Analysis on the Combustion Process of the Ethanol - Diesel Direct Injection Engine with Simultaneous Diesel and Ethanol Injection (with Ethanol Injection Starting Point Earlier than the Diesel Injection Starting Point)

A set of GDI system for ethanol injection is installed on a F188 diesel engine, and the diesel supply system of the original diesel engine is used for diesel injection. The computational fluid dynamics software FIRE is adopted to establish a 3D combustion model of the ethanol-diesel direct injection engine. The total heat energy of the fuel is equivalent to that of the original diesel engine under the same condition. As the diesel injection starting point is 344 degrees CA and there is simultaneous diesel and ethanol injection, the ethanol injection starting points at 344 degrees CA, 338 degrees CA, 332 degrees CA, 326 degrees CA and 320 degrees CA are subject to 3D simulation for fuel injection, mixed gas formation and combustion and pollutant formation process. The results show that, the earlier the ethanol injection is, the steeper the heat release rate curve during the initial combustion period, the higher the peak value, and the shorter the heat release duration are, and the higher the maximum combustion pressure, the headmost phase of the maximum combustion pressure and the more obvious the premixed combustion are. Earlier ethanol injection starting point and quicker rise of the temperature curve of the cylinder bring the headmost phase of the highest average temperature in the cylinder, and higher average temperature in the cylinder brings higher NO concentration. The ethanol injection starting point shall be earlier than the diesel injection starting point injection, for it is the most favorable for reducing soot generation.