FE - DCA | Dissertações de Mestrado e Teses de Doutoramento
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- Development and Experimental Test of an In-Flight Thrust and Torque Measuring SystemPublication . Simões, Rafael da Conceição; Brojo, Francisco Miguel Ribeiro Proença; Soares, Marcelo de PinhoThis thesis details the design, development, and validation of an in-flight thrust and torque measurement system, aimed at optimizing the performance of UAV powerplant systems through real-time data analysis. The system was integrated into TEKEVER’s AR3 UAV and subjected to a multi-phase testing approach encompassing controlled dynamometer (dyno) tests, static testbench trials, and dynamic flight testing under real operational conditions. These tests allowed for a detailed examination of the engine-propeller system’s behavior under varying load scenarios, including different airspeeds, aerodynamic forces, and throttle settings. Findings from this study underscore the significant impact of real-flight conditions on engine and propeller performance, with observed reductions in engine speed, power, and thrust when compared to static ground test results. These reductions are attributed to the aerodynamic forces encountered in flight, such as drag and wind resistance. A critical outcome of the research was the ability to cross-check the thrust values obtained during cruise with the aerodynamic drag on the UAV, which allows for improved calibration of the company’s Computational Fluid Dynamics (CFD) model. This cross-verification process not only supports more accurate predictive modeling but also provides a foundation for enhancing future powerplant and propeller matching studies. Additionally, the study highlights the effectiveness of the in-flight measurement system for capturing detailed thrust and torque data under operational conditions, providing a robust baseline for evaluating engine-propeller combinations in real time. This research contributes essential advancements in UAV performance optimization, offering new methodologies for measuring and analyzing powerplant efficiency under flight conditions. This project was fully funded and supported by TEKEVER UAS, whose resources, technical support, and expertise were instrumental in the successful execution of this research.
- Estudo da viabilidade da otimização da área de produção dos painéis WP3 da Airbus Atlantic PortugalPublication . Marques, Erika Almeida; Saúde, José Manuel Mota Lourenço da; Moutinho, Sandra Cristina PimentaA dissertação foi desenvolvida na Airbus Altantic Portugal. Este trabalho teve como objetivo o estudo da viabilidade da otimização da área de produção dos painéis WP3 através da redução do lead time do produto, aplicando ferramentas de melhoria contínua, baseadas na filosofia Lean Production de modo a aumentar a eficiência e o desempenho do processo produtivo. O estudo inicia-se com uma revisão das ferramentas Lean, tais como Value Stream Mapping, 5S e standard work, que visam minimizar o desperdício e melhorar o desempenho operacional. O caso de estudo envolve o diagnóstico da situação atual do processo produtivo, identificando problemas e oportunidades de melhoria. Através da implementação de ferramentas Lean, foram propostas soluções para reduzir os tempos de paragem, reorganizar os postos de trabalho e reduzir as atividades sem valor acrescentado. Os resultados demostram melhorias de 3% e 6% de redução do tempo útil de produção dos painéis inferiores e superiores, respetivamente, bem como uma redução do tempo de reparações. A dissertação conclui destacando a aplicação bem sucedida das ferramentas Lean no setor de fabricação aeronáutica e com sugestões de trabalhos futuros, incluindo a integração de um sistema enterprise resource planning para monitorizar os processos e um seguimento do trabalho realizado para garantir a sustentabilidade das melhorias implementadas.
- Desenvolvimento de uma Impressora 3D de Grande Volume para Prototipagem Rápida de Corpos AerodinâmicosPublication . Pereira, Marcos Regino Cabral; Silvestre, Miguel Ângelo RodriguesNa Universidade da Beira Interior existe uma necessidade crescente de ferramentas disponíveis para o fabrico de protótipos que são utilizados em variados projetos e trabalhos desenvolvidos. Com ênfase na construção de corpos aerodinâmicos em materiais compósitos, através de laminação em moldes, surge a falta de ferramentas e métodos de fabrico de moldes de forma rápida e barata. Uma solução passa pela criação de uma máquina de fabrico aditivo, para produzir moldes ou modelos das peças desejadas. Esta máquina será de grande volume pois as mais comuns não têm tamanho suficiente para fabricar as peças pretendidas de uma só vez. O principal objetivo deste trabalho foi o desenvolvimento e montagem de uma impressora 3D com 900 x 900 x 1000 mm3 de volume, do tipo FDM, tendo por base a história da impressão 3D e os fundamentos teóricos desta tecnologia que são apresentados. Foi tida em conta a minimização dos custos e a minimização do movimento das peças com maior massa. Esta impressora usa o chão e o teto da sala para benefício estrutural e tem uma configuração de movimento Core XY. A máquina foi desenvolvida e montada com sucesso respeitando os parâmetros iniciais e foram feitos testes de impressão que validam o seu bom funcionamento. Contudo, ainda existe margem de melhoria e de implementação de outras configurações. É também descrito um processo de moldagem que usa gesso e juta como materiais, sendo o resultado de uma das aplicações da impressora 3D desenvolvida.
