水和二氧化碳的激光吸收光谱研究

发布时间：2018-01-01 08:12

本文关键词：水和二氧化碳的激光吸收光谱研究　出处：《太原科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：工业革命以来,由于人类大肆向空气中排放二氧化碳等温室气体,已造成全球气候变暖,极地冰川融化,极端天气频发等一系列问题。如何减少温室气体的排放成为全人类亟待解决的问题,而温室气体的浓度监测是节能减排的重要环节之一。用于气体检测的方法可分为传统法和激光光谱法,与传统的气体检测方法相比,激光吸收光谱法有无需采样进行检测,能直接实时监测、操作简便、实验过程易于控制等优势,并具有较高的探测灵敏度,因此是目前应用研究的热点之一。本文在对吸收光谱技术理论研究的基础上,采用长光程吸收和谐波检测技术,搭建了气体检测实验系统,进行二氧化碳和水的吸收光谱研究,并对差分吸收探测电路提出了改进。理论上,研究谐波信号与调制幅度的关系,通过理论计算,得出二次谐波峰值与气体浓度成一定的线性关系。本文采用归一化的二次谐波信号实现免校准测量,此方法可以消去光源波动以及其它光电器件的电流漂移等不稳定性噪声。对激光器的温度和电流调谐特性进行试验,分析频率调制幅度对谐波信号的影响,调节实验参数,在波形最优的情况下进行实验。利用长光程波长调制光谱技术测量了不同浓度的二氧化碳,分别获取其直接吸收以及一次、二次谐波信号。利用Origin软件对采集到的信号进行去背景、拟合等处理。由归一化的二次谐波与气体浓度的关系,计算气体浓度。分析计算浓度与标准浓度的偏差,检验气体检测系统的可行性。并对水分子在12252-12312 cm-1这个弱吸收波段的吸收谱线进行测量,共测到了43条吸收谱线,对测得的数据进行拟合,得到伏格特线宽和洛伦兹线宽,与Hitran谱线数据库的数据吻合较好;将各拟合谱线的中心频率和Hitran库进行比对,偏差较小,验证系统具有较好的探测精度。
[Abstract]:Since the Industrial Revolution, human beings have emitted greenhouse gases such as carbon dioxide into the air, which has caused global warming and melting of polar glaciers. How to reduce greenhouse gas emissions has become an urgent problem for all mankind. The concentration monitoring of greenhouse gas is one of the important links of energy saving and emission reduction. The methods used in gas detection can be divided into traditional method and laser spectrum method, compared with the traditional gas detection method. Laser absorption spectrometry has the advantages of no sampling, direct real-time monitoring, simple operation, easy control of the experimental process, and high detection sensitivity. Therefore, it is one of the hotspots of application research. Based on the theoretical research of absorption spectrum technology, this paper builds a gas detection experimental system using long optical path absorption and harmonic detection technology. The absorption spectrum of carbon dioxide and water is studied, and the differential absorption detection circuit is improved. Theoretically, the relationship between harmonic signal and modulation amplitude is studied and calculated theoretically. The linear relationship between the second harmonic peak and the gas concentration is obtained. In this paper, the normalized second harmonic signal is used to realize the calibration free measurement. This method can eliminate the unstable noise such as the fluctuation of light source and the current drift of other optoelectronic devices. The temperature and current tuning characteristics of the laser are tested and the influence of the amplitude of frequency modulation on the harmonic signal is analyzed. By adjusting the experimental parameters, the experiment was carried out under the condition of optimal waveform. Different concentrations of carbon dioxide were measured by long path wavelength modulation spectroscopy, and the direct absorption and one time absorption were obtained respectively. The second harmonic signal is processed by using Origin software to remove background and fit the signal. The relationship between the normalized second harmonic and gas concentration is discussed. Calculate the gas concentration. Analyze the deviation between the calculated concentration and the standard concentration. To test the feasibility of the gas detection system, and to measure the absorption lines of water molecules at 12252-12312 cm-1, a total of 43 absorption lines have been measured. By fitting the measured data, the volt linewidth and Lorentz linewidth are obtained, which are in good agreement with the data of Hitran spectral line database. The center frequency of each fitting line is compared with the Hitran library, the deviation is small, and the system has good detection accuracy.
【学位授予单位】：太原科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X831;TN249

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