Influences of the diameter of the balance hole on the flow characteristics in the hub cavity of the centrifugal pump

The diameter of the impeller balance hole in a centrifugal pump is closely related to axial force. Thus, to select the appropriate diameter of a balance hole is crucial for balancing the axial force of the centrifugal pump. After the validation of the CFD method and the grids independence study, the characteristics of flow in the hub cavity have been analyzed in 4 cases with different diameters of balance holes. The leakage rate of the liquid in the hub cavity of the centrifugal pump is calculated and compared with the test result. According to the research, when no balance hole exists, the distribution of liquid velocity in the core area of the hub cavity exhibits axial symmetry, and the circumferential velocity component is approximately 0.4 times of the impeller’s rotational speed. When the balance hole exists, the distribution of liquid velocity in the hub cavity does not exhibit axial symmetry, and the circumferential velocity component is larger than 0.4 times of the impeller’s rotational speed. The radial leakage velocity on the turbulent boundary layer of the pump cover will increase with the increasing diameter of the balance hole.