TABLE OF CONTENTS In recent years engine modeling has become more and more important in the development process. In an early development stage new strategies can be examined without expensive test bench measurements. Further on, control strategies can be designed and optimized. Thereby new requirements for the models arise.
Multiple direct fuel injection in diesel engines
Direct fuel injection was a breakthrough for diesel engines. By means of multiple injections in common rail systems, the evaporation process and subsequently the combustion process can be directly influenced.
Stratified charge in SI engines
As explained in Section 5.1, SI engines work with a homogeneous air-fuel mixture at stoichiometric air-fuel ratios because the catalytic converter shows extremely good conversion rates under such conditions. At part load, directly injected SI engines work with lean air-fuel mixtures. In order to get a safe combustion a stratified charge is assembled around the spark plug. In such engines the charge exchange, turbulences inside the combustion chamber and the injection process must be modeled.
Exhaust gas calculation
One of the major problems is to model the exhaust gas generation fairly accurate. The maximum allowable emissions are determined by law. In order to meet such regulations two strategies are pursued in parallel. One is to minimize the raw emissions of noxious gases from the combustion process. The other is to clean the exhaust gases by means of catalytic after treatment systems. Both strategies need sophisticated control systems and dynamic models of the chemical processes involved.
Because of the rising importance of...
