Search Results

Abstract This article aims at the calibration of an onboard sensor and actuator parameters as well as the identification of the open-loop transfer function of the steering and traction control systems of tripod electric vehicles (EVs). Tripod EVs are commonly used as forklifts and automatic guided vehicles in a factory or wheelchairs in a hospital. A test procedure called the circular, linear, and cornering motions (CLCM) test is introduced in this article for making the corrections which are caused by many factors including the potentiometer of the steering angle error, hall sensor error of the traction speed, the backlash of the steering system, and the tire slip angle that can lead the tripod EV to deviate from the path. The CLCM test is subdivided into circular, linear, and cornering motion subtasks for each individual identification and calibration purposes.

Abstract Using two subgrid-scale models of Smagorinsky and its dynamic version, large eddy simulation (LES) approach is applied to develop a 3D computer code simulating the in-cylinder flow during intake and compression strokes in an engine geometry consisting of a pancake-shaped piston with a fixed valve. The results are compared with corresponding experimental data and a standard K-Ɛ turbulence model. LES results generally show better agreement with available experimental data suggesting that LES with dynamic subgrid-scale model is more effective method for accurately predicting the in-cylinder flow field.

Abstract Homogeneous charge with direct injection (HCDI) is a single-fuel low-temperature combustion (LTC) strategy that injects diesel into the intake port and inside the engine cylinder. The present study aims to numerically evaluate various oxides of nitrogen (NOx) mitigation methods such as split injection, exhaust gas recirculation (EGR), and water vapor induction in a single-cylinder diesel engine operated in HCDI mode. Numerical investigations are carried out using a commercial computational fluid dynamics (CFD) code CONVERGE. Experimental data are generated in a light-duty diesel engine operated in HCDI mode at 2.4 bar indicated mean effective pressure (imep) (low load) and 4.6 bar imep (high load) conditions to validate the CONVERGE predictions. The production engine is modified to run in HCDI mode through suitable modifications in the intake system, cylinder head, and fuel injection systems.

Abstract Vehicle aerodynamics has been the subject of extensive research, with a heavy emphasis on the vehicle. Heavy vehicles, such as trucks and buses, have undergone aerodynamic studies in recent years to reduce drag and improve fuel economy [1]. In this study, the distribution of air conditioning in the cabin of a passenger bus was investigated by discussing the factors that influence in attaining the desired thermal comfort values such as temperature distribution, relative humidity ratios, and air velocities inside the bus. The research was conducted on three different cases. In this study, different types of air-conditioning (AC) outlets—linear grills, slots diffusers, and gaspers—were used, and the effect of each outlet on temperature distribution, air velocities, and relative humidity ratios within the bus was investigated. In all three cases, the inlet air velocity was set to 0.8 m/s, and the return air was combined in the middle of the bus.

Abstract The idea of using a Micro Gas Turbine (MGT) as range extender for Hybrid Electric Vehicles (HEVs) is discussed in the literature for several years now. It is regarded from an experimental as well as from a numerical point of view, both indicating superior exhaust gas emissions and performance compared to piston engines. This is commonly shown by applying a series of consecutive New European Drive Cycles (NEDC). In 2017, however, the new approval procedure Worldwide harmonized Light vehicles Test Procedure (WLTP) was introduced with a more realistic drive cycle and also a specific test procedure for HEVs. In this work, a drive cycle simulator is set up considering the essential vehicle components and incorporating a detailed model of the MGT steady-state as well as transient emission and performance behavior. The WLTP is applied to an MGT range-extended HEV considering different operating strategies and vehicle configurations.

Abstract The input of combustion heat in engines has a major impact on the piston friction and the resulting wear of the piston skirt. The new methodology presented here enables the simulation of combustion heat input during motored operation, and thus a detailed investigation of the piston friction under realistic piston temperature profiles of real engine operation is possible. For this purpose a standardized engine test bench for motored friction evaluations was expanded to include, among other things, a movable high-power diode laser with special defocusing optics. The setup of the test engine is based on the FEV teardown step methodology [1] and has open access to the engine piston from above due to a cylinder head dummy. Thus, the heat input by means of a high-power diode laser into the piston crown can be made. The reduced engine structure also enables a precise and highly accurate evaluation of the piston friction.

