诱导轮超同步旋转空化传播机理

Inducer super-synchronous rotating cavitation propagation mechanism

为了揭示超同步旋转空化的传播机理,对二维平板叶栅内部非定常空化流动进行数值模拟研究,叶栅的几何参数和模拟工况均来自真实诱导轮试验结果。结果表明:仿真预测的叶栅空化断裂点与试验结果接近,随空化数下降空化区的演变规律与试验结果一致。在一定的空化数范围出现传播频率比为1.1~1.4的旋转空化现象,对流场细节的深入分析发现空化区与来流冲角的相互作用是空化区波动沿周向超同步传播的机理。空化区与叶片前缘的冲角是呈正相关的,同时空化区增大会在尾缘诱发顺时针涡扰动,空化区减小会在尾缘诱发逆时针涡扰动,当扰动达到叶片喉部位置时,会对相邻叶片产生影响,空化区增加会导致相邻叶片冲角减小,相应空化区也减小,空化区减小会导致相邻叶片前缘冲角增大,相应空化区增大,如此循环往复,形成空化区波动沿周向的超同步传播。

In order to explain the propagation mechanism of SRC(super-synchronous rotating cavitation),the unsteady cavitating flow inside a 2D plate cascade was numerically investigated,the geometric parameters and working condition parameters were from real experimental results.It was found that the cavitation breakdown point of cascade is close to the experimental results,the evolution of cavity with reduction of cavitation number is in consistent with the experimental results.The propagation ratio of SRC which occurs in a specific cavitation number range is 1.1~1.4,the detailed analysis of flow field indicates that the interaction of cavity and incidence angle is the super-synchronous propagation mechanism of cavitation fluctuation.The cavitation development and incidence angle are positively related.The cavitation expansion will induce clockwise vortex disturbance near the trailing edges,and cavitation shrink will induce anticlockwise vortex disturbance.When the disturbances arrive the throat position of the blades,they will affect on the adjacent blade.The incidence angle of adjacent blade leading edge will decrease due to cavitation expansion,the corresponding cavitation area decreases.The incidence angle of adjacent blade leading edge will increase due to cavitation shrink,the corresponding cavitation area increase.The cavitation areas on the three blades move in circles,thus the SRC is formed.