摘要
可调谐激光二极管吸收光谱(TDLAS)技术因其高灵敏度、高选择性和快速响应的特点,被广泛应用于痕量气体的检测与燃烧诊断研究。基于谐波检测的波长调制光谱(WMS)方法具有高信噪比的优势,是最常用的TDLAS气体传感方法之一。近年来,为了扩展WMS方法的适用范围,减小光谱参数标定误差,针对WMS方法免标定策略的研究逐渐成为热点。传统的免标定WMS方法一般需要根据光谱数据库并结合激光调制参数进行复杂的吸收光谱模拟,对先验光谱参数的准确度和硬件参数提出了很高的要求。针对以上问题,提出了一种基于二次-四次谐波联用的免标定波长调制激光吸收光谱方法,可以实现气体参数的快速、精确测量。与传统免标定WMS方法相比,新方法有以下特点和优势:(1)新方法基于Voigt线型导出,可以适应于任意展宽条件下的测量;(2)新方法只需要利用二次谐波和四次谐波中心峰高参数的代数计算即可获得吸收谱线展宽、积分吸收面积等关键光谱参数,进而实现浓度、温度等气体参数的测量;(3)新方法不需要进行运算量较大的谐波拟合以及高次谐波计算,降低了对硬件系统的要求;(4)因为不需要扫描完整的吸收谱线形状,解决了传统方法在高温高压下由于吸收谱线展宽变大而导致的谐波信号不完整问题;(5)新方法只需要利用光谱数据库中的吸收谱线强度和低状态能量等光谱参数,而不需要利用自展宽系数、温度指数、其他组分碰撞展宽系数等先验参数,降低了对光谱数据库的依赖性。为了验证新方法的可行性,在实验室环境搭建WMS测量系统,选择CH_(4)分子在6046.95 cm^(-1)附近的吸收谱线,并利用二次与四次谐波峰值进行室温下CH_(4)摩尔分数的测量实验。实验结果表明,在20 cm吸收光程长下,CH_(4)摩尔分数测量的相对误差为1.19%,系统的探测极限为4.28×10^(-6)。
Wavelength modulation spectroscopy(WMS)based on harmonic detection,a modality of the tunable diode laser absorption spectroscopy(TDLAS),has been widely employed for gas properties measurement and combustion diagnosis,given its advantages of contactless,rapid,high sensitivity and accuracy.In recent years,to expand the application scope of the WMS method and reduce the calibration error of spectral parameters,the research on the calibration-free strategy of the WMS method has gradually become a hotspot.Traditional calibration-free WMS method generally needs to simulate the absorption spectrum according to the spectral database combined with the laser modulation parameters,which puts forward high requirements for the prior spectral parameters and hardware parameters.A rapid and accurate calibration-free wavelength modulation spectroscopy(WMS)method for gas parameter measurement based on 2ndand 4thorder harmonics is proposed.Compared with the traditional calibration-free WMS method,the proposed method has the following characteristics and advantages.First,the proposed method,analytically deduced from a much more accurate Voigt function model,enables speedy measurement down to milliseconds and general suitability for various degrees of line-shape broadening.Second,the proposed method only needs the algebraic calculation of the central peak height parameters of the 2ndand 4thharmonics to obtain the key spectral parameters,such as absorption line broadening and integrated absorption area,to realize the measurement of gas parameters such as concentration and temperature.Third,the proposed method does not need square iterative fitting calculation and high-order harmonic calculation,which reduces the requirements of hardware system.Fourth,instead of acquiring the entirely scanned absorption line-shape,the proposed methodonly requires extracting the peak values of the harmonics.This characteristic significantly benefits gas diagnosis at elevated pressure and/or temperature.Fifth,the proposed method only needs to use the spe
作者
王一红
周宾
赵荣
汪步斌
WANG Yi-hong;ZHOU Bin;ZHAO Rong;WANG Bu-bin(Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education,School of Energy and Environment,Southeast University,Nanjing 210096,China)
出处
《光谱学与光谱分析》
SCIE
EI
CAS
CSCD
北大核心
2023年第2期368-373,共6页
Spectroscopy and Spectral Analysis
基金
国家重点研究发展计划项目(2017YFB0603204)
国家自然科学基金项目(50976024)
国家自然科学基金项目(50906013)资助。
关键词
吸收光谱
波长调制
谐波检测
免标定
甲烷检测
Absorption spectroscopy
Wavelength modulation
Harmonic detection
Calibration-free
CH4 detection
