A quantitative study on the combustion and emission characteristics of an Ammonia-Diesel Dual-fuel (ADDF) engine

In order to resolve the global warming problem, Ammonia-Diesel Dual-Fuel (ADDF) combustion has been a feasible strategy for burning ammonia to reduce carbon emissions from internal combustion engines. In the research of this paper, an ADDF engine experimental platform was developed and established. Premixed-Charge Compression Ignition (PCCI) combustion and diesel-piloted combustion modes under different operating conditions were investigated to achieve the goals of high thermal efficiency and low emissions. Moreover, the influence of diesel injection strategy and intake pressure on combustion, gaseous and particle emissions were explored. The results indicate that high thermal efficiency can be obtained using PCCI mode with early injected diesel, which forms a homogeneous mixture with ammonia under the low load condition. Under medium and high load conditions, less diesel was injected early, and ignition was delivered by a pilot injection of diesel close to the top dead centre. Under all operating conditions, the gross indicated thermal efficiency (ITEg) exceeded 48%, and the maximum ITEg was 51.5%, which was comparable to the diesel-only mode. Meantime, the emission of ammonia, NO and N2O were normally below 6 g/kWh, 7 g/kWh, and 1 g/kWh, respectively. With increasing ammonia energy substitution ratio, the particle emission changed from accumulation-mode particles to nucleation-mode particles, but the mass of accumulation-mode particles dominated. •As the load increased, the optimal combustion mode changed from PPCI mode to diesel-pilot mode.•The gross indicated thermal efficiency under different operating conditions exceeded 48%.•Nitrogen-containing emissions were controlled at a low level.•With increasing RAE, the particle emission changed from accumulation-mode particles to nucleation-mode particles.