Abstract
Direct numerical simulation of methane-air turbulent plane jet premixed flame have been conducted by considering detailed kinetic mechanism and temperature dependence of thermal and transport properties. In this study, we focus on relation between local flame structures and production mechanisms of NO, especially prompt NO, in turbulent shear flow. In the turbulent plane jet premixed flame, unburnt mixture islands are frequently discharged from the main flame. It is clarified that generation of unburnt mixture islands locally enhances production of prompt NO near the disconnection region of the flame surface. The production mechanisms of prompt NO are investigated in terms of reaction rate of elementary reactions and concentrations of major species. In the generation process of unburnt mixture islands, the state of almost incomplete combustion is formed and it results in increase of CO concentration. As a result, production of H and NNH is promoted. Consequently, prompt NO is increased by the elementary reaction related with H and NNH during the disconnection process of the flame surface.
