Limited driving characteristics of combustion instability in a swirling flame: An experimental study

Abstract

Regarding combustion instability, heat-release pulsation leads to pressure pulsation. Conversely, the driving force of the pulsating flame restricts the oscillation equilibrium point of combustion instability. Thus, in this paper, we developed a flame limited driving model explaining the finiteness of the driving energy of flame pulsation. Our research indicates that the limit cycle state of combustion instability was affected by the limitations of heat-release pulsation and Rayleigh integration. The coupling intensity of the heat-release pulsation and oscillating pressure decreases gradually with the increase in the oscillating pressure amplitude. In addition, an increase in flame pulsation amplitude presents finiteness similarly. When the acoustic amplitude exceeds a certain threshold, the amplitude of heat-release pulsation stops increasing until the flame approaches the oscillation blow-out limit. The further strengthening of the oscillation intensity of combustion instability is simultaneously restricted by the limitations of heat-release pulsation and Rayleigh integration, and thus the combustion instability finally stabilizes at the oscillation equilibrium point.