Temperature Measurement Based On Gaseous Spontaneous Rayleigh-Brillouin Spectrum

Atmospheric temperature is one of the most important meteorological parameters in atmospheric science research.With the rapid development of atmospheric detection technology,Rayleigh-Brillouin scattering(RBS)laser detection technology has become an important non-invasive measurement method,which has been successfully applied in various fields such as meteorology,ocean and geology.It is expected to be a temperature diagnosis technology,which is of great significance for the accurate measurement of modern aeroengine combustion chamber and tail flame temperature.Firstly,based on the S6 model,the influence of pressure change on the spontaneous RBS line at the temperature of 298 K and the influence of temperature change on the RBS line at the pressure of 3 atm are simulated.The simulation results show that the pressure mainly affects the intensity of Brillouin peak and Rayleigh peak,while the temperature mainly affects the Brillouin frequency shift.The effect of the pressure on the RBS line is studied by using the designed gas spontaneous RBS detection system to measure the spontaneous RBS line in nitrogen with the 90° scattering angle at the pressure of 1-8 atm and the temperature of 296 K.The experimental results show that the pressure retrieval based on RBS line is feasible,and the S6 model can describe the spontaneous RBS line better.Secondly,the effect of the errors of the line width of the Fabry-Perot interferometer(FPI)instrument function,scattering angle between scattered light and incident light,the gaseous bulk viscosity,pressure and Mie scattering mainly caused by aerosol on temperature retrieval are studied by simulation at the temperature of 298 K and the pressure of 0.2-8 atm.In addition,the spontaneous Rayleigh-Brillouin scattering experiment with a 90° scattering angle in nitrogen is performed at the temperature of 298 K and the pressure ranging from 0.7 to 7 atm.The temperature is determined after parameters optimization.The results show that the experimental results are in good agreement with the conclusions of the simulation.This study has important reference significance for achieving high-precision absolute detection of temperature under different pressure conditions and accurately analyzing the gas state.Finally,the V3 model and the G3 model are compared with the spontaneous RBS spectra which is simulated based on the S6 model under the temperature of 298 K and the pressure of 1-8 atm.In addition,the spontaneous RBS line of nitrogen with Mie scattering at different temperatures(292-298 K)and different pressures(4-7 atm)are measured,and the measured lines are fitted by the S6 model,the V3 model and the G3 model to obtain temperature information respectively.By using the V3 model and the G3 model,the Brillouin frequency shift can be directly measured,but the accuracy is slightly low.However,the retrieval temperature based on the S6 model requires the known pressure parameter.Therefore,the V3 model and the G3 model are more suitable for the temperature retrieval of unknown environmental pressures.