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Rodrigues de Vasconcelos Figueiredo, Paulo Alexandre
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- Análise teórica de propelante compósito de base de perclorato de amónia com RDX contendo pequenas partículas de boroPublication . Figueiredo, Paulo Alexandre Rodrigues De Vasconcelos; Brojo, Francisco Miguel Ribeiro ProençaNa indústria aeronáutica/aeroespacial tem-se verificado uma procura de propelantes com melhores desempenhos, menos poluentes e mais eficazes para um motor foguete, o que tem levado a uma evolução considerável no ramo dos propelantes heterogéneos. Neste âmbito tem-se observado a eminente necessidade de conjugar os oxidantes (sendo o mais comum o perclorato de amónia), com as nitramidas (RDX) sob varias concentrações. Actualmente tem-se constatado ainda que a adição de combustíveis metálicos (mais concretamente o alumínio) e a adição de ligantes energéticos contribuem para o aumento dos parâmetros de desempenho de voo, nomeadamente, o impulso específico, o caudal, a velocidade característica, a velocidade dos gases de escape, entre outros. Constata-se ainda que existem combustíveis metálicos promissores para além do alumínio, entre eles o boro, o berílio, o titânio e o magnésio. Esta dissertação visa clarificar e modelar a influência de uma mistura de propelante compósito de base de perclorato de amónia, com o explosivo RDX (Cyclotrimethylene trinitramide), com e sem a adição de partículas finas de boro. Desta forma é possível verificar se o boro é um bom combustível metálico, sendo ou não passível a ser usado nos motores foguete. As propriedades energéticas do boro, assim como o progresso do boro na superfície da queima do grão, são modeladas usando um algoritmo matemático em Matlab. Este estudo visa então comparar dois propelantes muito semelhantes, um com boro e outro sem boro, de forma a compreender e verificar se esta aplicação é viável. Por fim far-se-á um estudo de comparação (apenas complementar) entre o boro e o alumínio a nível de desempenho.
- Optimization of FPSO Glen Lyon Mooring LinesPublication . Figueiredo, Paulo Alexandre Rodrigues de Vasconcelos; Brojo, Francisco Miguel Ribeiro ProençaDuring oil and gas inspection and extraction operations both in deep and ultra-deep water, vessel mooring is a very important factor for the development of oil fields. For these depths, standard stand-alone surface facilities e.g. jack up rigs or offshore fixed platforms are not suitable due to the harsh collinear and non-collinear environment in-situ (location, waves, surface and underwater current, sea tides, ice, etc.). For deep sea wells clusters, it is usual to use floating production storage offloading (FPSO) as surface platforms for long time exploitation periods. Subsea expenditure, refers the cost of the subsea project and generally includes the capital expenditures (capex) and operational expenditures (opex). In the production of hydrocarbons capex and opex exponentially increases with increasing depth, resulting in a need for precise detailed design phase for analysis of systems to verify components strength, ductility and fatigue, stiffness, instabilities, corrosion etc. The design of oilfields is most of the times overrated (in a very conservative way) due to several requirements and complex models of costs evaluation. After detailed phase and installation of all facilities and components, as well as due to the expected life design for hydrocarbons exploitation all anchoring system shall withstand the environmental loads in order to not compromise the operation. Each oilfield has a unique development, since environmental phenomena are unique in each earth location. This work refers to the optimization process of an anchoring system for deep waters in the Schiehallion Field, or in other words, the complete development of the mooring system for a FPSO, from the positioning in-situ with environmental conditions and vessel characteristics (Orcaflex), further optimization of the mooring system for an equivalent system (Matlab), mechanical design of the mooring system (CATIA), structural detailed analysis (Altair and Nastran) as fatigue life analysis. In order to reproduce all the mooring process, it is performed and initial comparison of the former FPSO (Schiehallion FPSO) that has been working in-situ since 1993 till its replacement for the new vessel (Glen Lyon FPSO). Due to the latest discoveries in the oilfield, the project has to be redesigned alongside with former wells and having in consideration recent discovered wells. Further optimization of the complete fixation system was verified as well as finally detailed structural analysis of specific components in key locations with higher margin of failure. Within this work, all the methodology which led to the optimization of Glen Lyon mooring lines was fully detailed from vessel analysis to detailed mooring mechanical design, constraints and requirements were applied, trade-offs and assumptions made during this critical development phase are presented and discussed.