Modeling Ignition and Combustion in Spark-ignition Engines Using a Level Set Method

An improved discrete particle ignition kernel (DPIK) model and the G-equation combustion model have been developed and implemented in KIVA-3V. In the ignition model, the spark ignition kernel growth is tracked by Lagrangian markers and the spark discharge energy and flow turbulence effects on the ignition kernel growth are considered. The predicted ignition kernel size was compared with the available measurements and good agreement was obtained. Once the ignition kernel grows to a size where the turbulent flame is fully developed, the level set method (G-equation) is used to track the mean turbulent flame propagation. It is shown that, by ignoring the detailed turbulent flame brush structure, fine numerical resolution is not needed, thus making the models suitable for use in multidimensional modeling of SI engine combustion. To test the ignition and combustion models, they were applied to a homogeneous charge pancake geometry-combustion-chamber engine for which experimental heat flux data from probes in the engine head and cylinder liner was available. By comparing the flame arrival timings with the simulations, the ignition and combustion models were validated. In addition, the models were also applied to a homogenous charge Caterpillar converted propane-fueled engine. Good agreement with experimental cylinder pressures and NOx data was obtained as a function of ignition timing, engine speed and EGR levels.