Raman-scattering gas temperature measurements in particle-laden flows

The feasibility of making time-averaged Raman-scattering temperature measurements in highly luminous flows has been investigated in tests on the Sandia Atmospheric Combustor Exhaust Simulator facility (ACES). In these experiments the diluted exhaust stream from a methane-burning combustor was seeded with 5 μm diameter fly ash particles. Tests were run at temperatures ranging from 900 to 14500K at particle densities up to 6000 particles/cm3. Measurements were made using a pulsed argon-ion probe laser and a gated detection system for enhancement of signal-to-background ratio. Scans of the Stokes Q-branch vibrational Raman spectrum of nitrogen were fit by calculated spectra in order to determine temperature. The Raman-scattered signal was small but measurable in all cases. There was no apparent laser-induced interference from either fluorescence or particle incandescence. Good agreement between Raman-scattering temperature measurements and radiation-corrected thermocouple mearurements was obtained