Keywords

hydrogen combustion; flashback; axial-stage combustor; gas turbine; flame stability; hydrogen enrichment

Abstract

The addition of hydrogen to conventional fuels enhances reactivity and can increase the risk of flashback in premixed gas turbine combustors. This study investigates the effects of premixing length and hydrogen concentration on flame stability in a high-pressure axial-stage combustor. Experiments were conducted at the UCF Propulsion and Energy Research Laboratory using a two-stage configuration, where the primary stage provided a high-temperature vitiated crossflow using a hydrogen-piloted, premixed methane–air mixture, and hydrogen-enriched methane–air mixtures were injected through a concentric fuel-tube injector in the axial stage. Premixing length was varied for pure hydrogen flames, and hydrogen concentration was varied at a fixed premixing length, while all other operating conditions were kept constant. Increasing premixing length resulted in more complete mixing prior to injection, raising the effective flame speed at the injector exit. Intermittent upstream flame propagation was first observed at the 10.16 cm premixing length, with flashback becoming more frequent and sustained at longer lengths. Increasing hydrogen concentration at a fixed premixing length produced a similar effect, transitioning flame behavior from stable leeward attachment to intermittent windward attachment and eventually to frequent flashback events above 90% H₂. The majority of upstream propagation events initiated on the windward side of the injector, where boundary layer effects reduce local axial velocity. These results demonstrate that injector geometry and local flow structure strongly influence flashback behavior in hydrogen-enriched gas turbine combustors operating at elevated pressures.

Thesis Completion Year

2026

Thesis Completion Semester

Spring

Thesis Chair

Ahmed, Kareem

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Thesis Discipline

Aerospace Engineering

Language

English

Access Status

Open Access

Length of Campus Access

None

Campus Location

Orlando (Main) Campus

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