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ICHMT DIGITAL LIBRARY ONLINE

ISSN 961-91393-0-5

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Year 1995

• 1Radiative Transfer I
Proceedings of the First International Symposium on Radiation Transfer - Kusadasi, Turkey, August, 1995

800 pages

Volume price - $192.00

DETAILED SPECTRAL RADIATION CALCULATIONS FOR NONHOMOGENEOUS SOOT/GAS MIXTURES BASED ON A SIMULATED ETHYLENE JET DIFFUSION FLAME

Pei-Feng Hsu
Mechanical and Aerospace Engineering Department, Florida Institute of Technology, USA

Jerry C. Ku
Mechanical Engineering Department, Wayne State University, Detroit, Michigan, USA

ABSTRACT

The purpose of this paper is to study the effects of the radiative properties of soot particles and CO₂ and H₂O gases on detailed radiative heat transfer calculations using a simulated ethylene jet diffusion flame. The YIX method is applied to calculate the radiative transfer quantities over the spectral range of 1-20 μm in a finite cylindrical enclosure with distributions for flame temperature, soot volume fraction, and gas concentrations precalculated from a modeling analysis. Scattering from soot particles is neglected. Soot only, gases only, and the combined cases are examined. The Rayleigh solution is used to calculate the absorption coefficient spectra for soot aggregates. Soot complex refractive index spectra are generated from the Drude-Lorentz dispersion model based on three frequently cited dispersion parameter sets. Results from these three dispersion parameter sets show that the difference in maximum flux divergence is 45% and that the difference in maximum radial flux is 62%. Thus current uncertainties about soot spectral refractive indices are the main limitation on accurate estimates of the radiation heat transfer from sooting combustion systems. The exponential-wide-band model is used to calculate gas absorption coefficient spectra. Generally, radiation from soot is two to three times of that from gases. Therefore both soot and gas contributions are significant, and accurate models for gas absorption coefficient spectra are crucial. More than 95% of the total gas radiation comes from the 2.73 and 4.3 μm bands of CO₂ and from the 2.67 μm bands of H₂O. The 6.3 μm H₂O band can be added to essentially account for all gas radiation, and other gas absorption bands make very little contribution. Practically, for the type of flames considered here, it is concluded that spectral contributions from beyond the 5 μm range can be neglected with less than 5% loss of accuracy in calculating the total radiative flux and its divergence.