Abstract:

The preparation of microbubbles by microfluidic technology has attracted much attention due to its controllable process and wide operating range. In this work, a step T-junction microchannel was chosen as the device for the microbubble generation to study the bubble swarm self-assembly behavior and its flow characteristics. Effects of the liquid volumetric flow rate, liquid viscosity, gas injection pressure, and channel size on the bubble swarm were investigated. The results show that ordered bubble swarm (bubble swarm crystals) can be formed only when the gas phase content in the channel is greater than the liquid phase content, and the bubble swarm crystals can self-assemble into structures with different numbers of rows along the channel width or depth direction in the confined space. Besides, the effects of different operating parameters on the flow behavior of the bubble swarm crystal were explored. The variation rules of the flow velocity of the bubble swarm crystal with the liquid-phase volumetric flow rate are the same as the rules of the gas-liquid two-phase volumetric flow rate. Finally, the strategies to improve the flow ideality of the system are proposed, and a dimensionless model for the prediction of the flow ideality of the bubble swarm crystal is also developed.

Key words: microchannels, gas-liquid flow, bubble, crystal, hydrodynamics

摘要：

微流控技术制备微气泡因其过程可控、操作范围宽等特性而备受关注。选择阶梯式T型微通道作为微气泡生成的设备，利用高速摄像机研究了高气相含量下气泡群的自组装行为和流动特性，探索了液相体积流量、液相黏度、气相输入压力和通道宽度等因素对气泡群的影响规律。结果表明，只有当通道内的气相含量大于液相含量时才能形成有序的气泡群(气泡群晶体)，且气泡群晶体在受限空间内能够沿着通道宽度或深度方向自组装成不同行数的结构。此外，系统研究了不同操作参数对气泡群晶体运动速度的影响规律。气泡群晶体运动速度随着液相体积流量变化的规律与气液两相的总体积流量变化规律一致。最后，提出了提升气液体系流动理想性的策略，并构建了预测气泡群晶体流动理想性的无量纲数学模型。

关键词: 微通道, 气液两相流, 气泡, 晶体, 流动特性