Conventional Navy jet fuel ‘5’ (JP-5) was operated in a Waukesha single cylinder diesel Cooperative Fuels Research (CFR) engine with intake port jet fuel injection under a range of compression ratios (CR). At the lowest CR of 12, a small range of engine loads in the lower torque or gross indicated mean effective pressure (gIMEP) range could be attained. As the engine CR was increased only a very limited range of loads were attained since heavy engine ‘knocking’ occurred. Navy jet fuel is a reactive fuel (cetane number 46), and thus could not tolerate higher CRs without premature combustion. Intake port water injection was then applied in order to cool the intake air charge and delay the jet fuel HCCI start of combustion. As a result, a range of HCCI operation (gIMEP from 1 to 5 bar) could be attained across a range of CRs. In general, with this approach, combustion phasing with port fuel and water injection advanced with increasing CR resulting in lower efficiencies at the higher CRs. Exhaust carbon monoxide (CO) was minimum in mid-HCCI operating range suggesting a trade-off of poor light load lean combustion, and the steadily diluted higher load operation with increasing water content. Companion analysis suggests that the thermal energy for water evaporation was principally provided by the engine walls. Further, the dilution effect of the water resulted in lower overall charge temperatures which further lowered the overall reactivity of jet fuel in the engine allowing reasonable HCCI operation.

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