Mestrado em Engenharia Mecânica

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http://repositorio.ufes.br/handle/10/17622

Nível: Mestrado Acadêmico
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Agora exibindo 1 - 5 de 287

Evaluation of engineering ceramics and cermets performance in high-stress abrasion
(Universidade Federal do Espírito Santo, 2025-07-08) Sousa, Natália de Oliveira; Scandian, Cherlio ; https://orcid.org/0000-0002-4393-719X; http://lattes.cnpq.br/8466752738430250; Strey, Nathan Fantecelle ; https://orcid.org/0000-0002-2568-116X; http://lattes.cnpq.br/3613706957012460; https://orcid.org/0009-0002-6858-560X; http://lattes.cnpq.br/4123866993043725; Sinatora, Amilton ; https://orcid.org/0000-0002-5004-4947; http://lattes.cnpq.br/2988437176012972; Penagos, Jose Jimmy ; https://orcid.org/0000-0003-2879-4722; http://lattes.cnpq.br/5197354360810183
Este trabalho de mestrado investiga o comportamento do desgaste de cerâmicas de engenharia e cermet (Al2O3, ZrO2, ZTA, B4C e PCD), em comparação ao metal duro WC/Co — um material atualmente adotado como referência para sistemas submetidos a desgaste abrasivo severo, especialmente os sistemas de prensa de rolos de alta pressão (High Pressure Grinding Roll– HPGR), utilizados na cominuição de minério. O ensaio de abrasão de alta tensão ASTM B611-21 foi selecionado por sua capacidade de classificar a resistência ao desgaste de materiais duros em condições que envolvem fragmentação de partículas abrasivas. Embora o procedimento da norma ASTM B611 especifique a alumina 30-grit como abrasivo, também foi utilizada a Areia Normal Brasileira– IPT para simular condições menos severas. Inicialmente, o equipamento de abrasão previamente construído em laboratório foi validado utilizando-se a alumina como abrasivo, enquanto o comportamento do desgaste foi avaliado principalmente com areia, ambos os procedimentos de ensaios realizados a 200 N. A resistência ao desgaste foi correlacionada com as propriedades mecânicas e características de cada material. A areia foi aproximadamente dez vezes menos severa que a alumina nos ensaios com WC/Co e ZTA. Dentre todos os materiais testados com areia, o PCD apresentou a menor taxa de desgaste (2 × 10−4 mm3/m), dez vezes inferior à do WC/Co (2 × 10−3 mm3/m), enquanto a Al2O3 apresentou a maior (7.1 × 10−1 mm3/m), 350 vezes superior. A segunda etapa explorou o efeito da carga e do tipo de abrasivo sobre o desgaste. Para simular condições mais realistas, utilizaram-se a areia padrão e o pellet feed, um dos principais constituintes do minério de ferro, a 65 N e 130 N. ZrO2, B4C, PCD e WC/Co foram selecionados para investigação adicional, tendo suas taxas de desgaste e os mecanismos de desgaste correlacionados com suas propriedades. OPCDmanteve-se como o material de melhor desempenho (7×10−5–3.5×10−4 mm3/m), apresentando taxas de desgaste próximas às do WC/Co. O B4C também se mostrou promissor em condições menos severas (por exemplo, 2−6×10−4 mm3/m com pellet feed). A ZrO2, anteriormente a cerâmica de melhor desempenho nos ensaios a 200 N com areia, apresentou taxas de desgaste de uma a três ordens de grandeza superiores às do WC/Co. Nos ensaios com alumina e areia como abrasivos, foi detectada a cominuição abrasiva, especialmente para partículas menores na distribuição granulométrica dos abrasivos. O estudo concluiu que o WC/Co permanece como escolha claramente justificada para aplicações de abrasão severa, particularmente em sistemas HPGR, mas também destaca o potencial de compósitos cerâmico-metálicos como o PCD e a aplicabilidade das cerâmicas de engenharia, a depender da severidade abrasiva do sistema
Previsão da distribuição do tamanho de gotas em escoamento de emulsões por modelo de balanço populacional: simulação numérica e experimentos
(Universidade Federal do Espírito Santo, 2025-03-20) Elias, Murilo Zucatelli; Ramos, Rogério; https://orcid.org/0000-0003-4493-2435; http://lattes.cnpq.br/2975022316691139; https://orcid.org/0009-0009-7422-2101; http://lattes.cnpq.br/6373443252232198; Lage, Paulo Laranjeira da Cunha; https://orcid.org/0000-0002-0396-5508; http://lattes.cnpq.br/5576851640501227; Siqueira, Renato do Nascimento; https://orcid.org/0000-0002-8397-8180; http://lattes.cnpq.br/9791817633014124
