Avaliação do limite de inflamabilidade inferior e concentração limite de oxigênio de misturas QAV – 1/etanol anidro em ar e atmosferas inertes
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Data
2021-05-07
Autores
Rios Escalante, Edwin Santiago
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Universidade Estadual Paulista (Unesp)
Resumo
A substituição parcial de combustível fóssil por combustíveis alternativos obtidos da biomassa, é uma possível opção para a sustentabilidade ambiental em aplicações aeronáuticas. No entanto, a inflamabilidade e risco de explosão no transporte e manuseio a que são sujeitos, têm que ser avaliados quando misturados com querosene de aviação (QAV – 1) em diferentes proporções. Os limites de inflamabilidade são características essenciais na prevenção da ignição, propagação da chama e consequente explosão de misturas inflamáveis, podendo ser classificados em duas categorias: (1) Limites de Inflamabilidade Inferior (LII) e (2) Limites de Inflamabilidade Superior (LIS). No entanto, na presença de gases inertes, a Concentração Limite de Oxigênio (CLO) é um parâmetro que tem ganhado interesse no controle e extinção da chama. A proposta do presente trabalho é determinar experimental e analiticamente os LIIs e CLOs de misturas QAV – 1/etanol anidro em ar e atmosferas inertes às diferentes condições de pressão e temperatura, com o intuito tanto de entender o fenômeno de ignição quanto de validar os requerimentos de inertização de recintos confinados contendo este tipo de misturas, visando o futuro uso de etanol anidro na indústria aeronáutica de pequeno e grande porte. A avaliação dos efeitos da pressão, temperatura e atmosferas inertes sobre os LIIs e CLOs de combustíveis tipo Jet – XX, sendo XX a concentração de QAV – 1 na mistura, foi realizada em uma bancada experimental montada segundo norma Americana ASTM – E681. O planejamento fatorial 2𝑘�� foi usado com o intuito de diminuir o tempo de execução dos experimentos. Também, foram avaliadas as incertezas a fim de estimar os erros de medição. Além disso, usando Leis, Definições e Proposições de grande importância histórica na Filosofia Natural, procedeu-se com duplo método cientifico: indutivo – dedutivo para formular a Teoria das forças atrativas e repulsivas na ignição por faísca. Desta forma, foram encaradas hipóteses sobre a possível distribuição das moléculas (ar, combustível e gás inerte) para a ocorrência ou prevenção da ignição. As diferenças entre os valores calculados e medidos foram avaliadas com AARE (%) e, a probabilidade de ajuste dos dados experimentais com as distribuições propostas no presente trabalho, foi estimada com o teste Chi-quadrado (χ2) . Em alguns casos, o coeficiente de correlação (R2) também foi usado. Os resultados mostraram que tanto LII quanto a CLO foram levemente afetados com a variação da pressão e temperatura. O 𝐶��𝑂��2 demostrou ser mais efetivo que 𝑁��2 para a inertização de misturas inflamáveis. Na presença de 𝐶��𝑂��2, a mínima CLO do QAV – 1 e etanol anidro é 16% e 13%, respectivamente, o que indica que o etanol anidro é mais perigoso que o QAV – 1 devido à sua alta volatilidade e baixo ponto de fulgor. Finalmente, a teoria proposta foi validada com os testes experimentais encontrando-se uma adequada aproximação entre as hipóteses formuladas e as observações experimentais em diferentes condições de pressão e temperatura. Isto significa que apelando à matéria e movimento é possível dar respostas aos diferentes fenômenos encontrados na natureza.
