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| Analysis on improvement of model draft tube by vortex-generators |
| Tian Xiaoqing1, Zheng Yuan2, Pan Huachen3, Sun Bin1 |
| 1.College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 2.College of Energy and Electrical Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 3.School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou, Zhejiang 310018, China |
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Abstract In order to develop a new type of draft tube with vortex-generators, the working mechanism of vortex-generators was analyzed in some extent, then a series of experimental model draft tubes with vortex-generators were designed by combination with the theory of draft tube; finally, verifying simulations and experiments were conducted on those models. In accordance with geometrical characteristics of the model draft tube, a structured mesh was generated by considering the near-wall function. The share stress transport(SST)model was used in the turbulent flow simulation. The blades of vortex-generator were installed between two sections in the tube, one is the section where a vortex starts to be generated and the other is the section where the vortex begins to be developed, then 55 different wor-king conditions were simulated. Finally, energy recovery coefficients were calculated, and the optimum blade installation was identified. It was shown that two pairs of counter rotating vortex-generators should be installed in the section where a vortex starts is generated and the angle between the generator and the draft tube center line should keep being 15°. A conforming experiment was conducted under this installation scheme, and 3.2% improvement in energy recovery coefficient have been observed. This suggests that the position where vertex-generators are installed is the section where a vortex starts to occur. This proposal can be useful to hydropower stations being constructed and those being refurbished.
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Received: 17 May 2012
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