Impact of CO2, N2 or Ar diluted in air on the length and lifting behavior of a laminar diffusion flame

Radiative emissions measurements from a buoyant, turbulent line flame under oxidizer-dilution quenching conditions

“…Initial extinction results for the present study, in agreement with those of previous works [25][26][27][31][32][33][34][35], show that weakened flames in co-flow lift prior to extinction. As currently understood, this type of extinction is mainly due to weakening of the edge reaction kernel responsible for flame stabilization [25][26][27], a phenomenon more characteristic of partially-premixed flame suppression, than that of the diffusion flames encountered in fire safety applications.…”

“…7a. As shown, L f increases with reducing X O2 , in agreement with previous observations [6,25]. This trend is rationalized that, as X O2 decreases, a greater volume of oxidizer must be entrained to support complete combustion (and soot oxidation).…”

“…The inverse effect, occurring due to soot extinction, explains the slight over-predictions in L f for methane fuel below X O2 ¼0.180 and propane fuel below X O2 ¼0.160. Similarly declining visible flame height measurements coinciding with flame color transition have been previously reported [25].…”

“…As currently understood, this type of extinction is mainly due to weakening of the edge reaction kernel responsible for flame stabilization [25][26][27], a phenomenon more characteristic of partially-premixed flame suppression, than that of the diffusion flames encountered in fire safety applications. It is then questionable whether/how liftoff extinction relates to the suppression of large-scale turbulent flames, where suppression is believed to result from progressive localized extinction throughout the main combustion region [20][21][22][23][24][25][26].…”

“…Others have focused on developing scaling relationships to compare results from different sized configurations [18,19]. It is worth noting that most previous studies have featured small laminar flames, which have proven quite useful for exploring extinction theory [20][21][22][23][24][25][26][27] as well as establishing extinction-limit criteria for flames under quenching action [28][29][30][31][32][33][34][35].…”