泵反转液力透平速度滑移的计算与分析

Calculation and analysis on velocity slip of pump as turbine

针对离心泵反转液力透平(PAT),采用RNGk-ε湍流数值模拟分析了泵工况(正转)与透平工况(反转)的速度滑移特性,揭示了滑移系数的变化规律,提出了考虑滑移系数时计算PAT泵工况与透平工况扬程换算关系的新方法.结果表明:随着流量增加,泵工况滑移系数增大,透平工况滑移系数减小.速度滑移引起叶轮内的附加水力损失,透平工况流量大于额定流量时,其滑移系数小,叶轮内附加水力损失小,这是液力透平大流量时效率高的原因之一.采用PAT换算关系新方法计算了不同比转速下的6个PAT算例的扬程换算值,并将结果与未考虑滑移系数的方法比较,经实验验证该方法的平均误差约减小5%~20%.

Focus on the pump as turbine （PAT）,the slip phenomenon was analyzed based on RNG （renormalization group）k-εsimulation,the distribution of slip factor was revealed for pump mode and turbine mode,and a new method of head relationship between pump and turbine mode was proposed considering slip factor.Results show that slip factor is increasing with the increase of discharge in pump mode but inversely in turbine operation.Relevant hydraulic loss in impeller passage is induced by slip phenomenon.Slip strengthened in part-load region,as a consequence,hydraulic efficiency is low,on the contrary,it weakened in over-load region,therefore,hydraulic efficiency of PAT is high relatively.Then the head relationship between pump mode and turbine mode for 6 selected PATs were calculated based on the proposed new method,and results were compared with those without consid-ering the slip coefficient,which shows that the average error is reduced by 5%～20% using proposed new method.