同轴微通道内管结构对液滴生成的影响规律研究

doi:10.11949/0438-1157.20231245

摘要/Abstract

摘要：

研究了同轴微通道内水-硅油体系的液滴生成过程。在不同的连续毛细数Ca_c和分散相Weber数We_d下，观察到滴出流和喷射流两种不同的流型。实验考察了两相流量、黏度和内管结构对液滴尺寸和液滴生成频率的影响。结果表明液滴尺寸随着分散相流量增加而增大，而随着连续相流量和黏度的增加而降低。此外，随着We_d的增加，流型会从滴出流过渡到喷射流，而更大尺寸的内管会更早过渡到喷射流，从而得到更大的液滴尺寸。对于液滴生成频率，其随Ca_c和We_d的增加均呈现先快速增加后变缓的趋势。当内管通道尺寸基本相同时，不同结构的内管通道在固定Ca_c时其液滴生成频率相差不大，且随着通道尺寸的减小，液滴生成频率逐渐增加。基于实验结果，建立了液滴尺寸预测模型，预测值与实验值吻合较好。

关键词: 微通道, 两相流, 内管结构, 液滴生成, 流域

Abstract:

The droplet generation process of the water-silicone oil system in the coaxial microchannel was studied. Under different continuous capillary number Ca_c and dispersed phase Weber number We_d, two different flow patterns, dripping flow and jet flow, were observed. Experiments examined the effects of two-phase flow, viscosity, and inner tube structure on droplet size and droplet generation frequency. The results showed that droplet size increased with the increase of dispersed phase flow rate and decrease of flow rate and viscosity of continuous phase. Additionally, with the increase of We_d, jetting occurrence was found to be easier in relatively larger capillary, which in turn generated larger droplets. The generation frequency of droplet increased fast firstly then slow down to a plateau with the increasing of Ca_cand We_d. When the hydraulic diameters of inner channel were almost same, the deviation in the generation frequency of droplet obtained from different geometries of inner channel was small at fixed Ca_c. And the generation frequency of droplet increased with the decrease in the hydraulic diameters of inner channel. Based on the obtained results, an empirical correlation was proposed to predict the droplet size with good prediction performance.

Key words: microchannels, two-phase flow, inner channel geometry, droplet formation, flow regimes

中图分类号:

TQ 028.8

宋仕容, 刘宏臣, 米晓天, 许超, 杨梅, 尧超群. 同轴微通道内管结构对液滴生成的影响规律研究[J]. 化工学报, 2024, 75(2): 566-574.

Shirong SONG, Hongchen LIU, Xiaotian MI, Chao XU, Mei YANG, Chaoqun YAO. Experimental investigation of droplet formation in coaxial microchannels with different geometries of inner channel[J]. CIESC Journal, 2024, 75(2): 566-574.

图/表 10

图1 同轴微通道结构示意图及实验装置流程图

Fig.1 Schematic representation of the coflowing microchannel device and sketch of the experimental setup

表1 实验中玻璃毛细管的结构和尺寸

Table 1 Geometries and dimensions of glass capillaries used in the experiment

序号	结构	外径/mm	内径/mm
R-0.3	圆形	1.0	0.3
R-0.4		1.0	0.4
R-0.6		1.0	0.6
S-0.2	方形	1.0×1.0	0.2×0.2
S-0.35		0.9×0.9	0.35×0.35
S-0.6		1.0×1.0	0.6×0.6
S-0.7		0.9×0.9	0.7×0.7
T-0.35	等边三角形	0.75	0.35

图2 同轴微通道内不同内管结构的液液两相流型

Fig.2 Typical flow patterns of droplet formation in the coflowing microchannel with different inner geometries (Qc=1 ml/min)

图3 以Cac和Wed表示的两相流型图实心点—滴出流；空心点—喷射流

Fig.3 Diagram of the two-phase flow regime characterized by Cac and Wedsolid dot—dripping flow; hollow dot—jetting flow

图4 连续相和分散相流量对液滴尺寸影响

Fig.4 Effect of flow rates of continuous and dispersed phase on the droplet size（R-0.6, μc=100 mPa·s）

图5 连续相黏度对液滴尺寸影响

Fig.5 Effect of viscosity of continuous phase on the droplet size as a function of Cad and Qc and Cac

图6 内管尺寸对液滴尺寸影响

Fig.6 Effect of inner channel hydraulic diameter on the droplet size as a function of Cac and Wed

图7 内管形状对液滴尺寸影响

Fig.7 Effect of inner channel shape on the droplet size as a function of Cac anb Wed

图8 实验结果测量的dp/di值与预测值的比较

Fig.8 Comparison of the experimental dp/di with the calculated value

图9 内管结构对液滴生成频率影响

Fig.9 Effect of inner channel geometry on the generation frequency of droplet as a function of Cac and Wed

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