Time-resolved Measurement Of Temperature In Combustion Field By CPP Femtosecond Single-shot CARS Spectroscopy

CARS spectroscopy is a widely recognized temperature measurement technique.Nanosecond CARS spectrometry thermometry technology is relatively mature,but due to its inherent inelastic collisions of molecules and low frequency,it is no longer suitable for rapidly changing combustion fields such as high temperature turbulence flame.Facing of the demand for measuring complex combustion fields temperature,it is proposed to use a single-shot CARS to measure the combustion temperature,and the chirped-probe pulse femtosecond coherent anti-Stokes Raman scattering(CPP fs CARS)temperature measurement technology came into being.In just over the past decade,the CPP fs CARS technique has been developed for determining single-shot point temperature measurements.By continuously improving CPP fs CARS theory research,modifing the fitting algorithm and optimizing the experimental system,the CPP fs CARS technology used to measure field temperature changed from steady gas cell to high temperature turbulence burner.Now,It has achieved the time-resolved measurement of the temperature of the turbulent burner at high temperatur and increased the accuracy of the temperature measurement.In this paper,CPP fs single-shot CARS spectroscopy is used to measure the temperature of steady gas and unsteady combustion flame.Research work mainly includes the following aspects.(1)Establish the theoretical model of CPP fs CARS spectral.The CARS signal intensity was deduced from the polarization of the medium.And by building the nitrogen molecular response model as well as the three beam electric field model,CPP fs CARS spectral model was constructed.(2)Establish the CPP fs single-pulse CARS system to time-resolved measure temperature,which mainly includes a steady gas thermometry system and unsteady combustion flame system.(3)A simulation study of the fitting program was performed.Simulated the parameters of the theoretical model and the molecular response models at different temperatures.The fitting process for obtaining the optimal parameters of the theoretical spectrum and the optimal temperature of the experimental data is given.(4)The CPS fs single-pulse CARS was used to measure the temperature of the steady gas and the unsteady combustion flame at 290K-1050 K.The presicion of temperature measurement was great and the result accuracy batter than 1.5%.The time resolution of temperature measurement reached 0.01 s.