EE - Escola de Engenharia
URI permanente desta comunidadehttps://rihomolog.furg.br/handle/1/512
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47 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.
- ItemResin transfer molding process: a numerical analysis(2014) Oliveira, Iran Rodrigues de; Amico, Sandro Campos; Souza, Jeferson Avila; Lima, Antonio Gilson Barbosa deThis work aims to investigate the infiltration of a CaCO3 filled resin using experiments and the PAM-RTM software. A preform of glass fiber mat, with dimensions 320 x 150 x 3.6 mm, has been used for experiments conducted at room temperature, with injection pressure of 0.25bar. The resin contained 10 and 40% CaCO3 content with particle size 38μm. The numerical results were evaluated by direct comparison with experimental data. The flat flow-front profile of the rectilinear flow was reached approximately halfway the length of the mold. It was observed, that the speed of the filling decreases with increasing CaCO3 content and,the higher the amount of CaCO3 in the resin, the lower the permeability of the reinforcement that is found. The reduction in permeability is due to the presence of calcium carbonate particles between the fibers, hindering the resin flow in the fibrous media. The computational fluid flow analysis with the PAM-RTM proved to be an accurate tool study for the processing of composite materials.
- ItemNumerical analysis of the resin transfer molding process via PAM - RTM Software(2015) Oliveira, Iran Rodrigues de; Amico, Sandro Campos; Souza, Jeferson Avila; Lima, Antonio Gilson Barbosa deThis work aims to investigate the infiltration of a CaCO3 filled resin in fibrous porous media (resin transfer molding process) using the PAM-RTM software. A preform of glass fiber mat (fraction 30%), with dimensions 320 x 150 x 3.6 mm, has been used in rectilinear injection experiments conducted at room temperature and injection pressure 0.25, 0.50 and 0.75 bar. The polyester resin contain 0% and 40% CaCO3. The numerical results were evaluated by direct comparison with experimental data. The flat flow-front profile of the rectilinear flow was reached approximately half length of the mold. It was observed, that the both velocity infiltration and permeability have decreased with increasing the CaCO3 content, thus, increasing the time to processing of the composite material.
- ItemTemperature and pressure drop model for gaseous helium cooled superconducting DC cables(2013) Ordonez, Juan Carlos; Souza, Jeferson Avila; Shah, Darshit Rajiv; Vargas, Jose Viriato Coelho; Hovsapian, RobThe need to transfer large amounts of power in applications where cabling weight and space are a major issue has increased the interest in superconducting cables. Gaseous helium and neon are being considered as possible coolants due to their suitability for the expected operating temperature ranges. Gaseous helium is preferred due to its higher thermal conductivity and relatively lower cost than neon. This paper enhances a previously presented mathematical model of a superconducting cable contained in a flexible cryostat by including flow pressure drops. In this way, the model is capable of properly sizing and minimizing fan power, and allows the prediction of system response to localized heating events (e.g., quenching). A volume element model approach was used to develop a physics model, based on fundamental correlations, and principles of classical thermodynamics, mass and heat transfer, which resulted in a system of ordinary differential equations with time as the independent variable. The spatial dependence of the model is accounted for through the three-dimensional distribution of the volume elements in the computational domain. The model numerically obtains the temperature distribution under different environmental conditions. Pressure drop calculations are based on realistic correlations that account for the wavy nature of the coolant channels. Converged solutions were obtained within the imposed numerical accuracy even with coarse meshes.
- 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 volume element model (VEM) for energy systems engineering(2015) Dilay, Emerson; Vargas, Jose Viriato Coelho; Souza, Jeferson Avila; Ordonez, Juan Carlos; Yang, Sam; Mariano, André BellinThis work presents a simplified modeling and simulation approach for energy systems engineering that is capable of providing quick and accurate responses during system design. For that, the laws of conservation are combined with available empirical and theoretical correlations to quantify the diverse types of flows that cross the system and produce a simplified tridimensional mathematical model, namely a volume element model (VEM). The physical domain of interest is discretized in space, thus producing a system of algebraic and ODEs with respect to time, whose solution delivers the project variables spatial distribution and dynamic response. In order to illustrate the application of the VEM in energy systems engineering, three example problems are considered: (i) a regenerative heat exchanger; (ii) a power electronic building block (PEBB); and (iii) a notional all-electric ship. The same mathematical model was used to analyze problems (ii) and (iii), that is, the thermal management of heat-generating equipment packaging. In the examples, the converged mesh had a total of 20, 2000, and 7725 volume elements. The third problem led to the largest simulation, which for steady-state cases took between 5 and 10 min of computational time to reach convergence and for the ship dynamic response 50 min (i.e., 80,000 s of real time). The regenerative heat exchanger model demonstrated how VEM allowed for the coexistence of different phases (subsystems) within the same volume element. The thermal management model was adjusted and experimentally validated for the PEBB system, and it was possible to perform a parametric and dynamic analysis of the PEBB and of the notional all-electric ship. Therefore, because of the observed combination of accuracy and low computational time, it is expected that the model could be used as an efficient tool for design, control, and optimization in energy systems engineering.
