Abstract
In this paper, we aim to develop a comprehensive ignition model for three-dimensional (3D) computational fluid dynamics (CFD) combustion modeling in spark-ignited (SI) engines. In the proposed model, we consider the following aspects separately to model the spark ignition process comprehensively. An electrical circuit is solved for calculation of the energy transferred to the spark plasma channel. The spark itself is represented by computational particles for monitoring its motion and ignitability. Heat diffusion from the spark toward the surrounding mixture is calculated with a one-dimensional (1D) model, resulting in the temperature obtained at the surface of the spark channel. Based on the calculated temperature and interpolated pressure and local mixture composition, an instantaneous ignition delay time is read from tabulated values for every particle representing the spark channel. The final ignitability criterion is defined by a precursor calculated with a zero-dimensional (0D) model, which accounts for the history of changes in spark surface temperature and local mixture properties. As soon as the precursor reaches a threshold value for a given spark channel particle, a flame kernel is introduced at a position of the particle. Flame propagation is generally treated by the G-equation combustion model. Validation is performed by measurements of the spark discharge process in high-velocity flow field and single-cylinder AVL research engine. We demonstrate that the proposed model can correctly reproduce the electrical circuit, spark channel dynamics, and overall engine performance.
