Radiation-affected laminar flame propagation

Abstract

Increased laminar flame thickness and flame speed under the influence of radiation is shown in terms of an original heat transfer number H = ~rP Total radiation 1 + 3r2/(1 -to) Conduction where ~ = (Kp/rR ) '~ is the weighted nongreyness, K p and r R are the Planck mean and the Rosseland mean of the absorption coefficient, r = rM6 K is optical thickness, r M = (rprR)'/~ the mean absorption, 8 K the conduction flame thickness, P = 4o TM3/(~5 K) the Planck number, T M the adiabatic flame temperature, ~ the thermal conductivity, and w the albedo, the ratio of scattering to extinction.

Buoyancy-driven turbulent diffusion flames

“…As is well known, the primary effect of thermal radiation on high-temperature problems is on the heat flux. Studies by Arpaci and coworkers [58,59,61,62,[64][65][66], and Selamet and Arpaci [63,67] show the emission, absorption, and scattering (hotness, optical thickness, and refractive) effects on this flux. However, there is no experimental literature on pool fires separating these effects.…”

“…On intuitive grounds, the emission effect of radiation (hotness of flame) has been already incorporated into the heat of combusion and the latent heat of evaporation by fractional lowering (say 3' and ~b) of these properties (see Kanury [19]). Following the studies of Arpaci and coworkers [58][59][60][61][62] and Selamet and Arpaci [63], the optical thickness and scattering effects of radiation can be incorporated into 3' and ~b. However, because of the lack of experimental data, no attempt is made here to demonstrate their influence on 3' and ~b.…”

Entropy production in flames

“…which, in terms of Eqs. (15), (16), and (18) (21) where sij is the rate of deformation. For a reversible process, all forms of dissipation vanish, and…”

“…Rearrange Eq. 25 [14], and McIntosh and Clarke [15] for the case excluding radiation, and Arpaci and Tabaczynski [16,17] for the case including radiation; also, see Kooker [18] and Sohrab and Law [19] for the importance of radiation on quenching processes, and Lee and Tien [20] for the effect of condensed fuels on this process). References [12,13,16,17] follow the usual practice and evaluate the minimum quench distance from the tangency condition,…”

Radiation-affected laminar flame quenching

“…By assuming that the walls are black (ew = 1) and noting that r/ -1, o) -0, and Tb ~ Tu, the right-hand side of Eq. (16) may be rearranged as 1 7"…”