of civil aircraft is the key parameter to evaluate aircraft landing performance, which is significantly important to flight safety and flight economy of civil aircraft. The present study developed a calculation program for aircraft landing distance through the understanding and analysis of the aircraft landing process and its phenomenon. The calculation program combines kinetic and dynamic analysis models for both the aircraft landing and taxi stages. The full aircraft polar curve is utilized to predict the overall lift and drag characteristics of the wing, fuselage, and flat tail. Additionally, the kinetic and dynamic analysis models consider the effects of the aircraft landing configuration, including the landing gear trend, aircraft flaps, and spoilers, on the lift and drag characteristics of the aircraft. The calculation program was developed and verified using MATLAB language and the calculation results were compared with those of the Airbus landing performance software FlySmart. The relative error was within + 3%. Then the calculation program was employed to calculate the aircraft’s approach speed and landing distance under various conditions for one airport.

Xiangyang Xu, Liangxing Li, Yue Teng, Zutao Xiang, Huagang Shi, Weicheng Qu, Guannan Chen, Fujuan Li
Transformer-Based Method for Unsupervised Anomaly Detection of Flight Data

Achieving efficient flight data anomaly detection is a key technology for monitoring aircraft flight state and identifying unsafe flight behavior and is a basic requirement for intelligent flight control of future aircraft. Flight data belongs to multivariate time series, which has inherent attributes such as long series, many variables, lack of labels, unbalanced distribution of abnormal and normal samples, etc. At the same time, the high accuracy requirement of flight data abnormality detection and the limitation of computing resources bring great challenges for practical applications.To address these issues, this paper proposes an unsupervised flight data anomaly detection method based on Transformer and adversarial training. This method is based on the Transformer architecture, uses the attention mechanism to model long-term dependencies in the time dimension, and introduces a convolutional neural network block to better capture local contextual features within the sequence window. Adopting two-stage adversarial training with a loss constraint mechanism enhances the stability and generalization of the model.This paper validates the model using real-world datasets, including MSL, SMAP, and SMD. The results show that the detection effect is better than LSTM-VAE, MAD-GAN, and OmniAnomaly. In addition, the model is trained and tested using QAR data. The experimental results show that the anomaly detection method proposed in this paper can accurately locate the time of anomaly occurrence in-flight data with a prediction accuracy of 0.9017.

Hao Yu, Honglan Wu, Youchao Sun, Hao Liu
Comparison Design and Performance Analysis of Aerodynamic Configuration for Swarm Unmanned Aerial Vehicle with Rotate-Morphing Wing

This paper has investigated comparison design and performance analysis of aerodynamic configuration for swarm UAVs with a rotate-morphing wing. Firstly, four aerodynamic configurations of swarm UAVs are proposed to be suitable for complex tasks in subsonic and supersonic flight. These configurations employ various fuselages and high or low rotate-morphing wings. Secondly, aerodynamic analysis of four configurations is conducted by a robust numerical method of the modified SST turbulence model. The preferred configuration is gained, which consists of a high wing, X-shaped rudders, and a blunt fuselage of flat upper surface. It has good stability, cruise lift-drag performance, and less disadvantageous flow interference with the rotate-morphing wing and fuselage. Finally, to meet the task requirements of various flight segments, performance analysis is conducted at the rotate-morphing wing sweep angles of 0° and 45° for the preferred configuration. The research shows that the preferred aerodynamic configuration has outstanding aerodynamic performance and to better fit for swarm UAVs than other configurations. Its cruise longitudinal and lateral stability is not less than 10% and it is suitable for subsonic and supersonic flight endurance. It maintains longitudinal and lateral stability with wing sweep angles of 0° and 90° at both subsonic and supersonic while exhibiting lateral-directional asymmetric and flow field at wing sweep angles of 45°, which is needed to deflect the rudders to achieve steady flight. The numerical simulation analysis of different rotate-morphing wing sweep angles is beneficial for aerodynamic performance comprehensive evaluation to meet the swarm UAV needs of different mission stages. These can provide an aerodynamic configuration design and performance analysis idea for swarm UAVs.

