Effects of blending MTBE, methanol, or ethanol with gasoline on performance and exhaust emissions of SI engines

The current experimental study aims to examine the effects of using oxygenates as a replacement of lead additives in gasoline on performance and exhaust emissions of a typical SI engine. The tested oxygenates are MTBE, methanol, and ethanol. These oxygenates were blended with a base unleaded fuel in three ratios (10, 15, and 20 vol.%). The engine maximum output, thermal efficiency, CO emissions, HC emissions, and NOx emissions were all evaluated at a variety of engine operating conditions using an engine dynamometer set-up. The results of the oxygenated blends were compared to those of the base fuel and of a leaded fuel prepared by adding TEL to the base.;The methanol blends performed better than the other oxygenated blends in terms of engine output and thermal efficiency. The MTBE blends were the best performers among the oxygenated blends in terms of HC emissions while the ethanol blends were the best performers in terms of CO and NOx emissions.;When compared to the base and leaded fuels, the oxygenated blends improved the engine brake thermal efficiency. The leaded fuel performed better than the oxygenated blends in terms of the maximum output of the engine except in the case of 20 vol.% methanol and 15 vol.% ethanol blends. With respect to the base fuel, the addition of oxygenates decreased the CO emissions, decreased the HC emissions at most operating conditions, but generally increased the NOx emissions except for 10 vol.% ethanol blend. The emissions results for the leaded fuel were comparable to those of the base.