Partial replacement of fossil fuel with alternative fuel obtained from biomass is a possible option for sustainability in aeronautical applications. However, their flammability and risk of explosion in transport and handling must be assessed when mixed with fossil fuels in different proportions. Flammability limits are considered essential characteristics in assessing flame propagation and explosion hazards. They can be classified into two categories: (1) Lower Flammability Limits (LFL) and (2) Upper Flammability Limits (UFL). However, in presence of inert gases, Limit Oxygen Concentration (LOC) is the parameter that has gained interest in flame control and extinguishing. The purpose of this work is to determine analytically and experimentally the LFL and LOC of jet fuel / anhydrous ethanol blends in air and inert atmospheres at different pressure and temperature conditions, in order to validate the inertization requirements of confined enclosures containing this type of mixtures, aiming at the future use of anhydrous ethanol in the small and large aviation industry. Experimental evaluation of the effects of pressure and temperature on LIIs of Jet - XX fuels, being XX the percentage of jet fuel in the mixture, was made using a flammability apparatus build according to ASTM E - 681 standard. The factorial design 2𝑘� was used aiming to decrease the execution experiments time. Additionally, the uncertainties were evaluated aiming to estimate the measurement error. Besides, using Laws, Definitions and Propositions of great historical importance in Natural Philosophy was proceeded in the double scientific method: deductive and inductive to formulate the theory of the attractive and repulsive forces in spark ignition. In this way, hypotheses were raised about the possible molecular distribution (air, fuel and inert gas) for the occurrence or prevention of the ignition. The differences between measured and calculated values were evaluated with AARE (%) and the fit goodness probability of experimental values with the mathematically model proposed was estimated with Chi - square test (𝜒�2). In some cases, the correlation coefficient (𝑅�2) was also used. The results have shown that, both LFL and LOC are slightly affected by the pressure and temperature variation. 𝐶�𝑂�2 proved to be more effective than 𝑁�2 for the flammable mixtures inertization. In 𝐶�𝑂�2 presence, the minimum LOC of the QAV-1 and anhydrous ethanol is 16% and 13%, respectively, indicating that ethanol is more dangerous than QAV-1 due to, its high volatility and low flash point. Finally, the proposed theory was validated based on experimental tests finding an adequate approximation between the hypotheses formulated and the experimental observations at different pressure and temperature conditions. It means that appealing to matter and motion is possible to draw responses to the several phenomena found in nature.
Partial replacement of fossil fuel with alternative fuel obtained from biomass is a possible option for sustainability in aeronautical applications. However, their flammability and risk of explosion in transport and handling must be assessed when mixed with fossil fuels in different proportions. Flammability limits are considered essential characteristics in assessing flame propagation and explosion hazards. They can be classified into two categories: (1) Lower Flammability Limits (LFL) and (2) Upper Flammability Limits (UFL). However, in presence of inert gases, Limit Oxygen Concentration (LOC) is the parameter that has gained interest in flame control and extinguishing. The purpose of this work is to determine analytically and experimentally the LFL and LOC of jet fuel / anhydrous ethanol blends in air and inert atmospheres at different pressure and temperature conditions, in order to validate the inertization requirements of confined enclosures containing this type of mixtures, aiming at the future use of anhydrous ethanol in the small and large aviation industry. Experimental evaluation of the effects of pressure and temperature on LIIs of Jet - XX fuels, being XX the percentage of jet fuel in the mixture, was made using a flammability apparatus build according to ASTM E - 681 standard. The factorial design 2𝑘� was used aiming to decrease the execution experiments time. Additionally, the uncertainties were evaluated aiming to estimate the measurement error. Besides, using Laws, Definitions and Propositions of great historical importance in Natural Philosophy was proceeded in the double scientific method: deductive and inductive to formulate the theory of the attractive and repulsive forces in spark ignition. In this way, hypotheses were raised about the possible molecular distribution (air, fuel and inert gas) for the occurrence or prevention of the ignition. The differences between measured and calculated values were evaluated with AARE (%) and the fit goodness probability of experimental values with the mathematically model proposed was estimated with Chi - square test (𝜒�2). In some cases, the correlation coefficient (𝑅�2) was also used. The results have shown that, both LFL and LOC are slightly affected by the pressure and temperature variation. 𝐶�𝑂�2 proved to be more effective than 𝑁�2 for the flammable mixtures inertization. In 𝐶�𝑂�2 presence, the minimum LOC of the QAV-1 and anhydrous ethanol is 16% and 13%, respectively, indicating that ethanol is more dangerous than QAV-1 due to, its high volatility and low flash point. Finally, the proposed theory was validated based on experimental tests finding an adequate approximation between the hypotheses formulated and the experimental observations at different pressure and temperature conditions. It means that appealing to matter and motion is possible to draw responses to the several phenomena found in nature.
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Palavras-chave
Limite de Inflamabilidade Inferior (LII), Concentração Limite de Oxigênio (CLO), Querosene de avião (QAV – 1), Etanol anidro, Filosofia natural, Lower Flammability limits (LFL), Limit Oxygen Concentration (LOC), Jet fue, Anhydrous ethanol, Natural Philosophy, Combustível - pesquisa, Etanol, Engenharia sustentável