Effects of Ethanol in Ester-Ethanol-Diesel Blended Fuels on Spray Behavior and PM Emission

摘要

The ethanol has potential to be a renewable alternative fuel for internal combustion engines and contributes to lower global CO{sub}2 emission. In this study, vegetable methyl ester is added in the ethanol-diesel fuel to prevent separation of the ethanol from diesel, thus the ethanol blend ratio can be set up to 30% in volume. This work pays more attention on its spray, effects of the ethanol percentage on the detailed PM components. To investigate the spray behavior of ethanol, diesel and their blends, experiments in a constant volume chamber were carried out combining numerical simulation. Properties of the ethanol-diesel blended fuels were obtained through some measurements and empirical calculations. The breakup sub-model, Wave-KH model considering the blend fuel properties were adopted in an engine simulation code KIVA-3V. The simulation had a good agreement with experiments. This research work shows that ethanol has slight effect on penetration lengths and spray cone of the fuel, the greatest effect is on that the spray space of ethanol is larger and mixes with air better than the diesel. The PM emission and size distribution were also studied on a diesel engine with different fuels. The three individual components, namely SOF, DS and sulfate mass, were tested and analyzed in detail. The results show that with increasing ethanol in blend fuels, the smoke is decreased significantly; the PM emission is also reduced until the ethanol percentage is more than 20%. The smoke and PM have different behaviors even using the same kind of fuel. In addition, under the same condition, increasing ethanol in blend fuels, the DS emission in PM reduces the smoke, but the SOF emission is not reduced as expected. The ethanol in blended fuels affects PM size distribution and leads the PM diameter to become smaller.