Particle emissions from internal combustion engines utilizing hydrogen and hydrogen-enriched fuels

This article offers a comprehensive review of research on particle emissions from internal combustion engines fueled with hydrogen and hydrogen enriched fuels. It briefly discusses the health and environmental hazards of combustion-generated particles and covers fundamental issues of particle formation in engine combustion, along with their characterization and measurement methods. Combustion-related properties of hydrogen and hydrogen-enriched fuels are discussed and analyzed in view of their impact on the combustion process and particle formation. A detailed analysis of particle emissions from dual-fuel engines operated with hydrogen addition, as well as from dedicated engines fueled with hydrogen or hydrogen-rich reformate is provided. The analysis covers the effects of engine type, primary fuel type, hydrogen injection method, and ambient conditions on particle formation and emission. This review shows that a significant body of diverse research activities is being conducted in the field. However, several issues still need to be addressed. An attempt to list some of the open questions is made.