Characteristics of combustion and radiation heat transfer of an oxygen-enhanced flame burner

Abstract

The spectral and total radiation intensities of a methane/oxygen flame were investigated experimentally and compared with those of a methane/air flame. Different combinations of central and annular fuel-oxygen supplies were studied to find the best combination for increasing the radiation intensity. A fast infrared array spectrometer was used to measure the spectral radiation intensity in the mid-infrared range (1.3–4.8 μm). A laser-induced incandescence technique was utilized to visualize the instantaneous and average soot distribution in the flames. The results show that an oxygen-enhanced inverse diffusion flame is very effective in increasing the thermal radiation compared to a normal oxygen diffusion flame. The power spectral densities (PSD) of spectral radiation intensity in the wavelength region corresponding to soot show a Gaussian shape in the methane/oxygen flames, in contrast to a log-normal shape in the methane/air flames. The difference in the probability density functions (PDFs) is caused by a more uniform spatial distribution of soot in the methane/oxygen flames compared to that in the methane/air flames. The PSDs of the spectral radiation intensities for methane/air flames show buoyant flickering while those of methane/oxygen flames do not for the present operating conditions.