Modeling of Flame Propagation and Energy Conversion Rates in SI Engines 830331

In this paper a thermal model for flame propagation in preraixed homogeneous charges is developed which is based on real physical properties of engine and fuel. It is applied to engine cycle simulations of a model engine. The flame propagation model has been successfully used already to analyze ignition problems and engine knock. Here it will be shown that this flame propagation model is capable also of correctly predicting all the known dependencies of the cylinder pressure on fuel-air-ratio, compression ratio, spark timing, EGR, fuel properties, etc. which are observable on engines both with respect to magnitude and tendency of the corresponding changes. The results of extensive parametric studies with this model are presented along with details of the model calculation. The predictions are compared to real engine data taken both from established literature and from own engine work. From the very good agreement between predicted and measured dependencies it is concluded that the proposed model is a very useful tool for guiding research work.