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殷一民, 陈爱国, 李猛, 陈力, 陈爽. 高超声速低密度风洞FLEET测速实验研究. 力学学报, 2024, 56(6): 1-7. DOI: 10.6052/0459-1879-24-002
引用本文: 殷一民, 陈爱国, 李猛, 陈力, 陈爽. 高超声速低密度风洞FLEET测速实验研究. 力学学报, 2024, 56(6): 1-7. DOI: 10.6052/0459-1879-24-002
Yin Yimin, Chen Aiguo, Li Meng, Chen Li, Chen Shuang. Velocity measurement in hypersonic low-density wind tunnel using fleet. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(6): 1-7. DOI: 10.6052/0459-1879-24-002
Citation: Yin Yimin, Chen Aiguo, Li Meng, Chen Li, Chen Shuang. Velocity measurement in hypersonic low-density wind tunnel using fleet. Chinese Journal of Theoretical and Applied Mechanics, 2024, 56(6): 1-7. DOI: 10.6052/0459-1879-24-002

高超声速低密度风洞FLEET测速实验研究

VELOCITY MEASUREMENT IN HYPERSONIC LOW-DENSITY WIND TUNNEL USING FLEET

  • 摘要: 高超声速低密度风洞试验对高超声速飞行器的气动特性研究至关重要, 气流速度是其中最受关注的重要参数之一. 高超声速低密度风洞流场具有流速快和密度低等特点, 给速度测量带来很大挑战. 常规测速技术在高超声速低密度流场中应用时局限较多, 而FLEET技术具有不干扰流场和无需外加示踪物等优点, 且直接以风洞工作气体为示踪分子, 有望在高超声速低密度流场速度测量中发挥重要作用. 文章首先研究了不同压强对FLEET信号的影响, 发现随着压强的降低, 光丝中心宽度逐渐展宽; 在低密度条件下FLEET信号仍具有较高强度, 可用于流场的速度测量分析. 随后在Φ0.3m高超声速低密度风洞中分别对Ma5.0和Ma16.0来流条件开展了FLEET测速实验, 结果表明, 随延迟时间的增加, 光丝中心宽度保持展宽趋势, 荧光信号强度逐渐降低; 与Ma5.0相比, 在Ma16.0条件下荧光信号强度衰减速率更慢和光丝中心宽度更宽. 通过FLEET试验测得的Ma5.0和Ma16.0条件下, 风洞来流速度与皮托管测量值的最大相对偏差分别为0.31%和0.49%, 表明FLEET技术能够为高超声速和低密度稀薄流动速度测量提供有效技术手段.

     

    Abstract: Hypersonic low-density wind tunnel test plays an important role in the study of aerodynamic characteristics of hypersonic vehicles. Velocity is one of the most crucial parameters in hypersonic low-density wind tunnel. While obtaining the flow velocity accurately by conventional velocimetry techniques such as LDV and PIV is particularly difficult since the extremely low density and hypersonic velocity in hypersonic low-density flow. Femtosecond laser electronic excitation tagging (FLEET) velocimetry technique offers an opportunity to overcome this problem. As an unseeded and nonintrusive molecular tagging velocimetry method, FLEET directly probing molecular nitrogen (N2) instead of relying on tracer particles for velocity measurement, thereby immediately avoiding issues with particle lag and non-uniform seeding density. This dissertation seeks to answer the practical question as what measurement performance can be expected of FLEET in different pressures. It turns out that the width of optical filament’s center gradually broadening as the pressure decreases, and the intensity of FLEET signals is strong enough for velocity measurement until the pressure is as low as 90Pa. This indicates that FLEET is well suited for velocity measurement in low density flow. Subsequently, FLEET velocity measurement experiments are conducted in Φ0.3m hypersonic low-density wind tunnel in both Mach 5.0 and Mach 16.0 flow. The results suggest that as the delay time increases, the width of optical filament’s center keep broadening, and the fluorescence signal intensity gradually decreases. In contrast to Mach 5.0, the fluorescence signal intensity reduced slower and the width of optical filament’s center are wider in Mach 16.0. And compared with velocities measured by pitot tube, the maximum relative deviation measured by FLEET is 0.31% in Mach 5.0, while which is 0.49% in Mach 16.0. On the whole, FLEET as a relatively recent velocity measurement technique, has been demonstrated as an effective velocimetry method for hypersonic and low-density flow.

     

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