Numerical Research On Coarse Particles Solid-liquid Two-phase Flow In A Multistage Mixed-flow Lifting Pump

With the development of economic production,the demand of society for resources has been increasing since the beginning of the 21st century.The mineral reserves on the land have not been able to meet the needs of human beings,and all countries have gradually entered the ocean in terms of resource utilization.The oceans that cover 71%of the earth's surface are rich in mineral resources,such as polymetallic nodules,cobalt-rich crusts,and polymetallic sulfides.Therefore,it is of great significance to relieve the supply pressure of mineral resources and increase the degree of strategic resource security in China that strengthening the exploitation of deep-sea mineral resources.In this paper,the solid-liquid two-phase flow of coarse particles in a deep-sea mining lifting pump is studied by combining theoretical analysis and numerical simulation,and the in-flow characteristics,wear characteristics and particle movement characteristics of the solid-liquid two-phase flow of coarse particles in the pump are analyzed under different flow rates,concentrations and particle sizes.The main work and conclusions of this paper are as follows:1.The development status of deep-sea mining technology in the domestic and overseas and the research status of solid-liquid two-phase flow pump test and numerical calculation are summarized.2.The velocity coefficient method is used to design the impeller and space guide vane of lifting pump,and the transparent impeller and space guide vane are manufactured by using PMMA.The visualization test system of solid-liquid two-phase flow of lifting pump is built and the energy performance test of lifting pump is carried out.The test results show that the head is 20.2m and the efficiency is 64.88%under the design condition.The optimal working condition point is 1.4Q_d,and the efficiency is68.03%.3.Discrete Phase Model(DPM)is used to simulate the solid-liquid two-phase flow in the lifting pump under different flow rates,the relationship between solid phase volume distribution and liquid phase flow was analyzed.,the results show that:(1)the distribution uniformity of solid phase in the first stage impeller is better than that in the second stage impeller.With the increase of flow rate,the distribution of solid phase volume in two stage impellers tends to the suction surface of the blade,the particle volume fraction at the outlet of the pressure surface gradually decreases,and the scale of flow vortex decreases;(2)with the increase of concentration,the solid phase distribution at the inlet of pressure surface gradually decreases,and the scale of the flow vortex gradually increases;(3)with the increase of particle size,the solid phase in the two stage impellers tends to be on the suction side of the blade.The volume fraction of solid phase in the guide blade inlet gradually increases,and the scale of flow vortex gradually decreases.The uniformity of solid phase distribution in the impeller was improved.4.The Oka model based on fluid dynamics is used to simulate the wear characteristics of each flow components of lifting pump,the wear distribution law and wear rate of each part in the pump are analyzed,and the results show that:(1)with the increase of flow,the wear area at the inlet of the two stage impeller and guide blade gradually increased,while the outlet gradually decreased,and the average wear rate of the front cover plate gradually decreased,with a maximum decrease of 33.8%;The average wear rate of the two-stage impeller blade,hub and guide blade all showed an increasing trend,with the maximum increase of 39.8%,173.9%and 61.49%respectively.(2)with the increase of concentration,the wear area of the two-stage impeller and guide blade gradually increased,and the average wear rate showed an increasing trend,with the maximum increases of 96.1%,89.1%,114.1%and 76.84%,respectively.(3)with the increase of particle size,the wear area at the inlet and outlet of the two-stage impeller gradually increased,and the average wear rate showed an increasing trend.The maximum increases were 182.8%,158.8%and 86.34%respectively.The wear at the entrance of the two-stage guide blade gradually increased,while the wear at the exit gradually decreased.The average wear rate showed a trend of decreasing,with a maximum decrease of 82.11%.5.CFD-DEM coupling method is used to perform transient simulation calculation of particle movement characteristics in the lifting pump under different physical parameters.The particle movement,particle velocity distribution and particle collision characteristics in the pump are analyzed.The results show that:(1)with the increase of particle size,the collision probability at the inlet of the impeller gradually increased,and the particle backflow was obvious.The particles in the impeller passage gradually shift from the pressure to the suction surface.(2)with the increase of particle size,the overall movement speed of the particle in the lifting pump tends to decrease;The distribution interval of particle velocity gradually widens.(3)with the increase of particle size,the particle collision changes from the collision between particles to the collision between particles and the wall surface.