Numerical characterization of stratified weakly turbulent hydrogen flames

Abstract

Lean hydrogen combustion offers great potential to reduce greenhouse gas emissions. However, due to its unique combustion characteristics, hydrogen poses significant challenges regarding operational safety of burners and their

emissions. To address these challenges, burner designs must be adapted to ensure the safe and efficient combustion of hydrogen. Previous works indicate that a targeted mixture stratification in the radial direction has the potential of reducing the flashback propensity of hydrogen flames anchored at the sharp edge of a burner outlet. However, the homogeneity of the mixture at the burner outlet also has a significant impact on

emissions of (partially) premixed hydrogen-air flames. Combining both ideas, two burner designs featuring a radial mixture stratification with varying levels of mixture homogeneity in the angular direction at the burner outlet are presented. These designs are analyzed using LES with adaptive mesh refinement for the flame zone and detailed chemistry to evaluate the flame’s stabilization behavior and

emissions in comparison to a reference fully premixed flame. The results of the numerical simulations suggest that the mixture stratification approach is effective for the weakly turbulent flames stabilized on the mesoscale nozzles considered in the present work. Furthermore, the analysis of the

emissions provides useful implications to guide future nozzle design and assessment prior to (additive) manufacturing and experimental investigation.