Abstract Nowadays the role played by passenger vehicles on the greenhouse effect is of great value. To slow down both global warming and fossil fuel wasting, the design of high-efficiency engines is compulsory. Downsized Turbocharged Gasoline Direct Injection (TGDI) engines comply with both high-efficiency and power demand requirements. Nevertheless, Direct Injection (DI) inside downsized chambers may result in the fuel wall impingement, depending on the operating conditions. The impact of fuel on the cylinder liner leads to the mixing of the fuel and the lubricant oil in the cylinder wall. When the piston moves, the piston top ring scraps the non-evaporated fuel-oil mixture. Then the scraped fuel-oil mixture may be scattered into the combustion chamber, becoming a source of diffusive flames in all conditions and abnormal combustions known as Low-Speed Pre-Ignitions (LSPI) at the highest loads.

Abstract Joining titanium (Ti) alloys with conventional processes is difficult due to their complex structural properties and ability of phase transformation. Concerning all the difficulties, diffusion bonding is considered as an appropriate process for joining Ti alloys. Ti6Al4V, which is an α+β alloy widely used for aero engine component manufacturing, is diffusion bonded in this investigation. The diffusion bonding process parameters such as bonding temperature, bonding pressure, and holding time were optimized to achieve desired bonding characteristics such as shear strength, bonding strength, bonding ratio, and thickness ratio using response surface methodology (RSM). Empirical relationships were developed for the prediction of the bond characteristics, and sensitivity analysis was performed to determine the increment and decrement tendency of the shear strength with respect to the bonding parameters.

Abstract The simulation of lubricating pumps for internal combustion engines has always represented a challenge due to the high aeration level of the working fluid. In fact, the delivery pressure ripple is highly influenced by the effective fluid bulk modulus, which is significantly reduced by the presence of separated air. This paper presents a detailed lumped parameter model of a variable displacement vane pump with a two-level pressure setting, in which the fluid model takes into account the dynamics of release and dissolution of the air in the oil. The pump was modelled in the LMS Imagine.Lab Amesim® environment through customized libraries for the evaluation of the main geometric features. The model was validated experimentally in terms of pressure oscillations in conditions of low and high aeration. The fraction of separated air in the reservoir of the test rig was measured by means of an X-ray technique.

Abstract This article focuses on the axial crush performance of woven carbon fiber/polyetherimide (CF/PEI) thermoplastic composites using MAT054 in LS-DYNA. The CF/PEI laminates are fully characterized empirically using mechanical test methods, and the experimental data is used to develop a MAT054 material card for LS-DYNA. A second MAT054 material card is developed separately using virtual test data gathered from a multiscale representative volume element (RVE) of the same woven CF/PEI composite. The two MAT054 material cards are implemented in LS-DYNA simulations of single hat-shaped tubular structures under impact. Using only constituent properties from material datasheets as inputs to the multiscale model, the homogenized tensile modulus of the multiscale RVE was within 4% of the experimental composite laminates. However, the multiscale methods overpredicted the tensile and compressive strain to failure and homogenized material strength of the composite laminate.

Abstract The notable increase in combustion noise in the 7–10 kHz band has become an issue in the development of pre-chamber jet ignition combustion gasoline engines that aim for enhanced thermal efficiency. Combustion noise in such a high-frequency band is often an issue in diesel engine development and is known to be due to resonance in the combustion chamber. However, there are few cases of it becoming a serious issue in gasoline engines, and effective countermeasures have not been established. The authors therefore decided to elucidate the mechanism of high-frequency combustion noise generation specific to this engine, and to investigate effective countermeasures. As the first step, in order to analyze the combustion chamber resonance modes of this engine in detail, calculation analysis using a finite element model and experimental modal analysis using an acoustic excitation speaker were conducted.

Abstract An experiment has been developed to investigate the passive pre-chamber jet ignition process in gasoline engine configurations and low-load operating conditions. The apparatus adopted a modified 4-cylinder 2.0L gasoline engine to enable single-cylinder operation. To reduce the complexity, the piston position was fixed at a predefined position relative to the top dead center (TDC) to simulate thermodynamic conditions at ignition and injection timings. High-speed Infrared (IR) imaging was applied to visualize the jet penetration and ignition process inside the main cylinder and to investigate the cyclic spatial variability. Two passive pre-chambers with different total nozzle areas and numbers of nozzles were used. In addition, the pre-chamber volume and pressure at ignition timing were varied to examine their effect on jet ignition performance.

