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Journal Article

A Predictive Tool to Evaluate Braking System Performance Using Thermo-Structural Finite Element Model

2019-10-14
Abstract The braking phenomenon is an aspect of vehicle stopping performance where with kinetic energy due to the speed of the vehicle is transformed into thermal energy produced by the brake disc and its pads. The heat must then be dissipated into the surrounding structure and into the airflow around the brake system. The thermal friction field during the braking phase between the disc and the brake pads can lead to excessive temperatures. In our work, we presented numerical modeling using ANSYS software adapted in the finite element method (FEM), to follow the evolution of the global temperatures for the two types of brake discs, full and ventilated disc during braking scenario. Also, numerical simulation of the transient thermal analysis and the static structural analysis were performed here sequentially, with coupled thermo-structural method.
Journal Article

A Contribution to Improving the Thermal Management of Powertrain Systems

2019-10-08
Abstract This work presents a generalized methodology for the optimal thermal management of different powertrain devices. The methodology is based on the adoption of an electrically driven pump and on the development of a specifically designed controller algorithm. This is achieved following a Model Predictive Control approach and requires a generalized lumped-parameters model of the thermal exchange between the device walls and the coolant. The methodology is validated at a test rig, with reference to a four-cylinder spark-ignition engine. Results show that the proposed approach allows a reduction in fuel consumption of about 2-3% during the engine warm-up, a decrease in fuel consumption of about 1-2% during fully warmed operation, and an estimated fuel consumption reduction of about 2.5-3% in an NEDC. Finally, the investigation highlights that the proposed approach reduces the risk of after-boiling when the engine is rapidly switched off after a prolonged high-load operation.
Journal Article

Effects of Water Injector Spray Angle and Injector Orientation on Emission and Performance of a GDI Engine - A CFD Analysis

2019-10-08
Abstract Higher water evaporation and proper water vapor distribution in the cylinder are very vital for improving emission and performance characteristics of water-injected engines. The concentration of water vapor should be higher and uniform near the walls of the combustion chamber and nil at the spark plug location. In direct water-injected engines, water evaporation, vapor distribution, and spray impingement are highly dependent on injector parameters, viz., water injector orientation (WIO), location, and spray angle. Therefore, in this article, a computational fluid dynamics (CFD) investigation is conducted to study the effects of water injector spray angle (WISA), and WIO on the water evaporation, emission, and performance characteristics of a four-stroke, wall-guided gasoline direct injection (GDI) engine. The WISA is varied from 10° to 35°, whereas the WIO is varied from 15° to 35° in steps of 5°.
Journal Article

Comparison of Regulated and Unregulated Emissions and Fuel Economy of SI Engines with Three Fuels: RON95, M15, and E10

2019-10-04
Abstract This article focuses on a comparative research of the emissions discharged from four vehicles equipped with SI engines, which comply with different emission control systems (Euro 6, Euro 5, and Euro 3). The vehicles used for this work were installed with two different fuel injection technologies (direct injection and port fuel injection) and were operated with three different types of fuels (RON 95, M15, and E10). The tests were performed at the Joint Research Center (JRC) in Ispra using a state-of-the-art emissions test facility according to the European emissions legislation. The test bench included a chassis dynamometer and two different driving cycles were used: NEDC and US06.
Journal Article

Localization Requirements for Autonomous Vehicles

2019-09-24
Abstract Autonomous vehicles require precise knowledge of their position and orientation in all weather and traffic conditions for path planning, perception, control, and general safe operation. Here we derive these requirements for autonomous vehicles based on first principles. We begin with the safety integrity level, defining the allowable probability of failure per hour of operation based on desired improvements on road safety today. This draws comparisons with the localization integrity levels required in aviation and rail where similar numbers are derived at 10−8 probability of failure per hour of operation. We then define the geometry of the problem where the aim is to maintain knowledge that the vehicle is within its lane and to determine what road level it is on.
Journal Article

A Novel Metaheuristic for Adaptive Signal Timing Optimization Considering Emergency Vehicle Preemption and Tram Priority

