气流分级机分级过程的数值模拟

发布时间：2018-03-26 15:25

本文选题：气流分级　切入点：两相流　出处：《中国海洋大学》2015年硕士论文

【摘要】：随着超细粉体技术的发展,现代工业对于碳化硅等磨料的粒径要求越来越小、粒度分布也越来越窄,对于分级设备性能的要求也越来越高。FL450型气流分级机作为常用的碳化硅颗粒的分级机设备,弄清其工作原理,操作参数、设备结构参数、物料及介质性质以及设备放大效应对气流分级机分级效果的影响规律,对分级机结构和操作条件的优化,提高设备的分级效率具有重要意义。本文采用数值模拟的方法,利用Fluent软件研究对FLA50型气流分级机分级碳化硅的过程就行研究分析。通过采用离散相模型模拟气流分级机内部的气固两相流,使用随机轨道模型模拟不同粒径颗粒在分级机内的运动轨迹。利用构建好的气流分级机模型,模拟了不同转速和风量、不同叶轮结构和导流锥结构、不同密度材料对分级机内部流场的速度分布的影响以及对分级过程的影响,利用其对分级结果的影响规律,根据生产要求对现有分级操作做出合理的优化设计。得到结论如下：(1)使用离散相模型和随机轨道模型描述气流分级机的分级过程是可行的。(2)本文在忽略颗粒间相互作用的情况下,研究不同粒径颗粒在分级机内部的分级过程,颗粒分级时依然出现了“鱼钩效应”,说明“鱼钩效应”的出现与颗粒在分级过程的中受力情况有关,需要进一步去研究。本文不支持“鱼钩效应”由分级过程中颗粒间的团聚造成这一结论。(3)固定风量调整分级叶轮转速,在适当范围提高转速能够使得分级产品的集中度和收率变高而不影响产品分级效果。当转速超出适当范围时,产品分割粒径d50会下降,分级效果变差；固定分级叶轮转速调整风量,改变风量严重影响产品收率。(4)过少的叶片数量和过厚的叶片都会使得分级过程的分级效果变差甚至没有分级效果。在保证分级效果的前提下,使用叶片数量72片,厚度4mm的分级叶轮较原来的生产过程使用的叶轮产品回收率高；导流锥直径对分级结果影响较大,存在一个最优直径使得分级效果最好。(5)不同密度的物料的在分级机内的分级效果是不一样的,密度为2300kg/m3～4000kg/m3间的物料,密度越大分级效果越好,密度越小分级效果越差。(6)当介质温度由15℃升高到145℃时,会增加大颗粒穿过分级叶轮的比例,不利于分级。(7)分级设备放大会导致分级产品的收率降低,对分级产品的影响较小。
[Abstract]:With the development of superfine powder technology, modern industry for silicon carbide abrasive particle size smaller, narrower grain size distribution, for the classification of equipment performance requirements are increasingly high.FL450 type air classifier as silicon carbide particles commonly used classifier equipment, understand its working principle, operation parameters, equipment structure parameters. Materials and media properties and influence effect on the amplification equipment air classifier classification efficiency, optimization of classifier structure and operating conditions, has important significance to improve the classification efficiency of the equipment. By using numerical simulation method, this research, by using the Fluent software of FLA50 type air classifier classification of silicon carbide on air classifier simulation analysis. The gas-solid two-phase flow by using the discrete phase model, using stochastic trajectory model of particles with different diameters in the classifier The trajectory. Using air classifier model constructed, simulation of different speed and air volume, different impeller structure and guide cone structure, the influence of different material density on the internal flow field of the velocity distribution of the classifier and the influence on the classification process, using its influence to the classification results, according to the production requirements to make reasonable design of the existing grading operation. The conclusions are as follows: (1) classification process using the discrete phase model and the stochastic model to describe the air classifier is feasible. (2) in this paper, ignoring the interaction between particles, the classification process of particles with different diameters in the classifier internal, particle classification still appears the "fish hook effect" that, "fish hook effect" and the stress in the particle grading process, it needs further studies. This paper does not support the "hook effect" by classification In the process of agglomeration of particles caused by this conclusion. (3) fixed air volume adjustment speed to improve the speed of impeller, the concentration and yield of high grade product change without affecting the product classification effect in the appropriate range. When the speed exceeds the proper range, product cut size D50 will decline, grading effect becomes worse; fixed grading impeller speed adjust the air volume, air volume change seriously affect the yield of the product. (4) leaf number and leaf thickness is too small will make the classification effect of classification process variation or no classification effect. Under the premise of ensuring the classification effect, blade number is 72, the recovery of impeller product grading impeller with the thickness of 4mm is the original production process using high rate; guide cone diameter on the classification results are affected, there is an optimal diameter makes the classification best. (5) materials of different density in classifier classification The effect is not the same, the density is 2300kg/m3 ~ 4000kg/m3, the material density is better classification effect, the smaller the density classification effect is worse. (6) when the medium temperature increased from 15 degrees to 145 degrees, will increase the proportion of large particles through the impeller, is not conducive to the classification (7) classification equipment. Amplification leads to graded product yield reduced, less impact on the classification of the product.

【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.8

【参考文献】