Effect of isopropanol and n-pentanol addition in diesel on the combustion and emission of a common rail diesel engine under pilot plus main injection strategy

Abstract

In this study, isopropanol and n-pentanol are blended in diesel with 20% ratio by volume, named D80IP20 and D80NP20. Their combustion and emission performances were compared with diesel on a four cylinder common rail diesel engine under pilot plus main injection strategy. The pilot injection duration decreases and the main injection duration increases with engine loads. For test fuels, the starts of pilot and main injection and the durations of pilot injection are remained unchanged in each engine operation. D80IP20 has the longest ignition delay due to the lowest cetane number and the shortest combustion duration due to the highest fuel oxygen. However, the peak combustion temperature of D80IP20 is lower than that of D80NP20 under double injection strategy. Compared to diesel, both D80IP20 and D80NP20 obviously reduce the particle number concentrations (PNCs) and the particle volume concentrations (PVCs), while increase the NOx emissions. D80IP20 has the lowest PNCs and PVCs and its number geometric mean diameter (NGMD) and volume geometric mean diameter (VGMD) are the lowest among the three fuels. D80IP20 has higher NOx emission than diesel, but lower than D80NP20 due to lower PCT. Further, D80IP20 with 10% EGR can achieve the simultaneous reduction for NOx emission and PNCs at low and high loads compared to diesel without EGR. Results indicate that blending isopropanol in diesel has better effects in combustion improvement and emission control and is more suitable than n-pentanol under pilot plus main injection strategy.