Experimental and CFD Investigation of the Spreading Dynamics and Fire Suppression Performance of Three Fire-Fighting Foams on Burning Fuel Surfaces

Oil-pool fires involving liquid hydrocarbons are difficult to suppress and pose substantial economic risks. This study characterizes three widely used Class B fire suppressants through physical property measurements, cold oil-surface spreading tests, and burning oil-pool fire experiments, coupled with transient computational fluid dynamics (CFD) simulations in ANSYS Fluent. The results show that 3% aqueous film-forming foam (3% AFFF) and 3% alcohol-resistant aqueous film-forming foam (3% AFFF-AR) spread spontaneously on oil surfaces, whereas 3% fluoroprotein foam (3% FP) has a negative spreading coefficient and covers oil surfaces only through gravitational accumulation. Although 3% AFFF exhibits the fastest cold-state spreading, 3% AFFF-AR achieves the shortest fire-extinguishing time under combustion conditions because of its superior thermal stability and longer drainage time. In contrast, 3% FP shows the poorest fire-extinguishing performance. The CFD simulations capture the main temporal evolution of foam spreading and agree reasonably with experimental observations, particularly in the temporal consistency between simulated foam front propagation under the simplified elevated-temperature boundary condition and measured extinguishment times. Within the scope of the present simplified model and small-scale experiments, the results suggest that a positive spreading coefficient serves as a necessary but insufficient thermodynamic condition for effective foam spreading. Under high-temperature conditions, foam thermal stability critically influences the sustainability of spreading by resisting thermal degradation and bubble rupture, while drainage behavior and spreading kinetics modulate the coverage rate; collectively, these factors determine the overall fire suppression effectiveness under the tested conditions. These findings provide preliminary support for optimizing firefighting foam performance, pending validation under larger-scale and more fully resolved combustion scenarios.