Programa de Pós-Graduação em Engenharia Mecânica - PPGEM /ITEC

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/2341

O Programa de Pós-Graduação em Engenharia Mecânica (PPGEM) do Instituto de Tecnologia (ITEC) da Universidade Federal do Pará(UFPA). Tem por objetivo formar recursos humanos qualificados, e incentivar a pesquisa e o aprofundamento dos estudos técnicos e científicos relacionados ao campo de atuação da Engenharia Mecânica com aplicação na realidade e necessidades da região amazônica.

Navegar

Agora exibindo 1 - 20 de 55

Acesso aberto (Open Access)
Construção de um modelo de dispersão de poluentes na Baía do Guajará
(Universidade Federal do Pará, 2005-12-19) BATISTA, Adriano Gomes; SENA, Manoel José dos Santos; http://lattes.cnpq.br/2349287816857909; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
The sea and coastal environment of Brazil have suffered a process of considerable environmental degradation in the last years. This degradation was caused by the growing environmental pressure on the sea and the continental natural resources that have overwhelmed the limited capacity of the ecosystems to absorb the impacts. In the specific case of the Bay of Guajará, located in the Estuaries Guajará, in the area delimited by the Bay of Marajó and for the rivers Pará and Guamá, these risks are associated mainly to the pollution originating from of the city of Belém and the petroleum derived pollution caused by transport operations. In the case of the Bay of Guajará, it is known that there are sewer spillings periodically caused by the tide. Because this pollution is caused by the tide, there is little that can be done to correct or soften the effects of this problem. The numeric models consider the complexity of the physical phenomena that govern the operation of the coastal environment, and have been used as tools in hydrodynamic simulation with recognized importance in coastal administration. This application can support several studies: the understanding of the dispersing processes of pollutants; the implantation of systems of monitoring of water quality; the plan of action in cases of a oil spillage; and the effects of alterations in the geometry of channels and bays and estuaries. The objective of this work is to explain these subjects and to describe the necessary stages for the construction of a numeric model of dispersion in the Bay of Guajará using the tools of the Systems of Geographical Information and the Method of Finite Elements.
Acesso aberto (Open Access)
Análise experimental sobre velocidade de captura em sistemas de transporte pneumático
(Universidade Federal do Pará, 2006) GOMES, Luiz Moreira; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
The transport velocity is one of the most important parameters in the pneumatic transport of solids. The success of the particulates materials conveying depends on the prediction or the determination of the minimum velocity of transport. The velocity above of that necessary to the steady transport of solid particles leads to a great energy consumption due to an increased pressure drop of the system, solids degradation and abrasion of solids and of the tube. On the other hand, a velocity below of this boundary-value certainly will result on the deposition of solid particles for bottom of the tube and its consequently blockage. In this work, a technique to measure the minimum pickup velocity of solid particles in horizontal pneumatic conveying has been developed. It is based on visual observation of the particles behavior when occurring the capture, on measures of the velocity of operation of the gas and the mass of captured particles. The qualitative analysis of some parameters is made still that influence in the pickup velocity of particles, allowing a bigger understanding of the involved phenomena.
Acesso aberto (Open Access)
Estudo de técnicas de análise modal operacional em sistemas sujeitos a excitações aleatórias com a presença de componente harmônico
(Universidade Federal do Pará, 2006-02-17) CRUZ, Sérgio Luiz Matos da; MESQUITA, Alexandre Luiz Amarante; http://lattes.cnpq.br/3605920981600245
Traditional modal parameter identification usually require measurements of both the input force and the resulting response in laboratory conditions. However, when modal properties are to be identified from large structures in operation, usually the possibilities to control and measure the loading on the structure is rather limited. In this case, the modal testing is usually performed using response data only. Operational Modal Analysis (OMA) or Operational Modal Testing is a method where no artificial excitation needs to be applied to the structure or force signals to be measured. In this case, the modal parameters estimation is based upon the response signals, thereby minimizing the work of preparation for the test. However, standard OMA techniques, such as NExT, are limited to the case when excitation to the system is a white stationary noise. The NexT assumes that the correlation functions are similar to the impulse response functions, and then, traditional time domain identification methods can be applied. However, if harmonic components are present in addition to the white noise, these components can be misunderstood as natural modes in the plot of response spectrum. In this work, it is shown that it is possible identify if a peak in the response spectrum correspond to a natural mode or an operational mode. It is achieved through the application of the probability density function. It is also presented a modification in the LSCE algorithm in such manner that it can support harmonics in the operational excitation. In order to validate the methods presented in this work, it is shown numerical and experimental cases. In the former, results for a mass-spring-damper of five degree of freedom are presented, and in the latter a beam supporting an unbalanced motor is analyzed.
