Proceedings of Fluid Mechanics and Fluid Power (FMFP) 2023, Vol. 4

The growth of electrical devices necessitates efficient cooling systems, but the development of cooling fan propellers has lagged due to the coherent dependence on conventional propeller designs. Recent advancements in cooling technology for electric vehicle battery packs involve numerous developments yet cost and space constraints are some of the persistent challenges. Increasing the number of cooling fans leads to excess power consumption and reduced system efficiency. Adjusting the battery pack’s structure can help lower temperature, but large air openings risk debris ingress and require high-quality filters, reducing air density and creating pressure drops. This lowers the mass flow rate through the fans, increasing battery pack temperature and affecting efficiency. This paper aims to focus on the development of propellers with enhanced mass flow rate obtained by implementing different airfoil geometries in the designing of the propeller, analyzing their effect, and proceeding with the performance analysis with an existing design.

The study of particulate matter (PM) emissions, including ultra-fine particles (UFPs), is crucial due to their severe influence on human well-being. The present work focuses on the elementary investigations of diesel flame-combustion by measuring the particulate emissions, with and without the addition of 100 ppm Alumina/Ceria nanoparticles (NPs), using a scanning mobility particle sizer (SMPS). Initial results indicate a decrease in the total number concentration (TNC) of particulate emissions within the size range of 23–711 nm when NPs are added to diesel. However, a detailed analysis reveals an increase in TNC for particulates smaller than 50 nm. This suggests that the NPs evolve during combustion, leading to an elevated number concentration (NC) in the ultra-fine particle region (< 50 nm). The size of NPs also plays a vital role in the improvement of the combustion process and PM emissions. The present study reveals that ball-milled nanofuel samples (NFS) show a better reduction in TNC of PM emissions (18.25% for A100BM, 20.70% for Ce100BM) when compared to bath-sonicated NFS (14.04% for A100BS, 15.09% for Ce100BS). The maximum reduction of 28.07 and 32.28% in PM emission is observed for Alumina-nanofuel and Ceria-nanofuel, respectively, when ball-milling and bath-sonication are combined.

Sodium is used as coolant in Indian fast breeder reactors (FBR’s) to remove the heat generated due to nuclear fission in the reactor core. A quantified sodium flow is envisaged through various flow zones in fuel, blanket and storage flow channels called subassemblies (SA). Reduction of flow in any reactor core SA can decrease the heat transfer and can cause various anomalies in reactor parameters as per their capacity. An independent in situ flow measurement system named as core flow monitoring mechanism (CFMM) is used in prototype fast breeder reactor (PFBR), to measure and ensure the required coolant flow rate through each SA. Eddy current flow meter (ECFM) is used as sensor in CFMM for sodium flow measurement. One CFMM is not capable to reach out all the core SA and hence monitoring the coolant flow rate in all the core SA is not possible. Therefore, two CFMM are used to cover the entire core. The sodium flow rate in fuel SAs (FSA) are measured using CFMM-1 and the coolant flow rates in blanket SA (BSA) and storage SA (SSA) are measured using CFMM-2. The hydraulic testing of CFMM-2 revealed that the sodium velocity at the sensor region ranges from 0.23 to 0.56 m/s. With such a low velocity measurement, it was anticipated that the measurement error using ECFM would be significant. In order to achieve a measurable output, the hydraulic design of CFMM-2 is altered to enhance the velocity at the sensor location. The hydraulic design of CFMM-2 has been optimized using CFD tools and sodium velocity at the sensor region is increased by 105%. The CFD predicted results that are also validated with the 1:1 scale experimental testing using water as simulant.

The current study examines the flow and heat transfer of micropolar fluid in a porous medium. The walls are maintained at two different constant temperatures, and the Brinkman equation has been used for the fluid flow under constant pressure gradient. The governing equation of the problem is solved analytically. The expressions for fluid velocity, micro-rotation and heat transfer, flow rate, wall shear stress, and heat transfer rate have been achieved in its closed form. The effect of various physical parameters on the velocity profile and temperature are represented graphically.

The die is used to get the desired shape during the extrusion of hydrogenic fluid. The extruded rod is cut to get the required length of the pellet and injected in the form of fuel into the fusion reactor. The design of the die is an important preliminary step in the development of the extruder system. Therefore the study of die requires a knowledge of the rheological behavior of hydrogen and its effect on change in pressure and viscous heating. The Polyflow CFD tool from ANSYS has been used to study the characteristics of pressure, local shear rate, and viscous heating at different temperatures of solid hydrogen. In the present investigation, the uniform cross-section die has been simulated at non-isothermal conditions. The results obtained from the CFD analysis have been validated from the literature. The correlation between flow rate and viscous dissipation helps to understand the non-isothermal behaviors of hydrogen. Different contours have been included to know the local changes of pressure and shear rate at minimum and maximum flow rates.

Hydraulic systems are widely used in a variety of industrial applications and are essential for mobile machinery used in the agricultural, construction, and mining sectors. The mobile equipment used in these industries involves hydraulic systems coupled with power actuators that deal with heavy loads and require precise control, reliable operation, and high efficiency to improve productivity, efficiency, and energy-saving. The said controls of the power actuator are achievable by deploying two methods, one by independent metering technology using two proportional directional control valves and the second one by using a digital directional valve. The present article discusses and compares the said two control methodologies using Automation Studio® simulation software. The simulation studies are made for actuator displacement and pressure at different load conditions. It is found that the digital directional valve controlled hydraulic system demonstrates better dynamic performance and control compared to the independent metering control technology. The digital directional valve control ensures that system pressure remains constant regardless of the load variations, which decreases throttle loss and pressure fluctuation in the hydraulic system.

The main objective of this paper is to investigate the effect of atomization quality on the lean blowout (LBO) limits and flame lift-off conditions of a swirl stabilized burner under different air flow operating conditions. Two simplex atomizers of different geometrical parameters are chosen to represent different atomization quality of the injector. Combustion experiments are conducted using Jet-A fuel in the swirl stabilized burner to measure the LBO limits. The atomizer with better atomization quality (K-0.252) shows wider LBO limits at all air flow operating conditions. Flame images are captured at different equivalence ratio (Ф) conditions through the exit of a swirl stabilized burner. Images are processed in RGB format and non-dimensional values of average blue, green and red intensities of the flame images are plotted against equivalence ratios. The average blue intensity initially decreases up to a certain value of equivalence ratio (termed as transition equivalence ratio) and then increases until blowout. After this transition equivalence ratio, significant changes in the colour and features of the flame are observed. This transition equivalence ratio obtained from blue intensity plot is assumed to be the lift-off equivalence ratio of the flame. Atomization quality of burner is found to strongly affect the LBO limits and the lift-off conditions of the flame.

