Combustion Control by Pilot Fuel Injection for Utilizing Low Cetane Number Fuels in Diesel Engines

Abstract

This paper investigates a combution control technique for utilizing low cetane number fuels in diesel engines. Two types of light cyclic oil (LCO) with cetane index of 23 and 31 were tested. The influences of the pilot injection on the combustion, thermal efficiency, and exhaust emissions were examined in a single cylinder diesel engine equipped with a common-rail type fuel injection system.The results show that LCO with cetane index of 31 brings higher rate of pressure-rise, higher NO_x and lower smoke emissions compared to diesel fuel because of an enhanced premixing due to a longer ignition delay. However, the pilot injection enables the engine to operate on the LCO smoothly without causing the too high rate of pressure-rise. The pilot injection also enables the operation on the LCO with cetane index of 23 at selected load conditions.