三维孔喉结构微通道内液滴的破裂行为研究

doi:10.11949/0438-1157.20190652

摘要/Abstract

摘要：

利用高速摄像仪研究了三维孔喉结构微通道内液滴的破裂行为。采用不同黏度的甘油-水溶液作为分散相，含4%（质量）表面活性剂（Span 20）的矿物油作为连续相。液滴通过孔喉结构后，观察到了三种流型：球形破裂、非球形破裂和不破裂。除极低连续相毛细数的情形外，分散相黏度和两相流量的增加不利于液滴破裂，液滴的破裂位置均接近于喉道出口。研究了液滴的球形破裂，结果表明，球形破裂中子液滴平均尺寸随分散相黏度和连续相流量的增加而降低，且与两相总毛细数呈幂律关系，模型预测值与实验结果吻合良好。

关键词: 三维孔喉结构, 液滴, 破裂, 微通道, 两相流, 微流体学

Abstract:

The flow behaviors of droplets breakup in the three-dimensional (3-D) pore-throat microchannel were investigated using a high-speed camera. A glycerin-water solution of different viscosity was used as a dispersed phase, and a mineral oil containing 4%(mass) of a surfactant (Span 20) was used as a continuous phase. Three flow patterns were observed when the droplets flowed out the pore-throat structure: spherical breakup, non-spherical breakup and non-breakup. Except extremely low capillary number of continuous phase, the increase of the viscosity of the dispersed phase or two-phase flow rates is not conducive to droplet breakup. Generally, the breakup position of the droplets approaches to the throat outlet. The spherical breakup of the droplets was further studied, the results indicate that the average daughter droplets size decreases with the increase of the viscosity of the dispersed phase and the flow rate of the continuous phase. The variation of the average size of daughter droplets with capillary number could be scaled with a power-law relationship, and the predicted result agrees well with the experimental data.

Key words: 3-D pore-throat structure, droplet, breakup, microchannel, two-phase flow, microfluidics

中图分类号:

TQ 021.1

周灏, 朱春英, 付涛涛, 高习群, 马友光. 三维孔喉结构微通道内液滴的破裂行为研究[J]. 化工学报, 2019, 70(10): 3924-3931.

Hao ZHOU, Chunying ZHU, Taotao FU, Xiqun GAO, Youguang MA. Study on droplet breakup behaviors in 3-D pore-throat microchannel[J]. CIESC Journal, 2019, 70(10): 3924-3931.

图/表 9

图1 实验装置图 1, 2—微型泵; 3—微芯片; 4—光源; 5—计算机; 6—高速摄影机; 7—显微镜; 8—收集器

Fig.1 Schematic diagram of experimental setup

图2 三维孔喉结构微通道

Fig.2 3-D pore-throat microchannel

表1 实验中所用流体的物理性质

Table 1 Physical properties of liquids used in experiment

Solution	Density, ρ/(kg·m^-3)	Viscosity, μ/(mPa·s)	Interface tension, σ/(mN·m^-1)
4% Span20/mineral oil	852.9	22.23
10% glycerol-water solution	1020.5	1.13	3.42
20% glycerol-water solution	1045.0	1.51	2.04
30% glycerol-water solution	1070.5	2.10	1.80

图3 三维孔喉结构内液滴的破裂流型

Fig.3 Droplet behaviors when passing through 3-D pore-throat microchannel

图4 液滴破裂过程相关参数定义

Fig.4 Definitions of parameters to characterize droplet breakup process

图5 不同浓度液滴在矿物油中经过三维孔结构微通道后的流型图

Fig.5 Diagrams for droplet behaviors in 3-D pore-throat microchannel

图6 子液滴平均尺寸随连续相流量变化趋势 (插图：平均尺寸随毛细数的变化)

Fig.6 Changing trend of daughter droplet sizes with flow rate of continuous phase(insert: L/W ~ Ca)

图7 液滴通过喉道时头部与尾部的演化

Fig.7 Representative trajectories for droplet approaching throat convergence(Q c = 2 ml·h-1, Q d = 0.4 ml·h-1. Dispersed phase: 10% gly-water)

图8 子液滴尺寸的预测值与实验值比较

Fig.8 Comparison between predicted values and experimental data of daughter droplet sizes

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