The packed bed thermal energy storage (PBTES) system is a versatile solution for storing solar thermal energy and waste heat at various temperature levels. Enhancing the heat transfer coefficient between the encapsulation material and the heat transfer fluid (HTF) is crucial for improving the system’s thermal performance. This study used stainless steel spherical balls to encapsulate myristic acid as the phase change material (PCM) and water as the HTF. Experimental investigations were conducted on a lab-scale rectangular storage tank, examining three different HTF flow rates (200 LPH, 300 LPH, and 400 LPH) during the charging and discharging phases. The results demonstrated that increasing the flow rate reduced the charging/discharging durations of the PCM, enabling efficient heat energy storage/release within a shorter time. Notably, the cumulative heat stored/released was higher than other HTF flow rates at the 80-minute charging phase and the 105-minute discharging phase for the flow rate of 400 LPH. The PBTES system demonstrated an average energy efficiency of 85.79% and an exergy efficiency of 34.29%. The thermo-hydraulic assessment of this study confirmed that higher HTF flow rates significantly improved the overall performance of the PBTES system.

This work presents a deep learning-based approach to tackle inverse heat conduction problems in one and two dimensions from the available temperature profile and heat flux. The primary objective is to predict the equivalent thermal conductivity of materials in different compositions. Three distinct cases are presented: a uniform thermal conductivity material, a checkerboard pattern with alternating conductivity, and a composite structure comprising dispersed phase and matrix with varying conductivity. A comprehensive noise analysis is conducted on the one-dimensional heat conduction case, wherein input data is subjected to 5%, 10% and 25% noise levels. This analysis explores the model’s robustness and sensitivity to noisy input.

Fluid mechanics plays a crucial role in the design of hydraulic dampers and actuators. These devices are necessary to ensure smooth operation of high speed machines and vehicles. Currently, passive dampers are commonly used due to their cost-effectiveness, but they are less adaptive. On the other hand, active dampers are highly effective as they respond quickly to changes in environmental stimuli but come with a higher price tag. As a result, researchers are investigating semi-active dampers as a viable solution to achieve a balance between affordability and effectiveness in the design of vibration attenuating systems. Magneto rheological (MR) fluid actuators and dampers (semi-active dampers) are used in a number of vehicle dynamic applications. Popular models of MR devices are Bingham and Bouc-Wen which can be integrated in system level vehicle dynamics models. Several approaches have been used to solve these system level models using semi-analytical and numerical methods. This article explores traditional model based approaches to characterize magneto rheological devices. Comparison of different numerical methods for dynamic response is investigated in this article.

The break-up of a liquid fuel jet is mainly dependent upon the properties of the fuel, its injection velocity and the properties of gases surrounding the nozzle. The disintegration process depends upon surface tension at the liquid–gas interface, liquid density, the liquid's dynamic viscosity, and the nozzle hole diameter. Analysis of fuel jet breakup quality is based on breakup length, jet structure, droplet size, breakup frequency and spray angle. Based upon this qualitative and quantitative analysis, the suitability of different fuels in different applications is finalized. For this purpose, in the present work, nozzle system performance is assessed while considering tangible and intangible factors. A GTA-based model is developed that represents the fuel jet and its break-up process. The nodes and edges of the digraph represent interactions of the fuel jet parameters. Matrix representation is appropriate for considering factor interdependence. System complexity is no less than any other system, therefore, computational techniques are necessary for saving time and cost. A computer program in ‘R’ has been developed to solve the problem. Results are reasonably appropriate for comparing the quality of jet formation in different engineering systems. Based on the graph-based analysis findings, design recommendations or modifications are proposed for fuel injection systems to improve fuel jet break-up efficiency, reduce fuel consumption, and minimize emissions.

In liquid rocket engines, cavitating venturi is used as flow control device which meters the constant flow rate at fixed inlet pressure under varying back pressure conditions. Cavitating venturi is used mainly in two configurations, fixed area cavitating venturi and variable area cavitating venturi. The use of fixed area cavitating venturi is more prominent in propellant feed lines of fixed thrust engines as well as that of test facility. In case of throttling engines, where a proper flow control is needed at different thrust level, variable area cavitating venturi is preferred. The present work investigates the cold flow characterization of a variable area cavitating venturi designed for 1000N MMH-N2O4 based Throttleable Pintle engine. The flow controlling area for the cavitating venturi was varied using a needle by mechanical means. Experiments were carried out using water as simulant fluid. Effect of back pressure on flow characteristics was studied at different stroke lengths of the moving needle at fixed inlet pressure. In addition, effect of varying inlet pressure on flow characteristics was also studied at a fixed stroke length of the moving needle.

Tilting pad thrust bearings are mechanical components commonly used to support axial loads in rotating machinery. They consist of several pads that tilt to accommodate the changing load direction. Double-acting thrust bearings are a specific type of thrust bearing designed to carry bidirectional axial loads. Unlike single-acting thrust bearings, which can support loads in only one direction, double-acting thrust bearings are capable of accommodating axial forces in both the forward and reverse directions. This characteristic makes them ideal for applications where the direction of axial loads may change frequently. In the present study, a numerical estimation of load-carrying capacity, axial stiffness, and angular stiffness of a double-acting thrust bearing is performed. Axial stiffness refers to the ability of the bearing to resist displacement under an applied axial load. Angular stiffness refers to the amount of restoring moment provided by the bearing pads when a bearing is subjected to a certain amount of journal inclination. The impact of pivot film thicknesses on the bearing load-carrying capacity, axial stiffness, and angular stiffness is also studied.

The One Way Flow Restrictor (OWFR) is one of its kind passive device that restricts the fluid flow in reverse direction compared to its forward direction. When installed in piping system and operating flow is in reverse direction, the OWFR will reduce the rate of loss of inventory to prevent the severe consequences like system overheating, faster depressurization etc. Comparative much less restriction in forward direction maintains the normal operation of overall system almost same. Towards this requirement, a 6-inch size OWFR development work has been initiated. A conceptual design of OWFR has been derived using form drag concept of restriction. The CFD analysis was carried out for pressure, velocity, particle path profiles both in forward and reverse direction. The designed OWFR was fabricated and its flow characteristics has been measured experimentally. This paper describes the design concept, numerical analysis by CFD, fabrication, experimentations and results of designed 6-inch OWFR. The results of CFD have also been validated against experiment and a comparative analysis of experimental and CFD data is also described here.

The present work focuses on the combustion performance of a premixed methane-air mixture with hydrogen and steam addition in micro-combustors with isothermal walls at 300 K. The reaction of the premixed flame under varying operating conditions is analyzed in terms of the centerline temperatures, flame temperatures, maximum heat of reaction in the vicinity of the reactive front, and the mass fraction of various species involved in the combustion process. The interactions between flame position, temperature, and species concentrations caused in the micro-combustor for 10% and 20% hydrogen addition ratios are studied using the ANSYS Fluent solver. The simulation results depict that hydrogen addition significantly escalates the reaction rate, flammability range, and flame stability, increasing the OH mole concentration and reducing the ignition time. An increase in the hydrogen addition ratio causes the flame position to gradually shift toward the combustor inlet, with the flame temperature increasing steadily by about 3.5% for every 10% hydrogen addition. However, this can be countered by adding steam to the incoming mixture, which helps to push the flame to its original location. The steam amount required to reinstate the flame to its original position corresponding to the two hydrogen percentages has been determined.

