Study On Screening Characteristics Of Linear Screen Based On Discrete Element Method

As a screening device for material grading,linear sieve has been used widely in recent years.However,the existing linear screen has problems such as clogging of the screen mesh port and low screening accuracy during use.Therefore,based on the discrete element method,the analysis of the movement and sifting phenomenon of pulverized coal during the screening process can help us to further understand the screening characteristics of the vibrating screen,master the screening theory,and provide a basis for the design and application of linear screens.First,structural design and motion analysis were performed on a linear screen containing a multi-layer screen.Based on the dynamic balance theory,3D modeling software Solidworks and dynamic analysis software Adams were combined to calculate and simulate the motion trajectory of the screen in space.It is found that the trajectory of any point on the screen is similar to an ellipse,and the ellipticity of the trajectory of each point on the screen,from the screen discharge port to the inlet port,is first increased and then decreased.Secondly,the discrete element simulation of the vibrating screening process of pulverized coal was carried out.According to the mechanics of granular materials,DEM discrete element simulation was used to analyze the movement of particles during the screening process,and the influence of the mass flow rate of coal powder inflow and the variation of the mesh excitation frequency on the precision of coal powder screening was studied.It is found that with the increase of the mass flow rate of coal powder inflow,the precision of the screening of each layer of screen is gradually reduced,and the ratio of the precision of the first screen and the third layer is gradually increased.As the excitation frequency of the screen increases,the precision of the screening of each layer of the screen increases first and then decreases,and the ratio of the precision of the first layer of the screen and the third layer of the screen decreases first and then increases.Finally,the pulverized coal vibrating screening experiment platform was set up,and the control variable method was used to carry out the screening accuracy experiment.Throughmutual verification between experiment and simulation analysis,it is found that the maximum inflow pulverized coal mass flow rate of this linear sieve should be lower than 0.3kg·s-1,and the optimal excitation frequency is 18Hz-20 Hz.At the same time,through the comparison of the results,it is proved that the discrete element method has engineering practicability in dealing with the vibration screening problem,and provides reference for the application and expansion of the discrete element method.