Experimental analysis of chaotic property of in-cylinder combustion of SI engine

In spark-ignition (SI) internal combustion engines, fluctuations of the in-cylinder pressure trace and the combustion phase are usually different from one cycle to another. Distinguishing the randomness and the chaos, both of which cause the cycle-to-cycle variation (CCV), is beneficial to the optimization of engine control strategies. In this paper, the cycle-to-cycle varied CA50 series are analyzed based on the chaos theory, and the Lyapunov exponents of CA50 series are calculated. In contrast, an independent repeated random number series is analyzed by the same method. Comparing the Lyapunove exponents of measured CA50 series, some classic chaos systems, and the independent random number series, it can be found that the evolution of CA50 is affected more by randomness than by chaos.