Abstract
Spark ignition engines have a fateful event that enhancing EGR rate makes cycle-by-cycle variations and then ends up its combustion limit. To unveil this event, spark discharge images were shot with a high-speed video camera, and spark discharge electric current and voltage, in-cylinder pressure were measured at the same time under high EGR rate combustion. The relations between spark discharge behaviors and combustion characteristics were investigated. It is discussed here how initial combustion speed variations, which caused by differences of spark discharge behavior among cycles, affects the combustion cycle-bycycle variations.
