Mechanisms for fire suppression with aqueous foams and the role of surfactants

摘要

We developed apparatus, methods, and models to investigate commercially available fluorinated and fluorine-free surfactant formulations, and quantified foam properties, fire suppression mechanisms, and fire extinction performance. We showed that the fluorocarbon (AFFF) and fluorine-free (RF6) formulations caused differences in bubble diameters and liquid drainage rates by using an identical foam generation method. We found significant differences in suppression mechanisms such as the fuel permeability through the foam layer and in foam degradation between fluorocarbon and fluorine-free foams, which are found to affect the measured fire extinction time at large and slow foam application rates respectively. The fire extinction times were significantly higher for the fluorine-free foam than for the fluorinated foam at all foam flow rates, and especially at low flow rates. Reducing bubble diameter reduced fuel permeability, degradation, and extinction time. However, the effects of surfactant properties (oleophobicity and hydrophobicity) on foam properties (bubble diameter, liquid content, lamella thickness), suppression mechanisms, and fire extinction are not well understood and are essential to finding environmentally friendly replacements for fluorocarbon surfactants having high fire suppression efficiency.