Acesso aberto (Open Access)
Controle de vibração em reatores elétricos através de absorvedores dinâmicos viscoelásticos
(Universidade Federal do Pará, 2006-04-18) VALE, Alan Rafael Menezes do; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
Equipments used in electric substations have specific functions in the functioning and maintenance of the functionality of such installations, being equipment applied to control reactive currents, short circuit currents and maneuver poles in transmission systems of electric energy. It was detected that some reactors in functioning had presented high levels of structural vibration. Two of these reactors operate in the substation of Rurópolis city, situated the west of Pará state. Another decurrent problem of the raised level of vibration of these structures is the generation of hot spots in the electromagnetic nucleus of the reactor, being able to generate bubbles of highly inflammable gases. The existence of these operational problems can cause to the North of Brazil Transmission System functional interruptions in the transmission of electric energy. That would cause in the North region and other linked ones (Northeast, Southeastern and Center-West) raised social and financial damages. The application of tools for reducing the vibrate-acoustic trouble (reduction of the levels vibration and, therefore, noise) can prevent structural and operational damages that result in its operative non-availability reducing, consequently, losses and the necessity of the development of equipment of cost raised with low indices of vibration. In the intention of if reducing such levels, it is considered the application of dynamic absorbers in the external structure of the reactors. With the calculated absorbers in amount, position and parameters (mass, stiffness and damping) expects to create a system syntonized with the frequency of the excitement of electromagnetic nature, that will absorb part of the vibratory energy of the reactor, having minimized raised detected levels and, therefore, all the subsequent problems. Viscoelastic materials will be used in the dynamic absorbers (with temperature and frequency dependent dynamic properties), because these materials to increase the field of activity of the dynamic absorbers, adjusting themselves it the raised verified modal density in the metallic shells of the reactor.
Acesso aberto (Open Access)
Comportamento mecânico e de flamabilidade de compósito de polipropileno reclicado com fibra de coco e hidróxido de alumínio
(Universidade Federal do Pará, 2006-05-02) SILVA, Vera Lúcia Dias da; DIAS, Carmen Gilda Barroso Tavares; http://lattes.cnpq.br/2113791118142177
The plastic recycling has been an interesting possibility to minimize the destiny problem of the plastic residues. The polypropylene (PP) is enters the types polymers of larger consumption, therefore the utilization of this material has been enabling the studies development of great scientific and social relevance. This polymer presents excellent cost-performance relation, besides can be easily conformed and to exibit mechanical properties that turns it useful in several applications. However, this material when being burnt generates products that act as combustible so that, for some uses, flame resistance good is necessary. This can be gotten by flame retardant addition, that has the intention to increase the resistance of this material to the ignition and, at the same time reducing the propagation speed of the flame. The aluminium hydroxide, or simply alumina hydrate, is the flame retardant agent used most in the market, therefore it also acts as smoke suppressant and it does not liberate toxic gases during the burning. However, for such properties, high alumina hydrate concentrations are necessary. This causes deterioration in the physical properties of the materials for not have reinforcing character. The natural fibres own good reinforcement capacity when combined adequately with polymers. Also presenting advantages as low cost, low density, biodegradability and in the combustion does not emanate toxic gases. In this work, mixtures contend alumina hydrate and coco fibres had been incorporated polypropylene with the objective of if finding an properties rocking adequate for use of this composite with characteristics flame resistance and mechanical performance. The composites were molded by hot compression and characterized by IV, DRX, MEV, mechanical and non-flammability tests. Increase in the elasticity modulus of the composites in general was observed, as well as increase in the tenacity resistance of the PP/coco fiber composite regarding pure PP. The results had indicated the efficiency of alumina hydrate as it flame retardant, in all the composites, except PP/F, classifying the materials as V-0 according to international norm UL 94V.
