EE - Trabalhos apresentados em eventos
URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/515
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11 resultados
Resultados da Pesquisa
- ItemVertical cooling arrangement for electromagnetic launchers(2011) Zhao, Han; Souza, Jeferson Avila; Ordonez, Juan CarlosA three-dimensional transient electromagnetic and thermal analysis has been performed on an electromagnetic launcher (EML) with a moving armature. Coupled electromagnetic, thermal, and mechanical equations are solved to capture current distributions, temperature response in the rails and projectile launch velocity. The thermal management of EMLs becomes more important in applications in which multiple shots are required. In this study we consider the first shot in a sequence of shots occurring every 5 seconds with the actual launch lasting only 3 milliseconds. This paper studies the effects of introducing a vertical cooling channels arrangement after the determination of the temperature field during the launch process. The temperature distributions at the end of the 5s cooling period are compared for three different channel configurations. A no-cooling situation is also included for comparison. These comparisons can provide some directions to optimize thermal management of the EML rail conductor.
- ItemApplication of the computational modeling in the resin transfer molding (RTM) process: a case study of a marine propeller(2012) Porto, Joseane da Silva; Letzow, Max; Santos, Elizaldo Domingues dos; Souza, Jeferson Avila; Isoldi, Liércio André; Amico, Sandro CamposThis work presents one example of how the computational modeling can help in the Resin Transfer Molding (RTM) process when it is applied to the production of parts with complex geometry, such as the marine propellers. This manufacture process of composite material parts consists in the injection of a polymeric resin into a closed mold where a fibrous reinforcement is previously placed. The numerical simulation of the RTM process can be considered as the resin flow through a porous media. This computational model was developed in the FLUENT package, which is based on the Finite Volume Method (FVM), and was applied to study a propeller for naval propulsion. As the propeller has a complex format, the use of computational approach as a preliminar step in the manufacturing process is very important for the correct definition of the inlet and outlet nozzles. So, it is possible to design an efficient mold, avoinding extras costs related with the mold redesign, the resin waste and the increase of injection time. The results showed that an inadequate positioning of the mold outlet nozzles causes an increase about 10% and 2% in the production time and in the resin amount, respectively, for obtaining the marine propeller by RTM process.
- ItemA numerical methodology for permeability determination of reinforcements for polymeric composites(2012) Souza, Jeferson Avila; Isoldi, Liércio André; Santos, Elizaldo Domingues dos; Oliveira, Cristiano Peres; Amico, Sandro CamposThis work focus on developing a numerical methodology for the determination of permeability of RTM reinforcements. The method allows the calculation of the three permeability components (Kxx, Kyy and Kzz) from a set of time dependent flow front coordinates data; one coordinate for each permeability component. An initial guess is set for the permeabilities and the difference between numerical and experimental values of flow front position at a specific time is minimized with the solution of an algebraic system of equations. Newton-Raphson method was used to solve the non-linear system of equations. The results presented in this paper were obtained for a rectilinear (1D) and a radial 2D problem, both with analytical solutions for the flow front position as a function of time. For the 1D comparison between the numerically calculated Kxx and the analytical value agreed within 1.7% and, for the 2D radial problem, numerical and analytical values of Kxx and Kyy agreed within 1.3%.
- ItemA two-phase one-dimensional model for simulation of FCC risers(2006) Brum, Ary Saad; Souza, Jeferson Avila; Vargas, Jose Viriato CoelhoThe FCC (Fluidized Catalytic Cracking) is one of the most important processes in a petroleum refinery plant. The numerical modeling of this process has been performed by several authors who have proposed different mathematical models and reported them in the literature. With the constant increase of computational capabilities, such models have become even more complex and with wider application. The different models address both fluid flow and cracking kinetic, varying from simple one phase and one-dimensional models to three-dimensional and three-phase models. Therefore, there is no common ground regarding the most adequate formulation, and advantages and drawbacks may be identified in each available model. In the present work, a relatively complex model reported in the literature is reproduced. Even though it is a one dimensional model, it includes many physical phenomena, like the dependence of the fluid properties on temperature and the transport equations formulation for both phases (gas and particulate). In a following stage, some simplifications in the mathematical formulation are included to the model and the results obtained with both formulations (with and without simplifications) are compared. The main goal of the present work is to establish a relationship between each included physical phenomenon and its real influence on the capability of the model to predict the products formation inside the riser reactor.
