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| Internal flow and analysis of its unsteady characteristics in centrifugal pump with ultra-low specific-speed |
| CHEN Jie1, WANG Yong1, LIU Houlin1, SHAO Chang1, ZHANG Xiang2* |
| 1.National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2.Key Laboratory of Fluid and Power Machinery, Ministry of Education, Xihua University, Chengdu, Sichuan 610039, China |
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Abstract In order to explore internal flow and its unsteady characteristics in ultra-low specific-speed centrifugal pumps more comprehensively, an ultra-low specific-speed centrifugal pump with a specific-speed ns=25 was chosen as a study object. Then numerical simulations of the unsteady three-dimensional fluid flow in the pump were carried out. Finally, the internal flow field, radial thrust on the impeller and the pressure fluctuation of fluid in each section of the volute were analyzed. The results show that there appears vortices in various sizes and numbers in flow channels of the impeller under different flow conditions. A high velocity zone is found in two adjacent channels near the tongue, however, the zone disappears gradually with the increase of flow rate. Under high flow rate conditions, the area of the low velocity zone decreases gradually, the size and number of vortices reduce steadily, and the rela-tive velocity distribution in the impeller becomes uniform gradually. The orientation and magnitude of radial thrust on the impeller vary constantly, showing a hexagram pattern. The amplitude of radial thrust decreases gradually with increasing flow rate, but its main excitation frequencies are all the blade passing frequency or its integer multiples.The peak pressure fluctuation in each section of the volute decreases along the flow path and the main excitation frequencies are all the blade passing frequency or its integer multiples. This fact suggests that the impeller-volute interaction is one major factor influencing pressure fluctuation in the volute.These results have provided useful reference for optimum design of the ultra-low specific-speed centrifugal pump and selection of its feasible operating flow rate range.
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Received: 10 November 2016
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