Stability, near flashback combustion dynamics, and NOx emissions of H₂/N₂/air flames in a micromixer-based model gas turbine combustor

This study experimentally investigates stability, near flashback dynamics, and NOx emissions arising from H₂/N₂ flames in a micromixer-based burner for gas turbine combustion applications. Generalized stability maps were generated and NOx emissions and temperature profiles were recorded. Two distinct flashback modes are revealed at each hydrogen fraction (HF), with intense audible loud noise (dynamic instabilities) during flashback mode 1, followed by the actual flashback (flashback mode 2) occurrence. Shorter combustors are needed for more stable H₂ flames. The onset of acoustic perturbations (flashback mode 1) is observed to occur consistently at a constant adiabatic flame temperature (AFT) of ∼1800 K. A uniform temperature profile, a smaller profile factor (PF), is reported at the different HFs. The lean cold combustion conditions minimized NOx emissions to the single-digit ppm level despite rising the AFT.