DEMEC - Departamento do Curso de Engenharia Mecânica

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/10750

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Finding hidden oscillations in the operation of nonlinear electronic circuits.
(2016) Rocha, R.; Torricos, Rene Orlando Medrano
Several dynamic behaviours can simultaneously coexist in the operation of a nonlinear electronic circuit. However, some of these dynamics are difficult to be observed due to their sensibility to initial conditions. The use of describing functions to determine the coexistence of multiple dynamics in the operation of an electronic circuit with nonlinear feedback is proposed.
Analysis of the energy efficiency of diesel oil consumption in the Brazilian Iron Ore Mining Company.
(2018) Fernandes, Eunírio Zanetti; Leal, Elisângela Martins; Figueiredo, Robson Lage; Reis, Gemírson de Paula dos
This paper aims to evaluate the diesel oil consumption between 2008 and 2015 in the production of iron ore in Brazil, creating correlations between energy intensity (production), economy and checking the impact of fuel prices on the commodity. During the analyzed period, the years 2008-2009 indicated economic crises, which interfered in the price and the commercialization of iron ore products. The physical intensity was 0.2% higher than the economic intensity. In the period from 2010 to 2014, economic activity remained more stable, with a decreasing trend, mainly due to the increase of iron ore prices. The physical intensity is much higher than the economic intensity influenced by the expansion of the Chinese economy. The year of 2014 indicated the end of the high iron ore price cycle and the beginning of supply and demand stabilization with consequent reduction in prices. In 2015, the market entered the stabilization phase, with a continuous reduction in unit production costs and transportation logistics. There was an abrupt change due to the strong increase of the economic intensity due to the fall of the international prices of iron ore. The diesel oil consumption plays a vital role in the scenario of cost reduction in iron ore production and a deeper analysis must be done in order to discover some options to change the energy matrix.
Acoustical performance of Helmholtz resonators used as vehicular silencers.
(2018) Martins, Lucas Rodrigues; Guimarães, Gustavo Paulinelli; Fragassa, Cristiano
This study proposes to evaluate the acoustical performance of a reactive vehicular silencer made entirely of Helmholtz resonator. Four or seven resonators are idealized to be in a series configuration, all the dimensions except cavity length and resonators are fixed. An algorithm processes inputted characteristic engine noise signal obtained from literature, identify peaks, and calculates ideal cavity length for attenuation. The transmission loss of the system is analytically calculated. Attenuation levels obtained are satisfactory. The required volume of the resonator to achieve the same resonance frequency as low frequency noise peak demands impractical cavity length, proving it to be flawed. It is suggested to use resonators of two or three different diameter for different frequency range in order to overcome this problem.
Análise e comparação do torque filete a filete no rosqueamento interno por machos de corte.
(2018) Vianello, Pedro Ivo Alves; Souza, R. F. A.; Silva, Marina Carla Bezerra da; Pereira, Igor Cezar
The thread process is responsible for internal and external threads creation which are of large application in several areas. Even though its large usage in industry, there are few papers about this process. In this paper, it was carried out torque fillet by fillet measurements over the chamfer portion of the tap and the torque comparation between tools from two distinct manufacturers. It was used M 10 x1,5 HSSE straight flute taps, with and without coating in tapping process on a grey cast iron GG30, in order to analyse the relation between the number of fillets in the tap’s chamfer and its geometry in torque signal behaviour.
Análise da temperatura filete a filete no rosqueamento interno por machos de corte.
(2018) Souza, R. F. A.; Vianello, Pedro Ivo Alves; Silva, Marcio Bacci da; Pereira, Igor Cézar
Among the manufacturing processes, threading stands out, as it can be accomplished by machining or by forming. This process is responsible for the creation of internal and external threads, which has great applicability in production lines. Due to the market’s great competitiveness, methods are sought to increase production by decreasing the time of each unit process. However, tapping is usually performed at low cutting speeds due to limitations related to the manufacturing process. The study of the tapping can bring benefits, such as the reduction of wear mechanisms, resulting in an increase in tool life. In this research, the temperature was measured from fillet to fillet in the conical part of the tool, varying the cutting speed and the number of fillets. The tap used is, M 10 x 1.5 HSS, uncoated in threading process for internal thread production in SAE 1045. To analyze the temperature was used the tool-workpiece thermocouple method on each fillet of the tap. The cutting speeds used were 10 and 25m / min. From the second fillet on the temperature is constant, even with the increase in the number of fillets, as expected.
