Navegando por Autor "GOMES NETO, Abel Ferreira"

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Acesso aberto (Open Access)
Teoria do funcional de densidade aplicada a reatividade química de combustíveis e biocombustíveis na fase gasosa: gasolina, etanol e gasolina-etanol
(Universidade Federal do Pará, 2015-03-10) GOMES NETO, Abel Ferreira; CHAVES NETO, Antonio Maia de Jesus; http://lattes.cnpq.br/3507474637884699; MACHADO, Nelio Teixeira; http://lattes.cnpq.br/5698208558551065
We performed a theoretical study using the Density Functional Theory, with the B3LYP functional and the basis set 6-311 ++ g (d,p) to calculate thermodynamic properties of the following fuels and biofuels: gasoline, ethanol and gasoline-ethanol mixture, all in gas phase. The simulations were performed using the Gaussian 09W and Hyperchem 7.5 softwares and allowed obtaining fuel properties, witch, were calculated from the weighted average for the properties to each of its major components, considering the mass fractions of components of two kinds of gasoline, a Standard kind and other commercial Regular. The simulations were performed at various temperatures in the range 0.5K - 1500K and under pressure of 1 atm, using continuous polarizable model to simulate solvated systems with each component. Conformational search, optimization and frequency calculations (Raman and Infrared) were simulated were performed, where, was possible obtain physical quantities associated with the chemical reactivity and the calorific value of the fuel during injection phase in combustion chamber. It was also possible to prove and quantify some relevant characteristics of the fuels, such as, The high antiknock potential of ethanol when it is compared to the gasoline, as well as the influence caused for the ethanol when blended with gasoline. These comparisons were made from the study of thermodynamic potentials (internal energy, enthalpy and Gibbs free energy) obtained during the simulations. In addition to these properties, were calculated the rate-change of Gibbs free energy in relation to temperature, specific heat at constant pressure and entropy of major components. This methodology has been reproduced using the PM3 and PM6 semi-empirical computational methods with the purpose of comparing its accuracy and computational cost to the study fuels, to results obtained from the B3LYP functional. We found that semi-empirical methods can generate results with a good precision for calculations of thermodynamic properties of major components, as such as, functional B3LYP showed, but with a computational cost far lower enabling this work presents itself as a methodology quite effective for the thermodynamic characterization of fuels and biofuels in the gas phase, when they are injected into the combustion chamber.
Acesso aberto (Open Access)
Teoria do funcional de densidade e ensemble canônico para análise termodinâmica do gás natural, gás de síntese e de suas misturas
(Universidade Federal do Pará, 2018-10-05) GOMES NETO, Abel Ferreira; CHAVES NETO, Antonio Maia de Jesus; http://lattes.cnpq.br/3507474637884699
In this work we performed a thermodynamic characterization of natural gas, synthesis gas and the mixtures of these two fuels, obtaining predictions based on the density functional theory and on statistical thermodynamics, through the canonical ensemble model. The study initially focused on verifies what method of the Density Functional Theory is more suitable for the thermodynamic analysis of natural gas, where properties were obtained, such as the following thermodynamic potentials: internal energy, enthalpy, Gibbs free energy and entropy. We conclude that B3LYP functional, along with the basis sets 6-311++g(d,p) corresponds to the most recommended method for the thermodynamic prediction of this fuel, the thermodynamic properties of the synthesis gas were analyzed, as well as the effects caused by the synthesis gas when mixed with natural gas. The results showed the synthesis gas can be a possible anti-knock additive, which a mixture containing up to 30% of synthesis gas can raise the resistance of natural gas to heating, reducing only about 15% of the energy their released in the combustion.