文丘里式气泡发生器内气泡破碎机制分析

作为一种高效、安全的气泡发生装置，文丘里式气泡发生器在工业、化工等过程有广泛的应用，但对其内部气泡破碎过程和作用机制相关研究较少。前期研究发现，较大气泡进入文丘里管扩张段后会发生迅速减速，并对气泡碎化过程产生极大影响。基于大涡模拟方法，对文丘里式气泡发生器内的流动过程进行了数值模拟，发现在扩张段近壁面存在明显的涡流区，涡流区前端与上游来流发生强烈的碰撞，造成进入此区域的流体发生迅速减速，使得涡流区与主流交汇区附近静压急速增大；当此区域存在运动的气泡时，激增的压力梯度力以及附加质量力导致气泡运动速度迅速减小，并与周边流体形成了更强的相互作用；高流速条件下，会使气泡发生严重变形、甚至破碎。

Bubble breakup mechanism in Venturi-type bubble generator

As efficient and safe equipment, Venturi-type bubble generators have wide application in general and chemical industry. There are few researches about process and mechanism of bubble breakup inside generators. Previous studies showed that large bubbles were rapidly decelerated after entered diverging section of a Venturi-type bubble generator, which was probably critical to bubble breakup process. In this paper, large-eddy simulation on flow in a Venturi-type bubble generator showed existence of an obvious vortex region near wall of the diverging section. A strong collision between front of the vortex region and fluid from upstream fast decelerated fluid upon entering the region and significantly increased static pressure near confluence of vortex region and mainstream. When a bubble was moving through the region, it would be greatly decelerated by a surge in pressure gradient force and mass-added force, which intensified interaction with ambient fluid. Under a high liquid velocity condition, the bubble could be severely deformed and even broken..