Numerical Simulation And Experimental Study On Gas-solid Two-Phase Flow In Vertical Screw Conveyor

Until today,the bulk material loading technology has been already developed to a certain high level,but the ship unloading technology is more difficult than the loading technology,and the highest efficiency is only about 1/4 of the loading efficiency.Vertical screw conveyor has been widely used in the bulk material conveying domain due to its unique advantage.At present,domestic and foreign scholars mainly use the discrete element method to analyze the flow field in vertical screw conveyor.But because of the limitation of the discrete element method,it is difficult to analyze the movements of large number and small size of particles.Based on computational fluid dynamics theory and the Euler two fluid model,the gas-solid flow in the vertical screw conveyor is studied in this paper,the main work and results are as follows:(1)Applying the theory of discrete mechanics,the stress distribution of the particles in vertical screw conveyor is analyzed,and based on the analysis of material motion,the motion parameters of materials are established.By using the hypothesis of change on speed of material particles spiral groove along the radial,the equation of the motion is obtained.(2)This paper uses Fluent to simulate the dilute gas-solid flow of mono-sized particles in the vertical screw conveyor,and the Euler two fluid model is been used to analyze the flow properties of particles in vertical screw conveyor.The study suggests that,the axial velocity of particles was influenced by the inlet and outlet,the total speed of the particles was higher at the tube wall,but because of the gap between the screw blade and the tube wall,the axial velocity was lower at the tube wall,and the maximum value appears only in the outer edge of the blade.The granular temperature on the blade increases gradually from the center to the edge in radial direction,and was higher near the tube wall than that in the flow channel,and it can represent the wear conditions of the blade.(3)In order to explore the transport law under different speed of the screw,this paper makes a further research of the flow properties of particles in vertical screw conveyor under the different rotational speeds of the screw based on the results before.The study shows that,the axial velocity of particles increases with the increasing of the rotational speed,but it becomes more and more unstable,and the particle distribution becomes uniform gradually,but the particle filling ratio,axial force total torque and the power of screw decreases with the increasing of the rotational speed.(4)Considering the research conditions,a set of vertical screw conveyor experiment device is built.The parameters of experiment set test were determined,then a system to obtain them was built up,and the factors which affecting the performance of vertical screw conveyor were tested.The experimental result is then compared with that from the simulation results.It is found that,the particle filling ratio increases with the increasing of the feed rate and the amplification increased first and then decreased.The torque of the screw shaft increases with the increase of the feed rate,and the amplification is gradually increased.The whole axial velocity of the material increases with the increase of the screw rotational speed,and the simulation results are is consistent with the simulation results.But the particle filling rate of the experimental results shows great fluctuation,and the reasons of the errors are analyzed.