Flame Propagation Through Layered Fuel-Air Mixtures

Flame Phenomena in Premixed Combustible Gases

“…For the idealized infi nite depth of the air layer the results revealed that the ratio of the propagating fl ame speed to that of the laminar fl ame speed was equal to the square root of the density ratio ( ρ u/ ρ b ); that is, the fl ame propagation for the layered confi guration is about 2.6-2.8 times the laminar fl ame speed. Indeed the observed experimental trends [41,42] fi t the analytical derivations. The same trends appear to hold for the case of a completely premixed combustible condition of the roof of a channel separated from the air layer below [41] .…”

“…To show this effect Feng et al . [41,42] considered analytically the propagation of a fuel layer at the roof of a channel over various lengths and depths of the confi guration in which the bottom layer was simply air. For the idealized infi nite depth of the air layer the results revealed that the ratio of the propagating fl ame speed to that of the laminar fl ame speed was equal to the square root of the density ratio ( ρ u/ ρ b ); that is, the fl ame propagation for the layered confi guration is about 2.6-2.8 times the laminar fl ame speed.…”

“…This displacement results in redistributing the combustible gaseous layer over a much larger area in the induced curved, parabolic type, fl ame front created. Thus the expansion of the combustible mixture sustains a pressure difference across the fl ame and the resulting larger combustible gas area exposed to the fl ame front increases the burning rate necessary for the elevated fl ame propagation rate [40,42] .…”

Flame Stabilization in a Layered Medium

“…Investigations by Phillips (1965) ;Liebman, Corry and Perlee (1970); Hirano et al (1977); Feng, Lam and Glassman (1975); Hirano and Suzuki (1980) and others have therefore tended to focus on flame speed and gas movement. Consequently, in the latter two studies, models were developed which incorporated detailed hydrodynamics but neglected diffusional effects.…”

On Convective Flame Acceleration in Long Horizontal Galleries

“…The propagation of flames in horizontal layers has been investigated by Burgoyne and Roberts (1968), Phillips (1965Phillips ( , 1975, Perlee et al, (1964), Liebman et al (1968), Feng et al (1975), Kaptein and Hermance (1976), as well as the burning and buoyancy of a combustible gas sphere in surrounding air (Fay and Lewis, 1976) and the spread of flame beneath the ceiling with increasing velocity of the flame leading edge (Lovachev, 1976). For this concentric spread of flame beneath a 4 m 2 ceiling (in a cubic chamber 8 m 3 ) the flame velocity remains constant, though the kernel development beneath the ceiling is essentially unsteady (Figure I in Lovachev, 1976).…”