Acesso aberto (Open Access)
Projeto e construção de câmaras reverberantes em escala reduzida para o estudo das características de perda de transmissão de divisórias confeccionadas a partir de materiais regionais
(Universidade Federal do Pará, 2006-09-05) TOUTONGE, José de Aviz; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
To project and build reverberant chambers, in scaled model, for the determination of materials transmission loss used for noise control purposes was the objective of this research. Besides, the research seeks to establish a methodology of analysis and interpretation of the acoustic parameters starting from the theory of scaled models, in such way that one can infer the transmission loss of the studied materials. The necessity of this construction occurs due to the non availability of real scale reverberant chambers (only available in some regions of Brazil), making it difficult and raising the costs of material performance tests in other Brazilian regions. Therefore, reverberant chambers were constructed in a reduced scale of 1:6, in order to allow the transmission loss study of party walls, developed with regional materials, confronting their performances and, simultaneously, their use in academic activities. Despite the fact of the chambers have been constructed in reduced scale, the scale factor (1:6) was not considered, meaning that measurements had been carried through in the real octave bands between 125 Hz and 8 kHz. Party walls had been assayed for the determination of the acoustic parameters, based on ISO 140 and 354. Finally, from experimental results, it was possible to prove the efficiency of materials used in the construction of partitions, which could be used for noise isolation purposes in buildings and industrial enclosures. Apart from the experimental assays, analytical calculations had been fulfilled according to the formulation of Analysis Energy Statistics (SEA) in order to provide evidence and validation of the results.
Acesso aberto (Open Access)
Simulação de sistemas de simples estágios de refrigeração por compressão de vapor
(Universidade Federal do Pará, 2006-09-18) ZIGMANTAS, Paulo Vitor de Matos; LIMA, Carlos Umberto da Silva; http://lattes.cnpq.br/3180435250091076
Nowadays, the thermal performance of refrigeration systems of vapor compression is a very important toll to aid on the development of News Products or Upgrading them. A steady state simulation model is presented to estimate the refrigeration systems performance.The studied system considers a air conditioning equipment Model PA HILTON, that includes a semi-hermetic alternative compressor, a compact tube and fins evaporator and condenser and finally a thermostatic expansion valve. The condenser mathematical model takes account of three different regions of heat transfer : cooling, condensing and sub-cooling.The evaporator mathematical modeling considers the evaporating and superheated regions. Depending of the region studied, in the model simulated includes appropriate correlations of heat transfer and pressure droops. The heat transfer and pressure drop inside the lines between the components are not considered. The solution of non linear equation systems is obtained trough a interactive method using the Engineering Equation Solver Software. The comparations between experimental and simulated values shows a very good agreement.
