汽-水分离器内双液滴碰撞的数值模拟研究

Numerical Investigation of Binary Droplet Collision in Steam Separator

采用流体体积函数(VOF)方法模拟压水堆汽-水分离器内等直径液滴对心碰撞,研究典型的聚合,低、中、高韦伯数(We)的反射分离过程。观察碰撞过程中液滴的形状,记录并分析动能和表面能相互转化以及能量耗散的进程。结果表明:在高We反射分离时,表面扩张的过程中,外部液体会脱离形成环状,液环在表面张力作用下收缩,与内部液体重新接触后使表面复杂剧烈的波动;这影响了分离过程以及子液滴的形成,导致Kim子液滴模型无法准确预测子液滴数目和直径。通过模拟不同We下的碰撞,得到等直径对心碰撞聚合与反射分离的临界We为15.6,并与3个预测模型进行了对比,Qian模型预测结果与模拟结果吻合良好。

Numerical simulation was carded out by using fluid Volume function （VOF） method to study the equal-sized head-on binary droplet collision in steam separators. The typical coalescence and reflexive separation with low, middle, high We, were investigated. Droplet shapes during the collision process were observed. And transformation between kinetic energy and surface energy, energy dissipation were analyzed to achieve better knowledge on the collision process. It was found that in high We reflexive separation, the external liquid departures out of the droplet and forms a circular ring. The liquid ring is forced by the surface tension to contract and impact on the inner liquid, which leads to the surface＇s fierce and complicated oscillation. This phenomenon affects the separation process and satellite droplet formation. And Kim＇s satellite droplet model cannot make precise prediction. By simulating the equal-sized head-on collisions with various We, critical We between coalescence and reflexive separation was found as 15.6. And comparison with three models shows that. Qian model matches well.