Controlling low-carbon fire suppression: The dual regime of air vortex ring

Fire carbon emissions are a major contributor to global warming and threaten the sustainability of energy systems. This study introduces the air vortex ring as a low-carbon, energy-efficient fire suppression agent. Results show that a single vortex ring with as little as 1 J of kinetic energy can prevent over 100 g of fire carbon emissions, achieving effective extinction remotely at up to 3 m. By combining optical measurement and theoretical analysis, a critical transition in the dominant extinction mechanism is revealed. At short propagation distances, extinction is governed by a blow-off regime driven by vortex translational momentum. At longer distances, the mechanism shifts decisively to a fuel-dilution regime, where the vortex core entrains and dilutes fuel-air mixture below the flammable limit. A consolidated theoretical framework is developed to quantify this transition, where the Froude number (Fr) is established as a key indicator and enables the construction of an operational diagram that clearly demarcates blow-off, transition, and fuel-dilution conditions. This work provides a fundamental understanding of vortex-induced extinction, and it offers a practical, science-based framework for designing next-generation, sustainable firefighting systems.