STUDY ON ACCURATE-HIGH SPEED POWDER CLASSIFICATION SYSTEM CONSIDERING PARTICLE CHARACTERISTICS

我们提出了一种新的湿式离心式分级系统，该系统可以应用稳定的轴对称几乎刚性旋转的流动。该分级系统具有明显的特点，可以任意设定离心力与作用在颗粒上的流体阻力之比，并可以通过数值模拟从颗粒运动轨迹上从理论上探讨分级机理。我们以前考察了不同通过流量和转速下的分级性能，并阐明了从一微米到亚微米范围内具有接近一真比重的球形颗粒的锐度指数和切割尺寸与Ekman数和Rossby数的关系。然而，该系统的吞吐量很小。工业需要还要求对形状各异、真比重大于2的颗粒材料进行更准确的分类。因此，为了使这一系统切实可行，我们必须将该系统扩展到更有效的系统。本研究的目的是将该分类系统发展为一种满足工业需求的分类系统的新技术。1.为了阐明重力的标度律，我们定义了离心力效应参数Ce、重力效应参数Ge和粒子雷诺数Re。并研究了这些参数与Stewartson层中流体和颗粒速度差之间的关系，这是主要的分类流动。通过数值模拟计算了粒子的运动轨迹和粒子的概率密度分布。并研究了Ekman和Stewartson Layers的分类机制。我们用一种类似于圆盘-圆柱形的简单形状来处理新系统，并通过数值模拟来评估它的分类性能。

WE PROPOSE A NEW WET TYPE CENTRIFUGAL CLASSIFICATION SYSTEM TO WHICH A STABLE AND AXISYMMETRIC ALMOST RIGIDLY ROTATING FLOW CAN BE APPLIED. THE CLASSIFICATION SYSTEM HAS DISTINCTIVE FEATURES IN THAT WE CAN ARBITRARY SET THE RATIO OF THE CENTRIFUGAL FORCE TO THE FLUID DRAG ACTING ON PARTICLES AND CAN THEORETICALLY INVESTIGATE THE CLASSIFICATION MECHANISM FROM THE PARTICLE TRAJECTORIES BY NUMERICAL SIMULATION. WE PREVIOUSLY INVESTIGATED RESULTS OF THE CLASSIFICATION PERFORMANCE FOR VARIOUS THROUGH FLOW RATE AND ROTATION RATE, AND CLARIFIED THE DEPENDENCE OF THE SHARPNESS INDEX AND CUT SIZE ON EKMAN AND ROSSBY NUMBERS FOR THE SPHERICAL PARTICLES FROM ONE-MICRON TO SUB MICRON REGIME HAVING TRUE SPECIFIC GRAVITY NEAR ONE. HOWEVER, THE THROUGHPUT IS SMALL FOR THE SYSTEM. INDUSTRIAL NEEDS ALSO DEMAND MORE ACCURATE CLASSIFICATION OF PARTICULATE MATERIALS HAVING VARIOUS SHAPES AND TRUE SPECIFIC GRAVITY MORE THAN TWO. HENCE IN ORDER TO MAKE THIS SYSTEM PRACTICABLE, WE HAVE TO EXTEND THE SYSTEM TO MORE EFFICIENT ONES.THE OBJECTIVE OF THE PRESENT STUDY IS TO DEVELOP THE CLASSIFICATION SYSTEM TO A NEW TECHNIQUE ON THE CLASSIFICATION SYSTEM SATISFYING INDUSTRIAL NEEDS. WE HAVE OBTAINED THE FOLLOWING RESULTS:1. IN ORDER TO CLARIFY A SCALING LAW ON THE GRAVITY FORCE, WE DEFINE CENTRIFUGAL EFFECT PARAMETER Ce, GRAVITATIONAL EFFECT PARAMETER Ge AND PARTICLE REYNOLDS NUMBER Re. AND WE INVESTIGATE THE RELATION BETWEEN THESE PARAMETERS AND THE DIFFERENCE OF FLUID AND PARTICLE VELOCITIES IN THE STEWARTSON LAYER WHICH IS THE MAIN CLASSIFICATION FLOW FIELD.2. WE CALCULATED THE PARTICLE TRAJECTORIES AND THE PROBABILITY DENSITY DISTRIBUTION OF THE PARTICLES BY THE NUMERICAL SIMULATION. AND WE INVESTIGATE THE CLASSIFICATION MECHANISM IN THE EKMAN AND STEWARTSON LAYERS.3. WE TREAT NEW SYSTEM WITH A SIMPLE SHAPE LIKE A DISK-CYLINDER SHAPE AND EVALUATE ITS CLASSIFICATION PERFORMANCE BY NUMERICAL SIMULATION.