Research on flame structure and oscillatory combustion Characteristics of hydrogen-enriched premixed Combustor

Hydrogen fuel has emerged as a critical research focus for gas turbines due to its zero-carbon and renewable advantages. However, the rapid chemical reaction rate and high combustion velocity of hydrogen can easily induce thermoacoustic oscillations. To investigate the acoustic characteristics of hydrogen-blended natural gas premixed combustors, experimental measurements and numerical simulations were conducted on dynamic pressure within the combustor under varying hydrogen blending ratios and turbulent fluctuation velocities. The results show that the dominant frequency of dynamic pressure oscillations remained within the range of 70–76 Hz as the hydrogen blending ratio increased from 0% to 30% in experimental tests,when the hydrogen blending ratio reached 40%, the dominant frequency abruptly jumped from 75.36 Hz to 197 Hz, indicating a mode transition phenomenon. Higher turbulent fluctuation velocities led to a gradual increase in dynamic pressure oscillation frequencies. The flame structure undergoes significant alterations as the hydrogen blending ratio increases, CH radicals concentrated in block-like regions downstream at 0% hydrogen blending, as hydrogen blending increased, CH radicals exhibited a distinctive "V-shaped" distribution. Numerical results show that higher hydrogen blending ratios generally amplified high-frequency dynamic pressure fluctuations. OH radicals displayed an outward diffusion trend as hydrogen content increased.