Improvement of the prediction accuracy of NO emissions in counter-flow diffusion flames on using NO mass fraction as a progress variable

Computational fluid dynamics has been widely used to predict the production of nitrogen oxide (NO). Flamelet approach is commonly used as a modelling technique to perform turbulent combustion simulations. As the prediction of NO emissions with the flamelet approach is not reliable, when predicting the NO emission, the NO emissions are calculated with the conservation equation of NO mass fraction, and the NO production rate is predicted with the flamelet approach. In this study, we used the mixture fraction and NO mass fraction to predict the NO production rate in the conservation equation of the NO mass fraction, comparing the numerical results calculated with proposed method with those with the conventional methods and detailed chemistry model. Numerical simulations of counter-flow diffusion flames where NO was not supplied, that was supplied with fuel, and that was supplied with oxidizer indicated that the distribution of NO mole fraction calculated with the proposed method was in better agreement with that of the detailed chemistry model than that of the conventional methods.