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Measurements of Metastable [math] Molecules in Nonequilibrium Supersonic Flows
Journal of Thermophysics and Heat Transfer ( IF 2.1 ) Pub Date : 2021-07-30 , DOI: 10.2514/1.t6254
Elijah R. Jans 1 , Ilya Gulko 1 , Dirk C. M. van den Bekerom 1 , Terry A. Miller 1 , Igor V. Adamovich 1
Affiliation  

Nonintrusive laser diagnostics are used for the measurements of metastable nitrogen molecules in the lowest excited electronic state, N2(A3Σu+), in a nonequilibrium flow, blowdown supersonic wind tunnel. The tunnel is operated with nitrogen at plenum pressures of P0=200250 Torr, with the flow expanding through a two-dimensional contoured nozzle to the Mach number of M=3.64.6. The steady-state run time of the tunnel is approximately 10 s. The flow is excited by a repetitive nanosecond pulse discharge operated in the plenum or in the nozzle throat. Time-resolved absolute N2(A3Σu+,v=0) populations in the plenum are measured by single-pass, continuous wave tunable diode laser absorption spectroscopy (TDLAS). In the supersonic test section, absolute N2(A3Σu+,v=02) populations are measured by cavity ring down spectroscopy (CRDS), using a tunable pulsed laser system operated at 10 Hz. During each run, 50 single-shot ring down traces are acquired, demonstrating good shot-to-shot reproducibility. The results demonstrate that the cavity ring down time is not affected by the supersonic flow. N2(A3Σu+,v=02) populations and the flow temperature are inferred from the single-shot CRDS data. At the conditions when the flow is excited by the discharge in the nozzle throat, N2(A3Σu+,v=0) population in the supersonic test section is measured by both CRDS and TDLAS diagnostics. The two diagnostic techniques are complementary and can be used for characterization of nonequilibrium reacting flows over a wide range of pressures, including short-run-time high-enthalpy flow facilities.



中文翻译:

非平衡超音速流动中亚稳态 [数学] 分子的测量

非侵入式激光诊断用于测量处于最低激发电子态的亚稳态氮分子, N2(一种3Σ+),在非平衡流动中,排污超音速风洞。隧道使用氮气在压力为0=200——250 Torr,流动通过二维轮廓喷嘴扩展到马赫数 =3.6——4.6. 隧道的稳态运行时间约为 10 s。该流由在增压室或喷嘴喉部中操作的重复纳秒脉冲放电激发。时间分辨绝对值N2(一种3Σ+,v=0)通过单程连续波可调谐二极管激光吸收光谱 (TDLAS) 测量增压室中的人口数量。在超音速测试部分,绝对N2(一种3Σ+,v=0——2)使用频率为 10 Hz 的可调脉冲激光系统,通过腔衰荡光谱 (CRDS) 测量种群数量。在每次运行期间,都会获得 50 条单次衰减轨迹,证明了良好的一次次重复性。结果表明,腔的衰减时间不受超音速流动的影响。N2(一种3Σ+,v=0——2)从单次 CRDS 数据推断人口和流动温度。在喷嘴喉部的放电激发流动的条件下,N2(一种3Σ+,v=0)超音速测试部分的人口由 CRDS 和 TDLAS 诊断测量。这两种诊断技术是互补的,可用于表征各种压力下的非平衡反应流,包括短运行时间高焓流设施。

更新日期:2021-07-30
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