Abstract: Aiming at the critical challenge in handling lithium iron phosphate battery thermal runaway jet fires—where flames are easily controlled but prone to rapid re-ignition—this study conducts comparative experiments using pure water, aqueous film-forming foam(AFFF), fluoroprotein foam, F-500 water-based additive, and three-phase foam. The flame extinction time during the specified spraying process and post-extinction reignition characteristics after cessation of spraying are recorded, while simultaneously analyzing the dynamic responses of flame zone and battery surface temperatures, heat release rate (HRR), and CO2 and CO volume fractions. Results indicate that pure water and AFFF failed to fully extinguish the flames during the spraying phase. Fluoroprotein foam, F-500, and three-phase foam successfully achieved flame extinction, with three-phase foam exhibiting the shortest extinguishing time (7.56 s), followed by F-500 (13.05 s); fluoroprotein foam achieved extinction at the end of spraying but the flame reignited after 13.27 s of pause. Temperature and combustion characteristic analyses reveal that instantaneous cooling intensity during spraying does not fully represent overall fire suppression performance; although all agents reduce thermal feedback, post-extinction reheating rate and other factors determine whether reignition occurs. Based on comprehensive evaluation of combustion intensity, cooling dynamics, and anti-reignition capability, three-phase foam demonstrates superior suppression performance, followed by F-500. This study elucidates the differences in cooling mechanisms and oxygen-blocking anti-reignition behaviors among various water-based fire suppressants under jet flame conditions, confirming that constructing a durable physical barrier can effectively interrupt heat accumulation.

Key words: lithium iron phosphate battery, thermal runaway, water-based fire extinguishing agent, re-ignition suppression