Investigation of subcritical instability in ducted premixed flames

An experimental investigation of the bistable region of instability in a thermoacoustic system comprising of ducted, premixed laminar flames has been performed. The stability diagram of the system is obtained and the bistable region for a range of flame locations at different fuel-air mixture equivalence ratios is identified. Subsequently, threshold amplitudes for triggering instability in the system using sinusoidal acoustic forcing, introduced externally, is obtained. It is observed that depending on how close the system is to the Hopf point and the nature of oscillations at the Hopf point, the triggered oscillations can exhibit different dynamical behavior. Copyright © 2011 by ASME.