A Transport Equation Residual Model Incorporating Refined G-Equation and Detailed Chemical Kinetics Combustion Models

A transport equation residual model incorporating refined G-equation and detailed chemical kinetics combustion models has been developed and implemented in the ERC KIVA-3V release2 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 that which is from the combustion products of the current engine cycle. The refined G-equation and detailed chemical kinetics include revision of a PRF chemistry mechanism, and introduction of 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. Validation of the revised PRF mechanism shows that the calculated ignition delay matches shock tube data very well. The Damkohler criterion is based on a comparison between a laminar flame propagation time scale and the chemical kinetics time scale, and the results from implementation of the Damkohler model range between the G-equation model and pure chemistry, depending on the conditions. 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.