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Flame Spread On Charring Materials: Numerical Predictions And Critical Conditions

Delichatsios, M.A. and Chen, Y., 1994. Flame Spread On Charring Materials: Numerical Predictions And Critical Conditions. Fire Safety Science 4: 457-468. doi:10.3801/IAFSS.FSS.4-457


A detailed flame spread computer code has been applied to predicting flame spread and fm growth for the upward wall orientation on charring materials. The flammability properties for the pyrolysis rate of charring materials have been measured by performing pyrolysis experiments and surface temperature measurements in inert atmospheres. An extensively validated integral pyrolysis model for charring materials was employed in a flame spread code: the present flame spread code is an improvement and modification of a code presented in a previous paper. The improvements include: a) calculation of the burnout front, b) incorporation of convective heat loss from the front and back surface and c) profiles for the heat flux distribution from the flame to the wall. The flame spread code can also routinely handle preheating of the wall by externally imposed heat fluxes prior to ignition. Predictions from the model are compared with various experiments for upward flame spread performed at MST and in Japan; the agreement is good. In addition, the model and the experiments verify that flame spread stops when the flame height is nearly equal to the length of pyrolysis region. This maximum flame spread length is simply related to the properties of the charring material as Lm~(q”n xA ?Hc/ (?Hv)eff)2 where q”n, is the net heat flux from the flames (equal to flame heat flux minus reradiation losses at the pyrolysis temperature), xA?Hc, is the actual heat of combustion and (AHV), is the heat of gasification of the material corrected for char conductivity effects.


numerical predictions, charring material, flame spread

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