: Ammonia is attracting attention not only as a carbon-free fuel but also as a hydrogen career. Using ammonia as an alternative to hydrocarbon fuels could significantly mitigate global warming. Furthermore, the world\\\'s demand for miniaturized products leads to the high importance of micro-scale devices such as micro combustor, which is an effective alternative to traditional batteries. In the current study, 2D planar numerical simulations have been done to investigate ammonia flame dynamics with hydrogen addition and NOx emission in a micro-scale combustor. Therefore, the effect of inlet flow velocity, hydrogen fraction, and equivalence ratio on the map of flame dynamics and combustion characteristics are studied. The physical model is a 2D planar channel with 10 mm length and 1 mm height. The wall temperature is defined as a constant temperature at 1260 K to provide a similar condition to the previous experimental work of ammonia combustion in a microtube [1], and this condition is a typical condition for flame dynamics investigation [2]. This model is validated by previous work [3]. It has been found that by changing the equivalence ratio from lean condition to rich condition, not only does the ammonia fraction of the fuel increase, but also NO emission significantly decreases. However, a lean condition has been suggested for hydrogen and hydrocarbon combustion to decrease emissions. In terms of flame dynamics of ammonia/hydrogen mixture, three types of flame are generally observed, including ignition-extinction mode, close symmetric, and open symmetric flame. While the open symmetric flame is obtained in lean conditions in high inlet flow velocities, closed symmetric flames are seen in stoichiometric and rich conditions. Furthermore, in stoichiometry and rich conditions, 70% of the fuel includes ammonia, the other 30% is hydrogen, while only 40% of the fuel is ammonia when a lean condition is employed.

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