예혼합 압축착화 디젤 엔진에서 압축비, 운전속도 및 분사시기에 따른 혼합기 및 연소 특성

Abstract

The application of early diesel injection for near-homogeneously premixed charge has been tested in the single-cylinder engine. HCCI engine combustion has been investigated with the variety of engine operating parameters e.g. compression ratio, engine speed and, injection timing. Low compression ratio (14.8) with the advanced injection timing earlier than 50°CA BTDC was applied for achieving well-mixed charge and appropriate combustion phasing. The variation of injection timings were tested for two different engine speed (800 and 1200 rpm) and the results showed that 6.2 ms of ignition delay was required to reduce engine-out NOx emissions to negligible level regardless of engine speed. A sudden increase of power-output was captured at around injection timing=70°CA BTDC. A visualization of the spray explained that the power-output was high due to the increased air utilization by the spray directing the bowl-lip area resulting in improved mixture preparation and combustion efficiency.