Analysis of two methods for estimating the temperature dependence of the gas-phase chemical reactions rate constants




The issues of structural-parametric identification of kinetic models intended for mathematical modeling of physical and chemical processes in gas dynamics are discussed. An analysis was made of two methods for estimating the temperature dependence of the rate constants of gas-phase chemical reactions: using a standard model based on the well-known Arrhenius formula and a new one proposed relatively recently. The focus of the article is on the basic parameter of the temperature dependence of the rate constants - the activation energy. The values of activation energy for combustion reactions of a mixture of hydrogen and oxygen, obtained by methods of approximation of experimental data based on the Arrhenius formula, calculations based on the theory of the transition state, and values of activation energy obtained using a new model, are compared. According to this model, for exothermic reactions, the activation energy is always equal to zero, while for endothermic reactions, the activation energy is determined by the difference between the potential energies of the final and initial states in a given reaction and is numerically equal to its absolute value. It is shown that the application of this method for estimating the activation energy gives results that are in good agreement with empirical data.

chemical reactions, kinetic models, structural-parametric identification, rate constants, activation energy.


Volume 24, issue 1, 2023 year


Анализ двух способов оценки температурной зависимости констант скорости газофазных химических реакций

Обсуждаются вопросы структурно-параметрической идентификации кинетических моделей, предназначенных для математического моделирования физико-химических процессов в газовой динамике. Выполнен анализ двух способов оценки температурной зависимости констант скорости газофазных химических реакций: с использованием стандартной модели на основе известной формулы Аррениуса и новой, предложенной сравнительно недавно. Основное внимание в статье уделяется базовому параметру температурной зависимости констант скорости – энергии активации. Проведено сопоставление значений энергии активации для реакций горения смеси водорода с кислородом, полученных методами аппроксимации экспериментальных данных на основе формулы Аррениуса, расчетов на основе теории переходного состояния и значений энергии активации, полученных с использованием новой модели. Согласно этой модели, для экзотермических реакций энергия активации всегда равна нулю, а для эндотермических энергия активации определяется разностью потенциальных энергий конечного и начального состояний в данной реакции и численно равна ее абсолютной величине. Показано, что применение этого способа оценки энергии активации дает результаты, которые хорошо согласуются с эмпирическими данными.

химические реакции, кинетические модели, структурно-параметрическая идентификация, константы скорости, энергия активации.


Volume 24, issue 1, 2023 year



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