Analysis of the coefficient of friction at the workpiece-tool interface in milling of high strength compacted graphite cast irons.
(2019) Silva, Leonardo Rosa Ribeiro da; Ruzzi, Rodrigo; Teles, Vinicius C.; Sales, Wisley Falco; Guesser, Wilson L.; Machado, Alisson R.
The coefficient of friction at the workpiece-tool interface is one of the main influencing parameters in machining. It can be tribologically investigated using conventional and open tribometers, however, there is no consensus as to which type of test has the best correlation with the real machining process. This work aims at investigating the use of three different methods to measure the coefficient of friction in the machining of three types of high strength compacted graphite cast irons, with variations in the size of the free graphite phase and the presence or absence of molybdenum carbides in the matrix. The coefficient of friction of the process was measured using two progressive load conventional tribological tests, the progressive load single sliding test with load ranging from 0.5 to 40 N and the progressive load reciprocate sliding test in both dry and starved lubrication regimen, with load ranging from 48 to 83 N. The coefficient of friction was also measured in a conventional machining center used as an open tribometer, where ramp milling tests were performed in workpieces fixed on a piezoelectric dynamometer, with a cutting depth varying from 100 μm to 0, to simulate a regressive load. The following machining parameters were varied: cutting speed, feed rate, tool geometry, tool coating and the use of minimum quantity of lubrication in contrast to dry machining. As the main results, the predominance of lubrication, even in small quantities, was observed as the most influential parameter in the coefficient of friction. An inverse relationship was also observed between the hardness of the materials and the coefficient of friction independent of the lubrication condition used. The results of the coefficient of friction obtained in progressive load re- ciprocate sliding and open tribometer tests showed the best correlation with those found in the literature for this kind of materials.
Technical analysis of a hybrid solid oxide fuel cell/gas turbine cycle.
(2019) Leal, Elisângela Martins; Bortolaia, Luis Antônio; Leal Júnior, Amauri Menezes
The relatively high operating temperature of the solid oxide fuel cell allows for a highly efficient conversion to power, internal reforming, and high-quality by-product heat for cogeneration or a bottoming cycle. Besides, high-temperature fuel cells offer a good opportunity for coupling to a gas turbine. Fuel cell systems have demonstrated minimal air pollutant emissions and low greenhouse gas emissions. This paper focuses on the investigation and technical analysis of a direct internal reforming solid oxide fuel cell (DIR-SOFC) and a gas turbine (GT) system. The technical analysis comprises of an energy and exergy analysis of the hybrid cycle, using the Gibbs function minimization technique for the methane steam reforming process. The assessment is performed to determine the influence of the hybrid cycle operating temperature and pressure, steam-to-carbon ratio and fuel and oxidant usage in the fuel cell. Equilibrium calculations are made to find the ranges of inlet steam-to-carbon ratio and the operating current density of the fuel cell. After that, a hybrid system consists of a DIR-SOFC and a GT is evaluated using computer simulation. The results showed that the fuel cell is the main power producer system at the design point. The high-energy efficiency (around 62%) and exergy efficiency (around 58%) are achieved by the hybrid cycle compared to fuel cell efficiency (about 40%) and the GT (around 38%). The power ratio (SOFC/GT) found was 1.50. An analysis varying the fuel cell current density and the GT pressure ratio was performed showing that the fuel cell power production decreases about 7% with increasing current density when the GT becomes the main power-producing equipment. However, the system energy efficiency decreases with the reduction of power produced by the fuel cell.
Study of the project parameters influence in the performance of solar collectors.