Impeller exit area is an important design parameter that influences pump performance characteristics. In this study, to achieve steeper H-Q characteristics and a safer power curve, a new impeller has been designed with reduced area ratio. The numerical analysis, using commercial ANSYS CFX software, has been performed with the old and the new modified impeller on the same casing by keeping the volute geometry, throat area and suction development unaltered. In order to reduce the area ratio, we have reduced the impeller exit area by decreasing impeller width and blade outlet angle. To validate the simulation result, an experiment has been conducted in the pump test laboratory with the two impellers. We have observed that the H-Q characteristic becomes steeper with the decrease in the area ratio. The peak efficiency remains unchanged, however, the BEP shifts toward the lower flow rate. The P-Q curve becomes non-overloading and flat. We have also introduced a steepness factor Ku which can be used in future research work.

Hydro power utilizing low head and ultra-low head is an area that can be harnessed as a potential source of renewable energy. Technologies proposed to harness this area were a subject of scrutiny as the flow dynamics and economics of the project were quite challenging. Various hydro turbine technologies developed to cater to this area are ample proof of the research and development activities that are rampant in this field worldwide. Also, these technologies were highly capital-intensive and technology-driven. This area can now be economically developed using ingenious hydropower screw technology. With a footfall of more than 25 units installed and commissioned in India alone by both government and private developers, hydropower screw technology has craved a market for itself. The paper discusses the need for wide-spread adoption of hydropower screws for low-head and ultra-low-head hydropower development in India. Also, salient features of the hydropower screw installed in India at various locations and the results of the performance guarantee test carried out at different project locations are discussed in detail.

This article deals with the development of an energy regenerative technology by incorporating an accumulator in the conventional swing drive system of a hydraulic excavator used for mining operations. The accumulator incorporated in the proposed energy regenerative swing system stores the waste energy released during the turntable (superstructure) swing motion of the excavator. The energy stored in the accumulator is used to propel the swing hydromotor along with the main hydraulic pump in the next cycle of the excavator’s swing motion. For the analysis of the proposed system, the detailed simulation model is made in the MATLAB®/Simulink environment. The performance analysis of the proposed swing system is compared with the conventional swing system through simulation. It is observed that the energy saved by the proposed system incorporating an accumulator is 17.79% of the energy consumed by the hydraulic pump of a conventional swing system.

The present research includes a comprehensive computational fluid dynamics (CFD) investigation to enhance the scramjet combustor performance. Although scramjet propulsion systems have a lot of potential for use in hypersonic flight, they face substantial technological difficulties when operating effectively at supersonic speeds. The present study’s main objective is to analyse a dual-strut and cavity-based model of a scramjet combustor in order to boost its effectiveness. To analyse the intricate flow and combustion processes that occur inside the scramjet combustor, the study employs a high-fidelity CFD technique. To precisely depict the complicated features of supersonic combustion, a two-dimensional, compressible Reynolds averaged Navier-Stokes solver with turbulence modelling is used. By including the struts and cavities in the design, various modifications are made to the standard DLR model, and the flow is then analysed. In the current simulations, the air velocity at the strut and species fraction at the outlet of the combustor are primarily observed, which aids in understanding of the mixing time and combustion efficiency of the combustor. The dual strut with cavity creates the recirculation region that could enhance the fuel air mixing of the combustor. The distribution of hydrogen in the lateral direction of the flow is improved by the shock wave interaction from the cavity compared to the baseline strut design. The findings of the present study advance our understanding of scramjet combustor performance and offer insightful information for upcoming design advancements.

Cryogenic rocket engines offer the highest specific impulse among liquid rocket engines, making them a crucial component of space missions. Cryogenic engines are mostly used in the upper stage of the rocket. Maintaining precise control over the Mixture Ratio (MR) in liquid rocket engine is vital, and it is achieved by bypassing a portion of the liquid oxygen (LOX) from the pump's delivery side to its suction side. However, this MRC bypass flow mixing results in non-uniform temperature at the pump inlet, which may get further aggravated in the pump leading to non-uniform temperature at the thrust chamber injector inlet. This non-uniform injection temperature may cause combustion related problems. This paper presents a comprehensive computational fluid dynamics (CFD) study conducted to investigate the flow characteristics in two distinct cases: Constant pump inlet temperature flow (Case 1) and Maximum MRC bypass flow condition (Case 2). In Case 2, the pump inlet temperature variation of 3.2 K decreased to 2.1 K at the pump delivery and further mixed in the downstream elbow, resulting in a temperature variation of 0.4 K only. On the other hand, in Case 1, the constant pump inlet temperature flow exhibited a non-uniformity of temperature of approximately 1.9 K at pump outlet, which diminished significantly to an order of 0.1 K in the downstream line. The pump performance (headrise and efficiency) obtained from CFD closely matches with performance of pump during the hot test.

Propellers are a key component used in the propulsion of aircrafts, drones, etc. to generate lift or thrust. The propeller design for the use in unmanned aerial vehicles (UAVs) such as drones plays major role in their performance. Based on the requirements for such a typical UAV application, a propeller design has been attempted. The paper deals with designing a propeller based on classical blade element theory and varying the related parameters to achieve satisfactory aerodynamic characteristics, as per the requirements. Sensitivity studies for the design optimisation have been done through CFD analysis, followed by the propeller fabrication through additive manufacturing route and tests in still air with electric motor drive.

We explored the fragmentation behavior of Carbopol-water-based gel simulants at different Carbopol wt.% concentrations, and breakup morphologies are compared against the breakup of Newtonian fluids such as deionized water (DI). It is observed that increased Carbopol concentration affects the breakup events and delays the initiation and breakup phases. As the bag inflates, inhomogeneity appears at the bag interface, causing the bag to rupture early compared to DI water due to the Marangoni effect. DI water and Carbopol 0.05 wt.% (S-I) sample show rising cross-stream deformation, but Carbopol 0.1 wt.% (S-II) has nearly constant growth from initiation to the bag rupture period. Hence, child droplets from rim breakup have significantly higher volumes than DI water ones.

The exploration of hydrokinetic energy has received significant attention in recent years. The cross-flow turbine-based Savonius rotor is popular for its excellent starting capability and moderate conversion efficiency. The present work numerically investigates the assessment of hydrokinetic energy utilization by deploying the circular deflectors upstream of Savonius rotor placement. The results have also been compared to without deflector-augmented Savonius rotor. Two positions (equispaced) in the upstream and downstream sides of the placement of the turbine are selected. The results demonstrate the variations of the kinetic energy at different angular positions. It is also observed that the deflector-augmented Savonius rotor is about 179.01 and 40.65% more effective in energy utilization in the vicinity (X3–X2) and far-field (X4–X1) locations, respectively, compared to without deflector Savonius rotor. Further, the gain in the hydrokinetic energy for circular deflector-assisted Savonius rotor is more due to guided flow and backward drag force reduction on the returning side blade.

