椭球形颗粒直线振动筛分机理研究

发布时间：2018-12-12 09:36

【摘要】：筛分是各领域中散体料进行粒度分级的主要技术手段;在各类筛分物料中,椭球形或类椭球形颗粒占较大比例,椭球形颗粒长直径远大于短直径的外形特性,导致其筛分特性相对球形颗粒更为复杂。目前,对椭球形颗粒精选筛分,缺乏针对性筛分机理及装置的研究,采用传统的筛分方法,并以球形颗粒筛分机理控制参数进行椭球形颗粒筛分,其筛分性能差。为此,本文结合直线振动筛分具有高筛分效率、高生产率,且对椭球形颗粒筛分适应性好的特点,提出椭球形颗粒直线振动筛分方法,以类椭球形颗粒枸杞为筛分对象,开展椭球形颗粒直线振动筛分机理研究。主要研究工作内容与结论如下:(1)椭球形颗粒直线振动筛分理论研究基于直线振动筛分理论,以筛分分离粒度和综合筛分效率为基础筛分性能指标,研究椭球形颗粒直线振动筛分过程的颗粒运动学特性、透筛特性及其影响因素;结果表明:筛分分离粒度是一个区间范围?d,颗粒沿筛面方向的相对速度越大,分离粒度越小;椭球形颗粒物料在筛面上做周期性相对下滑和相对上滑移动,同时,做周期性相对筛面向上、向下摇摆滚动,因此,若颗粒垂直筛面方向的跳动较大时,不该透筛的较大粒度的椭球形颗粒会竖直或倾斜穿过筛孔,造成误筛,使得分离粒度上限值增大,分离粒度区间?d增大,综合筛分效率降低。研究了厚层椭球形颗粒直线振动分层原理及其影响因素,并设计分层性能指标检测方法,结果表明:不同粒度颗粒的动能差异是形成颗粒分层的主要原因,细粒或粗粒体积浓度的变化率是检测颗粒分层速率的有效可行方法。(2)椭球形颗粒直线振动筛分仿真分析利用离散元软件EDEM,对单层椭球形颗粒在筛面上的运动特性进行仿真分析,结果表明:颗粒群在筛面x方向的相对速度和绝对速度具有与振动筛面相同的周期性;颗粒群相对速度是时间的类余弦曲线,平均相对速度、平均绝对速度随着筛分参数(筛面倾角、振幅、频率、振动方向角)的增大而增大;当筛分参数大于一定值之后,颗粒群出现垂直筛面方向的跳动,且筛分参数值越大,跳动量越大。对单层椭球形颗粒筛分分离粒度、综合筛分效率进行仿真分析,结果表明:筛分分离粒度为一个范围(mind~maxd),筛分分离粒度(分离粒度上限maxd、下限mind和中心cd)随着筛分参数的增大而减小,随筛孔直径增大而增大;验证了?d受颗粒跳动的影响,当颗粒群在垂直筛面方向上有跳动时,?d随着振幅、频率和方向角增大而增大,综合筛分效率降低,筛面倾角在取值范围内,因颗粒群垂直筛面方向无跳动,?d不变,故不影响综合筛分效率。对厚层椭球形颗粒直线振动分层特性及颗粒运动动能仿真分析,结果表明:椭球形颗粒振动分层过程中,大颗粒与小颗粒垂直筛面方向的动能差随着振幅、频率、振动方向角的增大而增大,筛面倾角对其影响不大;颗粒分层速率随着振幅、频率和振动方向角的增大而增大,筛面倾角对颗粒分层速率影响较小,颗粒分层速率随时间的推移越来越小。(3)椭球形颗粒直线振动筛分性能试验研究设计直线振动筛分试验装置,对椭球形颗粒枸杞进行直线振动筛分性能试验及结果分析。试验结果验证了单层颗粒筛分中振幅、频率以及筛面倾角对筛分分离粒度以及综合筛分效率的影响规律;验证厚层筛分中振动幅度、振动频率以及筛面倾角对颗粒分层速率的影响规律。得到较佳筛分性能参数为振幅为4mm、频率为20HZ、筛面倾角为8°时,其筛分效率为93.6%,筛分生产率为1.54t/h。
[Abstract]:The sieving is the main technical means for the particle size grading of the dispersion materials in all fields; in the various screening materials, the ellipsoidal or the like-like particles occupy a larger proportion, the long diameter of the ellipsoidal particle is much larger than the outer shape characteristic of the short diameter, and the screening characteristic is more complex with the spherical particles. At present, the selection and screening of the ellipsoidal particles, the lack of the targeted screening mechanism and the research of the device, the traditional screening method is adopted, and the spherical particle screening is carried out by the spherical particle screening mechanism control parameters, and the screening performance is poor. in ord to solve that problem, the linear vibrating screen is combine to have the characteristics of high screening efficiency, high productivity, and good screening adaptability to the ellipsoidal particle, Study on the mechanism of linear vibrating screen for ellipsoidal particle. The main research contents and conclusions are as follows: (1) The theoretical study of the linear vibrating screen of the ellipsoidal particle is based on the principle of the linear vibrating screen, and based on the screening separation size and the comprehensive screening efficiency as the basic screening performance index, The characteristics of the particle kinematics, the characteristics of the screen and the influencing factors of the elliptic particle linear vibrating screen are studied. The results show that the size of the sieve separation is an interval range. d, the greater the relative speed of the particles in the direction of the screen surface, the smaller the separation particle size, If the direction of the vertical screen of the particles is large, the spherical particles of the larger particle size of the screen not to be passed through the sieve are vertical or inclined to cause a false screen, so that the upper limit value of the