基于相干反斯托克斯拉曼散射的等离子体流场热力学非平衡特性表征方法研究

Characterization of thermodynamic non-equilibrium of plasma flow using coherent anti-Stokes Raman scattering

  • 摘要: 流场温度是流体最基本的参数之一,流场温度测量精度直接影响到高超声速飞行器气动力、气动热以及热防护等性能预测准确性。本文基于CARS技术基本原理,开发了面向非平衡流场的CARS光谱计算及振转温度反演算法,并在1000 K~2300 K静态环境下对其准确性开展了实验验证。搭建了基于微波等离子体的非平衡流场,获取了不同压强、流量以及组分下等离子体流场的振转温度信息。结果显示在实验条件范围内,振动温度随着压强的增加而降低,随N2体积流量和Ar体积分数呈现先增大后降低的趋势;转动温度随着压强的增加而降低,随N2体积流量呈现先增大后降低的趋势,随Ar体积分数的增加而增大;非平衡度随压强的增加而增加但其变化率随压强增加而减小,随N2体积流量的增加呈现先降低后增大的趋势,随Ar体积分数的增加而降低。

     

    Abstract: Temperature is considered to be one of the most concerned parameters to quantitatively describe flow characteristics, of which the measurement accuracy directly affects the prediction of aerodynamic, aerothermal and thermal protection performance of hypersonic vehicles. Based on the principles of Coherent Anti-Stokes Raman Scattering (CARS), a CARS spectral computation and vib-rotational temperature inversion program is proposed for characterizing the thermodynamic non-equilibrium properties of the high-temperature gas flow field. And corresponding accuracy from 1000 K to 2300 K is verified in a static environment. A non-equilibrium microwave plasma flow is built and its vibrational temperature and rotational temperature with different pressures, N2 volumetric flow rate, and compositions are obtained by using the developed program. The results show that within the range of experimental conditions, with pressure increasing, the vibrational temperature and rotational temperature decrease, while the thermodynamic non-equilibrium degree increases but corresponding increase rate decreases. With N2 volumetric flow rate increasing, the vibrational temperature and rotational temperature first increase and then decrease, while the thermodynamic non-equilibrium degree exhibits an opposite trend. With Ar volume fraction increasing, the vibrational temperature first increases and then decreases, and the rotational temperature increases, while the thermodynamic non-equilibrium degree decreases.

     

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