流向强迫作用下的液体初始雾化机制及动力学特征

Initial Atomization Mechanism and Dynamic Characteristics of Liquid with Forced Perturbation

关键词:  燃烧室  射流破碎  扰动波  雾化  频率  液滴

Key words:  Combustor  Jet breakup  Disturbing wave  Atomization  Frequency  Droplet

摘要:

使用Volume of fluid（VOF）方法和基于树形数据结构的自适应算法来研究射流雾化的破碎过程以及扰动对射流破碎机理产生的影响。在无扰动情况下，液体射流的头部、液丝和液滴随着射流时间的发展不断发生演变。射流头部先呈现蘑菇状外形，随后液丝生成，并慢慢转变成网兜状，直至断裂形成小液滴。在周期性流向强迫的作用下，射流液柱的表面会形成周期波，其液丝破裂形成液滴的时机与稳定射流情形相比会有所提前，射流形成的头部更趋于扁平，最终生成的液滴数量更多。低中频阶段，随着扰动频率的增大，射流未扰动液柱长度（ L）逐渐缩短，液滴直径的概率密度分布（ PDF）趋于尖锐，液滴平均直径（ SMD）增大。在高频阶段，随着扰动频率的增大， L会随之增大，液滴直径的 PDF分布变得平缓， SMD会减小。

Abstract:

To investigate the breakup process of jet atomization and the effects of disturbance on the jet, the volume of fluid (VOF) method and the adaptive algorithm based on tree data structure are used to simulate the atomization process. The tip, the liquid filaments and the droplets in undisturbed liquid jet change continuously with the evolution of the jet time. First, the tip appears in a mushroom shape, then the liquid filaments appear, and gradually become a thin-net shape. The liquid filaments slowly become small droplets, and the droplets spread upstream around the tip. The perturbation frequency forces on the jet and produces a periodic wave on the surface of the liquid column. Compared with the steady velocity jet, the liquid filaments form droplets earlier, the tip is flatter, and the number of droplets is larger. In the low-middle frequency phase, as the disturbance frequency increases, the non-perturbed length ( L) gradually decreases, probability density function ( PDF) distribution of the droplet diameter tends to be sharp, Sauter mean diameter ( SMD) increases. In the high frequency phase， as the disturbance frequency increases, L gradually increases, PDF of the droplet diameter tends to be smooth and SMD decreases.