基于TDLAS的近红外甲烷高灵敏检测技术  

Near-infrared Methane Gas Detection Technology Based on TDLAS with High Sensitivity

作　　者：刘海芹 徐睿 王振翔 赵天琦 赵春柳 石岩[1,2] 陈亮 LIU Haiqin;XU Rui;WANG Zhenxiang;ZHAO Tianqi;ZHAO Chunliu;SHI Yan;CHEN Liang(College of Optical and Electronic Science and Technology,China Jiliang University,Hangzhou 310018,China;Key Laboratory of Optical Sensing&Image Metrology for State Market Regulation,China Jiliang University,Hangzhou 310018,China)

机构地区：[1]中国计量大学光学与电子科技学院,杭州310018 [2]中国计量大学国家市场监管重点实验室(光传感与图像计量),杭州310018

出　　处：《光子学报》2024年第3期243-250,共8页Acta Photonica Sinica

基　　金：国家市场监管总局科技计划项目(No.2022MK218);浙江省属高校基本科研业务费专项资金(No.2021YW19)。

摘　　要：为增强甲烷气体检测技术的气体吸收率,提高检测灵敏度,利用可调谐二极管激光吸收光谱技术,采用中心波长为1 653.7 nm的分布反馈激光器作为光源,研制了有效光程为14.5 m的Herriott型气体吸收池,并采用波长调制光谱法进行甲烷气体浓度检测。结果表明,二次谐波峰值信号与甲烷气体浓度成较强的线性关系,线性度为0.998 52,检测下限为4.82 ppm;初始积分时间为1 s时的Allan方差为6.37 ppm;积分时间到112 s时,Allan方差为427 ppb,检测灵敏度为4.27×10^(-7)。In order to achieve the detection of methane gas concentration and monitoring of methane leakage,and to improve the monitoring efficiency and accuracy,a high sensitivity near-infrared methane gas detection technique based on the Tunable Diode Laser Absorption Spectroscopy(TDLAS)technology is proposed.As an absorption spectroscopy technology,TDLAS is based on the Lambert-Beer law.When the emission laser makes contact with gas molecules,the gas molecules will absorb the laser energy if the wavelength of the laser coincides with the absorption line of the gas molecule.And it is known that the absorption rate of gas is directly proportional to the effective absorption distance.A larger attenuation of laser intensity tends to produce a stronger TDLAS sensor signal.Therefore,it is necessary to increase the amount of light intensity attenuation by using a long optical path gas cell.At the same time,in order to improve the measurement sensitivity and detection limit of the system,the system uses a self-developed gas absorption cell.Simulation design of Herriott-type gas absorption cell uses TracePro optical simulation software.Under the consideration of no excessive interference,uniform spot distribution,and reasonable angle between incident and outgoing rays,two concave spherical mirrors with a diameter of 50.8 mm are designed to form a Herriott absorption cell with a cavity length of 220 mm.The system adjusts the current injected into the Distributed Feedback(DFB)laser to make its output central wavelength at 1653.7 nm and serve as the detection light source of CH4.The thermo electric cooler temperature control circuit adjustes the temperature stability of the laser and is used to operate the laser at 26℃.The lock-in amplifier generates low frequency sawtooth wave signal and high frequency sine wave signal.The two signals are superimposed by the adder.The emitted laser light is absorbed by the measured gas and emitted from the end of the gas chamber to the photodetector.The photodetector converts the optical signal i

关 键 词：可调谐二极管激光吸收光谱 甲烷气体检测 波长调制法 高灵敏 Herriott腔 

分 类 号：O433[机械工程—光学工程]