A Transport Equation Residual Model Incorporating a Damkohler Criterion for Predicting the Flame Propagation in Gasoline Direct Injection Engines

A transport equation residual model incorporating a Damkohler criterion has been developed and implemented in the ERC KIVA-3V code for Gasoline Direct Injection (GDI) engine simulations for better predictions of flame propagation. In the transport equation residual model a fictitious species concept is introduced to account for the residual gases in the cylinder, which have a great effect on the laminar flame speed. The residual gases include CO2, H2O and N2 remaining from the previous engine cycle or introduced using EGR. This pseudo species is described by a transport equation. The transport equation residual model differentiates between CO2 and H2O from the previous engine cycle or EGR and which is from the combustion products of the current engine cycle. In addition a Damkohler criterion, which determines whether the G-equation model or chemical kinetics should be used for assessing the combustion processes in flame-containing cells is introduced. The criterion is based on a comparison between a laminar flame propagation time scale and the chemical kinetics time scale. The integrated model was used to simulate the combustion process in a Gasoline Turbocharged Direct Injection (GTDI) engine, and the same set of combustion model parameters for both high load and low load were used. For both high load and low load operating conditions, good agreement with experimental in-cylinder pressure, heat release rates and Mass Fraction Burned (MFB) data was obtained.