Rocha, Nuno Miguel Pina Bastos; (2025) Experimental Investigation of a Piloted Premixed Jet Burner for High-Hydrogen Flames. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Hydrogen combustion in gas turbines offers a pathway to store excess renewable energy and provide dispatchable power, but limited availability and high costs will require turbines to operate on hydrogen–methane mixtures. Hydrogen’s high reactivity presents significant challenges for gas turbine combustion, including flashback, NOx emissions, and thermoacoustic instabilities. This work presents a novel jet combustor capable of stabilising highly premixed methane–hydrogen mixtures up to 100% hydrogen without relying on strong recirculation, using a ring of angled pilots. Fuel–air mixing was characterised via laser-induced breakdown spectroscopy (LIBS) for varying composition, equivalence ratio, and bulk velocity. Flame stabilisation was examined in piloted and non-piloted configurations, and thermoacoustic behaviour was quantified. Results show a parabolic fuel distribution, with mixing quality improving at higher momentum flux ratio. In non-piloted flames, hydrogen content strongly affected stability and flame structure, with pure hydrogen producing sharper, more stretch-resistant flames than 90% H2. Piloting extended stable operation to lower hydrogen contents and temperatures, consistently damping oscillations by shifting them to higher frequencies, with benefits largely independent of equivalence ratio. The findings provide new experimental insight into mixing, premixed flame stabilisation, piloted combustion, and thermoacoustic dynamics in high-hydrogen environments, supporting the development of next-generation low-emission gas turbine combustors.

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