In the transportation sector, ammonia used as a power source plays a
significant role in the scenario of carbon neutralization. However, the
engine-out emissions correlations of ammonia-diesel dual-fuel (DF) engines are
still unclear, especially the nitro-compounds of great concern and GHG. In this
study, the engine-out emissions are evaluated by using a four-cylinder
ammonia/diesel DF engine. Various operating conditions consisting of ammonia
energy ratio (AER), engine load, and speed were carried out. Unburned NH3
increases with raising ammonia content but decreases with increasing engine
load and speed. The NO+NO2 tendency shows a non-linearity trend with increasing
ammonia content, while a trade-off correlation is linked to N2O. The N2O
emission of ammonia engine significantly weakens the beneficial effect of GHG
reduction, the 30% and 50% decarbonization targets need at least 40% and 60%
ammonia energy without regard to N2O effect, while at least 65% and 80% ammonia
energy respectively with considering N2O. N2O presents a parabolic-like
tendency with AERs. Advanced pilot-diesel injection timing helps to reduce both
NH3 and N2O, but this effect becomes insignificant as the AER is less than 0.4.
A combustion strategy of the rapid heat release and ammonia-governed heat
release respectively are revealed