The effect of very low speed forced flows on the size and shape of a diffusion flame adjacent to a solid fuel slab are investigated experimentally and theoretically. Flows due to natural convection are eliminated by performing the experiment in low gravity. The range of velocities tested is 1.5 cm/s to 6.3 cm/s and the mole fraction of oxygen in the O2/N2 atmosphere ranges from 0.15 to 0.19. Although the flames did not reach the final steady state in the 5.2 seconds to which the experiment was limited, trends in many flame charasteristics, such as flame size, shape and color can be deduced. As the flow velocity is reduced, the flames move farther from the fuel surface, and its color suggest a lower flame temperature. As the oxygen concentration is lowered the flames move closer to the fuel sample and the flame temperature is lowered. With stand off distances up to 8.5 mm and thicknesses around 1 or 2 millimeters, these flames are much weaker than flames observed at normal gravity. A corresponding theoretical model is solved using a two-dimensional Navier-Stokes system with a one-step finite-rate chemical reaction and surface radiative loss. Computed flame shape and size compare favorably with experimental results, but the computed trend of maximum temperature does not appear in agreement. The implications of these comparisons are discussed.
Size and shape of solid fuel diffusion flames in very slow speed flows
Groesse und Form der Diffusionsflammen von Festtreibstoffen in Stroemungen mit sehr langsamer Geschwindigkeit
AIAA-Papers ; Jul ; 1-16
1987
16 Seiten, 12 Bilder, 5 Tabellen, 14 Quellen
Aufsatz (Konferenz)
Englisch
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