Effect of steam addition on no formation

Abstract

This study aims at elucidating the effect of steam addition on NO formation. To achieve this purpose, NO concentration profiles in methane-air premixed flames were measured under the condition of constant maximum flame temperature, with various concentrations of added steam. These experimental studies made it clear that the NO concentration is reduced by addition of steam even though the maximum flame temperature is kept constant. Furthermore, it was shown experimentally that the reduction in No formation by steam addition becomes large as the equivalence ratio increases, particularly when the added steam exceeds 10 mol percent. It was also found that the NO concentration increases with an increase of maximum flame temperature, and that the dependence of NO concentration on maximum flame temperature is weakly correlated with the amount of steam added. Furthermore, numerical calculations were conducted to obtain profiles of important species and NO in one-dimensional laminar methane-air premixed flames, corresponding to those used in experimental study. Comparison of these experimental results with the calculated results made it clear that the numerical calculation correctly predicts the measured reduction of the NO concentration when the steam concentration is less than 10 mol percent.