On pre-ignition heat release of fuels with various octane sensitivities under compression ignition conditions

Abstract

Fuel and engine interactions are the essential issues for advanced compression ignition engines, and low-octane gasoline is considered as prospective fuel under compression ignition conditions. However, with enhanced low-temperature chemistry, low-octane gasoline may exhibit distinctive characteristics affecting ignition phenomena. In this study, the ignition phenomena of low-octane gasoline was investigated under gasoline compression ignition conditions using validated chemical kinetic mechanism. The toluene primary reference fuel blends were employed to obtain the same RON = 75 with various octane sensitivity. With addressing ignition characteristics and pre-ignition heat release, the role of fuel sensitivity, inlet conditions, and exhaust gas recirculation on fuel reactivity was clearly demonstrated. The results show that the fuel sensitivity is positively correlated with fuel reactivity in high-temperature low-pressure regime, whereas there is a negative correlation in low-temperature high-pressure regime. The opposite correlation between fuel sensitivity and fuel reactivity is closely related to the pre-ignition heat release, with decreasing low-temperature heat release at high fuel sensitivity. Finally, the effects of exhaust gas recirculation on low-temperature heat release were investigated. It shows that affected by low-temperature heat release, distinct characteristics in combustion phasing are observed with the addition of the exhaust gas recirculation.