Acesso aberto (Open Access)
Implantação de CGH's na Amazônia: uma visão global com ênfase nos aspectos hidrológicos, tecnológicos, ambientais e financeiros
(Universidade Federal do Pará, 2007) BEZERRA, Fábio Vinícius Vieira; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662; BLANCO, Claudio José Cavalcante; http://lattes.cnpq.br/8319326553139808
A problem of great social relevance in the Amazon Region is the fact that small isolated communities are not contemplated by the benefits of the big hydroelectric plants installed in the region. An alternative solution to this problem is the use of the big mesh of small rivers and creeks of the area to the implantation of small hydroelectric power plants known in Brazil as CGH´s. Within this context, the present work analyzes and discusses certain general aspects concerning the implantation of CGH's, and mainly, bringing them to the reality of the small Amazon basins. The aspects to be approached in this work are concerned with the technological, hydrological, environmental, and financial contexts. These aspects are analysed in a global form and also in a specific way through a case study - the implantation of sister’s Dorothy CGH, in which was possible the use of existent methodologies for the studies of implanting CGH's in the Amazon Region. Within the hydrological aspects it was possible the use of existent rain-flow model developed by Blanco 2005, and applied to small basins in the Amazon Region which do not possess flow registrations. In the environmental context nowadays there is a strong requirement of the local authorities for the accomplishment of environmental studies relative to the energy enterprise. Taking into consideration that the Amazon region is environmentally very affected by man's action, these studies should be very well defined, in order to point out the possible impacts that can be caused by CGH, which must be described in the RAS (Simplified Environmental Report), requested by the competent organ responsible for regulating small energy uses. In view of that, it was developed in this work a methodology to simulate and calculate the flooded area by the CGH’s implantation in the Amazon Region, and a case study concerning the implantation of sister Dorothy’s CGH is presented. In the technological context, due to the main characteristics of low falls of the Amazonian rivers and creeks, the focus of the technological analysis will be on the behavior of axial turbine adapted to low falls. The technological analysis contemplates the use of tools for predicting the performance of axial turbines. In the financial context , there is rare information regarding the costs of implantation of CGH's in the Amazon. The costs regarding the sister’s Dorothy CGH were obtained and compared with other equivalent CGH’s and diesel generators available in the literature.
Acesso aberto (Open Access)
Caracterização da liga 6101 refinada com a adição de diferentes teores de cobre e solidificadas em molde unidirecional horizontal e em molde "U"
(Universidade Federal do Pará, 2007) FEITOSA, Johnyson Pereira; QUARESMA, José Maria do Vale; http://lattes.cnpq.br/7443111804471290
The 6101 alloy (series 6xxx) was modified with addition of 0.05% and 0.3% of copper and with additions of grain refiners as Al-Ti-B. The alloys were thermally characterized (heat transfer coefficient of metal / mold, displacement speed of liquidus isothermal and cooling rate), mechanically (tensile strength and toughness module) and electrically (electric resistivity, specific resistance and power conductivity) using two forms of pouring out: one is horizontal directional solidification and the other into the "U" mold. By horizontal directional solidification was possible characterize the macrostructure, influenced by refiners of grain and by viscosity that copper provides in the metal / mold efficiency of alloys researched, modifying the thermal, mechanical and electrical properties. The solidification in "U" mold makes possible evaluates the mechanical and electrical properties, seeing the forming process variables of alloys, as forming rate, tensile strength, toughness and electric resistivity, power conductivity and electric resistance, using the specimens obtained in several diameters. For the “U” mold were casting more two alloys to evaluation, Al-0,6Mg-0,4Si-0,1Cu and Al-0,6Mg-0,4Si-0,2Cu. The mechanical and electrical properties had been influenced by cold working, copper content and shrinkage void presents into alloys structures.
Acesso aberto (Open Access)
Projeto, construção e aferição de um dispositivo de solidificação unidirecional horizontal refrigerado à água
(Universidade Federal do Pará, 2007-04-16) SILVA, José Nazareno Santos da; ROCHA, Otávio Fernandes Lima da; http://lattes.cnpq.br/0702326922309672; MOREIRA, Antonio Luciano Seabra; http://lattes.cnpq.br/0667768010106721
The aim is about the solidification structures of thermal parameters is important to mechanic behaviour of the metallic materials. These structures are influenced by means of heat removal conditions of metal/ mould system during the solidification process. Despite of this, some mathematic models have been developed to appraise the structural and thermal variation mainly considering the upright unidirectional solidification process. This research plans to project, construct and check up one device in order to be able to represent the horizontal unidirectional solidification process cooled by water which considers the solute convection effects. To check up the solidification device, a comparative study was done between the representative experimental bend of metal´s thickness solidification related to time to Al-4%Cu, Sn-5%Pb, Sn-15%Pb e Sn-20%Pb alloys. The present results shows positive consonances. The unidirectional aspect of the heat removal constructed was estimate trough the macrostructure characterization of the studied alloys. Finally a comparative study is done between values of the interface metal/mold heat transfer coefficient obtained trough other newly works developed about ascendant and descendent unidirectional solidification process.
