Advances in Engine and Powertrain Research and Technology

Simulation of dynamics is one of the important tasks in engineering calculation projects related to internal combustion engine-based powertrains. It allows to evaluate strength and durability of engine parts, reliability and wear of their lubricated contacts, noise, and vibratory interaction of the powertrain with the vehicle body. Depending on the modeling depth and on the scope and accuracy of results, the software tools used for simulation of powertrain dynamics, can be sub-divided into fast basic tools and precise high-end tools. It is shown that in order to reach the expected quality and to be timely efficient at the same time, a complete project should apply a combined dynamic simulation workflow consisting of two main phases: (1) early phase, with system check, basic analysis and layout, as well as coarse optimization using basic tools, and (2) final phase, with fine tuning and verification of critical parameters of the system using high-end tools. The present chapter gives an extended overview of the typical design analysis tasks and related software tools used in the early phase of powertrain simulation workflow. It should be noted that efficient dynamic models of engine parts—first of all crankshaft—significantly contribute to shorter preparation for high-performance calculations, and to smooth transition between different tasks and phases of the project.

This chapter presents the theoretical formulation for torsional vibration analysis in internal combustion engines. The methodology can be applied to several crankshaft geometries with different cylinder configurations. The steady-state solution of the equations considers the state transition matrix and the convolution integral. Here, this formulation is applied to the mathematical model of a six-cylinder diesel engine with 7.2 l of volumetric displacement and a viscous damper assembled at the crankshaft front end to reduce the vibration amplitude. With the results of the torsional vibration analyses, it is possible to determine the dynamic torque at each region of the crankshaft. Finally at the end of the chapter, the calculated torsional vibration amplitudes at the crankshaft front end are compared with measured values from an engine to validate the proposed methodology.

A bench rig is designed, constructed, and used to determine the scuffing mechanism and threshold conditions, and to investigate the effects of surface roughness, clearance, circumferential groove, oil temperature, and oil feeding rate on scuffing in piston-pin/bore contacts. The bench rig simulating conditions include time-dependent dynamic load over a complete engine cycle, an oscillatory rotation, a constant surface velocity corresponding to the maximum surface velocity of the piston pin in real engines, and surface and material properties. Based on the experimental results, it is concluded that the scuffing failure mechanism involves adhesion and fatigue. The deterioration of the surface shear strength by fatigue cracks under a high surface temperature appears to contribute to the final scuffing of the pin-piston contact. The effects of the bore surface roughness and groove on the scuffing behavior are more significant than the clearance. A computer model to study the onset of scuffing conditions at the pin/piston interface is developed. The scuffing factor and the scuffing failure mapping reflect the interaction among the related mechanisms of wear, relevant parameters, and the inaccuracy in modeling.

Since the Industrial Revolution (1760–1820), 2040 gigatonnes of carbon dioxide (CO₂) were emitted to the atmosphere and the half of these emissions occurred between 1970 and 2010. Worldwide, greenhouse gas (GHG) emissions increased over 1970–2010, with larger absolute increases between 2000 and 2010 and 14% of this total amount was released due to transportation. Furthermore, 65% of GHG emissions are related to CO₂ and, in order to mitigate its effect on global warming, stricter legislations lowered the CO₂ emission limits for automobiles. To achieve these stricter emission limits, the strategy of engine downsizing with the use of a turbocharger has been adopted by the automotive industry. The turbocharger is characterized as a low weight and high-speed rotor, achieving rotational speeds as high as 350 krpm. To withstand these extremely high rotating speeds, the shaft is commonly supported by floating ring bearings, leading to complex rotor dynamic phenomena. This work summarizes the rotor dynamics of automotive turbochargers, presenting its expected, general behavior, along with a literature review on the most important topics regarding turbocharger dynamic analyses. The nonlinear effect of the floating ring bearing on the shaft lateral vibrations is discussed, along with the effect of different bearing systems on the turbocharger response, including the thrust bearing effect on the rotor axial and lateral dynamics. Current researches on turbocharger modelling and investigation are also presented. Most works rely on developing high fidelity models with low computational costs, including several different effects, such as temperature variations and mass-conserving cavitation algorithms in the lubricated bearings, investigations on newer geometries of the floating ring and thrust bearings and optimal solutions to reduce friction losses.

