High-resolution spectral diagnostics in flows with mild vibrational relaxation

Results are reported from the calculation of line-by-line spectra using state densities from vibrational state relaxation calculations for CO and CO2 in an expanding flow of typical combustion gases. The relaxation calculation provides detailed state number densities independent of an assumption of temperature for the ensemble state distribution, and the spectral calculation uses these state densities directly. The spectral regions from 4.0 to 5.0 microns have been modeled; results from the region 4.55 microns where the CO and CO2 spectra overlap are examined. The effect of the relaxation on the line spectra is evident. Requirements for diagnostic instrumentation in such environments are examined.