Kyugo Hamai

Stabilized Combustion in a Spark Ignited Engine through a Long Spark Duration

An investigation has been done on the relationship between spark ignition characteristics and combustion stability in a gasoline engine. The spark discharge parameters examined are the spark current, energy, and duration. It is found that lengthening the spark discharge duration is particularly effective in achieving stabilized combustion. The analytical results of a constant volume combustion chamber test verify that a longer spark duration promotes flame initiation and makes reliable flame propagation possible. The length of the spark duration is regarded as the period from ignition to the onset of combustion pressure rise. The spark duration must be longer than the heat release delay. The reason is that a long-duration spark shortens the initial combustion period, thereby making it possible to reduce the fluctuations that occur during that period. This is particularly important because such fluctuations are known to be the main cause of the cycle-to-cycle fluctuations in engine combustion. The spark duration should be three to four times longer than the conventional spark discharge.