SU1509087A1 - Method of generating gas foam for extinguishing a fire - Google Patents

Abstract

The invention makes it possible to increase the stability of the foam and increase the productivity of the process. The products of combustion of hydrocarbon fuel with a temperature of 600-900 ° C are cooled with sprayed water to a temperature of 150-200 ° C and steam content of 20-25%. The resulting gas-vapor mixture is fed to the grid at a speed of 6-7 m / s. 1 tab.

Description

The invention relates to the field of fire extinguishing, in particular, to a method for producing a gas-mechanical fire extinguishing foam.

The purpose of the invention is to increase the stability of the foam and increase the productivity of the process.

Examples 1-3. To dry the process, the hydrocarbon fuel is burned in a turbojet engine with a capacity of 1.68 kg / s. The combustion process is controlled so that at the exit from the turbine of the engine the temperature of the gases is 600 ° C. The ratio of air consumption and fuel is chosen so that the volume content of oxygen in the combustion products is 15%. A decrease in the gas temperature and the production of a vapor-gas mixture are carried out in a cooling chamber with sprayed water up to 150 ° C. The required amount of water to cool the combustion products and the amount of evaporated water to obtain a 25% volumetric steam content is determined by the formulas

SgpSp (Gpg-7 k) + 0 / 7g + Svsv ()

 CrCr () (1)

a, Cr. (100-CO / (pC.), (2)

where Gn is the mass of water evaporated, kg / s; Gr is the mass of gas, kg / s;

GB is the mass of water supplied for cooling, kg / s;

 Cm - the average heat capacity of steam within the temperature range, kJ / kg-K;

Si is the heat capacity of water, kJ / kg-K;

Cr is the average heat capacity of the gas within the temperature range kJ / kg-K;

Gsh is the temperature of the vapor-gas mixture. TO;

HH is the boiling point of water. TO;

 - temperature of the water going to cool, K;

Gg is the temperature of the gases used for cooling, K;

g is the heat of evaporation of water, kJ / kg;

C - steam content of the gas-vapor mixture.

In the above example, Tg 600 ° C 873 K; 7 K; 7k 100 ° C 273 K; 7 pg 150 ° C 423 K.

The heat capacities of water, gas, and steam within the specified temperature limits are: Cn 2 kJ / kg-K; C, 4.2 kJ / kg-K; C, 1.08 kJ / kg-K.

Heat of evaporation of water kJ / kg.

The density of steam and gas is necessary for the transition from bulk steam content to mass flow of steam: r: 0.515 kg / m; Pr 0.846 KG / M-.

Substituting the above values in expression (1), we find the mass of water Ge, optionally

cl

ate

about with

About 00

1.68 kg / s of gas up to G, 150 ° C, required for cooling Gr, and from expression (2) the mass of steam C is found to obtain a gas-vapor mixture with a steam content of 25%: C = 0.42 kgf / s; , 42 kg / s.

This shows that the evaporation coefficient is 1, i.e. it is necessary to produce complete evaporation of the supplied water.

From the expression Co2t1g Co2g- (100-Cn), where Co2pg is the volumetric oxygen content of the vapor-gas mixture;

 - volume content of oxygen in the gas mixture;

Cn - steam content vapor-gas

mixes

find the volumetric oxygen content of the vapor-gas mixture

CSP 15 (100-25) 11.25%.

A steam-generating grid with a diameter of 0.6 m is used and the resulting gas-vapor mixture is fed at a speed of 0 m / s with jMecTHO with a frother solution. Knowing the mass flow rate of steam and gas and their density, they find the volumetric flow rate of the vapor – gas mixture on the grid and the volume of the generated Gti foam 1.7.

The method is implemented in a similar way with the average and maximum values of the specified parameters.

The specified, obtained, and proposed parameters (Cn — foam productivity, f — foam half-life) in Examples 1-3 are tabulated.

The advantage of the proposed method in comparison with the known method is an increase in foam stability by a factor of 2-3, an increase of 2-2.3 times the generator productivity in foam, due to an increase in the rate of foam generation on the grid. Low steam content and high stability lead to a reduction in steam condensation and fluid deposition in mine workings. An increase in the efficiency of fire extinguishing is achieved by the fact that a stable foam

transported over long distances to the source of fire, the gas phase of the foam, containing 11–12% of oxygen, collects flame combustion, and the foam has a higher heat capacity (2.5–3 kJ / kg-K) compared to the vapor – gas mixture (1.4 kJ / kg-K), cools the combustion center more quickly, which reduces the fire extinguishing time by 2 times in comparison with the known method of producing foam.

Claims (1)

Invention Formula A method for producing a gas-mechanical foam to extinguish a fire, including burning hydrocarbon fuel, cooling the combustion products with sprayed water and feeding the resulting vapor-gas mixture and frother to the foam generating network, characterized in that the combustion products are cooled with temperature to increase foam stability and increase process performance 600 - 900 ° C sprayed water to a temperature 150–200 ° C and a steam content of 20–25%, and the supply of the vapor – gas mixture to the foam generating network is carried out at a speed of 6–7 m / s.