Numerical simulation of spray and mixture stratified combustion was performed in a gasoline direct injection (GDI) engine. A modified version of the KIVA-3V multi-dimensional CFD code including an improved fuel sheet atomization model, a spray breakup model, a droplet distribution model, an initial air tumbling model, a droplet evaporation model and a combustion model was used. Numerical studies of spray and mixture stratification are conducted for a GDI combustion chamber at a partial load operating condition.The effects of different injector orientations, reverse tumbling strength and injection timings on the mixture quality near the spark plug were analyzed and the results showed that these parameters would significantly influence the fuel stratification pattern, the ignition process and the combustion characteristics. Improper parameter settings would make the mixture too lean or too rich near the spark plug, resulting in a poor combustion. For a GDI engine, optimization in chamber configuration, tumbling flow and injection timing will play an important role in the success of stratified combustion under the partial load condition.%应用修正的多维流体力学计算程序KIVA-3V对缸内直喷(GDI)汽油机燃油喷雾和混合气分层燃烧过程进行了数值模拟.修正的子模型包括改进的燃油薄膜雾化模型、油滴破碎模型、油滴分布模型、初始缸内气体滚流模型、油滴蒸发模型以及燃烧模型.针对一种典型的三菱缸内直喷汽油机燃烧室结构在部分负荷工况下的燃油喷雾和分层燃烧进行了数值模拟.分析了不同的喷油器位置,缸内逆向滚流强度以及喷油时刻对火花塞附近混合气浓度的影响.计算结果表明,这些参数对燃油分层模式,点火过程以及燃烧特性都有显著影响,不适合的参数将导致火花塞间隙附近燃油空气混合气过稀或过浓从而使燃烧恶化.对缸内直喷汽油机部分负荷工况而言,燃烧室构形、缸内气体流动组织以及喷油时刻的优化设计对实现成功的分层燃烧起着重要作用.
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