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Effective design of the lubrication path greatly influences the durability of any transmission system. However, it is experimentally impossible to estimate the internal distribution of the automotive transmission fluid (ATF) to different parts of the transmission system due to its structural complexities. Hybrid vehicle transmission systems usually consist of different types of bearings (ball bearings, thrust bearings, roller bearings, etc.) in conjunction with gear systems. It is a perennial challenge to computationally simulate such complicated rotating systems. Hence, one-dimensional models have been the state of the art for designing these intricate transmission systems. Though quantifiable, the 1D models still rely heavily on some testing data. Furthermore, HEVs (hybrid electric vehicles) desire a more efficient lubrication system compared to their counterparts (Internal combustion engine vehicles) to extend the range of operation on a single charge.

In light-duty direct-injection (DI) diesel engines, combustion chamber geometry influences the complex interactions between swirl and squish flows, spray-wall interactions, as well as late-cycle mixing. Because of these interactions, piston bowl geometry significantly affects fuel efficiency and emissions behavior. However, due to lack of reliable in-cylinder measurements, the mechanisms responsible for piston-induced changes in engine behavior are not well understood. Non-intrusive, in situ optical measurement techniques are necessary to provide a deeper understanding of the piston geometry effect on in-cylinder processes and to assist in the development of predictive engine simulation models. This study compares two substantially different piston bowls with geometries representative of existing technology: a conventional re-entrant bowl and a stepped-lip bowl. Both pistons are tested in a single-cylinder optical diesel engine under identical boundary conditions.

Hybridization is a mainstream technology for automobiles, and its application is rapidly expanding in other fields. Marine propulsion is one such field that could benefit from electrification of the powertrain. In particular, for boats to sail in enclosed waterways, such as harbors, channels, lagoons, a pure electric mode would be highly desirable. The main challenge to accomplish hybridization is the additional weight of the electric components, in particular the batteries. The goal of this project is to replace a conventional 4-stroke turbocharged Diesel engine with a hybrid powertrain, without any penalty in terms of weight, overall dimensions, fuel efficiency, and pollutant emissions. This can be achieved by developing a new generation of 2-Stroke Diesel engines, and coupling them to a state-of-the art electric system. For the thermal units, two alternative designs without active valve train are considered: opposed piston and loop scavenged engines.

The paper presents the main results of a study on the simulation of energy efficient management of on-board electric and thermal systems for a medium-size passenger vehicle featuring a parallel-hybrid diesel powertrain with a high-voltage belt alternator starter. A set of advanced technologies has been considered on the basis of very aggressive fuel economy targets: base-engine downsizing and friction reduction, combustion optimization, active thermal management, enhanced aftertreatment and downspeeding. Mild-hybridization has also been added with the goal of supporting the downsized/downspeeded engine performance, performing energy recuperation during coasting phases and enabling smooth stop/start and acceleration. The simulation has implemented a dynamic response to the required velocity and manual gear shift profiles in order to reproduce real-driver behavior and has actuated an automatic power split between the Internal Combustion Engine (ICE) and the Electric Machine (EM).

As the proliferation of downsized boosted engines continues, it becomes increasingly important to understand how engine and vehicle hardware impact vehicle transient response. Several different methodologies can be used to understand hardware impacts, such as vehicle testing, 0-D vehicle models, and constant engine speed load steps. The next evolution of predicting vehicle transient response is to transition to a system level vehicle analysis by coupling a detailed engine model, utilizing crank angle resolved calculations, with a simple vehicle model. This allows for the evaluation of engine and vehicle hardware effects on vehicle acceleration and the rate of change of vehicle acceleration, or jerk, and the tradeoffs that can be made between the hardware in early program development. By comparing this system level vehicle model to the different methodologies, it can be shown that a system level vehicle analysis allows for higher fidelity evaluations of vehicle transient response.

Electric motor whine is one of the main noise sources of hybrid and electric vehicles. This paper describes a comprehensive analytical and experimental investigation of permanent magnetic electric motor NVH designs focusing on the contribution from torque ripple (TR) and radial forces (RF). A design-of-experiment method is adopted to design and build candidate motors with (i) high TR and high RF; (ii) high TR and low RF; (iii) low TR and high RF and (iv) low TR and low RF. Four prototype motors are built and tested on motor fixtures to measure dynamic stator forces in radial, tangential and axial directions, track dominant motor orders, and estimate motor Operational Deflection Shapes (ODS). Finite-element based electromagnetic and NVH analyses are performed and correlated to test data. Both tests and analyses confirm reducing TR and RF improves motor NVH performance at dominant pole pass orders.