Acesso aberto (Open Access)
Projeto e construção de uma câmara reverberante em escala reduzida para a caracterização acústica de materiais absorventes
(Universidade Federal do Pará, 2007-05-31) GUEDES, Reginaldo Cascaes; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
In the area of Acoustics, concerning the last decades, a significant growth has been observed in the demand for data regarding not only the absorbing characteristics of acoustical materials, but also the usage of numerical methods which are able to represent the acoustical behavior of real systems. These real systems demand a significant infrastructure, which means a great deal of investments. Thus, in order to attend such demands for new data, to allow the development of research regarding the sound absorbing characteristics of regional materials and to develop practical classes on acoustics, both for graduate and post-graduate students, this work presents all the information regarding the project and construction of a scaled reverberant chamber (1:6 of a 200 m3 real chamber). Besides, a methodology is presented regarding the qualification and adequacy of the internal acoustic field, based on the guidance of ISO-354. On the other hand, experimental results for the miniaturized chamber are presented and discussed, which characterize and validate the usage of the coconut fiber panels, developed by the Acoustics and Vibration Group of the Federal University of Pará. Finally, numerical results, based on Ray Tracing Methods, are presented and compared to those measured for the scaled chamber, seeking the validation of the developed numerical model.
Acesso aberto (Open Access)
Influência dos parâmetros térmicos de solidificação na transição colunar/equiaxial em ligas do sistema Sn-Pb sob condições transitórias de extração de calor
(Universidade Federal do Pará, 2007-07-04) MOUTINHO, Daniel Joaquim da Conceição; ROCHA, Otávio Fernandes Lima da; http://lattes.cnpq.br/0702326922309672; MOREIRA, Antonio Luciano Seabra; http://lattes.cnpq.br/0667768010106721
This work carry out a theoretical experimental study about the influence of solidification thermal parameters on the columnar to equiaxed transition of Sn 5%Pb, Sn 15%Pb, and Sn 20% Pb and Sn 25% Pb alloys during the horizontal unidirectional solidification process cooled by water which considers the solute convection effects. The tip growth rates and cooling rates have been experimentally calculated and the obtained results are compared with those of a numerical model. The columnar to equiaxed transition position is determined through the macrostructure characterization of the studied alloys. The experimental results have shown that the thermosolutal convection influences the CET occurrence. Finally, a comparative experimental study is done for the studied alloys when directionally solidified in different water-cooled systems.
Acesso aberto (Open Access)
Predição do desempenho de gasificadores de biomassa utilizando equilíbrio químico
(Universidade Federal do Pará, 2007-08-10) OLIVEIRA, Antônio Geraldo de Paula; NOGUEIRA, Manoel Fernandes Martins; http://lattes.cnpq.br/2324813094737469
The gasification technology has been object of study of many researchers, especially those involved in power generation use biomass. This paper presents a simplified model for biomass gasification based on chemical equilibrium considerations. The model consists in the minimization of the Gibbs free energy of the produced gas, constrained by mass and energy balances for the system. Despite the simplicity of the model, its results are reliable in identifying the tendencies of the working parameters for the system. Biomass composition, gasification temperature (air supplied), moisture content, air temperature, and heat losses are parameters that may be varied in order to evaluate different operational points. Results obtained are compared to those found in real operation of gasification processes and they shown good agreement.
