Development of an engine simulation program and its application to stratified charge SI engines

The paper presents the development of an engine simulation program and its application to the analysis of a spark ignition (SI) engine with stratified charge. The engine simulation program has been developed to predict engine combustion, auto-ignition, performance and emissions. Full NOx formation i s included in the model with a refined method to calculate the equilibrium burnt gas composition. To predict the onset of knocking combustion, an auto -ignition model involving 31 different chemical reactions is included. The thermodynamic and auto-ignition models are coupled through cylinder pressur e and unburned gas temperature. The inclusion of a geometry sub-model permi ts the modelling of SI engines with complicated cylinder head geometry. The model was then applied to a SI engine with stratified fuel or diluent. The effects of the charge stratification on engine's combustion, performance a nd emissions are discussed.