A Preliminary Study of the Discharge Current and Spark Energy for the Multi-Coil Offset Strategy

To overcome the unfavorable operation conditions caused by lean/diluted charges in modern Spark Ignited (SI) engines, various advanced ignition systems have been proposed in the past. Among them, the dual-coil and multi-coil Transistor Coil Ignition (TCI) systems with offset discharge strategy caused significant attention in literature because they can generate a continuous spark with high spark energy being delivered into the cylinder. Comparing with the dual-coil system, a multi-coil system is capable to apply more flexible control strategies and generate a higher discharge current. However, the spark energy and transfer efficiency of the multi-coil system are still worthy to investigate as they are important performance indicators for a TCI system.

In this paper, the discharge characteristics of the dual-coil and triple-coil strategies under both quiescent and flow conditions were studied firstly by experimental methods. Based on the test results, a numerical model for the multi-coil system was developed. Simulations of gradually adding more coils up to ten to the multi-coil system were conducted. Spark energy and transfer efficiency for each simulation conditions were calculated and compared to investigate the influence of the coil number on the discharge current and spark energy of the multi-coil offset strategy.