Numerical simulation and test on impeller wear of slurry pump

Abstract: The centrifugal slurry pump is a device that is used to deliver high density fluid containing suspended solid. It is generally used in electricity, mining, metallurgy, transportation, water conservancy and environmental protection industry. In order to study wear characteristics of impellers during slurry pump working, a centrifugal engineering plastic slurry pump was chosen as the main study model. The entire solid-liquid two-phase flow field in the model pump, which includes inlet, impeller, volute, back blade passage, and gap was meshed by structured girds with ICEM CFD software. Firstly, single-phase flow fields under five working conditions, including the design working condition, were simulated with the SST k-ω turbulence model, and the simulative external characteristic curves were compared with test results. It was found that the maximum error is less than 5%, and the error at the design working condition is less than 3%. It showed that the results of simulation are reliable. Based on the results achieved, mentioned above, particle multiphase model in ANSYS CFX software was adopted to simulate the solid-liquid two-phase flow in the model pump. To verify the results of simulation, a wear test rig was set up to study the abrasion of impellers during the operation of pumps. The results of simulation and test showed that: the distribution of volume fraction of solid-phase has a good agreement with the wear pattern of hydraulic components in impellers during the wear test, and the two-phase flow field achieved by simulation can be used to explain the generation of abrasion. The areas with relatively more severe abrasion in impeller passages are located at the inlet edge of blades, the surface of the back shroud near the inlet edge and pressure side, as well as the junction between the pressure side and back shroud which does not extend to the outlet edge, because the existence of low speed circulation at the inlet edge of blades can easily lead to the gathering of solid particles which will aggravate the abrasion of inlet edge. Additionally, the particles that flow into the passages have an axial speed, which make them move towards the back shroud, finally causing the impact, and the flow separation of particles occurs at the pressure side of blade near the outlet edge. The most severe abrasion are in the back blade passages located at the pressure side near the outlet edge of the impeller, and the abrasion pattern develops towards the hub, which leads to a parabolic wear shape. The abrasion at the other areas in the back blade passages can be neglected. The main reason obtained from the analysis which mainly causes the abrasion of back blades was the impact between the particles and the back blades induced by the back flow under the effect of high pressure at the volute tongue. Through the comparison of numerical and test results, the simulation method was proved to be viable in predicting the wear characteristics of impellers during the operation of pump, and the two-phase flow field achieved from simulation can provide some direction and reference information for optimization design.