UPWARD FLAME SPREAD OVER THIN SOLIDS IN PARTIAL GRAVITY
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Authors
Feier, Ioan
Shih, Hsin-Yi
Sacksteder, Kurt R.
T'ien, James S.
Issue Date
2002-01
Type
Article
Language
en_US
Keywords
Alternative Title
Abstract
Experiments to observe upward and downward flame spread and extinction over a thin solid fuel inpartial-gravity environments were conducted in an aircraft flying parabolic trajectories. In the upwardspreading case, flames with constant lengths and steady spread rates were observed using narrow fuelsamples in reduced pressures. The upward flame spread rates and the flame and pyrolysis lengthsincreasedlinearly with the gravity level. The proportionality constants, however, increased with pressure and samplewidth. For comparison, downward spreading tests were also conducted using the same reduced-pressureatmospheres needed to obtain steady flames in the upward spreading case. In downward spreading, thesteady spread rates and the flammability boundary exhibited a non-monotonic dependence on gravity. Thisbehavior is attributed to competition between finite-gas-phase residence times in the flame stabilizationzone and radiative heat losses from the flame. Throughout the accessible range of partialgravity,the upwardspreading flames propagated at higher speeds than the downward spreading flames and the fuel is moreflammable in the upward spread direction. A three-dimensional concurrent-flow flame-spreading model,originally developed for forced flows in a duct at microgravity, was reformulated and numerically solvedfor buoyant flow. The numerical flame spread simulation provides detailed flame structure including gasflow and temperature fields, oxygen and fuel transport, and solid temperature and thickness distributionsand predicts the essential three-dimensional features observed for the narrow, reduced pressure flames
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Citation
Feier, Ioan & Shih, Hsin-Yi & Sacksteder, Kurt & Tien, James. (2002). UPWARD FLAME SPREAD OVER THIN SOLIDS IN PARTIAL GRAVITY.