基于可调谐半导体吸收光谱的波长调制技术,建立了精确的吸收模型。通过两条已知吸收中心的吸收谱线,对标准具自由光谱范围进行标定,并利用更贴近激光器出光特性的描述模型,得到激光器频率-时间响应,结合实验室标定和HITEMP数据库的杂合吸收谱线参数,建立了可与实际吸收直接比较的精确模型,以诊断燃烧流场。本研究以H₂O为目标分子,选取吸收中心为7185.60 cm ^-1和6807.83 cm ^-1两条吸收线,利用扣除背景的归一化二次谐波信号峰值反演流场温度,并在管式高温炉上进行实验验证,最高测量温度为1500 K,相对误差小于3.1%。吸收模型的准确性决定了所测流场参数的准确性,该模型可应用到更为复杂的燃烧流场环境,实现流场参数的精确测量。

In this study, an accurate absorption model is established by using the wavelength modulation technology based on tunable diode laser absorption spectroscopy. The free spectral range of an etalon is calibrated by the two absorption lines whose transition line centers are known, and the frequency-time response of the laser is obtained using a description model close to the output characteristics of the laser. Along with the hybrid absorption line parameters calibrated in the laboratory and the HITEMP database, an accurate model that can be directly compared with the actual absorption is established for diagnosing the combustion flow field. Herein, H2O is the target molecule, and the transition line centers of the two selected lines are 7185.60 and 6807.83 cm -1. The flow field temperature can be obtained via the peak of the normalized second harmonic signal with background subtracted and verified in a high-temperature flow field generated by a tubular high-temperature furnace. The maximum temperature is 1500 K, and the relative measurement error is less than 3.1%. Further, the accuracy of the absorption model determines the accuracy of the measured flow field parameters. The method used to establish the model can be applied to the complex combustion flow fields for accurately measuring the flow field parameters.