Effects of different valve lift adjustment strategies on stoichiometric combustion and lean burn of engine fueled with methanol/gasoline blending

Abstract

In order to cope with the increasingly severe energy and environmental problems, the development of new technologies and alternative fuels have gradually become a hot spot. The effects of different valve lift adjustment strategies on engine performance under stoichiometric combustion and lean burn were studied when fueled with methanol/gasoline blending. The results showed that when fueled with M100, M50 and M0 under stoichiometric combustion, compared with the original throttle condition, reducing valve lift resulted in a longer combustion process. Economy performance and BSNOx, BSCO emissions all can be improved in varying degrees by adjusting intake or/and exhaust valve lifts, but BSHC emissions showed no obvious variations. The optimal valve strategy for economy performance was different for different fuel. Combined adjusting intake and exhaust valve lifts with fully opened throttle was suitable for M100, the strategy combined throttle with intake and exhaust valve lifts was optimal for M50 and M0. The ESFC was improved at most 5.6%, 4.7% and 6.8% when fueled with M100, M50 and M0 under the optimal strategy respectively. Regardless methanol additional rate, lean burn controlled by intake valve lift with fully opened throttle had more potential on improving engine economy performance. Blending methanol with gasoline could extend the lean burn limitation and further improve economy and emissions performance. The optimal ESFC improved by 1.7% and 2.4% more than that of original throttle engine when fueled with M0 and M100 respectively, and the lean burn limitation was expanded from 1.3 to at least 1.45.