During oil production, shear and turbulence in the Ćow progressively break water droplets, leading to the formation of stable water-in-oil (W/O) emulsions. This study investigated the droplet breakup and coalescence dynamics in W/O emulsions through laboratory experiments and population balance modeling. The research was conducted using the NEMOG/UFESĆowcircuit, focusing on the impact of gate valve restrictions on the droplet size distribution (DSD). The Coulaloglou and Tavlarides (CT) and Mitre et al.(CEM) published models were applied to simulate the observed phenomena, with parameter adjustments to optimize predictions against experimental data. Results showed that the MV-01 valve, located at the circuitŠs inlet, predominantly induced droplet breakup, causing a moderate reduction in the mean droplet size. In contrast, the downstream MV-02 valve exhibited greater variability in DSD due to a signiĄcant increase in coalescence events, particularly at dispersed phase concentrations exceeding 15% v/v. The implemented models effectively predicted the DSD for water volume fractions of 5%, 10%, and 15% v/v. The CEM model demonstrated superior overall performance, even with its original parameters, although it underestimated coalescence effects at high dispersed-phase concentrations. With mean errors ψ of approximately 40% for MV-01 and 16% for MV-02 when considering the distribution. Predictions of the mean droplet diameter, De brouckere, yielded mean errors ψ below 23% for MV-01 and 9% for MV-02. The CT model showed limitations in fully describing coalescence phenomena, requiring additional adjustments under severe conditions. Factors such as water volume fractions and the heterogeneous distribution of turbulent energy were identiĄed as critical for improving predictions. Sensitivity analysis revealed that breakup and collision parameters (Cb and Cc) had the most significant inĆuence on prediction errors, whereas the coalescence efficiency parameter (Ce) had a negligible impact. Experimental results partially corroborated model predictions, with average and maximum errors comparable to those reported in the literature. The maximum error in the predicted volume-weighted mean droplet diameter (D[4,3]) was 25.6%, highlighting the need for advancements in submodels for coalescence and energy dissipation to enhance simulation accuracy.
Abordagem mista de volumes finitos e elementos finitos para otimização topológica em escoamentos turbulentos
(Universidade Federal do Espírito Santo, 2025-02-21) Lima, Caio Patrick Picoli de; Romero Saenz, Juan Sergio ; https://orcid.org/0000-0002-4469-3692; http://lattes.cnpq.br/5239907504083223; https://orcid.org/0009-0002-4851-1494; http://lattes.cnpq.br/3835630925303451; Martins, Ramon Silva ; https://orcid.org/0000-0002-4905-1453; http://lattes.cnpq.br/0642654456195324; Alves, Marcus Vinicius Canhoto ; https://orcid.org/0000-0003-0434-6159; http://lattes.cnpq.br/5750452284147903; Vazzoler Junior, Hermes ; https://orcid.org/0000-0001-7674-1356; http://lattes.cnpq.br/5304698296429834
Optimization is a well-known topic in popular imagination. Regarding engineering, geometry optimization is possibly the most widespread topic to the public, especially optimization of aircraft wings, and, as an example of this topic, there is the work of Muller (2021), that, through optimization, almost halved drag on the wing. Another interesting work was conducted by Zheng et al. (2021) in the optimization of the cooling system of a photovoltaic panel, in order to maximize its efficiency. Amongst all optimization methods, the one chosen for this work is the Topological Optimization Method, since it does not depend on a previous knowledge of the optimal geometry. Originally, this method was developed using the Finite Elements Method, which has limitations on flow solution. These limitations are overcome by using the Finite Volumes Method, although it has limitations that prevent its use on the Topological Optimization Method. The objective of this work is the development of the tool created by Lima, Aguiar e Romero (2024), which uses the Finite Volume Method and the Finite Element Method together for Topological Optimization, so that it optimizes turbulent flows. The solution of the flow was done using the software OpenFOAM®, the geometry optimization through custom code executed on Octave, and the automatization of this process was done by Bash Scripting. Once the optimization tests of a nozzle, a T bend, and a 90° knee had been conducted, qualitative analyses with the available literature were conducted. The results obtained were qualitatively identical to the reference geometries with smaller meshes, which shows that the tool is functional, although there is still space for improvement. Furthermore, the geometries resulting from the optimization of turbulent flows had a smaller pressure drop when compared to the geometries generated from the optimization of laminar f lows
Uma avaliação experimental da rota de repotenciação baseada em recuperação de calor residual para o condicionamento do ar de combustão em um motor alternativo de grande porte
(Universidade Federal do Espírito Santo, 2024-12-16) Fonseca, Francisco Mello; Donatelli, João Luiz Marcon; Cunha, Carla César Martins; Santos, José Joaquim Conceição Soares; https://orcid.org/0000-0003-3695-2014; Venturini, Osvaldo José; Pérez, Silvia Azucena Nebra de