Acesso aberto (Open Access)
Estudo da viabilidade operacional do processo de soldagem MAG com alimentação adicional de arame frio
(Universidade Federal do Pará, 2007-11-09) SÁBIO, Alberto Dias; BRAGA, Eduardo de Magalhães; http://lattes.cnpq.br/4783553888547500
The present study shows experimental research of the weld concerning operational, economic and geometric viability as well as its superficial quality when using MAGCW (Metal Active Gas – Cold Wire), understood as: MAG welding process with nonenergized wire or cold wire. For the development of this research, welding MAG and MAG-CW processes have been used together with 1,2 mm of diameter consumable solid wires, class AWS E-70S6 and carbon dioxide pure, CO2, as protection gas with 17 l/min release for both processes. Automated welding was performed with electronic source adjusted in CC+, in constant tension mode, interfaced by a microcomputer. In both processes the welds were put on steel carbon samples SAE 1020, 76x155x12,7 mm size, with simple disposition passes, pulling and pushing the voltage arc. The MAG-CW process added cold wire on the electric arc region, fed by the Tandem and Twin sequential wire shape auxiliary system on plane position. The variables of influence were: Velocidade de Alimentação do Arame-Eletrodo, VAE, which varied in three levels: 6; 7,5 and 9 m/min, respectively, Velocidade de Alimentação do Arame-Fio, VAF, which also varied in three levels: 3; 4 and 5 m/min combined with VAE. Response variables for experimental evaluation were electric arc stability, economic features, geometric features and weld superficial quality. The results demonstrated satisfactory arc stability as well as high production concerning MAG process and also good superficial aspect of welds. Rising rates obtained by MAG-CW process demonstrates the superiority due to non-energized wire addition to the arc. Thus, the MAG-CW process, in comparison with MAG process, demonstrated superiority concerning the 57% in rate of fusion (RF) for the VAE of 6 m/min, 59 % for the VAE of 7,5 m/min and 53 % for the VAE in 9 m/min. it has also been observed that the same occurred with the rate of deposition (RD) increasing in all speed levels: 62% for the VAE in both conditions of 6 m/min and 7,5 m/min and in 57 % for the VAE in 9 m/min. The good performance in the increase of the taxes obtained by the process MAG-CW demonstrates advantage, with larger evidence in the acting of these characteristics, in function of the addition of cold wire to the arch.
Acesso aberto (Open Access)
Análise técnico-econômica da substituição parcial do combustível diesel pelo gás natural em motores marítimos na região amazônica
(Universidade Federal do Pará, 2007-12-07) FRANCO, Alcides Canêjo Linhares; MESQUITA, André Luiz Amarante; http://lattes.cnpq.br/1331279630816662
The international experience indicates the existence of five main elements related to the expansion of the natural gas consumption as following: a) availability of natural gas reserve; b) restriction offers of other energy ones (especially for the electricity generation); c) concern with the environment by a environmental legislation more rigorous, each day; d) the investments attraction by the private companies permission for the distribution and commercialization of the natural gas; e) the generalized permission for the industry, attracting private companies, because of the opportunity of the investment. In this scene, the construction of the gas line Coari (extraction base) Urucu-Manaus with about 670 kilometers of total extension that will be ready on April of 2008, as divulged by Petrobras on 05/21/2007 and will carry 4.7 million cubic meters per day of natural gas in the first phase of operation. The foreseen total investment is of R$2.4 billions. The natural gas will substitute the diesel and the combustible oil used, mainly, in the production of great part of the consumed electric energy in the Amazon State. It will be used also in the industrial and commercial processes, as well as supplying, with safety, auto-machine vehicles (automobiles, pickups, light trucks, bus). This last application stimulated this research, that establish a technical-economic analysis of the partial substitution of the fuel diesel by the natural gas in maritime engines in the Amazon Region, because the boats are vehicles that cross the rivers of this Region and are used for load and passengers transportation. First, it is demonstrated that it is possible, in technical conditions, the conversion of the diesel engines to consume the diesel mixed with natural gas to the taxes of substitution of diesel for natural gas from 5% to 90%, using available technologies that are in the Brazilian market, under the view of energy and environment performances. Later it presents an economic analysis of the conversion, considering the reservoirs for natural gas compressed - NGC offered in the national market and the kits of conversion. The research reveals: a) the economic viability of the enterprise if the weights and the volumes of the natural gas reservoirs are neglected, especially the first one; b) the no economic viability, considering the transport of the reservoirs, in the boats, that had no financial results because of the prices of the taxes resulting of the space occupied by the volumes and the weights of these reservoirs.
