Developmental study of a new technique to classify submicron particles

本文研究了一种利用刚性旋转机壳与转子之间的准刚性旋转通流的新型分级机，并得到了如下结果。理论结果表明：（1）在内部区域，轴向速度与机壳和转子壁的斜度和曲率有关，而方位速度只与斜度有关。(2)壳体上的Ekman输运与转子上的Ekman输运之比由壳体的斜率函数与转子的斜率函数之比决定。实验结果（1）出现定常轴对称流态的条件是：（）1.6E^<0.46>，其中E和E是Rossby数和Ekman数。(2)内部区域的速度分布与理论结果一致。(3)Stewartson层由强轴向流动的内层和弱反向流动的外层组成。(4)对于只在转子上的Ekman层内供给进料的情况，我们获得了优异的分级效率（锐度指数 * 1.5）。计算分析（1）建立了模拟同轴旋转转子与壳体之间的近刚性旋转通流的计算程序和分析颗粒在流动中运动的计算程序。(2)在分析旋转圆盘与圆柱形槽之间的几乎刚性旋转的通流时，我们用数值方法考虑了目前分级技术的机理。(3)理论和实验结果得到了计算分析的证实。(4)入口处的几乎所有颗粒都通过Ekman layr进入Stewartson layr。(5)在Stewartson层，粗颗粒在离心力的作用下进入刚性旋转区。(6)颗粒分级效率由参数Dp/λ <0Eepsilon>0（Dp ;颗粒直径，E ;埃克曼数，E;罗斯比数）指定。

We have studied a new classifier using the almost rigidly rotating through-flow between rigidly totating housing and rotor, and have obtained the following results.1. Theoretical results(1) In the interior region, the axial velocity depends on slopes and curvatures of the housing and rotor walls, while the azimuthal velocity depends only on the slopes.(2) The ratio of the Ekman transport on the housing to that on the rotor is determinated by the ratio of the function of housing's slope to that of the rotor's.2. Experimental results(1) The condition of occurrence of a steady axisymmetric regime of the flow is epsilon(〕SY.ltorsim.〔)1.6E^<0.46>, Where epsilon and E are Rossby and Ekman numbers.(2) Velocity distributions of the interior region agree with the theoretical results.(3) The Stewartson layr constitutes of the inner layr with a strong axial flow and the outer layr with a weak reverse flow.(4) We got excellent classification efficiency (sharpness index * 1.5) for the case where the feed is supplied only within the Ekman layr on the rotor.3. Computational analysis(1) A computational code to simulate the almost rigidly rotating through-flow between the coaxially rotating rotor and housing and a computational code to analyze motion of particles in the flow are constructed.(2) In the analysis of the almost rigidly rotating through-flow between the rotating disk and cylindrical tank, we have numerically considered the mechanism of the present classification technique.(3) Theoretical and experimental results are confirmed by the computational analysis.(4) Almost all particles at the inlet go to Stewartson layr through Ekman layr.(5) Coarse particles go to rigidly rotating region by the effect of centrifugal force at Stewartson layr.(6) Particle classification efficiency are specified by a parameter Dp/^<0Eepsilon>0 (Dp ; diameter of particles, E ; Ekman number, epsilon ; Rossby number).