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Study on using hydrogen and ammonia as fuels: Combustion characteristics and NOx formation

This paper evaluates the potential of hydrogen (H2) and ammonia (NH3) as carbon‐free fuels. The combustion characteristics and NOx formation in the combustion of H2 and NH3 at different air‐fuel equivalence ratios and initial H2 concentrations in the fuel gas were experimentally studied. NH3 burning velocity improved because of increased amounts of H2 atom in flame with the addition of H2. NH3 burning velocity could be moderately improved and could be applied to the commercial gas engine together with H2 as fuels. H2 has an accelerant role in H2–NH3–air combustion, whereas NH3 has a major effect on the maximum burning velocity of H2–NH3–air. In addition, fuel‐NOx has a dominant role and thermal‐NOx has a negligible role in H2–NH3–air combustion. Thermal‐NOx decreases in H2–NH3–air combustion compared with pure H2–air combustion. NOx concentration reaches its maximum at stoichiometric combustion. Furthermore, H2 is detected at an air‐fuel equivalence ratio of 1.00 for the decomposition of NH3 in flame. Hence, the stoichiometric combustion of H2 and NH3 should be carefully considered in the practical utilization of H2 and NH3 as fuels. H2 as fuel for improving burning performance with moderate burning velocity and NOx emission enables the utilization of H2 and NH3 as promising fuels. Copyright © 2014 John Wiley & Sons, Ltd.