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This investigation was aimed at measuring the relative performance of two spray-guided, single-cylinder, spark-ignited direct-injected (SIDI) engine combustion system designs. The first utilizes an outwardly-opening poppet, piezo-actuated injector, and the second a conventional, solenoid operated, inwardly-opening multi-hole injector. The single-cylinder engine tests were limited to steady state, warmed-up conditions. The comparison showed that these two spray-guided combustion systems with two very different sprays had surprisingly close results and only differed in some details. Combustion stability and smoke emissions of the systems are comparable to each other over most of the load range. Over a simulated Federal Test Procedure (FTP) cycle, the multi-hole system had 15% lower hydrocarbon and 18% lower carbon monoxide emissions.

With deflected-disc dampers, digressive force-velocity shapes are achieved via the combined effects of disc stack stiffness and hub-offset. The degree of digressiveness can be adjusted to alter vehicle performance by changing the proportion of these parameters. Optimizing this relationship can yield substantial vehicle performance improvements, but the time consuming iterative process of developing a new disc stack for each hub-offset discourages experimentation. To enable more efficient digressiveness comparisons, a regression-based computational method has been developed which converts disc stack stiffness from one hub-offset to other offsets directly, without iteration. Once an initial disc stack for one offset has been tuned by traditional methods, stacks for other offsets can be calculated that maintain overall damper control.

A simulation methodology is developed for the Constant Radius Constant Speed (CRCS) analysis to predict the ISO4138 [1] road test performance. The CRCS analysis can be used to predict the vehicle steady-state handling characteristics such as understeer, rear cornering compliance, and roll gradient, etc. The Yaw-Rate Control methodology is applied to replace the traditional driver-in-the-loop path-following approaches. Comparing to the path-following approaches, the proposed method is simpler to use, more efficient, accurate, and robust.

This paper presents an alternative launch device for layshaft dual clutch transmissions (DCT's). The launch device incorporates a hydrodynamic torque converter, a lockup clutch with controlled slip capability and two wet multi-plate clutches to engage the input shafts of the transmission. The device is intended to overcome the deficiencies associated with using conventional dry or wet launch clutches in DCT's, such as limited torque capacity at vehicle launch, clutch thermal capacity and cooling, launch shudder, lubricant quality and requirement for interval oil changes. The alternative device enhances drive quality and performance at vehicle launch and adds the capability of controlled capacity slip to attenuate gear rattle without early downshifting. Parasitic torque loss will increase but is shown not to drastically influence fuel consumption compared to a dry clutch system, however synchronizer engagement can become a concern at cold operating temperatures.

This paper outlines a process to assess the aerodynamic performance of different vehicle exterior surfaces. The initial section of the paper summarizes the details of white-light scanning process that maps entire vehicle to points in Cartesian co-ordinate system which is followed by the conversion of scanned points to theme surface. The concept of point-cloud modeling is employed to generate a smooth theme surface from scanned points. Theme surfaces thus developed are stitched to under-body/under-hood (UB/UH) parts of the base vehicle and the numerical simulations were carried out to understand the aerodynamic efficiency of the surfaces generated. Specifics of surface/volume mesh generated, boundary conditions imposed and numerical scheme employed are discussed in detail. Flow field over vehicle exterior is thoroughly analyzed. A comparison study highlighting the effect of front grilles in unblocked condition along with air-dam on flow field has been provided.

Determining Li-ion battery life through life modeling is an excellent tool in determining and estimating end-of-life performance. Achieving End-of-Life (EOL) can be challenging since it is difficult to achieve both cycle and calendar life during the same test without years of testing. The plan to correlate testing with the model included three (3) distinct temperature ranges, beginning with the four-Season temperature profile, an aggressive profile with temperatures in the 50 to 55°C range, and using a mid-temperature range (40-45°C) as a final comparison test. A high duty-cycle drive profile was used to cycle all of the batteries as quickly as possible to reach the one potential definition of EOL; significant increases in resistance or capacity fade.

The main objective of this work is to demonstrate the merits of the Adjoint method to provide comprehensive information for shape sensitivities and design directions to achieve low drag vehicle shapes. The adjoint method is applied to a simple 2D airfoil and a 3D vehicle shape. The discrete Adjoint equations in the flow solvers are used to investigate further potential shape improvements of the low drag vehicle shapes. The low drag vehicle used in this study was designed earlier using the conventional approach (i.e., extensive use of wind tunnel testing). The goal is to use the already low drag vehicle shape and reduce its drag even further using the adjoint methodology without using the time-consuming and the high cost of wind tunnel testing. In addition, the present study is intended to compare the results with the other computational techniques such as surface pressure gradients method.

