SOOT AND RADIATION IN COMBUSTING BOUNDARY LAYERS

Abstract Classical studies of boundary layer diffusion flames have neglected radiation. As a first step toward a better understanding of radiation heat transfer in fires, a numerical solution is obtained for a steady, laminar, radiating, combusting, boundary layer over a pyrolyzing fuel slab. Two Shvab-Zeldovich coupling functions are needed in the analyses, which treat forced and free flows separately. For these laminar systems, an optically thin approximation for radiation is valid, based on previous measurements of soot volume fraction in combusting boundary layers. As in non-radiating combustion, the mass transfer number, B, and the mass consumption number, rp, are the dominant parameters controlling the local pyrolysis rate and the excess pyrolyzate, respec- tively. The dominant role of the dimensionless heat of combustion, Dc, in determining the flame temperature makes it a significant parameter in radiating systems. The surface temperature and emissivity characterize the surface emission, which can...

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