【作者】 张立；

【导师】 宋伟刚；

【作者基本信息】 东北大学 ， 机械工程（专业学位）， 2020， 硕士

【摘要】 转载系统作为输送机的重要组成部分,在其工作过程中由于物料的冲击和破碎所带来的粉尘污染是一个很严重的问题。物料在转载系统内的流动是一个散状物料和空气、粉尘相互作用的复杂力学过程,单纯使用离散单元法或运用流体力学的知识并不能完全描述转载系统内的运动状态,因此需要使用DEM-CFD耦合的方式来研究粉尘的运动状态。转载系统中的物料运行稳定以后,粉尘颗粒在重力作用下会进行不同程度的沉降,而粉尘具体的运动状态与其粒径大小有关。以导料槽中粉尘的沉降和扩散为例,采用FLUENT软件中的Discrete Phase Mode进行分析,得到的仿真结果表明粉尘粒径小于30μm时不易沉降,而粒径大于90μm时能够快速沉降到导料槽中。针对常见的直线和曲线式落料管转载系统建立相应的几何模型,并采用EDEM-FLUENT耦合技术中的Euler模型对物料和粉尘进行了分析,其中使用EDEM软件分析了物料颗粒的运动情况和受力关系,使用FLUENT软件中的DPM模型分析了空气和粉尘的流动情况。在FLUENT后处理模块中得到转载系统内气体压强以及流体速度等情况,并针对输送带速度、落料高度等影响因素进行对比仿真,得到的仿真结果表明输送带速度增大和落料高度增加均会引起粉尘浓度的增大。基于EDEM-FLUENT耦合技术,对引风管抑尘转载系统进行了仿真分析,并对引风管抑尘转载系统和直线式落料管转载系统模型进行了对比分析,得到引风管抑尘转载系统导料槽出口气体体积流量值减小了 5.80%,并建立了引风管内气体回流强度的评价指标。当引风管的直径分别为300mm、400mm、500mm、600mm时,抑尘效果最好的模型中引风管直径是400mm。在无动力抑尘转载系统中,为防止含尘空气排放到作业空间内,需要保证转载系统的导料槽密封性能良好,因此导料槽的结构比较复杂。针对导料槽内粉尘外溢的现象,空气刮刀抑尘设备是通过悬浮在输送带上的连续排列的刮刀利用空气吸力使粉尘在输送带上随物料转载出去的,与输送带无接触且导料槽无需密封。本文通过FLUENT软件实现了对该设备中含尘气体运动的可视化呈现,同时对影响该设备抑尘效果的因素进行了对比仿真,得出当刮刀与输送带运动方向成50°角时,系统抑尘效果最好。更多还原

【Abstract】 As an important part of the conveyor,the transfer station is suffering very serious dust pollution caused by the striking and crushing of materials during work,which is a serious problem.The material flowing process in the transfer system is a complex mechanical process which includes the interaction among loose materials,air and dust.This project adopts DEM-CFD coupling method to analyze the movement of dust since discrete element method or hydromechanics cannot fully describe the motion state in the transfer system.The dust particles will subside by different degree due to the effect of gravity after the movement of material is stable in the transfer,and the specific movement state of the dust is related to the diameter of the particle.Taking the subsidence and diffusion of dust in the guide chute as an example,this project uses Discrete Phase Mode of FLUENT to do the analysis.The result obtained is that it is uneasy for the particle to subside to the guide chute when its diameter is less than 30 μm and its easy for the particle to subside to the guide chute when its diameter is longer than 90 μm.In this study,the corresponding geometric models is established according to the common straight and curved blanking tubes of conveyor transfer systems.Using the Euler model in the EDEM-FLUENT coupling technology,the movement and stress condition of material particles are analyzed by EDEM and the flow of air and dust are analyzed by Discrete Phase Model of FLUENT.In the FLUENT post-processing module,the gas pressure,flow velocity and other parameters in the transfer system are obtained.The comparison simulation is carried out for influencing factors such as the belt speed and the falling height and the result is that the concentration of dust will increase along the increase of the belt speed and the falling height.Beside this,based on EDEM-FLUENT coupling technology,the simulation analysis is done for the dust suppression transfer system with guide duct.The comparison analysis is done between dust suppression transfer system with guide duct and the ordinary transfer station with linear blanking pipe.The result shows that the induced air outlet of dust suppression transfer system with guide duct decreases 5.80%compared to the ordinary transfer station with linear blanking pipe.The evaluation index of reflow strength in the air pipe is established according to the result.When the diameter of the guide duct is 300mm,400mm,500mm,and 600mm,the diameter of the guide duct in the model with the best dust suppression effect is 400mm.In an unpowered dust suppression and transfer system,in order to prevent dust-containing air from being discharged into the working space,it is necessary to ensure that the guide groove of the transfer system has a good sealing performance,so the structure design of the guide groove is relatively complicated.As for the phenomenon of gas overflow in the material guide chute,the Airscrape equipment uses air suction to transfer the dust on the conveyor belt with the material through the continuously arranged scrapers suspended on the conveyor belt.There is no contact with the conveyor belt and the material guide chute does not need to be sealed.In this project,FLUENT is used to visualize the airflow movement and dust movement in the equipment.At the same time,the factors that affect the dust suppression effect of the equipment are compared and analyzed.The system has the best dust suppression effect when the scrapes is at an angle of 50° to the moving direction of the conveyor belt.更多还原