叶轮几何参数对离心泵断裂空化性能的影响

Effects of impeller geometry parameters on fracture cavitation performance of centrifugal pump

为了改善离心泵的空化性能,研究离心泵断裂空化发生机理,对1个比转数为134的单级离心泵进行空化性能的模拟计算,通过改变叶轮的进口直径、叶片进口安放角和叶轮出口宽度进行数值模拟,根据模拟结果预测了模型泵的空化性能,并分析不同空化余量下叶轮流道内的气泡分布.研究结果表明:在额定工况下,随着进口压力的降低,空泡首先在叶片背面进口边附近产生,然后随着叶轮旋转沿流道向叶轮出口扩散,并随着流道过流面积的增加向叶片工作面扩展;叶轮流道内气泡呈不对称分布的主要原因是由于叶轮与蜗壳的动静耦合作用,使叶轮叶片表面的压力分布不对称造成的;与叶轮进口参数相比,叶轮出口宽度的变化对离心泵空化性能的影响不大;当增大叶片进口安放角后,减小了叶片的弯曲程度,叶片进口的过流面积增大,空化性能得到改善,相同进口压力下的空化余量值减小;在进口直径和进口安放角的变化过程中,均存在一个最佳值,最佳值对离心泵效率和空化性能的提高具有重要意义.

To improve the cavitation performance and study the cavitation fracture mechanism of the centrifugal pump,the numerical simulation of cavitation performance in a specific speed 134 centrifugal pump was carried out by changing the impeller inlet diameter,the blade inlet angle and the impeller outlet width. Then the cavitation performance was predicted according to the simulation results,and the bubble distribution in the impeller passage was analyzed under different net positive suction heads.Simulation results show that with the decreasing of the inlet pressure,the cavitation bubble first occurs at the blade inlet of the suction side,then it diffuses to the impeller outlet with the rotating of the impeller at the same time,and the bubbles flow to the pressure side when the flow area becomes bigger.The main reason why the bubble in the impeller passage is asymmetric is that the pressure on the surface of the impeller is asymmetric because of the static coupling between impeller and volute. Compared to the impeller inlet parameters,the change of the impeller outlet width affects the cavitation performance less. The bending of the blade becomes smaller when the inlet angles become bigger,the flow areas in the blade inlet increase,the cavitation performance is improved and the value of the NPSH decreases under the same inlet pressure. There exists an optimum value for the change of the impeller inlet diameter and the blade inlet angle,which is important to the improvement of the centrifugal pump＇s efficiency and the cavitation performance.