With the introduction of Chinese goals of “carbon peak” and “carbon neutrality”, the low-carbon and zero-carbon transition of internal combustion engines is imperative. Ammonia, as a zero-carbon fuel and a high-energy-density carrier for hydrogen, is a promising alternative fuel for achieving carbon neutrality in the near to mid-term. Developing ammonia-hydrogen combustion technology for high-power, zero-carbon internal combustion engines is of significant importance for global climate governance. This paper analyzes the potential of ammonia as a future green energy source and its practical applications in internal combustion engines. It reviews the latest advancements in ammonia-hydrogen engine combustion from the aspects of combustion modes, reaction kinetics of ammonia-hydrogen fuel, and fuel supply methods, comparing three combustion modes (spark ignition/homogeneous compression ignition/jet ignition), two ammonia supply methods (gaseous port injection/liquid ammonia direct injection), and two jet ignition methods (active/passive). A promising technology of ammonia-hydrogen synergy combustion based on online ammonia cracking to produce hydrogen from a single liquid ammonia fuel tank is proposed and discussed. Key technical and scientific issues to be addressed in spray, combustion, and nitrogen-based emission control are also pointed out. Research indicates that using a small amount of hydrogen (less than 3%) to ignite ammonia-air mixtures in ammonia-hydrogen engines can achieve stable combustion and high thermal efficiency while extending the lean limit. Ammonia-hydrogen synergy zero-carbon high-power internal combustion engines, as efficient and reliable application carriers for ammonia fuel, have broad application potential and value in heavy-duty vehicles, construction machinery, ocean-going vessels, and power generation. The development of ammonia-hydrogen engines can advance fundamental combustion theory and revitalize China's internal combustion engine industry.
