液-液分散雾化形成液滴的模式

Evolution of Drop Formation Form in Another Liquid during Dispersive Liquid Atomization

基于图像采集与处理方法实验研究了水喷入非相溶油中的液液分散雾化过程.结果表明,通过改变操作条件使水破碎形成3种水滴模式:滴流、层流射流和湍流射流,揭示了其演变规律及其形成机理,获得了分散液体破碎强度、射流长度脉动和液滴粒径分布参数随雷诺数Re、韦伯数We的变化规律.随Re和We增加,分散液体破碎强度持续增强,在Re=467,We=8.6时液滴形成模式由滴流向层流射流发展,在Re=3169,We=241时演变为湍流射流,且液滴的粒径均匀性和最小平均粒径均出现在湍流射流模式下;在滴流模式下,液滴的形成、长大与脱离喷嘴均由液滴受力的平衡机制控制;在层流射流模式下,射流柱破碎形成液滴主要由两相界面的表面波扰动引起,且射流长度的脉动具有随机和非周期的特点;在湍流射流模式下,射流柱表面出现拟序涡结构,其在射流起始段失稳,在射流扩散段大量形成较小粒径的液滴.

The evolution process of drop formation in another immiscible oil during dispersive liquid atomization is experimentally studied by image gathering and processing. The results show that there exist three typical dispersive liquid break-up forms related to drop formation, dripping, laminar jet and turbulent motion jet, with three different mechanisms. The variation of liquid-liquid atomization forms, jet break-up intensity, jet length fluctuation and drop size distribution with liquid Reynolds number （Re） and Weber number （We） show that jet break-up intensity is strengthened continually with increasing of Re and We, dispersive liquid break-up form is transformed from the dripping to laminar jet at Re=467 and We=8.6, and becomes finally the turbulent motion jet at Re=-3 169 and We=241, and the best spreading parameters of drop size distribution, the uniformity and least mean value of drops size, always appear in turbulent jetting form. Under the dripping form, emerging, developing and breaking away of liquid drops from the tip of nozzle are dominated by balanced-force mechanism. And under the laminar jetting form, the mechanism of dispersive liquid break-up is caused by interphase surface wave motion, and jet length fluctuation is characterized by random and no periodic ways. However, under the turbulent jetting form, coherent structure appears and acts on jet instability at the initial section of the jet, and a large number of finer drops form in the diffusion section.