Influence of intermediate temperature heat release on autoignition reactivity of single-stage ignition fuels with varying octane sensitivity

This study investigates the effects of intermediate temperature heat release (ITHR) on autoignition reactivity full boiling range gasolines with different octane sensitivity through intake and simulated exhaust gas recirculation (EGR) sweeps in a homogenous charge compression ignition (HCCI) engine. To isolate ITHR effects, low was suppressed use high oxygen mole fraction. For quantification ITHR, new method applied to engine data by examining maximum value second derivative rate. Combustion phasing comparisons fuels showed that fuel less became more reactive as EGR ratio decreased, while higher had reverse trend. all were tested, amount increased fraction increased. These trends, depending sensitivity, almost identical trends combustion phasing, showing significantly affects determines sensitivity.