Abstract:

The non-blocking rupture process of droplets in asymmetric T-type microchannels was studied using a high speed camera. The glycerol-water solution and mineral oil with 4%(mass) surfactant Span-20 were introduced as the dispersed phase and continuous phase, respectively. The breakup process of droplet could be divided into three stages:entering stage, deformation stage and breakup stage. The breakup stage could be further divided into two sub-stages:fast breakup stage and thread breakup stage. The effects of liquid superficial velocity, the dimensionless length of the droplet and the viscosity ratio between dispersed phase and continuous phase on the breakup stage were investigated. The results indicated that the fast breakup stage was a self-similar process, the evolution of the dimensionless minimum width of the droplet neck with the dimensionless remaining time could be scaled by a power-law relationship, and the value of power law index was about 1.35. In the thread breakup stage, the dimensionless minimum width of the droplet neck was linear with the dimensionless remaining time. The slope of line increased with the increase of liquid superficial velocity and the dimensionless droplet length, and reduced with the increase of the viscosity ratio between dispersed phase and continuous phase.

Key words: microchannels, droplet, breakup, dynamics, two-phase flow

摘要：

利用高速摄像机研究了不对称T型微通道内液滴的无阻塞破裂过程。以甘油-水溶液为分散相，含4%（质量分数）表面活性剂Span-20的矿物油为连续相。液滴的无阻塞破裂过程可分为三个阶段：进入阶段、形变阶段和破裂阶段。其中破裂阶段又可分为快速破裂阶段和细丝破裂阶段两个子阶段。考察了表观流速、无量纲液滴长度和两相黏度比对破裂阶段的影响。结果表明：快速破裂阶段是一个自相似过程，无量纲颈部最小宽度与无量纲剩余时间呈幂律关系，幂律指数约为1.35。细丝破裂阶段无量纲最小颈部宽度与无量纲剩余时间呈线性关系。斜率随着表观速度和无量纲液滴长度的增大而增大，随两相黏度比的增大而减小。

关键词: 微通道, 液滴, 破裂, 动力学, 两相流