- Piezoresistive Sandwich Structures: Assessing the viability of additive manufacturing and real-time monitoring for aerospace applicationsPublication . Moura, João Carlos Silva; Silva, Abílio Manuel Pereira da; Pereira, João Pedro Nunes; Aguiar, Martim Lima deThe use of composite materials, especially laminates and sandwich materials, has been currently experiencing significant growth, both qualitatively and quantitatively; this fact is owed to their advantages over traditional options, namely with regards to their resistance to fatigue, stiffness and relatively low weight. These factors contribute to their preference in transport-related applications, namely in the aerospace industry. Simultaneously, recent advances in manufacturing techniques and a paradigm shift towards favouring materials and components that independently integrating multiple functions indicate an undeniable potential for the improvement of the manufacture and functionality of these same composites. In this work, several beam-type samples were developed according to the principles of a sandwich-type composite, where the traditional fabrication for a laminate is complemented by additive manufacturing techniques and the additional inclusion of a piezoresistive component to promote an electrical monitoring capability, with the objective of demonstrating the viability of such a configuration of elements in a single component. Furthermore, three different types of cores were created for the sandwiches – with hexagonal, auxetic (re-entrant) and cubic cells – with the intention of emphasising the advantages and disadvantages of the various types of cells, namely those of a geometry only made possible by resorting to additive manufacturing. These efforts highlighted the cubic geometry for its greater energy absorption: up to 273 % greater than other geometries; the highlight of the auxetic geometry was a superior strain at the yield point: up to 196 % further than the other options; and the highlight of the hexagonal was an inferior decline in stress and elastic modulus over cycles: up to 26 % of that observed for both values in other geometries. Furthermore, all geometries achieved a high-quality piezoresistive response, demonstrating multifunctionality.
- Enhancing Smart City Capabilities with the Integration of Unmanned Aircraft Systems: Unlocking Porto s PotentialPublication . Barateiro, João Gonçalo Lopes ; Dias, Veruska Mazza Rodrigues; Silva, Jorge Miguel dos ReisThe increasing number of urban residents presents growing challenges that require innovative and efficient solutions. Cities are looking for smarter approaches, which involve the optimization of resource usage and the improvement of public services, with the aim of enhancing the quality of life and overall satisfaction of residents through sustainable practices. Current and emerging innovative technologies provide effective tools for addressing urban challenges. Unmanned Aircraft Systems (UAS) present a valuable solution, due to their versatility, flexibility, efficient data collection methods, and lower environmental and economic impact compared to other technologies (e.g., helicopters, general aviation aircraft). UAS have been extensively studied as they offer a large variety of urban applications, such as monitoring, traffic management, and infrastructure inspection. In the near future, they are also expected to start carrying passengers and delivering goods in Europe, contributing to the development of Urban Air Mobility (UAM), a priority among the European Union’s (EU) sustainable urban mobility initiatives. This work proposed the application of a Strengths-Weaknesses-Opportunities-Threats (SWOT) analysis to qualitatively evaluate the key factors influencing the implementation of UAS in Porto, alongside the use of the TOWS matrix to define strategies of implementation. The Fuzzy Analytical Hierarchical Process (FAHP) was used to identify the most relevant factors from the perspective of respondents with expertise in various relevant fields. Other quantitative methods were also applied to establish a prioritization order for the proposed strategies, aiming to identify initiatives that would position Porto closer to widely recognized smart cities. The obtained results were validated in a partnership with a UAS sector company based in the city under study. The combination of both stages allowed for the conclusion that Porto has significant potential for the implementation of UAS within the smart city paradigm. Among the key favourable factors are the city’s proactive, dynamic and collaborative nature - regarding the urban environment, and the environmental sustainability intrinsic to UAS – regarding the vehicle itself. Additionally, the potential for creation of jobs and business opportunities with the development of this industry emerged as the major benefit of this implementation. However, the study highlighted also substantial concerns regarding both the fragility of the current legislative framework and its constantly evolving nature, as well as the inherent complexity, all of which amplify the challenges associated with safety and security.
