1971 Volume 21 Issue 2 Pages 55-62
Analysis on the surface flame-spread velocity of plywood in the inclined tunnel-furnace has been pursued with respect to various inclination-angle and flow-rate of the fuel-gas. Following theoretical equation has been derived as a particular solution for the stationary state surface combusion ;
Vf=ρCpVfa/3LρωCpωτ +L(h+havR)/2ρωCpωτ(2－χ)+aρCpβg0 sinθ(1－χ)(TF－TL)/3ρωCpωτVF(2－χ)
where Vf and VF are the mean flame-spread velocity and hot current velocity respectively, L and a are flame-lenghth and thickness (δ) over L as the parameter concerning the-shape of flame, h and hR are heat-transfer coefficient by current and radiation respectively, TF and TL are the temperature of flame and surface temperature of sample at the top of flame, χ and τ are the heat-loss coefficient and thickness of sample, ρω and Cpω are the density and specific heat of the sample, ρ and β are the density and volume-expansion coefficient of air. The first term on the rightside of the above equation concerns with the drafting effect of the hot current velocity (VF), the second term represent the radiation-effect by the flame-lenghth, and the third term expresses the contribution from buoancy-effect of the current. The initial driving force to propagate fire from small fire-source from wall to ceiling is considered to be due to the third and second effect and the succesive increase of the fire-source on the floor will accelerate the drafting-effect of the hot-current exponentially as are represented in the first term of the equation and then reaches to the so-called flash-over.
