Asymptotic analysis of radiative extinction in counterflow diffusion flames of nonunity Lewis numbers

Extinction of premixed methane/air flames in microgravity by diluents: Effects of radiation and Lewis number

“…The combined effects of stretch and radiation on premixed flames have been studied by several researchers [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Farmer and Ronney [17] numerically examined the dynamics properties of near-limit CH 4 /air flames in planar and spherical geometries considering radiative heat loss from CO 2 and H 2 O.…”

“…Wang and Niioka [31] numerically investigated radiation reabsorption effects in CH 4 -air counterflow premixed flames and found that the reabsorption of emitting radiation leads to substantially wider flame thickness and higher flame temperature than those calculated by using the optically-thin model. Ju and his co-workers [23][24][25][26][27][28][29][30]34,35] conducted extensive studies on the combined effects of radiation and stretch on flammability limits for various Lewis number mixtures. In particular, their recent work [34] show that the flame geometry has a significant impact on radiation absorption and that the 1-D planar radiation model was not valid for the computation of the flame speed of a spherical flame.…”

Perfectly stirred reactor model to evaluate extinction of diffusion flame

“…More recent experimental [14][15][16] as well as computational and theoretical [3,4,[17][18][19][20] works on diluent-induced flame extinction demonstrate that, similar to the critical extinguishing concentration in premixed flames, a fundamental concentration limit also exists in diffusion flames; when the diluent concentration exceeds such a limit, steady diffusion flame fails to exist at any strain rate. The fundamental limit arises as a merging point of two extinction limits governed by essentially different mechanisms, high strain blow-off and radiative quenching.…”

Local Extinction of Diffusion Flames in Fires

“…Thus, we find that the Damköhler number is a function of flame stretch and flame temperature, Da ~ (1/χ st )/exp(T a /T st ). Critically low values of Da may therefore be achieved in several ways [4][5][6][7][8][9][10][11][12][13]: low values of Da may be achieved under fast mixing conditions (i.e., when χ st is large and τ mixing is short); low values of Da may also be achieved under low temperature conditions (i.e., when T st is low and τ chemical is long). The fast mixing limit is the extinction limit associated with aerodynamic quenching; the low temperature limit is the extinction limit associated with thermal quenching and dilution quenching.…”