低比转速多级泵间隙尺寸改变对内部流场及其性能的影响

Influence of Change of Gap Size on Flow Field and Performance in Low Specific Speed Multistage Pump

为研究低比转速多级泵间隙尺寸的改变对内流场及其性能的影响,应用CFX软件对带间隙模型泵进行数值模拟,设计了12个间隙组合模型,分析了泵的外特性、间隙泄漏量、叶轮出口与导叶进口速度压力的变化规律。结果表明,随着间隙尺寸的增加泵扬程和效率均有所下降;叶轮口环的泄漏来自遭到撞击改变方向的叶轮出口流体,导叶口环的泄漏来自次级叶轮进口的流体;间隙对泵的影响程度依次为叶轮口环>导叶口环>叶轮与导叶的运转间隙;叶轮出口流出的液体进入导叶时极大地阻断了叶轮泵腔之间与叶轮导叶轴向间隙的流体交换。数值模拟结果较估计值仍然偏高,数值模拟对单一模型的准确度有待商榷,说明多组模型对比十分必要。研究成果为进一步深入分析奠定了基础。

In order to investigate the influence of change of gap size on internal flow field and performance in low specific speed multistage pumps, numerical simulation of the model pump with clearance was carried out by CFX software. Twelve sets of models with different gap sizes were established for numerical analysis. The change laws of the pump external characteristics, the leakage of the gap, the outlet of impeller and guide vanes' inlet velocity and pressure were analyzed. The results show that the pump head and efficiency decrease decrease with the increase of clearance size;The leakage of the wear-ring comes from the fluid of impeller outlet that crashed and the direction has changed, and the leakage of the guide vanes' wear-ring comes from the inlet fluid of the secondary impeller;The degree of influence of all gaps on the performance of the pump is sorted as: the wear-ring > the guide vanes' wear-ring > the impeller and vane running clearance. With the liquid from the impeller outlet entering the guide vanes, the liquid block the exchange of the fluid in the clearance between the impeller chamber and the impeller guide vane. However, the numerical simulation is still higher than the estimated value. This indicates that the accuracy of numerical simulation to a single model is questionable;Multiple model comparisons are always beneficial and necessary. The research results lay a foundation for further in depth analysis.