隔热层厚度和数量对太空多层光学窗口温度分布的影响

Effects of Thickness and Number of Heat-Insulation Glass Layer on Temperature Distributions of Multi-Layer Optical Windows in Outer Space

航天器上常安装有用于科学观察的多层光学窗口,其温度分布的均匀性会影响成像质量。运用射线踪迹-节点分析法的任意多层镜反射辐射与导热耦合换热模型,研究了隔热层厚度及数量对太空中多层光学窗口温度分布的影响。光学窗口的吸收系数、折射率随波长的变化用一组矩形谱带来近似。研究显示太空中热辐射在光学窗口的冷却过程中起着非常重要的作用,在离玻璃层表面附近很薄的一层玻璃介质内,辐射与导热存在强烈的耦合作用。隔热层厚度越薄,其内的温度分布越均匀,有利于提高成像质量。隔热层数量越多,光学窗口各层玻璃的温度分布越均匀,有利于提高成像质量,但是隔热层最佳数量的确定还需综合考虑其它因素。

The muhi-layer optical windows are usually installed in spacecraft for scientific observation, in which the homogeneity of temperature distribution has effects on image quality. In this paper, considering semitransparent and specularly reflecting interfaces, based on the ray tracing-node analysis method, a multi-layer transient coupled radiative and conductive heat transfer model is used to examine the effects of thickness and the number of heat insulation glass layers on temperature distributions of the multi-layer optical windows. The changes of absorption coefficient and refractive index of the optical window changing with wave length are approximately expressed by using a set of rectangular spectral bands. The study shows that in outer space, thermal radiation plays a very important role in the cooling process of the multi-layer optical window, and in the very thin layer of glass medium very close to the surface of glass layer, the radiative heat flux and the conductive heat flux are coupled with each other intensively. The thinner the insulation glass layer is, the more homogeneous the temperature distribution therein is, thus helpfully improving the image quality. The more the number of insulation glass layers are, the more homogeneous temperature distribution of the multi-layer optical window is, thus also helpfully improving the image quality. Also determination of the optimized number of heat insulation glass layers needs to consider the other factors.