Longitudinal and azimuthal thermoacoustic modes in a pressurized annular combustor with bluff-body-stabilized methane-hydrogen flames

To explore the dynamics of annular combustors, we investigate azimuthal thermoacoustic instabilities under a range of hydrogen power fractions and operating conditions. Using time-series analysis and mode detection techniques, we examine the relationship between longitudinal and azimuthal modes, identifying a transition from chaos to high-amplitude periodic states. Our research sheds light on how hydrogen enrichment affects combustor stability and presents the first identification of type-II Pomeau--Manneville intermittency in annular combustors. These findings contribute to knowledge of the modal dynamics within combustors, with implications for the design and operation of future systems.