气动加热下光学窗口传热特性的数值模拟

针对气动加热条件下光学窗口辐射导热耦合传热开展研究,以了解光学窗口的热辐射发射规律及热防护性能。采用有限体积法、蒙特卡罗法、谱带模型建立了具有镜反射界面的光学窗口辐射传输及辐射导热耦合传热计算模型,对具有两层SiO2玻璃的光学窗口传热特性进行了模拟。结果表明处于高温区玻璃向外发射热辐射,低温区玻璃吸收热辐射;除了加热面附近外的玻璃区域,辐射热流密度远大于导热热流密度,在2.9～4.2μm谱带内的辐射热流密度大于0.4～2.9μm谱带内的;在0.4～2.9μm谱带内,可见光波长内的出射辐射热流密度最小,中红外波长范围内出射辐射热流密度最大。在光学窗口总厚度一定的情况下,降低玻璃层厚度和玻璃夹层气体热导率能够有效降低光学窗口非加热面稳态温度。

Numerical Simulation on Heat Transfer Characteristics of Optical WindowsUnder Aerodynamic Heating

The radiation and conduction coupled heat transfer processes in optical windows under aerodynamic heating are studied in order to understand the thermal emission characteristics and the thermal protection properties.A computational model for the coupled heat transfer in optical windows with Fresnel interfaces is established by FVM,MCM and spectral band model.The heat transfer characteristics for a specific optical window with two SiO2 glass lay-ers are numerically simulated.Results show that the glass layer under aerodynamic heating has net radiation emission and the other layer has net radiation absorption.Radiative flux in the optical window is greater than conductive flux except in the vicinity of the heated surface.The radiative flux in the wavelength between 2.9 μm and 4.2 μm is grea-ter than in the wavelength between 0.4 μm and 2.9 μm where the radiative flux going into spacecraft interior through the optical window has the lowest value in the visible spectrum and the highest value in the mid infrared spectrum.In the case of the optical window total thickness unvaried,decrease in both the gas conductivity and the gas layer thick-ness can effectively lower the steady state temperature of the optical window’s unheated surface.