Study On The Characteristics Of Harmful Gas Detection System In Aircraft Cabin Based On Laser

With the development of science and technology,airplane has gradually become one of the important means of transportation travelling.The leakage of harmful gas during flight would lead to an increase in the contents of pollutants in the cabin,which would seriously affect human health.Therefore,research on the monitoring of air pollutants in the cabin is crucial.As high-resolution absorption spectroscopy technology,the technology of TDLAS is high monochromaticity,extremely small linewidth,strong tunability,and little external interference,which can easily identifies different molecules from mixed gas molecules Ignore the interference of other spectral lines.This technology has been extensively used in many fields,but the research on aircraft air quality detection is still blank.In this thesis,laser cabin air quality detection technology is studied,the parameters that affect the stability of the detection system are studied,and the placement of the laser is explored.This thesis discusses the following aspects:（1）The thesis discussed the basic principles of TDLAS gas detection technology,and deduced the wavelength modulation technology and second harmonic extraction technology.The absorption line of the CO₂ was analyzed,and 1578nm was selected as the CO₂ absorption line.（2）The simulation model of TDLAS detection system was designed and built.The influence of temperature,pressure and other parameters on absorption cross section,absorption coefficient and spectral line width were analyzed by using HITRAN molecular database.Finally got the suitable temperature and pressure value.（3）The temperature characteristics of the laser in the detection system were simulated and analyzed,including the influence on output wavelength,power and threshold current.Reasonable selection of these parameters can ensure the sensitivity of the detection system.（4）Because of the randomness of people,the CO₂ distribution of the cabin is also highly uncertain.In this thesis,a half-load cockpit was randomly selected for model analysis to explore the CO₂ concentration distribution of different section locations.With the combination of image processing technology,the maximum concentration can be located,and the absorption level of weak absorption can be increased when the laser passes through the maximum concentration,so as to improve the accuracy of the detection system.