从20世纪80年代起，超细粉体技术逐渐发展起来，在电子技术、矿业冶金、印刷涂料、磁性记录材料、能源环保、医药食品等领域占有举足轻重的地位。机械粉碎法因其可以大批量生产，并且成本较低，成为工业上超细粉体生产的主要方法。但机械粉碎法生产的超细粉体往往存在粒度分布不均匀，形貌不规则等诸多缺陷，不能满足现代工业对粉体质量的要求。如何生产粒度小且分布窄的超细粉体成为粉体制造领域的难题。鉴于此，工业上往往对机械粉碎法生产出来的粉体进行再次加工，也就是对粉体进行分级。目前对粉体分级主要有干法分级和湿法分级，湿法分级因其分级粒径小、分级效率高而被广泛运用于亚微米精细粉体的制备。如何提高分级机的工作效率和精度，减小细粉的粒度成为业内研究的热点。本课题组研发的一款超细粉体湿法离心分级机，具有分级粒径小、工作效率高、工作压力低、出料不易堵塞和易维护等优点，并且可以通过变频电机改变分级轮转速，从而调节分级粒径的大小。本文针对这款新型超细粉体离心分级机的关键结构和分级腔流场进行了研究，主要内容如下：（1）对分级机分级机理和基本结构进行分析，通过对分级腔内固体颗粒进行受力分析，总结了影响分级机工作性能的主要参数，分为结构参数和操作参数，为后文研究指明了研究方向。（2）利用数值模拟仿真方法，分析不同结构叶片对分级腔内流场的影响，重点研究了流体速度分布情况和压力分布情况，为分级轮叶片结构设计提供了可靠依据。（3）利用FLUENT离散相模型，研究单个粒子的受力情况，观察单个粒子的运动轨迹，仿真研究了超细粉体离心分级机分级轮转速与分级粒径大小的关系。（4）搭建超细粉体离心分级机实验研究平台，测量了不同转速下分级后细料产品的粒径大小和分布情况，分析了不同转速下分级的分级精度，将实验数据与模拟结果进行了对比，对数值模拟仿真的合理性进行了验证。
Since the 1980s, ultrafine powder technology gradually developed, and hold a significant position in the field of electronics, mining, metallurgy, printing, paint, magnetic recording materials, energy, environmental protection, medicine, food and so on. Mechanical smash become the main method of mass production of ultrafine powder in the industry production because of its mass production and low cost. However, ultrafine powders produced by mechanical smash always have uneven distribution of particle size, irregular topography, and many other defects. These powders cannot meet the requirements of powder quality in modern industry. How to produce small particle size and narrow particle size distribution of ultrafine powders becomes a difficult problem of the preparation of ultrafine powders. Therefore, ultrafine powders produced by mechanical smash need to be processed again in the industry, namely powder classification. At present, powder classification is mainly divided into dry classification and wet classification, and wet classification is widely used in the preparation of submicron fine powder because of its small grading size and high grading efficiency. How to improve the work efficiency and accuracy of classifier, and reduce the particle size of fine powders becomes the hot spot of research.Our team developed an ultrafine powder wet centrifugal classifier. This classifier has a small grading size, high working efficiency, low working pressure, smooth output, easy maintenance and a series of advantages. It also can change the rotary speed of the grading wheel by frequency conversion motor, so as to change the grading size. In this paper, the key structures and the flow field in the grading chamber of this new ultrafine powder centrifugal classifier were studied. The main contents are as follows:(1) Grading mechanism and basic structures of classifier were analyzed, and the main parameters influencing the working performance were summarized through the stress analysis of the solid articles in the grading chamber. It mainly included structure parameters and operating parameters, and it pointed out the research direction for the later research.(2) By using numerical simulation method, the influence on the flow field in the grading chamber of different structure blades was studied, which mainly included the fluid velocity distribution and pressure distribution. These provided a reliable basis for the design of grading wheel blades.(3) By using FLUENT discrete phase model, the force of the individual particles was studied. The relationship between the rotary speed of grading wheel and cut size was analyzed by the observation of a single particle trajectory.(4) The experiment platform of ultrafine powder centrifugal classifier was set up. The particle size and distribution of the fine powder after grading were measured under different rotary speed, and the grading accuracy was also analyzed. Compared the experimental data and simulation results, the rationality of the numerical simulation analysis was verified.
