液-液循环流化床液滴形成特性研究

Drop Formation Characteristic of Liquid-liquid Circulating Fluidized Bed

基于图像采集与处理方法对液-液循环流化床液滴形成特性进行了实验研究,提出了形成液滴的3种液-液雾化方式,考察了液-液雾化方式与射流长度脉动、液滴粒径分布的相关性,获得了液-液雾化方式的转变规律以及雾化强度、射流长度脉动和液滴粒径分布基于相对雷诺数的变化规律。结果表明,雾化过程与相对雷诺数密切相关,随着相对雷诺数的增加,雾化强度持续增强,液-液雾化方式由滴流型向层流射流型转变,最后发展为湍流射流型;在整个相对雷诺数实验范围内,射流长度的脉动表现出随机和非周期的特点,其标准方差与平均值的变化规律基本一致,在相对雷诺数为1.3×104时达到最大值;液滴的粒径分布参数一直增大到湍流射流型雾化阶段,在相对雷诺数为2.5×104时,液滴的粒径均匀性最好,而液滴平均粒径总体上随相对雷诺数的增大不断减小,形成液滴的最小平均粒径发生在湍流射流型雾化阶段。

Drop formation characteristic of liquid-liquid circulating fluidized bed（LLCFB） were experimentally studied by means of image gathering and processing.Three typical liquid-liquid atomization forms related to drop formation were defined.The relativity was investigated between liquid-liquid atomization forms and jet length fluctuation or drop size distribution,and the change rules of liquid-liquid atomization forms,jet break-up intensity,jet length fluctuation and drop size distribution were obtained with the relative Reynolds number（Rer） between the two phases.The results showed that the course of drops formation rested seriously with Rer.Along with increasing Rer,jet break-up intensity was strengthened continually and liquid-liquid atomization formed by trickling to the laminar jet transformation,developed finally for turbulent motion jet.Jet length fluctuation was characterized by random and no periodic.The overall change tread of standard derivation was consistent with average jet length each other with Rer,and their maximum happened at 1.3×104.Furthermore,spread parameter of drop size distribution increased to the stage of turbulent motion jet atomization and the uniformity appeared at 2.5×104,but the average diameter of drops always decreased with increasing Rer and its maximum at the stage of turbulent motion jet atomization.