剪切稀化流体中微粒子聚集行为研究  

Study on particle aggregation behavior in shear-thinning fluid

作　　者：童松豪 韩戌峰 周福康 许晓飞[1] Songhao TONG;Xufeng HAN;Fukang ZHOU;Xiaofei XU(Research and Design Institute of Fluid and Powder Engineering,Dalian University of Technology,Dalian,Liaoning 116024,China)

机构地区：[1]大连理工大学流体与粉体工程研究设计所,辽宁大连116024

出　　处：《过程工程学报》2022年第6期792-801,共10页The Chinese Journal of Process Engineering

基　　金：国家自然科学基金资助项目(编号:51876030);大学生创新创业训练计划资助项目(编号:20211014110741)。

摘　　要：在化工过程、生物工程等领域中,实现颗粒分离至关重要。通过整合微流控技术、高速显微图像采集技术和数字图像处理技术,探究微粒尺寸、通道流量和液相流变特性对微粒聚集的影响规律。结果表明,在剪切稀化流体羧甲基纤维素钠(CMC)水溶液中,随着通道流量和颗粒粒径增大,微颗粒聚集位置逐渐向剪切速率较高的一侧偏移;随着CMC质量分数增加,聚集位置不断向剪切速率较低的一侧偏移。利用求解的幂律型剪切稀化流体速度和剪切速率方程,结合对微颗粒的受力分析,证明稠度系数越大,聚集位置越偏向剪切速率较低处;剪切稀化特性越强,聚集位置越偏向剪切速率较高处,说明在幂律型剪切稀化流体中的黏度变化是微颗粒发生特殊迁移聚集行为的一个重要原因。In shear-thinning fluid,there is a special rheological behavior that the apparent viscosity decreases with the increase of shear rate.As the viscosity changes during lateral migration,the lift force acting on particles will also change,so the particle migration and aggregation laws in Newtonian fluids are not completely applicable to shear-thinning fluid.Integrating microfluidic technology,high-speed microscopic image acquisition technology and digital image processing technology,combined with the solved velocity and shear rate equations of shear-thinning power-law fluids,the force analysis of particles is completed,and the influences of particle size,channel flow rate,apparent viscosity and shear-thinning characteristics on particle aggregation are investigated.Results indicate that,in the shear-thinning fluid sodium carboxymethyl cellulose(CMC)aqueous solution,with the increase of channel flow rate,the equilibrium position of inertial liftΔF=0 gradually approaches the wall surface,and the migration and aggregation location of particles gradually tends to the side of higher shear rate.This leads to the gradual change of the particle distribution from relatively uniform distribution to aggregation at specific locations.As the particle size increases,the aggregation in the shear flow becomes more and more obvious,and gradually closing to the wall.Combining experimental study and theoretical analysis,it is proved that the greater the consistency coefficient K(represent greater apparent viscosity),the more the aggregation position is towards the low shear rate,and the smaller the power law index n(represent stronger shear thinning characteristic),the more concentrated the position is towards the high shear rate.K increases and n decreases with the increase of CMC mass fraction which leads the aggregation position constantly shifting towards the side with lower shear rate.This shows that the consistency coefficient has a greater influence on the migration and aggregation of particles in shear-thinning power-law flui

关 键 词：剪切流场 剪切稀化流体 微通道 微粒子 颗粒聚集 

分 类 号：TQ021.1[化学工程]