Experimental Investigation on the Effect of Oxygen Enhancement on Radiation Distribution in Inverse Diffusion Flames

Abstract

Intense investigations have been focused on radiative heat transfer in oxygen-enhanced inverse diffusion flames since it plays a significant role not only in fundamental combustion research, but also in terrestrial and spacecraft fire safety study. To investigate the characteristics of the radiative heat transfer, a calibrated mid-infrared camera was used to acquire images of radiation intensity including soot and carbon dioxide in the 2–5μm wavelength range. The mole fraction of oxygen in the oxidizer varied from 21% to 100% with co-flowing inverse flame burner used to stabilize the flames. The characteristics of axial and radial radiation intensity distribution in different oxygen enhanced conditions are compared and analyzed. The results indicated that oxygen enhancement broadens the radial range of inner blue reaction zone and stretches the axial height of the plume zone. Similar to radial peak radiation intensity value and the growth rate of radial radiation intensity in different axial heights from X = 1D to X = 3D (X: axial height above the burner along the flame centerline; D: diameter of oxidizer exit), the peak value of radiation intensity and the growth rate of radiation intensity along the flame centerline both have a positive linear relationship with the oxygen mole fraction in the oxidizer.