The hydrodynamic near-field and acoustic far-field characteristics of an unheated Mach 0.5 jet manipulated using steady fluidic injection are experimentally investigated. The fluidic injection is introduced via two injectors placed diametrically opposite in the upstream direction, injecting air normal to the main jet. Extensive measurements are performed on the natural and manipulated jets. The present study shows a significant reduction in turbulent intensities and overall sound pressure levels for the manipulated jets.

This work is to present the design and development of a vertical static thrust bed (VTSB) for solid propellant rocket motors. The setup consists of a motor mount, load cell holder, amplifier, and load cell to measure the impulse and to know the rocket thrust with different classes of rocket motors ranging from A class to F class, different nozzles, and new kinds of fuel for amateur rockets. This vertical test bed was designed and assembled in Autodesk Fusion360®. The thrust bed was tested using a KNSU rocket motor. The results of thrust and total impulse values are comparable to the literature. The testbed is safe to demonstrate and the results obtained are satisfactory. The test stand can be used for the motors with specific impulse up to 100 N s.

This present work investigates the external aerodynamics of a lean-burn gas turbine fuel-flexible injector using particle image velocimetry (PIV) experiments. The complex aerodynamics of the injector is studied to obtain the velocity flow fields generated by the main and pilot swirler sections of the injector and to capture the central toroidal recirculation zone (CTRZ) at the injector exit. The fuel flex injector assembly consists of a pilot and main mixer. The pilot mixer consists of primary and secondary swirlers arranged co-axially in clockwise and counter-clockwise directions. The main mixer consists of three swirlers in which the primary swirler of the main mixer is arranged co-axially with pilot mixer while the secondary and tertiary swirlers of the main mixer are arranged radially. The efficient CTRZ is achieved through optimized swirlers in the geometry. The velocity flow field is visualized on different flow rates using low-speed PIV for the pilot, main, and full injectors separately. A symmetric and small CTRZ is observed at the exit of the pilot mixer. Similarly, a symmetric and larger CTRZ is observed at the exit of main mixer. A combined and bigger CTRZ with a strong shear layer is observed at the exit of the full injector.

In this article, detailed design and manufacturing processes/materials are presented for the prototyping of a cost-effective open-circuit wind tunnel. Students and educators can use it to enhance their understanding of aerodynamics concepts by enabling them to perform a variety of experiments, such as flow visualization, drag, and lift measurements, and boundary layer studies. The design of the settling chamber, contraction cone, test section, and diffuser are based on empirical parameters suggested by the literature available in this domain. Fabrication was done by using materials and components easily available locally. The final prototype of the wind tunnel is tested and calibrated to ensure accurate and reliable measurements. To validate the performance of the wind tunnel, a series of experiments were conducted, comparing the obtained results with established theoretical models and existing data. The affordability and accessibility of the wind tunnel make it particularly suitable for educational institutions with limited resources.

Effectiveness of ground heat exchanger is ruled by the prevailing thermal resistances. Using serrated surface helps in curtailing the fluid side thermal resistances. In the present study, a 3-D numerical analysis has been carried out to determine an improved design of circular tubes with longitudinal serrations for minimization of the thermal resistance caused by the pipe surfaces. As the geometry of serrations is an important design parameter, for such purpose, the thermo-hydraulic performance of various serrations is assessed. For the considered geometries of the serrations, the thermal and flow parameters viz. pipe length, pipe diameter, inlet temperature, wall temperatures, and Reynolds number are kept same for all the cases. The results indicated that the deployment of triangular or rectangular fins is a promising method for augmentation of heat transfer. The maximum percentage change in the thermal conductance is found to be 423 and 448% for triangular and rectangular fins, respectively, for minimum pitch value (1/30) and maximum height (1/15). It is also noticed that the fin height and pitch should be chosen carefully as the system becomes inefficient for lower fin height (1/30) and higher pitch (1/5) values.

A numerical study is conducted on the jet impingement in rectangular and curved channels with and without crossflow to comprehend the flow mechanics and heat transfer characteristics. In most of the practical scenarios, jet impingement is accompanied by crossflow. The crossflow generally reduces the jet’s mean velocity length and displaces the geometric jet impinging point in the downstream direction. The influence of jet Reynolds number (Re) 7500 and the velocity ratio of crossflow and jet flow (M) 0, 0.19 and 0.25 are varied to study the flow distribution and heat transfer characteristics on the target wall surface. The heat transfer is higher for rectangular channels than curved channels for M = 0. The maximum Nusselt number (Nu) decreases for both channels while increasing M from 0.19 to 0.25. In the rectangular and curved channels, the maximum local Nu is reduced by 22.5% and 14.8%, with an increase in M from 0.19 to 0.25, respectively.

Optical visualisation techniques such as shadowgraph and Schlieren are commonly employed to study shockwave characteristics in supersonic free jets, to conduct qualitative as well as quantitative analysis. Typically, high-speed cameras are used to capture images with clearly visible shockwaves. The lower-cost cameras with lower frames per second (fps) do not yield satisfactory results. Therefore, there is a need to develop an algorithm capable of reducing image noise and enhancing the images from a low fps camera to enable better observation of shockwaves. In this study, a supersonic free jet exiting a CD nozzle with design Mach number 1.6 was visualised using the Schlieren method. Images were captured using a camera operating at 7 fps and processed using a MATLAB algorithm to reduce noise and bring out well-defined shockwave structures. The algorithm employed these series of steps: time averaging of images with shockwaves and images of the background, conversion of images to grayscale, application of a frequency-domain filter, and subtraction of the background image from the supersonic jet image. Qualitative analysis was performed on the processed images that revealed prominent features such as the shock cells, vortices generated by chevrons, and the Mach disc in highly overexpanded jets. Quantitative analysis was also done to measure shock angle and Mach stem length. Additionally, image processing brought out the previously unseen shear layer in the original images. This algorithm holds potential for cost reduction in optical visualisation experiments by eliminating the requirement for a high fps camera to achieve reliable qualitative analysis.

The increasing global energy demand has prompted significant technological advancements in underground mining operations. As the underground working areas expand, workers may encounter the need to travel considerable distances to reach the work face, resulting in a significant waste of time and energy. To address this issue, a man riding system offers a safe and comfortable solution for transport people along long deep incline mines. By using this system, workers can save considerable time and energy during their commute, which ultimately boosts productivity and enhances the profitability of mining operations. Installation of a man riding system in any mine depends on various parameters such as its geographical condition, man and material handling capacity, installation cost, etc. Its proper selection of man riding system needed to be done to increase its effectiveness and efficiency of that mine. In this paper, various types of man riding systems installed in different underground coal mines are studied based on the data collected from the mines. This will help analyse its performance and conclude its effectiveness under varying parameters such as speed, time duration, installation length, carrying capacity, etc. The mentioned study will be valuable in facilitating the appropriate selection and efficient utilisation of a man riding system (MRS) for an underground mining operation.

