There is a problem to decrease the ignition probability while lean combustion improves that the thermal efficiency of spark ignition engines. Therefore, some techniques that improve the ignition probability are necessary in lean combustion. In the present study, the ignition and combustion characteristics of the spark plug with dome-shaped flanges were examined by using swirling flow fields. The result shows that the dome flanged spark plugs were high ignition probability compared with conventional plug. It is considered the reason was the effect of the collection of the shock wave energy and the effect of suppressing the flow in vicinity of the spark gap. Especially, in lean condition, the ignition probability of the dome flanged spark plug with three holes and the hole was arranged in straight for the flow was the highest. In other side, the combustion characteristic of the dome flanged spark plug with three holes and the hole not to face the flow was better than conventional plug and other dome flanged spark plugs.