2019-09-24
Abstract In this article, a novel hybrid metaheuristic based on passing vehicle search (PVS) cultural algorithm (CA) is proposed. This contribution has a twofold aim: First is to present the new hybrid PVS-CA. Second is to prove the effectiveness of the proposed algorithm for adaptive signal timing optimization. For this, a system that can adapt efficiently to the real-time traffic situation based on priority signal control is developed. Hence, Transit Signal Priority (TSP) techniques have been used to adjust signal phasing in order to serve emergency vehicles (EVs) and manage the tram priority in a coordinated tram intersection. The system used in this study provides cyclic signal operation based on a real-time control approach, including an optimization process and a database to manage the sensor data from detectors for real-time predictions of EV and tram arrival time.
Journal Article

An Energy Management Strategy for Through-the-Road Type Plug-in Hybrid Electric Vehicles

2019-09-19
Abstract This article proposes an energy management strategy for a through-the-road (TTR) plug-in hybrid electric vehicle (PHEV) to achieve efficient fuel consumption performance. The target hybrid powertrain includes an electric traction motor, an integrated starter/generator (ISG), and a gasoline internal combustion engine (ICE) in the front axle and another electric motor in the rear axle. The energy management strategy is organized into six functional modules. The power mode is determined by the driver’s pedal demand, vehicle states, and the characteristics of the related power units to increase the overall system efficiency. The energy management strategy and the vehicle models are established in the Matlab/Simulink by using dSPACE Automotive Simulation Models (ASM) software. The proposed strategy is examined in terms of three test scenarios in the Model-in-the-Loop (MiL) simulations.
Journal Article

Brake Squeal Prevention through Suspension Design and Adaptive Suspension

2019-09-03
Abstract The brake squeal phenomenon has bothered automobile manufacturers for a long time. Although having no ill effects on the braking performance, the squeaky noise is often a nuisance and one of the major complaints of many customers. In order to design quality and noise-free automobiles, the brake squeal issue has to be permanently tackled. Controlling brake squeal by the addition of damping on the disk and shape optimization has been suggested by many researchers. Other methods proposed in the literature include the use of a different brake pad material or an anti-squeal paste. However, the effect of the type of brake pad suspension on brake squeal has not been studied. In this article, we demonstrate that the use of a 4-element viscoelastic support can help prevent brake squeal for the practical vehicle speed range. For a 2-element support, we have identified a suitable control parameter and proposed an efficient active control for squeal prevention based on that.
Journal Article

Evaluation of Dynamic Wheel Alignment Audit System Performance

2019-09-03
Abstract Wheel alignment audit systems are used in vehicle service environments to identify vehicles which may benefit from a comprehensive evaluation on a precision static alignment measurement system. Non-contact dynamic wheel alignment audit systems acquire measurement data from vehicles in motion passing between sensors in an inspection lane. The dynamic nature of the moving vehicles introduces variables which are not present when auditing wheel alignment on a static vehicle. Measurement results are affected by changes in vehicle velocity, steering movement, suspension movement, floor surface conditions, tire sidewall profiles, and driver presence, as well as other variables.
Journal Article

Empirical Investigation on the Effects of Rolling Resistance and Weight on Fuel Economy of Medium-Duty Trucks

2019-08-28
Abstract Vehicle rolling resistance and weight are two of the factors that affect fuel economy. The vehicle tire rolling resistance has a more significant influence than aerodynamics drags on fuel economy at lower vehicle speeds, particularly true for medium- and heavy-duty trucks. Less vehicle weight reduces inertia loads, uphill grade resistance, and rolling resistance. The influence of weight on the fuel economy can be considerable particularly in light- to medium-duty truck classes because the weight makes up a larger portion of gross vehicle weight. This article presents an empirical investigation and a numerical analysis of the influences of rolling resistance and weight on the fuel economy of medium-duty trucks. The experimental tests include various tires and payloads applied on a total of 21vehicle configurations over three road profiles. These tests are used to assess the sensitivity of rolling resistance and weight to the vehicle fuel economy.
Journal Article

