Introducing H ₂ as fuel in gas turbines is a promising step towards decarbonizing the energy sector. However, the future availability of H ₂ in large quantities remains uncertain. Consequently, designing fuel flexible (CH ₄/H ₂) combustion chambers for various fuel blends is necessary. The distinct combustion characteristics of H ₂, such as high flame speeds and high adiabatic flame temperatures, pose challenges when designing systems that can operate in a stable manner and with low emissions across a wide range of fuel mixtures. This paper investigates the fuel-flexibility of an atmospheric laboratory scale, partially premixed swirl stabilized combustor. By deploying a non-rotating axial air jet (AAI) in the center-line of the swirling flow, the flashback risk for high H ₂ content fuels is minimized. This study provides detailed insights into AAI's interaction with CH ₄/H ₂ fuel blends, analyzing the resulting flow field from Particle Image Velocimetry, emissions from exhaust gas analyser measurements, and flame structures from OH* chemiluminescence and OH Planar Laser Induced Fluorescence. The results show that AAI enables flame stabilization across the full range from 100% CH ₄ to 100% H ₂ in the same injector geometry. However, a high portion of the total airflow must be injected axially to stabilize H ₂ flames. Increasing the level of AAI increases NO emissions and alters flame stabilization mechanisms. This is likely due to a decrease in mixing quality, resulting in the fuel staying close to the periphery of the mixing tube. Switching the fuel from 100% CH ₄ to 100% H ₂ leads to an increase in NO emission, despite lower adiabatic flame temperatures for the perfectly premixed case. This indicates that the mixing process and flame location within the combustion chamber are essential in controlling NO emissions. Moreover, the flow field transforms significantly from a swirl-stabilized flow field featuring an inner recirculation zone to one resembling the one of a jet flame.

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Decarbonization of the energy sector by switching to low-carbon renewables is inevitable for a sustainable future. However, the intermittent and variable nature of low-carbon renewables, like wind and solar, poses several challenges when integrated into the existing energy grids. This is one of the main factors slowing down the transition to a more sustainable energy model. Long-term energy storage solutions are expected to alleviate these issues. The technologies currently available for this application (PHS and CAES) have a limited sustainable deployment potential which makes power-to-gas (P2G) technology, the only long-term strategy that can ensure decarbonization of the future global economy. Green hydrogen, a fundamental part of this concept, is the critical energy technology that can catalyze a paradigm shift in the existing energy markets. Yet, a widescale deployment of this technology is currently limited by several factors including low overall conversion efficiency, poor scalability and operational unreliability of fuel cell technology, high overall costs, absence of necessary infrastructure etc. This research project aims to propose a highly efficient combustion-based power cycle that can address several issues commonly associated with H2-based power generation application of the fuel-cell technology. Preliminary analysis identified that the s-CO2 Brayton cycle was the most suitable candidate for this application and thus, a thermodynamic analysis was conducted to determine the feasibility for this solution. This report documents the work completed in this project and proposes a novel oxy-combustion based green H2 fuelled s-CO2 power cycle concept as an alternative to the existing H2-based distributed power generation systems.