泵叶轮出口宽度对蜗壳内压力脉动强度的影响

Effects of the outlet width of pump impeller on pressure fluctuation intensity in volute

为了研究低比转数离心泵叶轮出口宽度对蜗壳内压力脉动强度的影响,将叶轮出口宽度分别设计为5、6和7 mm,并保持蜗壳和叶轮其他几何参数不变。应用ANSYS CFX 14.5进行数值计算,对比了定常数值计算与外特性、粒子图像测速(particle image velocimetry,PIV)试验结果,验证了数值计算的可信度,3个方案的扬程、效率均满足设计要求。在非定常数值计算中,引入压力脉动强度表征3个旋转周期内压力脉动的累积效应。结果表明:对于同一叶轮出口宽度,小流量下蜗壳内压力脉动强度最大,大流量次之,而在设计工况下,压力脉动强度及其梯度均是最小的;由于叶轮和蜗壳的时序干涉作用,隔舌处出现压力脉动强度的大梯度变化;蜗壳进口宽度与叶轮出口宽度之比为3时,该低比转数离心泵的性能满足设计要求,且压力脉动强度较低,综合性能较优。

To investigate the effects of impeller outlet width on pressure fluctuation intensity in the volute of a pump with low-specific-speed, the impeller outlet widths were designed as 5, 6, and 7 mm. Other geometric parameters, including impeller and volute, were unchanged. The commercial software ANSYS CFX 14. 5 was applied to solve the steady and unsteady Reynolds-averaged Navier-Stokes equations. The head curves and dimensionless mean velocity in the volute calculated by the steady numerical simulations displayed good agreement with those obtained by external characteristics and PIV experiments; therefore, the numerical simulation results were reliable to a certain extent. Furthermore, the ex-ternal characteristics of three schemes met the design requirements. In the unsteady simulations, a dimensionless stand-ard deviation coefficient of pressure fluctuation for three entire revolution periods was defined as the pressure fluctuation intensity. For the same impeller outlet width, the magnitude and gradient of pressure fluctuation intensity in the volute were the largest under the partial load operating condition, moderate under the overload operating condition, and mini-mum under the design operating condition. The gradient of pressure fluctuation intensity in the tongue region was larger than that in any other region because of the rotor-stator interaction. When the ratio of the volute inlet width to impeller outlet width was around 3, the performance and operating reliability of this low-specific-speed pump were in good bal-ance, and the fluctuating intensity was low and comprehensive performance was high.