Suppression of a flame of combustible liquids with high flashpoint by the method of agitating of layers using air and low expansion foam (sublayer method)

The method of agitating, used for suppression of diesel fuel, was actively developed in the 60-ies of the XX century and generalized in works of Blinov - Khudyakov. There was described suppression of oil fires by supplying of air stream into the bottom of tank. The air is not a fire extinguishing substance, but in this specific case it helps to achieve the burn termination effect. Suppression is provided not with air but due to agitating of cold layers of an oil product with the burning surface layer, actually it is a question of the method of suppression by means of air which creates conditions for agitation. On the basis of experimental researches it was determined the quantitative correlation of suppression time and air specific consumption from supply intensity of the air stream coming into the bottom of tank contained the burning liquid with high flash point. The model of process of combustible liquid flame suppression using the method of agitating of "cold" layers by air stream supplying into the bottom of tank with burning diesel fuel is considered. The suppression process analysis based on consideration of the material balance of liquid coming into the surface layer and going down into the depth due to convective streams which are formed by rising air flow and due to the difference in densities of "cold" and burning liquid is carried out. The results of experimental measurements of dependence of suppression time on intensity of air supply during diesel fuel flame suppression obtained in terms of proving ground and test bench are presented. Comparison of the fire test results obtained during suppression of diesel fuel flame in model test bench and, earlier received, in terms of proving ground is carried out. It is shown that the process of suppression is connected with formation of a thin liquid layer, from 1.5 to 3 mm, which appear on the surface of aburning hydrocarbon and have a temperature lower or equal to temperature of flash point, which are coming up to the surface with rising burning layer. Comparison of calculation results and experimental data on suppression of a diesel fuel flame in terms of proving ground and on the test bench is carried out. On the basis of conducted researches there were determined the optimal values of intensity and the minimal values of air specific consumption supplying into the bottom of tank for suppression of a diesel fuel flame.