(2019) Mapa, Lidianne de Paula Pinto; Mendes, Bárbara de Morais; Bortolaia, Luis Antônio; Leal, Elisângela Martins
This paper aims to observe the influence of design parameters on the performance of plane solar collectors. From the energy balance of the plane solar collector, the mathematical model was implemented varying the following design parameters: (i) Thickness of the absorber plate; (ii) Distance between the absorber and the cover; (iii) Edge insulation thickness; (iv) Absorber emittance; (v) Conductivity of the absorber; (vi) Convective heat transfer coefficient inside the tubes; (vii) Distance between tubes; (viii) Wind velocity; (ix) Solar radiation incident; and (x) Back insulation thickness. These parameters were altered observing the influence on the optical efficiency; the coefficient of energy loss; the instantaneous efficiency; and the useful energy gain. From the results, it is possible to see that the parameters that most influence the performance of the solar collector are the distance between the absorber and the cover, the absorber emittance, the thermal conductivity of the absorber, the distance between tubes, wind speed and solar radiation incident.
Influence of metallurgical texture on the abrasive wear of hot-rolled wear resistant carbon steels.
(2019) Damião, Carlos Alberto; Alcarria, Gabriela; Teles, Vinicius C.; Mello, Jose Daniel Biasoli de; Silva Junior, Washington Martins da
Hot-rolled wear resistant carbon steel sheets are commonly applied in mining equipment as abrasive wear- resistant material for front loaders, chutes, etc. The rolling process can induce metallurgical texture in the form of alternating bands of ferrite and pearlite known as "banding" which affect the mechanical properties of the material. The goal of this work was to verify the impact of metallurgical texture on the abrasion resistance of hot- rolled wear resistant carbon steels. SEM images of the field specimens showed that the prevailing wear me- chanism was parallel scratches. This wear mechanism was replicated in the laboratory using a dry sand-rubber wheel wear tester. The particle size used in the abrasive wear test (0.15–0.30 mm) was defined by the topo- graphical analysis of the field sample. In addition, linear scratch tests were conducted to determine the specific scratch energy. The block specimens used in the abrasion wear tests were cut from hot rolled plates with and without metallurgical texture taking into account the rolling direction. Metallographic analysis of these samples showed an anisotropic microstructure related to the lateral and transversal surfaces of the plates. The wear rate of the lateral surface was up to 40% lower than that of the upper surface. This result was attributed to the presence of metallurgical texture that increased hardness. In addition, the wear rate presented a linear re- lationship to the scratch specific energy. In this case, samples without metallurgical texture were more difficult to scratch. The analysis of the specific energy and wear rate parameters clearly showed the anisotropy of the samples presenting metallurgical texture, which corresponded to the highest abrasive wear rate.
Tire pyrolysis oil in Brazil : potential production and quality of fuel.
(2020) Gamboa, Alexander Alberto Rodriguez; Rocha, Ana Maura Araújo; Santos, Leila Ribeiro dos; Carvalho Junior, João Andrade de
he application of tire pyrolysis technology in a country will be feasible whenever competitive and attractive products are produced. In this work, quantitative and qualitative evaluation of the potential of tire pyrolysis oil (TPO) in Brazil was carried out. The quantitative evaluation consisted of determining the amount of feedstock (waste tires) available and the volume of TPO that can be produced in Brazil per year. The qualitative evaluation was applied to a sample of TPO produced in Brazil, determining its main atomization properties: specific mass, viscosity and surface tension. In addition, a theoretical comparison of the quality of TPO spray was performed, comparing the expected mass median diameter for TPO and diesel oil (DO) spray. The results of the quantitative evaluation showed that it is possible to produce around 230 to 280 thousand m3 per year of TPO, equivalent to about 2% of the onshore petroleum and fuel oil (FO) produced in Brazil for both cases. Meanwhile, the qualitative evaluation showed that the TPO produced in Brazil has greater ease of atomization in relation to the FO produced and marketed in the country. However, preserving the quality of TPO requires proper storage, since prolonged exposure to the environment increases its viscosity by up to four times, and can change it from medium oil (22.3o API) to heavy oil (14.1o API).
The golden mussel proteome and its response to niclosamide : uncovering rational targets for control or elimination.
