三产品旋流分级筛颗粒透筛分级机理研究

The hi-efficient classification of fine particles has become a research focus recently.Applicant created three product cyclone classification screen by combining arched screen with classifying hydrocyclone, which can increase the classification efficiency of coal slurry significantly. But the mechanism of penetrating and regulation has not been identified.In this program, we will combine methods of theoretical analysis，PIV test of prototype experiment, Fluent, coupled CFD numerical simulation based on Fluent-EDEM, starting from particle dynamics analysis, using PIV test results with low concentration to correct calculation model, studying the distributions of physical quantities in the internal swirl field with numerical simulations to get the particle motion laws and the effect of main factors, such as centrifugal intensity and size of screen mesh, etc. on particle penetrating.The functional relationship of penetrating amount, particle size and height of penetrating, centrifugal intensity, size of screen mesh will be established by connecting the pulp parameters of particle penetrating by sampling along the direction of screen height together with simulation results to clarify the penetrating mechanism.Correlation model of penetrating and classification performance, structural parameters, process parameters and physical parameters will be established and the influence degree and order of these parameters will be achieved using the result of numerical simulation with grey system theory. Parameter set for hi-efficient classification will be got and the direction of structural optimization will also be found out.This program has important theory meaning and actual value for the improvement of two-phase flow penetrating theory in swirl field. And it will also provide theoretical basis for optimizing equipment structure to increase classification efficiency and guarantee the stable production.

解决细粒物料高效分级成为近年来的研究热点。申请人把弧形筛分与水力旋流器融合，发明了三产品旋流分级筛，能显著提高煤泥分级效率，但透筛机理及调控机制尚未明确。本项目拟采用理论分析、样机试验PIV测试、Fluent和基于Fluent-EDEM耦合的CFD数值模拟相结合的方法，从颗粒动力学分析入手，用低浓度PIV测试结果修正计算模型，用数值模拟实验研究内部旋流场各物理量分布，获得颗粒运动规律，揭示离心强度、筛缝尺寸等主要因素对透筛影响机制；通过沿筛网高度方向布点采样获得透筛矿浆参数，结合模拟结果建立透筛量、透筛粒度与高度、离心强度、筛缝宽度等的函数关系，揭示透筛机理；对数值模拟实验结果用灰色系统理论建立透筛分级效果与结构参数、工艺参数及物性参数的关联模型；找出高效分级参数集，提出结构优化方向。本项目对完善旋流场两相流透筛理论具有重要理论意义；为优化设备结构进一步提高分级效率，保证稳定生产提供理论与实验依据。

三产品旋流分级筛（TPHS）通过在传统水力旋流器（CH）内增设柱段筛网创新的实现了离心和筛分耦合作用下的（简称“耦合”）颗粒分级。近年来，主要通过实验探索的方式对TPHS进行结构优化、过程调节及性能预测等研究，但对其内部多相流动的认识尚不充分，对其流场特征和颗粒透筛机理的准确描述尚属空白。因此，课题围绕TPHS，从多相流体动力学角度出发，以CFD和DEM理论分析为切入点，在合理仿真理论体系建立的基础上，对耦合流场的多相流动进行数值模拟，在模拟结果与相同条件下的物理样机实验对比验证的基础上，深入研究了设备内耦合流场分布特征和颗粒透筛机理，揭示了流体及颗粒运动规律。主要研究内容和结论包括：.1）借助PIV技术对φ75mmTPHS柱段筛网内耦合流场进行测试，获得了精确的流场信息；.2）以φ75mmTPHS为对象进行耦合流场的几何建模，以VOF和RANS算法进行流动建模，可获得稳定的宏观流动，并进行了有效性验证；.3）借助CFD仿真技术，对耦合流场分布特征进行全面分析：流体沿切向高速给入TPHS后做旋流向下运动，形成筛下流、外旋流、内旋流、透筛流等；与CH相比，耦合流场具有更低切向速度和更高径向速度；耦合流场的静压呈轴对称分布；耦合流场的湍流强度I、湍动能k和湍流耗散率ε值分布类似；流体透筛量和筛下返流量均与入口速度成正比；建立了单一筛缝下流体透筛流量及占比方程，并指出筛网两侧压差是流体透筛的根本原因；进行了流场优化；.4）采用CFD-DEM模拟对耦合流场内的颗粒运动进行研究：与CH不同，颗粒在TPHS内是在离心和筛分共同作用下分级的，可分为入料柱段的预先分层、柱段筛网的耦合分级和锥段区域的离心分级；并且，相同条件下，TPHS比CH具有更好的颗粒分级效果；在颗粒透筛过程中，曳力是主导作用力，虚拟质量力和压力梯度力阻碍颗粒透筛运动，重力可忽略，碰撞作用力随机影响。