Towards sustainable hydrogen and ammonia internal combustion engines: Challenges and opportunities

This review explores the required hardware changes and effects of incorporating hydrogen and ammonia on performance, combustion, and emissions of internal combustion engines (ICEs). Though hydrogen combustion is environmental-friendly, it burns much faster than conventional fuels, like gasoline or diesel, leading to challenges in controlling combustion and ignition timing, potentially causing engine knocking or misfiring. Ammonia is less combustible compared to hydrogen and traditional fuels, requiring specialized engine adjustments or dedicated combustion systems for effective use in ICEs. Like hydrogen, ammonia combustion results in minimal carbon emissions but might generate nitrogen oxides (NOx) emissions, necessitating additional after treatment for emission control. Adapting an ICE to utilize hydrogen or ammonia as a fuel necessitates significant modifications to enhance efficiency, manage combustion characteristics, and control emissions. By innovating safety techniques for handling hydrogen and ammonia with more reliable infrastructure, these fuels could potentially become viable energy sources soon.