Combustion and emission characteristics of dimethyl ether/gasoline DFSI engine under different excess air coefficients

Dimethyl ether (DME) was a carbon neutral alternative fuel for engines.The combustion and emission characteristics of a DME/gasoline Dual Fuel Spark Ignition (DFSI) engine with various excess air coefficients (& lambda;s) at different DME ratios (& phi;DME) were investigated experimentally in this study.The in-cylinder pressures along with their relevant crank angle were used for the com-bustion characteristics calculation. The light five component exhaust gas analyzer and particle analyzer were employed for the gaseous and particulate matter emission measurement, respec-tively. Results showed that the DME/gasoline dual fuel combustion strategy can enhance the Brake Mean Effective Pressure (BMEP) by up to 12.6% because the high diffusivity, superior LTR and fast LFS of DME. Although adding DME was beneficial for the reduction of gaseous emissions (HC, CO and NOx) from DME/gasoline DFSI engines, the gaseous emissions were mainly deter-mined by the variation of & lambda; s. Particularly, up to 93.4% of the CO emissions at stoichiometric condition can be reduced after increasing & lambda; to 1.3. The fast evaporation rate and superior LTR of DME helped to suppress PN emissions, but larger DME ratio (& phi;DME > 5%) was needed for & lambda; >1.2.