(2020) Sanson, Ananda Lima; Cosenza Contreras, Miguel de Jesus; Marco, Ricardo De; Neves, Leandro Xavier; Mattei, Bruno; Silva, Gustavo Gonçalves; Magalhães, Paulo Henrique Vieira; Andrade, Milton Hércules Guerra de; Borges, William de Castro
The Asian invasive species Limnoperna fortunei (Dunker, 1857), known as the golden mussel, causes great economic and environmental damage due to its fixative capacity and accelerated proliferation. Molecular studies for the control of larval and adult forms are of great economic, scientific and technological interest. Here, we first report on the compositional analysis of the L. fortunei proteome obtained through shotgun analysis using LC-MS/ MS. Among those 2790 proteins identified, many of them related to secretory processes and membrane receptors. Our second approach consisted in exposing the mollusc to the molluscicide niclosamide to evaluate the induced proteomic alterations. Exposure to niclosamide at 0.25 mg/L for 24 h resulted in a pronounced differential abundance of proteins when compared to those obtained when exposure was reduced to 4 h at 2.3 mg/ L. In total, 342 proteins were found differentially expressed in the responsive individuals as revealed by labelfree quantitative proteomics. Regarding the affected cell processes were: cell division and differentiation, cytoskeletal organization and compartment acidification (upregulated), and energy metabolism (downregulated). Our findings constitute the first inventory of the expressed proteome of the golden mussel and have the potential to contribute with a more rational proposition of molecular targets for control and monitoring of this species. Significance: With the recent availability of transcriptomic and genomic data applied to L. fortunei the timing is right to interrogate its putative gene repertoire using proteomic techniques. These have the potential to validate the existence of the predicted genes, infer their relative abundance and quantify their levels as a response to environmental stressors or various agents. Here we provided an inventory of the golden mussel proteome and evaluated its response to the molluscicide niclosamide. The obtained results open new avenues for intervention aimed at its control or elimination, particularly by targeting the various cellular processes that were uncovered.
Stability analysis for the Chua circuit with cubic polynomial nonlinearity based on root locus technique and describing function method.
(2020) Rocha, Ronilson; Medrano Torricos, Rene Orlando
This work investigates the dynamics of the Chua circuit with cubic polynomial nonlinearity using methods for stability analysis based on linearization and frequency response. Root locus technique maps eigenvalues of the linearized system in order to analyze the local stability, which allows to verify dynamic features, motion patterns, and attractor topologies. The method based on describing functions allows analyze effects of the cubic nonlinearity in the system, as well as predict equilibrium and fixed points, periodic and chaotic orbits, limit cycles, multistability and hidden dynamics, unstable states, and bifurcations. The stability of the Chua circuit with cubic polynomial nonlinearity is analyzed using both approaches in order to identify and map dynamics in parameter spaces. Numerical investigations based on computational simulations corroborate the theoretical results obtained using this stability analysis. This theoretical analysis and the numerical investigations present interesting insights about the dynamics of the Chua circuit with cubic polynomial nonlinearity and provides a design tool for electroelectronic implementations.
An approach to torque and temperature thread by thread on tapping.
(2020) Pereira, Igor Cezar; Vianello, Pedro Ivo Alves; Boing, Denis; Guimarães, Gilmar; Silva, Marcio Bacci da
During internal threading, small alterations in cutting parameters, tool geometry, or process characteristics produce considerable effects on torque and temperature behavior. Understanding these effects is critical to the design and development of new taps. In this work, the torque behavior for a tap operation is evaluated as a function of the number of threads, tool manufacturer, and angle of the taper region of the tool. The chip–tool interface temperature was analyzed, considering the influence of cutting speed and number of threads. Experimental tests were carried out using M10x1.5 taps and cutting speeds of 10 m/min and 25 m/min. Taps with two different geometries were considered in this analysis. The results show a difference in the distribution of the torque along the threads of the conical part between the tools. The presence of adhered material increased the torque during the reverse stage. The torque during the reverse stage for a tap with a damaged tooth was approximately 50% of the torque during the cutting stage. The temperature showed an increase with the number of threads stabilizing between the fourth and fifth threads and increasing again in the sixth filled due to adhesion of workpiece material.
