STAND-OFF DISTANCES ON A FLAT FLAME BURNER

For a given stand-off distance of a laminar flame on a porous metal burner, it has been shown both experimentally and theoretically that there exists two solutions, a low-speed flame and a high-speed flame. For small enough stand-off distance there is no solution. The minimum stand-off distance is identified as the quasi-steady approximation to the extinction length for flames quenching in flows perpendicular to a heat sink. Measurements of flame speed, maximum flame temperature, and stand-off distance have been correlated for hydrogen, ethylene, and methane flames by a Peclet number dependent only on the ratio of the heat of combustion to the heat loss. The correlation agrees quantitatively with solution of one-dimensional flame equations where a Dirac-delta function models the reaction rate. © 1979.