Optimization design of horizontal Francis turbine with two runners
ZHENG Yuan1, YANG Chun-Xia2, ZHOU Da-Qing1, SHEN Ming-Hui3, LI Xiao-Xu2
(1. College of Energy and Electrical Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 2. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 3. Xinxiang Power Supply Company, Henan Electric Power Company, Xinxiang, Henan 453000, China)
The fluid dynamics through a horizontal Francis turbine with two runners in a power station aboard was analyzed by using a CFD code, suggesting the turbine was subject to a low efficiency and poor cavitation performance because of significant hydraulic loss caused from complex flow passage geometry and unsmooth flow. Since the update of stationary flow passages was unallowable, just the turbine runners can be optimized. It appears that there are three ways to optimize the runners, i.e. change the blade shape, adjust the runner crown profile and alter the relative location of two runners. Based on the N-S equations, Spalart-Allmaras turbulence model and SIMPLIC algorithm, the threedimensional, steady turbulence flow in the optimized turbine was simulated, the details of flow were obtained and the hydraulic performance was predicted. The results showed that the flow rate was increased to 28.55 m3/s, the left and right runner efficiency were reached to 92.24% and 91.78%; when the runner of type Ⅲ and crown profile of type B and the two runners blades having a stagger pattern were adopted. Meanwhile, the cavitation performance of the runners of type Ⅰ, Ⅱ and Ⅲ was analyzed, showing the runner of type Ⅲ has the best cavitation behavior.
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