Modeling of the Ammonia Substitution Ratio in a Heptane-Fueled Internal Combustion Engine

Articles in Press

Document Type : Research Paper

Authors
Samuel Molima 1 , 2
Fathi Hamdi 1
Takwa Hamdi 1
Mouldi Chrigui 1
1 Laboratory for Mechanical Modeling, Energy and Materials (LM2EM), Engineering National School of Gabes, The University of Gabes, Omar Ibn El Khattab Street 6029, Gabes, Tunisia
2 Laboratoire de Modélisation Mécanique, Energétique et Matériaux, Institut supérieur des Techniques Appliquées (ISTA-Kinshasa), Avenue Aérodrome N° 3930, Commune de Barumbu, Kinshasa BP 6593, Democratic Republic of the Congo
10.22055/jacm.2026.48727.5456
Abstract
Ammonia is a carbon-free, low-emission fuel with high potential for sustainable RCCI engines. This study investigates ammonia–heptane dual-fuel combustion using a hybrid G-equation with detailed chemical kinetics and CFD-based turbulence–chemistry modeling. Increasing ammonia substitution ratio (ASR) reduces peak in-cylinder pressure (up to ~10% at 40% ASR) and heat release rate due to its low reactivity and high ignition energy, while increasing droplet size, vapor penetration, and wall-film formation. At 40% ASR, start-of-injection (SOI) strongly affects emissions: retarded injection (14–16° BTDC) minimizes NOx (1.73 g/kWh, ~15% lower than 18° BTDC) and CO (1.47 g/kWh, ~70% lower than advanced SOI) but slightly increases unburned hydrocarbons (1.73 g/kWh, ~20% higher), whereas advanced injection (22–24° BTDC) improves UHC conversion but sharply increases CO (~5 g/kWh, +240%) and NOx (3.23 g/kWh, +85%). Pareto-based analysis identifies 16–18° BTDC as the optimal SOI window, balancing fuel efficiency and emissions. These findings provide quantitative guidance for low-carbon RCCI engine optimization.
Keywords
Ammonia/heptane
IC engine
CFD
Low-carbon-fuels
Detailed reaction mechanism
Spray
Subjects

Publisher’s Note Shahid Chamran University of Ahvaz remains neutral with regard to jurisdictional claims in published maps and institutional affiliations

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Available Online from 14 April 2026