Comparative Study of Key Reactions Affecting Nitrogen Oxide Formation in Methane Laminar Premixed Flame

Abstract

Nitrogen oxides (NOx), classified as an indirect greenhouse gas (GHG), are increasing in demand for reduction as emission regulations are expanded not only in internal combustion engines but also throughout the industry. Nitrogen atoms are dissociated at relatively low temperature and can be easily converted to NOx by radicals and intermediates, so the reaction pathway is complex and changes in a short time. Therefore, numerical analysis methods should be used to simulate combustion phenomena and analyze chemical reactions, emphasizing the importance of the reaction mechanism, which includes reaction constants and reaction pathways. In this study, the laminar premixed flame was simulated using a numerical analysis method, and the NOx formation characteristics were identified according to the analysis variables using a reaction mechanism. The study was carried out using GRI 3.0, Okafor, and Konnov 0.5, which includes the combustion reaction of methane, as the variables used were equivalence ratio and inlet temperature. As a result, it was confirmed that Konnov 0.5 generates less NOx compared to GRI 3.0 and Okafor. Upon analyzing the reaction contribution, it became apparent that the hydrocarbon chain and chain‐branching reaction and the third‐body efficiency coefficient contribute to Konnov 0.5’s NOx generation. The results in one and two dimensions showed similar trends. It is expected that similar results will be obtained for higher‐dimensional systems with complex physical phenomena.