直喷汽油机压电晶体控制外开轴针式喷油器喷雾场速度特性

Spray Velocity Characteristics of an Outward-Opening Pintle-Type Injector Actuated by Piezo for DI Gasoline Engines

应用粒子图像测速技术(PIV)对定容弹内多种试验条件下压电晶体控制的外开轴针式喷油器的喷雾场速度特性进行测量与分析.试验结果表明,油嘴附近的大尺度气体涡流A和涡流B不仅对油气掺混和喷雾雾化起到关键作用,对于点火时刻火花塞附近的混合气特性也具有重要影响.将喷射压力、环境压力、轴针升程及轴针座锥角对喷雾场内涡流运动的影响作为重点进行分析.结果表明,环境压力增加促进了涡流A和涡流B的增长,同时使涡流的位置更加靠近喷油器.轴针座锥角的变化显著改变了喷雾场内的气流运动特征,94°轴针座锥角的喷雾出现了明显的冲向油嘴的气体回流.通过对喷雾场各节点的速度结果进行标准差计算,得到了喷雾场的速度标准偏差.以此为基础,对喷雾场内涡流的运动特性及其对混合气分布的影响做了进一步的分析.

Velocity field characteristics on axial cross-sections of conical sprays from the piezo outwards- opening pintle-type injectors under different chamber conditions are measured and analyzed by means of particle image velocimetry （PIV）. Experimental results reveal that large-scale vortices not only promote air entrainment and atomization, but also play an important role on mixture distribution after injection. The effects of injection pressure, ambient pressure, needle lift and designed spray angle on the large-scale air vortex A and B are in- vestigated. The rise of ambient pressure improves the development of these two vertices and makes them ap- proach to nozzle. Variation of designed spray angle affects the velocity characteristics of spray field significantly. The obvious air backflow in the vicinity of nozzle with 94 deg. designed spray angle is observed. Root mean square calculation of velocity is made. The turbulent intensity of spray field and its influence on mixture distribu- tion are analyzed from the standard deviation fluctuation of node velocities.