A Comprehensive Overview of Hydrogen-Fueled Internal Combustion Engines: Achievements and Future Challenges

This paper provides a comprehensive review and critical analysis of the latest research results in addition to an overview of the future challenges and opportunities regarding the use of hydrogen to power internal combustion engines (ICEs). The experiences and opinions of various international research centers on the technical possibilities of using hydrogen as a fuel in ICE are summarized. The advantages and disadvantages of the use of hydrogen as a solution are described. Attention is drawn to the specific physical, chemical, and operational properties of hydrogen for ICEs. A critical review of hydrogen combustion concepts is provided, drawing on previous research results and experiences described in a number of research papers. Much space is devoted to discussing the challenges and opportunities associated with port and direct hydrogen injection technology. A comparison of different fuel injection and ignition strategies and the benefits of using the synergies of selected solutions are presented. Pointing to the previous experiences of various research centers, the hazards related to incorrect hydrogen combustion, such as early pre-ignition, late pre-ignition, knocking combustion, and backfire, are described. Attention is focused on the fundamental importance of air ratio optimization from the point of view of combustion quality, NOx emissions, engine efficiency, and performance. Exhaust gas scrubbing to meet future emission regulations for hydrogen powered internal combustion engines is another issue that is considered. The article also discusses the modifications required to adapt existing engines to run on hydrogen. Referring to still-unsolved problems, the reliability challenges faced by fuel injection systems, in particular, are presented. An analysis of more than 150 articles shows that hydrogen is a suitable alternative fuel for spark-ignition engines. It will significantly improve their performance and greatly reduce emissions to a fraction of their current level. However, its use also has some drawbacks, the most significant of which are its high NOx emissions and low power output, and problems in terms of the durability and reliability of hydrogen-fueled engines.