Exploration of sustainable aviation technologies and alternative fuels for future inter-continental passenger aircraft

Abstract

Global aviation demand and its environmental impact are projected to grow significantly in the next two decades. The primary objective of this thesis is to assess aircraft technology and low-carbon energy combinations, considering lifecycle effects, to enable climate-neutral subsonic long-range flight (14,000 km) for a large aircraft (~300 passengers) – a complex area to decarbonize. First, using Breguet’s range equation, it is found that liquid hydrogen (LH2) and 100% synthetic paraffin kerosene (SPK) are the only alternative fuels suitable for this sector. With current technology, the specific energy consumption (SEC in MJ/tonne-km) of LH2 and 100% SPK aircraft are 11% higher and 0.2% lower compared to Jet-A, respectively. Second, a global sensitivity analysis is performed using the range equation to investigate the effects of four technologies – aerodynamics, lighter structures, cryo-tank weight, and overall efficiency (𝜂o) – on the design performance of an LH2 tube-wing aircraft. Compared to current technology, it is found that for an LH2 aircraft: (i) enhancing 𝜂o and aerodynamics significantly reduces its SEC; and (ii) with the most optimistic technology projections, its SEC improves by 33%, requiring a 22% longer fuselage. Third, by applying weight-sizing methods and GasTurb simulations, 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%, respectively, compared to a present-day Jet-A aircraft. Lastly, a comparative lifecycle analysis is conducted for these three BWB aircraft, quantifying both CO2 and non-CO2 impacts. After evaluating over 100 manufacturing pathways/feedstocks for 100% SPK and LH2, it is found that only LH2 could achieve climate-neutral long-range flight when produced from biomass-based sources with carbon sequestration. The findings of this thesis could help guide future aviation technology development and policy decisions.