挡板对陶瓷干法造粒气-固两相流混合过程的影响

为探究陶瓷干法造粒气-固两相流混合过程挡板对粉体混合效果影响,构建欧拉气-固两相流模型分析空气与粉体相互作用,简化造粒区域并建立粉体混合过程三维物理模型,采用滑移网格法、多重参考系法模拟造粒室旋转运动,修正RNG离散模型分析湍流状态。根据径向及轴向粉体体积分数分布、速度场探究不同挡板对粉体混合影响,并改进挡板位置和结构以提高粉体混合程度。结果表明:当造粒室内分别含矩形壁挡板、矩形底挡板、半圆形壁挡板时,粉体轴向体积分数高于0. 27的区域分别占总面积29%、40%、37%;粉体径向体积分数高于0. 29的区域分别占总面积24%、15%、33%;粉体轴向平均速度分别为0. 4 m/s、0. 5 m/s、0. 6 m/s;对不同粒径的粉体进行密度测定实验,当造粒室内含矩形壁挡板时,粉体密度基本为1. 9 g/cm3,一致性较好。该结果显示矩形壁挡板造粒室内的粉体堆积程度最低,粉体混合性能最优,该模型及结果能够有助于提高对陶瓷干法造粒室气固两相流流场的理解,并对造粒室挡板设计优化提供一定理论指导。

Effect of Baffles on the Ceramic Dry Granulation Gas-Solid Two-phase Flow Mixing Process

In order to study the influence of baffles in the mixing process of ceramic dry granulation gas-solid two-phase flow on the powders mixing,established Euler gas-solid two-phase flow model to analysed air-powder interaction,simplified the granulation area and establishing a three-dimensional physical model of the powder mixing process,used sliding mesh method and multiple reference frame method to simulate the rotating motion of granulation chamber,corrected RNG discrete model to analyze turbulent state.Based on radial and axial powder volume fraction distribution and velocity field,the effects of different baffles on powder mixing were explored,changed baffle positions and structure to increase powder mixing.The results show:when the granulation chamber contains a rectangular wall baffle,a rectangular bottom baffle,a semi-circular wall baffle,the powder axial volume fraction higher than 0.27 accounts for 29%,40%,37%in the total area;the powder radial volume fraction higher than 0.29 accounts for 24%,15%,33%in the total area;the powder axial average speed is 0.4 m/s,0.5 m/s,0.6 m/s respectively;density measurement experiments on powders of different particle sizes show when the granulation chamber contains a rectangular wall baffle,the powder density is basically 1.9 g/cm^3,the uniformity is good.The results show that the powder accumulation in the rectangular wall baffle granulation chamber is the lowest and the powder mixing performance is optimal.The model and results can help improve the understanding of gas-solid two-phase flow field in ceramic dry granulation chamber and provide theoretical guidance for optimization of granulator baffle design.