커먼레일 시스템을 장착한 단기통 예혼합압축착화엔진의 Two-stage디젤연료 분사법에 따른 연소 및 배기가스 특성

Abstract

A small size in-cylinder direct injection diesel engine is modified to operate in HCCI mode. the recent problem to realize a stable HCCI combustion in the need of high inlet air temperature to vaporize a diesel and to achieve a well premixed charge. this high inlet temperature makes lower thermal efficiency. this is the main reason why the two-stage injection strategy is applied to control combustion process without intake air heating. the first stage of injection is used as a main fuel injection while the injection timing is varied from BTDC 100。to BTDC 300。and the small quantity of a diesel fuel is used for the second stage of injection as a pilot fuel while the injection timing is varied from BTDC 10。to TDC. also the effect of air-fuel(A/F) ratio is studied to promote the auto ignition. the wxperimental result shows the two-stage injection could be used as a diesel-fueled HCCI injection strategy when the first main injection timing is near the end of the intake stroke to achieve the highest IMEP and the second pilot injection timing is near TDC to achieve a premixed combustion only. if the second injection timing is advanced. heat release rate indicated the diffusion flame like DI-Diesel engine. compared to DI-diesel engine in the same IMEP value, HCCI engine result shows more than 80% NOx reduction but higher fuel consumption and more THC value