Understanding the flow characteristics and, especially, how the aerodynamic forces are influenced by the changes in the vehicle body shape, are very important in order to improve vehicle aerodynamics. One specific goal of aerodynamic shape optimization is to predict the local shape sensitivities for aerodynamic forces. The availability of a reliable and efficient sensitivity analysis method will help to reduce the number of design iterations and the aerodynamic development costs. Among various shape optimization methods, the Adjoint Method has received much attention as an efficient sensitivity analysis method for aerodynamic shape optimization because it allows the computation of sensitivity information for a large number of shape parameters simultaneously.

This paper presents some of the challenges and successful outcomes in developing the aerodynamic characteristics of the Chevrolet Volt, an electric vehicle with an extended-range capability. While the Volt's propulsion system doesn't directly affect its shape efficiency, it does make aerodynamics much more important than in traditional vehicles. Aerodynamic performance is the second largest contributor to electric range, behind vehicle mass. Therefore, it was critical to reduce aerodynamic drag as much as possible while maintaining the key styling cues from the original concept car. This presented a number of challenges during the development, such as evaluating drag due to underbody features, balancing aerodynamics with wind noise and cooling flow, and interfacing with other engineering requirements. These issues were resolved by spending hundreds of hours in the wind tunnel and running numerous Computational Fluid Dynamics (CFD) analyses.

An air suspension system can consist of many different components. These components include an air compressor, air springs, pneumatic solenoid valves, height sensors, electronic control unit, air reservoir, air lines, pressure sensor, temperature sensor, etc. The system could be designed as a 2-corner rear air suspension or a 4-corner air suspension. In this paper, the pneumatic models of air suspension systems are presented. The suspension system models are implemented in AmeSim. The suspension controls are implemented using Matlab/Simulink. The compressor was modeled using the standard AmeSim element with known mass flow rate as a function of pressure ratio. Air lines were modeled using a friction submodel of pneumatic pipe and control (isolation) valves are modeled using 2 position, 2 port pneumatic servo valves. The air spring is modeled as a single pneumatic chamber, single rod jack with spring assistance to account for spring nonlinearities.

A comprehensive analysis has been performed for floating bearings applied in a turbocharger. It is found that Couette power loss for a full-floating bearing (the floating ring rotates) decreases with increasing inner and outer clearances, while its Poiseuille power loss increases with increasing inner and outer film clearances. In comparison with a semi-floating bearing (the floating ring does not rotate), a full-floating bearing can reduce both Couette and Poiseuille power losses. However, floating bearing is found to have a smaller minimum film thickness for a given dynamic loading from rotor-dynamics. The total power loss reduction for typical full-floating bearings ranges from 13% to 27%, which matches well with some published experimental data. In general, the speed ratio increases with increasing outer film clearance, while it decreases with increasing inner film clearance because of shear stresses on the outer and inner film.

Presented in the paper is a comprehensive analysis for floating piston pin. It is more challenging because it is a special type of journal bearing where the rotation of the journal is coupled with the friction between the journal and the bearing. In this analysis, the multi-degree freedom mass-conserving mixed-EHD equations are solved to determine the coupled pin rotation and friction. Other bearing characteristics, such as minimum film thickness, pin secondary motions in both connecting-rod small-end bearing and piston pin-boss bearing, power loss etc are also determined. The mechanism for floating pin to have better scuffing resistance is discovered. The theoretical and numerical model is implemented in the GM internal software FLARE (Friction and Lubrication Analysis for Reciprocating Engines).

Diesel engine developers are continually striving to reduce harmful NOx emissions through various calibration and hardware strategies. One strategy being implemented in production Diesel engines involves utilizing cooled exhaust gas recirculation (EGR). Although there is a significant NOx reduction potential by utilizing cooled EGR, there are also several issues associated with it, such as EGR cooler fouling and a reduction in cooler effectiveness that can occur over time. The exact cause of these issues and many others related to cooler fouling are not clearly understood. One such unanswered issue or phenomenon that has been observed in both field tested and lab tested EGR coolers is that of a recovery in EGR cooler effectiveness after a shutdown or after cycling between various conditions.

