Abstract: The effects of polymer addition on the rheological properties of compressed air foam and the pressure drop characteristics of foam flow in horizontal pipeline were investigated. The results show that the viscosity of the foaming solution changes significantly with polymer type and concentration. At the same polymer concentration, the non-Newtonian behavior of the Xanthan Gum (XG)-based foaming solution is more pronounced than that of the sodium Carboxymethyl Cellulose (CMC)-based one, which is attributed to stronger molecular interactions within the XG chains. Furthermore, both the type and concentration of the polymer substantially influence the rheological properties of the foam. As the polymer concentration increases, the consistency coefficient of the foam increases, while its flow behavior index decreases. Based on the rheological experimental results, a pressure drop prediction model for annular foam flow of compressed air foam was developed by incorporating the friction factor between the foam and the pipe wall, as well as the entrainment effects of the gas core and the foam layer on the fluid. The errors between the pressure drop values predicted by the proposed theoretical model and the corresponding experimental data are within 25%, indicating that the model exhibits satisfactory predictive performance.

Key words: compressed air foam, non-Newtonian fluids, annular foam flow, pressure drop