T型微通道内液滴形成过程及长度的实验研究

利用高速摄像机研究截面为400×400 μm的正T型微通道内液-液两相流动特性，离散相（硅油）和连续相（质量分数为0.5%的十二烷基硫酸钠SDS蒸馏水）的体积流量范围分别为1~5、2~110 mL/h. 结果表明，两相流型主要为弹状流和滴状流，前者的形成机理为挤压机理，后者为剪切机理. 液滴的长度随离散相体积流量和离散相与连续相体积流量之比的增大而增大，随连续相的体积流量和毛细数的增大而降低. 液柱长度的变化规律与液滴长度相反. 液滴生成时间随离散相与连续相的体积流量的增大而逐渐降低，剪切机理生成液滴所需时间小于挤压机理. 依据实验结果，采用离散相与连续相体积流量比和连续相的毛细数，总结出无量纲液滴、液柱长度及液滴生成时间的预测关联式.

Experiment study on formation and length of droplets in T-junction microchannels

Flow characteristics of liquid-liquid two-phase flows in T-junction microchannels with 400×400 μm cross-section were experimentally studied using a high-speed camera. Silicon oil and distilled water with 0.5% sodium dodecyl sulfate (SDS) were used as dispersed phase and continuous phase, respectively. Volume flow rates of the disperse phase ranged from 1 to 5 mL/h, while those of the continuous phases ranged from 2 to 110 mL/h. Slug flow and droplet flow patterns were observed in the experimental work. Results show that the formation of dispersed slugs is controlled by the squeezing mechanism, while the shearing mechanism domains the liquid droplet formation process. The length of liquid droplet increases with the increase of volume flow rate of dispersed phase and the volume flow rate ratio of dispersed phase to continuous phase, and decreases with the increase of volume flow rate and capillary number of continuous phase. The change of lengths of liquid column is opposite to that of liquid droplet. The droplet generation time decreases with the increase of volume flow rates of dispersed phase and continuous phase, and the formation time for shearing mechanism is less than that of squeezing mechanism. Based on the experimental results, the volume flow rate ratio of dispersed phase to continuous phase and the capillary number of continuous phase are adopted to develop the predictive correlations of dimensionless liquid droplets, column length and droplet generation time.