This thesis investigates the performance of vaneless radial and conical diffusers operating with supercritical carbon dioxide (SC-CO2) under various geometric configurations. The motivation arises from the growing interest in compact, high-efficiency turbomachinery suitable for supercritical fluid cycles. The study employs a combination of one-dimensional modelling (1D) and computational fluid dynamics (CFD) to analyse pressure recovery in view of frictional effects and flow separation. All the CFD simulations were conducted using commercial software Ansys CFX 2024 and 2025 integrated into Ansys Workbench and all the coding, including 1D modelling and post-processing was done with Matlab 2024. The performance of SC-CO2 operating diffusers was compared against air simulations at ambient conditions at matched Mach regime. The results show the advantageous pressure recovery of SC-CO2. Furthermore, the comparison between 1D and CFD modelling shows acceptable agreement for low expanding diffusers but reveals significant deviations in outcomes close to separated flow conditions.

Bush planes are general aviation aircraft, that enable transportation to remote areas, where there is no infrastructure supporting regular aviation. Their main features are the taildragger configuration, a short take off and landing distance (STOL) and they offer the ability to land on rough terrain. Paradoxically, although they are the aircraft most directly related to nature, bush planes are often old, polluting and loud, and thus far from being environmentally friendly. To partially overcome these disadvantageous characteristics, Group 12 designed a stateoftheart bush plane, using the principle of distributed propulsion, called the Twin Puffin. In order to design a bush plane, first an understanding is required of the needs and desires of the stakeholders. For this, a market analysis is performed and from this it can be concluded that the aircraft will serve for three main purposes: transport, medical emergency missions and tourism. After obtaining the insight into the market of bush planes, all possible design options are listed. Pruning of unfeasible, unrealistic and inapplicable options is done to end up with seven aircraft concepts. From those concepts, the most suitable and promising is then selected. The aircraft is chosen to be a twin boom concept, therefore the name Twin Puffin was chosen for the design. Following, the design is worked out in detail, where all the subsystems are designed. The fuselage, the structure of the plane, the energy source, the wing, the propulsion system, the empennage, landing gear and electrical systems are designed and optimised, so the final aircraft design is finalised. Inspired by Nature, the bush plane is named the Twin Puffin. ’Twin’ following the distinctive twinboom empennage, and the ’Puffin’, from the bird with a stubby display and a master of short takeoff and landing on the ocean cliffsides, a real inspiration for a STOL aircraft. The featured twin boom empennage make aft loading of cargo or a medical stretcher easy. Furthermore, the distributed propulsion is placed on the wing’s leading edge, allowing unobstructed view during all flight phases, solving the typical visibility issues of a traditional bush plane. The distributed propellers are powered by a hybrid engine using both electricity from batteries and power generated by an internal combustion engine that can run on diesel, jet fuel, and suitable types of biofuels. This allows for an increase in available power and a local reduction in the emissions and noise during electricallypowered takeoff and landing. Furthermore, the distributed electric propulsion lead to excellent STOL characteristics, as the blown air over the wing allow for a large increase in lift at low speeds. Moreover, the Twin Puffin is primarily built of the sustainable material flax fibre composite, making the aircraft more environmentally friendly. The Twin Puffin is estimated to produce 70% less noise and 50% emission, compared to competing aircraft and is thereby a modern, impressively performing bush plane design.