Simulation And Analysis Of Transport Characteristics And Optimization Of Shield Screw Conveyor Based On Discrete Element

As an important part of the conveying system of the earth pressure balance shield machine,screw conveyor have excellent slag discharge capacity,its spiral blade has high strength and wear resistance,spiral blade structure is closely related to transport performance,power loss and wear resistance.In this thesis,the shield screw conveyor with different blade profile and uniform pitch is simulated and analyzed by discrete element,the influence of helix structure on conveying performance and the main factors affecting the conveying performance is studied.the parameter optimization model of screw conveyor is established,the optimization is completed and the effectiveness of optimization is verified.The main research contents of this thesis are as follows:(1)The pressure-bearing,mechanical and kinematic analysis of the conveying medium of the earth pressure balance shield screw convey is carried out,the conveying principle is analyzed,and the influence of screw blade structure and pitch variation on conveying performance is discussed theoretically,which provides a basis for subsequent simulation analysis of conveyor.(2)The conveying process of shield screw conveyor is simulated by discrete element software EDEM,and the reliability of the simulation model is verified by analyzing the simulation results.The operation process of the shield screw conveyor under straight line,broken line and curve bus spiral blade and uniform pitch is simulated respectively,and the performance indexes of the conveyor is obtained,and the influence of different blade shape and uniform pitch on the conveying performance is analyzed.(3)The installation Angle,pitch,shaft diameter and inner diameter of the shield screw conveyor are determined as the optimization parameters,and the mass flow rate of the conveyor,the average wear amount of the screw and the power loss are determined as the optimization objectives,the discrete element method and orthogonal test were used to obtain the numerical results of the performance indexes and the range is calculated.The influence degree of each parameter on the indexes was analyzed.The mathematical relationship between the structure parameters and performance indexes of the screw conveyor was established by the data fitting method of least square.(4)The constraint conditions in the optimization process are analyzed and the optimization model of shield screw conveyor of earth pressure balance is established.NSGA-Ⅱ(multi-objective genetic)algorithm combined with entropy weight and TOPSIS(ideal approximation)method is used to optimize the structure parameters of the conveyor,and the effectiveness of the optimization is verified by simulation.The optimized shield screw conveyor improves the transport capacity,reduces the wear of the screw shaft and reduces the power loss.