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| Analysis on rotor strength and mode of pump-turbine with splitter blades |
| ZHANG Jinfeng1, SONG Haiqin1*, ZHANG Fan1, CAI Haikun1, LAI Liangqing1, HONG Qiuhong2 |
| 1. National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2. Kunming Jiahe Science & Technology, Ltd., Kunming, Yunnan 650501, China |
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Abstract This study considered a model of a pump-turbine with splitter blades operating in pump mode. Vibration characteristics of the rotor of the pump was analyzed based on CFD and FSI methods. Steady simulations of flow conditions under three opening degrees; small opening degree of 9.8°, optimal opening degree of 17.5° and the large opening degree of 24.8° were conducted. The results under rated working conditions were imported into the rotor structure to realize unidirectional fluid-structure coupling. Further, deformation and equivalent stress of the rotor with pre-stress were analyzed and the wet and dry modes of the runner were also calculated to analyze vibration characteristics of the runner under different conditions. The analysis revealed that deformation of the runner under the pre-stress corresponding to different openings is basically the same as the equivalent stress distribution and the deformation of the runner mainly occurs on the low-pressure side of the upper crown. In addition, vibration sectors were divided in the circumferential direction to describe the characteristics of the vibration shape according to the number of pitch diameters. It was found that the relative amplitude of the low-pressure side of the upper crown and lower ring of the runner in each sector is relatively large. Furthermore, the additional mass of water in the wet mode has little effect on the modal characteristics of the runner, but it will have a significant impact on the amplitude. Lastly, the influence of pre-stress on the natural frequency of the structure is small and can be ignored, while the natural frequency of the structure will decrease significantly in the wet mode,indicating that the additional mass effect of water should be fully considered when the vibration characteristics of the structure is analyzed.
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Received: 11 August 2020
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