关键词: TDLAS, 谐波信号, 数值模拟, 实验研究

Abstract: TDLAS technology has become one of the important development directions of gas concentration on-line detection technology because of its noncontact, high sensitivity and fast on-line response. Determining the molecular absorption line shape function is the prerequisite for applying this technology. However, there is no effective method for on-line measurement of molecular absorption line shape function, which seriously affects the measurement accuracy of TDLAS technology and limits its application. Therefore, studies the relationship between the characteristic parameters and the molecular absorption line shape function in TDLAS technology through the theory of absorption spectrum and wavelength modulation, and deduces the expression of harmonic terms containing molecular absorption information, eliminating the effects of the background signal, laser intensity, and modulation index according to the relationships between the harmonic signals, and finally establishing the measurement algorithm of absolute absorption intensity based on harmonic signal. The absorption spectral lines of CO₂ molecule and H₂O molecule near 6982cm^-1 is taken as an example for numerical analysis and experimental research, and the simulation and experimental results show that the relative error between the theoretical absorption spectrum and the measured molecular absorption spectrum according to the algorithm is less than 5%, which further improves the measurement accuracy of TDLAS technology and broadens its application range.

Key words: TDLAS, Harmonic signal, Numerical simulation, Experimental research