Dynamic behavior of irregular particles and transition mechanism of erosive wear in a helical mixed-flow deep-sea mining pump

Non-uniform particle shape characteristics can intensify wall erosion in deep-sea mining pumps, yet the underlying mechanisms remain unclear. In this study, a CFD-DEM method based on the reconstruction of realistic particle morphology was employed to numerically investigate a helical mixed-flow deep-sea mining pump, with particular focus on the effects of particle size and sphericity. The validity of the numerical model was established through bench performance tests and tracer particle trajectory observations. The particle physical properties were subsequently refined and incorporated into the numerical simulations. By combining the sphericity-corrected Stokes number under high-Reynolds-number conditions with the simulated particle motion dynamics, a particle size of 10 mm was identified as the critical threshold for the wear mechanism transition. Further analysis of sphericity at this critical size showed that, when the sphericity decreases from 0.95 to 0.85, the number of particle tumbling events in the impeller decreases by 54.1%, and the impeller erosion rate decreases by approximately 60%. In the guide vanes, however, particle angularity intensified localized wear through geometric interlocking and stress concentration. These results clarify the coupled effects of particle size and morphology on the transition of erosion mechanisms, providing mechanistic guidance for component-specific anti-wear design of deep-sea mining pumps.