Analysis of a hybrid molten carbonate fuel cell and gas turbine cycle.
(2020) Leal, Elisângela Martins; Silva, Barbara Emanuelle Sanches; Leal Júnior, Amauri Menezes
Background: Hybrid systems with fuel cells and thermal engines are studied with promising results. Molten carbonate fuel cells (MCFC) show many advantages compatible with the current demands for energy production in a sustainable competitive way. Materials and Methods: This paper focuses on the computational investigation of an indirect internal reforming MCFC coupled to a gas turbine (GT) system. The technical analysis comprises of energy analysis of the hybrid cycle, using the Gibbs function minimization technique for the methane steam reforming process. The assessment is performed to determine the influence of the hybrid cycle operating temperature and pressure, steam-to-carbon ratio, and fuel and oxidant usage in the fuel cell. Results: Results show that the increase in temperature and in operating pressure of the fuel cell and the fuel reform rate improves the hybrid system performance. Variation in the utilization factor, however, did not determine an expressive increase in system efficiency. For the same fuel mass flow rate, it is possible to see that the variation in the operating temperature of the fuel cell resulted in an increase in the total power of the hybrid system when compared to the results of the pressure increase. The increase in temperature resulted in a maximum increase of 12% in delivered power and corresponding to about 7% system efficiency increase. Instead, an increase in pressure of about 4% corresponding to an increase of about 2% system efficiency. Conclusion: Although an increase in the fuel cell's power density was observed for the same mass flow rate in the system, the pressure negatively influenced the total delivered power by the fuel cell.
Measuring and comparing the ignition delay time of the reference diesel, convectional diesel, additive ethanol and biodiesel from soybean oil using a shock tube.
(2020) Santana, Cláudio Márcio; Barros, José Eduardo Mautone; Almeida Junior, Helder Alves de; Braga, Jorgimara de Oliveira; Bosch Neto, Juan Canellas
The objective of this work is to correlate the ignition delay times of reference diesel, convectional diesel, ethanol and biodiesel from soybean oil measured in a shock tube with a 5% additive increase in the cetane number. The results were correlated with the cetane number of the respective fuels and compared with the ignition delay times available in the studies by oth- ers authors. The shock tube is a metal tube in which gas at low pressure and at high pressure is separated by a diaphragm. When the diaphragm breaks in predetermined conditions (high pressure in this case) produces shock waves that move from the high-pressure chamber (known driver section) to the low-pressure chamber (known driven section). The tests were per- formed under the following initial conditions: refected shock wave temperature from 903 to 1260 K, equivalence ratio of 1 and refected shock wave pressures of 24 bar. For determining and recording the ignition delay time, pressure sensors with high acquisition rate and luminosity sensors were used. With information from pressure sensors and the luminosity sensor, ignition delay times of reference diesel, convectional diesel, additive ethanol and biodiesel from soybean oil were recorded. We concluded that the ignition delay time of additive ethanol was twice as large as the ignition delay time of reference diesel. The ignition delay time of biodiesel from soybean oil was approximately three times greater than the ignition delay time of reference diesel. The ignition delay time of the reference diesel was smaller than the convectional diesel. The contribution of this work is that it shows why additive ethanol and pure biodiesel should not be used as substitutes for diesel compression ignition engines without any major changes in the engines. The ignition delay times of these fuels are at least two to three times longer than the ignition delay time of reference diesel.
Development of a low-cost instrumentation system applied to an electrolytic cell.
