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Spark ignition experiments were conducted to investigate effects of multi discharges on ignition of a lean-turbulence mixture. Initial flame kernel developments were observed by Schlieren photography, and discharge characteristics were analyzed by high-speed photography and spectroscopic measurements. Results indicated that the MIE (Minimum Ignition Energy) of the single discharge was lower than that of the multiple one at 100 kPa, and higher at 500 kPa. Each discharge was generated independently when discharge interval was set to 1 ms at 500 kPa, while discharge was occurred continuously at 100 kPa. This discharge characteristics might be related to the ignition performance.

In order to improve the ignition stability and reduce the cycle-to-cycle variation, it is necessary to understand the mechanism of the flame kernel development and the local quenching effect during the spark ignition process. In this study, experiments for the spark ignition process in a high-speed lean gasoline-air mixture turbulent flow field were conducted. OH* chemiluminescence measurement and focusing Schlieren photography was applied to observe the development of flame kernel and discharge channel behaviors simultaneously. Results indicated that flame kernel fragments, generated by the restrike and short- circuit of discharge channels, quenched due to the local turbulence, which led to slow flame propagation or misfire. In that cases, the initial flame kernels showed stretched behaviors, along with high curvatures.