Numerical Simulation for Vehicle PowertrainDevelopment

Ground transportation industry has accepted the reality that fast, efficient, and cost effective engine and vehicle development necessitates the use of numerical simulation at every stage of the design process. Within the vehicle powertrain design and development process, three different levels of modelling can generally be found: 1. Detailed modelling: it is performed during the research and early development stages. It is mainly focused on single powertrain components, such as for instance the internal combustion engine or the electric motor of a Hybrid Electric Vehicle (HEV), providing detailed information about their behaviour, while it cannot study the whole system. 2. Software in the Loop (SiL) modelling: it is carried out later in the development cycle but often before production hardware is available. It has a global perspective and it can be used to evaluate vehicle performance. Moreover today SiL becomes popular in control system development, such as for instance in the development of HEVs energy management systems. 3. Hardware in the Loop (HiL) modelling, which is conducted once production controllers are available. Therefore, this chapter will provide a description of different methodologies which can support engineers in each phase of the vehicle powertrain design process. Starting from the description of different modelling approaches, the chapter will then go deeper into the analysis of numerical models for the main powertrain subsystems (such as for instance the internal combustion engine, the electric motors for HEVs, etc.). Finally, two case studies of numerical simulation applied to powertrain development will be presented; the first focused on the evaluation of vehicle performance, paying particular attention to the engine behaviour under transient conditions, the second aiming instead to the assessment of the fuel economy potential of different Hybrid Electric Vehicle architectures.