(2020) Reis, Gemírson de Paula dos; Matos, Saulo Neves; Rêgo Segundo, Alan Kardek; Leal, Elisângela Martins; Figueiredo, Robson Lage
Humanity’s growing long-term energy demand will be the opportunity for new energy generation sources. In this scenario, the use of hydrogen as an energy source has become an interesting alternative to energy production, as the use of fossil fuels can lead to harmful consequences, such as the emission of greenhouse gases. This paper presents the development of a low-cost instrumentation system for monitoring the temperature, current, voltage, and gas flow rate of a dry electrolytic cell. Through the electrolysis process, the cell generates a hydrogen-rich gas which is used as an additive in an internal combustion engine to reduce pollutant gas emissions and primary fuel consumption. The measured variables are presented as a function of the time to analyze the behavior of the electrolyzer. The main advance reported in this work is related to the use of a low-cost sensor for a hydrogen-rich gas flow measurement, in which calibration was performed indirectly using a rotameter as a reference. The calibration curve adjusted to the experimental data by linear regression presented a coefficient of determination of 0.9957. Thus, the use of the low-cost sensor is a feasible alternative for measuring the electrolysis gas generated by the cell.
Modelo de simulação e análise termodinâmica e econômica de microturbinas a gás em operação com biogás e gás natural e acionamento fotovoltaico do compressor.
(2021) Trindade, Gustavo Sana; Bortolaia, Luis Antônio; Bortolaia, Luis Antônio; Machado, Luiz; Leal, Elisângela Martins; Murta, Jorge Luiz Brescia
O crescente aumento da demanda por eletricidade no Brasil e no mundo aliado à preocupação ambiental devido à emissão de poluentes está motivando a investigação e desenvolvimento de fontes sustentáveis de energia e a interação entre elas. Nesse contexto, a geração de energia elétrica por meio do aproveitamento da energia oriunda do Sol e de resíduos sólidos urbanos pode ser uma opção efetiva para diversificação da matriz energética brasileira. Portanto, no intuito de ratificar essa tendência, o foco deste trabalho é o desenvolvimento de um modelo de simulação termodinâmico para análise de microturbinas a gás de 30 kWe, 65 kWe e 200 kWe sob operação com biogás ou gás natural e acionamento fotovoltaico do compressor. Em termos metodológicos, o software Engineering Equation Solver foi utilizado como ferramenta de cálculo para resolução do modelo termodinâmico em regime permanente elaborado para a construção de tabelas paramétricas e gráficos que permitem avaliar o desempenho das máquinas térmicas convencional e híbrida em cidades escolhidas como representantes para as 5 regiões brasileiras. O software Radiasol 2 foi utilizado para aquisição dos dados de insolação ao longo do ano. As microturbinas híbridas apresentam menor consumo específico de combustível, visto que não há necessidade de descontar a potência produzida na turbina para acionar o compressor quando a eletricidade produzida pelos painéis fotovoltaicos é suficiente. Além disso, uma análise econômica é proposta para avaliar a viabilidade econômica dos projetos. Os resultados termodinâmicos mostraram que o consumo específico de combustível para microturbinas híbridas é sempre menor que metade do determinado para microturbinas convencionais. Os resultados econômicos mostraram que a hibridização de microturbinas a gás com energia fotovoltaica é sempre vantajosa para os parâmetros de entrada considerados, mesmo na região sul, onde a radiação solar é menos intensa e a energia adquirida pelas concessionárias é mais barata. Tempos de retorno do investimento são menores que o tempo de vida útil dos equipamentos, receitas positivas são encontradas e o valor da eletricidade gerada pelos meios propostos em muitos casos é menor que o pago atualmente para as concessionárias. Em Belém (PA), por exemplo, tempos de retorno do investimento menores que seis anos e receitas financeiras para 25 anos da ordem de dezenas de milhões de reais são encontrados.
Dynamic behavior of tapping axial force.
(2021) Pereira, Igor Cezar; Mapa, Lidianne de Paula Pinto; Barros, Thamiris Nogueira de; Fortes, Reinaldo Clemente; Silva, Marcio Bacci da; Guimarães, Gustavo Paulinelli
Background Tapping is one of the processes that most requires attention in the industry, due to the stage in which it occurs and its characteristics. In the case of tapping, it is common to use components and equipment with less rigidity, which com promises the dynamic behavior in several situations and can lead to process distortion or failure. Purpose The objective of this paper is to study the dynamic behavior of tapping in relation to several characteristics of the process. Methods The dynamic behavior of the force signal was used to evaluate the process, varying the cutting parameters and the clamping system of the workpiece. Results The experimental results indicate that the foating system did not present a good dynamic behavior at high cutting speeds, this greater application of vibration is due to the resonance due to the combination of oscillations under forced and natural vibration. Conclusions The natural frequency of the foating fxture system infuenced the behavior of the axial forces. The increase in cutting speed resulted in a direct increase in the axial force vibrations as its frequency came close to the natural frequency of the system. Through dynamic analysis of the axial force signal observed the dynamic characteristics of the process and the machine tool. This allowed the dynamic evaluation of the system through the measurement of force signals generated in the threading process.