Abstract Small rectangular representative volume element (RVE) specimens of lithium-ion battery modules without and with electrolyte were tested under quasi-static and dynamic in-plane constrained compressive loading conditions. Effects of electrolyte and loading rate on the compressive behavior of RVE specimens were examined. The test results show that the average buckling stress of the specimens with electrolyte is higher than that of the specimens without electrolyte under both quasi-static and dynamic loading conditions. The test results also show that the average buckling stress of the specimens under dynamic loading conditions is higher than that of the specimens under quasi-static loading conditions, without or with the presence of electrolyte in the specimens. The percentage of increase of the average buckling stress of the specimens due to electrolyte under dynamic loading conditions is more than that of the specimens under quasi-static loading conditions.

Abstract Reducing the weight of automotive components is one of the most achievable solutions for lowering the transport carbon footprint. This is the reason for the rapid increase over the last few years in the replacement of conventional alloys (i.e., steel and cast iron) with low-density materials (i.e., aluminum alloys, composites) and in the redesign of components shape in order to remove the unnecessary material (e.g., related to the introduction of additive manufacturing or high-strength materials). Despite this general trend, the use of higher-density metals and massive geometries is still predominant in the production of structural components, especially for heavy vehicles and safety-relevant parts. Aim of the present review is to summarize how this current situation can be overcome. The analysis started with an investigation about the materials that can be used for the production of structural parts, the potential reduction of the component weight and its costs.

Abstract The increasing use of aluminum alloy extrusion in automotive vehicle chassis as structural members has necessitated the need to investigate their crushing behaviors. This article experimentally examines in detail, for the first time with respect to strength, ductility, and microstructure, AA6063-T7 (overaged) condition and the standard T6 temper and their capacity to meet crashworthiness requirements. Both tempers were assessed based on their mechanical properties (strength, ductility, true stress/strain behavior to necking, plastic anisotropy, strain rate sensitivity, and post-instability ductility to fracture) and microstructure, which were determined using basic tensile testing methods and metallographic approach.

Abstract Recently, automation of driving has become a significant interest of both industry and academia. Researchers are investigating different facets of automated driving systems (ADS) to address legal, technical, and logistical problems, which will make ADS-equipped vehicles (AVs) a reliable option for daily transportation. One of the most significant challenges that must be addressed before the mass production of AVs is the verification and validation (V&V) of safety and performance. A comprehensive V&V methodology is required to achieve assurance that the AV operates safely even in an uncertain traffic environment. The V&V Task Force under the Society of Automotive Engineers (SAE) On-Road Automated Driving (ORAD) Committee intends to develop such a V&V testing methodology. The first step in this process is a literature review of various AV V&V efforts, which is the purpose of this document.

Abstract In modern diesel fuel a proportion of biodiesel is blended with petro-diesel to reduce environmental impacts. However, it can adversely affect the operation of nonwoven coalescing filter media when separating emulsified water from diesel fuel. This can be due to factors such as increasing water content in the fuel, a reduction in interfacial tension (IFT) between the water and diesel, the formation of more stable emulsions, and the generation of smaller water droplets. Standard water/diesel separation test methods such as SAE J1488 and ISO 16332 use monoolein, a universal surface-active agent, to simulate the effects of biodiesel on the fuel properties as part of water separation efficiency studies. However, the extent to which diesel/monoolein and diesel/biodiesel blends are comparable needs to be elucidated if the underlying mechanisms affecting coalescence of very small water droplets in diesel fuel with a low IFT are to be understood.

Abstract The supersession of metallic alloys with lightweight, high-strength composites is popular in the aircraft industry. However, aviation electronic enclosures for large format batteries and high power conversion electronics are still primarily made of aluminum alloys. These aluminum enclosures have attractive properties regrading structural integrity for the heavy internal parts, electromagnetic interference (EMI) suppression, electrical bonding for the internal cells, and/or electronics and failure containment. This paper details a lightweight carbon fiber composite chassis developed at Meggitt Sensing Systems (MSS) Securaplane, with a copper metallic mesh co-cured onto the internal surfaces resulting in a 50% reduction in weight when compared to its aluminum counterpart. In addition to significant weight reduction, it provides equal or improved performance with respect to EMI, structural and flammability performance.

Abstract Letter from the Special Issue Editors

Abstract Letter from the Guest Editors