10.1063/5.0068660.1

Abstract

The paper studies experimentally the stability of an inverted conical plane-symmetrical premixed methane-air flame under normal and reversed gravity. The conical flame is stabilized by a thin transverse rod. Flow velocity is varied within the range of 1–8 m/s, fuel equivalence ratio— within the range of 0.8–1.4. It is shown that such a flame could be both V-shaped (attached only to the stabilization rod) and M-shaped (attached both to nozzle edge and stabilization rod) depending on the set of conditions. The transition between two modes is studied experimentally under normal and reversed gravity. The hysteresis properties for the M–V and V–M transitions under the normal gravity conditions and their absence under the reverse gravity ones are reported. The most unstable flames are observed under reversed gravity at the maximum burning velocity (φ ≈ 1.1 ±). For such conditions, periodical oscillations between M-shaped and V-shaped flames occur over a wide range of velocities. In the experiments under reverse gravity, the V shape prevails over the M shape. It is found that a reverse flow exists above the stabilizer at any velocity under normal gravity and at high velocities (>5 m/s) under reverse gravity. In both cases, a linear increase in the longitudinal size of the vortex zone with increasing velocity is observed. It is concluded that gravity noticeably contributes to rich flames stability.