Improvements to Combustion Models for Modeling Spark-Ignition Engines Using the G-equation and Detailed Chemical Kinetics 2008-01-1634

Improvements to combustion models for modeling spark ignition engines using the G-equation flame propagation model and detailed chemical kinetics have been performed. The improvements include revision of a PRF chemistry mechanism, precise calculation of “primary heat release” based on the sub-grid scale unburned/burnt volumes of flame-containing cells, modeling flame front quenching in highly stratified mixtures, introduction of a Damkohler model for assessing the combustion regime of flame-containing cells, and a better method of modeling the effects of the local residual value on the burning velocity. The validation of the revised PRF mechanism shows that the calculated ignition delay matches shock tube data very well. The improvements to the “primary heat release” model based on the cell unburned/burnt volumes more precisely consider the chemical kinetics heat release in unburned regions, and thus are thought to be physically reasonable. The simulation results show that the flame front quenching model effectively captures the flame quench phenomenon in highly stratified mixtures which are typical in Gasoline Direct Injection (GDI) engines. The results from implementation of the Damkohler model range between the G-equation model and pure CHEMKIN, depending on the conditions. Finally, an improved method is proposed to calculate the effects of local residual values on flame speed. After using these combined improvements to the combustion model, calibrations from high load to low load were applied to a Gasoline Turbocharged Direct Injection (GTDI) engine, and the same set of combustion model parameters for both high load and low load were used. The calibration results show that the simulated pressure, heat release rate, and Mass Fraction Burned (MFB) match the experimental data very well.