Much like the oil crisis in the 1980s, the aviation industry is once again considering more environmentally sustainable propulsion options due to concerns around climate change. More fuel efficient propulsion methods form the pillar on which environmentally sustainable aviation can be built, since it is the propulsion system that emits harmful greenhouse gasses. The propulsion system consists of an energy carrier, currently kerosene, and an energy to thrust converter, often a jet engine. Although efficiency gains are being made, using kerosene and jet engines will prove infeasible in the long run due to global warming concerns. Replacing the jet engine with a propeller offers an attractive solution since propeller shaft power can be supplied by batteries or fuel cells. Furthermore, propellers are relatively efficient due to their infinite bypass ratio. Additionally, a surge in demand for Urban Air Mobility [3] incentives propeller optimisation studies. Aircraft are a combination of complex and interacting systems. For this reason it is important to consider interactions between wings and propellers when designing either. Propeller-wing optimisation is therefore an increasingly important topic. Propeller-wing optimisation literature is scarce, likely due to the complexity of a coupled propeller-wing system. Optimising a propeller-wing system is possible with high-fidelity simulations but often takes a substantial amount of time. The aim of this research is to address the lack of coupled propeller-wing aerostructural optimisation. The knowledge gap is addressed by designing a novel coupled propeller wing framework that is suited for computationally efficient optimisation studies. Furthermore, the optimisation framework will be modular such that it can be easily extended. The ability to expand the framework increases the scope and impact of this research...

The increasing demand for sustainable aircraft solutions has encouraged the development of non-CO􁊼 emitting aircraft designs. Currently, a number of theoretically successful designs have been created by parties such as the Massachusetts Institute of Technology, National Aeronautics and Space Administration, and The Technical University of Delft. Unfortunately, these radical aircraft redesigns are too risky to conceive, requiring massive amounts of investment and research. Since growth of the global aviation industry will only persist if aircraft greenhouse gas emissions are reduced, airlines have been looking for more fuel efficient aircraft, and the demand for green solutions has skyrocketed1. Thus, in this study the A320appu is proposed in an effort to significantly decrease the environmental footprint of aviation while limiting the risks and cost that accompany novel designs. This is done trough a conversion of the A320neo to use a hybrid, multi-fuel power and propulsion system. By replacing the traditional kerosene Auxiliary Power Unit (APU) with a hydrogen engine and an aft mounted, boundary layer ingesting propulsor, the design will enter the narrow-body market as an intermediate step between current generation kerosene-powered aircraft and more distant radical redesigns, like the Flying V2 or the Aurora D8 3. The APU is thus adapted into an Auxiliary Power and Propulsion Unit (APPU). This single aisle, short-medium haul airliner was specifically chosen for this conversion because aircraft of this class are expected to comprise 80% of all aircraft sales by 2038. The reconfigured A320neo, coined the A320appu, shall provide an economically feasible and green alternative. It shall be the first advance towards normalising hydrogen within the aviation industry.

The challenges of designing the A320appu are to maintain low development costs, integrating the cutting edge subsystem and reassessing aircraft parameters such as the stability and controllability or range. Moreover the Operating Empty Weight (OEW) increases because of the added subsystems, and as the A320appu is designed for the same Maximum Take-off Weight (MTOW), the available payload decreases. The A320appu is designed such that the increase of the OEW is minimised, while maximising the integrability by limiting the amount of changes to the A320neo. Furthermore, significant reduction of the 𝐶𝑂􁊼 emissions and local pollution have to be ensured, while providing similar performance to the A320neo. To achieve the aforementioned points, four main changes to the A320neo are proposed below and thereafter discussed in more detail.