Calculation and analysis of leakage of Francis pump-turbine
Min Zheng1, Liang Changping1, Dong Zhiqiang1, Liu Dianxing1, Qin Daqing2, Wei Xianzhu2
1.College of Energy and Power Engineering, Lanzhou University of Technology, Lanzhou, Gansu 730050, China; 2.State Key laboratory of Hydropower Equipment, Harbin, Heilongjiang 150001, China
Abstract：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 conditions. 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.
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