Browse Publications Technical Papers 2019-01-0725
2019-04-02

A Preliminary Study of the Discharge Current and Spark Energy for the Multi-coil Offset Strategy 2019-01-0725

Future clean Spark Ignited (SI) engines are on the trend of lean/diluted combustion strategies and engine downsizing to achieve the reduction of exhaust emission and fuel consumption. However, the new development in SI engines demands higher spark energy in terms of higher discharge current level and longer discharge duration to overcome the unfavorable ignition conditions caused by the diluted in-cylinder charge and the increased back pressure. The spark energy delivered from the single-coil single discharge of the conventional Transistor Coil Ignition (TCI) system is limited because of its energy storage capability. In order to realize robust ignition control, advanced discharge strategies based on the TCI system, including dual-coil or multiple coil discharge, were proposed over the past. With the use of additional coils, these ignition systems are capable to deliver more energy to the spark gap and generate controllable discharge current profiles. In this work, a three-coil ignition system with a compact package size was developed. Based on this system, the spark discharge characteristic of dual-coil and three-coil discharge strategies were studied and compared with the conventional single-coil single discharge through experimental results. Comparing to the dual-coil discharge strategy with a 50% duty cycle, the duty cycle of the three-coil discharge is only 30% when delivering the same amount of energy to the spark gap. The energy transfer efficiency of the three-coil discharge therefore is higher than that of dual-coil discharge. Simulations were conducted to investigate the effects of coil inductance, charging duration and charging frequency on the discharge profile and the delivered spark energy of the three-coil ignition system.

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