Infrared emission from high-temperature H2O(upsilon(2)): A diagnostic for concentration and temperature

A shock tube system was used to produce known concentrations of water at combustion temperatures so that the infrared radiance from a portion of the H2O(nu(2)) band could be measured as a function of temperature and wavelength. The resulting data set was used to determine the efficacy of a spectral emission diagnostic for H2O temperature and column density at the exit plane of a supersonic combustor. Temporally and spectrally resolved, optically thin infrared emission, at 13 wavelengths between 6.5 and 9.5 mu m, was observed from shock-heated H2O/N-2, H-2/O-2/N-2, and H-2/O-2/Ar mixtures, at pressures of 1 and 5 atm and temperatures between 1400 and 3000 K. Least squares analysis of the temperature dependent intensities for each wavelength channel gave parameters that accurately describe the radiance as a function of wavelength and temperature over the entire temperature range of the measurements, The accuracy to which temperatures and H2O column densities can be determined from these parameters was then estimated, Radiometric data were compared with predictions from a widely used band model, corrections for optically thick systems were explored, and the relationship between optically thin radiance and the optical cross section produced. Column densities at which corrections for optical thickness are required were also calculated.