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For the conventional 6 speed automatic transmission with engine stop-start powertrain, an electrically-driven auxiliary pump is implemented to maintain the transmission line pressure as required to lock-up the CB1234 clutch during engine auto-stop conditions. Upon releasing the brake pedal, the transmission engages into first gear with the objective to accelerate the vehicle in a responsive manner. In this study, a novel normally-engaged dual-piston clutch concept is designed to keep the CB1234 clutch locked-up during engine auto-stop conditions with the intention to eliminate the auxiliary pump without compromising vehicle performance. This dual piston clutch concept requires a relatively low line pressure to release the normally-engaged clutch when needed, thus, minimizing the hydraulic pumping work. To explore the functionality of this concept under a wide-open-throttle (WOT) auto-start transition, modeling and simulation of the normally-engaged dual-piston clutch is completed.

The electric vehicle on-board charger (OBC) is responsible for converting AC grid energy to DC energy to charge the battery pack. This paper describes the development of GM’s second generation OBC used in the 2016 Chevrolet Volt. The second generation OBC provides significant improvements in efficiency, size, and mass compared to the first generation. Reduced component count supports goals of improved reliability and lower cost. Complexity reduction of the hardware and diagnostic software was undertaken to eliminate potential failures.

By analyzing the dynamic distortion in all body closure openings in a complete vehicle, a better understanding of the body characteristics can be achieved compared to traditional static load cases such as static torsional body stiffness. This is particularly relevant for non-traditional vehicle layouts and electric vehicle architectures. The body response is measured with the so-called Multi Stethoscope (MSS) when driving a vehicle on a rough pavé road (cobble stone). The MSS is measuring the distortion in each opening in two diagonals. During the virtual development, the distortion is described by the relative displacement in diagonal direction in time domain using a modal transient analysis. The results are shown as Opening Distortion Fingerprint ODF and used as assessment criteria within Solidity and Perceived Quality. By applying the Principal Component Analysis (PCA) on the time history of the distortion, a Dominant Distortion Pattern (DDP) can be identified.

This work analyzes the lubricant supply to critical regions of needle roller bearing of an automatic transmission. The needle roller bearing is a critical component of an automatic transmission and it has several rotating cylindrical needle rollers that are having relative motion with inner surface of the pinion. Supply of lubricant to the needle roller bearings is very essential to prevent failure of the bearings due to frictional contact between rollers and inner surface of pinion. The supply of lubricant to the needle roller bearings depends on the location of oil supply hole. Lubricant supply to the needle roller bearings of an automatic transmission is studied using commercial 3D Computational Fluid Dynamics (CFD) software for different oil supply positions. CFD simulation is performed for the region between the pinion supply hole and end of the needle bearings including all needles. Lubricant is supplied to the needle bearing from the pinion pin oil supply hole.

A computational, three-dimensional approach to investigate the behavior of diesel soot particles in the micro-channels of wall-flow Diesel Particulate Filters is presented. The KIVA3V CFD code, already extended to solve the 2D conservation equations for porous media materials [1], has been enhanced to solve in 2-D and 3-D the governing equations for reacting and compressible flows through porous media in non axes-symmetric geometries. With respect to previous work [1], a different mathematical approach has been followed in the implementation of the numerical solver for porous media, in order to achieve a faster convergency as source terms were added to the governing equations. The Darcy pressure drop has been included in the Navier-Stokes equations and the energy equation has been extended to account for the thermal exchange between the gas flow and the porous wall.

Direct-injection technology represents today a very interesting solution to the typical problems that are generally encountered in SI, gas-fueled engines such as reduced volumetric efficiency, backfire and knock. However, development of suitable injection systems and combustion chamber geometry is necessary to optimize the fuel-air mixing and combustion processes. To this end, CFD models are widely applied even if the influence of the mesh structure, numerical and turbulence models on the computed results are still matter of investigation. In this work, a numerical methodology for the simulation of the gas exchange and injection processes in gas-fueled engines was developed within the Lib-ICE framework, which is a set of libraries and applications for IC engine modeling developed using the OpenFOAM® technology. The gas exchange and fuel injection processes were simulated into a four-valve, pent-roof hydrogen-fueled engine with optical access.

Premixed combustion modes in compression ignition engines are studied as a promising solution to meet fuel economy and increasingly stringent emissions regulations. Nevertheless, PCCI combustion systems are not yet consolidated enough for practical applications. The high complexity of such combustion systems in terms of both air-fuel charge preparation and combustion process control requires the employment of robust and reliable numerical tools to provide adequate comprehension of the phenomena. Object of this work is the development and validation of suitable models to evaluate the effects of charge premixing levels in diesel combustion. This activity was performed using the Lib-ICE code, which is a set of applications and libraries for IC engine simulations developed using the OpenFOAM® technology.

