Experimental investigation on the spread of aqueous foam over ethanol surface

The presence of ethanol has an adverse effect on foam spreading, and ethanol fire is difficult to extinguish with aqueous fire-fighting foams. Thus, it is necessary to explore the foam formulation suitable for ethanol fuels and study the spreading behavior of foam over ethanol surface. In the current work, stable foams based on hydrocarbon surfactant (SDS), fluorocarbon surfactant (FC1157), and polymers (XG) were prepared by using the compressed-air foam system. The spreading behaviors of foam on polar ethanol and non-polar heptane surface were observed and compared. Furthermore, the effects of stabilizer concentrations, foam flow rates and expansion ratios on foam spreading performance were investigated, respectively. The results indicate that aqueous SDS foam can spread on the heptane layer continuously, but it is difficult to cover the ethanol surface. The addition of XG and FC1157 can synergistically improve the spreading performance of aqueous foam over ethanol. Depending on stabilizer concentrations, there are remarkable differences in foam spreading behaviors. Besides, different foam application parameters including expansion ratios and foam flow rates significantly affect the foam spreading rate, despite the same foam formulation. The research methods and results guide the optimal design of foam formulations as well as the practical application of aqueous foam for ethanol fire extinguishment.