Extinction of premixed flames by stretch and radiative loss

Combined effects of curvature, radiation, and stretch on the extinction of premixed tubular flames

“…(14) and (15) reduce to the previous results of adiabatic tubular flames [20] in the limit of N ¼ 1, R I ¼ 0, and L AE ¼ 0; and those of counterflow flames [3,10] in the limit of N ¼ 0, R I ¼ 0, and R O ! 1.…”

“…For both flame geometries, the potential flow assumption, which is commonly used in the large activation energy asymptotic analysis [3,10,20], is employed here. By introducing a geometry factor N with N ¼ 0 for the counterflow flame and N ¼ 1 for the tubular flame (with e R I and e R O being the inner and outer tube radius, respectively), the potential flow field for both configurations can be written as…”

“…In the limit of large activation energy, chemical reaction occurs only within a very thin zone of high temperature, whose thickness is much smaller than that of radiation zone [3,8]. Therefore, the reaction rate can be replaced by the Dirac-Delta function [26][27][28] x ¼ exp…”

“…However, for stretched flames, the flammability limit can be changed through the combined effects of thermal radiation and flame stretch. The combined effects of flame radiation and stretch have been studied by using planar and radiative counterflow flames [3][4][5][6][7][8][9][10][11][12]. These studies have shown that the flammability limit of stretched flames below a critical Lewis number can be lower than that of unstretched flames.…”

Numerical Investigation of CH4/CO2/Air and CH4/CO2/O2Counterflow Premixed Flames with Radiation Reabsorption

“…It is therefore of importance to examine the effects of radiative heat loss on stretched flames. Sohrab and Law (1984) investigated the effect of radiative heat loss on stretched premixed flames, and concluded that radiation has little impact on the extinction of stretched flames because the stretch rate in their study was not extended to a sufficiently low value. Egolfopoulos (1994) also studied the radiation effect on steady and unsteady stretched flames, and indicated that radiation is important for near limit stretched laminar flames and for weakly stretched diffusion flames.…”