Aerodynamic performance of a turbine stage is influenced by the losses occurring within individual turbine blade rows. Total pressure losses within a turbine stage are classified into primary, secondary and annular wall losses. Primary losses are further divided into losses due to shocks and momentum deficit. In turbomachinery design, it is a standard methodology to discretize blades of stator and rotor rows into several airfoil sections during their respective blade design process. The aim of the present paper is to put forth the airfoil redesign methodology adopted in arriving at an improved airfoil of mean section of a baseline axial turbine Nozzle Guide Vane of an existing low-pressure turbine stage at the Versatile Turbine Test Rig (VTTR) at Propulsion Division, CSIR-NAL. Baseline airfoil is characterized for aerodynamic performance using RANS CFD simulation and flow field is analyzed in detail. Details of the numerical setup, grid dependence and turbulence model are furnished in the paper. It is observed that high flow accelerations over the suction surface are causing an early and drastic rise in loss at onset of transonic flow. Sensitivity study of Unguided turning (UGT) and Trailing Edge Wedge Angle (TEW) is carried out using 2D CFD to generate a population of airfoils and shortlist Six airfoil designs for detailed 3D CFD analysis. It is found that use of a flat back suction surface with a suitable combination of trailing edge wedge angle. The redesigned airfoil referred to as “Profile 5” in the study achieves a reduction of loss by around 40% compared to that of baseline airfoil at the design point condition of Exit Mach Number M = 1.

Comprehensive numerical investigation focused on the thermal and emission characteristics of a multi-tube inverse diffusion flame (IDF) using methane as the fuel and air as the oxidizer is performed. The multi-tube IDF configuration comprises a variable number of coaxial air and fuel tubes, ranging from 4 to 9, with one central tube and the others arranged circumferentially. The study employs the k-ε turbulence model and the Probability Density Function (PDF) approach for combustion modeling. The research emphasizes the comparison of maximum temperature, carbon monoxide (CO) and nitrogen oxides (NOx) emissions, and methane (CH4) mole fraction between the conventional IDF and the multi-tube IDF configurations. It is demonstrated that the number of tubes plays a pivotal role in shaping the flow physics and temperature characteristics of these flames. Flame height calculations for all burner geometries are based on the CO fraction at the flame’s centerline. Since CO is mostly generated in the final stages of the multi-step chemical reaction involving methane, it is a suitable indicator to use for determining flame height. Multi-tube geometries are found to enhance flame temperature due to increased mixing within the flame region. Furthermore, the multi-tube IDF configuration exhibits the lowest NOx emissions. The findings provide valuable insights into optimizing combustion processes for enhanced efficiency and reduced emissions in industrial applications.

Internal combustion engines have been in use for about two centuries. The fuel efficiency of conventional compression ignition engine is superior to conventional spark ignition engine. The diesel-fueled compression engine is meeting the requirement of prime mover in applications. The diesel engines have undergone multitude of design modifications. Diesel-fueled engines’ particulate and oxides of nitrogen (NOx) emissions are high. Of late, research community is perplexed with the tackling of fuel efficiency and lower exhaust emissions. Low-temperature combustion has shown promising results with lower emissions and better efficiency. Reactivity-controlled compression ignition engine has shown promising results to continue for the sustenance of combustion engines. The new concept engine operates with two types of fuel: low reactivity and high reactivity fuels. With proper fuel selection, this concept could facilitate the use of renewable energy sources. Numerical simulations with ANSYS-Forte using hydrogen, as low reactivity fuel, in varying proportions along with petrodiesel as high reactivity fuel. For a chosen engine configuration, pressure-crank and heat release rate diagrams along with NOx and carbon monoxide (CO) emissions have been predicted. The results indicated that with increase in amount, both rate of heat release and NOx emissions increased, whereas CO emissions decreased.

This project delves into the realm of heat exchangers and passive heat enhancement techniques. Heat exchangers are critical components in various industries, facilitating efficient thermal energy transfer. Passive techniques, such as twisted tape inserts, offer innovative ways to bolster their performance. Using a validated model in ANSYS software, we conducted a comprehensive analysis of heat exchanger efficiency, taking a stepwise approach. We initiated our study by examining the baseline heat exchanger, devoid of any enhancements, followed by the introduction of twisted tape inserts. We progressively increased the twists from 2 to 4 and integrated hole patterns. The outcomes were striking, showcasing a significant 13.104 K reduction in hot water outlet temperature with the implementation of twisted tape and holes. Furthermore, the performance of the heat exchanger increased by 3.96% with these heat enhancement techniques. These results emphasize the efficacy of inventive enhancements in optimizing heat exchanger designs, promising energy conservation, and heightened system performance within industrial heat transfer processes.

Wind turbine wake models that estimate the evolution of the velocity deficit are essential for designing optimal wind farms. A key component of these models is the wake growth rate. We analyze the performance of a recently proposed analytical wake growth rate model and for the streamwise velocity deficit behind an isolated turbine. We consider conditions with different vertical velocity gradients (VVGs) while keeping the streamwise average velocity and ambient streamwise turbulence intensity at the turbine hub height the same across cases. This is done by changing the aerodynamic roughness, friction velocity, and turbine hub height. Comparisons between the predictions of the model and LES data show that the model performance is better for cases with lower VVG. It was also found that the model predicts lateral/spanwise wake widths better than the vertical wake widths.

To analyze the drying characteristics of Jamun (Indian Blackberry) slices experimentally, the experimentations have been conducted on a small-scale convective hot air dryer available at Energy Section, Sardar Patel Renewable Energy Research Institute, Anand, Gujarat, India. Convective drying characteristics for Jamun slices were analyzed at 60–80 °C air drying temperatures with an interval of 10 °C with air velocity (1 and 1.5 m/s). The sample’s initial moisture content has been found using a hot air oven available at the Chemistry Laboratory, A. D. Patel Institute of Technology, Anand, Gujarat, India. During the drying investigation, it was found that it occurred only in a range of falling periods of drying. Air temperature plays a very important role in drying. Air velocity also shows a significant effect in the drying rate and drying time. Moisture removal took place from initially at 83.68 (% wb) to finally around 4 (% wb) in the tray dryer. The experimental results were verified with various theoretical results published by previous researchers.

