Nitro-compounds and GHG exhaust emissions of a pilot diesel-ignited ammonia dual-fuel engine under various operating conditions

TL;DR

This study evaluates emissions from a pilot ammonia-diesel dual-fuel engine under various conditions, focusing on nitro-compounds and GHGs, revealing how operating parameters influence emissions and potential strategies for emission reduction.

Contribution

It provides new insights into the emissions correlations of ammonia-diesel dual-fuel engines, especially regarding nitro-compounds and N2O, under different operating conditions.

Findings

Unburned NH3 increases with ammonia content but decreases with load and speed.

N2O emissions significantly weaken GHG reduction efforts.

Advanced injection timing reduces NH3 and N2O emissions, especially at higher AERs.

Abstract

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.