【作者】 王敬鑫； 杨再利； 朱春玲； 于大川；

【Author】 Wang Jingxin;Yang Zaili;Zhu Chunling;Yu Dachuan;Department of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics;State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics;

【机构】 南京航空航天大学航空学院； 南京航空航天大学机械结构力学及控制国家重点实验室；

【摘要】 飞机穿越含有过冷水滴云层时迎风面发生水滴撞击冻结现象,威胁飞行安全。在明冰条件下,水滴以多角度撞击低温表面并向后溢流形成水膜。因此,开展干燥倾斜表面液滴撞击相变过程研究,有助于理解初始水膜的形成过程。实验探究了基板温度,倾斜角度和静态接触角对撞击过程的影响。为了避免表面结霜影响,实验设计并营造密闭干燥环境。实验采用侧视和俯视同时记录的方式,其中,侧视记录水滴撞击过程,俯视拍摄水滴相变形貌。实验中利用高速相机获取的撞击水滴图像,通过图像处理方法获取水滴轮廓,确定撞击水滴的铺展直径和液膜前缘/后缘位置变化过程。实验结果表明,倾斜表面撞击水滴的铺展过程与滑移过程是同步发生的;冷基板表面撞击水滴回缩程度大幅降低,但是表面温度对最大铺展系数影响较低。随着冷基板倾斜角度增大,撞击水滴受到拉伸,导致最大铺展系数增大,甚至当倾斜角度达到60°时,水滴发生分裂。此外,基板倾斜角度影响水滴相变形貌。当基板温度为-10℃情况下,水滴撞击倾斜超疏水表面发生弹跳并离开表面。更多还原

【Abstract】 The phenomena of impacting and freezing of droplets would appear, when aircraft encounters clouds with supercooled water droplets in flight, which threaten aircraft safety. Under the glaze icing condition, the water droplets impact the cold surface at multiple angles and run back to form the water film.Therefore, the research of impacting and freezing process of droplet impinging on a dry inclined surface is helpful to understand the formation of the initial water film. The experiments aim to investigate the influences of surface temperatures, tilt angles and static contact angles on the impact and freezing process.The dry and closed environment was designed to avoid the influence of frost on the surface. The experiment combined side and top views, to record impact process and freezing process simultaneously.The images acquired by high-speed camera were dealt to obtain the contour of the droplet, and then get the change of spreading diameter, the tail position and the front position of droplet impinging on inclined surface. The results show that the spreading process and the slipping process of the droplet impinging occur synchronously. The degree of retraction of droplet impinging on cold surface is greatly reduced, but the degree of supercooling has a low effect on the maximum spreading diameter coefficient. As the inclination angle of supercooling substrate increases, the droplet impinging on surface is stretched strongly,which lead to the maximum spreading diameter coefficient of the droplet increases. And as the tilt angle of the substrate reaches 60 degrees, the droplet impinging on the surface breaks up. In addition, the tile angle of the substrate has an apparent influence on the final shape of the ice bead. For the cases of small super-cooling degrees, compared with the adhesion of droplet impinging on the hydrophilic surface, the water droplet would bounce off the incline super-hydrophobic surface.更多还原