- ItemNumerical simulation of the resin transport through fiber reinforcement medium(SOUZA, Jeferson Avila; ROCHA, Luiz Alberto Oliveira; AMICO, Sandro Campos. Numerical simulation of the resin transport through fiber reinforcement medium. In: INTERNATIONAL CONGRESS OF MECHANICAL ENGINEERING – COBEM, 19., 2007, Brasília. Anais... Brasília: [s.n.], 2007. Disponível em: . Acesso em: 25 jul. 2015., 2007) Souza, Jeferson Avila; Rocha, Luiz Alberto Oliveira; Amico, Sandro CamposThis paper describes the numerical simulation of the RTM (Resin Transfer Molding) process applied to the modeling of the resin transport through a fibrous reinforcement. The molding volume which is to be impregnated with the resin is considered as a porous medium and the Darcy equation is used to determine the resin transport velocity through the mold. A control volume finite element method is used for the determination of the pressure gradients inside the mold and the resin flow front advance is obtained using a FAN technique. The finite volume method was built to be used with a bi-dimensional unstructured grid, hence allowing the discretization of complex geometries. In the simulation presented here, resin physical properties, like viscosity and density, and the permeability of the media were kept constants.
- ItemAn original procedure to determine transverse permeability using a multilayer reinforcement in RTM(2010) Oliveira, Cristiano Peres; Souza, Jeferson Avila; Isoldi, Liércio André; Rocha, Luiz Alberto Oliveira; Amico, Sandro Campos; Silva, Rafael Diego Sonaglio daResin Transfer Molding (RTM) is a manufacturing process for polymer composites parts for a variety of uses. The numerical simulation of the resin flow into the mold can be used to minimize costs related to mold design and the manufacturing process itself. However, to obtain realistic results, accurate information about the resin and the reinforcement media are necessary. In the multilayer RTM, distinct porous media layers are stacked to obtain a final composite with better performance. For the numerical simulation of the multilayer RTM, transverse permeability (Kzz) data are necessary. This work proposes an original methodology to determine the transverse permeability in multilayer RTM composites, assuming that the in-plane permeabilities (Kxx and Kyy) are known and using this information, combined with experimental data obtained during mold filling. The motivation of this study is the fact that the transverse permeability is usually not available in the literature, being referred to as a difficult parameter to be directly determined using experiments.
- ItemComputational modeling of the resin transfer molding process(2009) Oliveira, Cristiano Peres; Souza, Jeferson Avila; Isoldi, Liércio André; Rocha, Luiz Alberto de Oliveira; Amico, Sandro CamposThe Resin Transfer Molding, or RTM, process has recently become one of the most important processes of fiber reinforced composites manufacturing. The process consists essentially of three stages: “an arrangement of fiber mats in a mold cavity, a mold filling by a polymeric resin and a curing phase”. Most of the difficulties of incorporating RTM occur during the filling stage. To create an acceptable composite part the preform must be completely impregnated with resin. The conditions which most strongly influence the flow are mold geometry, resin rheology, preform permeability, and location of the injection ports and vents. There are different types of RTM process, e.g. RTM Light or VARTM, employed in accordance with the final desired characteristics and properties of composite components. Besides, RTM may also be carried out using multilayers, with distinct characteristics. The numerical simulation of the mold filling stage becomes an important tool which helps the mold designer to understand the process parameters. Considering the fibrous preform as a porous media, the phenomenon can be modeled by Darcy’s law to describe resin flow. This study used two commercial softwares, FLUENT® and PAM-RTM®. FLUENT® is a general Computational Fluid Dynamics (CFD) code, based on Finite Volume Method (FVM). It applies the Volume of Fluid (VOF) method to solve the filling problem because it does not have a specific RTM module. PAM-RTM® is a specific package for RTM problems, based on the Finite Element Method (FEM). These tools were applied to simulate numerically several RTM examples of the resin flow into the mold and the results for both softwares were compared with previous works.
