Thermoacoustic Instabilities in Hydrogen-Methane Combustion: Analysis of Self-Excited Flame Dynamics in a Lab-Scale Cyclone Burner

Abstract The transition to hydrogen as a fuel is crucial for reducing carbon emissions in industrial combustion processes, but it presents challenges in maintaining combustion stability. This study examines the flame dynamics and thermoacoustic instabilities in a 30 kW cyclone burner system, using methanehydrogen blends with hydrogen volume fractions ranging from pure methane to 80% hydrogen. The cyclone burner imparts a swirling motion to the airflow, which is then premixed with fuel in the annular passage. Pressure oscillations were recorded using four pressure transducers, while OH chemiluminescence was measured through optical access windows using a photomultiplier. Flame dynamics were captured by a Phantom VEO 710L highspeed camera, allowing detailed investigation of the flame’s behavior under varying fuel compositions. The addition of hydrogen was found to amplify oscillation amplitudes, significantly influencing the combustion stability. Non-intensified high-speed camera images were processed using spectral proper orthogonal decomposition (SPOD), offering deep insights into the flame’s physical characteristics. The SPOD spectra revealed dominant frequencies that strongly correlated with pressure and heat release rate measurements. Similar trends were observed in SPOD modes as hydrogen concentrations increased, further highlighting the role of hydrogen in increasing pressure oscillation amplitudes.These findings demonstrate that SPOD-processed visual data is an effective tool for analyzing flame dynamics and diagnosing thermoacoustic instabilities in hydrogen-methane combustion systems. The research contributes to the understanding needed to safely integrate hydrogen into industrial combustion processes while maintaining system stability.