- ItemNumerical simulation of FCC risers(2003) Souza, Jeferson Avila; Vargas, Jose Viriato Coelho; Meien, Oscar Felippe von; Martignoni, Waldir PedroThe catalytic cracking of hydrocarbons in a FCC riser is a very complex physical and chemical phenomenon, which combines a three-dimensional, three-phase fluid flow with a heterogeneous catalytic cracking kinetics. Several researchers have carried out the modeling of the problem in different ways. Depending on the main objective of the modeling it is possible to find in the literature very simple models while in other cases, when more accurate results are necessary, each equipment is normally treated separately and a set of differential and algebraic equations is written for the problem. The riser reactor is probably the most important equipment in a FCC plant. All cracking reactions and fuel formation occur during the short time (about 4-5s) that the gas oil stays in contact with the catalyst inside the riser. This work presents a simplified model to predict the, temperature and concentrations in a FCC riser reactor. A bi-dimensional fluid flow field combined with a 6 lumps kinetic model and two energy equations (catalyst and gas oil) are used to simulate the gas oil cracking process. Based on the velocity, temperature and concentration fields, it is intended, on a next step, to use the second law of thermodynamic to perform a thermodynamic optimization of the system.
- ItemThree-dimensional launch simulation and active cooling analysis of a single-shot electromagnetic railgun(2014) Zhao, Han; Souza, Jeferson Avila; Ordonez, Juan CarlosAn electromagnetic railgun is one of the applications of electromagnetic launchers, which are devices used to accelerate projectiles to velocities exceeding those attained with conventional propelling systems. A magnetic field is generated when current flows through two conductive rails connected by a moving armature. The current that passes through the rails exerts an electromagnetic force on the armature and causes it to accelerate to high speeds. In this work, a threedimensional transient model for the thermal and electromagnetic solutions of the launch process is presented. The model accounts for the determination of the current and temperature profiles inside the rails, the projectile movement, and the cooling process after the first launch. Focus is given to the thermal management where five different arrangements, one without cooling and four that include cooling channels, are studied. A 10 to 50 K reduction in the peak temperature was obtained with the inclusion of cooling channels when compared to the no-cooling-channel case. It was also shown that the position and size of these channels can be optimized in order to reduce this peak temperature.
- ItemStudies on thermal and viscoelastic properties of vinyl ester resin and its composites with glass fiber(2015) Garay, André Cechin; Paese, Lucas Tosin; Souza, Jeferson Avila; Amico, Sandro CamposVinyl ester resins are widely used in sandwich composite structures. Because of their good resistance to chemicals, flexibility and easy processing, these sandwich are extensively applied in the marine sector. These composites are typically manufactured by liquid molding processes, especially infusion. In this study, RTM light was used to inject the polymeric resin into the mold cavity, flowing in the space between the impermeable core and the mold walls, where the fibrous medium was. In this process, viscosity, gel time and curing time of the resin are very important parameters. This work addressed the curing and post-curing characteristics of a vinyl ester resin, and also the characteristics of neat and reinforced vinyl ester using dynamic mechanical analysis (DMA). The increase in shear rate did not significantly influence resin viscosity within the studied range. Differential scanning calorimetry showed the efficiency of the post-curing stage, with the decrease in residual enthalpy. With DMA, it was possible to determine gel time and gel temperature, which yielded similar values to those found by the SPI (Society of the Plastics Industry) method, indicating that the simpler SPI method can be reliably used for that.