Numerical Simulation Of Flow Behavior Of Particles In A Screw Conveyer Based On CFD-DEM

The screw conveyor has the ability to transport and strengthen mixing,and it has been widely used and gradually developed into an essential equipment in industrial production.A large amount of cuttings will be produced in the process of onshore oil exploration or offshore drilling platform production.The cuttings will be brought to the ground with the drilling fluid.The cuttings will be separated by centrifuge and other equipment.The cuttings will be dried and then they will need to be transported and collected.The screw conveyor has been widely used in the transportation and collection of cuttings because their good airtightness,stable operation and high efficiency.In the past flow behavior of particles was simulated by means of discrete element method in a screw conveyor.But the influence of gas on particle flow was ignored.Therefore,in this paper CFD-DEM method combined with particle dynamics is used to simulate both the flow behavior of gas and particles in a screw conveyor,and the discrete particle motion is solved by Lagrange coordinates and the gas phase motion is solved by Euler coordinates.The DEM soft sphere model is used to fully consider the collision between particles and particles or particles and wall.The particle flow process in the screw conveyor is simulated,and the calculated results are compared with the experimental values to verify the accuracy of the model.Through the analysis and study of the factors affecting the particle flow,the results show that the particle mainly perform translational and rotational movements in the screw conveyor,and translational motion is a main mode of motion in a screw conveyor.With the speed of screw increasing,the pulsation and the movement of particles are more intense and the movement speed of particles increases faster,which are beneficial to the transportation of particles.With an increase of incline angle,the particles translational motion along the axial direction declines and the particle rotational motion increase,which has great influence on the flow behavior of particles.Increasing the filling rate will increase the particle density,inhibit the particle movement,and reduce the particle temperature and the contact force.With the increase of helix angle,the particle velocity of motion and the motion along the axis rise strongly.As the density of particle rises,the particles is more likely to accumulate and the smaller density of particles is more affected by the gas.Increasing the inlet speed of gas will accelerate the movement speed of particle,which is conducive to particle transportation.Numerical simulation of flow of particles with different particle shapes in the screw conveyor.The simulation results show that the particle shape is an important factor affectingthe transportation of the screw conveyor.The more the shape of particle deviates from the spherical shape(i.e.the lower the sphericity of the particles),the greater the rolling resistance.And the particles accumulate and deposit at the bottom more easily.Moreover,with the increase of sphericity,the movement of particles increases and the fluctuation is obvious.When spherical particles are transported,the interaction force between gas and particles is stronger.The higher the sphericity,the higher the contact force,collision force and total force.In this paper,the CFD-DEM model is used to simulate the flow behavior of particles in the screw conveyor and the impact of the different physical parameters and operating conditions are considered,which are more consistent the state of the gas-solid two-phase flow in the actual screw conveyor.The knowledge of these process characteristics provides a basis for improving the transport efficiency of the screw conveyor during the practical application.