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The combustion process of a heavy-duty DI-Diesel truck engine has been investigated using numerical simulation. The numerical modeling was based on an improved version of the KIVA-2 engine simulation code, employing a modified characteristic time-scale combustion model and a modified Kelvin-Helmholtz spray atomization model. The NO-formation process was modeled using the extended thermal Zeldovich mechanism. The simulation efforts included the effects of different injection characteristics such as varying the injection rate profile or number of injection holes and sizes. The physical sub-models used to improve the simulation of the mixture-formation and the combustion process were validated through comparison with single-cylinder engine experiments. Special attention was given to accurately model the in-cylinder flame propagation of the individual sprays and their effect on thermal NO-formation. All simulations were based on full load cases at medium speed.

The application of statistical analysis methods and simulation techniques through the concept stages of a truck engine development process, in order to assist with decision making, is reported in this paper. Aspects of single cylinder engine, combustion system development and the subsequent use of modelling and simulation, to predict multi-cylinder engine behaviour, is described. Finally, the inclusion of vehicle commercial and operational information is shown to provide insights into the likely mix of technical strategies for future truck engines in the UK vehicle parc. It is seen that, in the near future especially in Europe, the likely solution for truck engines will be a mix of EGR and SCR techniques both of which will include the use of particulate filtration. However, the extent of the commercially viable application of this strategy is very dependent upon likely future market prices for the various aftertreatment and fuel technologies.

For the development of new HD Diesel engines which meet the demands of future international emission regulations and, at the same time, ensure economic operation modern development tools need to be used, especially for an optimisation of the combustion principle. To find the optimal engine set up, the variation of a large number of engine and injection system parameters, i.e. injection system, number of nozzle holes and sizes, injection rate profiles, etc. is required. To speed up the design process, modern optical engine diagnostics and 3D-numerical simulation can help to analyse the highly transient in-cylinder processes in detail. These methods provide essential insight to understand the complicated physical and chemical interactions and acting mechanisms during mixture formation, combustion and pollutant formation as well as the function of components of the system.