Acesso aberto (Open Access)
Influência da variação da razão de alimentação ar/serragem de um combustor ciclônico na composição dos seus produtos gasosos
(Universidade Federal do Pará, 2008) VASCONCELOS, Adriano Akel; NOGUEIRA, Manoel Fernandes Martins; http://lattes.cnpq.br/2324813094737469
In this work it was made an analysis of the combustion in a cyclonic combustor through experimental measures of the temperature and gases concentration in the internal wall of the combustion chamber. With the objective of finding an appropriate operational parameters for the proposed design, the feeding of air and sawdust of combustor was varied in a poor equivalence ratio (with excess of air) while the experimental data were computed. The data profiles obtained were confronted with the theory of the combustion of solids and with the temperature fields and gases concentration founded by Cunha (2005) numerically in the code Fluent V.6.0. In this comparison it was possible to find good qualitative value among the temperatures measured and the one from calculations, however there were differences in the topic concentration of gases. It was possible also to identify the minimum equivalence rate that the cyclonic combustor had in their gaseous products low pollutant tenors, like CO. Besides, at the end of this work a methodology was proposed to find the appropriate size of a cyclonic combustor in agreement with the strip of sawdust consumption that it wants to incinerate.
Acesso aberto (Open Access)
Comportamento mecânico de material compósito de matriz poliéster reforçado por sistema híbrido fibras naturais e resíduos da indústria madeireira
(Universidade Federal do Pará, 2008-02-29) RODRIGUES, Jean da Silva; FUJIYAMA, Roberto Tetsuo; http://lattes.cnpq.br/3165747089941318
In this work, composite materials of polyester matrix reinforced by short sisal fiber, by residue of wood and by hybrid system for sisal / residue of wood, arranged randomly, were produced using the minimum stages of technology processing in the productive step, with views to produce a composite material easy technically to produce. The polyester matrix used was a pre-accelerated tereftálica with cobalt naftenato and cured at room temperature with methyl ethyl ketone peroxide (MEK) in different proportions in relation to the resin, 0.33%, 1.66%, 3.33% and 5.00% by volume in order to evaluate the influence on mechanical properties. The sisal fibers were manually cut in lengths of 5, 10 and 15 mm and used in the way purchased and surface untreated. The residue of wood powder was used of maçaranduba wood. The composites were produced by manual moulding, without pressure and room temperature. Specimen were manufactured for evaluated matrix, composites reinforced by sisal, ranging of the length of the fibres, composites reinforced by maçaranduba residue and strengthening of hybrid composites, sisal / wood residue, in different proportions of the constituents. Mechanical properties were evaluated by tests of traction and Charpy impact and the areas of fracture generated were evaluated by scanning electron microscopy in order to correlate aspects of fracture with the mechanical properties. It was determined the specific mass of each series of specimen of each manufactured, and the volume fraction of the composite material. The results showed that the increase in the length of the sisal fiber, tensile strength and impact of composites has been increased, reaching the composite of sisal fibre, 15 mm, the best performance with the specimen series tested. The heterogeneity of size maçaranduba residue was negative effect on the mechanical properties of composites. The hybrid composites materials sisal / wood residue with higher content of fibers elevated in 80% of the mechanical properties obtained for the composite material reinforced only by sisal fiber.
Acesso aberto (Open Access)
Análise computacional dos campos de velocidade e temperatura do ambiente interno da usina termelétrica Santana - Amapá
(Universidade Federal do Pará, 2008-08-07) OLIVEIRA FILHO, Álvaro Henriques de; SAID, Mounsif; http://lattes.cnpq.br/8493361134195157
The numerical simulation of the airflow in internal environments is in the present time the most appropriate method for analysis of thermal comfort indoors. The airflow in these environments is configured as a complex one, therefore, in general, it is a combination of free-shear flow (jet) and of wall-shear flow, moreover, these are governed by inertia and buoyancy forces, characterizing a situation of mixing convection. The combination of these mechanisms creates an airflow with complex characteristics, as recirculation zones, vortices, detachment and re-attachment of boundary layer amongst others. Therefore, the precision of the solution will be directly connected, mainly, with the ability of the adopted turbulence model to reproduce the turbulent characteristics of the airflow and thermal transfers. The main objective of the present work was the computational simulation of the internal thermal environment of the enclosure which shelters the generators and the Wärtzilä engines of the thermo-electric power plant of Santana in the state of Amapá (Brazil). The mathematical formulation based on the solution of the general equations of conservation includes an analysis of the principal models of turbulence applied to the airflow inside the enclosure, as well as the heat transfer processes associated. The finite-volume numerical method is used in the discretization of the conservation equations, through the Fluent-Airpak software, for the analysis of the distribution of air velocity and temperature fields. The correct use of the software was tested and validated by successfully simulating problems solved by other authors. The numerical results of the airflow in the enclosure were compared with the experimental data and presented a good agreement, by considering the complexity of the simulated problem and the limitations and difficulties found during measurements. Moreover, simulations are presented of strategies for improvement of the thermal environment, based on the actual reality and on the results of the numerical simulations. Finally, simulations of a prototype solution are presented with the reduction of the internal temperature in the enclosure. This solution allows an increase of the exposure time inside the enclosure, from 20 up to 30%, and improves the thermal comfort of the thermo-electric power plant.
