Development and validation of reduced chemical kinetic mechanisms for hydrogen-enriched ammonia/methane premixed combustion

The growing demand for carbon-free energy, driven by the urgent need to reduce greenhouse gas emissions, has intensified interest in ammonia and hydrogen as promising alternative fuels. To facilitate their gradual replacement of conventional hydrocarbons, reliable chemical kinetic mechanisms are essential. In this regard, a reduced mechanism for methane-ammonia-hydrogen blends, comprising 35 species and 233 reactions, was developed and validated against experimental data. Simulations were performed for various equivalence ratios, ammonia and hydrogen fractions, and pressures. Results demonstrate a two-stage temperature response: for x N H 3 <0.525, hydrogen raised flame temperature, but further enrichment caused a slight decline. NO exhibited a maximum at x N H 3 = 0.32 due to the competition between thermal- and fuel-NOx, consistently peaking at ϕ = 0.9 regardless of hydrogen content, while fuel-rich conditions suppressed NO formation. Reaction pathway analysis revealed that NH 3 controlled NO formation through HNO and NH intermediates, with higher hydrogen concentrations reducing the rates of key NO-forming reactions. • A reduced mechanism for CH 4 /NH 3 /H 2 flames developed and verified by experiments. • At x N H 3 = 0.32, NO peak occurs due to competing thermal and fuel NOx formation. • NO Peak occurs at ϕ = 0.9 for all H 2 contents, but fuel-rich mixtures suppress NO. • For x N H 3 <0.525, H 2 enrichment raises flame temperature, but above it drops. • CO formation is negligible and H 2 -insensitive under lean, but rises in fuel-rich.