Roles for combustion in a net-zero CO2 society

This paper considers the role of combustion, and associated future combustion R&D needs, to support the decarbonizing of civilian energy and propulsion sectors. The field has already seen many significant shifts in emphasis over the past decades, due to evolving societal and regulatory drivers, and availability of alternative fuel feed-stocks. For example, regulations on NOx emissions have significantly influenced the focus of the combustion research community. This is clearly evidenced by, for example, the balance of papers on non- premixed relative to premixed combustion in the Combustion Symposium. Similarly, the current trend of decarbonization is driving development of renewable chemical energy carriers and electrification broadly (including hybridization of propulsion systems). This paper also surveys the intersection of combustion technology and research with other societal considerations, including regulatory, environmental justice, geopolitical, and economic drivers. These trends will increasingly motivate combustion problems associated with thermal efficiency, operational flexibility, low particulate and NOx emissions, and fuel flexibility. This paper closes with ideas for future combustion research and development needs directed at the research community, as well as engineering executives and regulatory/certification oversight bodies. General themes include mixing of fuel and air under auto-ignitive conditions, low NOx combustion under high temperature conditions or with ammonia-containing fuels, operational flexibility, high turn-down, and major variations in fuel properties.