H2-ICE Technology Options of the Present and the Near Future

At present, the hydrogen combustion engine has gained renewed interest from the heavy-duty internal combustion engine (ICE) industry as an enabler for fast decarbonization of well-to-wheel emissions and reinforced by the vast commitment of key stakeholders to establish a green hydrogen infrastructure. Past studies have often focused on partial substitution of the primary hydrocarbon fuel by hydrogen in spark ignition and compression ignition engines. Studied 100% hydrogen combustion engines are dominantly of the premixed spark ignition type using port fuel hydrogen injection. In this study, a wider look at other hydrogen ICE concepts has been taken that may bear high potential to overcome some of the limitations of using hydrogen for high power applications. The studied concepts vary from port injection to direct injection of hydrogen and from spark ignition to compression ignition. They have been compared based on their proven or expected pros and cons, and more in detail based on their load range and transient response potential. To quantify the comparison of the engine performance potentials, energy balance computations have been performed for all the concepts and additionally in-house measurement data of a port injected hydrogen spark ignition engine has been used. The results show that direct injection technology can improve the load range of a spark ignition hydrogen engine. An option for higher thermal efficiency and faster transient behaviour is to use a compression ignition engine with direct injection of hydrogen at high pressure, however, this may require another fuel to initiate the combustion. Coming studies are subjecting some of these concepts to detailed investigations by experiment and simulation.