- Squish Band Influence on a Piston Ported 2-Stroke Engine PerformancePublication . Silva, Vítor Alexandre Pinheiro da; Brojo, Francisco Miguel Ribeiro ProençaTwo-stroke engines are widely used worldwide in applications where lightweight design, high power-to-weight ratio, and simplicity are essential. Common modern uses include motorcycles, marine engines, and small machinery. In the aeronautical sector, they are especially valuable in unmanned aerial vehicles (UAVs) for both civilian and military purposes, where their high power-to-weight ratio is critical for performance. They are also used in ultralight aircraft, aeromodelling, and experimental aviation due to their compact design and cost-effectiveness. Advances in technology continue to improve their performance, solidifying two-stroke engines as a reliable and indispensable part of both aviation and the entire transport sector. This study intends to analyse the influence of the squish band on the combustion efficiency and performance of two-stroke engines. For that, a small 50cc two-stroke piston ported SI engine was designed from scratch to serve as the base for the analysis. The squish band of the designed engine was then altered in three different characteristics: the gap to the piston crown at top dead center (TDC), the angle of the squish band and the percentage of the piston’s bore area where a squish band was present. With these modifications, a total of six different variations of the base engine were created and analysed. The numerical simulations were performed in ANSYS Fluent. In this CFD software, the engine’s motion through its cycle and the species movement and combustion were modelled and the different calculations were computed. The results revealed that the designed engine performed as expected and the different squish band variations provided interesting results.
- Development of new Water Landing Infrastructures and ProceduresPublication . Gabriel, Vasco João Capote; Silva, Jorge Miguel dos Reis; Soares, Paulo Alexandre Ramos de FigueiredoThis Master Dissertation arises from an analysis of accidents in Portuguese territory involving water landing and ditching emergencies. The concern regarding this topic was primarily raised by Gabinete de Prevenção e Investigação de Acidentes com Aeronaves e de Acidentes Ferroviários (GPIAAF). Over the past years, Portugal has experienced several accidents of this type, some fatal, which involved or should have involved an in-depth study of the process of water landing and its specificities. It is therefore evident that there is a failure regarding the characteristics of the dedicated water landing infrastructures, as well as an effective risk assessment and flight crew training related to this aspect. This Master Dissertation not only addresses an analysis of historical occurrences, and the lessons retrieved up from them but also the current applicable regulations, to make possible to propose new water landing infrastructures equipped with operational support elements that could assist aircrafts in regular operations as well as emergency situations, if the decision is to ditch the aircraft. For this purpose, two locations are proposed for such infrastructures at two distinct dams, Marateca and Aguieira, being the first near Castelo Branco and the latter on near Viseu. The proposed location of these infrastructures is based on the initial condition that the areas for operation are well defined and marked out, thus avoiding the risk of incursion into them by third parties who are unaware of the delimitation of these restricted areas of operation. It also accounts for the existence of means of rescue, not only for normal operations, but especially in the event of an accident, namely search and rescue means for immediate reaction. It is also proposed to build up the infrastructure on the ‘land side’ with hangars, parking bays and taxiways, which can be used by amphibious or rotary-wing aircraft, while aircraft/crews can move from the maritime to the land environment via docks or access ramps. Moreover, access roads, suitable car parking slots, and restaurants, for example, can have a double-use, for both complementary aerial emergency activities and for tourism purposes, for example. Means for ensuring safety and separation of “airside” to the “landside” are also proposed. This entire study is based on current regulations to ensure the necessary safety and compliance. To ensure that the proposed infrastructure is operation viable, it will be necessary to provide for the most rigorous risk assessments possible, which in terms of crew training will lead to the implementation of new training methods, not only in the theoretical component, but mainly in terms of instruction and flight training, which should be transversal to any Approved training Organisation (ATO). This study is based on the requirements of international and national legislation, which include theoretical and practical training, as well as key points that must be addressed during the training stage. In addition, these points are based on the prerequisites needed to obtain an amphibious aircraft pilot's licence. For this study, and while developing this dissertation, only the crucial flight phases involving the use of the proposed infrastructure have been considered.
