Study On Gas-solid Two-phase Flow Haracteristics Of Sepiolite Powder In Curved Pipe

Sepiolite powder is widely used in modern scientific fields such as air purification,aerospace,deep sea drilling and other non-metallic mineral materials.In order to obtain high purity sepiolite mineral powder,it is often classified and purified by pneumatic conveying device in the deep processing.The bend pipe is an important part in the pneumatic conveying device of sepiolite powder.Due to the influence of the bending structure,The gas-solid two-phase flow characteristic at the bend pipe are complex.The gas-solid two-phase flow characteristic of sepiolite powder in the bend pipe directly affects the subsequent purification and grading performance of the pneumatic conveying device.Numerical simulation and experimental study on the gas-solid two-phase flow characteristics of sepiolite powder in bend pipe,which based on the physical and mechanical properties of sepiolite powder particles.The research content of this dissertation mainly discusses the following aspects:(1)Detection of characteristics of sepiolite powder particles.The parameters such as kinematic viscosity,density and particle size of sepiolite powder were detected by powder comprehensive performance detector,ultra depth of field microscope,Stomer viscometer and strain type direct shear instrument,which supported for subsequent theoretical analysis and simulation.(2)Establishment of mathematical model for calculating gas-solid two-phase flow of sepiolite powder particles in bend pipe.Firstly,the basic hydrodynamic equations of particle and gas phases were established.Secondly,a Realizable k-?turbulence model and a Large eddy simulation(LES)were used to solve the equations of gas-phase fluid motion.Secondly,the force on sepiolite powder was analyzed.Finally,The gas-solid coupling governing equations of sepiolite particles in bend pipe were established,which based on the discrete phase model DPM.(3)Numerical simulation and analysis of gas-solid two-phase flow of sepiolite powder particles in bend pipe.The LES-DPM two-way coupling model was adopted to simulate the gas-solid two-phase flow characteristics of sepiolite powder particles in the pipe.The numerical simulation of gas-solid two-phase flow of sepiolite powder was analyzed by changing the different bending angles,bending diameter ratios,inlet speeds and particle sizes with COMSOL Multiphysics software.The main influencing parameters of gas-solid two-phase flow characteristics were analyzed by orthogonal experiment simulation,and the suitable conveying parameters were obtained under specific conditions(4)PIV experimental study on sepiolite particles in gas-solid two-phase flow in the bend pipe.The pneumatic conveying experiment of different bending angles,bending diameter ratios and inlet velocities of sepiolite powder particles was carried out by constructing the bend pipe pneumatic conveying experimental platform.The particle trajectories,pressure drops and velocities obtained were respectively compared with the simulation results.The above results show that the gas-solid two-phase coupling model established in this paper can effectively predict the gas-solid two-phase flow characteristics of sepiolite in the elbow,and the Large eddy simulation can clearly reflect the complex flow conditions in the elbow compared to the Realizable K-? turbulence model.It also provides a basis for the selection of appropriate parameters for the suspension pneumatic transport of sepiolite powder in the bend pipe under different structures and technological conditions,which is of great significance for the subsequent classification purification of sepiolite powder particles and the research on the mechanism of particle deposition and dispersion in the suspension transport of non-metallic mineral materials in the bent pipe.