On the axial thrust and hydraulic performance of a multistage lifting pump for deep-sea mining

The multistage centrifugal lifting pumps are widely used for deep-sea mining to achieve high-head vertical transportation. However, the axial thrust caused by the multistage structure probably exceeds the carrying capacity of the deep-sea lifting pump. Mounting balance holes on the impeller reduces the axial thrust but also affects the pump's hydraulic performance. In this research, the deep-sea mining pump's axial thrust and hydraulic performance were studied. A computational fluid dynamics model of a two-stage centrifugal pump was established employing the whole-flow-field method. Numerical simulations on the transportation of pure liquid and solid-liquid mixtures were then carried out for an actual mining pump. Results reveal that the influence of balance hole position on hydraulic performance or thrust is insignificant. A larger hole diameter, contributing to an increased flow rate and ability to balance axial thrust, however, causes more flow losses and worse hydraulic performance. Furthermore, a test prototype pump was developed, and a non-destructive measuring device was exploited to acquire hydraulic parameters and axial thrust. The experimental results reveal the effectiveness of the proposed balancing scheme and numerical method. These findings could provide analytical methods and theoretical support for designing lifting pumps in deep-sea mining.