There are a variety of test protocols associated with vehicle fuel economy and emissions testing. As a result, a number of test protocols currently exist to measure axle efficiency and spin loss. The intent of this technical paper is to describe a methodology that uses a singular axle efficiency and spin loss procedure. The data can then be used to predict the effects on vehicle FE and GHG for a specific class of vehicles via simulation. An accelerated break-in method using a comparable energy approach has been developed, and can be used to meet the break-in requirements of different vehicle emission test protocols. A “float to equilibrium” sump temperature approach has been used to produce instantaneous efficiency data, which can be used to more accurately predict vehicle FE and GHG, inclusive of Cold CO2. The “Float to Equilibrium” approach and “Fixed Sump Temperature” approach has been compared and discussed.

Diesel piston bowl geometry can affect turbulent mixing and therefore it impacts heat-release rates, thermal efficiency, and soot emissions. The focus of this work is on the effects of bowl geometry and injection timing on turbulent flow structure. This computational study compares engine behavior with two pistons representing competing approaches to combustion chamber design: a conventional, re-entrant piston bowl and a stepped-lip piston bowl. Three-dimensional computational fluid dynamics (CFD) simulations are performed for a part-load, conventional diesel combustion operating point with a pilot-main injection strategy under non-combusting conditions. Two injection timings are simulated based on experimental findings: an injection timing for which the stepped-lip piston enables significant efficiency and emissions benefits, and an injection timing with diminished benefits compared to the conventional, re-entrant piston.

The purchase of a new automobile is unquestionably a significant investment for most customers, and with this recognition, comes a correspondingly significant expectation for quality and reliability. Amongst automotive systems -when it comes to considerations of reliability - the brakes (perhaps along with the tires) occupy a rarified position of being located in a harsh environment, subjected to continuous wear throughout their use, and are critical to the safe performance of the vehicle. Maintenance of the brake system is therefore a fact of life for most drivers - something that almost everyone must do, yet given the potentially considerable expense, it is something that of great benefit to minimize.

The oil consumption and blow-by are complex phenomena that need to be minimized to meet the ever changing modern emission standards. Oil flows from the sump to the combustion chamber and the blow-by gases flow from the combustion chamber to the crank case. There are several piston rings on the piston, which form a ring-pack. The ring pack has to be efficiently designed to minimize the oil consumption and blow-by. Since it is difficult and extremely costly to conduct experiments on every series of engines to check for the blow-by and oil consumption, a CFD analysis can be performed on the ring pack to study the blow-by and oil-consumption characteristics. In the CFD analysis described here, the region considered is between the compression chamber and the skirt, between the piston (including the rings) and the cylinder liner. The 3D CFD analysis was conducted for the engine running conditions of 5000 rpm and load of 13.5 kPa, for a 2.4L gasoline engine.

There has been an increasing interest in exploring the potential to reduce energy consumption of future connected and automated vehicles. People have extensively studied various eco-driving implementations that leverage preview information provided by on-board sensors and connectivity, as well as the control authority enabled by automation. Quantitative real-world evaluation of eco-driving benefits is a challenging task. The standard regulatory driving cycles used for measuring exhaust emissions and fuel economy are not truly representative of real-world driving, nor for capturing how connectivity and automation might influence driving trajectories. To adequately consider real-world driving behavior and potential “off-cycle” impacts, this paper presents four collaborative evaluation methods: large-scale simulation, in-depth simulation, vehicle-in-the-loop testing, and vehicle road testing.

Hybrid electric vehicles and battery electric vehicles (BEV) use power electronics (PE) devices to convert between high voltage DC power of the battery and other formats of power. These PE components requires operation within certain temperature range, otherwise, overheating causes component as well as vehicle performance degradation. Therefore, a thermal management system is required for PE components. This paper focuses on the design and development of such a PE components thermal control system. The proposed control system is a distributed thermal control system in which all the PE components are placed in series within one cooling loop. The advantage of the proposed control system is its reduced system complexity, energy efficiency and flexibility to add future PE components. In addition, electric control unit (ECU) are utilized so that complex control algorithms can be implemented.

General Motors’ 3rd generation eAssist propulsion systems build upon the experience gained from the 2nd generation 115v system and the 1st generation 36v system. Extensive architectural studies were conducted to optimize the new eAssist system to maintain the performance and fuel economy gains of the 2nd generation 115v system while preserving passenger and cargo space, and reducing cost. Three diverse vehicle applications have been brought to production. They include two similar pickup trucks with 5.3 liter V8 engines and 8 speed transmissions, a 4-door passenger car with 2.5 liter 4 cylinder normally aspirated gasoline engine and a 6-speed automatic transmission, and a crossover SUV with a 2.0-liter turbocharged engine and 9 speed transmission. The key electrification components are a new water cooled induction motor/generator (MG), new water cooled power electronics module, and two major variants of 86v lithium ion battery packs.

