反转泵液力透平速度滑移机理

Research on Slip Phenomenon of Pumps as Turbines

速度滑移对液力透平的水力性能和内流特性有一定影响。以反转泵液力透平为研究对象,评估不同湍流模型对液力透平水力性能影响的敏感性,通过数值模拟与试验值误差分析发现,采用RNG k-ε湍流模型预测液力透平水力性能具有较高的可信度。选用RNG k-ε湍流模型和CFX17.0,分析透平内速度滑移机理及速度滑移量化指标,进一步对比液力透平和离心泵速度滑移的大小及流动机理。研究发现:液力透平叶轮内存在速度滑移现象,速度滑移导致透平水头降低,并诱发了附着于叶片工作面的旋涡。透平滑移系数随比转速变化而变化,数值在0.2～0.4。比较反转泵液力透平透平工况与泵工况的滑移系数发现:当比转速大于50时,透平工况的滑移系数比泵工况的小,比转速低于50时,出现了透平工况滑移系数高于泵工况的情形。

Slip phenomenon is known to strongly influence the performance of pumps as turbines(PAT). In the present work, the standard k-ε model,RNG k-ε model,standard k-ω and SST k-ω model are adopted to simulate the hydraulic performance of PAT, and the experiment values are in a good agreement with CFD result by using RNG k-ε model. Therefore, the slip phenomenon in turbine impeller is studied and the slip factor is estimated for each PAT using RNG k-ε model. Then the slip phenomenon in turbine mode was compared with pump mode. It is observed that slip phenomenon occurs in PAT, and it lead to the head decrease, besides, the vortex flow is generated in PAT’s flow passages near pressure side of blade. The slip factor varies with the specific speed of PAT, and its value is 0.2-0.4 approximately. In comparison with pump mode, the slip factor of turbine mode smaller than pump mode when the specific speed above 50, but larger when it below 50.