Ammonia is a promising fuel as not only a carbon-free fuel, but also as a hydrogen carrier. Blending ammonia with hydrogen is an effective method to tackle ammonia\\\\\\\'s low flammability problem. However, there is a lack of data regarding ammonia combustion at the microscale. In the present study, two-dimensional numerical simulations were performed to investigate ammonia/hydrogen\\\\\\\'s stable flame region, NOx emission, and combustion efficiency in micro-combustors. For these purposes, the effects of inlet flow velocity and the hydrogen fraction of the fuel on the combustion characteristics and temperature distribution were analyzed. It has been found that a stable flame cannot exist when the inlet velocity is too low relative to the flame speed or too high in accordance with the heating of the wall. Furthermore, a stable flame does not appear when the hydrogen fraction is less than 60% in the fuel. In terms of emission, increasing the inlet flow velocity increases NO emission at every hydrogen fraction of the fuel, and the maximum NO produced increases by approximately 120% when the inlet flow velocity changes from 50 to 200 cm/s. Reduction of the inlet flow velocity is suggested when a higher percentage of ammonia is required in the fuel to recover the loss of combustion efficiency.

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