Research On Hardware System Of Spatial Anti-radiation Fire Detection Of Aircrafts Cargo Based On TDLAS

Aircraft has gradually become an important way for people to travel,but the frequent occurrence of false alarms in aircraft fire detection devices poses a huge safety hazard to passengers.Therefore,it is imperative to improve the fire detection devices on the aircraft.Tunable diode laser absorption spectroscopy?TDLAS?is an emerging gas detection technology with high detection accuracy,high reliability,and good stability for operation in harsh environments.The application of TDLAS technology in fire detection to detect gas and toxic gases released by combustion has a very good application prospect.Since the combustion generates a large amount of CO₂ gas,the detection of CO₂ gas concentration is used as the main criterion for the fire alarm.Beer-Lambert's law,on the principle of gas absorption spectroscopy and the theoretical basis of TDLAS technology for detecting gas concentration is elaborated.The formula for calculating the line intensity is discussed in detail.The expressions of the three line types and the reasons for the changes are introduced.The influence of temperature and pressure on the line type and line width is discussed.The principles of wavelength modulation technology and second harmonic detection technology are further elaborated.On the basis of theory,a complete TDLAS-based gas concentration detection system was constructed,and suitable lasers and photodetectors were selected,and an open optical path based on aircraft cargo bay was designed.The FPGA-based signal generator design,schematic design of the drive circuit,temperature control circuit and phase-locked amplifier circuit are realized,and the simulation and analysis of each unit circuit are carried out.A detailed test analysis of the temperature and current tuning characteristics of the laser was performed.The second harmonic peak corresponding to different concentrations of CO₂ gas was tested by the built hardware system,and the detection of CO₂ gas concentration was initially realized.