Spark Ignition Engine Combustion Modeling Using a Level Set Method with Detailed Chemistry

A level set method (G-equation)-based combustion model incorporating detailed chemical kinetics has been developed and implemented in KIVA-3V for Spark-Ignition (SI) engine simulations for better predictions of fuel oxidation and pollutant formation. Detailed fuel oxidation mechanisms coupled with a reduced NO_X mechanism are used to describe the chemical processes. The flame front in the spark kernel stage is tracked using the Discrete Particle Ignition Kernel (DPIK) model. In the G-equation model, it is assumed that after the flame front has passed, the mixture within the mean flame brush tends to local equilibrium. The subgrid-scale burnt/unburnt volumes of the flame containing cells are tracked for the primary heat release calculation. A progress variable concept is introduced into the turbulent flame speed correlation to account for the laminar to turbulent evolution of the spark kernel flame. To test the model, a homogeneous charge propane SI engine was modeled using a 100-species, 539-reaction propane mechanism, coupled with a reduced 9-reaction NOx mechanism for the chemistry calculations. Good agreement with experimental cylinder pressures and NOx data was obtained as a function of spark timing, engine speed and EGR levels. The model was also applied to a stratified charge two-stroke gasoline engine simulations, and good agreement with measured data was obtained.