轴对称腔体内淹没射流空化的滞后效应

摘要

Experimental measurements and high speed video observations were carried out to study the cavitating flow properties of submerged jet in an axis-symmetrical cavity.The variations of cavitation number and Reynolds number (Re)of working jet in cavity chamber and outlet nozzle were obtained.From the experimental results,it is found that,in a certain range of Re,the jumping variation of cavitation number comes about,while the cavitating state in cavity chamber changes suddenly from small diameter bubbles to large diameter bubbles.The critical Reynolds number at the occurance of cavitation number jumping in the decreasing process of working jet Re is smaller than that in the increasing process of working jet Re,which shows a hysteresis effect between the two variation processes.Within the range of cavity chamber length in experiments,the critical Reynolds number is linearly related to the chamber length in both increasing and decreasing process of working jet Re variation,but the slope of cavitation number jumping in decreasing process is smaller than in increasing process.The hysteresis effect is enlarged as the chamber length increases.%对轴对称腔体内淹没射流的空化流动特征进行了高速摄像观测和试验研究，得到了腔体内和下喷嘴出口管内流动的空化数与工作射流雷诺数（Re）的变化规律。试验研究发现，在一定的 Re 范围内，空化数随 Re 数发生跳跃变化，腔体内空化形态发生突变，空泡形态由突变前的小直径空泡剧变为突变后的大直径空泡。Re 减小变化过程发生空化数跳跃的 Rec 小于 Re 增大变化过程发生空化数跳跃的 Rec ，两者存在滞后效应。在试验的腔长范围（6≤Lc ／d1≤13）内，Re 增大变化过程和 Re 减小变化过程的 Rec 均随腔长线性变化，但后者变化的斜率小于前者，滞后效应随着腔长的增长而扩大。