Performance Research And Optimization Of Double Screw Conveyors Based On Discrete Element Method

Double screw conveyors are a kind of conveying equipments which are widely used in various industries.However,due to the lack of researches on double screw conveyors at home and abroad,it is hard for people to chose suitable working conditions and structures of them when they transport cohesive materials.Moreover,the design of double screw conveyors is often based on human experiences which always causes a series of problems,such as low conveying capacity,high power consumption and low life.What’s more,the optimization of the structures of double screw conveyors is always based on the principle:when they are damage,then the optimization will begin,which leads to low efficiency and economic performance.To deal with the problems above,the double screw conveyers with different structures are modeled according to a real double screw conveyer,and simulated by discrete element method in order to provide reference for the selection of working condition parameters and the selection and optimization of structures of the double screw conveyors.And the following four tasks have been completed:1.When the double screw conveyor transports different viscosity materials,the distribution of particle axial velocity,angular velocity,forces around the shell and forces around screw blades is obtained under different screw speed,filling ratio.Through the analysis of these parameters,it is shown that the conveying capacity of the double screw conveyor can be improved by increasing the screw speed or filling ratio appropriately,but these two parameters should not be too large to prevent the performance of the conveyor from getting worse.2.The double screw conveyers with different structures are represented by a dimensionless parameter called overlapping ratio.Through the simulation of the double screw conveyers with different structures,the distribution of particle axial velocity,angular velocity,forces around the shell and forces around screw blades is obtained.Through the analysis of these parameters,it is shown that when the double screw conveyor is designed to transport non-cohesive material mainly,the structure of no overlap between two screw blades should be adopted;When the double screw conveyor is designed to transport cohesive material mainly,the structure of a certain overlap between two screw blades should be adopted.3.The distribution of forces around the shell and forces around screw blades is analyzed under different screw speed,filling ratio or overlapping ratio.The analysis results show that the bottom of the shell and the edge of screw blades are the most vulnerable parts of the double screw conveyor;Particles in the double screw conveyor are easily worn out or broken near the two drive shafts,the bottom of the shell and the edge of two screw blades.And some optimization suggestions are provided according to the phenomena above.4.When the screw speed,filling ratio or overlapping ratio of the double screw conveyor are certain,the influence of different particle viscosity on its performance is obtained through simulation.The simulation shows that the double screw conveyor is more suitable for transporting cohesive materials and its performance is better under different parameters.