With evolving global CO₂ emissions legislation and the increased adoption of electrified powertrains such as hybrid electrics, there is a growing need to extract more fuel efficiency from the Gasoline SI engine. By applying gasoline low temperature combustion over typical driving cycle conditions and traditional stoichiometric spark-ignition combustion over the high speed and high load operating conditions, reduced peak pressures and low friction losses can be maintained across the entire operating ranges, consistent with standard SI engine vehicle practices and expectations. This research is focused on combining three enabling technologies for synergistic integration: (a) downsized boosting to address parasitic losses, (b) lean, low temperature combustion to address heat and work extraction losses, and (c) physics-based cylinder-pressure driven controls to streamline the calibration and implementation process. In summary, this research shows that an advanced low temperature combustion system integrated with modern downsize boosted engine technology can deliver a significant fuel consumption benefit (~20%) over conventional natural-aspirated, homogeneous stoichiometric spark-ignition engines. Furthermore, this research proves that this can be done with commercially available fuels, without impacting the customer experience consistent with the most stringent emissions requirements (SULEV30).

Three-dimensional numerical simulations of mixture formation, autoignition, and combustion processes in a cylinder of a sample Diesel engine using the detailed reaction mechanism of fuel oxidation are performed. Particular attention is paid to the autoignition process. The three-stage nature of fuel autoignition in a Diesel engine characterized by the successive appearance of cool, blue, and hot flame exothermic centers has been observed computationally for the first time. The specific features of each of the three stages of autoignition and their interaction with each other are revealed. The location of the first centers of autoignition is identified. The influence of the parameters of numerical procedure on the calculated characteristics of multistage autoignition is investigated. The influence of the fuel Cetane number on the engine operation process is discussed.

Future emission standards and renewable energy targets present a significant challenge for internal combustion engine manufacturers, requiring continuous improvements in efficiency and use of newly developed, preferably carbon neutral, fuels. As an answer to the future challenges, Reactivity Controlled Compression Ignition (RCCI) concept was developed with the aim to attain low emissions of NO_x and particulate mass (PM) simultaneously. In the recent years, the RCCI concept is becoming even more attractive, since recently up-scaled renewable fuels exhibit a wide interval of different reactivities, making them ideal for obtaining the desired combustion parameters in RCCI combustion concept. In the present chapter, an application of direct injection of renewable Hydrotreated Vegetable Oil (HVO) and port injection of Methane rich natural gas in RCCI concept is discussed. The application features low local combustion temperatures preventing local formation of high NO_x concentrations, with a high degree of charge homogenization, which is crucial for achieving low emissions of particulate matter. The presented results and discussion focus on the influence that different engine control strategies have on the main combustion process and emission indicators. Relations between different engine control strategies, including variation of energy shares of utilized fuels, direct injection timing of the direct injection and gas path control, engine thermodynamic parameters and engine-out emissions were deeply investigated and benchmarked with conventional diesel combustion. The results show that with an innovative combination of alternative fuels, significant simultaneous reduction of NO_x and PM engine-out emissions can be achieved.

The stratified fuel distribution and early flame development in a firing spray-guided direct-injection spark-ignition (DISI) engine are characterized applying optical diagnostics. The goal is to compare effects of single and double injections on the stratified air–fuel mixing and early flame development. Vaporized in-cylinder fuel distributions resulting from both single and double injections before, during and after ignition are selectively visualized applying Rayleigh scattering. Reynolds-averaged Navier–Stokes (RANS) simulations are performed to facilitate interpretation of the obtained experimental data. Two hypotheses are tested. First, injecting the fuel as a closely coupled double injections can improve mixing. Second, the better mixing putatively associated with double injections is mainly due to either a longer mixing time or higher mixing rate (driven by turbulence generated by the injections). The optical investigation of the in-cylinder fuel distributions and early flame propagation corroborated the better mixing, showing that double injections are associated with more evenly distributed fuel, fewer local areas with high fuel concentrations, faster initial flame spread and more even flame propagation (more circular flame spreading). The results from both the experiments and the simulations support the hypothesis that delivering fuel in closely coupled double injections results in better mixing than corresponding single injections. According to the simulations, the improved mixing stems from the longer time available for mixing of the air and fuel in double injection events, which has stronger effects than the higher computed peak bulk mixing rate for single injections.

