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非平衡凝固是过冷条件下水滴凝固过程的重要现象。本文针对飞机结冰过程过冷水滴的非平衡凝固效应,发展了改进的凝固特性预测模型及数值计算方法,并自行搭建了实验系统,开展了所建过冷水滴凝固模型与数值预测方法的实验验证。研究表明,所发展的改进模型可有效表征水滴过冷阶段的非平衡凝固效应,因而对冷水滴凝固速率的预测有较好的改进;当过冷度为0℃时,过冷模型退化为传统模型。基于所建方法,开展了过冷度及冷却条件对水滴凝固特性的影响分析,获得了不同条件下水滴凝固过程的温度分布及相界面变化特征。研究表明,过冷度越大或水滴尺度越小,凝固速率相对越高;在考虑非平衡凝固效应的条件下,过冷水滴凝固速率要高于不考虑非平衡凝固效应的工况。相关研究可为结冰热力学模型的改进,以及结冰特性的精细化预测提供参考。
Unbalanced solidification is an important phenomenon of the solidification of droplets under the condition of supercooling. In this paper, according to the non-equilibrium solidification effect of subcooled water droplets during the icing process, an improved solidification property prediction model and numerical calculation method are developed. An experimental system is set up to carry out the experiment of the established solidification model and numerical prediction method verification. The results show that the improved model can effectively characterize the non-equilibrium solidification effect of the droplets during the supercooling stage and thus improve the prediction of the solidification rate of the cold water droplets. When the undercooling is 0 ℃, the overcooled model degenerates into the traditional model. Based on the proposed method, the influence of undercooling and cooling conditions on the solidification characteristics of water droplets was analyzed, and the temperature distribution and phase interface characteristics of water droplets during solidification under different conditions were obtained. The results show that the higher the undercooling degree or the smaller the droplet size, the higher the solidification rate. Under the condition of non-equilibrium solidification, the solidification rate of the supercooled water droplet is higher than that without considering the non-equilibrium solidification effect. The related research can provide reference for the improvement of icing thermodynamic model and the finer prediction of icing characteristics.