| The exploitation of deep-sea mineral resources is an important development direction in "Marine-Power" strategy.The vertical lifting pipeline is an important part of the deep-sea mining hydraulic lifting system.Studying and mastering the movement state and lifting characteristics of coarse particles in the pipeline is of great significance to improve the safety and efficiency of hydraulic lifting.Based on this,this paper established the CFD-DEM coupling model of hydraulic lifting of coarse particle vertical pipeline by the numerical simulation method,and explored the flow characteristics,distribution characteristics,interaction law,pipeline energy and pressure loss law of two-phase flow in pipe under different working conditions,so as to provide theoretical reference for engineering practice.The main contents are as follows:(1)CFD-DEM method was used to establish a numerical model of hydraulic lift of coarse-particle vertical pipeline.Computational fluid dynamics method and discrete element method were used to solve and calculate the flow field characteristics and the motion and collision characteristics of solid particles respectively.The interaction between the two phases was realized through the interaction of momentum and energy.The accuracy of the model is verified by comparing the simulation data with the experimental data.(2)The model is used to simulate the hydraulic lifting process of coarse particles in static pipelines,and the macroscopic motion characteristics such as particle velocity and concentration distribution are obtained.Then: 1)The variation law of particle concentration and velocity under different transportation conditions,as well as the distribution characteristics along radial direction and lifting direction are analyzed;2)From the perspective of force,the change rule of interaction force between particle and fluid,particle and particle,and particle and wall under different transport conditions is analyzed,and the influence mechanism of particle force on macroscopic motion characteristics is explored;3)Summarize the influence of conveying parameters such as particle size,conveying velocity,feeding concentration and gradation on lifting characteristics.(3)Further,by modifying the interaction strategy of interphase data,the pipeline vibration is synchronized in CFD and DEM,and the lifting characteristics of particles under different vibration frequencies and vibration amplitude are obtained,and the influence law of vibration intensity changes on lifting characteristics is summarized.The results show that the vibration of pipe makes the dynamic characteristics of particles fluctuate,which leads to the increase of local concentration of particles and pressure loss of pipe,and adversely affects the particle lifting.(4)Comprehensively considering the indexes of particle mass flow,energy and pipeline pressure loss,the influence of the change of transport parameters on particle lifting efficiency is analyzed.Based on this,the range of transportation parameters that can maximize the improvement efficiency is explored,and a reasonable parameter formulation strategy is proposed. |
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