基于波长调制光谱非线性特征的气体浓度宽量程检测方法  

Wide⁃Range Gas Concentration Detection Method Based on Nonlinear Characteristics in Wavelength Modulation Spectroscopy

作　　者：王前进 孙鹏帅 张志荣 蔡永军 黄文彪 庞涛 夏滑 吴边[2] Wang Qianjin;Sun Pengshuai;Zhang Zhirong;Cai Yongjun;Huang Wenbiao;Pang Tao;Xia Hua;Wu Bian(School of Environment Science and Optoelectronic Technology,University of Science and Technology of China,Hefei 230026,Anhui,China;Anhui Provincial Key Laboratory of Photonic Devices and Materials,Anhui Institute of Optics and Fine Mechanics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,Anhui,China;Key Lab of Environmental Optics&Technology,Anhui Institute of Optics and Fine Mechanics,Hefei Institutes of Physical Science,Chinese Academy of Sciences,Hefei 230031,Anhui,China;Advanced Laser Technology Laboratory of Anhui Province,Hefei 230037,Anhui,China;PipeChina General Academy of Science&Technology,Langfang 065000,Hebei,China)

机构地区：[1]中国科学技术大学环境科学与光电技术学院,安徽合肥230026 [2]中国科学院合肥物质科学研究院安徽光学精密机械研究所光子器件与材料安徽省重点实验室,安徽合肥230031 [3]中国科学院合肥物质科学研究院安徽光学精密机械研究所中国科学院环境光学与技术重点实验室,安徽合肥230031 [4]先进激光技术安徽省实验室,安徽合肥230037 [5]国家管网集团科学技术研究总院,河北廊坊065000

出　　处：《中国激光》2024年第5期206-212,共7页Chinese Journal of Lasers

基　　金：国家重点研发计划(2022YFB3207601,2021YFB3201904);国家自然科学基金(42005107,11874364,41877311);中国科学院合肥研究院“火花”基金项目(YZJJ2022QN02)。

摘　　要：针对石油化工、煤矿安全等领域对气体浓度宽量程检测的需求,对波长调制光谱检测气体浓度时的非线性特征进行了研究,提出仅用波长调制方法实现气体浓度的宽动态范围测量。该方法根据激光吸收光谱技术原理,对吸收项及其泰勒展开式进行分析,在小吸收度时采用线性近似,在大吸收度时采用三次多项式近似。并且使用甲烷气体(CH_(4))作为实验对象,搭建了CH_(4)检测系统,验证了该方法在气体浓度宽量程检测方面的可行性。经过实验验证,该方法能够实现4个数量级大跨度范围(1.5×10^(-6)~10000×10^(-6))的CH_(4)检测。对阈值为1000×10^(-6)(在3 m有效光程下吸收度为0.0236)以下和以上的气体体积分数分别进行检测,反演浓度和标准浓度之间均表现出良好的相关性,拟合优度均大于0.999。另外,在吸收度大于0.0236的范围内,该方法的最大测量相对误差为0.93%,绝对误差为-92.1×10^(-6)。为了验证其稳定性,对体积分数为5000×10^(-6)(吸收度为0.118)的CH_(4)进行长时间测量,并统计其反演浓度的高斯分布,经过计算得到其半峰半宽为15.9×10^(-6)。实验证明该方法突破了传统波长调制光谱只能测量低浓度的局限,在宽量程检测中获得了良好的检测结果,为气体浓度宽量程检测提供了一种新思路,同时也大大拓宽了波长调制光谱的应用范围。Objective Tunable diode laser absorption spectroscopy,a commonly used gas concentration detection technology,has the advantages of non-contact real-time measurement,high sensitivity,and strong selectivity.It includes direct absorption spectroscopy and wavelength modulation spectroscopy.Compared to direct absorption spectroscopy,wavelength modulation spectroscopy technology has a strong anti-interference ability,higher sensitivity,and lower detection limit;it has been widely used in environmental monitoring,industrial gas detection,combustion diagnosis,and other fields.However,real-time wide-range detection of gas concentration has increasingly become a necessity.For example,the volume fraction of methane in coal mines and petrochemical pipelines varies from 0%to 100%,and the water vapor in air fluctuates significantly.Therefore,there is an urgent need for a new method for wide-range detection of gas concentration in petrochemical pipelines,coal mines,and other fields.Methods To meet the requirements of wide-range detection of gas concentration in many fields,this study utilizes the high sensitivity characteristics of wavelength modulation spectroscopy,examines the nonlinear characteristics of wavelength modulation spectrum(WMS-NL),and then achieves high sensitivity and wide range detection of gas concentration using the wavelength modulation method.According to the principle of laser absorption spectroscopy,the Taylor expansion of the absorption term is analyzed.Specifically,linear approximation and cubic polynomial approximation of the Taylor expansion are adopted at low concentration(low absorbance)and high concentration(high absorbance),respectively.Moreover,methane(CH_(4))is taken as an example to verify the feasibility of this method in the wide-range detection of gas concentration.Additionally,combined with the three parameters of absorption line intensity,effective optical length,and gas concentration,the specific details of the method are described based on the calculation of the absorbance of CH_(4).Resu

关 键 词：光谱学 波长调制光谱 非线性特征 甲烷气体(CH_(4)) 宽量程检测 

分 类 号：O433.1[机械工程—光学工程]