The selective catalytic reduction has seen widespread adoption as the best technology to reduce the NOx emissions from internal combustion engines, particularly for Diesels. This technology uses ammonia as a reducing agent, which is obtained injecting an ammonia carrier into the exhaust gas stream. The dosing of the ammonia carrier, usually AdBlue, is the major concern during the design and engine calibration phases, since the interaction between the injected liquid and the components of the exhaust system can lead to the undesired formation of solid deposits. To avoid this, the thermal and kinematic interaction between the spray and the components of the after treatment system (ATS) must be modeled accurately. In this work, the authors developed a Conjugate Heat Transfer (CHT) framework to model the kinetic and thermal interaction among the spray, the eventual liquid layer and the pipe walls.

Cycle-To-Cycle Variability (CCV) must be properly considered when modeling the ignition process in SI engines operating with ultra-lean mixtures. In this work, a strategy to model the impact of the ignition type on the CCV was developed using the RANS approach for turbulence modelling, performing multi-cycle simulations for the power-cycle only. The spark-discharge was modelled through a set of Lagrangian particles, introduced along the sparkgap and interacting with the surrounding Eulerian gas flow. Then, at each discharge event, the velocity of each particle was modified with a zero-divergence perturbation of the velocity field with respect to average conditions. Finally, the particles velocity was evolved according to the Simplified Langevin Model (SLM), which keeps memory of the initial perturbation and applies a Wiener process to simulate the stochastic interaction of each channel particle with the surrounding gas flow.

In the most elementary treatment of plane-wave reflection at the open end of a duct system, it is often assumed that the ends are pressure nodes. This implies that pressure is assumed as a constant at the open end termination and that steady flow boundary condition is supposed as instantaneously established. While this simplifying assumption seems reasonable, it does not consider any radiation of acoustic energy from the duct into the surrounding free space; hence, an error in the estimation of the effects of the flow on the acoustical response of an open-end duct occurs. If radiation is accounted, a complicated three-dimensional wave pattern near the duct end is established, which tends to readjust the exit pressure to its steady-flow level. This adjustment process is continually modified by further incident waves, so that the effective instantaneous boundary conditions which determine the reflected waves depend on the flow history.

Many new combustion concepts are currently being investigated to further improve engines in terms of both efficiency and emissions. Examples include homogeneous charge compression ignition (HCCI), lean stratified premixed combustion, stratified charge compression ignition (SCCI), and high levels of exhaust gas recirculation (EGR) in diesel engines, known as low temperature combustion (LTC). All of these combustion concepts have in common that the temperatures are lower than in traditional spark ignition or diesel engines. To further improve and develop combustion concepts for clean and highly efficient engines, it is necessary to develop new computational tools that can be used to describe and optimize processes in nonstandard conditions, such as low temperature combustion.

Nowadays, detailed kinetics is necessary for a proper estimation of both flame structure and pollutant formation in compression ignition engines. However, large mechanisms and the need to include turbulence/chemistry interaction introduce significant computational overheads. For this reason, tabulated kinetics is employed as a possible solution to reduce the CPU time even if table discretization is generally limited by memory occupation. In this work the authors applied tabulated homogeneous reactors (HR) in combination with different turbulent-chemistry interaction approaches to model non-premixed turbulent combustion. The proposed methodologies represent good compromises between accuracy, required memory and computational time. The experimental validation was carried out by considering both constant-volume vessel and Diesel engine experiments.

Objective of this work is the incorporation of the flame stretch effects in an Eulerian-Lagrangian model for premixed SI combustion in order to describe ignition and flame propagation under highly inhomogeneous flow conditions. To this end, effects of energy transfer from electrical circuit and turbulent flame propagation were fully decoupled. The first ones are taken into account by Lagrangian particles whose main purpose is to generate an initial burned field in the computational domain. Turbulent flame development is instead considered only in the Eulerian gas phase for a better description of the local flow effects. To improve the model predictive capabilities, flame stretch effects were introduced in the turbulent combustion model by using formulations coming from the asymptotic theory and recently verified by means of DNS studies. Experiments carried out at Michigan Tech University in a pressurized, constant-volume vessel were used to validate the proposed approach.

