中红外吸收光谱测量激波风洞自由流中 NO 浓度和温度

JF-10氢氧爆轰驱动激波风洞内的高焓自由来流气体中含有因电离和离解等非平衡过程产生的微量组分。利用可调谐二极管激光吸收光谱技术(TDLAS),对自由流中 NO 微量组分的浓度和温度进行测量,有助于定量理解气体电离和离解这一非平衡过程。本实验中,JF-10氢氧爆轰驱动激波风洞实验段内压力为百帕量级,在谱线加宽中多普勒加宽占据主导,多普勒半高宽可由分子平均热运动速度获得,其半高宽与温度的平方根成正比,因此选取一条吸收谱线并准确测定其多普勒半高宽即可得到温度和浓度。本实验中采用中红外量子级联激光器(Quantum Cascade Laser),选取1909.7cm-1附近6条吸收线作为吸收线,在2kHz 的扫描频率下,采用直接吸收-波长扫描法进行 NO 温度和浓度测量。实验测得自由流中 NO 平均分压约为0.33Pa,自由流平均温度约为600K。

Nitric oxide concentration and temperature measurement for shock tunnel free stream using mid-infrared absorption spectroscopy

In this paper,JF-10 shock tunnel is driven by H2/O2 detonation and the free-stream contains some trace components which are generated by non-equilibrium processes such as ionization and dissociation.Tunable diode absorption spectroscopy (TDLAS)is used for tempera-ture and concentration measurement of nitric oxide in the free-stream and this quantitative meas-urement is helpful to understand the non-equilibrium processes.In the experiments,the test sec-tion’s static pressure of JF-10 shock tunnel is just several hPa.Thus,Doppler broadening domi-nates,which is caused by random thermal motion of the absorber species.The half width of Doppler broadening is temperature dependent and this functional relation provides a method for gas temperature and species concentration measurement.A mid-infrared quantum cascade laser of 5.2μm central wavelength is used and gas temperature and nitric oxide concentration are meas-ured using a single line of 1909.7cm-1 wavelength by direct absorption-wavelength scanning method under 2kHz scanning frequency.The measured partial pressure of nitric oxide is about 0. 33Pa which represents its concentration and the temperature is about 600K in the free-stream.