Wenbiao Gan, Xianzhi Zhang, Zhenjie Zuo, Yi Zhang
Overview of the Payload Support Capability of the Aerospace Basic Experiment Rack of the China Tiangong Space Station

China’s Tiangong space station has been fully completed by 2022, marking the entry of China’s manned space engineering into a new development phase with space science, space technology and space application research as important tasks. The rich application resources of the space station provide a broad and open experiment platform for on-orbit technology verification. In the field of space technology experiment on the Chinese space station, the Mengtian Experiment Module of the Tiangong Space Station has been equipped with an aerospace basic experiment rack to support the verification of new space experiments in the microgravity environment of long-term space. Utilizing the in-module space environment conditions provided by the manned space station, as well as the on-orbit operation, maintenance and replacement capabilities of astronauts, and based on the constraints of external resources such as machinery, electricity, heat, information, measurement and control, the space base experiment rack provides an excellent open experiment and verification platform for the space station’s payloads.This paper comprehensively combs the experiment support capability of the space base experiment rack from the aspects of structural mechanism function, information management function, power distribution control function, thermal control function, etc., summarizes the constraint indexes of the rack on the mechanical, power supply, information and thermal interfaces of the payload unit inside the rack, and formulates the on-orbit experiment process of the payload inside the rack, which provides useful references for the relevant experiment payloads to carry out the on-orbit experiment by using the space base experiment rack. It provides useful reference for the relevant experiment payloads to carry out in-orbit experiments using the space basic experiment rack.

Zhao Yin, Pei Guo, Zhengyi Wang, Jinlu Yang, Yan Song, Zhenhao Zhao, Chao Cheng, Ai ming Wang
Aerodynamic Efficacy of Changing the Chordwise Installation Position of Multi-winglet on Commercial Aircraft

This study investigated multi-winglet availability in transonic civil aircraft and the aerodynamics of changing the winglet attachment position for the main wing. Multi-winglet decreases drag for wingtip vortex dispersion and increases lift due to gaps between the winglets, but previous studies have only been investigated under subsonic conditions. Also, the past perspective was on the effect validation of the winglet pluralization; no study was performed regarding the position of the multi-winglet on the main wing. We diverted this multiplying concept to a transonic civil aircraft and analyzed the aerodynamics of its model with three nonplanar winglets placed on the upwind and downwind sides of the main wing. Furthermore, we compared the results to the computational mode without any winglet. As a result, both multi-winglet models improved the lift-to-drag ratio of the whole body compared to the no-winglets model because the connection of the winglets and the main-wing shock waves enhanced lift by expanding the negative pressure area on the main wing to the multi-wing tips. Moreover, the lift-to-drag ratio of the downwind type was higher than the upwind type because each shock wave on the multi-winglet extended by the shock on the main wing in the upwind type, which increased the wave drag.

Erina Kobayashi, Kazuhisa Chiba
Analysis of Hydrodynamic Ram Effect of Aircraft Fuel Tank Filled with Foam Under Fragment Impact

Modern combat aircraft usually fill the tank with foam, which has been proven to reduce the ignition probability of the tank under fragment impact. However, there is a lack of systematic study on the impact of foam filling on the hydrodynamic ram effect of fuel tank. In this paper, the influence of foam filling and other factors on the hydrodynamic ram effect of tank under fragment impact is studied by numerical simulation. First, a simplified fuel tank model is established by referring to the wing fuel tank of a certain combat aircraft. Then, the finite element model for hydrodynamic ram effect simulation is established and the load transfer between foam, fuel and fuel tank is simulated by ALE algorithm. Finally, the hydrodynamic ram effect of different fragment velocity, liquid filling ratio, tank size and foam filling were simulated and analyzed. Through this study, the following conclusions can be drawn: 1. Filling foam in the tank can significantly reduce the hydrodynamic ram effect under the impact of high speed fragment; 2. In a given situation, there is a size that causes the most severe structural damage to the tank due to the hydrodynamic ram effect. The methods and conclusions of this study can provide basis for the anti-damage design of battle aircraft fuel tank and the high survivability design of aircraft, as well as provide criteria for the battle damage assessment of fragmented warheads to aircraft.

Meng-tao Zhang, Yang Pei, Yin-jie Ma, Yu-xue Ge
Propulsion Performance of Multiple Pitching-Heaving Airfoils in Side-by-Side Configurations

In nature, flying animals and swimming fishes flap their wings or fins to achieve excellent movements within the low Reynolds number regime. Their complex flapping kinematics are often reasonably simplified into the pitching-heaving motion of a two-dimensional (2-D) airfoil or hydrofoil, which can be further upgraded to multiple airfoils or hydrofoils in either tandem or side-by-side configurations when insect swarms or fish schools are considered. Here, the propulsion performance of pitching-heaving airfoils in the side-by-side configuration is examined via numerical simulations. The research starts with finding an preferable propulsion status for a single airfoil and then, to further guide the practical design of a multiple-flapping-wing micro air vehicle (MAV), the biplane and triple airfoil configurations are then considered. Results show that, for a single airfoil undergoing pitching-heaving motion, high propulsion efficiency is obtained when the amplitude of the effective angle of attack is around 20°. The corresponding reduced frequency should be confined within a certain range that goes up slightly as the Strouhal number increases. When placing airfoils in the side-by-side configuration, the contribution of clap and fling motion can enlarge the thrust and efficiency, which becomes prominent when the minimal inter-foil gap decreases. The enhancement led by a single clap and fling phase is found to be relevant to a novel flow structure. The middle airfoil of the triple configuration experiences dual clap and fling phases and almost double its thrust enhancement. Compared to previous research on pitching-heaving airfoils, our findings explain the fluid-mediated interaction between multiple (>2) pitching-heaving airfoils in the side-by-side configuration without a limit of total heaving amplitude. These findings can provide insight into determining the wing number of a MAV with multiple flapping wings sharing a stroke plane.

