混流式水泵水轮机泄漏量的计算及分析

Calculation and analysis of leakage of Francis pump-turbine

为了确定混流式水泵水轮机泄漏量的大小,分别采用基于经验参数的理论公式法和基于N-S方程、RNG k-ε湍流模型、结构化网格技术的CFD数值模拟法,对某大型可逆式水泵水轮机分别在60%,70%,80%,90%的导叶开度下进行了泄漏量计算,并对2种方法的计算结果进行了对比分析.结果表明:理论公式法涉及经验参数的选取,对计算经验的依赖程度较大,具有一定的盲目性和不准确性,同时在对机组水轮机工况下的泄漏量进行计算时,由于各个工况点的水头相等,导致计算出的不同工况下机组泄漏量曲线是一条平行直线,并没有反映出泄漏量随工况变化的真实规律;将CFD数值模拟法计算的性能曲线与试验性能曲线进行比较,结果显示吻合度较高,验证了CFD数值模拟法的正确性及对间隙泄漏问题计算的可行性,可以较为准确地描述间隙泄漏问题,克服了理论公式法在计算时出现的弊端.

In order to determine the leakage of Francis pump-turbine, the theoretical formula method was employed based on empirical parameters, and the CFD numerical simulation method using Navier -Stokes equations, RNG k -ε turbulence model and structured grid technology was used to calculate the leakage of a large reversible unit with the guide vane opening at 60% , 70% , 80% and 90% , and then a comparative analysis of the results of this two methods was done. The results show that the theoretical formula method involves the selection of empirical parameters, which leads a larger degree of dependence on computing experience, and has certain blindness and inaccuracy. When calculating the leakage under the turbine condition, the head of the points are equal, thus leading to that the leakage curve is a parallel straight line. It cannot reflect the real law between the leakage and the working con- ditions. By comparing the performance curves calculated by the CFD numerical simulation with the testing performance curves, the agreement of the results are better, verifying the accuracy of CFD numerical simulation and the feasibility of the clearance leakage calculation. It can describe the clearance flow more accurately and overcome the drawbacks of the theoretical method in calculation.