Abstract:

In this work, visualization experiments were carried out in serpentine microchannels with Y-type microfluidic junction and small curvature using a high-speed camera. Visible rectangular microchannels with the equivalent diameter of the 177.8 μm were fabricated using transparent glass and polydimethylsiloxane (PDMS). Air and deionized water were well mixed in the Y-type mixer. First, gas and liquid were injected into inlets 1 and 2, respectively. And then, the order would be reversed. Flow characteristics of these two different mixing modes were compared. The main flow patterns such as slug flow, wavy stratified flow and dispersed flow were observed. In this regard, the shape and length of slug, thickness of liquid film and share of liquid droplets entrained by gas phase were investigated in succession, and a new correlation to predict droplets content was proposed based on the measured data. In addition, the arc at the corner can induce slug flow for these two different ways of mixing. Both of them were experiencing tension and fracture processes. The difference was that the latter would like to carry out expansion firstly due to the obstruction by the liquid. The gas-liquid mixture in different ways could have some impact on the flow of each phase and the distribution of two phases near the wall or in the bends was also different.

Key words: microchannels, gas-liquid flow, flow patterns, phase distribution, film, share of entrained liquid droplets

摘要：

以空气、去离子水为实验工质,在θ=50°的Y型混合器内充分混合,利用高速摄像仪对当量直径177.8 μm的小曲率蛇形微通道进行可视化实验,对比了两种气液混合方式(上气下液型、上液下气型)下的流动特性。实验发现的主要流型有弹状流、波状分层流、弥散流等,对此分别研究了气弹的形状和长度、液膜厚度以及气流携带液滴的份额,并提出新的预测液滴含量的关联式。此外,针对这两种不同的混合方式,在弯道处发现圆弧可以诱导产生弹状流,二者均经历拉伸和断裂过程,区别在于后者在拉伸之前,先要进行膨胀。不同的气液混合方式对各相的流动会产生一定的影响,两相流体在通道壁面附近以及弯道处的分布也有所区别。

关键词: 微通道, 气液两相流, 流型, 相分布, 液膜, 液滴份额