Radiative Emission and Reabsorption in Laminar, Ethylene-Fueled Diffusion Flames Using the Discrete Ordinates Method

Thermal radiation from laminar, sooting, coflow diffusion flames at atmospheric pressure has been studied computationally as a function of ethylene fuel dilution by nitrogen. These flames had previously been investigated using laser diagnostics and thermocouple-gas sampling probe techniques, and the measured soot levels had been satisfactorily predicted by a sectional soot kinetics model. In this work, the discrete ordinates method for solution of the equation of radiative transfer in axisymmetric cylindrical coordinates has been coupled to the flow’s energy conservation equation through the calculated divergence of the net radiative flux. Two self-consistent models for the absorption/emission of radiation by soot, CO2, H2O, CO, and ethylene were considered: the Planck mean model and one based on narrowband, wavelength-dependent absorption. The wavelength-dependent calculation was found to predict much more substantial reabsorption effects; we conclude that the Planck mean model inadequately characterizes...