A numerical spectroscopic technique for analyzing combustor flowfields

A computer program which calculates the ultraviolet emission and absorption spectra of OH is presented for use in conjunction with numerical programs which predict combustor flow field properties. Spatial distributions of OH number density and temperature, resulting from analytical flow field calculations, are used as input data for calculating the absolute intensities of the spectra. Of particular interest is the ability to calculate the shapes of the intensity envelopes associated with the low resolution slit settings of a given spectrometer. Comparisons are made with actual spectral data obtained with various degrees of spectral resolution. The computer program is also used to generate graphical inversion techniques for analyzing experimental spectra. An example is given in which one such graphical technique is used to obtain average temperatures and number densities along the axis of an axisymmetric duct containing a supersonic diffusion flame. Another example is presented to demonstrate the manner in which a second inversion technique can be used to obtain radial profiles of temperature and OH number density from radial scanning of an axisymmetric combustor flow field. Two cases involving thermodynamic nonequilibrium are also discussed, one of which involves a hot vibrational band and the other an electronic nonequilibrium.