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| Layout position of bionic non-smooth structure on blades of centrifugal pump |
| DAI Cui1, CHEN Yiping1, DONG Liang2*, WANG Zhaoxue1 |
| 1. School of Energy and Power Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2. National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu 212013, China |
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Abstract In order to explore the correlation between drag reduction rate and layout position of bionic non-smooth structure, and the sensitivity of hydraulic efficiency of centrifugal pump to the structure, bionic non-smooth structures were decorated on six different locations on blade two surfaces of a centri-fugal pump, respectively; and six designs were resulted.The hydraulic characteristic parameters and internal flow of the centrifugal pumps with these designs were studied numerically by using ANSYS CFX software at a duty point.An optimal design was decided by comparing hydraulic efficiency and drag reduction rate among six designs. Then, the optimal layout design was compared and analyzed against the existing usual layout position of bionic non-smooth structure in the whole range of flow rate.Finally, the influence of roughness on the performance and flow in the pumps were clarified in terms of the same layout position of bionic non-smooth structure.The results show that the hydraulic efficiency of the pumps with bionic non-smooth structurewas less or equal to the efficiency without the structure, but the average shear stress on the blade surfaces was lowered by about 12.7%. The bionic non-smooth structure unit in any position could produce a drag reduction effect in some degree, however, the drag reduction effect produced by an adjacent bionic non-smooth unit did not show a linear relation of superposition in an intersected position. In the whole range of flow rate, the layout position of bionic non-smooth structure in the middle of blade suction side always leads to both higher hydraulic efficiency and larger drag reduction rate, compared with the layout arranged near the outlet on blade suction side. Additionally, the hydraulic efficiency change and drag reductionrates in two layouts showed a similar trend versus flow rate.Unfortunately, the efficiency change rate was too tiny to be considered as a standard to evaluate the bionic non-smooth structure, while the drag reduction rate was substantial. It is suggested that the bionic non-smooth structure should be arranged in the position suffering from the largest shear stress for a better performance and pit elements in the structure should be apart with large enough spa-cing to increase the average drag reduction rate. The results demonstrated that even though a rough surface could form a low-velocity layer near a wall like a bionic surface, the drag reduction was unachie-vable because only macroscopic bionic units play a positive role in drag reduction. The results revealed that the layout position has limited influence on the hydraulic efficiency of centrifugal pump.For a fixed number of pits applied, the pits should be placed in the position as close as possible where the maximum shear stress is experienced.
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Received: 23 October 2018
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