Application of Optimal Control Method to Path Tracking Problem of Vehicle

2019-08-26
Abstract Path tracking is an essential stage for vehicle safety control. It is more newsworthy than ever in the automotive context and especially for autonomous vehicle. The study proposes an optimal control method for path tracking problem in inverse vehicle handling dynamics. The proposed method generates an expected trajectory which guarantees minimum clearance to the prescribed path by identifying the optimal steering torque input. Based on this purpose, the path tracking problem, which is treated as an optimal control problem, is then solved by local collocation method and mesh refinement. Finally, a real vehicle test is executed to verify the rationality of the proposed model and methodology. The results show that using control variables as a mesh refinement function can capture the dramatic changes in state variables, and the efficiency improvement is more significant as the number of the grid points increases.
Journal Article

Assessing Viscosity in Hydro-Erosive Grinding Process via Refractometry

2019-08-22
Abstract The manufacturing of diesel injector nozzles requires precision processing to produce multiple micro-holes. An abrasive fluid containing a mixture of mineral oil and hard particles is used for rounding them, ensuring the hydrodynamics of the injection. As verified in a previous investigation, the viscosity of the fluid undergoes uncontrolled changes during hydro-erosive (HE) grinding. Such undesired viscosity changes are detrimental to the process and difficult to assess. The current investigation aims to study the possibility of using the refractive index of the oils used in the HE grinding for assessing their viscosities. A calibration curve correlating the refractive index and viscosity was obtained from the analysis of samples produced by mixing two distinct mineral oils in different proportions. The determined calibration curve was tested with 45 samples of filtered oil, collected directly from the tanks during the HE grinding.
Journal Article

Numerical Study of Pore Size and Distribution Effects on Gasoline Particulate Filter Performance

2019-08-22
Abstract The improved brake thermal efficiency of Gasoline Direct Injection (GDI) engines is accompanied by a significant increase in Particulate Matter (PM) mass and higher Particulate Number (PN) emissions as compared to (multi)Port Fuel Injected (PFI) engines. Gasoline particulate filters (GPFs) with high filtration efficiency and low backpressure will be required to meet the future, stringent PM/PN regulations. A two-dimensional (2D) CFD study was performed to determine the effects of pore size and distribution on the interdependent performance parameters of filtration efficiency and backpressure for clean GPFs. Simulation results show an on linear change infiltration efficiency as the pore size distribution tightens and determine a recommended distribution range, controlling the quantity of small-sized pores. Pore size distributions beyond this recommended range can cause a filtration performance loss or intolerable backpressure penalty for the GPF.
Journal Article

A Guide to Uncertainty Quantification for Experimental Engine Research and Heat Release Analysis

2019-08-22
Abstract Performing an uncertainty analysis for complex measurement tasks, such as those found in engine research, presents unique challenges. Also, because of the excessive computational costs, modeling-based approaches, such as a Monte Carlo approach, may not be practical. This work provides a traditional statistical approach to uncertainty analysis that incorporates the uncertainty tree, which is a graphical tool for complex uncertainty analysis. Approaches to calculate the required sensitivities are discussed, including issues associated with numerical differentiation, numerical integration, and post-processing. Trimming of the uncertainty tree to remove insignificant contributions is discussed. The article concludes with a best practices guide in the Appendix to uncertainty propagation in experimental engine combustion post-processing, which includes suggested post-processing techniques and down-selected functional relationships for uncertainty propagation.
Journal Article

Numerical Aspects Affecting Heat Transfer in ICE Applications and Definition of a Temperature Wall Function Accounting for the Boundary Layer Compressibility

2019-08-22
Abstract The heat transfer phenomena in Internal Combustion Engines (ICEs) are one of the main research topics that need to be addressed to enhance the performance in terms of power, efficiency, emissions and reliability. The present study is focused on the evaluation of the in-cylinder heat fluxes through the use of Computational Fluid Dynamic (CFD) simulations, with a wall function approach. In particular, the aim of this work is to present a new fully non-isothermal wall function obtained from the one-dimensional (1-D) energy balance equation for turbulent flows in the boundary layers, specifying all the steps and assumptions which have carried to the final fully compressible formulation. The new proposed wall function has been validated against experimental data of the General Motors (GM) Pancake Engine, representative of low Brake Mean Effective Pressure (bmep) operating point, comparing the results with other existing wall functions.
Journal Article