The present paper describes the results of a research project aimed at studying the impact of nozzle flow number on a Euro5 automotive diesel engine, featuring Closed-Loop Combustion Control. In order to optimize the trade-offs between fuel economy, combustion noise, emissions and power density for the next generation diesel engines, general trend among OEMs is lowering nozzle flow number and, as a consequence, nozzle hole size. In this context, three nozzle configurations have been characterized on a 2.0L Euro5 Common Rail Diesel engine, coupling experimental activities performed on multi-cylinder and optical single cylinder engines to analysis on spray bomb and injector test rigs. More in detail, this paper deeply describes the investigation carried out on the multi-cylinder engine, specifically devoted to the combustion evolution and engine performance analysis, varying the injector flow number.

The sustainable use of energy and the reduction of pollutant emissions are main concerns of the automotive industry. In this context, Hybrid Electric Vehicles (HEVs) offer significant improvements in the efficiency of the propulsion system and allow advanced strategies to reduce pollutant and noise emissions. The paper presents the results of a simulation study that addresses the minimization of fuel consumption, NOx emissions and combustion noise of a medium-size passenger car. Such a vehicle has a parallel-hybrid diesel powertrain with a high-voltage belt alternator starter. The simulation reproduces real-driver behavior through a dynamic modeling approach and actuates an automatic power split between the Internal Combustion Engine (ICE) and the Electric Machine (EM). Typical characteristics of parallel hybrid technologies, such as Stop&Start, regenerative braking and electric power assistance, are implemented via an operating strategy that is based on the reduction of total losses.

Today, nearly half of the world population lives in urban areas. As the world population continues to migrate to urban areas for increased economic opportunities, addressing personal mobility challenges such as air pollution, Greenhouse Gases (GHGs) and traffic congestion in these regions will become even a greater challenge especially in rapidly growing nations. Road transportation is a major source of air pollution in urban areas causing numerous health concerns. Improvements in automobile technology over the past several decades have resulted in reducing conventional vehicle tailpipe emissions to exceptionally low levels. This transformation has been attained mainly through advancements in engine and transmission technologies and through partial electrification of vehicles. However, the technological advancements made so far alone will not be able to mitigate the issues due to increasing GHGs and air pollution in urban areas.

General Motor's new front wheel drive six speed 6T40 automatic transmission benefits from patented technology to control high speed pump cavitation that is innovative yet cost effective. An annular nozzle is created with careful pump inlet design by integrating a conical section in the filter neck to create a jet pump to prevent high speed cavitation for almost no additional cost. Excess oil from a fixed displacement pump is used to achieve an effective increase in pressure at the inlet of the rotating group during high speed operation. Control of high speed cavitation reduces pump noise and improves line pressure control stability.

The internal flow in an injector is greatly affected by cavitation formation, and this in turn impacts the spray characteristics of diesel injectors. In the current work, the performance of the Homogeneous Relaxation Model (HRM) in simulating cavitation inside a diesel injector is evaluated. This model is based on the assumption of homogeneous flow, and was originally developed for flash boiling simulations. However, the model can potentially simulate the spectrum of vaporization mechanisms ranging from cavitation to flash boiling through the use of an empirical time scale which depends on the thermodynamic conditions of the injector fuel. A lower value of this time scale represents a lower deviation from thermal equilibrium conditions, which is an acceptable assumption for small-scale cavitating flows. Another important advantage is the ability of this model to be easily coupled with real fuel models.

The achievable shift quality of a modern automatic transmission may be greatly affected by the equivalent rotational inertia of the gearbox and driveline components. New, more mass- and packaging-efficient higher number of gear powerflows are being developed. These new architectures often result in more components being attached to a given rotational node. The rotational speed multiplication of the components must be considered when determining their inertial torque contribution to a given speed change event. An example of this multiplication effect is presented, with a discussion of the resulting impact to shift quality disturbance. Opportunities to address the negative aspects of the higher inertial torque contribution to transmission output shaft disturbance are discussed. Coordination of engine torque control and clutch torque control is presented as a viable strategy to improve shift quality.

For many years, the computer aided math model has been the foundation for lowering cost and reducing time to market for many manufacturing industries. The automotive industry applies a variety of tools and methods to evaluate the expected vehicle performance to a forever expanding set of requirements. These mathematical predictions of performance are then repeated for both a set of design cycles and a multitude of vehicles in the product portfolio. This paper presents a CAE perspective of the unique problems of the large scale virtual vehicle engineering factory and a set of solutions. Different strategies to create the various complex math models required are explored. These strategies include using COTS FEA pre-processers, producing FEA models internal to the CAD tools, as well as custom built tools, macros and process automation tools.