Spectral Identification Of Particulate Matter In High Temperature And High Velocity Flow Field

The identification of particulate matter type parameters in high-temperature and high-speed flow field is helpful to provide reference for fault diagnosis and traceability in high-altitude simulated environment.The identification of particulate matter type parameters in high-temperature and high-speed flow field is helpful to provide reference for fault diagnosis and traceability in high-altitude simulated environment.Therefore,it is particularly important to explore a method based on spectral detection technology for qualitative analysis of high-temperature and high-speed flow fields and abnormal particles.In this paper,the simulation of high temperature and high speed flow field is realized by propane/compressed air,and Fe,GH4169 alloy,C and TiO₂particles are taken as the research objects,and the laser-induced breakdown spectroscopy technique is used to verify the feasibility and effectiveness of the qualitative analysis of particles in high temperature and high speed flow field.In this paper,the domestic and foreign status,measurement characteristics and application fields of laser-induced breakdown spectroscopy（LIBS）are introduced.The electron temperature and of nanosecond laser induced aluminum plasma were calculated and analyzed.A laser-induced breakdown spectroscopy experimental device based on a propane/compressed air combustion platform was built.The diameter of the tail jet flame generated by the high temperature and high speed flow field is about 70mm,and the axial length of the flame is 400mm.The temperature field obtained by infrared camera temperature measurement and PIV velocity measurement is about 1200～1600K,and the flow field velocity is 130～230m/s.After debugging,the laser light path composed of the laser（532nm）and optical components can focus the laser spot with a diameter of 20um at about 100mm of the flame axis,which ensures the stability of the particle-induced breakdown spectroscopy experiment.The calibration of the spectral line wavelength of the grating spectrometer is completed by using the calibration light source,and the measurement accuracy can reach 0.06nm.The spectral line wavelength information of the tail jet flame in the high temperature and high velocity flow field was measured;the wavelength distribution characteristics of the flame components CH^*,C₂^*and H₂O were obtained,and the mechanism of free radical reaction was discussed.The relationship between spectral line intensity and pressure ratio is obtained.Qualitative analysis of spectral line characteristics of particulate matter based on spectral data.A suitable analytical line is selected to solve the electron temperature of the particle plasma.The effects of particle size,particle flow velocity,and flame breakdown spectrum on spectral line intensity in high-temperature and high-speed flow field were analyzed.The mathematical statistics law of particulate matter in high temperature and high speed flow field is expounded.The feasibility and limitations of applying LIBS technology to identify particle element species in high temperature and high velocity flow field are discussed.How to improve the efficiency and accuracy of particle spectroscopic detection in high temperature and high speed environment is discussed and prospected.