Research On Particle Collision And Erosion Mechanism In The Channel Of Impeller

Solid-liquid two-phase centrifugal pump is widely used in food industry,ore transportation industry,chemical industry,metallurgical industry and dredging industry for its simple structure,convenience,environmental protection,high efficiency and excellent transmission capability.However,erosive wear appears at wet end components of centrifugal pump,especially at the impeller region,due to the hydraulic transport of solids.Erosion may cause Low efficiency,short service life and even safety accidents.In this paper,the CFD software and DEM software are used to coupling to calculate the erosion of impeller passage,which is simplified to a bend.At first,we verify the feasibility of the CFD-DEM coupling calculation of solid-liquid two-phase by comparing the wear experiments with numerical simulation.And then,a simulation scheme is designed,which is mean to investigated how the size,concentration,density,velocity of the particles and radius of curvature influence wear,based on the orthogonal experiment.Last but not the least,we use the control variable method to analyze the relationship between particle shape,size combination and wall wear.The main contents of the dissertation are as follows:(1)The impeller passage is simplified to a bend,of which we study the wear of the inner wall.The wear test of the elbow at different concentrations was carried out,and the solid-liquid two-phase numerical simulation was calculated based on the FLUENT-EDEM coupling.The experimental data are consistent with simulation results at severe wear areas,wear rate at different mass concentrations and surface topography,which verifies the accuracy of FLUENT-EDEM coupling calculation of solid-liquid two-phase wear.(2)The numerical simulation of the 120°elbow was carried out based on CFD-DEM coupling.We study the effects of fluid's velocity,radius of curvature and particle concentration on the two-phase flow.To analyze the whole motion process of the particles in the bend,it is found that velocity of fluid and radius of curvature have much bigger influence on the two-phase flow than the particle concentration.(3)Based on the orthogonal experimental design simulation scheme,the effects of particle size,p mass concentration,density,velocity of fluid and radius of curvature on wall wear were studied.The results show that the impact of particle density is minimal when we use the average wall wear index,and the influence of concentration is minimal when we use the maximum wall wear index.While the velocity of fluid affect most with both indicators.(4)The simulation scheme was designed to analyze the effect of particle shape and different size combinations on wear using the control variable method.It is found that with the increase of sphericity,the wall wear rate shows an "S" curve distribution.As the relative volume fraction of small particles increases,the average wear of the wall surface decreases.