Effects of ethanol, ethyl-tert-butyl ether and dimethyl-carbonate blends with gasoline on SI engine

Abstract

The oxygenates ethanol (EtOH), ethyl-tert-butyl ether (ETBE), and dimethyl carbonate (DMC) were blended in a gasoline blendstock at levels of 2.8wt% oxygen. Chemical and physical properties of the blends were compared to the requirements of ozone non-attainment areas in México, particularly the percent of oxygen and the octane number but with reduced Reid vapor pressure with respect to the commercial regular gasoline sold in the area. Ethanol seems to be the additive that provides the highest fuel sensitivity (RON-MON) followed by the DMC blend. The blends were tested on a single cylinder spark ignition engine. Experiments were conducted for equivalence air–fuel ratio, fuel consumption, volumetric efficiency, brake thermal efficiency, brake power, engine torque and brake specific fuel consumption, while exhaust emissions were analyzed for carbon monoxide (CO), carbon dioxide (CO2) and nitrogen oxides (NOx). For all studied engine operation conditions (stoichiometric, rich and lean), baseline fuel presents the maximum cyclic dispersion; therefore, adding oxygenates makes more homogeneous cycle-by-cycle operation. The presence of DMC compensates for the reductions in combustion speed as the air fuel ratio becomes lean. Ethanol has similar effect; however, ETBE does not present this behavior. Additionally, EtOH and DMC burned 5–10% faster than ETBE and baseline gasoline under lean conditions.