Numerical analysis of nitrogen oxides in turbulent lifted H<inf>2</inf>/N<inf>2</inf> cabra jet flame issuing into a vitiated coflow

Abstract

This paper gives an in-depth insight into NOX (NO, NO2, and N2O)formation of H2/N2 turbulent Cabra jet flame issuing into a hot vitiated coflow. The joint composition probability density function (PDF)was employed to model the combustion and to specify the characteristics of the flame (i.e., scalar variables, concentration of species etc.). The turbulent transport term was modelled by Reynold-Average-Naiver-Stokes (RANS)SSG and molecular mixing was modelled by modified curl model. A combustion mechanism including 13 species and 34 reactions was employed to define the thermochemical state of the flame. The chemical reaction terms were resolved and accelerated by In Situ Adaptive Tabulation (ISAT). The simulation was performed at different equivalence ratios (ER), fuel jet nitrogen content (YN2,C), coflow (TC)and jet temperatures (TJ), coflow oxygen (YO2,C)and water contents (YH2O,C). Results reveal NOX is composed of 30% NO2 and 70% NO in the burner. Reaction rate analysis at different operating points in the ignition kernel demonstrates that N+OH⇌NO+H and NO2+H⇌NO+OH are dominant reactions in NO formation, while NO+HO2⇌NO2+OH is the main reaction in NO2 formation.