Effect of split injection strategies on diverse characteristics of a common rail direct injection diesel engine operating with diesel-palm oil-ethanol micro-emulsions

Abstract

This study investigated the effect of pilot injection timing (PIT) and pilot injection quantity (PIQ) on the performance of a common rail direct injection (CRDI) diesel engine with two-stage injection system operating with diesel-palm oil-ethanol micro-emulsions. The results indicated that, at low engine load, the maximum in-cylinder pressure (P_max) and peak of heat release rate (HRR) of D35P35E30 were highest, and those of D100 were lowest. At high engine load, the P_max of D100 was highest, that of D60P30E10 was lowest, and the peaks of HRR were almost identical for all test fuels. The P_max and peak of HRR were slightly increased with the advance of PIT. Increasing PIQ increased the first peak of HRR and reduced the second one. At low engine load, the coefficient of variation (COV) of P_max and the indicated mean effective pressure (IMEP) presented a slight decrease for the micro-emulsions, but did for D100 at high engine loads. The brake specific fuel consumption (BSFC) of the micro-emulsions was higher, and the brake thermal efficiency (BTE) was also slightly higher when compared with diesel (D100). With the advance of PIT and the increase of PIQ, BSFC was increased, BTE was decreased, and hydrocarbon (HC) emissions were reduced. The variation of PIT and PIQ had little effect on the particle number concentration (PNC), but had evident effect on nitrogen oxides (NOx) emissions. It was concluded that the micro-emulsions can be used to reduce NOx and particulate matter (PM) simultaneously combined with injection strategy in a diesel engine.