High-pressure Spray and Combustion Characteristics of Ammonia Jets under Diesel-Like Conditions

As a zero-carbon fuel, ammonia is drawing more and more attention for application in marine power plants. High-pressure direct-injection of ammonia can be considered to be a promising way for marine engines. In this study, the spray and combustion characteristics of ammonia jets are studied under diesel-like conditions in a high-pressure high-temperature constant-volume combustion chamber (CVCC) with comparison to diesel jets. The spray tip penetration, cone angle, maximum liquid length and lift-off length are obtained by the high-speed Schlieren and Diffused back-illumination imaging techniques. The ammonia jet’s combustion intensity and heat release rate are evaluated by the capturing image and the pressure trace. The effects of the ambient temperature (800 ~ 1000 K), ambient density (15 ~ 21 kg/m3) and ambient oxygen concentration (0 ~ 21%) on the evaporating and burning ammonia jets are investigated. The results show that the maximum liquid length in the ammonia jets is negatively correlated with the ambient density and ambient temperature. Under the ambient temperatures of 900 and 1000 K temperatures with 21%vol. oxygen, the ammonia diffusion jet flame is successfully observed. The macroscopic structure of the ammonia jet is quite similar to that of diesel, however, the significantly transparent-like flame texture with lower combustion intensity is observed for the ammonia diffusion jet.