Study On Vibrating Screening Process Mechanism Basing On DEM

Screening process theory, a fundamental theory for developing vibrating screening equipment, can offer direction to investigate large vibrating screen with high reliability and optimal control, which is of engineering significance. In order to explore screening process furtherly, this work study screening process with DEM(discrete element method)simulation and experiment. The main achievements are as flowing:Relative fundamental theory of DEM simulation were learned to simulate the process of grain filling hopper using Stream DEM, which compared the filling process based on CPU and GPU. Through this research, the relationship of time consumption and particles number in simulation based on CPU and GPU respectively, which suggests that computer graphics acceleration algorithm based on GPU can significantly improve the operation efficiency of discrete element simulation, and offer reference to enhance DEM simulation efficiency for large number particulate system. Experiment study for screening process was conducted using homemade screen model, which compared screening efficiency, trajectory and velocity of different size particles on screen surface of experiment and DEM simulation to verify the reliability of DEM simulation of screening process. The results show that the relative error of DEM simulation with sphere particles and experiment on screening efficiency and particle velocity range from 11% to 89% and from 0.76% to 28.2%, respectively. The relative error of DEM simulation with non-sphere particles and experiment on screening efficiency and particle velocity range from 5.3% to 12.5% and from 2.55% to 16.8%, respectively. This comparison suggests the DEM simulation with non-sphere particles can more accurately simulate the behavior of particles on screen surface. Circular vibrating screening process is simulated using discrete element method, and analyzes the influence of vibration frequency, inclined angle of screen surface, amplitude and length of screen surface on pulse number and velocity of particles on screen surface, part screening efficiency, which compares the simulation results with theory value. The analysis results are as following. When casting coefficient is less than 3.3, the pulse number of particles on screen surface during per unit time is identified with vibration frequency of screen model, and the relative error of simulation and theory on velocity of particles on screen surface is less than 12%. The results can better reflect movement velocity of particles on screen surface.Screening experiment is conducted with homemade vibrating screen to analyze the influence regulation of vibration parameters on screening efficiency, velocity and pulse number of particles on screen surface. The simulation results are compared with theory value, which shows that the pulse number of particles on screen surface is identified with vibration frequency of screen model, and the relative error of simulation and theory on velocity of particles on screen surface is less than 15%. The results can furtherly verify the reliability of movement velocity formula of particles on screen surface.Based on the results of simulation and experiment, the mathematical model of screening process is optimized by using MATLAB software. The optimal parameters can improve screening efficiency by 11.69%, which can offer theory basics for parameters optimization of vibrating screen.