separation particle size is increased, and the particle size range is separated. and d is increased, and the comprehensive screening efficiency is reduced. The principle of linear vibration of thick-layer ellipsoidal particle and its influencing factors are studied, and the test method of layered performance index is designed. The results show that the difference of the kinetic energy of different particle size particles is the main reason for the formation of the particles. The rate of change in the volume concentration of fine or coarse particles is an effective and feasible method for detecting the rate of particle delamination. (2) The dynamic characteristics of the single-layer ellipsoidal particle on the screen surface were simulated and analyzed by using the discrete element software EDEM, and the results showed that the relative velocity and absolute velocity of the particle group in the x-direction of the screen surface had the same periodicity as the vibrating screen surface. the relative speed of the particle group is the cosine curve of the time, the average relative speed, the average absolute speed is increased with the increase of the sieving parameters (screen inclination, amplitude, frequency, vibration direction angle), and the larger the sieving parameter value, the larger the jump amount. The results show that the separation size of the sieve is a range (mind.to maxd), the size of the separation and separation (the upper limit of the separation particle size maxd, the lower limit mind, and the center cd) decreases with the increase of the screening parameters. Increase with the diameter of the mesh; verified? d is affected by the particle run-out, when the particle swarm has a run-out in the direction of the vertical screen surface? d With the increase of the amplitude, frequency and direction angle, the comprehensive screening efficiency is reduced, and the inclination of the screen surface is in the range of value. and d, so the comprehensive screening efficiency is not affected. The results show that the difference of the kinetic energy of the large particle and the small particle in the plane of the vertical screen increases with the increase of the amplitude, frequency and vibration direction in the process of the vibration of the ellipsoidal particle. The influence of the angle of the screen surface is not large; the particle layer rate is increased with the increase of the amplitude, the frequency and the vibration direction angle, the influence of the inclination of the screen surface on the layer rate of the particles is small, and the layering rate of the particles is smaller and smaller over time. (3) The design of the linear vibrating screen sub-test device for the ellipsoidal particle linear vibrating screen is carried out, and the test of the linear vibrating screen and the result analysis of the ellipsoidal granular medlar are carried out. The influence of the amplitude, frequency and the angle of the screen on the separation size of the screen and the efficiency of the comprehensive screening is verified by the test results, and the influence of the vibration amplitude, the frequency of the vibration and the angle of the screen surface on the rate of the granular layer is verified. The screening efficiency was 93.6% and the screening rate was 1.54t/ h.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH237.6

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