Ventilation is an essential component of underground mining, as it helps maintain the safety and health of miners. Consequently production and work efficiency can be enhanced. The principal purpose of the ventilation system is to regulate the quantity and quality of fresh air while eliminating hazardous gases. With the intention of increasing the energy efficacy of an axial flow fan, this study investigates the design aspects of mine ventilation fans. A three-dimensional model of the fan was developed based on the dimensions of the fan were estimated using a one-dimensional technique. A 3D model of an axial fan and a CFD analysis of its performance are investigated for underground mining ventilation application. Several cases have been studied, leading to the conclusion that the forced axial ventilation fan case, characterized by a Solidity value of 1.6, is deemed suitable for further investigation. The CFD analysis demonstrates that the forced axial flow mining fan has been designed to effectively discharge a volumetric flow rate of 47.13 m3/s of air, while operating at a rotational speed of 600 revolutions per minute. It achieves a significant static pressure rise of 838 Pascals across the rotor while consuming 48 kW of power.

The aim of the present work is to study the effect of notches on the performance of the Savonius turbine. Here experiments are carried out for three different configurations of the rotor blade like conventional semi-circular blade, Semi-circular blade with hollow notches on retarding side of the blade, and Semi-circular blade with solid notches on retarding side of the blade. The experiments are carried out in small laboratory canal with 60 cm width, 88.5 cm water depth, and 10 Hp submersible pump. The performance of the turbine is measured in terms of torque, coefficient of torque, power, and coefficient of power. During the study it is found that maximum coefficient of power output of the rotor is 0.107 which is same for conventional rotor and rotor with hollow notches while angular velocity of the rotor with hollow notches is 13.72% higher than that of the conventional rotor and 22.68% higher than that of the rotor with solid notches.

This study explores the impact of burner outlet size on the behavior of a swirl burner with three nozzles. Our motivation stems from the need to understand how altering the burner’s hydraulic diameter affects combustion characteristics. The outlet hydraulic diameters ( $$D_h$$ D h ) were 5, 10, and 15 mm, and the bluff body diameter (BBD) was 10 mm. An unconfined premixed n-butane air mixture was tested using PIV at an equivalence ratio of 1, a pressure of 1 bar, a temperature of 300K, a Reynolds number of 4000, and a swirl intensity of S1.5. The findings show that the burner outlet expansion pushed the forward stagnation point upstream. The recirculation length and width suddenly doubled for the $$D_h$$ D h = 10 mm case and were almost constant for bigger outlet hydraulic diameters. Particle image velocimetry showed that the $$D_h$$ D h = 5 mm case had the highest Turbulent Kinetic Energy, resulting in higher stretch rates and vorticity. Under identical mixing conditions, the three flames have very different turbulence. CH* chemiluminescence showed that burner outlet size increased reaction rate. Due to the increased stretch rate and local flame extinction, exhaust gas analysis showed that the C $$_x$$ x H $$_y$$ y concentration was higher for the D $$_h$$ h =5 mm case and lowered with increasing burner outlet size. Entrainment increased for burner outlet hydraulic diameters of 5, 10, and 15 mm. Damkohler numbers under different cases reveal the flame’s internal categorization. The flame structure changed from thin to corrugated flamelets as the burner’s hydraulic diameter increased. This study underscores the complex relationship between burner outlet dimensions and flame dynamics, providing valuable insights into how flames are categorized under different circumstances. These findings carry significant importance for the optimization of combustion processes and the enhancement of efficiency in practical applications.

Tube-in-tube heat exchangers are extensively used in various industrial applications due to their compact design and ease of maintenance. However, the growing need to augment their thermal performance leads to the implementation of different fins on the tube surface. This study aims to numerically investigate the potential utilization of helical fins to enhance the thermal performance and capacity of the heat exchangers. The effect of varying fin pitch and helix angle is systematically analyzed for two different fin shapes, i.e., triangle and rectangle. The fin height and operating parameters are kept same for all the designs. The results highlighted a noteworthy improvement in the thermal conductance with the incorporation of fins on the tube surface. The use of helical fins provided an additional augmentation in compared to straight fins as the thermal conductance increases alongside the increase in helix angle. Specifically, the triangle fin geometry demonstrates a peak improvement of 548%, whereas the rectangle fin design exhibits an even more notable boost of 560% in the thermal conductance with a helix angle of 10°. Moreover, the study reveals that an increase in fin pitch results in a decline in thermal performance.

Thermal management of lithium-ion battery packs is very critical for safe operation and longer battery life. The heat generation from a battery cell is a function of ambient temperature, depth of discharge (DOD), and charge/discharge rates. It is very crucial to accurately predict the heat generation rate and in turn cell temperature at various operating conditions. In the present work, heat generation rate and temperature for a 20Ah lithium-ion battery cell are predicted using an electrochemical model based on NTGK formulation. The battery pack consists of two cells sandwiched between three liquid cooling plates. The cooling plates consist of three liquid cooling channels each of 3 × 4 mm cross-section. The thermal performance of the pack is evaluated for multiple operating conditions. The parametric study is aimed to achieve the max cell temperature of <  = 42 °C and max temperature difference (across the cells) of <  = 5 °C. The C-rates varied between 1 and 5C and the ambient (and coolant inlet) temperature varied between 25 and 40 °C (as per normal Indian climatic conditions). The coolant velocity required to keep max temperature below 42 °C is evaluated. Except for max C-rate and max ambient temperature used here, it was possible to achieve the target by varying the coolant flow rate from 0.01 to 0.10 m/s. An operational matrix showing the required coolant flow rate for different operating conditions is prepared.

The present study aims to experimentally investigate the stability limit of lean premixed CNG/air mixture flames in a laboratory-scale swirl stabilized combustor with different bluff body shapes for two cases of air mass flow rates. Four different bluff body shapes, having tapered profiles and circular surface area are employed for the current study. These bluff bodies have different area ratios (0%, 16%, 40% and 60%) and are named as B00, B16, B40 and B60, respectively. Tapered profile of these bluff bodies ensures smooth flow around them without flow separation. Results show that the lean blowout limits slightly improve for the bluff body with a higher area ratio than the bluff body with a lower area ratio. The reason for this behavior is supposed to be the creation of an additional small recirculation zone in the wake of the bluff body, which results in additional flame stability along with the flame stability provided by the inner recirculation zone (IRZ) created by an expanding swirl flow. Flame flashback is also not observed within the operational range of the combustor.

The present study experimentally investigates the impact dynamics of water drops on a superhydrophobic surface (SHS). The study delves into creating SHSs that replicate the water-repellent properties of lotus leaves, employing a simple method for surface preparation. The current procedure involves utilizing spray coating techniques with a commercially available hydrophobic solution NeverWet. The current research focuses on exploring the behavior of impacting water drops on an overhead projected sheet surface treated with NeverWet. The key features of drop impact dynamics, maximum spreading and rebounding dynamics, on the prepared SHS are compared against those exhibited by other SHSs documented in existing literature.