Acesso aberto (Open Access)
Variáveis térmicas de solidificação, espaçamento dentríticos secundários e resistência à corrosão de ligas hipoeutéticas Al-Ni
(Universidade Federal do Pará, 2008-08-14) COSTA, Giselle Barata; SÁ, Fernando Antonio de; http://lattes.cnpq.br/8275621144223544
In this research is carried out a sequence of experiments with Al-Ni hypoeutectic alloys to analyze the upward vertical directional solidification on transient conditions of heat flow. Experimental approaches were developed to quantitative the thermal variables of solidification, as follow: local time solidification; dislocation rate of liquidus isotherms, tip cooling rates and thermal gradients. This study analyzes the dendrite secondary arms spacing in relation to solidification thermal variables and to alloy composition, beyond link these parameters with corrosion resistance of these alloys. These experimental dendrite parameters, concerning to alloys solidification as Al - 1, 1,4 and 1,8%Ni, couldn’t be compared with the main theoretical model of dendrite growth by others researches, because, to alloy studied there shortage of thermophysic properties, impossible this comparison. The corrosive behavior is analyzed by potentiodynamic polarization technique and cyclic polarization technique lead into 3,5%NaCl solution on room temperature, coarse structure dendritics tend to increase the corrosion rates of Al-Ni hypoeutectic alloys. The experimental results obtained by the corrosion tests were correlated with dendrite microstructure. This way, experimental tendencies of growth dendrite were determined to upward vertical directional solidification.
Acesso aberto (Open Access)
Estudo de vibrações eólicas em linhas de transmissão de energia elétrica de alta tensão
(Universidade Federal do Pará, 2008-10-30) SANTOS, Alexandre Sá dos; SOEIRO, Newton Sure; http://lattes.cnpq.br/7303174583088137
The increasing demand for electrical energy has stimulated the technological advance of the equipment associated to its transport, generating a situation in which one has to operate under ever increasing nominal voltages, mainly due to economical reasons. This fact has a direct implication on the diameter of the conductors, elevating their cost, as well as that of the supporting structures. In order to overcome this problem, without cost elevation of the electrical transmission line project, the idea is to use more than one conductor per phase, in a parallel assembly with small distances between cables, which can be achieved through the insertion of spacers at regular intervals between the supporting towers. However, operational mechanical problems may arise such as, for example, total or partial rupture of cables and/or spacers due to dynamical wind excitations. Thus, this work investigates the dynamical behavior of a bundle of cables of electrical transmission lines, using a finite element model, which reproduces the coupling between cables and the transmission lines’ spacers-dampers and the fixing structures, considering non-linear geometrical effects due to huge cable displacements, and line continuity, i.e., the adjacent vain, which is taken into account by the model as an equivalent stiffness. Wind load is modeled through a non-deterministic process, from its statistical properties, such that two parts are considered: an average load, statistically analyzed, and a variable load, analyzed as a transient. Results show that the variable load part conduces to a dynamic response of the model, which could represent a dominant behavior. Therefore, the traditional methodology of assuming wind load as a static excitation could lead, in some cases, to disastrous consequences.