Experiments on dynamical motion of buoyancy-induced flame instability under different oxygen concentration in ambient gas

Abstract

We experimentally investigated the dynamical motion of buoyancy-induced flame instability under different oxygen concentrations in ambient gas for a non-premixed flame, focusing on how the oscillation frequency and amplitude of the flame tip change with oxygen concentration in ambient gas. The oscillation frequency of flame tip f t increases monotonically with increasing oxygen concentration in ambient gas X o, while the oscillation amplitude at flame tip A m drastically decreases with increasing X o. The change in the oscillation frequency for different oxygen concentrations can be clearly explained by the use of the theoretical equation proposed by Cetegen and Ahmed [B.M. Cetegen, T.A. Ahmed, Experiments on the periodic instability of buoyant plumes and pool fires, Combustion and Flame 93 (1993) 157–184]. As the flame tip location decreases with increasing X o, the magnitude of the periodic fluctuation of the interface between hot combustion products and ambient gas becomes small at the flame tip. This leads to a remarkable decrease in the oscillation amplitude of the flame tip in a high oxygen concentration environment.