분사기 형상이 예혼합 압축착화 엔진 연소에 미치는 영향

Abstract

The effect of injector geometries including the injection angle and number of nozzle holes has been investigated in a diesel-fueled homogeneous charge compression ignition (HCCI) engine. The HCCI engine has advantages of simultaneous reduction of PM and NOx emissions by achieving the spatially homogenous distribution of diesel and air mixture, which results in no fuel-rich zones and low combustion temperature. The wall- impingement of the diesel spray to the cylinder liner is a serious problem to achieve the homogeneous charge. It is because the injection timing should be extremely earlier than the conventional direct-injection (DI) diesel engine to achieve the homogeneous charge, so that the in-cylinder pressure and temperature is very low that results in longer spray penetration. A hole-type injector (5 holes) with small injection angle (100°) instead of conventional angle (150°) was applied to resolve this problem. The multi-hole injector (14 holes) was also tested to maximize the atomization of diesel. The macroscopic spray structure was visualized in a spray chamber, and the spray penetration was analyzed. Moreover, effect of injector geometries on the power output and exhaust gases was tested in a single-cylinder diesel engine. Results showed that the small injection angle minimizes the wall-impingement of diesel fuel that results in high power output and low PM emission. The multi-hole injector could not decrease the spray penetration at low in-cylinder pressure and temperature, but still showed the advantages in atomization and premixing.