Erosion in centrifugal pumps for transporting flows with dilute particles is a main pump failure problem in many engineering processes. A numerical model combining the computational fluid dynamics (CFD) and Discrete Element Method (DEM) is applied to simulate erosion in a centrifugal pump. Different models of the liquid-solid inter-phase forces are implemented, and the particle-turbulence interaction is also defined. The inertial particles considered in this work are monodisperse and have finite size. The numerical results are validated by comparing the results with a series of experimental data. Then, the effects of particle volume fraction, size, and shape on the pump erosion are estimated in the simulations. The results demonstrate that severe erosive areas are located near the inlet and outlet of the pressure side of the impeller blade, the middle region of the blade, the corners of the shroud and hub of the impeller adjoining to the pressure side of the blade, and the volute near the pump tongue. Among these locations, the maximum erosion occurs near the inlet of the pressure side of the blade. Erosion mitigation occurs under the situation where more particles accumulate in the near-wall region of the eroded surface, forming a buffering layer. The relationship between the particle size and the erosion is nonlinear, and the 1 mm particle causes the maximum pump erosion. The sharp particles cause more severe erosion in the pump because both the frequency of particle-wall collisions and the impact angle increase with the increasing sharpness of the particle.

In order to improve the hydraulic efficiency and internal flow pattern of a multi-stage pump under multiple flow conditions, an intelligent optimization design was proposed for its hydraulic components. Sensitivity analysis was used to select the key parameters influencing the hydraulic efficiency of a multi-stage pump. The optimal Latin hypercube sampling and non-dominated sorting genetic algorithm Ⅱ were employed to build a multi-objective optimization system. Moreover, a radial basis function neural network was adopted as the surrogate model of hydraulic efficiency. The research results showed that the impeller outlet width, impeller blade wrap angle, impeller outlet blade angle, and diffuser inlet width were the key factors affecting the hydraulic efficiency. The efficiency of the optimized model increased by 4.35% under the design condition and the matching of the internal flow between the optimized impeller and diffuser was significantly enhanced under the nominal condition. The improved flow pattern could be clearly observed in the flow passage of both the pump impeller and the diffuser. After optimization, the wear performance of the model was also improved compared to the original design. The wear area decreased in size and was distributed more evenly, resulting in a noticeable decrease in the maximum amount of wear.

A numerical model of annular linear induction pump with a full-scale pump channel is created to study the scale-dependent instability of the magnetohydrodynamic flow. The magnetic-fluid coupling effect is implemented by modifying the underlying governing equations and constraints. The model authenticity is validated by comparing the simulated pressure difference, as well as the pressure pulsation, with the previous experimental data. The flow patterns at different flow rates corresponding to different magnetic Reynolds numbers are depicted from both the azimuthal and meridian viewpoints, and the periodicity of the occurring vortex flows is found in the pump. By analyzing the different mechanisms contributing to the fluid kinetic energy, it is found the competition between the axial components of the Lorentz force and pressure gradient dominates the flow evolution in the pump channel. The magnetic-fluid coupling effect is found to amplify the disturbances in either the magnetic field or the fluid field. It is even effective within the uniform externally imposed magnetic field and inlet velocity only if a disturbance exists in the initial flow. Increase in the cycle number of disturbance can enhance the flow stability and induce smaller vortex flows. Finally, different mechanisms of energy conversion in the pump are analyzed and it is found that the sudden occurrence of vortex flows can induce large current density, which significantly increases the Ohmic dissipation and decreases the efficiency of energy conversion from magnetic field into the fluid. The relatively large Ohmic dissipation in the fluid is the main reason for the low efficiency of such a device.