Influence of fuel reduction rate on flame dynamics and lean blowout characteristics in a centrally-staged combustor

Understanding the transient dynamics of a lean blowout (LBO) is critical for aero-engine safety and operability. Yet, the mechanisms governing flame extinction under rapid fuel reduction during engine deceleration remain insufficiently explored. This study employs high-speed imaging and advanced analytical methods, including dynamic mode decomposition (DMD), to systematically investigate flame extinction dynamics in a model combustor. Results reveal a distinct three-stage extinction process: stable combustion, a volatile extinction transition, and final blowout. The critical transition stage is characterized by severe flame front fragmentation, localized quenching, and reignition events, driven by fuel supply disturbances and fuel-air ratio reduction. Analysis shows that increasing the fuel reduction rate significantly amplifies flame instability, reducing the extinction transition duration by approximately 55% while increasing the LBO limit by 12.6%. By integrating CH* chemiluminescence with DMD, the dynamic evolution of flame extinction and the inherent correlation between its instability and dominant mode are revealed. These findings enhance our understanding of flame extinction mechanisms and offer valuable insights for improving combustion stability and developing active control strategies.