Numerical Investigation of Engine Performance and Emission Characteristics of an Ammonia/Hydrogen/n-Heptane Engine Under RCCI Operating Conditions

• Published in: Flow, turbulence and combustion Vol. 112; no. 3; pp. 957 - 974
• Main Authors: Xu, Leilei, Bai, Xue-Song
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.03.2024; Springer Nature B.V
• Subjects: Ammonia; Automotive Engineering; Carbon neutrality; Combustion efficiency; Delay time; Diesel engines; Emission analysis; Energiteknik; Energy Engineering; Engineering; Engineering and Technology; Engineering Fluid Dynamics; Engineering Thermodynamics; Flame propagation; Fluid- and Aerodynamics; Heat and Mass Transfer; Heavy-duty engine; Heptanes; Hydrogen; Ignition; Isooctane; Maskinteknik; Mechanical Engineering; Mixtures; Nitrogen Oxides; Numerical models; Octane; Reactivity controlled compression ignition (RCCI); Teknik; Ammonia; Heavy-duty engine; Reactivity controlled compression ignition (RCCI); Carbon neutrality; Nitrogen Oxides
• ISSN: 1386-6184; 1573-1987; 1573-1987
• DOI: 10.1007/s10494-023-00453-y

This paper examines the potential of using ammonia (NH 3 ) as a primary fuel in heavy-duty engines for decarbonization, with some challenges yet to be addressed. It presents a numerical study of a Reactivity Controlled Compression Ignition engine, where pilot diesel is used to ignite the premixed ammonia/air mixture. The numerical model and combustion mechanism are validated against engine experimental results using methanol and iso-octane fuels and ignition delay times of ammonia/n-heptane mixtures measured in a rapid compression machine. The findings show that the engine can effectively operate with up to 50% of the total energy supplied by premixed ammonia, albeit with slightly elevated NO emissions compared to a diesel-fueled engine. Increasing ammonia further leads to lower combustion efficiency. Hydrogen can be utilized in the ammonia engine to enhance ammonia combustion; however, NO emissions increase further. Ammonia leakage primarily originates from regions near the cold wall, the center of the cylinder, and the crevice. N 2 O mainly forms at the ammonia flame front. Emission of N 2 O is therefore mainly due to flame front quenching near the wall.