OTHERWISE · Control of Hydrogen and Enriched-hydrogen Reacting flows with Water injection and Intensive Strain for ultra-low Emissions

We are racing against time to find a clean, yet abundant, energy source able to arrest global warming. Hydrogen has all the characteristics to address this challenge: it can be produced cleanly from water; it is incredibly energetic; and more importantly, it is carbon-free. However, hydrogens strong reactivity and diffusivity make the control of its flame in energy-generation devices extremely challenging. Moreover, toxic nitric oxides (NOx), a major concern for air quality, are still abundantly produced in a hydrogen flame. Enabling the use of hydrogen requires thus solutions where the flame is stable and with ultra-low NOx at the same time, and at any power setting.In this research I will study, for the first time, the combination of intensive strain and water injection in the context of lean premixed combustion. My preliminary research has indicated that intensive strain improves the reactivity of the hydrogen flame and simultaneously pushes the NOx down significantly, a property yet to be understood. Water injection further pushes down the NOx, but it commonly causes flame extinctions and inefficiencies. Its combination with hydrogen and intensive strain, by enhancing the flame, offers a way of surpassing these limitations, and further allows to operate the flame at richer conditions, so preventing common instabilities from occurring in lean premixed combustion.The objective of this research is to push the hydrogen flame into a high-strain regime characterised by stable flame and ultra-low NOx, and find the extreme limits and physical knowledge allowing full control of the reacting flow in such a regime. The flame dynamics, still unknown in this regime, will be explored for the first time and fully characterised in this research by using high-fidelity simulations, experiments and theoretical analyses. The gathered understanding will allow the control of hydrogen flames at any power setting. This will pave the way for the exploitation of green energy.