Development of a Spark-Ignited Combustion Strategy for 100% Ammonia (NH 3 ) Operation in Internal Combustion Engines

Annalena Braun (), Moritz Grüninger, Daniel Bäck, Tomas Carlsson, Jakob Ängeby, Olaf Toedter and Thomas Koch
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Annalena Braun: Intitute of Internal Combustion Engines (IFKM), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
Moritz Grüninger: Intitute of Internal Combustion Engines (IFKM), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
Daniel Bäck: SEM AB, 662 34 Åmål, Sweden
Tomas Carlsson: SEM AB, 662 34 Åmål, Sweden
Jakob Ängeby: SEM AB, 662 34 Åmål, Sweden
Olaf Toedter: Intitute of Internal Combustion Engines (IFKM), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
Thomas Koch: Intitute of Internal Combustion Engines (IFKM), Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany

Energies, 2025, vol. 18, issue 19, 1-14

Abstract: Ammonia (NH 3 ) is a promising carbon-free fuel for internal combustion engines, but its low reactivity and poor ignition properties present significant challenges for stable operation. This study presents the development and experimental validation of a spark-ignited combustion process that enables stable engine operation using 100% liquid NH 3 as a single fuel. A modified single cylinder research engine, equipped with NH 3 port fuel injection and a high-energy capacitive ignition system was used to investigate combustion behavior under various load conditions. The results show that stable, knock-free combustion with pure NH 3 is feasible at every operating point without any ignition aids like diesel fuel or hydrogen (H 2 ). The full load conditions of a diesel engine can be represented with an indicated efficiency of 50% using this combustion process. The emission measurements show nitrogen oxides (NO x ) and NH 3 emissions in a 1:1 ratio, which is advantageous for a passive SCR system. Increased nitrous oxides (N 2 O) formation occurs at low loads and cold combustion chamber temperatures. This work demonstrates the technical viability of carbon-free NH 3 combustion in spark-ignited (SI) engines and represents a promising step towards net-zero combustion.

Keywords: internal combustion engines; ammonia (NH 3 ); spark-ignited; carbon-free fuel; ignition strategies; maritime propulsion system (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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