激波冲击下液滴的雾化特性研究

Atomization characteristics of droplet under shock wave

液滴与激波之间的相互作用存在于旋转爆轰发动机、推进技术和云雾爆轰等应用中.本文目的是探究液滴与激波相互作用时其行为和演变特征,建立可靠的数值计算模型并分析液滴的变形和雾化机理.利用激波管生成不同马赫数的激波冲击液滴并采用高速摄影相机拍摄液滴的演变特征.基于VOF模型和自适应网格技术建立了数值计算模型,将数值计算的结果与实验结果对比验证了数值计算模型的正确性.实验结果表明,在激波作用下,液滴先后经历了变形阶段和雾化阶段.马赫数的增加会显著加快液滴变形和雾化的过程.数值计算结果表明,激波后的诱导气流在液滴表面存在边界层分离现象.边界层分离导致了液滴表面压力分布不均,致使液滴变形和压缩.液滴剥离则是液滴侧面的气流和背风面的驻涡流动对液滴表面的剪切作用共同造成的.

The interaction between droplets and shocks wave exists in a rotary detonation engine,propulsion technology,fuel air explosion and other applications.The purpose of this study is to (1) investigate the behavior and evolution characteristics of droplets when they interact with shock waves. (2) establish a reliable numerical model and analyze the droplet deformation and atomization mechanism.In this paper,shock waves with different Mach numbers were generated by a shock tube and the evolution characteristics of the droplets were captured by a high-speed camera.A numerical model was established based on VOF method and adaptive mesh technique.The numerical results were compared with the experimental results to verify the correctness of the numerical model.The experimental results showed that the droplet had undergone deformation stage and atomization stage under the action of a shock wave.The increase of Mach number would significantly accelerate the droplet deformation and atomization process.The numerical results showed that the induced air flow after the shock wave contained boundary layer separation on the droplet surface.Boundary layer separation resulted in an uneven distribution of pressure on the droplet surface,which caused droplet deformation and compression.Droplet stripping was caused by the shear action on the droplet surface caused by the airflow on the side of the droplet and the standing vortex flow on the lee side.