Measurements of transient sequences for fully premixed hydrogen/air swirling flames.

Decarbonization based on hydrogen represents a pivotal strategy in the transition to cleaner energy and transport systems. Towards this goal, transient sequences of lean blowout, blowoff, and flashback are studied with high-speed direct flame imaging. These transient sequences are documented from an identical starting point: a 100% H₂/Air swirl-stabilized condition also described. The sequences are depicted on a regime map function of equivalence ratio and bulk velocity, considering the evolution of both the Karlovitz number and the Lewis number. Sequences are acquired on a fully premixed, hydrogen/air, swirl-stabilized laboratory scale experiment. Data acquisitions are made with a high-speed camera (sensitive to both UV and visible light wavelengths) to capture flame chemiluminescence, complemented by schlieren imaging to visualize and describe flame evolution during each transient sequence. The presentation also provides insights on the effects of preferential diffusion versus turbulence on flame wrinkling for jet flame. Finally, the variations in flame intensity amplitude by integrating flame images into a time-series signal across different cases are discussed. This study aims at investigating unsteady processes for hydrogen premixed flames.