Advancements of combustion technologies in the ammonia-fuelled engines

Abstract

The worldwide decarbonisation movement has turned ammonia into one of the attractive alternative fuel for power generation. This paper reviews the progress of ammonia combustion technologies in spark ignition engine, compression ignition engine, and gas turbine. Relevant publications from prominent academic journals were acquired from credible scholarly databases and analysed. Ammonia dissociation and separate hydrogen supply were typically employed to deliver hydrogen to enhance ammonia reaction in the spark ignition engine. To achieve satisfactory engine performances with thermal efficiency of around 30%, a hydrogen mass fraction of roughly 10% is required for the ammonia/hydrogen engine. Engine parameters optimisation may be needed to increase hydrogen mass fraction further. Aqueous ammonia elevates heat release rate of full load compression ignition engine by almost 10%. However, prolonged ignition delay could potentially lead to higher engine noise levels. Multiple fuel injection optimisation is seemingly a more promising solution for improving ammonia compression ignition engine performances. In recent years, partial premixed combustion has gained considerable interest in hydrogen/ammonia gas turbine combustion research. This is mainly due to its ability to operate at equivalence ratio as low as 0.4, and in the slight fuel-rich regime. For operation at equivalence ratio 1.05, the nitric oxide concentration was decreased by a factor of approximately 5.9 when compared with that of stoichiometric condition. In all, ammonia offers a practical opportunity for sustainable power generation via internal combustion engines and gas turbine. Ground-breaking combustion technologies are crucial to boost the adoption of ammonia in these engines.