设计工况下离心泵作透平的压力脉动特性的数值模拟研究

Numerical simulation study on pressure fluctuation characteristics ofcentrifugal pump as turbines with normal condition

对比转速为n s=24.7的普通悬臂式离心泵作透平时在设计工况下的压力脉动特性进行了数值模拟研究,在计算中采用了SST k-ω湍流模型及q准则的涡识别方法,数值模拟方法对于泵作透平性能预测结果与经验方法较吻合。在数值模拟中采用了5套系统加密的网格进行网格无关性验证,进而在考虑计算成本及准确性的基础上选取了一套合适的网格进行设计工况下(Q=64 m^3/h)的压力脉动特性的研究。结果表明:在设计工况下,泵作透平的蜗壳内压力脉动现象主要是由转动的叶轮与静止的隔舌相互干涉引起,蜗壳内不同截面上的不均匀流动可能诱导蜗壳内的低频脉动现象;尾水管受到上游部件动静干涉的压力脉动影响,管内涡带形态扭曲,其扭曲方向与叶轮旋转方向一致。

In this paper,the pressure fluctuation characteristics of ordinary cantilever centrifugal pump with the specific speed of n s=24.7 are studied by numerical simulation under normal conditions.The SST k-ωturbulence model and q criterion vortex identification method have been used in the calculation.Performance prediction results of pump as turbines by numerical simulation method are in good agreement with the empirical method.In the numerical simulation,five sets of grids are used for grid-independent analysis,and then a set of a suitable grid is selected to study the pressure fluctuation characteristics of normal conditions(Q=64 m^3/h)based on considering the calculation cost and accuracy.The results show that under the normal condition,the pressure fluctuation in the volute of the pump as turbines is mainly caused by the interaction between the rotating impeller and the static tongue.The uneven flow on different sections of the volute may induce the phenomenon of low frequency pulsation.The draft tube is affected by the pressure fluctuation caused by the rotor-stator interaction of the upstream components.The shape of the vortex in the draft tube is twisted,and the twist direction is consistent with the motion direction of the impeller.