内混式雾化喷嘴的高速液滴形成迁移行为及其对铸坯表面膜沸腾传热机制的影响

高速连铸中二冷区冷却强度大，对传热均匀性要求更高，与内混式气水雾化喷嘴的高速液滴形成和迁移行为等密切相关。如能提高喷嘴的冷却均匀性和冷却强度，则可提升高速连铸的铸坯质量。喷嘴内液滴破碎、碰撞、迁移、气液动量传输行为及其对高速液滴特征的影响是什么？高速液滴穿过蒸汽膜、接触铸坯表面的变形、蒸发和冷凝行为及其对蒸汽膜更新行为的影响是什么？高速液滴特征参数如何影响铸坯表面膜沸腾传热机制？这些问题，前人研究较少，需要进一步探索。本申请项目以解决这些问题为目标，利用高速相机研究液滴的破碎、碰撞、迁移行为；利用三维粒子图像测速仪研究液滴离开喷嘴到达铸坯表面过程中的迁移行为和速度分布；利用热态实验研究液滴特征和蒸汽膜更新行为对铸坯表面传热的影响。结合理论分析和数学模型，从根本上明确内混式气水雾化喷嘴液滴特性参数的调控机制，为优化喷嘴结构，提高铸坯所受冷却强度及冷却均匀性提供理论基础和技术依据。

In the high-speed continuous casting, due to the large cooling intensity in the secondary cooling zone, the heat transfer uniformity is required to be higher. The cooling effect is closely related to the formation and migration behavior of high-speed droplets of the internal mixing air-mist nozzle. If the cooling intensity and uniformity of nozzle can be improved, the strand quality of high-speed continuous casting will be improved. What is the breakage, collision and migration behavior of droplets, the air-liquid momentum transfer and its effect on high-speed droplet characteristics in the nozzle? What is the behavior of passing through the vapor film, deformation, evaporation and condensation of high-speed droplets, and its effects on the replacement of vapor film on the strand surface? How does the high-speed droplet characteristic parameters affect the film boiling heat transfer mechanism of the strand surface? These problems are less studied by predecessors and need further exploration. In order to solve these problems, this project aims to study the breakage, collision and migration behaviors of droplets by using a high-speed camera; to study the migration behavior and velocity distribution of droplets leaving the nozzle to reach the slab surface using a three-dimensional particle image velocimeter. The experiment will be conducted to study the effect of droplet characteristics and vapor film replacement behavior on the heat transfer of strand surface. Combined with theoretical analysis and mathematical model, the regulation mechanism of the droplet characteristic parameters of the internal mixing air-mist nozzle is fundamentally clarified, which provides theoretical basis and technical basis for optimizing the nozzle structure and improving the intensity and uniformity of secondary cooling of strand.