Kai Wang, Long Chen, Yanlai Zhang, Jianghao Wu
Numerical Simulation Method for Aeroengine Blade Impacted by Large Gravel

When the aeroengine works in the harsh environment, it will inevitably inhale the particles such as gravel, hail and debris with large particle size and high hardness, which will cause impact damage to the blades and seriously affect the engine performance. Numerical simulation of this problem exists in the solid structure of the large deformation of the crushing and the movement of the damage products and other computational difficulties. In order to solve these difficulties, this paper adopts Finite Element Method (FEM) to simulate the large gravel and engine blade, simulates the motion of the damage products through the Smoothed Discrete Particle Hydrodynamics (SDPH) method, adopts the new FEM-SDPH transformation algorithm proposed independently to simulate the damage of the blade, and then through the transfer of data such as the velocity, coordinates, and the contact force, develops the SDPH-FEM numerical simulation of the problem of aero-engine blades affected by the impact of large pieces of gravel. The algorithm is used to numerically simulate the damage of compressor blade by large gravel impact, and the shape is obtained in good agreement with the actual, which verified the accuracy and practicability of the numerical method, and provided a reference basis for the prevention of damage of aeroengine blade by large gravel impact.

Tengda Shi, Fuzhen Chen, Hong Yan
Optimization and Evaluation of Supersonic Civil Aircraft Propulsion System Scheme Design Driven by Multiple Evaluation Indicators

In response to the issues of long design cycle and relatively independent design process and indicator evaluation in traditional propulsion system design method, this paper establishes a method for rapid optimization design and evaluation driven by multiple evaluation indicators. Starting from the analysis of the engine performance impossibility triangle, an EPN (Essential-Preferential-Noteworthy) hierarchical framework of indicator importance is proposed in the initial design stage, which classifies numerous evaluation indicators according to their importance. During the design process, a multi-objective optimization model is established by combining genetic algorithm with the EPN framework. This integrates the trade-off relationships of different indicators into the optimization design process, achieving rapid and automated optimization of system scheme. In the scheme evaluation phase, the Analytic Hierarchy Process (AHP) is employed to quantify the weights of various evaluation indicator, and the final design scheme is determined based on normalized comprehensive assessment values. Finally, this method is applied to the design of a new-generation propulsion system for the Concorde aircraft. The design results indicate that the proposed optimization design and evaluation method effectively meets the requirements of scheme design under multiple evaluation criteria. Compared to the original Concorde propulsion system, the new scheme reduces fuel consumption and takeoff nozzle exit jet velocity by 28.15% and 34.33% while meeting thrust requirement, thereby significantly improving the aircraft’s economy and environmental performance.

Guohe Jiang, Min Chen, Jingmei Cong, Hailong Tang, Jiyuan Zhang
A Design of Civil Aircraft High Frequency Antenna for Laboratory Test

This paper describes a method of designing a civil aircraft high frequency antenna, to meet the external communication requirements in the laboratory. In this paper, to assure the length of antenna is sufficient and to increase the radiation efficiency, a three-wire antenna for laboratory test is designed and selected, and its reliability is verified by modeling simulation analysis. In order to verify whether the performance of the designed antenna meets the requirements of the design index, this paper mainly demonstrates and verifies the performance index through theory and practice. On the one hand, theoretical calculation is made for each performance index, including transmission loss and antenna gain; On the other hand, the actual performance indexes are tested and verified, the modeling simulation test results depict the radiation patterns in the range of high frequency with antenna in various elevation angles. The radiation patterns indicate that in a given communication distance range, the three-wire antenna gain is enough to meet the communication requirements.

Xin Tu, Kaikai Si
2023 Asia-Pacific International Symposium on Aerospace Technology (APISAT 2023) Proceedings
Song Fu
Copyright Year
Springer Nature Singapore
Electronic ISBN
Print ISBN

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