Effects of pre-chamber jet ignition on knock and combustion characteristics in a spark ignition engine fueled with kerosene

Abstract

Pre-chamber jet ignition (PJI) is effective in accelerating combustion, expanding lean combustion limit and improving combustion stability on gas fuel and volatile liquid fuels. However, the effects of PJI on kerosene, which is less volatile and is more prone to knock than gasoline, are rarely discussed. In this work, PJI was applied to ignite kerosene in a direct injection dual spark plugs ignition (DSPI) engine and its effects on knock intensity, knock randomness, heat release rate, combustion phase and combustion stability were studied. Experiments were conducted with compression ratios (CR) of 6 and 7 respectively. Results show that PJI cannot improve the available CR of kerosene. At the early stage of PJI combustion process, a sudden increase and a fluctuation of heat release rate can be observed, which is coincident with the multi point ignition and highly turbulent flame caused by the rapid jet flow. PJI can improve the heat release rate, advance the combustion phase and improve the combustion stability of kerosene, but can also deteriorate the knock intensity without ignition timing adjustment. Due to the improved combustion stability, the randomness of knock is reduced. As a result, advanced combustion phase and reduced knock randomness lead to a better output and fuel consumption performance of PJI under critical knock condition than that of DSPI. The result shows that PJI.