Effects of thermal conductivity of airframe substrate on the dynamic ice accretion process pertinent to UAS inflight icing phenomena
Effects of thermal conductivity of airframe substrate on the dynamic ice accretion process pertinent to UAS inflight icing phenomena
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DOI：
10.1016/j.ijheatmasstransfer.2018.11.132
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发表时间：
2019-03-01
影响因子：
5.2
通讯作者：
Hu, Hui
中科院分区：
文献类型：
--
作者：
Li, Linkai;Liu, Yang;Hu, Hui
对广泛用于轻型无人机系统（UAS）的复合材料机身积冰表面的动态积冰和非定常传热过程进行了实验研究，并与常规有人机使用的金属机身表面的积冰和非定常传热过程进行了比较，以阐明与UAS飞行中结冰现象特别相关的潜在结冰物理过程。两个翼型/机翼模型具有相同的翼型形状，但由不同的材料制成（即，2 W/m.K的热塑性材料，以代表典型的UAS机身基板，与之相比，铝的热导率类似于200 W/m.K，广泛用于常规载人飞行器）。这两个测试模型并排安装在爱荷华州州立大学的结冰研究隧道内（即，ISU-IRT）在相同的湿釉或干雾凇结冰条件下进行的。在结冰试验过程中，利用高速成像系统记录了试验模型表面的动态积冰过程，同时利用红外热成像系统绘制了相应的积冰翼型表面温度分布图。研究发现，在ISU-IRT中，当空气中的过冷水滴撞击翼型时，冰将开始在试验模型表面迅速聚集，并释放大量的熔化潜热，这与翼型表面上受撞击过冷水团的相变有关。研究发现，机身基体的导热系数对动态积冰和积冰表面的非定常传热过程有显著影响。在相同结冰条件下暴露的两个测试模型中，发现由于热塑性基底的导热性低得多，所释放的熔化潜热在热塑性模型的表面上消散得慢得多。与铝模型表面相比，热塑性模型表面熔化潜热的耗散较慢，导致翼型前缘表面温度较高，“加热”区域较大，翼型表面水回流较明显，以及在超过过冷水滴的直接撞击区的更下游位置处形成更复杂的细流形冰结构。(C)2018爱思唯尔有限公司版权所有
An experimental investigation was conducted to quantify the dynamic ice accretion and the unsteady heat transfer process over the ice accreting surfaces of composite-based airframes widely used for light-weight, Unmanned-Aerial-Systems (UAS), in comparison to those over the surfaces of metal based airframes used by conventional manned aircraft, in order to elucidate the underlying icing physics specifically pertinent to UAS inflight icing phenomena. Two airfoil/wing models with the same airfoil shape, but made of different materials (i.e., thermoplastic material with the thermal conductivity being only similar to 0.2 W/m.K to represent typical UAS airframe substrates vs. Aluminum with the thermal conductivity being similar to 200 W/m.K widely used for conventional manned aircraft). The two test models were mounted side-by-side inside an Icing Research Tunnel available at Iowa State University (i.e., ISU-IRT) under the same wet glaze or dry rime icing condition. During the icing experiment, while a high-speed imaging system was used to record the dynamic ice accretion process over the surfaces of the test models, an infrared thermal imaging system was also used to map the corresponding surface temperature distributions over the ice accreting airfoil surfaces. It was found that, upon the impacting of the airborne, super-cooled water droplets in ISU-IRT, ice would start to accrete rapidly on the surfaces of the test models with a significant amount of the latent heat of fusion being released associated with the phase changing of the impacted super-cooled water mass over the airfoil surfaces. The thermal conductivity of the airframe substrate was found to affect the dynamic ice accretion and unsteady heat transfer processes over the ice accreting surfaces significantly. With the two test models being exposed under the same icing conditions, the released latent heat of fusion was found to be dissipated much slower over the surface of the thermoplastic model, due to the much lower thermal conductivity of the thermoplastic substrate. In comparison with those on the surface of the Aluminum model, the slower dissipation of the released latent heat of fusion on the surface of the thermoplastic model was found to cause higher surface temperatures and greater "heated" regions near the airfoil leading edge, more obvious surface water run-back over the airfoil surface, and formation of more complex rivulet-shaped ice structures at further downstream locations beyond the direct impinging zone of the super-cooled water droplets. (C) 2018 Elsevier Ltd. All rights reserved.