Visualization of Flashback in a Hydrogen Fueled Axial Stage Combustor

This study presents a detailed experimental investigation into the influence of hydrogen enrichment on flashback phenomena within a high-pressure, axially staged combustion system. The facility features a custom-designed glass injector which enables direct optical access to the axial stage and facilitates high-fidelity visualization of flame behavior during flashback events. The main stage provides a consistent high-temperature crossflow across all tested conditions, while the axial stage is varied in hydrogen content but maintained at a flame temperature of 1916K and momentum flux ratio of 2.5 for each case. The variation in the axial stage fuel composition spanned from 70% to 100% hydrogen by molar fraction to assess flashback propensity. The glass injector reveals that, even with increasing hydrogen content, flame propagation preferentially initiates on the windward side of the axial jet, resulting in flashback into the injector. The ability to have optical access into the secondary axial jet injector provides new insights into flame anchoring mechanisms and flashback tendencies in hydrogen-enriched, lean axial stage flames.