Potentials and challenges of hydrogen combustion system development as a sustainable fuel for commercial vehicles

One challenge for commercial vehicle development is reduction of the CO2 greenhouse gas, as a part of the transportation sector is. A trend of strong CO2 reduction is visible for EU, USA which cannot be fulfilled by only vehicle and engine optimization. Hydrogen fuel, which can be produced from biomass or renewable power like solar and wind is regarded as one of the key energy solutions for CO2 reduction in the future transportation.Hydrogen can be used in fuel cells or directly in internal combustion engines. The focus of this paper is the usage of hydrogen for heavy duty commercial vehicle combustion engine. Starting with an emission regulation roadmap and scenarios for future heavy duty engines until 2031, the requirements on combustion system and NOx reduction are defined.The major advantages regarded to hydrogen combustion are due to the wide range of flammability and very high flame speed numbers compared to fossil based fuels. Thus, it can be well used for lean burn combustion with much better fuel efficiency and very low NOx emissions. Potential of lean-burn hydrogen combustion for NOx reduction will be shown using heavy duty 2 L single-cylinder testing at multiple engine speeds and loads.Using numerical simulation, well validated by single cylinder engine measurements the potentials and challenges, as well as requirements on combustion and emissions for HD engines are discussed.The challenges regarding pre-ignition and glow-ignition due to the very low auto ignition delay time of hydrogen at high mixture temperatures and the low ignition energy demand of hydrogen will be discussed and future technologies like direct injection and diffusive combustion are addressed.The effects of a lean hydrogen combustion, i.e. lower exhaust gas temperature and their impact on exhaust gas after-treatment system to fulfill future regulations are discussed. Furthermore, measurements of exhaust gas particulate matter emissions with variation of air-fuel ratio are shown and discussed.Finally, recommendations on hydrogen combustion system for heavy duty commercial vehicle applications are given as an outlook.