切割叶轮对离心泵气蚀性能影响的数值分析

Numerical analysis of influence of cutting impeller on cavitation performance of centrifugal pump

切割叶轮作为离心泵运行工况的调节方式应用普遍。伴随叶轮的切割,泵效率下降,气蚀性能变差。为了获得切割叶轮导致泵气蚀性能变差的原因,以某型号的双吸离心泵为研究对象进行了数值模拟。结果表明,叶轮的切割不会使泵进口的吸入性能变差,即从泵的入口到叶轮进口的损失没有变化,叶轮进口的低压区域也无变化;叶轮切割导致的扬程下降致使对气蚀性能的评判指标(3%的扬程降)改变,即必需气蚀余量变大。

To meet different operating conditions of centrifugal pump operation,impeller cutting is widely used as the adjustment mode of centrifugal pump operating conditions.With the decrease of impeller diameter,pump efficiency declines and the cavitation performance deteriorates.In order to obtain the reasons for the deterioration of pump cavitation performance caused by cutting impeller,a double suction pump designed at common specific speed is studied via computational fluid dynamics(CFD).The results show that suction performance does not go bad with the decrease of impeller diameter because the loss between pump inlet and impeller suction inlet keeps same among these impellers,and so does the low pressure area.The head of pump declines because of the decrease of impeller diameter,so the Net Positive Suction Head Required(NPSHr),namely based on 3%head decline criteria,become higher.