| Belt conveyor is one of the most important bulk material transportation equipment in the world,which has the advantages of large throughput,simple structure,convenient maintenance,low cost and strong universality,and is widely used in coal metallurgy,transportation,hydropower,chemical industry and other departments.In order to solve the problem of energy consumption caused by friction between conveyor belt idlers and conveyor belt,permanent magnetic suspension belt conveyor came into being.The permanent magnet supporting structure is used to replace the idlers of the common belt conveyor,so that the magnetic conveyor belt carrying materials is suspended and the idlers can be operated without low resistance.In this paper,theoretical calculation,simulation analysis,experimental verification and other methods are used to study the mechanical characteristics of the vertical stability,lateral stability and magnetic resistance of the suspension force of the permanent magnetic suspension belt conveyor.The main research work is as follows:Force balance of permanent magnetic suspension support system of magnetic conveyor belt is the primary problem in the operation of permanent magnetic suspension belt conveyor.The expression of magnetic susceptibility strength and the difficulty in solving the correction coefficient are two important factors that limit the wide application of the existing formulas for calculating suspension force in permanent magnet suspension support system.Based on the hypothesis of molecular circulation and the bioslaw law,the mathematical expression of the magnetic field around the two phase repulsion ndfeb permanent magnet is given in this paper.A device for measuring the suspension force of air gap was designed and manufactured and relevant tests were carried out.Stability is an important factor affecting the normal operation of the permanent magnetic suspension belt conveyor.To solve the vertical stability problem,a vertical random vibration mathematical model of suspension support device was established based on the mathematical model of suspension force of permanent magnet suspension belt conveyor.The single-point suspension system was equivalent to non-linear spring,and the vibration characteristics of the single-point suspension system model under random load were numerically solved.In order to explore the vertical vibration characteristics of the permanent magnet suspension system in a more general sense,the permanent magnets of the suspension system were divided into blocks and the influence of the thickness of permanent magnets and the size of air gap on the suspension force was analyzed.The suspension system is equivalent to a magnetic spring,and the expression of dynamic characteristics of a spring with variable stiffness is given by quadratic fitting.ADAMS software simulation results show that the permanent magnetic levitation system can be stabilized by its own dynamic adjustment under the effect of random load disturbance,and has the function of vertical adaptive dynamic adjustment.Aiming at the lateral stability problem,three types of suspension support structures,namely,flat V type and groove type,were analyzed,and the groove structure with the best bearing capacity and anti-deviation comprehensive performance was selected for research.The results show that the lateral direction of the permanent magnetic levitation device with slot structure can be adjusted automatically.The permanent magnetic suspension belt conveyor realizes the magnetic suspension support without idlers,and the magnetic resistance becomes the main operating resistance.This paper explores the variation law of magnetic resistance under the influence of air gap permanent magnet material,permanent magnet spacing and other factors at different speeds,so as to provide a basis for the structural size design of permanent magnet suspension system and the selection of permanent magnet parameters.In order to comprehensively describe the working performance of the permanent magnet suspension belt conveyor and optimize the working efficiency of the permanent magnet suspension system,a method for determining the optimal floating resistance ratio of the permanent magnet suspension belt conveyor was proposed,taking the floating resistance ratio(the ratio of levitation force to magnetic resistance)as the optimization objective.A mathematical model is established to optimize the floating-drag ratio considering the velocity,and the optimal running speed of the magnetic belt is given,which provides a reference for the selection of the optimal operating parameters of the permanent magnetic suspension system.Aiming at the problems of low magnetic density utilization rate of permanent magnetic suspension belt conveyor,the supporting structure of Halbach type permanent magnetic suspension belt conveyor was proposed,and the magnetic field intensity and distribution of the Halbach type model were studied.The results show that the magnetic induction intensity of the Halbach model is about 2 times higher than that of the traditional model at 4mm on the permanent magnet surface and the magnetic field is mainly distributed in the middle of permanent magnet,which is beneficial to the arrangement of magnetic belt.The influence of magnetic belt width and thickness and permanent magnet thickness on magnetic belt suspension force in the Halbach model was analyzed,and the size parameters of the permanent magnetic suspension system were optimized.The calculation results show that the suspension force of the Halbach model can be about 3 times larger than that of the traditional permanent magnet model.The physical prototype of permanent magnetic suspension belt conveyor was made,and the driving device of drum group of permanent magnetic suspension support device was designed.The suspension characteristics of the prototype were observed in trial operation,and the suspension forces of the prototype were measured respectively under static and operational conditions.The feasibility of applying the theory of permanent magnetic suspension in belt conveyor is verified.Figure[90]table[19]reference[148]. |
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