Simulation Investigation of Working Process and Emissions on GDI Engine Fueled with Hydrous Ethanol Gasoline Blends 2019-01-0219
Internal Combustion Engine fueled with ethanol gasoline blends has advantages in performance of power, economy and emission, compared with ordinary gasoline. However, the fuel ethanol blended in ethanol gasoline blends currently is anhydrous ethanol, which is costly in dehydration process. Therefore, the production cost can be significant reduced by blending with hydrous ethanol instead of anhydrous ethanol while exerting the advantages of ethanol gasoline blends. In this study, computation fluid dynamics (CFD) software CONVERGE is employed to establish a simulation model of an actual gasoline direct injection (GDI) engine, to describe the effect of burning hydrous ethanol gasoline blends and changing injection strategy on combustion process and emission, and the validity of model was validated by experiments. The results show that, compared with gasoline, burning hydrous ethanol gasoline blends can accelerate combustion, expand the high temperature region during combustion, and reduce the formation of soot and CO, but an increasing formation of NOx. When changing the start of injection (SOI) timing, due to factors such as wall impingement, evaporation of fuel and in-cylinder flow, there is an optimal injection timing with the best uniformity of mixture gas, the highest heat release rate, the highest in-cylinder pressure peak and optimal time of pressure peak. Two stage injection can improve the fuel evaporation rate, optimize the distribution of the mixture gas, and reduce NOx emissions. The optimal secondary injection time is at -130 °CA, and the ratio is 25%. The stratified lean burn mode is also explored, and has the capability to reduce the combustion temperature and reduce NOx formation, but Soot, HC, and CO formation increases.
Yansu Liao, Xiuyong Shi, Jimin Ni, Yang Kang