Effect of Blending Dimethyl Carbonate and Ethanol with Gasoline on Combustion Characteristics

We investigated the effects of blending dimethyl carbonate (DMC) and ethanol with commercial gasoline on combustion characteristics. Our experimental approach involved using a rapid compression and expansion machine (RCEM) to achieve elevated temperatures and pressures. The fuels containing different volumes of oxygenated hydrocarbons were burned at equivalence ratios of 1.0 or 0.7, an initial temperature of 340 K, and initial pressures of 0.10 or 0.05 MPa. To simulate knocking phenomena, we installed a rectangular channel in the combustion chamber of the RCEM and measured the pressure history inside the chamber. By analyzing the pressure history resulting from the end-gas autoignition, we evaluated the combustion duration and maximum pressure amplitude. Blending both oxygenated fuels with gasoline effectively reduced the maximum-pressure amplitude in the end-gas autoignition, with ethanol exhibiting a more pronounced suppression effect compared to DMC in the same volumetric mixing ratio. At an initial pressure of 0.10 MPa, the combustion durations of DMC/gasoline blends showed non-linear behavior, being shorter than those of pure gasoline and DMC and comparable to those of the ethanol/gasoline blends. However, the blending effect of DMC on combustion durations was greatly mitigated when the initial pressure was reduced to 0.05 MPa. Conversely, the combustion durations for ethanol/gasoline blends showed a nearly monotonic reduction with an increase in the ethanol blending ratio at both initial pressures of 0.10 and 0.05 MPa. Finally, we discussed the differential impact of the blending effect of oxygenated hydrocarbons on combustion characteristics.