随着我国经济社会的高速发展，近年来火灾重特大事故频发，后果严重，给国家和人民财产造成巨大损失，如何实现火灾事故的早期准确预警是亟待解决的关键技术问题。在发生火灾时，常常会出现一些特征明显，规律突出的气体，比如：CO、CH4、C2H2、C2H4等，往往把这些气体称之为标识性气体。通过高精度测量标识性气体的浓度可以实现对火灾的早期预警，能够从源头减少人员伤亡以及降低财产损失，避免重特大事故的发生。可调谐激光吸收光谱技术是目前最先进的气体探测方法之一，它具有测量精度高、响应速度快、不受背景气体干扰等优点，在近二十年得到了迅速的发展，已成功应用于石油化工、环境监测、工业过程分析等诸多领域。以可调谐二极管激光吸收光谱技术(Tunable diode laser absorption spectroscopy，TDLAS)为基础，进行火灾早期预警领域中多组分气体检测技术的研究，可以为火灾事故精准预警、事故态势研判提供量化科学依据，有望降低重特大火灾事故，具有极高的科研价值和巨大的应用前景。本文从火灾预警应用场景需求出发，选取 CO、CH4和 C2H2三种常见典型火灾标识性气体作为研究对象，对谱线选择、测量方案、光学系统设计和数据处理算法进行研究，成功开发出火灾早期预警多组分气体检测系统。本文主要内容如下：

1. 概述了课题研究意义以及研究现状，介绍了几种应用范围较为广泛的气体检测技术，详细阐述了 TDLAS 技术的多处优点，以及在火灾早期预警的研究现状。

2. 介绍了 TDLAS 技术的基本理论和方法，介绍了 Beer-Lambert 定律、线强度和吸收谱线线型函数，阐明了直接吸收光谱技术，基于该技术设计并搭建了 C2H2测量系统，选用500 ppm·m C2H2标准气室开展实验研究，该实验系统测量到的 C2H2标准气室浓度为 493.7 ppm·m，误差为 1.26 %。并介绍了锁相放大器的基本原理、谐波检测原理以及波长调制光谱技术原理，进行了 CO、CH4和 C2H2三种气体的吸收谱线模拟，并说明了波长选择的原则。

3. 为进一步提高系统测量精度，采用波长调制光谱技术结合 Herriott 型多反气室和新型密集光斑多反气室的实验方案，设计并开展了 CO、CH4和 C2H2三种典型火灾标识性气体的高精度测量，并将三个多反气室测量系统集成为一个多组分气体检测模块，在实验室内模拟燃烧场景，进行室内环境中 CO、CH4和 C2H2三种火灾标识性气体浓度的同时监测实验，得到了不同燃烧物对应的CO、CH4和 C2H2三种火灾标识性气体浓度变化趋势图。

4. 为了更灵敏的检测到火灾标识性气体浓度的变化，实现更为早期的火灾预警，我们在第三章工作的基础上进一步增加了多反气室的光程长度。设计了两种矩阵型光斑多反气室，光程长度分别为 57.6 m 和 72 m。同样地，在实验室内模拟燃烧场景，进行室内环境中CO、CH4和 C2H2三种火灾标识性气体浓度的分别监测和同时监测实验。对应纸张、无烟炭、煤块和塑料袋四种不同的燃烧物，得到了 CO、CH4和 C2H2三种火灾标识性气体浓度随时间的变化趋势图。在分别点燃实验中四种不同可燃物的初期，有烟气产生但还没有明火时，均检测到了不同组分标识性气体浓度的变化。

综上所述，本论文开发的基于可调谐激光吸收光谱技术火灾早期预警系统，可以实现多种火灾标识性气体的高精度探测，在重特大火灾灾害智能感知和早期预警领域具有潜在的应用前景。

With the rapid development of our economy and society, fire accidents have occurred frequently in recent years with severe and serious consequences, which have caused great losses to the country and people's property. In the event of a fire, there are often some gases with obvious characteristics and prominent rules, such as: CO, CH4, C2H2, C2H4, etc., and these gases are often called identification gases. Early warning of fire can be realized through high precision measurement of the concentration of identifying gas, which can reduce casualties and property losses from the source and avoid the occurrence of major accidents. Tunable laser absorption spectroscopy is one of the most advanced gas detection methods at present. It has the advantages of high measurement accuracy, fast response speed and no interference from background gas. It has been rapid development in the past two decades and has been successfully applied in many fields such as petrochemical industry, environmental monitoring and industrial process analysis. Based on tunable diode laser absorption spectroscopy (TDLAS), the research of multi-component gas detection technology in the field of fire early warning can provide quantitative scientific basis for accurate early warning of fire accidents and accident situation research and judgment, which is expected to reduce heavy and extraordinarily large fire accidents, which has high scientific research value and huge application prospects. Based on the requirements of fire warning application scenarios, in this thesis, we select CO, CH4 and C2H2, three common typical fire identifying gases, as the research object, studies spectral line selection, measurement scheme, optical system design and data processing algorithm, and successfully develops a multi-component gas detection system for fire early warning. The main contents of this thesis are as follows:

1. The research significance and research status of the topic are summarized, several gas detection technologies with a wide range of applications are introduced, and the advantages of TDLAS technology as well as the research status of fire early warning are elaborated.

2. The basic theory and method of TDLAS technology are introduced, the Beer-Lambert law, linear intensity and absorption spectral line type function are introduced, the direct absorption spectroscopy technology is clarified, and the C2H2 measurement system is designed and built based on this technology. The 500 ppm·m C2H2 standard cell was used to carry out experimental research. The concentration of C2H2 standard chamber measured by the experimental system was 493.7 ppm·m, with an error of 1.26 %. The basic principles of phase-locked amplifier, harmonic detection and wavelength modulation spectroscopy are introduced. The absorption spectra of CO, CH4 and C2H2 gas are simulated, and the principle of wavelength selection is explained.

3. In order to further improve the measurement accuracy of the system, high-precision measurement of CO, CH4 and C2H2 are designed and carried out by combining the experimental scheme of Herriott type multipass cell and new dense spot multipass cell with wavelength modulation spectroscopy. Three multipass cell measurement systems were integrated into a multi-component gas detection module, and the combustion scene was simulated in the laboratory to carry out the simultaneous monitoring experiment of the concentrations of three fire identifying gases (CO, CH4 and C2H2) in the indoor environment. The trend charts of the concentrations of three fire identifying gases (CO, CH4 and C2H2) corresponding to different combustor were obtained.

4. In order to more sensitively detect changes in the concentration of fire identifying gas and realize earlier fire warning, we further increase the optical path length of the multipass cell on the basis of the work in Chapter 3. Two kinds of matrix type light spot multipass cell with optical path lengths of 57.6 m and 72 m were designed.Similarly, the simulation of the combustion scene in the laboratory was carried out to monitor the concentration of CO, CH4 and C2H2 in the indoor environment respectively and simultaneously. Corresponding to paper, anthracite, coal and plastic bags, the concentration trend of three fire identification gases, CO, CH4 and C2H2, was obtained over time. In the initial stage of four different combustibles in the separate ignition experiment, when there is smoke but no open flame, the change of the concentration of different components of the identifying gas was detected.

In summary, the fire early warning system developed in this thesis based on tunable laser absorption spectroscopy technology can realize the high-precision detection of a variety of fire identifying gases, and has potential application prospects in the field of intelligent perception and early warning of major and major fire disasters.

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