Experimental Investigation of PCCI-DI Combustion on Emissions in a Light-Duty Diesel Engine

The combination of premixed charge compression ignition (PCCI) and conventional DI diesel combustion was studied on a light-duty diesel engine equipped with EGR and a common rail fuel injection system. This combustion mode is referred to as PCCI-DI combustion. The main objectives of the study were to examine the emissions, performance and combustion characteristics of the engine operating under various levels of PCCI-DI combustion to determine if this mode of combustion was a viable in-cylinder NO_X emissions reduction strategy. The premixed charge was obtained with early pilot injections (up to three) using a custom engine controller. The engine test conditions were limited to light and medium loads and moderate engine speeds. Engine tests consisted of sweeps of pilot injection timing and quantity, and number of pilot injections. The results of this study suggest the greatest potential for reducing NO_X emissions with PCCI-DI combustion exists at light loads (below 30%) and medium to low speeds. At 1500 rpm and 17% load, moderate NO_X reductions of up to 15% were achieved, while a 9% NO_X reduction was achieved at 2600 rpm and 54% load.