Experimental study on mass loss mechanism and cooling effect of compressed air foam on fuel surface at different temperatures

Abstract

Compressed air foam (CAF) is widely used as a high-performance extinguishing agent for liquid fuel fire. In this work, the effects of initial fuel surface temperatures (50–80 °C) on the drainage and evaporation of CAF were studied experimentally. It was found that at the same foam mass, the drain rate is positively correlated to the initial fuel surface temperature. Furthermore, the drainage and evaporation with ER = 5.5 is less affected by the fuel surface temperature than ER = 10. Then the foam height was recorded and it was observed when the temperature is above 60 °C, the foam height with ER = 10 reduces rapidly at the beginning, while only slight thermal expansion occurs in ER = 5.5. In addition, the cooling effect of the foam was studied. The fuel layer temperature variation could be divided into three stages: rapid decline, relatively stable and gradual rise, which may relate to the foam drainage. But in the rapid decline state, the drop in fuel temperature is mainly related to the heat transfer between the fuel and foam. In addition, for the foam with ER = 10, the rising stage starts earlier. This work improves the understanding of mass loss and suppression mechanisms of fire-extinguishing foams.

Keywords

• Compressed air foam
• Firefighting foam
• Drainage
• Evaporation
• Mass loss mechanism
• Cooling effect