Study of the chemical effect of steam dilution on NO formation in laminar premixed H2/Air flame at normal and elevated pressure

To promote the understanding and development of the steam diluted H-2/air combustion technology, the chemical effect of steam dilution on NO formation in 1D laminar premixed H-2/air flame is numerically studied over a wide range of conditions. The importance and the influence path of the chemical effect of steam dilution are analyzed, and the impact of working conditions is explored. This research makes up for the deficiencies in understanding the chemical effect of steam dilution, and has significant reference value for optimizing working conditions in practical application. Results show that the importance of steam dilution's chemical effect on NO formation highly depends on the dilution rate and pressure. In this study, the chemical effect of steam accounts for -16.3%-20.1% of the total NO reduced by steam dilution. The direct chemical effect of steam is the main cause of NO change. It reduces the H and O concentration by inhibiting the reaction OH + H-2 < = > H + H2O and H + O-2 < = > OH + O. However, the third-body effect of steam increases the O concentration and then slightly promotes NO formation. Increasing pressure causes the direct chemical effect to gradually turns to promote the NO generation at low dilution rates. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.