The primary source of energy in all engines and powertrains is the “Fuel”. This term includes a range of different types from gas to distillate or synthetics and to heavy liquid fuels. The primary function of a fuel is to offer the requested amount of energy to the powertrain in all conditions and in all domains (land, sea, and air). Additionally, fuel is an important source of emissions that strongly impact air quality but also a pollutant for land and marine environments. The continuous effort to impose stricter limits led to the alteration of the fuel characteristics. Simultaneously, compatible advance alternative fuels (ex. biofuels such as biomethane, biodiesel, bioethanol, etc.) and renewable and synthetic fuels entering the market. This chapter presented an overview of Fuel characteristic associated with the development of different standards (both civil and military) for different kind of fuels which are associated with different propulsion systems. The continuous development of the fuel standards for compressed ignition engines in association with the biofuel standards will be analyzed. For spark ignition engines, unleaded petrol in association with ethanol fuel as blending components for petrol will be examined. The development of marine fuels including the biofuels and the new synthetic fuels from synthesized hydrocarbons will be presented. The Liquefied Petroleum Gas (LPG) will be examined. An important analysis will be presented for the aviation turbine fuels through the development of synthesized hydrocarbons.

Due to the continuous tightening of the Corporate Average Fuel Economy standards on passenger vehicles, several options are being explored in the automotive industry to reduce the consumption further in electrified powertrains, with one of the options being replacing internal combustion engines with alternative energy converters. Turbogenerator systems are among potential energy converters as they present fundamental benefits to powertrain applications, such as high efficiency, multi-fuel use, cogeneration capability, reduced vibration and noise, fewer components and compactness, as well as reduced weight compared to the engine and other energy converters. These systems are typically suitable for extended-range electric vehicles with a series-hybrid powertrain configuration, given their capacity to recharge the batteries at high efficiency and consequently extend the vehicle electric range beyond the typical urban driving limits. This chapter presents a methodology to design turbogenerators and optimize their system configuration to replace the engine in the auxiliary-power-unit of a series-hybrid powertrain. It consists of conducting first an exergo-technological analysis to identify the optimal turbogenerator system configuration, and second, assessing the resulting energy consumption while accounting for the additional consumption from thermal comfort and other auxiliaries on the Worldwide harmonized Light vehicle Test Cycle. For reference, the proposed methodology is applied to several turbogenerator systems, namely a simple gas-turbine, an external combustion gas-turbine, and a combined-cycle gas-turbine. The optimal configuration and design parameters for each of the three systems are identified while respecting automotive technological constraints. Consumption results show fuel savings up to 25% as compared to a reference extended-range electric vehicle equipped with an engine, depending on the battery size, the trip length, and the maximum turbine inlet temperature. Consequently, the proposed methodology helps design optimal turbogenerator systems presenting a serious alternative to engines on series-hybrid electrified vehicles, should the cost-effectiveness of these systems be proven.

In this chapter we review, discuss and critically evaluate the progress made towards zero-prototype development of electrified powertrains. The chapter will focus on fully electric powertrains rather than any combination of electrical and internal combustion engine power units (hybridisation). Emphasis will be given on disciplines that have previously, in the first instance, been looked at in isolation e.g. dynamics without coupling to tribological effects and powertrain transient dynamics without coupling to motor electromagnetics. Computational, numerical, and analytical simulation methods will be evaluated for prediction of mechanical efficiency and wear, as well as Noise, Vibration and Harshness. Areas in the available literature that require further investigation will be highlighted, with suggestions for future developments and directions of future research.

