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| Numerical simulation of excess output condition of a pump-turbine based on compressible calculation |
| Liu Jintao1, Li Xiaopeng2, Guo Lei3, Wang Leqin3 |
| 1.Beijing Institute of Control Engineering, Beijing 100190, China; 2.Central Power Supply Company, Sinopec Shengli Power Management Corporation, Dongying, Shandong 257000, China; 3.Institute of Chemical Machinery Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China |
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Abstract The flow in the runner was speed up at the excess output condition, and flow separation may occur in the runner and the pressure fluctuation was amplified. To study the hydraulic instability of a pump-turbine at excess output condition, a 3D pump-turbine model was set up. Unsteady,incompressible flow was used for numerical simulation using SST k-ω turbulence model under 110% rated power condition. The inner flow as well as the pressure fluctuation in the pump-turbine was analyzed. The law of evolution of pressure fluctuation in the field between the casing and the runner was investigated. Calculation results were compared with the experimental data. The results show that the amplitude of pressure fluctuation increases along the flow direction near the region of vanes. The dominant frequency of pressure fluctuation changes into half of the two times of blade passing frequency between guide vanes and stay vanes. The ratio of the relative amplitude of 9 fn frequency to the amplitude of mixture frequency decreases in the domain of guide vanes. The separation flow at the pressure side in the runner, as well as a large vortex rope in the draft tube, can be found at excess output condition.
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Received: 11 June 2012
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