Development of a Detailed Ignition Model with Energy Deposition and its Application to Full Engine Simulation

A multi-dimensional model of the spark ignition process for SI engines was developed as a user-defined function (UDF) integrated into the commercial engine simulation software CONVERGE CFD. The model presented in this paper simulates energy deposition from the ignition circuit into the fuel-air mixture inside the cylinder. The model is based on interaction and collision between electrons in the plasma arc and the gas molecules inside the cylinder using parameters from the ignition circuit and gas inside the cylinder. Full engine simulations using CONVERGE CFD with the developed ignition model including the ignition circuit model, arc propagation model, and energy deposition model were performed to evaluate the validity and performance of the model and to compare with the ignition model provided by CONVERGE CFD. Two engines with different characteristics were used for comparison, a low turbulent port fuel injected single-cylinder CFR engine and a high turbulent direct injected engine. Continuous multi-cycle simulations showed cycle-to-cycle variations in both engines. The range of the cycle-to-cycle variation depends on the detailed settings in the ignition model provided by the CONVERGE CFD. Simulations with the developed ignition model showed a range of cycle-to-cycle variation close to the experiment. The developed ignition model simulates the ignition circuit and the energy deposition with circuit parameters and their interaction with the flow field inside the cylinder. This requires less detailed settings from the user and enables more reasonable and physical simulations inside the ignition circuit and around the spark plug.