A Simplified Circuit Model for the Emulation of Glow Phase during Spark Discharge

The ever-growing demand to meet the stringent exhaust emission regulations have driven the development of modern gasoline engines towards lean combustion strategies and downsizing to achieve the reduction of exhaust emission and fuel consumption. Currently, the inductive ignition system is still the dominant ignition system applied in Spark Ignited (SI) engines. It is popular due to its simple design, low cost and robust performance. The new development in spark ignition engines demands higher spark energy to be delivered by the inductive ignition system to overcome the unfavorable ignition conditions caused by the increased and diluted in-cylinder charge. To meet this challenge, better understanding of the inductive ignition system is required.

The development of a first principle model for simulation can help in understanding the working mechanism of the system in a better way. In this paper, an empirical model was proposed to emulate the relation between the equivalent ion channel resistance of the spark plug gap and the discharge current during the glow phase of a spark discharge. This empirical model was then embedded into a simplified physics based spark ignition circuit model which had been developed previously. Model validation was conducted against measurement results. Compared to the previous model, the proposed model can capture the electrical characteristics better during the glow phase of the spark discharge. Parametric analysis was presented using the model to study the effects caused by changing the ignition coil settings.