A numerical investigation of injector hole configuration and injection parameters in a dimethyl ether fueled DICI engine

The lower calorific value of dimethyl ether (DME) is approximately 65% of that of diesel; therefore, a higher quantity of DME must be supplied per cycle to generate the same magnitude of power. A retrofitted DME-fueled engine generally uses a longer fuel injection duration to provide the excess fuel mass. The present work seeks to find the most appropriate way to increase the mass flow rate of a DME-fueled direct-injected compression ignition engine by varying the number of nozzle holes, nozzle hole diameter, and injection pressure. The results show that increasing mass flow rate increases peak combustion pressure and heat release rate but decreases combustion duration. Increasing the number of injector holes increases indicated specific fuel consumption (ISFC) and exhaust emissions (NOx, HC, and CO) due to mixing between unburned fuel spray and neighboring combustion products. Increasing the nozzle hole diameter or fuel injection pressure increases spray tip penetration and improves fuel-air mixing before combustion initiates. Increasing the nozzle hole diameter by merely 22 mu m than the baseline injector reduces ISFC and exhaust emissions at a slightly retarded start of injection (SOI). However, the lowest ISFC was found at the 30 MPa injection pressure at the most advanced SOI, at the expense of higher NOx.