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Abstract(s)
O presente trabalho aborda o estudo de um motor de combustão interna, que segue o ciclo de Otto
e utiliza como combustível uma mistura composta por hidrogénio e gasolina. O principal objetivo
deste trabalho consiste em estudar a viabilidade da utilização do hidrogénio neste tipo de motores
relativamente à produção de NOx. Para tal recorreu-se a um modelo matemático baseado no
mecanismo cinético de Zeldovich e realizaram-se diversas simulações para várias condições de
queima do motor de forma a poder retirar conclusões.
Elaborou-se uma revisão bibliográfica, que visou enquadrar o tema em estudo, abordando matérias
como motores de combustão convencionais, motores de combustão que utilizam o hidrogénio
como combustível, a produção de NOx e mecanismos cinéticos e, por fim, a regulamentação
existente relativamente às emissões de NOx.
Após a obtenção dos resultados, foi possível concluir que o aumento do excesso de ar, o aumento
da taxa de compressão e o aumento da concentração de gasolina na mistura provocam uma
diminuição das emissões do poluente e também que, no melhor cenário estudado, as emissões de
NO estavam acima do limite mínimo imposto pela união europeia.
Espera-se que esta dissertação possa servir de base à implementação deste tipo de motores em
veículos já existentes e também que possa inspirar futuros trabalhos nesta área, considerando que
a poluição provocada pelos combustíveis fósseis é um problema real, que poderá inviabilizar por
completo a existência de meios de transporte num futuro não tão distante, se não forem
encontradas alternativas sustentáveis.
This work addresses the study of an internal combustion engine, which follows the Otto cycle, and uses as fuel a mixture composed of hydrogen and gasoline. The main objective of this work will be to study the feasibility of using hydrogen in this type of engine in relation to NOx production. For this purpose, a mathematical model based on Zeldovich’s kinetic mechanism was used and several simulations were performed for various engine burning conditions in order to draw conclusions. A literature review was prepared, which aimed to frame the subject under study, addressing topics such as conventional combustion engines, combustion engines that use hydrogen as fuel, NOx production and kinetic mechanisms and, finally, the existing regulation regarding NOx emissions. After obtaining the results, it was possible to conclude that the increase in excess of air, the increase in the compression rate and the increase in the concentration of petrol in the mixture, lead to a decrease in emissions of the pollutant and also that, in the best scenario studied, NO emissions were above the minimum limit imposed by the European Union. It is hoped that this dissertation can serve as a basis for the implementation of this type of engines in existing vehicles and also that it can inspire future work in this area, considering that the pollution caused by the problem of fossil fuels is quite a real problem, and that could completely render the existence of means of transportation in the not so distant future, if no sustainable alternatives are found.
This work addresses the study of an internal combustion engine, which follows the Otto cycle, and uses as fuel a mixture composed of hydrogen and gasoline. The main objective of this work will be to study the feasibility of using hydrogen in this type of engine in relation to NOx production. For this purpose, a mathematical model based on Zeldovich’s kinetic mechanism was used and several simulations were performed for various engine burning conditions in order to draw conclusions. A literature review was prepared, which aimed to frame the subject under study, addressing topics such as conventional combustion engines, combustion engines that use hydrogen as fuel, NOx production and kinetic mechanisms and, finally, the existing regulation regarding NOx emissions. After obtaining the results, it was possible to conclude that the increase in excess of air, the increase in the compression rate and the increase in the concentration of petrol in the mixture, lead to a decrease in emissions of the pollutant and also that, in the best scenario studied, NO emissions were above the minimum limit imposed by the European Union. It is hoped that this dissertation can serve as a basis for the implementation of this type of engines in existing vehicles and also that it can inspire future work in this area, considering that the pollution caused by the problem of fossil fuels is quite a real problem, and that could completely render the existence of means of transportation in the not so distant future, if no sustainable alternatives are found.
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Keywords
Internal combustion engines hydrogen NOx chemical kinetics Zeldovich mechanism