挡板对陶瓷干法造粒气-固两相流混合过程的影响
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摘要
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。
In order to study the influence of baffles in the mixing process of ceramic dry granulation gassolid 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/cm3,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.
In order to study the influence of baffles in the mixing process of ceramic dry granulation gassolid 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/cm3,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.
引文
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[3]吴南星,廖达海,肖志锋.陶瓷干法造粒机的数值模拟及其优化设计[J].陶瓷学报,2014,35(1):82-87.
[4]黄剑锋,张博烨,汪庆刚,等.一种建筑陶瓷坯料干法造粒装置及其方法:CN103566818A[P]. 2014.
[5]王斌,郑伍魁,李辉,等.我国陶瓷墙地砖制粉工艺的进展[J].硅酸盐通报,2015,34(5):1312-1319.
[6]许涛,过学迅,张杰山,等.基于Fluent的液力变矩器内流场数值计算[J].农业机械学报,2007(12):152-155.
[7]周国忠,王英琛,施力田.用CFD研究搅拌槽内的混合过程[J].化工学报,2003(7):886-890.
[8]郭聪聪,赵恒文,许卓,等.搅拌槽内挡板对搅拌效果的数值模拟[J].给水排水,2011,47(S1):199-202.
[9]许卓,赵恒文,郑建坤.立式搅拌槽中挡板结构对搅拌能耗影响的数值模拟[J].水电能源科学,2013,31(5):162-165+197.
[10]钟天铖,汤文成,刘碧茜.推进式搅拌器固液混合的计算流体力学模拟[J].东南大学学报(自然科学版),2016,46(4):713-719.
[11] Xu S A,Feng L F. Effect of baffle in mixing of floating-particle in stirred tanks[J]. Synthetic Industry,1999,22(4):246-254.
[12] Luo J,Lu J M,Shen R C,et al. Effects of baffle on the mixing effectiveness of a crossflow jet mixer[J]. Chemical Reaction Engineering and Technology,2006,22(3):199-205.
[13] Pfleger D,Gomes S,Gilbert N,et al. Hydrodynamic simulations of laboratory scale bubble columns fundamental studies of the Eulerian-Eulerian modelling approach[J]. Chemical Engineering Science,1999,54(21):5091-5099.