低温高湿表面动态润湿特性对水汽冰晶生长及脱附的影响机制

Inaccurate speed measurement due to water vapor icing is one of the severe challenges that High speed EMU face during safe operation in winter, and it is of great scientific significance and application value to explore the mechanism of ice adhesion inhibition by surfaces with different wettability under low temperature and high humidity water vapor. In this project, coatings with different wettability due to different micro-nano structure (dense and porous) and surface energy will be controllable-constructed by a conventional coating-curing process on radar materials including metal and plastic. A novel method for dynamic online monitoring the behaviors of water vapor icing and ice crystal desorption from interface under alternate low temperature and high humidity environment (synergy of alternate low temperature and high humidity environment, dynamic tracking of icing behavior and ice adhesion/desorption from interface) will be established. The behaviors of water vapor adsorption, wetting, ice crystal growth, recrystallization and desorption from interface on low temperature and high humidity hydrophilic/hydrophobic surfaces will be studied. The relationship between water vapor ice crystal growth, ice desorption on surfaces with different wettability and microstructure, surface energy, dynamic wettability of these surfaces will be explored. A theoretical model about the effect of dynamic wettability on “water vapor ice crystals desorption from interface” will be established. The essence that how surfaces with different wettability facilitate ice desorption from interface will be revealed. The results will provide a theoretical basis for promoting development of anti- water vapor icing material and enhancing the technical level of anti- water vapor icing in the railway traffic field.

水汽覆冰冰冻导致的测速失准是高铁动车冬季安全运行面临的严峻挑战之一，探索润湿性表面抑制低温高湿水汽冰晶黏附的机理具有重要的科学意义和应用价值。本项目采用一步成膜法，于雷达罩体金属/塑料基材表面构筑具有不同微纳米织构（致密、多孔）及表面能的润湿性涂层表面；建立“交替低温高湿水汽结冰及界面冰晶脱附行为动态监测”测试新方法（“交替低温高湿水汽环境”、“冰晶生长动态跟踪”、“界面粘附/脱附力监测”协同）,深入研究低温高湿亲水/疏水表面水汽冰晶吸附、润湿、冰晶生长、再结晶以及界面脱附行为；探讨不同润湿性表面水汽冰晶生长、界面脱附与其微观结构、表面能及动态润湿性之间的关系规律；建立表面动态润湿特性对“水汽冰晶界面脱附”影响机制的理论模型，揭示润湿性表面促进水汽冰晶界面脱附的本质。研究结果将为促进防水汽结/覆冰材料研发以及提升铁路交通领域抗水汽结冰方面的技术水平提供理论基础。

针对水汽覆冰冰冻给高铁动车安全运行带来的严峻挑战，本项目采用一步喷涂法，于传统基材表面构筑出具有不同润湿性及不同微结构的疏水涂层，建立起“低温高湿水汽环境模拟、水汽冰晶生长及界面冰晶脱附行为”协同测试评估新方法，深入探讨了涂层微结构与动态润湿性的关系、低温高湿表面水汽吸附、冻结、冰晶生长及脱附行为以及界面冰晶脱附的影响机制等核心内容。研究发现：低温高湿（-10℃~-30℃,~100%RH）动态高速水汽环境下，表面吸附霜晶形貌与温度、水汽强度及方向相关性较大；交替低温高湿（-10℃~-30℃，10℃~30℃）环境下，静态吸附冰晶微观形貌包含树枝状、棒状、飞鸟状、团簇状等，且呈小冰晶与团簇冰晶混合形貌；当动态/静态吸附冰晶融化后，亲水表面易出现连片水膜，疏水表面则为分散球形水珠。对不同低温动态水汽覆冰界面冰晶形貌及冰粘附力综合分析，发现高寒高湿（-25℃）水汽撞击材料表面前已冻结为冰晶颗粒，不同润湿性表面均呈层状球形冰晶团簇随机分布，且表面冰粘附力较低且相对接近；低温高湿（-5℃）水汽以液态沉积于表面，水汽吸附铺展形貌与表面润湿性紧密相关，疏水/超疏水表面比亲水上表面更有利于抑制持续动态水汽冻结。从覆冰界面结构-润湿-脱冰关系规律的角度，综合剪切脱冰力与自然融脱冰时间，发现织构化疏水表面微米尺度结构演变对表面动态润湿性和脱冰能力的影响相反，且比纳米结构演变影响更大。特别地，伴随微米尺度垂直落差降低或消失，自然融脱冰模式由“粘滞坠落”转变为“快速滑落”，从力学、传热和动态润湿性深入理论分析，揭示融冰界面的滑动行为不等于固着水滴的迁移滚动性（即结冰前和脱冰后材料表面的动态润湿性），而显著依赖于微米尺度结构。本项目揭示了低温高湿环境条件、微纳结构演化对动态润湿特性及融/脱冰行为的协同影响机制，阐明了润湿性表面促进冰晶脱附的本质，将为促进防水汽结/覆冰材料研发提供理论基础。