Combustion of methanol in diesel engine using diethyl ether as ignition enhancer

Abstract

In this study, combustion of methanol in diesel engine is investigated using diethyl ether (DEE) as an ignition enhancer. Both experimental and numerical studies were performed and the results are compared with baseline diesel fuel. DEE has higher derived cetane number (DCN) of 139 when compared to methanol (DCN=8). Two blends DM75 (DEE 75% v/v + Methanol 25% v/v) and DM50 (DEE 50% v/v+ Methanol 50% v/v) were tested in diesel engine. For the same fuel injection timing of -20 CAD (aTDC), the intake air pressure is boosted to 1.75 bar to support auto ignition of DM mixtures. The peak cylinder pressures were comparable for diesel and DM75, while DM50 exhibited lower pressure with delayed start of combustion (SOC). Full cycle numerical simulations were performed using 3-D computational fluid dynamics (CFD) code (CONVERGE). DM75 and diesel showed similar flame liftoff and combustion phasing, and the numerical simulation results matched with the experimental results. Diesel ignited at a rich equivalence ratio range of 2-3, whereas DM75 and DM50 ignited at an equivalence ratio range of 1.0-1.5 and 0.3-0.6, respectively. The DM50 blend was found to exhibit stratified combustion with low in-cylinder and exhaust temperature when compared to DM75 and diesel.