Study on the Droplet Jet Impingement Process on Wall Based on DPM-to-VOF Method
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摘要: 喷淋雾化被广泛应用于核动力设备中，以保证其安全稳定运行。喷淋时，部分液滴会撞击设备壁面，以液膜的形式进行扩展和演变。基于Fluent软件的离散相-连续相转换（DPM-to-VOF，DTV）方法进行了液滴射流撞壁研究，使用两液滴滴落过程试验图像验证了模拟方法的准确性，研究了液滴射流注入速度、入射角度对壁面液膜形态的影响规律，得到了液滴溅射率随入射条件的变化情况，并分析了液滴撞击壁面时重力、表面张力、速度分量等对液膜形态扩展过程、液滴溅射率的影响。研究发现，增大注入速度能加大对液膜的扰动，液膜与壁面的接触面积显著增大，液膜区宽度和高度增加；增大入射角度对液膜形态的改变影响较大，体现在液膜区宽度增加和液膜区高度减小，液膜表面稳定性减低。溅射率随着注入速度和入射角度的增大而增大，其中，入射角度对溅射率的影响更大。Abstract: Spray atomization is widely used in nuclear power equipment to ensure its safe and stable operation. In the spraying, some droplets will impinge on the equipment wall and expand and evolve in the form of liquid film. This study investigated droplet jet impingement based on Fluent’s Discrete Particle Model-to-Volume of Fluid (DPM-to-VOF, DTV) transition method, and the accuracy of the simulation method was validated using experimental images of two droplet falling processes. The research investigated the influence of droplet injection velocity and incident angle on the wall liquid film morphology and obtained the variation of droplet splash rate with incident conditions. Furthermore, the effects of gravity, surface tension, velocity components, and other factors on the expansion process of liquid film morphology and droplet splash rate during droplet impingement on the wall were analyzed. It is found that increasing the injection velocity could enhance the disturbance to the liquid film, significantly increasing the contact area between the liquid film and the wall and the width and height of the liquid film area. Increasing the incident angle had a significant impact on the change of liquid film morphology, which was reflected in the increase in the width and decrease in the height of the liquid film area, leading to decreased stability of the liquid film surface. The splash rate increased with the increase of injection velocity and incident angle, with the incident angle having a more significant impact on the splash rate.
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图 2 液滴滴落撞击壁面的转换、演变过程和网格变化情况
Figure 2. Transitions, Evolutionary Processes and Mesh Changes in Droplet Impingement on the Wall
图 9 不同注入速度条件下的接触面示意图
Figure 9. Schematic Diagram of Contact Surfaces at Different Injection Rates
图 10 不同注入速度条件下的液膜特征曲线
Figure 10. Characteristic Curves of Liquid Film at Different Injection Rates
图 11 不同注入速度条件下的液滴流动轨迹示意图
Figure 11. Schematic Diagram of Droplet Flow Trajectory at Different Injection Rates
图 12 不同入射角度条件下的液膜特征
Figure 12. Liquid Film Characteristics at Different Incidence Angles
图 13 不同入射角度条件下的液膜形态和接触面示意图
Figure 13. Schematic Diagram of Liquid Film Morphology and Contact Surfaces at Different Incidence Angles
图 14 不同入射角度条件下的液膜特征曲线
Figure 14. Characteristic Curves of Liquid Film at Different Incidence Angles
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