Transition to Thermoacoustic Instability in a Turbulent Combustor

抄録

Research on the transition to thermoacoustic instability has been gaining interest in the recent years. Traditionally, such a transition to thermoacoustic instability was considered as a Hopf bifurcation, wherein the system dynamics exhibit a direct transition from stable (combustion noise) to unstable (limit cycle oscillations) operation at a critical value of the control parameter. Recent studies have reported that the transition to thermoacoustic instability is not direct, but happens through an intermediate state called intermittency. During intermittency, bursts of large amplitude periodic oscillations emerge amongst epochs of relatively low amplitude aperiodic oscillations. The use of synchronization theory to detect the coupled behaviour of the acoustic pressure and the heat release rate oscillations has shown that these signals are desynchronized during the state of combustion noise, whereas they exhibit phase synchronization at the onset of thermoacoustic instability. During the state of intermittency, signals are phase synchronized in the periodic regimes and desynchronized in the aperiodic regimes. Synchronization theory further aids in identifying another state of the coupled oscillations called generalized synchronization that happens after the onset of phase synchronization, during which both the acoustic pressure and the heat release rate signals exhibit a strong correlation in their amplitudes as well as instantaneous phases.