Analysis on Combustion Process of Ethanol - Diesel Direct Injection Engine with Two-stage Ethanol Injection Ignited by Diesel

摘要

A set of GDI system was installed on a F188 single-cylinder, air-cooled and vertical direct injection diesel engine, which was used for ethanol injection, and the mechanical pump injection system of the original diesel engine was used for diesel injection. Ethanol and diesel account for half of the total size respectively, and the total heat energy of the fuel is equivalent to that of the original diesel engine under the same condition. A 3D combustion model is established for the ethanol - diesel direct injection engine. The ethanol injection is adopted with two-stage injection mode, with the first stage injection starting point at 240°CA and the second stage injection starting point the same as the diesel injection starting point, 344°CA. Four conditions featured by the same total two-stage ethanol injection and the first stage injection and second stage injection respectively accounting for 20% and 80% (B20L80), 40% and 60% (B40L60), 60% and 40% (B60L40) and 80% and 20% (B80L20) of the total injection are calculated and analyzed. After diesel burning, the mixed ethanol is ignited. The two-stage ethanol injection proportion is different, and ethanol premixing and diffusion combustion proportion in the cylinder is also different, thus affecting the combustion process. The result shows that, with regard to B60L40 and B40L60, cylinder combustion pressure and average temperature are higher, combustion speed is faster, combustion is more sufficient, and combustion process is better. B60L40 has the highest NO generation but the lowest soot generation, and B20L80 has the lowest NO generation but the highest soot generation.