Suppression of fuel and air stream diluted methane–air partially premixed flames in normal and microgravity

Effect of fuel type on the extinction of fuel and air stream diluted partially premixed flames

“…Figure 4 presents liftoff heights plotted with respect to the CO 2 volume fraction for FSD ethylene and acetylene flames established at different fuel-side equivalence ratios / (for NFs / = 1). The corresponding results for methane flames have been previously reported [1,3,42].…”

“…Based on our previous analysis [3,42], for / < / tr , the fuel is the deficient reactant while for / tr < / < 1, the oxidizer is deficient (cf. Fig.…”

“…Our previous investigations of the extinction of CO 2 -diluted methane-air partially premixed flames (PPFs) [1][2][3] have shown that the relative effectiveness of fuel and air stream dilution (FSD and ASD, respectively) varies significantly with the fuel stream equivalence ratio. This is significant since fire suppressants are typically introduced into the air surrounding a flame, which may not always be the most effective action for flame suppression.…”

“…However a ban on their production since 1994 [7], has led to the introduction of a variety of alternative suppressants [8][9][10], including such inert alternatives as water mist [11] and inert gases [12][13][14]. The effectiveness of CO 2 as a flame suppressant has been examined in different configurations [1][2][3]15,16] but there is no comparison available of its relative effectiveness as it is introduced into the primary fuel and primary air streams of PPFs.…”

“…This is supported by other investigations [17][18][19] that showed that the relative effectiveness of fuel and air stream dilutions can change significantly for a NF as the fuel changes. Thus, a general observation from these investigations is that the dilution of either the fuel or air stream may be typically the more effective means of flame suppression for a certain condition [3,5] for both inert and chemically active agents.…”