基于可视化和图像处理的气液螺旋两相流流型研究

Characteristics of Swirling Gas-liquid Flow Induced by a Vane-type Swirler

为了揭示螺旋涡流对气液两相流型特征及相分布的作用机理,本文结合高速摄影方法和数字图像处理技术对竖直管内旋叶式起旋器作用下的气液两相流开展了实验研究。结果表明:起旋器出口流型包括螺旋气柱流、弹状流、搅拌流、螺旋间歇流、螺旋环状流和螺旋丝带流。其中,螺旋气柱流、螺旋间歇流、螺旋环状流和螺旋丝带流是四种典型螺旋流型,液相均以液膜形式均贴管壁流动,气相在管道中心流动。螺旋气柱流中厚液膜随时间波动较小,螺旋间歇流中液膜厚度随时间周期性波动,螺旋环状流中薄液膜随时间波动幅度相比螺旋气柱流增强。基于流型及相分布特征,提出了螺旋流型图并与光滑管Hewitt-Roberts流型图对比,发现起旋器作用下弹状流、搅拌流流动区域明显缩小,被限制在低气液流速区;螺旋涡流不仅促进了弹状-搅拌流的转变,也使得螺旋环状流相比光滑管环状流能够在更低的气速条件下形成。

In this work, based on the high-speed camera method, air-water experiments are carried out to study the characteristics of swirling gas-liquid flow induced by a vane-type swirler in a vertical pipe. According to the visual observation, four typical swirling flow patterns including swirling gas column flow, swirling intermittent flow, swirling annular flow and swirling ribbon flow are recognized at the swirler outlet. However, the non-swirling flow patterns such as slug and churn flow are also observed. Since all the swirling flows behave like an annular-type flow, i.e. the liquid phase flows adjacent to the pipe wall and the gas phase flows in the center of the pipe, the liquid film thickness of swirling flows is measured with image processing technique and statistically analyzed. On this basis,a swirling flow regime map is proposed and compared with the non-swirling flow map of Hewitt &Roberts. The results indicate that the swirling motion not only narrows the flow region of slug and churn flow, but also promotes the slug-churn and churn-annular transition.