Ammonia–Hydrogen Dual-Fuel Combustion: Strategies for Optimizing Performance and Reducing Emissions in Internal Combustion Engines

Cinzia Tornatore (), Paolo Sementa and Francesco Catapano ()
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Cinzia Tornatore: Institute of Science and Technology for Sustainable Energy and Mobility, CNR (Italian National Research Council), Via Marconi, 4, 80125 Napoli, Italy
Paolo Sementa: Institute of Science and Technology for Sustainable Energy and Mobility, CNR (Italian National Research Council), Via Marconi, 4, 80125 Napoli, Italy
Francesco Catapano: Institute of Science and Technology for Sustainable Energy and Mobility, CNR (Italian National Research Council), Via Marconi, 4, 80125 Napoli, Italy

Energies, 2025, vol. 18, issue 12, 1-26

Abstract: The urgent need to mitigate climate change and reduce greenhouse gas emissions has accelerated the search for sustainable and scalable energy carriers. Among the different alternatives, ammonia stands out as a promising carbon-free fuel, thanks to its high energy density, efficient storage, and compatibility with existing infrastructure. Moreover, it can be produced through sustainable, green processes. However, its application in internal combustion engines is limited by several challenges, including low reactivity, narrow flammability limits, and high ignition energy. These factors can compromise combustion efficiency and contribute to increased unburned ammonia emissions. To address these limitations, hydrogen has emerged as a complementary fuel in dual-fuel configurations with ammonia. Hydrogen’s high reactivity enhances flame stability, ignition characteristics, and combustion efficiency while reducing emissions of unburned ammonia. This review examines the current status of dual-fuel ammonia and hydrogen combustion strategies in internal combustion engines and summarizes the experimental results. It highlights the potential of dual-fuel systems to optimize engine performance and minimize emissions. It identifies key challenges, knowledge gaps, and future research directions to support the development and widespread adoption of ammonia–hydrogen dual-fuel technologies.

Keywords: ammonia; hydrogen; dual-fuel engines (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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