Optimization of palm oil biodiesel blends and engine operating parameters to improve performance and PM morphology in a common rail direct injection diesel engine

In this paper, the characteristics of five palm oil biodiesel blends (B0, B10, B20, B30, and B100) have been tested in a common rail direct injection (CRDI) diesel engine with various EGR rates and pilot injection timings under 25% and 75% engine loads. The following were evaluated: combustion characteristics, including in-cylinder pressure, heat release rate (HRR), and mass fraction burned (MFB); engine performance parameters, including brake specific fuel consumption (BSFC) and coefficient of variation of the indicated mean effective pressure (COVimep); and emission characteristics, including CO, HC, NOx, PM and its morphology. By considering the combustion and emission characteristics, we found that the diesel engine fueled with B30 blend fuel with a 10% EGR rate, or with a pilot injection timing of 24 degrees CA BTDC, can effectively reduce PM emissions and simultaneously keep NOx emissions at a low level. In addition, we found that the variations of the engine load and EGR rate, as well as the biodiesel blend ratio, have direct impacts on the PM particle diameter, shape, and other morphology.