Torque and Pressure CFD Correlation of a Torque Converter

2019-08-22
Abstract A torque converter was instrumented with 29 pressure transducers inside five cavities under study (impeller, turbine, stator, clutch cavity between the pressure plate and the turbine shell). A computer model was created to establish correlation with measured torque and pressure. Torque errors between test and simulation were within 5% and K-Factor and torque ratio errors within 2%. Turbulence intensity on the computer model was used to simulate test conditions representing transmission low and high line pressure settings. When turbulence intensity was set to 5%, pressure simulation root mean square errors were within 11%-15% for the high line pressure setting and up to 34% for low line pressure setting. When turbulence intensity was increased to 50% for the low line pressure settings, a 6% reduced root mean square error in the pressure simulations was seen.
Journal Article

Energy-Management Strategy for Four-Wheel Drive Electrohydraulic Hybrid System with Optimal Comprehensive Efficiency

2019-08-22
Abstract The four-wheel drive electric sport utility vehicle (SUV) requires high dynamic performance, and the front and rear axles are matched with a high-power motor. High-power motors operate under low-speed and low-torque conditions, with low efficiency and large power loss. To reduce the power loss under low-speed and low-load conditions, a hybrid system of front and rear dual motors and dual hydraulic pumps/motors is designed. A simulation model of a four-wheel drive SUV electrohydraulic hybrid system is constructed. Aiming at the optimal energy consumption, a dynamic programming algorithm is adopted to establish the driving control rules of the vehicle. Constrained by the Economic Commission for Europe Regulation No.13 (ECE R13), a braking-force distribution strategy for the front and rear axles is formulated. On the premise of satisfying the braking safety, regenerative braking is preferred, and the braking energy is recovered to the greatest extent possible.
Journal Article

Elastomer Swell Behavior in 1-Propanol, Diisobutylene, Cyclopentanone, and a Furan Mixture Blended in E10 and a Blendstock for Oxygenate Blending (BOB)

2019-08-21
Abstract The compatibility of four potential bio-derived blendstock molecules with infrastructure elastomers was determined by measuring the volume change following exposure. The blendstock molecules included 1-propanol, diisobutylene, cyclopentanone, and a furan mixture. The elastomers included two fluorocarbons, six nitrile rubbers (NBRs), and one each of fluorosilicone, neoprene, polyurethane, and silicone. The elastomers were exposed to the fuel molecules as blends ranging from 0 to 30 vol.% in both a blendstock for oxygenate blending (BOB) formulation and an E10 fuel. Silicone exhibited excessive swelling in each test fuel, while the other elastomers showed good compatibility (low swell) with diisobutylene, 1-propanol, and the furan mixture when BOB was used as the base fuel. The E10 base fuel produced high (>30%) swell in neoprene, polyurethane, and some nitrile rubbers. In most cases diisobutylene produced the least amount of volume expansion.
Journal Article

A Global Sensitivity Analysis Approach for Engine Friction Modeling

2019-08-21
Abstract Mechanical friction simulations offer a valuable tool in the development of internal combustion engines for the evaluation of optimization studies in terms of time efficiency. However, system modeling and evaluation of model performance may be highly complex. A high number of interacting submodels and parameters as well as a limited model transparency contribute to uncertainties in the modeling process. In particular, model calibration and validation are complicated by the unknown effect of parameters on the model output. This article presents an advanced and model-independent methodology for identifying sensitive parameters of engine friction. This allows the user to investigate an unlimited number of parameters of a model whose structure and properties are prior unknown.
Journal Article

Low- to High-Temperature Reaction Transition in a Small-Bore Optical Gasoline Compression Ignition (GCI) Engine

2019-08-19
Abstract This study shows the development of low-temperature and high-temperature reactions in a gasoline-fuelled compression ignition (GCI) engine realizing partially premixed combustion for high efficiency and low emissions. The focus is how the ignition occurs during the low- to high-temperature reaction transition and how it varies due to single- and double-injection strategies. In an optically accessible, single-cylinder small-bore diesel engine equipped with a common-rail fuel injection system, planar laser-induced fluorescence (PLIF) imaging of formaldehyde (HCHO-PLIF), hydroxyl (OH-PLIF), and fuel (fuel-PLIF) has been performed. This was complemented with high-speed imaging of combustion luminosity and chemiluminescence imaging of cool flame and OH*.
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