Making Hydrogen Work in Zero Carbon Jet Engines

The European aviation industry has committed to achieving net-zero aircraft propulsion by 2050 by introducing innovative technologies such as hybrid-electric propulsion and hydrogen fuelled gas turbines. Industry expects the introduction of hydrogen to make the greatest contribution to decarbonisation by 2050 with intra-EU routes being powered by hydrogen from 2035 . This Programme Grant (PG) would focus on solving the considerable scientific challenges encountered when cryogenic liquid hydrogen (LH2) is used to fuel gas turbine cycles. The technology for drop in SAF fuelled engines already exists but the economics and society's appetite for scaling up SAF production, which would remove land from food production and reduce biodiversity, imply that SAF will only form part of the zero carbon solution. We note that SAF combustion also adds CO2 to the atmosphere whereas hydrogen emits only water and can be produced carbon-free. Oxford, Imperial College, Loughborough and King's College are all currently working on some of the technology required to introduce liquid hydrogen fuelled gas turbines but this PG would rapidly accelerate UK progress and focus work on the fundamental science that will drive innovation in this field. The partnership between world class universities and industry will ensure that the UK leads the world in hydrogen powered aero-engines. Our discussions and workshops with Rolls-Royce, Airbus, Reaction Engines, ESA and the ATI have confirmed that there is a pressing need to tackle the intractable problem of engineering the cryogenic fuel system and combustor with a focus on the dynamic interaction between these. The key challenges we will address will enable aircraft engines to safely, efficiently and predictably heat and pressurise liquid hydrogen fuel from the cryogenic conditions that is stored at in the aircraft tank to temperatures suitable for injection in the combustor. Automotive technology on the market (for example, in the Toyota Mirai) relies on storing the hydrogen as a compressed gas where the hydrogen temperature changes and thermal challenges are comparatively modest, but the energy density (accounting for the weight of the tanks) is much less than the cryogenic solution required for commercial flight. For completeness, we note that battery energy storage, which leads zero carbon car technology, is almost two orders of magnitude too heavy for aircraft. This proposal addresses the pressing need for fundamental research, including experimental data, for LH2 fuelled turbofans. Our overall aim is to make mid-range commercial flight zero carbon by 2035. We envisage commercial airliners propelled by turbofans but with the kerosene currently burnt in the combustor replaced by green, zero carbon hydrogen. The vision of the PG is to provide the underpinning engineering science to enable the aero industry to replace existing aviation fuel with hydrogen. Our approach is to combine experiments in fluid dynamics and heat transfer together with physical investigations of the effects of cryogenic LH2 on component mechanical properties with bespoke numerical models to make rapid progress in this challenging zero carbon technology. The PG application has been offered support from many industrial partners and world leading academics which will enable the research team to focus on the conditions relevant to decarbonising flight. Our partnership with industry will ensure our research is rapidly disseminated to the colleagues responsible for the future engines and airframes that will deliver zero carbon aviation.