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FE - DCA | Dissertações de Mestrado e Teses de Doutoramento

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http://hdl.handle.net/10400.6/141
Website Departamento Ciências Aeroespaciais

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Browsing FE - DCA | Dissertações de Mestrado e Teses de Doutoramento by Author "Almeida, Gonçalo Freire Pires Bidarra de"

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  • Design and fabrication of a paraffin hybrid rocket engine
    Publication . Almeida, Gonçalo Freire Pires Bidarra de; Brojo, Francisco Miguel Ribeiro Proença
    his dissertation presents the design, construction, and experimental testing of a paraffin-based hybrid rocket motor using nitrous oxide as the oxidiser. The project's goal was to evaluate the regression behaviour of paraffin fuel under realistic conditions and analyse the system’s overall performance. The motor featured a single cylindrical grain configuration and was tested without swirl or combustion enhancement techniques. The average regression rate measured was approximately 1.0 mm/s, consistent with values reported for unaugmented paraffin-based systems. Fuel consumption was uniform along the grain length, and the burned surface exhibited wave-like textures characteristic of liquefying fuels, indicating limited entrainment activity. A significant performance limitation came from the oxidiser feed system. While thermochemical simulations based on an O/F ratio of 6.8 predicted optimal performance, actual tests revealed a much lower oxidiser flow rate (~57 g/s), resulting in a measured O/F ratio closer to 2.25. This discrepancy was attributed to vaporisation issues caused by inadequate injector sizing, heat soak into metallic components, and tank orientation that favoured the drawing of nitrous oxide in the vapor-phase. The low oxidiser mass flux contributed directly to the modest regression rate observed. Despite these limitations, the project showed valuable insights into early-stage hybrid rocket development, particularly the importance of aligning design assumptions with practical flow limitations and thermal considerations. Future improvements should focus on optimising injector area, reducing pressure losses in the feed system, ensuring proper liquid draw from the oxidiser tank, and potentially increasing chamber pressure through nozzle modification. These changes aim to enable higher oxidiser mass flux, enhance thermal feedback, and achieve regression rates more representative of highperformance hybrid propulsion systems.
    2025-07-24Master thesis Open access Show more