Proposals should:

• Establish accurate experimental data and reliable model estimates about the burning rate and the boundaries of static flame stabilisation (flashback and blow-out avoidance) in turbulent premixed combustion of hydrogen-enriched fuel blends (up to 100% H2) from atmospheric to high-pressure conditions (up to 10 bar, at least).
• Accurately predict the thermo-acoustic response and the boundaries of dynamic flame stabilisation (combustion dynamics control) in turbulent premixed combustion of hydrogen-enriched fuel blends (up to 100% H2) from atmospheric to high-pressure conditions (up to 10 bar, at least).

The above-mentioned two points can be achieved by exploiting a combination of first-principle numerical simulations, to minimize the modelling assumption, and advanced optical measurements, to obtain an accurate characterization of the flames across the pressure range investigated.

• Establish the optimal combustion process and combustion system layout, fuel injection and fuel staging strategies that simultaneously achieve the most robust flame stabilisation and the best low-NOx performance for different hydrogen-enriched fuel blends (e.g. with ammonia or natural gas) at high-pressure conditions. This can be achieved by developing numerical modelling and experimental testing of advanced, less generic and more specialized, combustion systems at laboratory scale (TRL 3-5), featuring novel fuel injection concepts and combustion staging strategies, with downscaled prototypes simulated and tested in laboratory facilities spanning atmospheric to high-pressure conditions (up to 10 bar, at least). Flame stability and emissions performance should be compared between alternative designs based on different fuel injection and staging strategies.

Although not strictly required to develop fuel-flexible combustion system layouts and innovative solutions, the involvement of a Gas Turbine Original Equipment Manufacturer (GT OEM) in the relevant research activities should be considered of crucial importance to significantly strengthen the industrial relevance of the research and its applicability and transferability to gas turbine applications.

The numerical and experimental methodologies should be selected to achieve a clear analytical differentiation between concurrently occurring and tightly interconnected processes, i.e. the increase in bulk Reynolds number and thermo-diffusive instabilities with pressure with the variation in chemical reactivity. In order to ensure that the principal rate-controlling processes and their trends are correctly and accurately captured at relevant conditions, laboratory experiments and numerical modelling efforts should target a pressure range covering a significant portion of the range relevant in gas turbine operation. Therefore, as a minimum requirement, the pressure range comprised between 1 and 10 bar should be investigated using state-of-the-art numerical modelling and experimental measuring techniques, i.e. featuring detailed optical diagnostics of the flame geometrical characteristics, of its stabilisation, structure and response to acoustic forcing.