A detailed experimental research is time consuming and expensive, which increases the use of numerical simulations in all engine development stages, especially for extensive analysis and optimization of various operating parameters that affect the engine operation. In such cases the so-called cycle-simulation models, based on 1-D/0-D approach, can be very helpful by shortening the process of engine’s operating map calibration. In recent years, such models are more and more intended to be real-time capable to enable their application in HiL (Hardware-in-the-Loop) simulations. Therefore, the challenge is to find the optimal balance between predictability and calculation speed of the model. This chapter presents a calibration procedure of a real-time cycle-simulation model with the aim of achieving good predictability of the model with minimal requirements for experimental investigations necessary for calibration of model parameters. The procedure includes calibration of both gas exchange and combustion model constants with the help of Proportional Integral (PI) controllers for each of the experimentally investigated operating points, and afterwards the parametrization of the selected constants based on the calibration results. The resulting parametrized model features computational speed compatible for HiL simulations, and the validation of the model showed that calculation results are in close agreement with the experimentally obtained results in the entire operating map of a naturally aspirated 1.4 L spark ignited engine.

Hardware-in-the-loop test rigs represent one of the most adopted experimental platforms to assess automotive transmissions dynamic performances. Even if their architectures may range among few different configurations, they share general requirements from the mechanical design to their controller implementation for a real-time deployment. This chapter is focused on a real application of a Dual Clutch Transmission Hardware-in-the-loop test rig. Two electric motors are installed to emulate the effect of the Internal Combustion Engine to the transmission input and the vehicle motion resistances to the transmission output, respectively. For a proper Hardware-in-the-loop operation, if a torque control is selected for one electric motor, the second one requires to be controlled in speed. Moreover, the controls structure cannot be usually customized since they are conventionally constrained by industrial drive limitations. This chapter includes an accurate analysis of the reciprocal influence of the two controllers since they are mechanically applied to the input and output of the same transmission. The analysis is further supported by a linear model of the transmission test rig which is able to predict the sensitivity effect of the two controller’s activation on the test rig performance. An optimal tuning of the two controllers’ parameters is then described to achieve the desired level of reference tracking and disturbance rejection targets.

Turbomachinery condition monitoring and diagnostics has come a long way in the last few decades. The main tool for monitoring and diagnosis of turbomachinery is the use of vibration measurement and analysis. Along with machine operating parameters, machine vibration analysis provides a complete picture of turbomachinery condition and can be used to perform a complete analysis and a diagnostic result can be subsequently obtained. Usually diagnostics is performed after an anomaly has been detected through monitoring. This is the approach taken by ISO 13373 series of diagnostic standards. This chapter discusses methods of vibration measurement for machinery monitoring and diagnostics. The sensors used, their operating principles and installation methods are described, as well as the required instrumentation and measurement set-up. The main tool for vibration diagnosis is the spectrum, however, for a complete and accurate diagnosis other vibration tools may have to be considered, including the overall amplitude, time waveform, the phase, the orbit and in some cases an operating deflection shape analysis (ODS) may need to be performed. Finally recent trends shall be briefly discussed, including the use of wireless sensors, cloud monitoring, expert diagnosis, the use of artificial intelligence in diagnosis, as well as the very recent use of vibration video motion magnification technology.

The manufacturing of powertrain components for light vehicles became more challenging during the last years, due to the powertrain diversity caused by the powertrain’s electrification. Based on this fact, the conventional process should be adapted to the use of different types of components and low production volumes while keeping the production costs on acceptable level. One of the extensively used manufacturing processes is High-Pressure Die Casting (HPDC) for aluminum and magnesium alloys, characterized by high complexity and high investments cost. Besides the casting processes, the additive manufacturing techniques introduced in the last years, offer new possibilities mainly due to the wide range of alloys and the possibility to shape up complex geometries. This chapter gives a comprehensive overview on the manufacturing methods used in the production of structural parts of powertrain and treats some advanced subjects of manufacturing issues and future trends.