Internal combustion engines (ICEs) in thermal power plants located in regions with high temperatures and humidity, as is the case for some plants in Brazil, operate under preventive derating to avoid the occurrence of knocking. On the other hand, these engines reject a significant amount of heat to the atmosphere, primarily through exhaust gases, which can be recovered to produce chilled water for cooling and dehumidifying intake air, aiming to increase power generation. A research and development project was conducted to design and install an experimental thermal system to evaluate performance improvements in a generating unit of a thermal power plant. This experimental thermal system was designed, its equipment acquired, installed, and instrumented for testing purposes. The system is composed of an absorption chiller, which recovers heat from the engine’s exhaust gases, a cooling coil for conditioning the engine’s intake air, and a cooling tower to cool the chiller and assist the engine radiator. The described experimental thermal system was installed and coupled to one of the generating units equipped with a Wärtsilä 20V34SG engine, which generates 8.5 MW of electric power, considering the derating conditions caused by the hot and humid climate at the plant site. Two experimental test campaigns were conducted. This dissertation aims to present and discuss the procedures and results of these tests, demonstrating that during the experiments, the maximum average cylinder pressure – one of the engine’s operational safety limits – was reached when the electric power output was 9.6 MW, representing nearly a 13% increase in power. The installed thermal system achieved a specific investment cost with savings of approximately 28% compared to recent investments in new generating sets, demonstrating the economic feasibility of the project.
Modelagem computacional da formação de torta de filtração em filtros de manga
(Universidade Federal do Espírito Santo, 2024-10-25) Zanete, Hóliver Zambon; Rocha, Sandra Mara Santana ; https://orcid.org/0000-0001-8787-7849; http://lattes.cnpq.br/9653853675618723; Siqueira, Renato do Nascimento ; https://orcid.org/; https://orcid.org/0000-0002-8397-8180; http://lattes.cnpq.br/9791817633014124; https://orcid.org/0009-0007-9184-6210; http://lattes.cnpq.br/3841315513918026; Sartim, Rafael ; https://orcid.org/0000-0002-5678-2027; http://lattes.cnpq.br/0380809249444032; Fernandes, Leandro Marochio ; https://orcid.org/0000-0003-4965-7233; http://lattes.cnpq.br/5933630468428555
The growing concern about the impacts of atmospheric pollution on the environment has driven the development of efficient technologies for controlling particulate emissions. Among these technologies, bag filters stand out as effective devices for removing particles from gas streams. These filters consist of a set of filter bags, usually made of fabric or felt, that retain solid particles while clean air passes through the filtering medium. As particles deposit on the surface of the filtering medium, they form a layer known as the filtration cake. This cake increases the resistance to airflow, leading to a higher pressure drop in the system. In this context, a detailed understanding of cake formation is essential for the design and optimization of bag filters. In this work, the implementation of a subroutine based on CFD (Computational Fluid Dynamics) was proposed to predict the formation of the filtration cake in bag filters. Darcy’s law was modified to incorporate particle deposition’s effects on the filter media’s surface on its permeability. The developed subroutine was validated against experimental data available in the literature and subsequently applied to a real bag filter. Three different superficial filtration velocities (5, 10, and 15 cm/s) were evaluated. Initially, the simulations were conducted under singlephase flow conditions (without particle injection), allowing for the fluid dynamics analysis at the beginning of the filtration process. Higher filtration velocities resulted in greater pressure drop. Additionally, the effect of the energy equation on the distribution of flow along the filter surface was observed. After the convergence of the single-phase simulations, particles with a diameter of 5,7 µm and a density of 2,79 g/cm3 were injected at a rate of 0,00127 kg/s for 250 seconds. The results indicated that the formation of the cake redistributed the airflow through the bags, promoting uniformity of the flow along the section of the filter element. It was found that the filling of the filtration chamber alters the pressure drop profile at the beginning of filtration and that, after the stabilization of the particle deposition rate, the increase in pressure drop begins to exhibit linear behavior. The identification of preferential zones for cake formation can significantly contribute to the optimization of bag filter designs

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