Ducted Fuel Injection (DFI) has the potential to reduce soot emissions in Diesel engines thanks to the enhanced mixing rate resulting from the liquid fuel flow through a small cylindrical pipe located at a certain distance from the nozzle injector hole. A consolidated set of experiments in constant-volume vessel and engine allowed to understand the effects of ambient conditions, duct geometry and shape on fuel-air mixing, combustion and soot formation. However, implementation of this promising technology in compression-ignition engines requires predictive numerical models that can properly support the design of combustion systems in a wide range of operating conditions. This work presents a computational methodology to predict fuel-air mixing and combustion with ducted fuel injection. Attention is mainly focused on turbulence and combustion modelling.

To improve torque management algorithms for drivability, the powertrain controller must be able to compensate for the nonlinear dynamics of the driveline. In particular, the presence of backlash in the transmission and drive shafts excites sharp torque fluctuations during tip-in or tip-out transients, leading to a deterioration of the vehicle drivability and NVH. This paper proposes a model-based estimator that predicts the wheel torque in an automotive drivetrain, accounting for the effects of backlash and drive shaft flexibility. The starting point of this work is a control-oriented model of the transmission and vehicle drivetrain dynamics that predicts the wheel torque during tip-in and tip-out transients at fixed gear. The estimator is based upon a switching structure that combines a Kalman Filter and an open-loop prediction based on the developed model.

The need to reduce fuel consumption and harmful pollutants from engines is an important task for automotive industry. It has led to technological advances in new engine design, such as engine downsizing. Due to the reduction of displacement, engine power output is reduced and thus its overall performance is limited. In order to increase torque and power, engines are typically boosted by turbochargers or superchargers. Meanwhile, the improvement on turbo design makes it possible to operate VGT (variable geometry turbocharger) at harsher exhaust environment for gasoline engines as well (e.g., with much higher exhaust temperature than that of diesel engines). This makes VGT related control problems more challenging and requires attention to protecting corresponding engine hardware during an entire engine life.

Aqueous Urea is a non-toxic and stable ammonia carrier and its injection and mixing represent the basis for the most common de-NOx technology for mobile applications. The reactant feed preparation process is defined by evaporation, thermolysis and hydrolysis of the liquid mixture upstream the Selective Catalytic Reduction reactor, and it is strongly dependent on the interaction between spray and gaseous flow. Low-pressure driven injectors are the common industrial standard for these applications, and their behavior in almost-ambient pressure cross flows is significantly different from any in-cylinder application. For this reason, two substantially different injectors in terms of geometry and design are experimentally studied, characterizing drop sizes and velocities through Phase Doppler Anemometry (PDA) and liquid mass spatial distribution through Shadow Imaging (SI).

Traditional vehicle air conditioning systems condition the entire cabin to a comfortable range of temperature and humidity regardless of the number of passengers in the vehicle. The A/C system is designed to have enough capacity to provide comfort for transient periods when cooling down a soaked car. Similarly for heating, the entire cabin is typically warmed up to achieve comfort. Localized heating and cooling, on the other hand, focuses on keeping the passenger comfortable by forming a micro climate around the passenger. This is more energy efficient since the system only needs to cool the person instead of the entire cabin space and cabin thermal mass. It also provides accelerated comfort for the passenger during the cooling down periods of soaked cars. Additionally, the system adapts to the number of passengers in the car, so as to not purposely condition areas that are not occupied.

In the vehicle development process, one important step is to set a component performance target from the vehicle level performance. Conventional barrier-decoupler dash mats and floor trim underlayment systems typically provide sound transmission loss (STL) with minimal absorption. Thus the performance of such components can be relatively easily specified as either STL or Insertion Loss. Lightweight dissipative or multi-layered acoustic materials provide both STL and significant absorption. The net performance is a combination of two parameters instead of one. The target for such components needs to account for this combined effect, however different suppliers use unique formulations and manufacturing methods, so it is difficult and time consuming to judge one formulation against another. In this paper, a unique process is presented to set a component target as a combined effect of STL and absorption.

More Mg alloys are being considered for uses in the automotive industry. Since the corrosion performance of Mg alloy components in practical service environments is unknown, long term corrosion testing at automotive proving grounds will be an essential step before Mg alloy components can be implemented in vehicles. However, testing so many Mg alloy candidates for various parts is labor intensive for the corrosion engineers at the proving grounds. This report presents preliminary results in evaluating corrosion performance of Mg alloys based on rapid corrosion and electrochemical tests in the lab. In this study, four Mg alloy candidates for transmission cases and oil pans: AE44, AXJ530, MRI153M and MRI230D were tested in the lab and at General Motors Corporation Milford Proving Ground and their corrosion results were compared.