The effect of end-gas auto-ignition flame properties on the knocking intensity of a dual-fuel hydrogen engine

This study sought to elucidate the mechanism governing PRE-mixed mixture ignition in end-gas region (PREMIER) combustion in a dual-fuel hydrogen engine. Both knocking and PREMIER combustion are induced by end-gas auto-ignition, but differ in terms of the subsequent development of pressure waves. Knocking is accompanied by strong waves, whereas PREMIER combustion is characterized by the absence of, or very few, such waves. End-gas auto-ignition of hydrogen–air mixtures was visualized while in-cylinder pressure was measured using an optical compression and expansion machine. The visualization data indicate that KI increased as the spread velocity of the end-gas auto-ignition front rose. That velocity remained below 100 m/s during PREMIER combustion, but attained approximately 400 m/s in severe knocking cycles. The theory proposed by Bradley was used to evaluate the experimental results, and two dimensionless parameters, ξ and ε , were estimated. The ξ - ε diagram showed a distinct transition from PREMIER combustion to knocking. (150 words).