- ItemConstructal design applied to the light resin transfer molding (LRTM) manufacturing process(2013) Isoldi, Liércio André; Souza, Jeferson Avila; Santos, Elizaldo Domingues dos; Marchesini, Renato; Porto, Joseane da Silva; Letzow, Max; Rocha, Luiz Alberto de Oliveira; Amico, Sandro CamposThe Light Resin Transfer Molding (LRTM) is a manufacturing process where a closed mold pre-loaded with a porous fibrous preform is filled by a liquid resin injected through an empty channel (without porous medium) which runs all around the perimeter of the mold, producing polymeric composite parts. Using the capability of FLUENT® package to simulate a multiphase flow (resin and air) in a geometry composed by porous media regions and empty regions, a computational model based on the Finite Volume Method (FVM) was applied to reproduce the resin flow behavior during the LRTM process. The aim of this work was to define the optimal geometry for the empty channel (border) by means the Constructal Design method. To do so, considering a border with a rectangular cross sectional area, the degree of freedom wb/tb (ratio between the width and thickness of the border) can vary while the border volume is kept constant. The results showed that employing the Constructal Design it is possible to decrease the filling time of the LRTM process in almost 20 %, being this an unpublished use for the Constructal Theory.
- ItemNumerical simulation of an owc devise(2013) Souza, Jeferson Avila; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréWave energy is a renewable and clean energy resource that, in a near future, may become an alternative to the more pollutant fuels. There are a number of wave energy converters prototypes and a few installed text facilities, however there is no device ready for commercial utilization. In this work an Oscillation Water Column Generator (OWC) is numerical simulated using the OpenFOAM software. The VOF (volume of fluid) method is used to solve the multiphase (air + water) fluid flow problem. Regular gravity waves, inside a rectangular (2D) tank, are imposed numerically by prescribing the inlet velocity at the left wall of the tank. The main goal of the work is to simulate the interaction between the generated waves and the OWC device and calculate the energy generated by the turbine (usually a Wells turbine). The air turbine, responsible for the electrical energy generation, is simulated by applying a source (force) term to the momentum equation at the OWC chimney section. Pressure drop at the turbine and air velocity at the chimney outlet section are evaluated as a function of time and used to compute the available energy to be converted into electrical energy. Results are presented and compared for two operating condition: with turbine and without turbine.
- ItemComputational modeling of the air-flow in an oscillating water column system(2009) Gomes, Mateus das Neves; Olinto, Cláudio Rodrigues; Isoldi, Liércio André; Souza, Jeferson Avila; Rocha, Luiz Alberto de OliveiraSeveral alternatives for electric power production have been studied in the last decades. Because of the huge energetic resources stored in the oceans in the form of wave - about 2TW - value that is compared to the annual rate of electric power used in the earth, the conversion of the wave’s energy of the oceans in electric power comes up important as one of these alternatives. One of the ways to make that conversion is through the oscillating water column (OWC) system: the wave enters into the hydro-pneumatic chamber (resembling a cave with entry below the waterline) and the up-and-down movement of water column inside the chamber makes air flow to and from the atmosphere, driving an air turbine. The turbine is symmetric and is driven indifferently in which direction the air flows. This paper presents the computational modeling of the air flow in a oscillating water column chamber using two different methodologies: in one of them it is considered just the chamber, varying the velocity in its entrance according to the wave’s equation, considering just the air, and a new one considering the chamber put into a wave’s tank, so it takes in account the complete interaction between water and air into the chamber. In this method, to consider the water and air it is used the multiphase model volume of fluid (VOF). It was simulated the same geometric compound of an oscillating water column system with a vertically placed tower, in order to compare these two different numerical models. It is noted that the dimensions of the tested chamber are in laboratory scale and the proposed model was used to simulate a 2D case. It was used GAMBIT® software for geometry creation and mesh generation, while FLUENT® package was employed for solving the conservation equations and analysis of the results.