Study on effects of mixing characteristics on the hydrogen-containing micro-mixing combustion using a modified LES-FGM model

Abstract

Mixing uniformity and combustion performance of a model Micromix burner were studied using the Large eddy simulation (LES) and modified Flamelet Generated Manifold (FGM) model. This model considered hydrogen preferential diffusion and used separate transport equations to compute NO formation, which significantly improved the prediction accuracy of flame structure and NO production for high-hydrogen micro-mixing jet flames. The result shows that, with changes in mixing uniformity, the difference in Damköhler numbers becomes noticeable as the reaction distance increases. It is most pronounced when the mixing quality increases above 90%, which leads to the abrupt change of the overall flame temperature and NO generation. Thus, there is an inflection point in the inhibition of NO production by mixing uniformity. Moreover, while the adiabatic flame temperature changes, the improved mixing quality can mitigate the flame temperature variations caused by changes in the equivalence ratio, further reducing the maximum NO production.