气液旋转流场中曲面壁面上液膜破碎行为研究

气液旋叶分离器筒体圆形壁面的液膜在旋转气体剪切和液滴撞击下极易发生破裂，造成液滴二次夹带的现象，导致分离性能急剧下降，是气液旋叶分离器设计的主要挑战之一。目前针对旋转流场中曲面壁面液膜行为的研究匮乏。本项目以在旋转气流与液滴碰撞作用下曲面壁面液膜破碎行为为对象开展研究，构建典型旋转通道可视化实验模型，采用激光多普勒测速、可视化高速摄像和平行电导探针测量技术，获得旋转气流和液滴作用下曲面壁面液膜凹陷、液滴反弹、液滴延展、液滴飞溅等典型现象及分区边界，遴选恰当的湍流模型和气液界面捕捉模型对典型现象展开CFD数值模拟，获得典型现象详尽的速度场和相分布。进一步开展液膜理论动力学分析，推导表征曲面液膜稳定性和液膜破碎的无量纲准则数，建立典型现象分区的无量纲准则边界和二次液滴粒径、夹带量的无量纲关系式。本研究揭示旋转流场中曲面壁面液膜破碎液滴夹带的机理，为旋叶分离器内气液分离分析提供理论基础。

The liquid film on the circular wall of gas-liquid vane-type separators is unstable due to the shear effect of the swirling gas and impact of the liquid droplets. Droplet entrainment happens, which results in significant decrease of separation efficiency and is challenging for the designers. Reports on the stability and broken-up behavior of the liquid film on the curved wall of channels whose main steam is swirling, are rare. Therefore, in present study, the behaviors of the liquid film on curved wall are investigated. A transparent typical swirling channels representing the channels inside separator is developed with air-water as the working fluid. The velocity of air inside the test section are measured by Laser Doppler Velocimetry (LDV), while the behavior of the liquid film on the curved wall are recorded by high speed camera. Meanwhile, the thickness of the film on the curved wall is measured by two-parallel electronic conductance probes. The typical dynamic features of the liquid film and droplets are obtained, for example, film cavitation, droplet bouncing, droplet spreading and droplet splashing. The region for every typical features are specified. By using proper turbulent model and liquid-gas interface capturing method, numerical simulation for typical dynamic behavior of the liquid film on curved wall, swirling gas stream and droplets are carried out. Thereby, detailed velocity and phase distribution are obtained and analyzed. Moreover, the forces on the liquid film on curved wall and droplets are analyzed. The key non-dimensional parameters and inception criterion for the stability and broken-up behavior of the film on curved wall are deducted. The non-dimensional inception criterion of droplet entrainment is developed with the assistance of the force balance analysis. The size of the new born droplets will be recorded by high speed camera. The size and the amount of new born droplets will be correlated to non-dimensional parameters. These correlations with the droplet entrainment criterion could be used for developing models for predicting the film thickness and separation performance of the swirl-vane separator. Through these work, the mechanism of film broken-up and droplet entrainment for films on curved wall with a swirling main stream is obtained and the correlations could be used for developing the models for the analysis of the performance of gas-liquid vane-type separator.