叶片包角对高比转数离心泵性能的影响

为研究设计工况下叶片包角对高比转数离心泵性能的影响,以一台比转数为185的单级单吸离心泵为研究对象,在保证泵体和叶轮其他几何参数相同的前提下,将叶片包角分别设计为110°,115°,120°,125°和130°. 应用ANSYS CFX 14.5软件对离心泵内流场进行数值计算.结果表明:叶片包角对外特性有显著影响,包角过大,扬程和水力效率整体下降;当叶片包角增大到130°时,最佳效率点向小流量偏移近20%;同时,随着叶片包角的增大,叶轮进口低压区增大,更容易发生汽蚀;叶片包角从110°增大到115°时,蜗壳内流动更加平顺. 当叶片包角增大到125°时,隔舌附近出现明显的低速旋涡区,随着包角进一步增大,旋涡区域扩大且向出口处移动;此外,当叶片包角为120°时,各监测点的压力脉动幅值较低,说明对于动静干涉作用的影响,叶片包角存在一个最优值. 针对叶片包角为120°的模型泵进行了性能试验,对比发现数值计算的结果与试验结果趋势一致,表明数值计算方法是可信的,对高比转数离心泵水力设计具有一定的参考价值.

Effects of blade wrap angle on performance of high specific speed centrifugal pump

In order to investigate the influence of blade wrap angle on high specific speed centrifugal pump performance under design condition, a single-stage, end-suction centrifugal pump with a specific speed of 185 is taken as study object. Firstly, five impellers respectively with 110°, 115°, 120°, 125°and 130° wrap angles are designed when the rest geometric parameters remain unchanged, then the flow fields in the pump with these impellers are calculated numerically by using software ANSYS CFX 14.5. The results show that the blade wrap angle has a significant impact on external characteristics. If the wrap angle is oversized, the head and the hydraulic efficiency will decline. When the wrap angle increases to 130°, the best efficiency point migrates about 20% to part-load region; in addition, the low pressure zone at the impeller inlet is enlarged with increasing wrap angle, leading to cavitation more easily. When the wrap angle increases from 110° to 115°, the flow in the volute is smoother. However, when the angle is 125°, an obvious vortex region with low velocity appears around the tongue, further it is expanded and moves to the impeller outlet gradually with increasing warp angle. Also, when the wrap angle reaches to 120°, the pressure fluctuation amplitude at every monitoring point is relatively low, showing there is an optimal wrap angle for rotor-stator interaction. The performance of the pump with 120° wrap angle is measured and it is found that the results of numerical simulation are in agreement with the measurements. This study has provided some reference significance to the development of a high specific speed centrifugal pumps with better performance.