AbstractsTransportation

A thorough redesign of the aircraft industry is needed to cope with diminishing fossil fuel reserves, including operation, aircraft design and propulsion systems. The European Commission sponsors the RECREATE research project to investigate the cruiser-feeder set-up, in which cruise-optimised aircraft stay aloft for extended periods while feeder aircraft transport payload and/or fuel between the ground and the cruiser. This study focusses on the design of a cruiser aircraft that uses nuclear power to transport up to 1000 passengers so that its endurance is only limited by maintenance intervals. Even though the Cold War produced some design options for nuclear aircraft, new research is needed to assess this concept’s feasibility in the near future aircraft industry. RECREATE has provided a preliminary layout for the cruiser aircraft, however weight estimation of the propulsion system that converts reactor power into propulsion proves to be a major hurdle in assessing the feasibility of the cruiser design. Within the 1 million kg weight budget that has been set, 100,000 kg is reserved for each heat cycle. Therefore, this study sets out to design a weight optimised heat cycle. The primary cycle reactor coolant is selected to be LBE because of its inherent radiation shielding and heat transfer properties. Outside of the shielding vessel, three options are investigated for the secondary cycle: an open cycle using FLiBe as a working fluid, and a regenerative and recompression lay-out of closed cycle using s-CO2. Because LBE limits the output temperature, only the closed cycles prove feasible in this study. An optimisation process consisting of an initial grid search and a final optimisation is used to minimise the weight of heat exchangers and piping of the system, whilst leaving turbomachinery and driveshafts to be optimised in other studies. The regenerative cycle comes out as the lightest thanks to its reduced number of components and lower mass flow. After the optimisation the minimum weight cycle has an overall thermodynamic efficiency of 45.4% using a maximum pressure of 60.5 MPa, with the designed components weighing 65,600 kg. This leaves a budget of 34,400 kg for the systems that were excluded. This is considered more than sufficient to state that the heat cycle weight remains within the required 100,000 kg. The nuclear cruiser requires comprehensive additional research and validation, such as a detailed design of the reactor and safety features. The results of this thesis also have to be corroborated by further calculations, simulations, and experiments. Nevertheless, this research has provided an important initial assessment of nuclear-powered propulsion for civil aviation. Advisors/Committee Members: La Rocca, G..