RAMAN and RAYLEIGH Thermometries in Flames

Abstract

The use of RAYLEIGH and vibrational RAMAN spectroscopic techniques in flame temperature measurements is examined. The experimental apparatus consisted of an Argon-ion laser (1.2 W at 488nm), a double monochromator, a recording system (photon-counter or data recorder), and a pair of multi-pass reflectors, which were used when high scattering light intensity was required. In an experiment using the RAMAN spectroscopy, an H₂ diffusion flame has been in- vestigated. The results of N₂ and O₂ vibrational temperature measurements are presented, and the temperature profiles for N₂ are further examined in comparison with the profiles determined through thermocouple measurements. CH₄-air premixed flames have been studied for the assessment of RAYLEIGH scattering spectroscopy. Time-averaged temperature profiles of a laminar flame obtained by this technique are compared with the results of thermocouple measurements. RAYLEIGH thermometry has also been applied to a turbulent flame, demonstrating that this technique provides reliable temperature determination with sufficient time resolution.