在吸收光谱燃烧流场诊断中,吸收分子谱线参数的准确性直接影响流场参数测量的精度。对燃烧诊断研究中主要探针水汽(H2O)分子的吸收谱线参数进行高精度校准。实验利用波长为1469 nm的近红外半导体激光器作为光源,采用高灵敏的免标定波长调制技术,结合自行搭建的实验室高温测量系统,获得了900~1500 K 温度范围内所选谱线的调制吸收光谱。利用非线性最小二乘L-M拟合算法对H2O吸收光谱进行拟合,精确获得了所选谱线在6807.83 cm -1和6808.04 cm -1的线强、自展宽系数和温度依赖系数;通过对比HITRAN和HITEMP数据库相应的光谱参数,可得线强的相对偏差分别为3.91%与-5.40%,自展宽系数的相对偏差分别为3.01%与-6.49%,温度依赖系数分别为0.5213与0.4567,线强的实验结果不确定度分别为1.05%与1.96%。所提出的免标定波长调制光谱参数标定法在高温光谱测量中具有检测灵敏度高、光谱信噪比高等优点,有利于提高光谱参数校准的精度,将为燃烧流场参数的精确反演提供谱线基础。

In the diagnosis of combustion flow field by absorption spectra, the accuracy of absorption molecular spectral line parameters directly affects the accuracy of the measurement of flow field parameters. In this paper, the absorption spectral line parameters of water molecules used as the main probe in combustion diagnostic studies are calibrated accurately. A near-infrared diode laser with a wavelength of 1469 nm is used as the light source, and the highly sensitive calibration-free wavelength modulation technology is used. Combining with the established laboratory high temperature measuring system, we obtain the modulation absorption spectra of the selected spectral lines in the temperature range of 900--1500 K. By using the nonlinear least square L-M fitting method to fit the H2O absorption spectra, the line intensities, self-broadening coefficients, and temperature dependent coefficients of the selected spectral lines at 6807.83 cm -1 and 6808.04 cm -1 are accurately obtained. By comparing the HITRAN and HITEMP databases, we obtain that the relative deviations of line strengths are 3.91% and -5.40%, the relative deviations of self-broadening coefficients are 3.01% and -6.49%, the temperature dependence coefficients are 0.5213 and 0.4567, and the uncertainties of the experimental results of the two line strengths are 1.05% and 1.96%, respectively. The spectral parameter calibration method based on calibration-free wavelength modulation has the advantages of high detection sensitivity and spectral signal-to-noise ratio in high temperature spectral measurement, which is conductive to improve the accuracy of spectral parameter calibration, and will provide spectral line foundation for accurate inversion of combustion flow field parameters.