卸料斗几何参数对自由下落微粒流流场特性的影响研究

发布时间：2018-05-18 06:50

本文选题：卸料斗几何参数 + 微粒流　；参考：《天津商业大学》2015年硕士论文

【摘要】：在工业生产和散装物料(如黄沙、煤炭以及粮食颗粒等)运输和卸料的过程中,进行自由下落运动的散料微粒流到处可见。微粒流在自由下落过程中由于受重力、浮力、颗粒之间摩擦阻力以及颗粒与环境空气之间作用力的影响,会导致环境空气被卷吸到微粒流束流场中形成微粒羽流。微粒羽流在自由下落过程中,当散料碰到底端接收装置时,由于下落散料的冲击力,促使散料粉尘逃逸到周围环境空气中造成环境污染,给工作人员的身心健康带来巨大的损害。本课题跟踪国际前沿、针对生产实际应用,以卸料斗自身结构为研究对象,运用EDEM颗粒元软件与Fluent软件对散状物料经卸料斗自由下落时与环境空气之间的耦合规律以及卸料斗几何参数、颗粒物料物性参数之间的关系进行数值模拟；在自由下落微粒流与环境空气关系的多功能实验平台上,通过改进卸料斗结构(卸料斗的倾斜角度a、卸料斗的初始下落口径D),对微粒流在环境空气中自由下落时的产尘量G进行实际测量,以期获得产尘量G最小的卸料斗。通过数值模拟和实验研究得出如下结论：(1)数值模拟结果表明：a)卸料质量流量Ws随着倾斜角度(?)、内摩擦系数μ、壁摩擦系数μW不断增加而减小。当53°(?)≤55°时,卸料质量流量Ws随卸料斗倾斜角度a的增加减少的幅度较大；而当55°(?)≤60°时,卸料质量流量Ws随卸料斗倾斜角度a的增加的减少的幅度较小。在本课题的研究范围内卸料质量流量Ws与内摩擦系数μ之间的关系表达式为：Ws=195.83×exp[0.095/(μ+0.176)],在本课题的研究范围内卸料质量流量Ws与壁摩擦系数μs之间的关系表达式为：Ws=322.5-416.3μw736.2μw2-638.6μw3+211.4μw4。b)计算区域内的颗粒浓度、微粒流流速v随初始下落口径D的增加而不断增大；在初始下落口径为0.0lm时,颗粒浓度最小,而当初始下落口径D为0.03m时,颗粒浓度最大。在微粒下落的初始阶段,微粒流流速v随着下落高度h的增加而增加,当下落高度h增长到某一定值时,微粒流流速v趋于稳定；微粒流流速v随着初始下落口口径D的增加而增加,当初始下落口径D为0.0lm时,微粒流速Vmax为2.28m/s,初始下落口径D为0.03m时,微粒流速Vmax为3.5 m/s。c)计算区域内颗粒的扩散半径随微粒密度ρp的增加而逐渐减小。在微粒下落的初始阶段,微粒流流速v随着下落高度h的增加而增加,当下落高度h增长到某一定值时,微粒流流速v趋于稳定；微粒流流速v随着微粒流密度ρp的增加而增加,当微粒密度ρp为790kg/m3时,微粒流速vmax为1.21 m/s,微粒密度ρp为2590 kg/m3时,微粒流速Vmax为2.83m/s。d)计算区域内颗粒的扩散半径随微粒粒径dp的增大而不断减小,颗粒的停留时间t随之减小；当微粒粒径dp为186.42×10-6m时,颗粒与环境空气的混合程度较好,颗粒在计算区域的停留时间较长,扩散半径也较大,相反在微粒粒径dp为767.13×10-6m时,颗粒在计算区域的停留时间较短,扩散半径也较小。在微粒下落的初始阶段,微粒流流速v随着下落高度h的增加而增加,当下落高度h增长到某一定值时,微粒流流速v趋于稳定；微粒流流速v随着微粒粒径dp的增加而增加,当微粒粒径dp为186.42×106m时,微粒流速Vmax为1.01 m/s,微粒粒径为767.13×106m时,微粒流速Vmax为2.54 m/s。(2)实验研究结果表明：各种结构(倾斜角度)的卸料斗都有其合理的使用范围,在工程实际应用中要根据物料的特性选用合适结构的卸料斗,如使得黄沙微粒流产尘量G最小的卸料斗角度为58°、玉米微粒流产尘量G最小的卸料斗角度为57°,而二氧化硅微粒流产尘量G最大的卸料斗角度为54°(3)通过实验数据与模拟数据的对比分析,发现微粒流在下落过程中速度的实验结果与模拟结果基本吻合,因此,实验研究与数值模拟计算均可以用来研究卸料斗结构对自由下落微粒流流场特性以及产尘量G的影响规律。(4)采用数学的方法,运用π定理以及多元线性回归分析的方法对大量的实验数据进行线性拟合,最终得出自由下落微粒流产尘量G与微粒流的质量流量Mρ、初始下落口径D、下降高度h、微粒密度ρp、微粒粒径dp、空气密度ρa及卸料斗的倾斜角度a之间经验公式：G=2.28e20.D1.55648.dp-0.30275.h1.85923.ρp1.31621.ρa-1.31621.α-7.05575
[Abstract]:In the process of transportation and unloading of industrial and bulk materials, such as sand, coal, and grain particles, free falling particles are seen everywhere. The influence of gravity, buoyancy, friction resistance between particles and the force between particles and ambient air during the free falling process leads to the environment. The air is absorbed into the flow field of particles to form a particle plume in the flow field of particles. In the process of free fall, the particle plume will cause environmental pollution in the ambient air, resulting in great damage to the physical and mental health of the workers. The international frontier, aiming at the practical application of production, takes the self structure of the hopper as the research object, and uses the EDEM particle element software and Fluent software to simulate the relationship between the free falling of the discharge hopper and the ambient air when the discharge hopper is free and the relation between the geometric parameters of the hopper and the physical parameters of the granular material. On the multi-functional experimental platform of the relation between the particle flow and the ambient air, by improving the structure of the hopper (the tilt angle of the hopper a, the initial drop diameter of the hopper D), the actual measurement of the dust amount G when the particle flow is freely falling in the ambient air is carried out in order to obtain the least dusts with the dust amount of G. The numerical simulation and experimental study are obtained. The following conclusions are as follows: (1) the numerical simulation results show that the discharge quality flow Ws decreases with the increasing of the angle (?), the internal friction coefficient and the wall friction coefficient mu W. When the 53 degree (?) less than 55 degrees, the discharge quality flow Ws decreases with the increase of the a of the hopper angle a; and the discharge quality flow Ws is unloaded when the discharge quantity is less than 60 degrees. The decreasing amplitude of the increase of the hopper inclination angle a is smaller. The relation expression between the discharge mass flow Ws and the internal friction coefficient um is Ws=195.83 x exp[0.095/ (mu +0.176) in the research scope of the subject. The relation expression between the discharge mass flow Ws