半开式单叶片螺旋离心泵叶轮内部压力脉动研究

Internal Pressure Fluctuation of Semi-open Screw Centrifugal Pump with Single Blade

摘要:

半开式单叶片螺旋离心泵由于叶轮结构不对称、叶轮与蜗壳之间的动静耦合作用以及叶顶间隙泄漏等因素的共同作用，泵内部伴随着很强的压力脉动效应，不利于机组的安全运行。针对比转数ns为237的半开式单叶片螺旋离心泵，以CCM+为仿真平台，采用多面体网格划分计算区域，进行全流场定常/非定常数值计算，监测叶轮叶片进口附近及叶片中部区域的压力脉动。结果表明：数值计算监测得到的压力脉动趋势与试验结果基本一致，但在监测点位置刚好离开叶片吸力面一定距离，并与同一轴向高度处叶片压力面具有较大圆周距离范围内时，数值计算得到的压力波动变化趋势与试验结果存在一定差异。结合数值计算得到的监测点附近压力云图分析发现，当叶片压力面逼近监测点时，压力达到最大值，并在叶片圆周厚度1/3处时，压力达到最小值。另外，从压力最低点到压力最高点范围内，2个监测点位置在5个工况下，压力波动均呈现出3种斜率变化。

Abstract:

Strong pressure fluctuation existed in semi-open centrifugal screw pump with single blade under the combined influence of asymmetric impeller structure, static and dynamic coupling effects between impeller and volute and tip clearance leakage etc., which was not conducive to the safety operation of the units. The semiopen screw centrifugal pump with blade and specific speed of 237 was taken as research object, STAR—CCM+ simulation platform was used, calculation area was partitioned with polyhedral mesh, the steady and unsteady numerical calculations of whole flow field were conducted, meanwhile, the outer characteristic was predicted and the pressure fluctuation of inlet and middle area of the blade was monitored. Results showed that the error between predicted outer characteristic and test results was very small and the trend of monitored pressure fluctuation was basically consistent with the test, but when there was a distance between monitoring points and suction surface and a large circumferential distance from the same axial height of pressure surface, the results of numerical calculation were different from the test results. It can be found from the pressure time-domain diagram of two monitoring points that pressure fluctuation span of Pre2 was larger than that of Pre1, which was due to the work capacity of blade’s middle area was better than that of inlet area. Analysis of pressure contour of monitoring points showed that when the pressure surface was close to the monitoring point, pressure reached its maximum value, and at 1/3 circumferential thickness area of the blade, pressure reached its minimum value. In addition, in the range of the lowest point to the highest point, the pressure fluctuation of two monitoring points presented three kinds of slope change under five working conditions.