Ammonia is regarded as one of the alternative fuels, since the physical properties of Ammonia is a suitable fuel for transportation and storage as a “hydrogen carrier”. Also, a large amount of ammonia can be produced easily through the Haber-Bosch process with low price. To use ammonia as the alternative fuel, it is necessary to pay attention to Fuel-NOx formation. In this study, the oxygen-enriched combustion was applied to an ammonia/N
2/O
2 premixed flame to make the flame stable. The effects of the oxygen-enriched combustion on characteristics of NOx formation and on the unburned ammonia remained in the burned gas were evaluated. Results showed that NO concentration reached to 1.2%, and unburned ammonia wasn't detected in all O
2 concentration conditions of fuel lean mixture. Also, NO concentrations sharply decreased between
φ = 1.0 to
φ = 1.4. At the condition of
φ = 1.4, NO concentration was 600 ppm. Unburned ammonia wasn't detected between the condition of
φ = 0.9 to
φ = 1.1, and over the condition of
φ =1.2, ammonia concentration was increased steeply. The sum of (NO + NH
3) became the minimum value around the condition of
φ = 1.3 and
φ = 1.4. These characteristics that the NOx formations depended on equivalence ratio were the same characteristics of NOx formation when propane is added to NH
3 as a fuel.
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