Modeling Premixed and Direct Injection SI Engine Combustion Using the G-Equation Model

A level set G-equation model has been developed to model the combustion process in spark ignition engines. The spark ignition process was modeled using an improved version of the Discrete Particle Ignition Kernel (DPIK) model. The two models were implemented into the KIVA-3V code to simulate SI engine combustion under both premixed and direct injection conditions. In the ignition model, the ignition kernel growth is tracked by Lagrangian markers, and spark discharge energy and flow turbulence effects on the kernel growth are considered. Once the ignition kernel grows to a size where the turbulent flame is fully developed, the G-equation model is used to track the mean turbulent flame evolution. When combined with a characteristic time scale combustion model, the models were also used to simulate stratified combustion in DISI engines, where the triple flame structure must be considered. It is shown that, by ignoring the detailed turbulent flame brush structure, fine numerical resolution is not required, thus making the models suitable for use in multidimensional modeling of SI engine combustion. The models were applied to a homogenous charge SI engine using propane fuel. Good agreement with experimental cylinder pressure and NOx data was obtained as a function of ignition timing, engine speed and EGR level. In addition, reasonably good agreement was also obtained when the models were coupled with a hollow cone spray model to simulate the combustion process in a direct-injection gasoline engine.

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