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The mass burning rate of a horizontal fuel cylinder at low Grashof numbers is analyzed using a semiempirical method. The method consists of utilizing the Schvab-Zeldovich formulation with a flame-sheet model and measured flame standoff distances. The derived burning rate expressed in terms of the thermal properties of the solid fuel and the gaseous phase, and the cylinder radius show general agreement with experiment.

Combustion of dry oak and wet oak with 50 wt% water content at a fire level surface heat flux of 2 cal/cm2 sec was experimentally investigated. Experimental measurements included thermal-physical properties, mass loss rate, surface regression rate, solid density, temperature, pressure, and gas composition. Effects of absorbed water on wood pyrolysis and combustion are examined from these measurements. It is found that the absorbed water mainly delays the temperature rise in the wet wood and the vaporized water convectively cools the pyrolyzing wood. The pyrolysis process is thus delayed in the wet wood and the volatile combustible gases are diluted by the water vapor. Decomposition of water and reaction between water and wood char (carbon) do not appear to occur significantly. At steady-state burning, surface regression rates are the same for both dry and wet wood, apparently because the regression rate is primarily governed by the oxygen supply to the char surface.

Luminous radiation from the soot particles of a flame propagating vertically downward on a polymethyl methacrylate (PMMA) rod is investigated by using exact and approximate analyses. Investigation shows that for vertically downward burning of a 0.5 in. diam PMMA rod, the luminous radiative heat transfer from the flame to the fuel rod is well within the optically thin limit. The approximate analysis is extended to conventional hydrocarbon fuels. A simple optically thin approximation in terms of flame temperature T f and mean beam length L m is obtained for the luminous radiation from soot particles. The thin approximation gives errors of less than 5% from exact values for L m T f