and the wall friction coefficient mu s is: Ws=322.5-416 in the scope of the study. The particle concentration in the region is calculated by.3 mu w736.2 w2-638.6 mu w3+211.4 mu w4.b. The particle flow velocity V increases with the increase of the initial drop diameter D, and the particle concentration is the smallest when the initial falling aperture is 0.0lm, while the particle concentration is the largest when the initial falling aperture D is 0.03m. The particle flow velocity is v along with the initial phase of the particle drop. When the falling height of H increases, the particle flow velocity V tends to be stable when the falling height of H increases to a certain value, and the particle flow velocity V increases with the increase of the initial drop aperture D. When the initial drop aperture D is 0.0lm, the particle velocity Vmax is 2.28m/s, the initial falling diameter D is 0.03m, the particle velocity Vmax is 3.5 The diffusion radius of the inner particles gradually decreases with the increase of the particle density of P P. In the initial stage of the particle drop, the flow velocity V increases with the increase of the drop height h. When the drop height h increases to a certain value, the particle flow velocity V tends to be stable; the particle flow velocity V increases with the increase of the micro particle density p p, when the particle density is density. When the p p is 790kg/m3, the particle velocity Vmax is 1.21 m/s, the particle density p p is 2590 kg/m3, the particle velocity Vmax is 2.83m/s.d). The particle diffusion radius decreases with the increase of particle size DP, and the retention time t decreases with the particle size. When the particle size DP is 186.42 * 10-6m, the mixing degree of particles with ambient air is more than that of the ambient air. Well, the retention time of the particles in the calculation area is longer and the diffusion radius is larger. On the contrary, when the particle size DP is 767.13 x 10-6m, the retention time of the particles in the calculated area is shorter and the diffusion radius is smaller. The velocity V of the particle flow increases with the increase of the falling height h in the initial stage of the particle drop, and when the falling height h increases to a certain value, the particle flow velocity is increased to a certain value. When the particle flow velocity V tends to be stable, the particle flow velocity V increases with the increase of the particle size DP. When the particle size DP is 186.42 x 106m, the particle velocity Vmax is 1.01 m/s and the particle size is 767.13 x 106m, and the particle velocity Vmax is 2.54 m/s. (2). The experimental results show that all kinds of structure (inclined angle) discharge hoppers are all reasonable. In the application range, in the practical application of the project, the proper structure of the discharge hopper should be selected according to the material characteristics. For example, the angle of the minimum discharge bucket of the G of the yellow sand particles is 58, the angle of the minimum unload hopper of G for the corn particle miscarriage is 57 degrees, and the maximum hopper angle of the silica particle miscarriage dust is 54 degrees (3) through the experimental number (54 degrees). According to the comparison and analysis of the simulated data, it is found that the experimental results of the velocity of the particle flow are basically consistent with the simulation results. Therefore, both the experimental and numerical simulation can be used to study the effect of the structure of the hopper on the flow field characteristics of free falling particles and the effect of the dust production G. (4) the method of mathematics and the application of the PI theorem are used. And the method of multivariate linear regression analysis is linear fitting for a large number of experimental data. Finally, the mass flow of free falling particles G and particle flow mass flow M rho, initial drop diameter D, drop height h, particle density p p, particle size DP, air density rho A and tilt angle a of discharging hopper: G=2.28e20.D1.5 5648.dp-0.30275.h1.85923. P p1.31621. P a-1.31621. alpha -7.05575
【学位授予单位】：天津商业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X513

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