Effect of ammonia energy ratio and load on combustion and emissions of an ammonia/diesel dual-fuel engine.

Ammonia is receiving increasing attention as a zero-carbon fuel. However, it is difficult to use alone because of its high auto-ignition temperature. Therefore, in this paper, the effects of four ammonia energy ratios (15 %, 30 %, 45 %, and 60 %) on the combustion and emission characteristics of the engine at different loads were studied by using the ammonia/diesel dual-fuel strategy. The results indicated that the presence of ammonia lowered the combustion temperature at all loads, thereby lowering the cylinder temperature and cylinder pressure. In addition, the HRR first increased and then decreased as the ignition delay increased with the increase in ammonia energy ratio. In terms of emissions, at 100 % load, the CO 2 and NO of the D40A60 were 65.5 % and 88.14 % lower than that of the D100. The decrease in CO 2 was due to more carbon-based fuels being replaced by ammonia. The decrease in NO was due to the decomposition of NO by the thermal deNO x reaction resulting from the lower combustion temperature. The emissions of N 2 O produced by partial ammonia oxidation offset the greenhouse gas emission reduction effect caused by the reduction of carbon dioxide emissions. Further optimization of the engine combustion strategy is still needed in the future. • The combustion characteristics of engines with different AERs at different loads are investigated. • The effect of different AERs on various emissions is presented. • An increase in AER is observed to increase N 2 O and GHG emissions. • Increasing the engine load can improve the emissions of unburned ammonia. [ABSTRACT FROM AUTHOR]