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Analyses of gasliquid twophase flow and pressure fluctuation during startup of municipal waterlogging selfpriming pump |
National Research Center of Pumps, Jiangsu University, Zhenjiang, Jiangsu 212013, China |
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Abstract To explore the selfpriming mechanism of selfpriming pump, the external mixing selfpriming pump was taken as the research object. Combining with grid slip technology, the unsteady numerical simulation of the selfpriming process was carried out by the VOF twophase flow model and kε turbulence model in CFX simulation software. The distributions of gasliquid twophase volume, liquid phase velocity, outlet void fraction and pressure in the pump at different times were analyzed. The time step and the total time of unsteady state simulation were changed to monitor the pressure change in the impeller and volute during the selfpriming process. The results show that the suction and exhaust of the selfpriming pump are mainly concentrated in the early and middle stages of the startup process, and the air contents in the impeller inlet and pump outlet are more than 60% and 75%, respectively. The gasliquid mixing zone at the impeller outlet leads to the flow disorder phenomenon in the large area from the impeller outlet to the inner side of the volute, which reduces the work capacity of the impeller and affects the normal exhaust of the pump. The pressure fluctuation amplitude of the monitoring point of the impeller is related to the distance from the blade working face, while the pressure fluctuation amplitude of the monitoring point in the volute is related to the distance from the outer edge of the impeller.
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