Investigation of tip leakage vortex characteristics in a centrifugal pump

Tip leakage vortex in a semi-open centrifugal pump has adverse effect on the external performance and vibration. In order to improve the understanding of tip leakage vortex structure and trajectory, a semi-open centrifugal pump was simulated by ANSYS CFX software and SST k-ω turbulence model. Then, the characteristics of the tip leakage vortex and distribution of tip leakage flow were analyzed, the prediction model of the tip leakage vortex trajectory was improved. The results show that the external characteristic of the numerical simulation is consistent with the experiment data. The minimum of the chordwise component of the tip leakage flow relative velocity coincides with the initial position of tip leakage vortex, and it moves upstream with the decrease of flow rate. The negative chordwise component leads to the formation of reverse vortex, and the increase of normal component is the main reason for leading edge overflow at small flow rate and secondary tip leakage flow nearing the trailing edge at the large flow rate. The tip leakage flow with a large velocity gradient at the tip clearance leads to the high entropy production rate. The mixing and rolling up phenomenon between the tip leakage flow and main flow also results in high entropy production rate. The area of the high entropy production rate increases with the flow rate decrease. The improved trajectory prediction model replaces the average velocity of the impeller inlet with the average velocity of the blade tip clearance inlet. The errors between the predicted results and the numerical simulation re- sults are negligible, indicating that the improved model could well predict the migration trajectory and expand the prediction range. © 2020, China Water Power Press. All right reserved.