Study On Cycle-to-Cycle Variaton Of In-Cylinder Peak Pressure In Gasoline Engines

As a significant character of the combustion process, the presence of cycle-to-cycle variation in gasoline engines limit the gasoline engines'operation areas and reduce its economy, power and emission control level. To minimize the cycle-to-cycle variation by deep understanding its principle is a major work of internal combustion engine researchers.This paper studied the cycle-to-cycle variation of in-cylinder peak pressure in gasoline engines. Based on experiment data, the influence of sampling numbers on the estimation precision of the in-cylinder peak pressure's cycle-to-cycle variation level has been studied, and the rational sampling numbers should be 2000 cycles according to a newly defined standard.Run the test under the condition of rational sampling number, found that in low load and lean mixture operation condition, by the increase of spark advance, the mean value of in-cylinder pressure increases, the standard variation of in-cylinder pressure increases, and the coefficient of variance of in-cylinder pressure increases in advance and decreases then. The spark advance should be set to avoid the point at which maxim COV pz happened when engine rworking in low load and lean mixture area.The distribution rule of in-cylinder peak pressure has been studied for the first time. Based on large test data and hypothesis testing method, the distribution of in-cylinder peak pressure has been proved to follow the Weibull distribution. The parameters of the density function areinfluenced by the engine speed, load, and air fuel ratio and spark advance.Finally, a regression distribution model of cycle-tocycle variation of in-cylinder peak pressure was established.