The Influence of Spark Ignition Characteristics on Stable Combustion in a Spark Ignited Engine : 4th Report, A Study on Cycle-to-Cycle Combustion Fluctuation

Abstract

As an initial combustion period involving the growing process of a initial flame kernel, is easily affected by the cycle-to-cycle air-fuel ratio and gas motion, combustion always fluctuates unstably in a spark ignited engine. In this study, by measuring the phenomena of spark ignition and engine combustion simultaneously, it is clarified that a decrease in cycle-to-cycle spark ignition fluctuation is achieved by increasing spark current. The spark ignition, however, is mainly fluctuated by cycle-to cycle gas motion in-cylinder during ignition timing. When a long durational spark which has a high spark current is given to stabilize the engine combustion, a new aspect has been obtained showing that the initial combustion period can be made to shorten and reduce its fluctuation. Especially, this characteristic of spark ignition is effective for a lean burn, which is fundamentally unstable combustion.