Ionic structure of methane flames

Pedersen, Timothy
Major Professor
Robert C. Brown
Committee Member
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Mechanical Engineering
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Mechanical Engineering

The objective of this research was to predict the structure of ions generated in methane flames. These simulations might lead to a better understanding of the interactions between ions in hydrocarbon flames. It was thought that such an understanding could lead to technology for electrically controlling combustion processes, formation of soot, and heat transfer;The reaction mechanisms used in this study was for a methane or hydrogen/methane flame. It contains reactions for the oxidation of fuels, chemiionization, ion-molecule reactions, and dissociative recombination. A computer model was developed to evaluate the formation of ions based on the proposed reaction mechanism;The computer code developed solved the governing equations of a laminar, premixed, one-dimensional flame immersed in an electric field. It included an iterative method that employed time splitting and finite difference techniques. Time dependent forms of the governing equations were solved until the solution relaxed to steady state;The saturation currents predicted by this model were used to determine the effective activation energies for the ionic phenomena. These values were successfully compared to experimental data. The activation energies were then compared to the values in the reaction mechanism. This led to the prediction of the ionic structure in methane flames;It appears that the depletion of the ions in the flame was by the recombination reaction H[subscript]3O[superscript]+ + e[superscript]- → H + H[subscript]2O. It was also demonstrated that C[subscript]2H[subscript]3O[superscript]+ + H[subscript]2 → H[subscript]3O[superscript]+ + C[subscript]2H[subscript]2 was the rate limiting reaction in determining saturation currents. The activation energy for this reaction was found to be in agreement with the value predicted using the saturation currents.