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| Numerical simulation of freesurface flow in updraftfreeexitflow hydropower turbine |
| YANG Wei, LIU Zhu-Qing, WU Yu-Lin, GAO De-Yu |
| (1.College of Water Conservancy and Civil Engineering, China Agricultural University, Beijing 100083, China; 2. Department of Thermal Engineering, Tsinghua University, Beijing 100084, China； 3. College of Engineering, Iowa State University, Iowa 50011,USA) |
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Abstract To study the turbine′s internal flow more accurately and improve its hydraulic performance, a geometrical model of the whole flow passage, including casing and runner, was established. An unstructured grid was applied to segment the runner, encrypt the grids on the inner surfaces of the runner blades and the casing guide vane. The sizes of grid clusters were made to meet the y+ for turbulence simulation. Based on RNG k-ε turbulence model, the internal flow was simulated. Taking the effect of free surface flow into consideration, by applying volume of fluid method, a simulated internal flow in an updraftfreeexitflow turbine was obtained. On the basis of the computation of simulation results, the internal flow loss was analysed. It was found that the largest loss was between the stay vanes and the runner inlet, which amounted to 73% of the total loss. The flow details show that the step structure of the area was the direct cause of the loss and exacerbated the runner′s inflow condition. Accordingly, where and how to improve the turbine′s energy performance was inferred.
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Received: 15 November 2012
Published: 30 April 2013
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