Effect of diesel/PODE/ethanol blends coupled pilot injection strategy on combustion and emissions of a heavy duty diesel engine

Abstract

Ethanol has limited solubility in diesel. Polyoxymethylene dimethyl ethers (PODE) can enhance the miscibility of ethanol/diesel blends. The application of pilot injection strategy can improve combustion noise and NOx emissions. Thus, the effects of different diesel/PODE/ethanol blends coupled various pilot injection strategies on the combustion, performance and emissions were conducted in a six-cylinder heavy duty diesel engine. As renewable alternative fuel, PODE has the characteristics of high cetane number, high oxygen content and no CC bond, while ethanol has the characteristics of high volatility and high oxygen content. The results show that the significant differences in heat release rate (HRR) and maximum pressure rise rate (MPRR) among DP20, DPE5, DPE10 and DPE15 can be reduced by using the pilot injection, in that the differences in HRR timing and peak value of HRR are weakened. Both the brake and indicated thermal efficiency of blends can be improved by appropriately optimizing the pilot strategy, when compared with the case of single injection. The thermal efficiency of blends is more sensitive to the pilot injection quantity, while the CO and HC emissions are more sensitive to the pilot-main interval. For single injection, blending ethanol into PODE/diesel blends causes adverse effects of increasing hazardous gas emissions, while optimizing pilot injection strategy can reduce the hazardous gas emissions of the blends to the best level of diesel and significantly reduce soot emissions when compared to diesel.