Dynamics of thermoacoustic instability under high-swirling flow

Thermoacoustic instability driven by the mutual coupling among the acoustic pressure, heat release rate, and flow velocity fluctuations, possesses high-amplitude pressure oscillations, leading to structural damage of the combustor. This study experimentally clarifies how the swirling flow affects the mutual coupling from a perspective of complex networks, focusing on the dynamics of thermoacoustic instability under high-swirling flow. As the swirl number exceeds a critical value, the combustion state significantly changes to thermoacoustic instability with aperiodic low-amplitude moderation. This aperiodic modulation is associated with an abrupt onset of local flame extinction under high-swirling flow condition. The onset of the local flame extinction degenerates the sustainment of thermoacoustic instability, which is reasonably identified by the vertex strength of two complex networks: turbulence network and thermoacoustic power network.