Study On Dynamics And Screening Characteristics Of Oversize Vibrating Screen With Statically Indeterminate Mesh Beam Structure

Coal is the primary energy in China.Coal preparation is an effective method for the cleaning and efficient utilization of coal.Screening is an indispensable unit process in coal beneficiation,and vibrating screen is the key screening equipment.It is widely used in the classification,dewatering,medium draining,and desliming of coal.With the increasing number of large-scale coal mines and coal preparation plants,the demand for oversize vibrating screen is becoming huge and progressively urgent.However,there are still several problems in oversize vibrating screen at present,such as poor reliability and low screening efficiency.Consequently,it cannot meet the production requirement of a large coal preparation plant,and restricts the large-scale upgrading of coal in China.Thus,the oversize vibrating screen with high reliability,stable operation and excellent screening effect is becoming the foundation of chinese coal industrial development.In the view of existing problems in oversize vibrating screen,a novel type of oversize vibrating screen was proposed in this dissertation,vibrating screen with statically indeterminate mesh beam structure(VSSIMBS).The dynamic structural response,kinematics law,screening characteristics and impact characteristics of material were researched.The research results provided theoretical support for the dynamic design and efficient operation of oversize vibrating screen.The main works and conclusions are as follows:Firstly,the mechanical model of VSSIMBS was established,and the dynamic parameters were obtained.The structural response of VSSIMBS and traditional vibrating screen was analyzed and compared by finite element method.The influence mechanism of statically indeterminate mesh beam structure on the whole performance of vibrating screen was revealed.The result showed that statically indeterminate mesh beam structure could improve the stress distribution of screen body,reduce the maximum stress,decrease high stress areas,and increase the strength and stiffness of vibrating screen.Finally,full-scale experiment on VSSIMBS was tested in field,and the test results proved the correctness of simulation.Secondly,the kinematic differential equation of VSSIMBS was deduced based on Lagrange equation,the dynamic model was established,and steady-state response was obtained.The force condition of eccentric blocks during operation process was analyzed,and the condition for the stable operation was obtained.Electromechanical coupling simulation model of VSSIMBS was built based on kinematic differential equation,and the number simulation of operation process was carried out.Through frequency control test and vibration synchronization test,the effect of the output characteristics difference of drving motors on the operation stability of vibration systerm was analyzed.The dynamic test on VSSIMBS prototype was made,and test results were discussed and analyzed.Thirdly,the probability screening model of VSSIMBS was established by discrete element method,the screening process was simulated,and the screening efficiency of vibrating screen was obtained.The influence law and optimal value interval of amplitude,frequency and vibration direction angle on screening efficiency were analyzed by single factor test.The respond surface test was designed,and the quadratic polynomial regression equation of vibration parameters on screening efficiency was obtained,and the optimization scheme with highest screening efficiency could be found.The test data was fitted by using BP and GRNN neural network respectively.The parameter optimization of neural network model after fitting was carried out by genetic algorithm,and more accurate optimization scheme was obtained.Finally,the motion of particle on vibrating screen surface was analyzed,the impact theoretical model of particle on screen surface was established,and the mathematical expression of maximum impact force was obtained.In order to reflect the comprehensive performance of VSSIMBS,the multi-index evaluation system was built.Dynamic structural response of screen surface during screening process was analyzed by discrete-finite element coupling method,and the arrangement of supporting beams was optimized based on analysis results to reduce the stress and deformation of screen surface.The orthogonal test was designed,and the influence degree and significance of vibration parameters on evaluation indexes were obtained.The optimization schemes for every index were put forward,and the multi-index optimization scheme was present based on comprehensive balance principle.