【作者】 杨再利； 王敬鑫； 于大川； 朱春玲；

【Author】 Yang Zaili;Wang Jingxin;Yu Dachuan;Zhu Chunling;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】 过冷大水滴撞击冻结威胁飞行安全,是飞机结冰研究中热点问题。实验针对过冷水滴的发生和温度控制进行了研究,考察了基板温度、水滴过冷度对撞击过程和相变过程的影响,旨在理解过冷水滴结冰与撞击的耦合机理。实验设计了低温系统,分别控制基板温度和过冷水滴过冷度。实验过程中水滴发生器的高度保持不变,保证水滴以相同的速度撞击冷基板表面。实验采用高速相机分别以4000fps和200fps记录水滴撞击过程和稳定状态下的相变过程。实验结果表明,随着基板温度降低,过冷水滴撞击的回缩趋势降低和振荡幅度减小,而高度方向水滴可以产生较大的振荡幅度;随着水滴过冷度增大,水滴粘度系数和表面张力系数增大,导致撞击水滴最大铺展系数降低;过冷水滴低速撞击冷基板可能发生瞬态相变、延迟相变和维持过冷状态,这与基板温度相关;随着冷基板表面温度降低,撞击过冷水滴稳定后发生相变过程所用时间缩短。更多还原

【Abstract】 The impact and freezing of supercooled large droplets would threaten flight safety, which has been a hot topic in the research of aircraft icing. To understand clearly the coupling mechanism between supercooled large droplets freezing and impact process, the generation and temperature control of supercooled large droplets were studied firstly. And then, the effects of substrate temperatures and the degrees of supercooled large droplets on the impact process and freezing process were investigated. A cryogenic system was designed to control the substrate temperature and the subcooling degree of the supercooled large droplets, respectively. During the experiment,the velocity of droplets hitting the cold substrate remains constant by controlling the height of the droplet generator. In the experiment, the high-speed camera was used to record the impact process at 4000fps and record the freezing process of the steady droplets at 200fps. The results show that, with the decrease of substrate temperature, the retraction trend and oscillation amplitude in spreading diameter direction of the supercooled large droplets decrease,but the oscillation amplitude in height direction keep large. Moreover, with the increase of supercooling degrees, the viscosity and surface tension of the droplets increase, which lead to the decrease of the maximum spreading coefficient of the impacting droplets. It is noted that, for droplets impinging on various substrate temperature at low speed, the phenomena of instantaneous freezing, delayed freezing and non-freezing are identified. Finally, with the decrease of substrate temperature, the time of freezing would be shortened.更多还原