A numerical study on the soot-free conditions of spherical diffusion flames
Published by (Combustion Institute Central States Meeting, April 22-24, Dayton, OH 2012)
Authors: Hamed (Mahmood) Dehnavi. Published April 23, 2012
The soot free conditions of transient ethylene/oxygen/nitrogen spherical diffusion flames supported by a porous spherical burner were investigated numerically using detailed chemistry and transport coefficients. Radiative heat loss from the flame is included with the heat loss rate described by a statistical narrow-band model and a discrete ordinates method. The computations simulate soot free ethylene flames at atmospheric pressure, which were observed experimentally using the NASA GRC 2.2-s drop tower. These flames are initially sooty but turn soot-free between 1-2 s after the ignition. Fifteen normal (fuel flowing into the oxidizer) and inverse (oxidizer flowing into fuel) flames were modeled. The fuel and oxidizer concentrations are chosen such that a broad range of adiabatic temperatures (2251-2628K) and mixture fractions (0.317-0.754) are included. The results indicate that the flames are soot free when there is no region where the carbon to oxygen atom ratio exceeds 0.47 and the temperature exceed 1425K. These values are only slightly different from those recently published for similar flames.
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