可调谐二极管激光吸收光谱氧气测量中的导数光谱处理与浓度反演算法研究

Derivative Spectrum and Concentration Inversion Algorithm of Tunable Diode Laser Absorption Spectroscopy Oxygen Measurement

氧气是发动机燃烧过程的必需成分,在飞行器进气道进行氧气监测需求迫切。针对飞行器上的工程要求和应用特点,设计了一种波长线性扫描可调谐半导体激光吸收光谱(TDLAS)短光程系统结合有限冲击响应(FIR)滤波二阶导数谱算法的方案完成了氧气吸收微弱信号的提取和浓度反演。根据TDLAS工作原理和吸收信号特征,对二阶导数谱用于气体浓度反演的理论依据进行了推导,在此基础上提出一种基于FIR的数字滤波方案来完成吸收信号的噪声滤除和二阶导数谱的提取。实验结果证明,该方案简单易行,提高了检测信噪比,降低了检测限,浓度反演结果准确、线性良好。

Oxygen is an essential component of the engine combustion process. It is an urgent demand for aircraft inlet oxygen monitoring. Aiming at aircraft engineering requirements and application characteristics, a short-path wavelength linear scanning tunable diode laser absorption spectroscopy （TDLAS） system is designed, which complete the weak oxygen absorption signal extraction and concentration inversion combined with the second derivative spectrum algorithm based on finite impulse response （FIR） filter. Theoretical basis for the second derivative spectrum method of gas concentration inversion is deduced according to the absorption signal characteristics and the TDLAS principle. A solution based on the FIR digital filter to complete absorption signal noise filtering and second derivative spectrum extracting is proposed on this basis. Experimental results show that this scheme is simple, the detected signal to noise ratio is improved, and the detection limit is reduced. Inversion results of gas concentration are accurate and linearity is good.