In this study, the effect of various pilot injection timings on combustion and emission characteristics were investigated in a common-rail direct injection (CRDI) diesle engine fueled with diesel-ethanol blends. The engine speed and engine load were controlled at constant 1500rpm and 70Nm, respectively. The tested fuels were DE0 (pure diesel fuel), DE5 (5 vol.% ethanol blended with 95 vol.% diesel oil), DE10 (10 vol.% ethanol blended with 90 vol.% diesel oil) and DE15 (15 vol.% ethanol blended with 85 vol.% diesel oil). The main injection timing was fixed at 0°CA TDC (top dead center), while various pilot injection timings including 25°CA BTDC (before top dead center), 20°CA BTDC and 10°CA BTDC were selected as the experimental variable. The experimental results showed that various pilot injection timings had little effect on the peak value of cylinder pressure, but had great influence on the start of combustion. The peak value of heat release rate (HHR) increased with the increase of ethanol content. However, the peak value of HRR reduced as the pilot injection is delayed. The diesel fuel containing 10% ethanol had a highest peak value of combustion pressure compared with the others, while the pilot injection timing occurred at 25°CA BTDC. On the other hand, the exhaust emissions of DE10 was also the lowest compared with the others. In addition, with the increase of ethanol content in diesel the PM and NOx emissions reduced.

Biodiesel fuel (BDF) can be effectively used as an alternative fuel in diesel engines. The BDF, however, may affect performance and exhaust emissions of the diesel engine because it's physical and chemical properties are different with from the diesel fuel such as viscosity, compressibility and so on. To investigate an effect of injection timing on characteristics of performance and exhaust emissions with the BDF in an IDI diesel engine, this research applied the BDF derived from soybean oil in this study. The engine was operated with six different injection timings from TDC to BTDC 12 ˚CA and six different loads at the engine speed of 1500 and 2000 rpm. In less then the BDF 20, it showed the similar trend compare to the diesel fuel. But, the best injection timing was 2˚CA retarded compare to the diesel fuel with BDF 50.

본 연구에서는 건조 후 20여년 운항한 군산대학교 실습선 해림호의 발전기를 대상으로 직접 선박현장에서 실험하여 최적 연료분사시기를 규명해서 선박의 경제적이고 친환경적인 운항에 도움을 주고자 연구하였다. 실험은 기관회전속도 1,200 rpm으로 일정히 유지하고, 기관부하를 0 kW에서 90 kW까지 30 kW간격으로 변화시켰으며, 연료분사시기는 BTDC 19o에서 23o까지 2o 간격으로 변화시키면서 실험하였다. 실험결과 연료분사시기를 BTDC 21°에서 BTDC 23°로 앞당길 경우, 연료소비율은 1.37 % 감소하였고, 질소산화물은 11.59 % 증가하였으며, 매연은 23.5 % 감소하였고, 아황산가스는 2.8 % 감소하였다. 따라서 노후 발전기 엔진에 있어서 연료분사시기가 연소특성 및 배기배출물특성에 미치는 영향을 종합적으로 분석․고찰한 결과, 최적 연료분사시기는 원래의 분사시기보다 2° 앞당겨진 BTDC 23°로 확인되었다.