Recently, researchers from Large-Engine-Research-Center (LERC) led by Prof. Tie Li from School of Ocean and Civil Engineering published an original scientific paper entitled Ammonia marine engine design for enhanced efficiency and reduced greenhouse gas emissions in Nature Communications. In this work, a concept termed as in-cylinder reforming gas recirculation (IRGR) is initiated to simultaneously improve the thermal efficiency and reduce the unburned NH3, NOx, N2O and greenhouse gas emissions of ammonia combustion engine. The first author is Dr. Xinyi Zhou.
On July 7, 2023, the International Maritime Organization (IMO) proposed the 2050 net-zero GHG target, and the carbon-free ammonia has been deemed as one of the most promising alternative fuels for maritime sector. However, there are still bottleneck problems such as high unburned NH3 and N2O emissions as well as low thermal efficiency that need to be solved before further applications. In this study, a concept termed as in-cylinder reforming gas recirculation (IRGR) is initiated to simultaneously improve the thermal efficiency and reduce the unburned NH3, NOx, N2O and greenhouse gas emissions of ammonia combustion engine. For this concept, one cylinder of the multi-cylinder engine operates rich of stoichiometric and the excess ammonia in the cylinder is partially decomposed into hydrogen, then the exhaust of this dedicated reforming cylinder is recirculated into the other cylinders and therefore the advantages of hydrogen-enriched combustion and exhaust gas recirculation can be combined. The results show that at 3% diesel energetic ratio and 1000 rpm, the engine can increase the indicated thermal efficiency by 15.8% and reduce the unburned NH3 by 89.3%, N2O by 91.2% compared to the base/traditional ammonia engine without the proposed method. At the same time, it is able to reduce the carbon footprint by 97.0% and greenhouse gases by 94.0% compared to the traditional pure diesel mode.
Conceptual model of the in-cylinder reforming gas recirculation (IRGR) for ammonia combustion engine
Effects of IRGR technology under ammonia energetic ratio of 80%, 90% and 97%
Paper Link: https://doi.org/10.1038/s41467-024-46452-z
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