Effect of syngas composition on heat release rate response and thermoacoustic oscillations in swirl-stabilized combustors

In this study, we investigate the effect of hydrogen and carbon monoxide addition on the heat release rate response during self-excited thermoacoustic oscillations in a turbulent swirl-stabilized combustor. The combustor exhibits self-sustained limit cycle oscillations at a frequency closer to the fundamental acoustic mode for methane-air combustion above a critical Reynolds number. As the percentage of hydrogen and carbon monoxide addition is increased, we observe the emergence of quasiperiodic and period-2 oscillations along with significant increase in acoustic pressure amplitude. However, the thermoacoustic amplitude reduces with further increase in the hydrogen percentage. Dynamic mode decomposition of high-speed chemiluminescence is used to analyze the mode and the flame structure that cause the amplification of thermoacoustic oscillations for different syngas compositions. Further, the phase-averaged images corresponding to different nonlinear states are investigated. This study shows that moderate percentage of hydrogen modify the spatial distribution of heat release rate and cause the amplification of thermoacoustic oscillations.