Investigation on pilot injection with various Start of Injection two and fuel injection pressure in common rail direct injection diesel engine

This experimental study was carried out using a single-cylinder CI engine under the pilot injection strategy to investigate the effect of fuel injection pressure and the position of the start of combustion 2 (SOI2) on combustion characteristics and emission. The fuel mixtures used in this experiment were gasoline 80% mixed with Biodiesel 20% distinguished by volume. The double pilot injection was applied with varying the SOI2. Meanwhile, SOI1 was fixed at -350° BTDC with 900 bar fuel injection pressure. At SOI2 fuel injection pressure was varied between 400-900bar. The results show that increasing fuel injection pressure will most effect on ignition delay and the start of combustion (SOC). Higher fuel injection pressure will decrease the ignition delay due to smaller fuel stratification. Meanwhile, retarding SOI2 will affect SOC to occurs faster due to closer injection timing to TDC which lower the possibility of Low Thermal Combustion (LTC). NOx emissions will be shown increases as a sign of proper mixing fuel with oxygen which contrary to CO emission. Higher fuel injection pressure will produce a smaller fuel spray that enhances the mixing of fuel and air which decrease NOx while increasing CO emission. As the LTC strategy can produce low emission of NOx, injection fuel closer to TDC will improve NOx while decreasing CO emissions.