基于多光谱融合的氨气和一氧化氮浓度测量方法研究

发布时间：2018-05-20 02:21

本文选题：可调谐半导体激光吸收光谱技术 + 差分吸收光谱技术　；参考：《东南大学》2016年硕士论文

【摘要】：可调谐半导体激光吸收光谱(TDLAS)技术是一种灵敏度高、时间响应快、非侵入式的气体检测技术,在污染气体的检测方面具有广阔的应用前景。差分吸收光谱(DOAS)技术具有结构简单、精度高、多组分实时检测等优点,广泛应用于烟气组分浓度的检测。由于NO、NH3气体的吸收光谱在紫外波段会产生交叠,目前采用单一的技术无法实现NO浓度的准确测量。因此,如何综合利用紫外光谱(基于DOAS技术)和近红外激光光谱(基于TDLAS技术)的多光谱融合信息,实现多组分气体浓度的同时测量是当前烟气测量研究领域的一个热点。论文围绕低浓度NH3测量以及NH3对NO浓度测量的干扰问题,开展了全面的理论分析与实验研究。对已有的TDLAS技术和DOAS技术进行深度解析,提出了基于紫外光谱和近红外激光光谱的融合模型,完善了多种补偿模型中的数据库,有效的消除了气体组分间的干扰。本文的主要工作有：将免标定波长调制方法首次应用于NH3气体浓度测量。a)理论分析了基于免标定波长调制的气体浓度测量方法,利用测量得到的背景光强来仿真透射光强,采用虚拟数字锁相和低通滤波器分析测量和仿真的透射光强信号,得到所需的谐波信号。b)建立了NH3气体浓度实验测量系统,开展了针对不同浓度NH3气体浓度测量的实验研究。实验结果表明：测量值与标气值基本吻合,实现了NH3浓度的准确测量。采用DOAS技术实现了NO气体浓度的测量。a)针对饱和吸收与测量系统分辨率等引起的NO非线性吸收以及温度对NO吸收截面的影响。研究了不同浓度下分子数密度比与测量浓度的关系,得到NO的非线性补偿函数,利用不同温度下分子数密度比与温度的关系,获取温度干扰补偿函数。b)搭建实验平台,对NO气体浓度进行了测量。实验结果表明采用提出的补偿函数可以很好地修正非线性和温度变化带来的干扰。提出了基于紫外和近红外激光光谱的融合模型,有效的消除了气体组分之间的干扰。a)分析了在不同浓度与温度下NH3对NO浓度测量的干扰规律,得到NH3干扰下的补偿函数,建立了基于紫外与近红外激光光谱的融合模型。b)开展了针对NH3和NO混合气体浓度同时测量的实验研究。结果表明：使用多光谱融合模型,可以有效的消除NH3对NO浓度测量的影响,实现NH3与NO气体浓度的同时准确测量。
[Abstract]:Tunable Semiconductor Laser absorption Spectroscopy (TDLAS) is a kind of non-invasive gas detection technology with high sensitivity, fast time response, and has a broad application prospect in the detection of contaminated gases. Differential absorption Spectroscopy (DOAS) technique has the advantages of simple structure, high precision and multicomponent real-time detection, so it is widely used in the detection of smoke component concentration. Since the absorption spectra of NO-NH _ 3 gas overlap in the ultraviolet band, it is not possible to accurately measure the concentration of no by using a single technique. Therefore, how to integrate the multi-spectral fusion information of ultraviolet spectrum (based on DOAS technology) and near-infrared laser spectrum (based on TDLAS technology) to realize the simultaneous measurement of multi-component gas concentration is a hot spot in the field of smoke measurement. In this paper, the theoretical analysis and experimental study of low concentration NH3 measurement and NH3 interference to no concentration measurement are carried out. Based on the deep analysis of the existing TDLAS and DOAS techniques, a fusion model based on ultraviolet spectrum and near infrared laser spectrum is proposed, which improves the database of various compensation models and effectively eliminates the interference between gas components. The main work of this paper is as follows: the method of non-calibrated wavelength modulation is applied to the measurement of NH3 gas concentration for the first time. The method of measuring gas concentration based on non-calibrated wavelength modulation is analyzed for the first time. The background light intensity is used to simulate the transmitted light intensity. Using virtual digital phase-locked and low-pass filter to analyze and simulate the transmitted light intensity signal to get the needed harmonic signal, the experimental measurement system of NH3 gas concentration is established, and the experimental research on the measurement of NH3 gas concentration with different concentrations is carried out. The experimental results show that the measured values are in good agreement with the standard gas values, and the accurate measurement of NH3 concentration is realized. The nonlinear absorption of no caused by saturation absorption and the resolution of measurement system and the effect of temperature on the absorption cross section of no are realized by DOAS technique. The relationship between the molecular number density ratio and the measured concentration at different concentrations is studied, and the nonlinear compensation function of no is obtained. Using the relationship between the molecular number density ratio and the temperature at different temperatures, the compensation function of temperature interference is obtained to build the experimental platform. The concentration of no gas was measured. The experimental results show that the proposed compensation function can be used to correct the nonlinearity and the disturbance caused by temperature change. Based on the fusion model of ultraviolet and near infrared laser spectra, the interference between gas components is effectively eliminated. The interference law of NH3 to no concentration measurement at different concentrations and temperatures is analyzed, and the compensation function under NH3 interference is obtained. Based on the fusion model of ultraviolet and near infrared laser spectra, the experimental study on simultaneous measurement of the concentration of NH3 and no mixtures was carried out. The results show that the multi-spectral fusion model can effectively eliminate the influence of NH3 on the measurement of no concentration and realize the accurate measurement of the concentration of NH3 and no at the same time.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：X831

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