Dependence of dispersion of low-expansion foam on the position in the foam layer by height

This paper presents a comprehensive analysis of structural models for low-expansion foams used in fire suppression systems. The cellular model, which occupies an intermediate position between spherical and polyhedral structures, was selected as the most adequate one, closely approximating real foams. The primary research objective was to establish the dependence of the average foam bubble diameter on the position within the foam layer by height. This relationship is crucial for understanding foam breakdown mechanisms and predicting its operational performance. To facilitate the comparison of polydisperse foams produced by different methods, a new classification of foams by dispersion composition was introduced, utilizing the concepts of minimum and maximum bubble diameters. A semi-empirical model for low-expansion foams was developed, incorporating the calculation of the volumetric flow rate of liquid through the Plateau-Gibbs channels (capillaries) under steady-state flow conditions, as well as key foam characteristics such as expansion ratio and stability. Experimental studies using the “Sintek-6NS” foaming agent were conducted to verify the theoretical dependence, revealing a clear stratification of the foam column into zones with varying dispersion and bubble shapes. The obtained experimental dependence for average foam bubble diameter shows good agreement with the equation proposed by the authors.

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