Effect of H2O dilution on NOx emissions from the oxidation of NH3/H2 fuel mixture

Abstract

During NH/H combustion, reactant jets entrain the burnt gas, resulting in a combustion zone diluted with HO. Therefore, the effect of HO dilution on NO formation should be carefully examined. In this study, NH/H oxidation with N and HO dilutions was investigated in a jet-stirred reactor (JSR). A systematic experimental analysis was conducted to investigate the effects of different factors, including temperature (), equivalence ratio (Φ), and HO volume fraction (). A numerical simulation was conducted using a modified mechanism to interpret the measured results and examine the kinetic pathways. NO formation is enhanced as increases but inhibited as Φ increases The effect of HO dilution on NO formation is related to and Φ. Under fuel-lean conditions, NO generation is hindered by HO dilution. NO formation is reduced by 43 % at = 1375 K and Φ = 0.5. In contrast, under fuel-rich conditions (Φ > 1), HO dilution promotes NO formation at high temperatures (e.g., > 1300 K at Φ = 2.5) The NO concentration peaks at approximately 1250 K in cases of N dilution, and 25 % HO dilution increases the of the peak NO concentration by approximately 100 K. At 1375 K, the promoting effect of HO on NO generation is significant at = 10 %. This study provides new insights into the effect of HO dilution on NO formation characteristics during NH/H oxidation.