Análise termoeconômica e ambiental da central termelétrica de uma usina siderúrgica integrada a coque simulando numericamente o uso do hidrogênio como combustível auxiliar.
(2021) Coura, Dimas Pereira; Leal, Elisângela Martins; Leal, Elisângela Martins; Silva, Guilherme Liziero Ruggio da; Assis, Paulo Santos; Bortolaia, Luis Antônio; Rocha, Luiz Joaquim Cardoso
A siderurgia apresenta fundamental importância no contexto energético do Brasil, sendo caracterizada como um dos grandes consumidores de eletricidade no país. Para ter competitividade no mercado global, uma indústria siderúrgica precisa apresentar um excelente plano estratégico. Este plano inclui um planejamento energético eficiente, buscando um melhor aproveitamento dos recursos, baixos impactos ambientais e custos operacionais. As centrais termelétricas em ciclo Rankine das usinas siderúrgicas integradas demonstram grande potencial econômico, uma vez que fazem uso dos próprios gases residuais do processo. O objetivo principal deste trabalho é analisar, do ponto de vista termoeconômico, a central termoelétrica de uma indústria siderúrgica, observando a influência da adição de hidrogênio juntamente com os gases do processo siderúrgico. A geração de hidrogênio é pela eletrólise da água, alimentada eletricamente por placas fotovoltaicas. A metodologia compreende o uso de um modelo computacional criado através do software Cycle Tempo versão 5.0. Para validação do modelo, os dados da central termoelétrica são usados, como parâmetro operacionais, variáveis do fluido de trabalho e a descrição dos equipamentos. Após, é realizada a introdução do hidrogênio como combustível auxiliar na caldeira, com avaliação do impacto dessa adição. A modelagem termoeconômica tem como finalidade obter um sistema de equações de custos que representa matematicamente o processo de formação de custos na planta. Em 39 simulações computacionais e 7 cenários de misturas de combustíveis possíveis e realizando a mistura com o gás de alto forno, o gás de coqueria e o gás de aciaria com hidrogênio além da uma análise termoeconômica. Os resultados apontam que até 30% de hidrogênio com o gás de alto forno é possível de se obter eficiência energética e exergética equivalente ao cenário zero, que mais representa a operação na central termoelétrica e ainda reduzir o custo com combustível.
Corrosion behavior of low carbon steel processed by ECAP in neutral and alkaline environment.
(2021) Braga, Jorgimara de Oliveira; Lins, Jefferson Fabricio; Castro, Gabriel Pessoa de; Almeida Junior, Helder Alves de; Santos, Igor Cuzzuol dos; Sousa, Gustavo Henrique; Criscuolo, Izabel Lima; Santana, Cláudio Márcio; Pereira, Ursula Cid
The purpose of this study was to evaluate the corrosion behavior of 1010 steel processed by Equal Channel Angular Pressing (ECAP), a technique that induces severe plastic deformation (SPD) in materials. The samples were processed by one and two passes of ECAP throught routes A and C. The corrosion behavior was evaluate using the potentiodynamic polarization and electrochemical impedance spectroscopy, using NaCl (pH= 6.5) and sodium hydroxide/sodium phosphate (pH= 10.5) solutions. The polarization tests showed better performance for the samples processed by ECAP than in the as cast samples both in alkaline and neutral solutions. The results showed that alkaline solution presented higher corrosion rate for the as cast and one ECAP pass materials. It is seen that samples processed throught routes A and C develop a film stabilization on the surface of these samples. In addition, the values of polarization resistance obtained from the electrochemical impedance spectroscopy in NaCl environment were higher for sample processed in route C.