Combustion and Flame, Vol.158, No.10, 1960-1969, 2011
Self-excitation in laminar lifted free-jet propane flames diluted with nitrogen
Laminar lifted propane free-jet flames diluted with nitrogen were experimentally investigated to determine distinctive self-excitation regimes in the flame stability map and to elucidate the individual flame characteristics. Extremely low-frequency (<0.1 Hz) self-excitation was caused by conductive heat loss from the premixed wings to the trailing diffusion flame and could be explained by a proposed mechanism for edge flame extinction during triple-flame propagation as well as flame-front propagation. A newly observed heat-loss-induced flame blow-out mechanism was related to conductive heat loss from the premixed wings to the trailing diffusion flame. Additional self-excitation prior to flame blow-out was caused by buoyancy and also significantly affected by the conductive heat loss from the premixed wings to the trailing diffusion flame. This was explained in terms of triple-flame propagation and flame-front propagation. Self-excitation obtained in laminar lifted propane free-jet flames diluted with nitrogen was characterized by functional dependencies of the Strouhal number with related parameters. (C) 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Keywords:Buoyancy-induced self-excitation;Flame-front propagation;Flame stability map;Fuel concentration gradient;Heat-loss-induced self-excitation;Triple-Flame propagation