<b>Influence of Surface Roughness and Fuel Delivery Strategy on Hydrogen Combustion Stability in Turbulent Jet Burners</b>

<p dir="ltr">The influence of internal surface roughness on the performance and operability of hydrogen jet burners was investigated under both fully and partially premixed conditions. A modular burner architecture, representative of practical combustion systems, was employed. Enabling systematic variation of surface finish and fuel-air delivery strategy to isolate roughness effects from other geometric or flow influences. High-speed OH* chemiluminescence imaging was used to characterize flame structure, anchoring behavior, and flashback dynamics across a range of operating conditions. The study demonstrates that surface roughness strongly affects flame anchoring and stability, with the nature of these effects dependent on the degree of premixing. In fully premixed operation, roughness promotes enhanced stability through modified near-wall flow and turbulence, while in partially premixed configurations it alters fuel distribution and flame location. The findings highlight the coupled influence of roughness, mixing quality, and momentum interaction, underscoring the importance of surface finish considerations in the design of hydrogen-fueled combustion systems.</p>