喷油时刻对汽油/乙醇发动机性能的影响

Effect of Fuel Injection Time on Performance of a Gasoline/Ethanol Engine

通过一台Yamaha YBR250发动机原机,进行乙醇直喷(EDI)与汽油进气道喷射(GPI)的改装,研究了EDI喷油时刻对发动机缸内混合气形成、燃烧和排放的影响,同时建立了EDI结合GPI发动机的三维计算模型,对试验工况进行了数值模拟.分别对喷雾模型和燃烧模型进行了试验标定,结果表明:通过改变EDI喷油时刻,进气涡流与喷雾带动气流的运动共同作用于缸内燃料的蒸发雾化,可以在火花塞附近形成不同程度的燃料浓区;延迟EDI喷油时刻至100°CA BTDC,能够有效地协同壁面传热以及乙醇蒸发作用,降低点火时刻缸内温度,从而降低最大爆发压力和缸内燃烧温度;相对于早喷工况,EDI喷油时刻为100°CA BTDC的工况能够有效降低缸内HC及NO排放.

The effects of ethanol direct injection(EDI)injection time on the in-cylinder mixture formation,combustion and emissions were studied on a modified Yamaha YBR250 engine which equipped with a EDI plus gasoline intake port injection(GPI)system.A three-dimensional model of the EDI+GPI engine was established to comprehensively simulate the air intake process,injection process,fuel and gas mixing and combustion process for the experimental points.In the simulation,the spray model and combustion model were calibrated respectively.The experimental and simulation results show that,by changing the EDI injection time,the intake swirl and the spray driven air flow can act on the atomization and evaporation of the fuel in the cylinder,leading to a rich mixture distribution near the spark plug.Delaying the EDI injection time to 100°CA BTDC can effectively reduce the in-cylinder temperature on the time of spark discharge,thus reducing the maximum combustion pressure and temperature.Delaying the EDI injection time to 100°CA BTDC can also effectively reduce HC and NO emissions compared with the early EDI injection time.