Effects of Multiple Parameters on Cyclic Variation of a SI Engine Fueled with 2-Methylfuran Gasoline Blends

Combustion characteristics of neat 2-methylfuran (MF), 10% and 20% volumetric fraction 2-methylfuran gasoline blends were experimentally investigated in a single cylinder spark ignition engine, and the results were benchmarked against that of the research on octane number 97 neat gasoline. The investigation focused on the performance of cyclic variation of MF and its blends, and the effects of spark ignition timing, compression ratio, and exhaust gas recirculation (EGR) were studied. Experiments were conducted at the engine speed of 1500 rpm, and loads between 7 and 11 bar indicated mean effective pressure (IMEP) with using stoichiometric air-fuel ratio mixture. Index of the coefficient of variation of IMEP (COV_IMEP) was used to evaluate the combustion stability of the tested fuels. The results show that neat MF and MF gasoline blended fuels have superior combustion stability compared with gasoline. With the increase of MF volumetric fraction, the COV_IMEP consistently decreased under different engine operation conditions. Through combustion analysis, MF shows shorter combustion duration than gasoline, which can largely explain the lower cyclic variation of MF and its blended fuels. With sweeping spark ignition timings, COV_IMEP of gasoline shows greater sensitivity than neat MF and two blended fuels, which indicates neat MF and the blended fuels can obtain more stable combustion when spark timing has to be deviated from maximum brake torque (MBT) spark timings. Increasing engine loads and compression ratios, more decline of COV_IMEP for gasoline can be found than that of MF and MF gasoline blended fuel. The COV_IMEP of gasoline goes up remarkably with the increase of EGR rates, while MF and MF gasoline blended fuel increases less in COV_IMEP. The overall results demonstrate that fueling neat MF or blending small amounts of MF has potentially favorable characteristics in decreasing cyclic variation, especially when retarded spark timing and high EGR rates have to be used.