A Numerical Assessment of Ammonia-Based Fuel Blends for Low-Emission Combustion in a Micro-Gas Turbine

Ammonia is increasingly considered a potential carbon-free energy carrier for power generation applications, although its use in micro-gas turbines remains challenging because of its low reactivity, low flame speed, flame stability limitations, and nitrogen-containing emissions. This study develops an integrated framework combining chemical kinetic modelling, Python 3.11-based emission screening, sensitivity analysis, 3D CFD modelling, and carbon footprint assessment for ammonia, hydrogen, methane, and selected dual-fuel blends. Under the investigated conditions, hydrogen was associated with the highest flame temperatures and the greatest NO formation, whereas ammonia exhibited lower combustion temperatures while promoting reaction pathways involving fuel-bound nitrogen. The sensitivity analysis highlighted the relevance of HNO- and NH-related pathways in H2/NH3 combustion systems. Among the investigated blends, the 80% H2/20% NH3 case showed a comparatively favourable balance with respect to nitrogen oxide emissions. For the 100% NH3 case, the predicted ammonia slip remained low at low-load conditions but increased substantially at the highest NH3 flow rate, indicating incomplete fuel conversion under the most demanding operating conditions. The results also suggest that methane-rich blends may represent transitional fuel options under the considered operating conditions. Furthermore, under the assumptions adopted in the carbon footprint assessment, green hydrogen and green ammonia pathways were associated with lower estimated climate impacts than methane and grey ammonia. Overall, the findings indicate the potential of ammonia, particularly in combination with hydrogen, for micro-gas turbine applications under the conditions investigated, although further numerical and experimental verification is required.