Instability Analysis of Taylor Bubble in Horizontal Gas-Liquid Intermittent Flows by S-PLIF Method

Horizontal gas-liquid two-phase flows are widely encountered in petroleum, nuclear reactors and other important industrial processes. Intermittent flow is one of the most common flow patterns in horizontal gas-liquid two-phase flows, which is characterized by the alternating movement of film regions and liquid regions. There are elongated Taylor bubbles in the film regions and complicated interactions between the liquid film and the Taylor bubble. Accurate interface detection of intermittent flows is extremely vital for studying the mass transfer and heat between phases and revealing the mechanism of flow pattern conversion. A structured planar laser-induced fluorescence (S-PLIF) detection system was designed to accurately identify the gas-liquid interface in this paper, composing of a high-speed camera, a laser generator, a ronchi ruling plate and a visualization box. Then, a dynamic experiment of horizontal gas-liquid two-phase flows was conducted to obtain original S-PLIF images. According to the deflection phenomenon of alternating light and dark stripes at the gas-liquid interface, an image processing method was proposed to extract the gas-liquid interface in different flow patterns. In addition, the evolution characteristics of liquid film thickness and Taylor bubble length were investigated. Finally, the instability of Taylor bubble was further studied by introducing high-order Markov entropy.