Abstract
Ammonia has emerged as a promising carbon-free energy carrier, yet its combustion poses significant challenges due to its low burning rate and emissions of
and N2O. Previous studies have shown that Rich-Dilute-Lean (RDL) combustor layouts can effectively mitigate these issues. However, implementing fuel-rich primary combustion during part-load operation poses a practical challenge, as the requirement of lower flame temperatures compared to full-load operation necessarily imply reduced fuel-to-oxidizer ratios. This work builds upon an earlier concept study solely based on numerical simulations, which proposed a novel azimuthal fuel-staging strategy using optimized multi-burner grouping to minimize emissions during part-load operation while still maintaining the desired thermal power.
Here, the concept is validated through precise emissions measurements in a laboratory-scale multi-burner premixed combustor. High-resolution Large-Eddy Simulations (LES) of the same configuration provide crucial insight into the physical processes that control flame stabilization, combustion efficiency and emissions formation. Two part-load strategies are compared: (1) uniform reduction of the equivalence ratio across all burners, and (2) selective burner deactivation to locally preserve fuel-rich conditions at the active-burner level. The present results confirm that optimizing burner placement and grouping — by combining switched-off and fuel-rich burners — significantly reduces emissions during part-load operation. Beyond the challenge of part-load operation, the proposed fuel-staging strategy, once refined on a combustor-specific basis for ammonia-based fuels, offers a promising pathway to enhance fuel flexibility of annular combustion systems in which the implementation of axial air staging for RDL operation is impractical.
Novelty and Significance Statement A novel azimuthal fuel-staging strategy for ammonia-fired gas turbines is introduced and experimentally validated at laboratory scale, with high-resolution numerical simulations providing complementary insights. The concept addresses the presently unsolved challenge of achieving low-emission performance during part-load operation in Rich-Dilute-Lean (RDL) combustion systems, which rely on fuel-rich primary combustion under full-load operation. For the first time, experimental evidence confirms earlier findings, only based on numerical simulations of an industrial-scale combustor, demonstrating that the proposed azimuthal fuel-staging approach can substantially reduce emissions across the full gas-turbine load range. The present validation illustrates that the proposed fuel-staging concept represents a viable solution for controlling emissions in industrial applications. Moreover, the proposed strategy offers a promising route to enhance fuel flexibility in other types of combustion systems — such as compact annular combustors — where axial air staging is impractical.