基于TDLAS的电弧风洞流场Cu组分监测

电弧风洞是进行防热材料和防热结构考核与研究的必要设备，也是高超声速地面试验能力的重要组成部分，但电弧加热器的电极烧蚀会导致较为严重的流场污染，影响试验准确性。利用可调谐二极管激光吸收光谱技术（TDLAS），通过对20 MW级片式电弧加热器内部流场中Cu原子809.25 nm跃迁谱线进行实时测量，研究了电弧风洞流场中Cu污染情况和电极烧蚀情况。在获得Cu原子该谱线低能态数密度基础上，估算了运行功率分别在7.3、8.7、10.0和11.7 MW时流场中Cu组分（原子态和离子态）总数密度平均为10.6×10¹³、11.2×10¹³、11.7×10¹³和16.4×10¹³ cm^-3，同时得到平均电极烧蚀率约为1.65×10^-5 g/C。试验还发现，TDLAS信号在高温流场建立阶段起伏变化明显，并且在功率跃变时也会出现突然增强而后迅速回落的现象，表明电弧抖动会使电极烧蚀严重加剧。

Monitoring copper species in flow of arc-heated wind tunnel based on TDLAS

Arc-heated wind tunnel, as an important hypersonic test facility, is indispensable for examining and developing thermal protection materials and structures. However, the flow is always contaminated by copper species generated from the surface molten or boiled electrodes, undermining the accuracy of the experiment. In this work, to quantitatively study the copper contamination and the electrode ablation, the Tunable Diode Laser Absorption Spectroscopy (TDLAS) is employed by measuring the 809.25 nm transition spectrum line of Cu in real-time in the 20 MW segmented arc heater. Based on acquisition of the number densities of lower state, the average number densities of copper species (including atoms and ions) in the inner flow of arc heater with the different power of 7.3, 8.7, 10.0 and 11.7 MW are measured, deriving results as 10.6×10¹³, 11.2×10¹³, 11.7×10¹³, and 16.4×10¹³ cm^-3 respectively. In the meantime, the average electrode ablation rate (defined by mass loss per unit of charge crossing the electrode surface) is obtained as about 1.65×10^-5 g/C. What's more, the monitoring TDLAS signal showed violent fluctuation before the steady flow is established and showed sudden sharp rise when the power of the arc heater changed, demonstrating that the fluctuation of arc spots could greatly aggravate the electrode ablation.