| MECHANICAL ENGINEERING |
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Design method based on load control of a three-segment quartic function and experiments for centrifugal pumps |
| LU Yangping, TAN Lei |
| State Key Laboratory of Hydroscience and Engineering, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China |
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Abstract [Objective] Centrifugal pumps are a common type of hydraulic machinery widely used in water transfer, energy storage, agricultural irrigation, oil production, and more. Owing to system regulation demands, these pumps often need to switch operating conditions and, therefore, operate for long periods in off-design states. This requires a wide efficient operating range and the development of advanced design methods. To address the issues of low precision in load control design methods and narrow efficient operating ranges, this paper proposes a centrifugal pump impeller design method based on the three-segment quadratic function controlling blade load distribution. [Methods] The proposed method divides the blade load from the impeller inlet to the outlet into three segments: the inlet segment, the intermediate segment, and the outlet segment. Each segment is given a quadratic function-type load distribution to construct the impeller design method based on three-segment quadratic function load control. By assigning values to 13 independent control parameters, the specific form of load distribution is determined, resulting in the final structure of the impeller. Using this design method, a centrifugal pump with a specific speed of 102 is designed and numerically simulated to analyze its energy and flow-field characteristics. This study also establishes a comprehensive test bench for closed centrifugal pump hydraulic model testing, which consists of the test pump, pipeline system, and sensors that measure inlet pressure, outlet pressure, flow rate, rotational speed, and torque. The designed pump is manufactured and tested on this bench. [Results] The simulation results demonstrate that the optimized impeller achieves a 4.11% increase in efficiency at the designed point Qd and a 5.35% increase in the average efficiency under multiple operating conditions ranging from 0.7 Qd to 1.3 Qd, with an almost unchanged flow-head curve. The energy characteristics indicate that the optimized impeller has a wide efficient operating range. Internal flow-field analysis reveals a decrease in the area and strength of vortex and flow separation at off-design points. At the 50% span of the blades, the pressure distribution from the impeller inlet to the outlet is more uniform, and the streamline distribution is more reasonable. Furthermore, changing the blade load in the inlet section from a fast rise to a slow increase improves pressure distribution on the blade surface, reduces local pressure gradients, and achieves a uniform variation. The tested results show that the maximum efficiency of the designed pump is 78.20%, which meets the design requirements. Meanwhile, the simulated results are compared with experimental results. The error between the simulated and experimental results is lower than 5%, validating the accuracy of the simulation method. [Conclusions] Both simulated and experimental results confirm that the centrifugal pump impeller design method based on the three-segment quadratic function load control significantly enhances pump efficiency, improves flow patterns, and provides a reference for the development of high-efficiency and wide-operating-condition impellers.
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| Keywords
centrifugal pump
three-segment quartic
load control
impeller design
numerical simulations
experimental test
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Issue Date: 22 November 2024
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2024,
Vol. 64
