The flow with solid-liquid two-phase media inside centrifugal pumps is very complicated and the relevant method for the hydraulic design is still immature so far. There exist two main problems in the operation of the two-phase flow pumps, i.e., low overall efficiency and severe abrasion. In this study, the three-dimensional, steady, incompressible, and turbulent solid-liquid two-phase flows in a low-specific-speed centrifugal pump are numerically simulated and analyzed by using a computational fluid dynamics (CFD) code based on the mixture model of the two-phase flow and the RNG k-ɛ two-equation turbulence model, in which the influences of rotation and curvature are fully taken into account. The coupling between impeller and volute is implemented by means of the frozen rotor method. The simulation results predicted indicate that the solid phase properties in two-phase flow, especially the concentration, the particle diameter and the density, have strong effects on the hydraulic performance of the pump. Both the pump head and the efficiency are reduced with increasing particle diameter or concentration. However, the effect of particle density on the performance is relatively minor. An obvious jet-wake flow structure is presented near the volute tongue and becomes more remarkable with increasing solid phase concentration. The suction side of the blade is subject to much more severe abrasion than the pressure side. The obtained results preliminarily reveal the characteristics of solid-liquid two-phase flow in the centrifugal pump, and are helpful for improvement and empirical correction in the hydraulic design of centrifugal pumps.

The slurry transport pump is the key equipment of deep-ocean mining systems. The motion law of coarse particles in the pump is not clear enough. In this paper, a hydraulic model of a laboratory-scale two-stage slurry transport pump is constructed, and the motion characteristics of coarse particles in the pump are numerically studied by using the computational fluid dynamics–discrete element method (CFD-DEM) method. The performance curve of the pump is obtained by experimental measurement, and the reliability of the calculated results is verified. Due to the application of the amplification flow rate design method, the optimum efficiency point of the pump is shifted to the large flow rate condition. Differences in particle swarm within two stages are compared. The position distribution, velocity variation and trajectory of particles in the impeller and bowl diffuser are studied in detail. The velocity of particles leaving the impeller depends on whether they collide with the impeller blade. The motion of particles in the bowl diffuser is divided into three periods. Collision between particles and blades in the bowl diffuser not only leads to energy loss but also gradually transforms the circumferential velocity of particles into axial velocity in the second period. This work can provide a reference for the study of wear and blockage prevention of slurry transport pumps.

In the conveying process of a solid–liquid two-phase medium, the wear of the flow passage components is unavoidable. In this study, the solid–liquid two-phase flow in a centrifugal pump was numerically simulated by computational fluid dynamics–discrete element method coupling. For particle diameters up to 3 mm, the particle–particle and particle–wall interactions were considered in the simulation. Two-phase performance and wear experiments for different flow rates and particle concentrations were conducted. The wear experiment was carried out for 48 h at each mass concentration. In these experiments, a paint film method was used to display the wear position, and the wall thickness of the flow passage was measured using an ultrasonic thickness gauge. The results show that the instantaneous wear rate of the impeller, volute, and wear plate in the pump changed periodically with the impeller rotation. The volute wall wear was related to the particle movement. With the increase in the particle mass concentration, the wear rate increased. However, the rate of increase of the wear rate decreased because the particles moved to the wall in the volute to form a particle layer. Increasing the concentration did not linearly increase the effect of the particles on the wall.

The transient behavior of centrifugal pumps during transient operating periods, such as startup and stopping, has drawn more and more attention recently because of urgent needs in engineering. Up to now, almost all the existing studies on this behavior are limited to using water as working fluid. The study on the transient behavior related to solid-liquid two-phase flow has not been seen yet. In order to explore the transient characteristics of a high specific-speed centrifugal pump during startup period delivering the pure water and solid-liquid two-phase flow, the transient flows inside the pump are numerically simulated using the dynamic mesh method. The variable rotational speed and flow rate with time obtained from experiment are best fitted as the function of time, and are written into computational fluid dynamics (CFD) code-FLUENT by using a user defined function. The predicted heads are compared with experimental results when pumping pure water. The results show that the difference in the transient performance during startup period is very obvious between water and solid-liquid two-phase flow during the later stage of startup process. Moreover, the time for the solid-liquid two-phase flow to achieve a stable condition is longer than that for water. The solid-liquid two-phase flow results in a higher impeller shaft power, a larger dynamic reaction force, a more violent fluctuation in pressure and a reduced stable pressure rise comparing with water. The research may be useful to understanding on the transient behavior of a centrifugal pump under a solid-liquid two-phase flow during startup period.

Fine and large particles flowing through a bend in a pipe move differently and therefore erode the pipe differently. This paper simulates solid–liquid two-phase flow containing large particles in a bend and analyses the relationship between the wear formation and particle motion. Wear experiments are carried out using 3-mm glass bead particles at a mass concentration of 1–15%. At the same time, the flow field and the motion of the granular system are obtained in computational fluid dynamics–discrete element method simulation. The wear formation mechanism is revealed by comparing experiments with numerical simulations. The wear rate of the wall surface increases with the mass concentration, while the marginal growth rate decreases as the mass concentration increases. As the mass concentration increases to a certain value, the degree of wear reaches a maximum and remains unchanged subsequently because of the formation of a particle barrier along the bend wall. The particles near the wall region will bounce forward because of the periodic disturbance flow around particles. The impact of mass bouncing particles causes the formation of the erosion ripple on the test sheet.