可调谐二极管激光吸收光谱技术一般采用双线法同时测量气体的温度和物质的量分数。然而在频分和时分复用这两种方式下,双线法易存在频率串扰和降低时间分辨率等问题,在实际应用中有一定的局限性。针对此问题,提出了基于波长调制光谱技术的免标定单线测量法,只用一条吸收谱线即可实现对气体温度和物质的量分数的同时测量。以燃烧过程中的主要产物CO₂为目标气体,选择中心频率为5007.787 cm ^-1的吸收谱线R(50)进行实验验证。从扣除背景的峰值归一化二次谐波信号的线型中提取温度信息,再利用扣除背景的一次谐波归一化二次谐波信号提取CO₂的物质的量分数。实验结果表明,免标定单线法与热电偶测量的温度最大相对偏差小于2.5%,物质的量分数的最大相对偏差小于2.8%。验证了用免标定单线测量法同时测量CO₂的温度和物质的量分数是可行的。

The two-line method is usually used to measure the temperature and mole fraction of gases simultaneously in tunable diode laser absorption spectroscopy. However, in practical applications of the two-line method, there exists some limitations such as cross-talk in the frequency division multiplexing method or reducing temporal resolution in the time division multiplexing method. To solve this problem, a new calibration-free one-line method based on wavelength modulation spectroscopy is proposed to implement simultaneous measurement of gas temperature and mole fraction by using a single absorption line. Using main combustion product CO2 as the target gas, and selecting R(50) spectrum line of CO2 at central frequency of 5007.787 cm -1, we verify the calibration-free one-line method. The temperature is extracted from line shape of the background subtracted peak normalized second harmonic signal, and mole faction of CO2 is extracted from the background subtracted first harmonic normalized second harmonic signal. The experimental results show that the maximum relative error between temperature from the calibration-free one-line method and measured temperature is less than 2.5%, and the maximum relative error of mole fraction is less than 2.8%. It is feasible to measure the temperature and mole fraction of CO2 at the same time using the calibration-free one-line method.