This research centers on an experimental exploration of the atomization performance of both swirl and non-swirl twin-fluid injectors, with an emphasis on enhanced atomization at higher liquid flow rates. In these injectors’ design, atomization is achieved by introducing a substantial volume of air onto a liquid jet within the injector. In the context of swirl-type injectors, the air is introduced through tangential holes into an annular passage, fostering a dynamic interplay. Measurements of size and velocity are meticulously obtained using a precise 2-D Phase Doppler Particle Analyzer system. A significant finding emerged that the Sauter mean diameter of droplets is comparatively lower in the swirl injector in contrast to the non-swirl injector, attributed to the integration of tangential momentum. Meanwhile, the mean droplet velocity remains consistently stable for both injector types. The results suggest that the swirl injector exhibits comparable better atomization characteristics to the non-swirl injector, even when faced with the limitations of a constrained spray angle.

Study is carried out on the low head axial flow turbine (AFT) with aim to utilize the available head efficiently. This focuses on influence of fillet radius at the trailing edge of the runner blade, and the stimulations were carried out for various loads under a constant low head condition. Different models were created in SOLIDWORKS with different fillet radii, i.e. 0 mm, 2 mm, 4 mm, 6 mm, and 8 mm, and stimulated in Ansys Fluent. The results are presented in the form of obtained efficiency ( $$\eta$$ η ) for corresponding fillet radius (Rtu) and rotor velocity plotted against their equivalent non-dimensional terms of Fillet Radius Ratio (FRR) for different Tip Speed Ratio (TSR). The results indicate that for the given head 0 mm, fillet is the most efficient with maximum efficiency of 56.63% and its performance decreases slowly with fillet radius with efficiency of 55.77% at fillet radius 8 mm.

Combustion of hydrocarbon fuels has been a major source of energy for many industries, including transportation, power generation, and heating. However, their combustion is associated with the emission of pollutants such as NO $$_\text {x}$$ x , CO, unburned hydrocarbons, and soot, which can have detrimental impacts on the environment. In recent studies, Peripheral Vortex Reverse Flow (PVRF) and Stagnation Point Reverse Flow (SPRF) combustors have been demonstrated to result in low pollutant emissions. In these reverse flow combustors, the flow reverses to emit on the same side as the air/fuel injection port, with the PVRF combustor consisting of a single exhaust that generates a strong peripheral vortex inside the combustor, while the SPRF combustor has two exhaust ports that form recirculation from both sides. This study investigates the performance of Compressed Natural Gas (CNG) fueled PVRF and SPRF combustors, each operating at a heat load of 6.25 kW, in premixed and non-premixed modes. The experiments were conducted to measure NO $$_\text {x}$$ x and CO emissions within global operational limits, as well as to identify reaction zones through CH* chemiluminescence imaging. Numerical simulations were carried out using RANS with global chemical kinetic mechanisms to estimate flow dynamics and gas recirculation patterns. Very low emission levels, less than or equal to 5 ppm of NO $$_\text {x}$$ x at an equivalence ratio of 0.6, were observed for both SPRF and PVRF combustors in both non-premixed and premixed modes. The trends for NO $$_\text {x}$$ x and CO concerning the equivalence ratio were also similar for both PVRF and SPRF combustors. Notably, the PVRF combustor exhibited slightly lower NO $$_\text {x}$$ x emissions in the non-premixed mode compared to the premixed mode. The numerical simulations found a higher recirculation ratio for the PVRF combustor compared to the SPRF combustor. Additionally, the location of the reaction zone exhibited significant variation between premixed and non-premixed modes for both combustors.

Thermoacoustic instability (TAI) is an undesirable phenomenon that can lead to sizeable structural vibration, noise pollution, and failure of the power systems. Therefore, it is required to understand the mechanism of TAI to predict and control it. In this study, to analyze the TAI, a two-dimensional (2D) computational fluid dynamics method has been developed for the vertical Rijke using Unsteady Reynolds averaged numerical simulation. To trigger the thermoacoustic instability, a trigger has been applied at the inlet boundary of the Rijke tube for a small duration (impulse time) using a user-defined function (UDF). The results have been observed to be in good agreement with published data. The effect of impulsive time of trigger on TAI has been analyzed. The limit cycle amplitude and frequency have been observed. The phase differences between the oscillation of pressure, velocity, and heat release have been calculated and they satisfy the Rayleigh criterion. The Rayleigh index and sound level in decibels have been calculated.

This study employs numerical simulations to investigate the effectiveness of mist film cooling on a flat plate, a critical aspect of advanced cooling techniques. The analysis focuses on several key parameters, including the momentum flux ratio (MR) with values of 0.32 and 0.87, mist concentration ranging from 2 to 10%, and turbulent intensities of 3, 10, and 20%. The simulations are conducted using the established k-epsilon turbulence model. The primary objective is to evaluate the lateral average effectiveness and area average film cooling effectiveness of mist on the flat plate. By systematically varying turbulent intensity, momentum flux, and mist concentration within the cooling air, the study provides valuable insights into the complex interplay of these factors and their impact on optimizing mist film cooling strategies for turbine engine applications. This investigation contributes to a deeper comprehension of the intricate dynamics involved in mist film cooling, thereby yielding pragmatic insights for refining cooling methodologies across diverse engineering contexts.

This study employs computational simulations to investigate film cooling using fan-shaped injection holes, with a focus on analyzing the distribution of turbulent kinetic energy (TKE) over a flat surface. The research utilizes the $$k-\epsilon $$ k - ϵ turbulence model to examine the impact of cooling fluid velocity at the injector exit on TKE and film cooling effectiveness at blowing ratios of 1.0, 1.4, and 2.0. The results demonstrate that increasing the outlet velocity enhances coolant dispersion and improves cooling effectiveness, particularly up to a blowing ratio of 1.4. Visualization of TKE highlights significant turbulence and thorough mixing between the coolant jet and mainstream gas. This study offers significant findings in optimizing outlet injection velocity and TKE distribution, thereby enhancing film cooling performance through diffuser-type injection. Given the practical implementation of fan-shaped injection holes in turbine engines, a comprehensive TKE analysis for cooling turbine components becomes crucial. Understanding the optimal outlet velocity and TKE distribution holds substantial significance in developing efficient cooling strategies for gas turbine applications. The implications of this research extend to various domains, including thermal management, electronics cooling, and power generation systems, all of which can benefit from improved cooling approaches. Notably, our study reveals that a 40% increase in blowing ratio could result in a 100% increase in TKE, facilitating the mixing of coolant gas with hot gas.

This study presents a groundbreaking conceptual innovation of a fan-shaped twin-fluid injector meticulously conceptualized and developed. A thorough performance assessment of the injector is being executed, employing water and compressed air as working substances. Measurements of droplet size and velocity are being carried out through the phase Doppler particle analyzer system, encompassing heightened feed flow rates and a range of airflow conditions. Moreover, an exhaustive exploration of spray spread dynamics is underway across three distinct impactor positions using high-speed imaging. Notably, at a moderate air-to-liquid ratio, the radial expansion of the spray is conspicuously intensified at the central impactor bolt position, surpassing the expansion at other positions. This phenomenon can be attributed to heightened turbulence levels resulting from the central impactor's presence, intricately shaping the resulting spray dispersion patterns. Another key insight is the substantial influence of droplet size and velocity distribution within the spray, driven by increased spray instability due to the presence of the impactor bolt.