- Aplicação de Modelos de Machine Learning para Classificação de Mecanismos de Falha e Deteção de Fissuras em Ligas Metálicas AeronáuticasPublication . Figueiredo, Tomás Carvalho; Gamboa, Pedro Vieira; Barros, Tomás ; Santos, BrunoO presente trabalho explora a aplicação de dois modelos baseadas em machine learning, nomeadamente redes neuronais convolucionais, para avaliação de falhas em ligas metálicas de componentes aeronáuticos da Força Aérea Portuguesa. O primeiro foi projetado para a classificação de mecanismos de falha utilizando imagens obtidas através do microscópio eletrónico de varrimento, enquanto o segundo se foca na deteção de fissuras de fadiga. Para a tarefa de classificação foi utilizada uma arquitetura VGG16, ajustada com uma classification head e treinada utilizando técnicas de transfer learning. Para a deteção foi implementado um modelo baseado em Faster R-CNN com ResNet 101 e Feature Pyramid Network, pré-treinado e configurado para identificar e localizar fissuras de fadiga de vários tamanhos. Ambos os modelos foram treinados e validados em conjuntos de dados anotados manualmente e com recurso a técnicas de data augmentation. O modelo de classificação atingiu uma exatidão de aproximadamente 93% e precisão de 92%, enquanto o modelo de deteção apresentou uma exatidão de cerca de 89% e precisão de 90%. Estes resultados destacam a capacidade das redes neuronais convolucionais em automatizar tarefas complexas, reduzindo o tempo de análise de grandes quantidades de imagens de uma só vez.
- Aerodynamic Analysis of a Two-Man BobsleighPublication . Ribeiro, Simão Rafael Silvério; Gamboa, Pedro VieiraBobsleigh is a highly competitive winter sport in which technological advancements play a crucial role in optimising performance, with aerodynamics being a key factor in race outcomes. This study presents a comprehensive aerodynamic analysis of a two-man bobsleigh using Computational Fluid Dynamics (CFD) simulations to investigate flow structures and drag sources, with the objective of improving aerodynamic efficiency through geometric modifications. A baseline bobsleigh geometry was developed using photographic references of high-performance designs from recent competitions. CFD analyses were conducted in ANSYS Fluent, employing the Realizable ?? - ?? turbulence model with Non-Equilibrium Wall Functions for near-wall modelling. Key aerodynamic characteristics, such as flow separation regions and pressure distributions were identified and studied. Simulations were performed at two distinct free-stream velocities: 15 ??/??, representative of the late push start phase, and 35 ??/??, corresponding to race-speed conditions. Additional analyses were conducted to evaluate the influence of confining walls in straight track sections on bobsleigh aerodynamic performance. Based on these findings and existing research, an iterative design process was conducted to develop an improved geometry aimed at reducing aerodynamic drag. The enhanced design incorporates modifications to the front bumper, ground clearance, and diffuser geometry, resulting in a 6.37% reduction in aerodynamic drag and a 3.14% increase in maximum speed.
- Application of eVTOL Aircraft in Advanced Air Mobility: Vertiport in Humberto Delgado AirportPublication . Nave, Tiago Anseriz da; Silva, Jorge Miguel dos ReisTechnological developments allowed air mobility to enter the urban environment, expanding urban mobility to a new dimension and originating Advanced Air Mobility (AAM). The present work explores the potential of a vertiport, AAM's ground infrastructure, associated with Humberto Delgado Airport, allowing its connection to the new Luís de Camões Airport. There are still many obstacles in the path to implementing a route taken by a recent category of aircraft, eVTOLs, in an industry that does not accept safety compromises. Various aeronautical authorities have released documentation to guide the development of vertiports. Yet, their transitional nature alongside the uncertainty around accordingly expanding air traffic control (ATC) and other operational uncertainties leads to significant doubt of the longevity of the models used so far. Aiming to reduce the impact of the many uncertainties, a vertiport implementation was sought while pondering proper specifications and public exposure to the negative side of AAM, pointing out identified sources of uncertainty and explaining the decision process for each step. Reaching a recommended layout for the case of study, a simulation model was then elaborated to estimate its performance, identify bottlenecks and confirm assumptions made during the layout design phase. The reached conclusions reflect a lack of validation of the claims surrounding AAM, translated on rigorous EASA guidance material for vertiport design, restricting the options for a vertiport associated with Humberto Delgado Airport. Considering data from August 2024, the developed vertiport, under various limitations such as visual flight rule (VFR) conditions and considering Volocopter’s VoloCity as the eVTOL, proved capable of serving 0.398% of the airport's daily processed passengers. The proposed vertiport’s performance can be seen as adequate for the expected demand on this initial stage, with few passengers seeking a direct connection between the airports and not taking another means of transport. On the other hand, expansion options are lacking, compromising the capacity of ground infrastructure in case of the concept's success. Additionally, as soon as infrastructure projects seeking an expansion of ground transport capabilities are completed, while still many years in the future, AAM may face serious competition from the more conventional transport means.