In an earlier paper, the authors described how Model-Based System Engineering could be utilized to provide a virtual Hardware-in-the-Loop simulation capability, which creates a framework for the development of virtual ECU software by providing a platform upon which embedded control algorithms may be developed, tested, updated, and validated. The development of virtual ECU software is increasingly valuable in automotive control system engineering because vehicle systems are becoming more complex and tightly integrated, which requires that interactions between subsystems be evaluated during the design process. Variational analysis and robustness studies are also important and become more difficult to perform with real hardware as system complexity increases. The methodology described in this paper permits algorithm development to be performed prior to the availability of vehicle and control system hardware by providing what is essentially a virtual integration vehicle.

Continuously variable transmissions (CVT) provide superior fuel economy by enabling internal combustion engines to operate at their “sweet spots”. However, there is still potential to improve CVT system’s mechanical efficiency, and further enhance vehicle-level fuel economy. In the past, extensive research work has focused on the core continuously variator unit (CVU) that includes pulleys and a belt or chain. Another thread of research has centered on optimization of CVT clamping force control to reduce hydraulic system loss. Nonetheless, to the best of our knowledge, very little research has looked into the planetary gear sets and clutches that enable the CVT system to switch between forward, neutral and reverse gears. The state-of-the-art reverse clutch usually consists of multiple friction and steel plates, and is normally open during all forward driving maneuvers. The relative speed between friction and steel plates is identical to turbine speed, which generate spin loss.

An experimental piston compounded engine was designed with guidance from thermodynamic modeling, then was built and tested to compare the model predictions to measured results. The piston-compounded concept has shown great potential for improvements in efficiency over current state-of-the-art light-duty engines through the use of an efficient second expansion process to more fully recover energy still present in the exhaust gasses, and was further developed into the Downsized Boosted Dilute Combustion, Exhaust Compounded (DBDC+EC) engine presented here. This paper documents some of the more unique design elements of this engine as well as a performance comparison between test data and modeling expectations. Ultimately, an experimental stoichiometric spark-ignited piston compounded engine was designed, five blocks were built, and collectively they were run for thousands of hours.

This article presents experimental results obtained with a disruptive engine platform, designed to maximize the engine efficiency through a synergetic implementation of downsizing, high compression-ratio, and importantly exhaust-heat energy recovery in conjunction with advanced lean/dilute low-temperature type combustion. The engine architecture is a supercharged high-power output, 1.1-liter engine with two-firing cylinders and a high compression ratio of 13.5: 1. The integrated exhaust heat recovery system is an additional, larger displacement, non-fueled cylinder into which the exhaust gas from the two firing cylinders is alternately transferred to be further expanded. The main goal of this work is to implement in this engine, advanced lean/dilute low-temperature combustion for low-NOx and high efficiency operation, and to address the transition between the different operating modes.

The market for electric vehicles and hybrid electric vehicles is expected to grow in the coming years, which is increasing interest in design optimization of electric motors for automotive applications. Under demanding duty cycles, the moving part within a motor, the rotor, may experience varying stresses induced by centrifugal force, a necessary condition for fatigue. Rotors contain hundreds of electrical steel laminations produced by stamping, which creates a characteristic edge structure comprising rollover, shear and tear zones, plus a burr. Fatigue properties are commonly reported with specimens having polished edges. Since surface condition is known to affect fatigue strength, an experiment was conducted to evaluate the effect of sample preparation on tensile and fatigue behavior of stamped specimens. Tensile properties were unaffected by polishing. In contrast, polishing was shown to increase fatigue strength by approximately 10-20% in the range of 105-107 cycles to failure.

Variable valve actuation is a focus to improve fuel efficiency for passenger car engines. Various means to implement early and late intake valve closing (E/LIVC) at lower load operating conditions is investigated. The study uses GT Power to simulate on E/LIVC on a 2.5 L gasoline engine, in-line four cylinder, four valve per cylinder engine to evaluate different ways to achieve Atkinson cycle performance. EIVC and LIVC are proven methods to reduce the compression-to-expansion ratio of the engine at part load and medium load operation. Among the LIVC strategies, two non-traditional intake valve lift profiles are investigated to understand their impact on reduction of fuel consumption at low engine loads. Both the non-traditional lift profiles retain the same maximum lift as a normal intake valve profile (Otto-cycle) unlike a traditional LIVC profile (Atkinson cycle) which needs higher maximum lift.

With continued industry focus on reducing parasitic transmission and driveline losses, detailed studies are required to quantify potential enablers to improve vehicle fuel economy. Investigations were undertaken to understand the influence of lower viscosity Automatic Transmission Fluids (ATF) on transmission efficiency as compared with conventional fluids. The objectives of this study were to quantify the losses of lower viscosity ATF as compared with conventional ATF, and to understand the influence of ATF properties including viscosities, base oil types, and additive packages on fuel efficiency. The transmission efficiency investigations were conducted on a test bench following a vehicle-based break-in of the transmission using a prescribed drive cycle on a chassis dynamometer. At low temperature, the lower viscosity ATF showed a clear advantage over the conventional ATF in both spin loss and loaded efficiency evaluations.