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中文核心期刊

基于CN自由基的火星再入流场温度测量

TEMPERATURE MEASUREMENTS IN SIMULATED MARS ATMOSPHERES BASED ON THE CN RADICAL EMISSION SPECTRUM

  • 摘要: 利用氰自由基(CN)B2Σ+→X2Σ+ 电子带系的发射光谱温度测量技术诊断模拟火星再入流场高温气体的温度. 以双原子分子光谱理论为基础,通过确定CN 自由基B2Σ+→X2Σ+ 电子带系中 Δv = 0 振动带系发射光谱的跃迁波数、Einstein 跃迁几率以及不同振转能级粒子数等参数,得到了任意转动温度和振动温度下的理论光谱强度分布,结合经窄线宽半导体激光器标定的仪器展宽(Lorentz 线型,半宽度FWHM 为0.154 nm),为CN自由基B2Σ+→X2Σ+ 电子带系发射光谱测温技术提供理论依据. 利用激波管模拟火星再入流场环境,通过分析激波波后不同时刻处高时间、空间分辨率的CN 自由基发射光谱,得到了激波波后高温气体不同时刻处的转动温度和振动温度,并根据得到的温度信息给出了激波诱导时间和弛豫时间.

     

    Abstract: Temperature measurements behind the strong shock waves for simulated Martian atmosphere were presented in this paper. Based on the inherent molecular structure characteristics of the CN radicals, the energy level distribution, the transition frequency and Einstein spontaneous emission transition probability were systematically analyzed and numerically studied. Meanwhile, the FWHM of apparatus function was measured experimentally to be Lorentzian profile of value 0.154nm by using of a narrow line width diode laser. The dependence of the spectral structure on the rotational temperature and vibrational temperature were numerically analyzed in detailed. In shock-tube experiments, the emission of CN (B2Σ+→X2Σ+) system measurements were performed behind a strong shock wave in a CO2-N2 mixture with two di erent conditions of initial pressure and velocity. Rotational and vibrational temperatures behind the strong shock wave, and the radiation structure of the shock layer, including induction, relaxation and equilibrium processes were obtained through analysis of time gating optical emission spectra with nanosecond temporal resolution.

     

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