Effects of diesel-ethanol-THF blend fuel on the performance and exhaust emissions on a heavy-duty diesel engine

The application of ethanol in diesel engines is limited for the poor solubility. Tetrahydrofuran (THF) as a promising biofuel can improve the solubility. In this study, the effects of THF and ethanol on combustion and emissions were investigated on a six-cylinder heavy-duty diesel engine. In terms of test fuels, the volume ratio of THF was 5%, and ethanol ratio was 0%, 10%, and 30%, respectively. Results show that the combustion characteristics are nearly the same in both fuels with and without THF addition in diesel. With the increase of ethanol, the ignition delay prolongs, the peak heat release rate raises and brake thermal efficiency increases. The delay of the combustion phase at a low load is more obvious than a high load. The addition of THF or 30% ethanol increases NOx emissions, while the addition of 10% ethanol reduces NOx emissions at low load. Also, the addition of THF or ethanol decreases soot emissions significantly, but HC and CO emissions increase significantly at low loads. In the World Harmonized Stationary Cycle test cycle of Euro VI regulation (the speeds contain 998, 1137, 1276, 1415, and 1694 rpm and the loads cover the idle to full load), compared with diesel fuel, the addition of 10% and 30% ethanol makes BTE decrease by 1.7% and 0.8%, NOx emissions increase by 16.2% and 22.6%, soot emissions decrease by 39.2% and 77.3%, HC emissions increase by 6.9% and 39.3%, and CO emissions decrease by 13% and increase by 43.5%, respectively.