Axial thrust in centrifugal pumps attracts extensive attention in order to improve the operating reliability of pumps. High axial thrust can cause rapid thrust bearing wear and subsequent pump failure or frequent overhauls. A centrifugal pump (XA65/20) was selected in this study, based on L16 (43) orthogonal array and CFD methods. The time-averaged Navier-Stokes equation was calculated for a 3D steady flow in the model pump in ANSYS CFX with the standard k-ω turbulence model and standard wall function applied. The structured meshes with different numbers were used for comparison in order to confirm that the computational results were not influenced by the mesh. Meanwhile, the effects of impeller back pump-out vane geometrical parameters, including its thickness Sk, its outlet diameter De and axial clearance δ, on the axial thrust and performances of the model centrifugal pump were analyzed. The different orthogonal schemes were obtained on the different values of Sk, De, and δ.
Finally, when the parameters of the impeller Sk, De, and δ are 5mm, 100mm, 1.5mm, respectively. The Best Efficiency Point (BEF) of 69.9% was achieved with 60.12m for the designed head and −952.133N for the minimum total axial force. The corresponding impeller with minimum total axial force was considered as the optimal scheme and manufactured for experimental test. The external characteristics by CFD have a good agreement with their experimental data, which also better verified the accuracy of the numerical method of axial thrust applied in this research.