Combustion and Emission Characteristics of a Low Emission and Highly Efficient PCCI Diesel Engine

Abstract

The combustion and emission characteristics of a low emission and highly efficient premixed charge compression ignition diesel engine operated with moderate amount of exhaust gas recirculation was investigated in a single cylinder test engine. Tests were carried out under constant speed and fuel quantity with two injection pressures 80 and 140 MPa while the injection timing was varied. Exhaust emissions and in-cylinder pressure were measured for the all the experimental conditions considered. Analysis based on the engine performance and exhaust emissions were carried out. The introduction of exhaust gas recirculation (EGR) under higher injection pressure led to the simultaneous reduction of nitrogen oxides (NO_x) and soot emissions due to a lower combustion temperature compared to conventional diesel combustion. However, the emissions of hydrocarbon and carbon monoxide slightly increased due to insufficient oxygen to allow complete combustion. Higher boost pressure led to higher indicated thermal efficiency and indicated mean effective pressure (IMEP) with low emissions of NO_x and soot with relatively same CO but slightly higher HC emissions. High engine performance and lower emissions was achieved at the high injection pressure coupled with EGR rate and high boost pressure.