Investigation of Critical Operating Conditions for Hydrogen Flames Under Typical Gas Turbine Conditions

Abstract The reliable operation of the core component of a modern jet-stabilized burner for large high-efficiency gas turbines with high power density and wide operating range was demonstrated in pressurized operation with 100% hydrogen. High-pressure tests were performed at the high pressure combustor test rig HBK-S at the DLR Institute of Combustion Technology, mainly with hydrogen, but also with various hydrogen/natural gas mixtures. A single nozzle burner configuration, representative of modern jet-stabilized gas turbine combustion systems, was used for this purpose in a special optically accessible combustion chamber. Optical and laser-based combustion diagnostics was applied for flame characterization. The investigation addressed the high reactivity of hydrogen and focused on operation at high pressures, high preheating temperatures and highflame temperatures, even beyond the specifications of state-of-the-art gas turbines, up to the operational limits regarding flashback. The influence of the operational parameters was investigated in detail on a generic configuration using a cylindrical quartz glass tube as mixing duct. Flame flashbacks could be directly observed within this optical mixing tube by highspeed OH* chemiluminescence. Further tests were carried out with a newly developed metallic mixing duct, that was equipped with a special device to enhance the flashback resistance based on purge air. The results showed, for example, a strong dependence on the pressure. No flashbacks were observed in the investigated flame temperature range at low pressures (4–6 bar). Towards higher combustion chamber pressures, the operational limit in terms of flashback shows an asymptotic behavior. Higher jet velocities push the flashback resistance to higher adiabatic flame temperatures. The flashback prevention arrangement of the metallic mixing duct successfully extends the operational range at all conditions compared to the optical mixing duct.