Evaluation of technology and energy vector combinations for decarbonising future subsonic long-range aircraft

Global aviation demand and its climate impact are forecast to increase significantly in the next two decades. The broader aim of this thesis is to evaluate aircraft technology and low-carbon energy-vector combination(s) considering lifecycle effects for enabling climate-neutral subsonic long-range flight (14,000 km) of a large aircraft (~300 passengers) – a challenging domain to decarbonise. Firstly, using Breguet’s range equation it is observed that liquid hydrogen (LH2) and 100% synthetic paraffin kerosene (SPK) are the only two alternative fuels found suitable for this domain. Using present-day technology, the specific energy consumption (SEC in MJ/tonne-km) of LH2 and 100% SPK aircraft are 11% higher and 0.2% lower relative to Jet-A, respectively. Secondly, a global sensitivity analysis is conducted using the range equation to study the impacts of four technologies – aerodynamics, lighter structures, cryo-tank weight, and overall efficiency (𝜂o) – on the design-point performance of a tube-wing LH2 aircraft. Relative to the present-day technology, it is observed that for an LH2 aircraft: (i) improving 𝜂o and aerodynamics dramatically improves its SEC; and (ii) using the most optimistic technology development estimates, its SEC improves by 33% requiring a 22% longer fuselage. Thirdly, by using weight sizing methods and GasTurb simulation, it is observed that the SEC of a futuristic BWB aircraft powered by Jet-A, 100% SPK, and LH2 decreases by 47.9%, 48% and 53.5% relative to the present-day Jet-A aircraft, respectively. Lastly, a comparative life-cycle analysis is conducted for these three BWB aircraft while quantifying both CO2 and non-CO2 effects. After examining over 100 manufacturing feedstocks/pathways for 100% SPK and LH2, it is observed that only LH2 could enable a climate-neutral long-range flight using fuel manufactured from biomass-based manufacturing unit employing carbon sequestration. The findings of this thesis could guide and enable more informed decision making in future aviation technology development and policy making.