双层分流燃烧室结构对燃油扩散的影响

Effects of double-layer diverging combustion chamber structure on fuel spreading

为了研究不同燃油喷射条件下的双层分流燃烧室结构对燃油扩散和燃烧室内空间利用的影响,获得该燃烧室结构优化和油气室匹配的信息,本文利用可视化实验设备测试了2种结构差异明显的双层分流燃烧室内燃油喷雾扩散过程。研究结果显示:在一定范围内设置碰撞台均能实现燃油分层流动;容积较小的浅盆形上层燃烧空间可以保证顶隙空间获得良好的利用;容积较大的浅ω形上层燃烧空间有利于燃油快速扩散,但会导致局部富油分布;底部凸起较低且容积较大的下层燃烧空间有利于燃烧室中心区域的利用。研究结果表明:提高燃油喷射压力对不同双层分流燃烧室内燃油喷雾扩散的促进作用不同;碰撞台位置对燃油喷射正时有良好的适应性,但提前燃油喷射正时降低了上层燃烧空间对顶层区域利用的影响;减小油束夹角和喷孔孔径不利于燃油的快速扩散和油气的均匀混合。

The visualization measurement apparatuses were applied to test the fuel spray spreading processes in two double-layer diverging combustion(DLDC)chambers with different structural features to investigate the effects of DLDC chamber structure on the fuel spreading and in-cylinder utilization under different fuel injection conditions and obtain the structure optimization and the chamber-spray-charge motion matching information on this chamber.Investigation results showed that the impinging platform set in a certain region could realize double-layer spreading of the fuel.The smaller upper layer in a shallow dish type could ensure the top clearance utilized well;the larger layer in a shallowωtype was good for the fuel fast spreading,while it would lead to some rich fuel distribution region;the larger lower layer with a lower center pipe was good for the chamber center region utilization.The investigation results also indicated that:increasing the injection pressure showed different effects on promoting the fuel spray spreading in different DLDC chambers;the fuel impinging platform position showed a good adaptability for the injection timings,while advancing the injection timing decreased the influence of the upper layer on the top region utilization.Meanwhile,decreasing the cone angle and the nozzle hole diameter was not good for the fast fuel spreading and homogeneous fuel-air mixing.