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Powertrains for commercial vehicles have evolved since the late nineteenth-century invention of the ICE. In the revised second edition of Advanced Hybrid Powertrains for Commercial Vehicles, the authors explore commercial powertrains through history from the ICE through the introduction of the hybrid powertrain in commercial vehicles. Readers are given an understanding of the ICE as well as the classification of commercial vehicle hybrid powertrains, the variety of energy storage systems, fuel-cell hybrid powertrain systems, and commercial vehicle electrification. The authors review the legislation of vehicle emissions and the regulation necessary to promote the production of fuel-efficient vehicles.

Vehicle electrification is being actively expanded into coming generations of passenger and commercial vehicles. This technology trend is helping vehicles to become more energy efficient. For electric vehicle (EV) city bus application, the system designers have been experimenting with a number of options including direct drive and multi-speed gearbox architectures. Direct drive scenario offers simplified drivetrain system, however requires a large and powerful electric motor. Multi-speed transmission system provides an opportunity to reduce motor size and optimize its operating points, but increases complexity from the architecture and controls point of view. This paper provides an overview of several common system layouts and examines their advantages and disadvantages. Vehicle simulation results are presented to compare direct drive vs. multi-speed technology from the gradeability, acceleration and energy consumption points of view.

This book provides a broad and comprehensive look at hybrid powertrain technologies for commercial vehicles. It begins with the fundamentals of hybrid powertrain systems, government regulations, and driving cycles, then provides design guidelines and key components of hybrid powertrains for commercial vehicles. It was written for vehicle and component engineers and developers, researchers, students, policymakers, and business executives in the commercial vehicle and transportation industries to help them understand the fundamentals of hybrid powertrain technologies and market requirements for commercial vehicles. It is useful for anyone who designs or is interested in hybrid powertrains and their key components. The term ‘commercial vehicle’ applies to everything from light delivery vehicles to class 8 long haul trucks, buses, and coaches. These vehicles are used for a wide range of duties, including transporting goods or people and infrastructure service.

On-board measurements of fuel consumption and vehicle exhaust emissions of NOx, HC, CO, CO2, and PM are being conducted for three types of commercially available city buses in Guangzhou, China. The selected vehicles for this test include a diesel bus with Eaton hybrid electric powertrain, a conventional diesel bus with automated mechanical transmission (AMT), and a LPG powered city bus with manual transmission (MT). All of the tested vehicles were instrumented with on-board measurements. Horiba OBS-2200 was used for measuring NOx, HC, and CO emissions; ELPI (Electrical Low Pressure Impactor) was used for PM measurement. The vehicles were tested at Hainan National Proving Ground in southern China. Test data of fuel consumption and exhaust emissions were analyzed. The city bus with Eaton hybrid electric powertrain demonstrated more than 27% fuel consumption reduction over the conventional diesel powered bus, and over 68% over the LPG bus.

This paper describes a NOx aftertreatment system and control strategy for heavy-duty diesel engines to achieve US EPA 2010 emissions regulations. The NOx aftertreatment system comprises of a fuel reformer catalyst, a LNT catalyst, and a SCR catalyst. The only reductant required to operate this system is diesel fuel; hence, no urea infrastructure is required to support this approach. The fuel reformer is used to generate reformate which is a combination of hydrogen, carbon monoxide and unburned hydrocarbons. This reformate provides a more efficient feedstock to improve LNT NOx regeneration efficiency. Engine out NOx is reduced using a two-step process. First, NOx is stored in the LNT catalyst during lean operation. During rich operation, portions of the stored NOx are converted to nitrogen and ammonia. Next, the ammonia released from the LNT is captured by the downstream SCR catalyst. The stored ammonia is further used to reduce the NOx that slips past the LNT catalyst.

The conventional diesel engine retarder is an add-on system that converts the power producing diesel engine into a power absorber by altering engine valve timing when vehicle retarding is desired. The retarding effect is achieved by releasing the compressed air charge near TDC compression to prevent energy from returning to the engine during expansion. Retarding performance is optimized only at one engine speed and the increased height due to the add-on approach is a disadvantage for some vehicle applications. This study introduces an integrated Variable Valve Timing (VVT) engine retarder (Figure 1) by applying the lost motion principle. The integrated retarding system has significant dimensional advantage over the conventional add-on engine retarder. The lost motion VVT retarder also provides optimized retarding performance over the entire engine operating range.

Variable Valve Actuation has been researched and applied to improve engine fuel economy and emissions. The effect on compression release engine retarding has not been considered. Heavy duty diesel engines are recognized for their ability to function as effective vehicle retarders. Many approaches have been taken to convert the power producing diesel engine into a power absorber by altering air flow management. Compression release diesel engine retarding is generated by altering engine valve timing when braking is desired. By releasing the compressed air charge at near TDC compression, the energy absorbed is prevented from returning to the engine during expansion. The net energy loss provides the braking effect. This study discusses the parameters used in system design to achieve maximum performance by using variable valve actuation, VVA, to produce the brake event. Retarding power potential is evaluated by cycle analysis for each system and supported by engine test data.

Diesel engine retarder performance varies as environment conditions change. An understanding of the mechanisms that produce this variance is gained through analytical consideration of ambient temperature, pressure and air moisture content. Retarding performance is quantified in an analytical model sensitive to these ambient parameters and their effect on system operating efficiency. Computer simulation is used to study the impact of ambient parameters on the turbocharged diesel engine and the compression release engine brake for a wide range of operating environments. Correlation with road performance is made to illustrate environment impact on maintained heavy vehicle downhill road speed.

Measurements of explosion limits for fuel/air/diluent mixtures compressed by an expanding laminar flame have been made in a constant volume spherical bomb. The fuels studied to date range from butane to octane at fuel/air equivalence ratios from 0.8 to 1.3. The explosion pressures and temperatures range from 10 to 100 atm and 650 to 850 K. The pressure versus time curves show the behavior typical of the two-stage ignition process observed in rapid compression machines. A branched chain kinetic model has been developed to correlate the data. The model has been used to predict both the explosion limits measured in the current bomb experiments and ignition delays measured in prior rapid compression machine experiments. Good agreement between experiment and theory can be achieved with minor adjustment in published rate constants.