Ammonia burning in premixed and diffusive modes in marine engine-like conditions.

Ammonia is emerging as a promising alternative marine fuel due to its carbon-free nature and established production infrastructure. However, its use in marine engines presents challenges related to toxicity, combustion characteristics, and engine adaptation. This study investigates ammonia combustion under marine engine-like conditions using an optically accessible high-temperature pressurized chamber equipped with dual injectors for ammonia and diesel. Experimental tests examined both premixed and diffusive combustion modes, analyzing pressure dynamics and flame behavior through optical diagnostics and thermodynamic measurements. Results indicate that in near-stoichiometric premixed conditions, ammonia combustion is complete and efficient if diesel pilot injection energy exceeds 4.4% of the total energy. In diffusive mode, ammonia ignition is hindered by temperature drops due to its evaporation, requiring optimized diesel injection strategies. These findings contribute to advancing ammonia utilization in marine engines, addressing combustion stability and efficiency.