Combustion analyses of various engines (viz., compression ignition engines, spark-ignition engines, and reaction engines) are vital for improving engine geometry through modifications in the existing engine to facilitate the optimum burning of blended fuels. Various kinds of binary and ternary fuel blends are precursors to electric and hydrogen fuel cell vehicles. Optimizing such fuel blend proportions for reducing emissions requires a fast and effective technique that can be used as a handy tool in automobile industries. Single-zone combustion modeling using modified Wiebe function is an effective and fast technique for analyzing stage-wise combustion in internal combustion engines. In the present study, an improved technique for the estimation of Wiebe function parameters is developed that avoids assuming the value of efficiency parameter ‘a’ or form factor ‘m’ of modified Wiebe functions. The transition points divides the combustion stages accurately. Burn fraction evolution and apparent heat release rate as a function of the crank angle duration are predicted using estimated multiple Wiebe function parameters. The values of root mean square error (< 1 J/°CA for predicted apparent heat release rate) and coefficient of determination (> 0.99) indicate higher predictability of the present model compared to previously reported models in the literature.

A specific flow will be drawn by a water turbine operating at a specific speed. The turbine may begin to drain the river if there is insufficient river flow to meet this requirement, which would cause a rapid decline in performance. As a result, it must either regulate itself or change the internal geometry of the system. Regulated turbines can change the amount of flow they draw by moving the runner blades and/or intake guiding vanes. The various turbines’ efficiency will eventually drop as they draw less flow. The novelty of the present work given in the complete specification by adopting the tail race water level at minimum threshold level of 659 m EL at design load of 4 MW will yield saving of 2.27 m3/sec or yield 0.472 MW input hydraulic power. The work will hold the key in novelty during the design and excavation of tail race channel or for renovation, modernization, and uprating (RMU) of the existing old hydropower plants. The design in selecting suitable width, depth and by adopting flow regulating means will yield and improve the net head substantially and thereby saving of discharge to an extent.

A comprehensive and methodical approach has been undertaken to meticulously calculate and devise the design of a commercial helium compressor for general manufacturing purposes. The calculation process involves a thorough assessment of each individual component, encompassing aspects such as the selection of a 6.6 kW refrigeration compressor, design of the heat exchanger, incorporation of an oil filter, utilization of a needle valve, integration of an oil separator, inclusion of a buffer, and consideration of numerous other essential elements within the helium compressor system. To measure the mass flow rate of both oil and helium gas, flow meters have been installed. Additionally, pressure measuring gauges have been incorporated to monitor the system’s pressure levels. The experimental setup has been fabricated and subsequently tested based on the calculations conducted earlier. During the initial run, the system was continuously operated under the conditions of 16 barg high pressure and 6 barg low pressure. The system was operated with the specified conditions, aiming to achieve the required purity (oil content ‹ 0.1 ppm) of helium after the separation of oil vapor.

Pump as turbine (PAT) is one of the most affordable and environmental friendly solutions for electrification in rural areas. These plants are usually run-of-river or hill-based, and during monsoon, they experience a lot of unsettled sediments. The detrimental effects caused by hard particles lead to downtime, repairs, and/or the necessity of replacement, which have an adverse impact on power generation. The present paper aims to investigate the influence of various parameters such as silt size, silt concentration, and operating time on the erosion of the PAT impeller. An attempt has been made to derive the correlation of normalized wear for SS304, and two different coatings, i.e., WC-Co-Cr (86/10/4) and Cr3C2-NiCr (75/25). The various costs related to the plant as a result of shutdown, repair, and coatings have been discussed. The present paper discusses different approaches to operate the PAT hydropower plant under a silty environment. An economic analysis has been carried out to compare the cost-effectiveness of each of the operational strategies. The results showed that the WC-Co-Cr coating applied by the high-velocity oxy-fuel (HVOF) technique is the most feasible solution to keep the PAT running efficiently during the monsoon.

In order to minimize the cost of maintenance and to avoid sudden failures of components in vertical axis wind turbines (VAWT), the employment of a condition monitoring system is necessary. Especially monitoring the source of vibration and controlling is a significant process in the structural reliability of any components. The gearbox in the VAWT is such type of a source to be monitored to avoid substantial downtime. The sudden rise in the need for alternate energy sources, the installation of wind turbines was gradually increased with increased data in condition monitoring. So interpreting and analyzing such vast resources of data required an efficient system. In this article, an automated adapted framework has been employed to analyze the gearbox failure. The adapted framework is anticipated to analyze the vibration signals, monitor the health, and isolate the faults by processing the signals with the support of artificial intelligence and machine learning techniques. It is anticipated to produce an efficient solution for the reduction of downtime in VAWT operations due to failures.

Savonius rotor carries huge potential as standalone power generation device chiefly due to its simplicity and high-torque characteristics. However, several undesirable characteristics hinder its commercial adaptation. One such characteristic is generation of negative torque by returning blade. To overcome this drawback, many techniques have been adopted, and one such technique is using slit or vent. In the paper, the performance analysis is carried out numerically using CFD approach and comparison between conventional semi-circular rotor, rotor equipped with capped vents and slits is carried out. As the performance of rotor is sensitive to vent location, two vent locations are selected, viz. 135° and 120° blade angle (β). Vent gaps, viz. 0.02D, 0.03D, and 0.04D, are chosen for analysis. Slit is analyzed at β = 120° and gap width of 0.03D and 0.04D. The probable physics related to flow around the rotor is discussed to analyze the reasons behind the obtained results. It is found that slit and vents deteriorate the performance ( $${C}_{\text{P}} and {C}_{T}$$ C P a n d C T values) compared to conventional Savonius rotor at all mentioned locations and gap sizes. Slit and vent both techniques produce almost similar results in working TSR range. Also, 135° vent location produces better results than 120° location.

For conveying the liquid from one level to higher level or from one location to another location, still pumps play a vital role. In this work, a glimpse of research related to radial flow pump was discussed in detail. To understand the effects of leading edge, four different leading profiles were designed and simulated using commercial computational fluid dynamics (CFD) tools. Plain, Circular, Ellipse2, and Ellipse4 are the leading edges that are discussed with reference to the CFD findings. Among four leading edges, three (Plain, Circular, and Elipse2) are fabricated and tested for performance as well as for cavitation. The significant changes are observed during performance test at constant speeds as well as during cavitation test for various flow rates and speeds. The clear demarcation was observed for Plain, Ellipse2, and Circular leading edge impellers from the cavitation characteristics and found that Circular leading edge impeller was better than all. Extents of cavitation growth from inception in the impeller passage were examined visually. Through computation studies, it was concluded that the Ellipse4 leading edge is found to be better than all leading edges with reference to the hydraulic performance and the pressure distribution along the vane course. This concludes that the leading edge of impeller vanes has drastic changes in the performance as well as in the cavitation aspects.