Objectives  When research is conducted for the centrifugal pumps' structural design and performance, the influence of the seal ring clearance is often neglected. However, the clearance of the seal ring will not only change the external characteristics of the centrifugal pump, but also affect its flow field distribution.

  Methods  In this paper, a vertical centrifugal pump with medium-specific speed is used as the research object. The ANSYS CFX is used to simulate and analyze the influence of different wear-ring clearances(0, 0.5, 0.7, 1.06 mm)on the external characteristics, pressure distribution, and velocity distribution of the centrifugal pump.

  Results  The results show that the external characteristics of the centrifugal pump with different annulus clearances are consistent with the experimental data. The relative error of two is less than 5%(except 1.06 mm clearance). This verifies the reliability of the numerical simulation. With the increase of the clearance of the seal ring, the head of the centrifugal pump decreases by 20% and the efficiency by 15% under design conditions. The local pressure of the front and back cover plates of the impeller at the small clearance increases, and the overall pressure at the large clearance decreases, resulting in the radial pressure distribution of the impeller cover plate being asymmetric. The gap of the annulus leads to turbulence in the fluid and the pressure and velocity at the inlet and outlet of the centrifugal pump present an uneven gradient distribution.

  Conclusions  The research results can provide a reference for the structural design and flow field analysis of the centrifugal pump.