The spontaneous raman scattering technique applied to nonpremixed flames of methane

Simultaneous space- and time-resolved measurements of the concentrations of CH₄, O₂, N₂, H₂O, H₂, CO, and CO₂ have been made using spontaneous Raman scattering, in the blue regions of CH₄ turbulent nonpremixed flames. The temperature is measured from the Rayleigh scattered signal. A "fluorescence" interference, which is broadband and contaminates in varying degrees the Rayleigh and all the Raman lines, is believed to be due to a number of molecules or flame radicals, including C₂ and CN or even incandescence of small particle nuclei. The "fluorescence" has been monitored at a bandhead of C₂ (516.5 nm) and its effect reduced by placing a Polaroid filter at the entrance slit of the spectrometer. The remaining "fluorescence" has been corrected for, using correction curves generated from measurements made in a laminar counterflow CH₄ diffusion flame and a diluted CH₄ N₂ = 1 2 (by vol.) laminar diffusion flame. Measurements of CO and CO₂ are not reliable in the rich regions of the flame where the "fluorescence" is intense. With minor modifications to the optical system, CO and CO₂ could also be measured with acceptable accuracy in regions of intense "fluorescence" and the "fluorescence" correction further refined. This work is considered to be an important extension of the applications of spontaneous Raman scattering as a measurement technique in flames.