Abstract:

Atomization of high viscous non-Newtonian fluid into gas by spinning disk promotes intimate contact between the two phases. The size of droplets is directly determined by the ligament breakup characteristics, which is the key factor to affect the qualities of product. For spinning disk atomizer in this paper, the ligament breakup characteristics are analyzed, the ligament spacing model concerning with both the surface tension and viscous forces is proposed. Meanwhile, the ligament breakup mechanism is summarized. The results indicate that the viscosity always produces damping effect for the formation of ligament. With the increasing of viscosity, the ligament spacing will also increase. In general, the ligament number is influenced by the linear velocity of liquid film at the disk rim, while it becomes stable in fully-ligament mode. The disk with larger diameter and slower speed is advisable in the actual atomization process. For high viscous non-Newtonian fluid, the ligament number can be predicted by the Weber number, the equivalent Reynolds number and the flow index. This paper supplies the theoretical basis and further application for the design and optimization of centrifugal atomization of high viscous non-Newtonian fluid.

Key words: fluid mechanics, model, experimental validation, ligament mode, spinning disk, centrifugal atomization

摘要：

高黏性流体经转盘离心雾化以液滴形式进入气相可显著改善气液相间接触，其纤维化特性直接决定了雾化液滴的尺寸，是影响物料品质的关键因素。针对转盘离心雾化器，对非牛顿黏性液膜失稳纤维化过程的物理机制进行了分析，分析了高黏度流体，仅考虑黏性作用时，黏性力对纤维间距的贡献，建立了黏性力与表面张力耦合作用下液膜破碎的纤维间距预测模型，探讨了液膜纤维化的一般规律。结果表明，黏性对液膜的失稳纤维化起抑制作用，黏度提高，纤维数量减小，纤维间距增大。纤维数量与转盘边缘液膜线速度相关。进入完全纤维状模式后，纤维数量趋于稳定，提高转速引起纤维数量稳定的流量范围缩小，不利于雾化，可采用低转速、大直径转盘改善雾化效果。非牛顿高黏流体液膜破碎后的纤维数量与Weber数、等效Reynolds数和流变指数直接相关。研究结果对高黏流体的转盘离心雾化系统设计与优化提供了可借鉴的理论与应用基础。

关键词: 流体力学, 模型, 实验验证, 纤维化, 转盘, 离心雾化