Two-dimensional interactions of non-isothermal counter-flowing streams in an adiabatic channel with aiding and opposing buoyancy

Flame ignition in the counterflow configuration: Reassessing the experimental assumptions

“…16 that there is considerable amount of H 2 both in upper and lower recirculation zones for both solutions branches. This is mainly due to the large sizes of these recirculation bubbles, which cause considerable amount of mixing [37,[56][57][58]. velocities.…”

“…It was realized also that the reported bifurcation is sensitive to T air and K. At low K and high T air , only the upper branch was attainable, while the lower branch was realized only for high K and low T air values, which could be caused by buoyancy [37]. Thus, given the wide range of T air and K values that are encountered in counterflow flame ignition experiments, it is not clear what flow conditions will be prevailing at the pre-ignition states, and thus velocity measurements or shadowgraph visualization are required.…”

“…Bifurcation of non-isothermal counterflowing jets has been reported also. Conditions that result in steady [35] and unsteady behavior of the flow-field have been identified [24,36,37]. Those conditions were shown to depend on the velocity and temperature at the nozzle exit as well as L.…”

“…In this regime, only stable and bi-stable states have been reported in axisymmetric configuration when the top jet has lower density, i.e. stable stratification [8,9,[23][24][25][31][32][33][34][35][36][37].…”

“…Finally, it should be noted that in the presence of a flame, the heat release is intense resulting in high temperatures and thus notable buoyancy-driven convection at large radii, which has been shown to suppress the tendency of the flow-field to bifurcate [37]. This could be the reason that in the combustion literature, the stability of counterflowing jets has attracted less attention despite its wide use.…”