基于时间分割法的柴油机交叉孔喷油嘴喷雾场粒子特性

Droplet Characteristics in Spray Field of the Intersecting-Hole Nozzles for Diesel Engines Based on Time Dividing Method

采用相位多普勒粒子分析仪(PDPA)对柴油机V形交叉孔油嘴和单孔油嘴的喷雾场粒子特性进行测量,通过时间分割法对测量结果进行深入分析.结果表明,在喷雾轴向Z=40,mm的位置上,靠近喷雾轴线的区域内两种交叉孔油嘴与单孔油嘴的粒径大小差别不大,但随着测量点的径向坐标增大,交叉孔油嘴的粒子直径逐渐小于单孔油嘴.在Z=60,mm位置上,与单孔油嘴的结果相比,两种交叉孔喷油嘴的粒子算术平均直径(AMD)和索特平均直径(SMD)更小.同时,交叉孔的交叉角增大会对液滴的进一步细化起促进作用,相比于单孔油嘴,交叉孔2喷油嘴的粒子AMD和SMD减小了近30%.对时间分割法划分的4个阶段粒子特性进行分析发现,F阶段的粒子速度高达70,m/s,喷射过程中的系统数据率较低,PDPA的大量粒子信息均来自于喷油结束的T阶段,此时粒子速度为零.交叉孔喷油嘴的扇状喷雾结构对油气混合的促进作用使粒子AMD随时间变化而不断减小.同时,与喷雾内侧相比,在喷雾外侧两交叉孔喷油嘴之间的粒径差异变小,相对于单孔喷油嘴,在粒径方面的优势变得明显.

Droplet characteristics in spray fields of two intersecting-hole（IH）nozzles and one single hole （SH） nozzle for diesel engines were measured by means of phase Doppler particle anemom-etry （PDPA）. Droplet data was analyzed using the time dividing method. Experimental results show that the difference in droplet mean diameter between IH and SH nozzles is insignificant in the region near noz- zle axis at Z = 40 mm. When radial coordinate of measurement is increased, the droplet sizes of the IH nozzles become smaller than those of SH nozzle. Comparing to SH nozzle, the droplet sizes of IH nozzles decrease further at Z = 60 mm, due to the improvement of intersecting angle on the decrease of droplet size. In particular, droplet AMD and SMD of IH 2 reduce by 30% compared with those of SH nozzle. In the four stages defined by Time Dividing Method, droplet velocity reaches 70 m/s at stage F. Data rate of PDPA is limited during the injection. Large numbers of droplet data with low velocity were obtained in the stage T after injection. Promotion of fan-shape spray on the fuel/air mixing helps to decrease the droplet AMD. Difference in droplet size between IH 1 and 2 nozzles becomes smaller in the peripheral region. Comparing with SH nozzle, the advantage of IH nozzles on droplet size is more obvious.