Improvement of emission characteristics and maximum pressure rise rate of diesel engines fueled with n-butanol/PODE3-4/diesel blends at high injection pressure

Polyoxymethylene dimethyl ethers (PODEn) are promising alternative biofuels with high cetane number and oxygen content. In this study, effects of PODE3-4 addition to diesel on the macroscopic spray characteristics were studied in a constant volume spray chamber under different injection pressures. The engine performance and emission characteristics of n-butanol/PODE3-4/diesel blends were investigated in a diesel engine under high injection pressures. The results indicate that the spray penetration of BD20 or PD20 was greater than that of D100; the addition of PODE3-4 to BD20 led to a further increase of the spray penetration without significant effects on the spray cone angle. Under an equal fuel injection pressure, the combustion of BD20 showed the greatest Maximum Pressure Rise rate (MPRR), which decreased after the addition of PODE3-4 to the blend. The soot and NOx emissions of BD20 were lower than that of pure diesel. Compared with BD20, the reduction of CO and HC emissions from the combustion of BDP20 were as high as 45.65% and 28.24%, respectively. The soot, NOx, CO and HC emissions of BDP20 were all lower than that of PD20. As the fuel injection pressure increased, a decreasing trend was observed in the number concentration as well as in the mass concentration of total particles. The lowest particle emissions in terms of total particle mass concentration were found for BDP20, followed by PD20, BD20 and D100. The ratio of sub-50 nm particles to total particles was highest for BD20 regardless of the injection pressure, and its value decreased upon adding PODE3-4 to BD20.