Discrete Element Simulation And Experimental Study On Screw Conveyor Transporting Granular Materials

Screw conveyors should be widely used in short-distance lifting or horizontal transport of loose materials such as powders or granules in various backgrounds,such as forestry,agriculture,industry,construction,machinery manufacturing,and ports.It is considered as a green,convenient and efficient transport device.It is unique structure can make spiral feeding quantitative or quantitative discharging in the conveying process.The main research contents and conclusions of this article are as follows:1.In this paper,we studied the particles conveying process with the large screw conveyors and improved screw conveyors of U-shape cross-section tube by the experiment,and we found that the mass flow rates increased with the increase of rotation rate,and decreased with the increase of inclination angle.The mass flow rate of the large screw pitch was larger than small screw pitch;mass flow rate of big particle was larger than small particle.2.Secondly,The discrete element method simulates the dynamic process of the particle conveyed by the screw conveyer of the same experiments size,and compares it with the experiments.The good agreement of simulations and experiments guaranteed the correct of DEM model and parameters used.Based on the validated DEM model and parameters,we then compared the efficiency,compressive force between round tube and U-shape tube conveyors.The comparison shows that the efficiency of the U-shape tube is higher than round tube at a small angle,but the efficiency of the round tube exceeds the U-shape tube under the inclination angle larger than 60°.Besides,we found that the relationship between transport efficiency and rotational speed was no-linear,which would remain stable after rotational speed exceeded an upper limit value.For compressive force of particles,particles at the feed hopper have larger compressive forces than those at other places,and the round tube is larger than the U-shape tube at feed hopper;with the increase of rotational speed particles compressive force tends to be stable.3.Finally,this paper establishes the model of the twin-shaft conveyor and performs the DEM simulation analysis,it was found that the steering of the twin-screw have no effect on the mass flow;Comparing the mass flow rate per unit cross-sectional area(M/A)for single-screw and twin-screw conveyors with the same pitch and speed,it was found that the maximum values of single-axis and double-axis M/A were close to each other.The twin-screw pitch and center distance will have a significant effect on M/A.At the same time,the regression equations of center distance,pitch and mass flow rate R2=0.9646 are obtained by simulation data fitting.