Abstract For flame spreading over solid fuels at microgravity in a quiescent environment, experimental, and computational, results show that the spread rate following ignition is steady because the leading edge of the flame itself establishes the flow field into which it spreads. Spreading into an opposing forced flow is inherently unsteady because of the changing character of the boundary-layer flow with location. The development of an unsteady flame spread model is presented and applied to thermally thick polymethylmethacrylate. The unsteady model is constructed such that interfacial phenomena, e.g., fuel surface reradiation, are accounted for as volumetric source terms in differential, conservation equations, so that the solid and gas fields may be treated simultaneously without iteration between phases. Care must be taken such that communication between the solid and gas at the interface is computed accurately. For forced flows with velocity much larger than the spread rate, radiative processes are unimportant, but for the lower flow rates, comparable to the spread rate, the opposite is true. Solutions for a quiescent environment are difficult to obtain. Conduction scales become large, and conduction heat transfer from the flame to the solid is reduced. Because of this, quiescent environment solutions could not be obtained without at least an approximate treatment of gas-phase, flame radiation.
Unsteady flame spread over solid fuels in microgravity
Advances in Space Research ; 13 , 7 ; 171-184
1993-01-01
14 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
Unsteady Flame Spread Over Solid Fuels in Microgravity
Online Contents | 1993
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