Experimental Studies on Water Mist Suppression of Liquid Fires with and without Additives

The purpose of this article is to examine the effect of additives on the extinguishment of liquid pool fires with water mist. Tests are conducted using gasoline, diesel, and ethanol pool fires in a 3.0 × 3.0 × 3.0 m well ventilation compartment. The additives included representative kinds of metal compound, NaHCO3, film-forming agent, AFFF, and a multi-component agent, MC additive. Results showed that the suppression performance varied greatly depending on fuel type, additive type, and concentration. The higher the fire point, the easier it is to extinguish the hydrocarbon liquid pool fires with water mist. But for the polar fuel, small fractal flames existing around the pool edge after the fire is suppressed increased the suppression difficulty. The benefit of adding film-forming additives is observed in the suppression of hydrocarbon fires when forming a thin film layer by fluorinated surfactant on the surface. However, too much film-forming additive decreased the marginal fire extinguishing effectiveness due to the saturation effects of surfactants. Addition of a small quantity of film-forming additives did not improve the performance of water mist for ethanol fires, which is considered to be eroded by the fuel. Addition of metal compounds increased the effectiveness of water mist gradually both for ethanol and hydrocarbon fires, but there also existed upper agent limit because of the associated limiting vapor pressure of the active metal compound. The multi-component additive showed a combined suppression effect of film-forming agent and metal chemicals. It effectively extinguished both ethanol and hydrocarbon fires though coupling the physical and chemical fire suppression mechanisms and seems worth further exploration.