Coupled effects of particle morphology and rotational speed on multiphase transport and erosion evolution in a multistage deep-sea mining pump

Deep-sea hydraulic lifting systems rely on multistage centrifugal pumps to transport coarse mineral particles under high-pressure, high-solids-loading conditions, where complex solid-liquid interactions strongly influence transport efficiency, hydraulic stability, and structural durability. However, the coupled effects of particle morphology and operating speed on particle transport, interphase momentum exchange, and wear evolution remain insufficiently understood. In this study, a two-way coupled Eulerian-Lagrangian CFD–DEM framework was developed and experimentally validated to investigate the internal solid-liquid flow behavior of a two-stage deep-sea mining pump. Three representative particle geometries, spherical, tetrahedral, and spherocylindrical, were examined under rotational speeds of 1450, 2000, and 3000 r/min at a constant solids mass fraction of 15%. The results reveal that rotational speed governs the overall energy transfer and transport intensity, while particle shape primarily controls transport stability and local collision mechanics. Increasing rotational speed significantly enhances particle translational velocity, drag force, pressure-gradient force, and lift force, resulting in stronger centrifugal segregation and tighter helical transport structures. At 3000 r/min, particle translational kinetic energy increased by nearly an order of magnitude compared with 1450 r/min, accompanied by substantially higher energy dissipation and contact-force fluctuations. Spherical particles exhibited the highest translational kinetic energy and normal contact force due to more efficient momentum transfer, whereas tetrahedral particles generated stronger tangential interactions and localized abrasive cutting. Wear analysis showed that blade leading edges and pressure-side surfaces were the most vulnerable regions, while shroud erosion shifted spatially between stages due to inherited swirl and secondary-flow redistribution. Non-spherical particles, particularly angular particles, intensified local stress concentration and accelerated material degradation. These findings provide new mechanistic insight into particle-shape-dependent transport and erosion in multistage mining pumps and offer practical guidance for hydraulic optimization and wear-resistant design in deep-sea slurry transport systems.