Research On The Migration Of A Solid-liquid Two-phase Medium And Energy Features In A Centrifugal Pump For Transporting Coarse Particles

The mineral resources under the sea are rich in types,high reserves and high quality,and the development prospect is huge.The pump–pipe lifting system is the most promising deep–sea mining technology,which is widely accepted in the world.The slurry transport pump is the key power equipment of the system.The problems of flow instability and blockage occur easily in the process of slurry transportation.The problems can induce a steep drop in pump performance,which directly affect the safe and reliable operation of the mining system.The slurry transport pump is a multistage centrifugal pump with bowl diffuser,and its flow channel is complex.The ore particles have the characteristics of high density and large particle size.The study of solid–liquid two–phase flow composed of ore and fluid is the basic guarantee for the design of efficient and reliable slurry transport pump.There are three important engineering problems about designing and manufacturing slurry transport pumps: 1.The passing performance of mineral particles(channel blockage);2.Reliability(wall wear);3.Efficiency(energy consumption).The three problems are closely related to the migration of particles in the pump.In this paper,the 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).The performance curve of the pump is obtained by experimental measurement under the conditions of clean water and ore slurry.The numerical results are in good agreement with the experimental results within the allowable error range,and the reliability of the calculated results is verified.Due to the application of the amplification flow rate design method,the efficiency point is separated from the working point.Because of the amplify flow design method,the optimal efficiency point is separated from the actual working point,and tends to the condition of large flow.For the slurry transport pump,firstly,this paper analyzes the influence of leakage flow on the main stream,the relationship between leakage volume and flow rate,and the two–stage difference of leakage flow.Then the flow characteristics of the impeller and the bowl diffuser are studied.Then the error between the total pressure drops method(experimental results)and the entropy production–volume loss method is analyzed,and the feasibility of using entropy production to calculate hydraulic loss is verified.The difference of hydraulic loss between the two stages is studied by entropy production loss and volume loss,and the distribution of entropy production rate in the main hydraulic components is analyzed.Finally,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 migration of particles in the bowl diffuser is divided into three periods.In the first period,the particles get into the bowl diffuser,and the circumferential velocity component is much larger than the other velocity components.In the second period,the particles move up along the suction of the bowl diffuser.The particles experience many collisions on the suction surface of the bowl diffuser and their motion trajectory is a broken line.These collisions gradually convert the circumferential velocity of the particles to the axial velocity,and also cause the particles to lose some kinetic energy.In the third period,the particles leave the bowl diffuser and the axial movement is dominant.These works can provide a reference for the study of wear and blockage prevention of slurry transport pumps.