Study on a New System of Multi-stage Classification using an Almost Rigidly Rotating Flow

我们研究了一种新的湿式离心分级系统，它采用了一个几乎刚性旋转流。该流动由地转内部区域、非地转Stewartson和Ekman层和/或刚性旋转区域组成。在这个离心系统中。由于我们可以任意增加离心力而不产生任何湍流波动，并且可以很好地控制离心力和流体阻力，所以我们可以通过由于颗粒尺寸的差异而产生的离心力和流体阻力的差异，将悬浮在水中的具有低浓度的非常细的进料颗粒精确地分类为粗产品和细产品。因此，该系统是适用于一个精确的亚微米分级。在本研究中，我们已经处理，作为多级系统的基础上，一个双级系统，可以将饲料颗粒分为粗，中，细产品一次全部。我们已经实验性地研究了间歇式和半连续式的分级性能。因此，我们得出以下结论，其中离心效应参数表征作用在颗粒上的离心力与流体阻力的比率。(1)半连续型（细产品和中等产品均可连续获得）显示出中等产品的变化系数比间歇型（仅细产品可连续获得）稍大，但显示出较小的质量中值直径。(2)在间歇式和半连续式两种类型中，随着离心作用参数的增大，介质产品的质量中值直径和变异系数变小，即介质产品变得更细，粒度更均匀。(3)在每一级作为一个单级分类器的分类性能上，有提取的阶段比没有提取的阶段表现出略差的分类精度。

We have studied a new wet-type centrifugal classification system that employs an almost rigidly rotating flow. This flow consists of geotropic interior regions, ageostrophic Stewartson and Ekman layers, and/or a rigid-rotation region. In this centrifugal system. we can accurately classify very fine feed-particles suspended in water with a low concentration into coarse and fine products by the difference in the centrifugal force and fluid drag exerting particles due to the difference in particle size, because we can increase the centrifugal force arbitrarily without producing any turbulent fluctuation and well manage the centrifugal force and the fluid drag. Hence, this system is adaptable to an accurate submicron classification.In the present study, we have treated, as the basis of the multi-stage system, a double-stage system that can classify feed particles into coarse, medium and fine products all at once. we have experimentally investigated the classification performance of both batch and semi-continuous types. Consequently, we have drawn the following conclusions, where a centrifugal-effect parameter characterizes the ratio of the centrifugal force acting on a particle to the fluid drag.(1) the semi-continuous type (both fine and medium products are obtainable continuously) shows a slightly greater coefficient of variation of the medium product than the batch type (only a fine product is obtainable continuously), but shows a smaller mass median diameter.(2) In both batch and semi-continuous types, with increasing centrifugal-effect parameter, the mass median diameter and coefficient of variation of the medium product become smaller, i.e. the medium product becomes finer and more uniform in particle size.(3) On the classification performance of each stage as a single-stage classifier, the stage with extraction shows a slightly worse classification accuracy than that without extraction.