电场作用下液滴的变形及库仑分裂模式

doi:10.16085/j.issn.1000-6613.2020-2150

摘要/Abstract

摘要：

基于高速成像技术，本文对电场作用下甲醇液滴的显微形貌特征进行了可视化研究，精确捕捉了两相流体系中不同生长阶段的荷电液滴基于时间分辨特性的变形及库仑分裂演变行为，得到不同工况下荷电液滴的变形分裂过程及行为演化细节。基于液滴所受库仑力和介电泳力与周围流域的耦合作用，揭示了电场作用下不同生长阶段的液滴库仑分裂形成机理。结果表明，电场强度和液滴粒径是决定液滴变形及库仑分裂模式的主要因素，荷电液滴的变形及库仑分裂模式可以分为推压变形、顶部破碎、顶部-边端破碎、伞状破碎。结合量纲为1参数对液滴的变形及破碎特征进行了定量分析，随着电场强度的增大及液滴粒径的减小，液滴变形及顶部破碎的程度更加剧烈，液滴临界伞状破碎长度减小。

关键词: 甲醇, 荷电液滴, 成像, 变形, 库仑分裂, 模式相图

Abstract:

A visual study of the microscopic morphological characteristics of methanol droplets under the action of an electric field was carried out based on high-speed tomography technology. The time-resolved deformation and the Coulomb splitting evolution behavior of charged droplets at different growth stages in a two-phase flow system were accurately captured. The details of the deformation and splitting process as well as behavior evolution of the charged droplets under different working conditions were achieved. Considering the coupled effect of the Coulomb force as well as dielectrophoretic force and the surrounding flow regimes on the droplet, the formation mechanism of the Coulomb split of the droplet at different growth stages in the presence of an electric field was revealed. The results showed that the electric field strength and the droplet size were the main factors that determine droplet deformation and the Coulomb splitting mode. The deformation and Coulomb splitting mode of charged droplets could be divided into pushed deformation, top breakup, top-sided breakup, and umbrella-shaped breakup. Combining the dimensionless parameters to quantitatively analyze the deformation and breakup characteristics of the droplet, the degree of droplet deformation and top breakup became more severe. The critical umbrella-shaped breakup length of the droplet decreased with the increase of the electric field intensity and the decrease of the droplet size.

Key words: methanol, charged droplet, tomography, deformation, Coulomb splitting, pattern phase diagram

中图分类号:

TK018

王军锋, 范志恒, 王东保, 陆帅全. 电场作用下液滴的变形及库仑分裂模式[J]. 化工进展, 2021, 40(10): 5451-5458.

WANG Junfeng, FAN Zhiheng, WANG Dongbao, LU Shuaiquan. Deformation and Coulomb splitting mode of droplets under electric field[J]. Chemical Industry and Engineering Progress, 2021, 40(10): 5451-5458.

图/表 10

图1 荷电液滴显微高速摄像试验系统

表1 试验中所用介质的物性参数

原料

表面张力

/N·m^-1

动力黏度

/mPa?s

相对

介电常数

电导率

/S·m^-1

密度

/kg·m^-3

界面张力

/N·m^-1

图2 不同模式下液滴变形及分裂的时序演化过程

图3 液滴所受电场力

图4 同一电场强度、不同生长阶段液滴的变形

图5 同一生长阶段、不同电场强度液滴的变形

图6 同一电场强度、不同生长阶段液滴的顶部破碎

图7 同一生长阶段、不同电场强度液滴的顶部破碎

图8 液滴的临界伞状破碎长度

图9 液滴变形及库仑分裂模式相图

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