SU1718981A1 - Fire extinguishing method - Google Patents

Abstract

The invention relates to fire extinguishing techniques and allows for an increase in the fire extinguisher supply range and the effectiveness of fire extinguishing. Before being supplied to the combustion zone, the fire extinguisher is sprayed and fed to the barrel, which is also supplied with a cryogenic product. they are mixed together to convert the fire extinguisher from a liquid to a solid granular state, and a cryogenic product from a liquid to a vaporous state. The resulting mixture is accelerated to the speed of sound propagation in the vapor of the cryoproduct, while the cryoproduct is fed into the barrel at a mass flow rate described in the description text of the invention. 1 hp f-ly, 1 ill.

Description

The invention relates to a fire extinguishing technique and can be used in stationary and mobile installations, especially in cases when fire extinguisher is required for long distances, for example, when extinguishing a fire in buildings and structures of great height, as well as in cases when a large energy impact on the burning zone is required.

The aim of the invention is to increase the range of the fire extinguisher and the effectiveness of extinguishing the fire.

This goal is achieved in that in the method consisting in supplying the fire extinguisher to the fire extinguisher, before being supplied to the combustion zone, the atomizer is sprayed, mixed with the cryogenic product, kept in the mixing zone until the full phase transformation of the fire extinguisher from the liquid to the solid granular state the product is from liquid to vapor state, and the resulting

mixture up to a speed not lower than the speed of sound propagation in cryoproducts.

In addition, cryoproduct served with mass flow

mi

WITH

WITH

.. (Ti - T2) Ci + (TrN T3) C2 + T2 (N-1) T3C3 + G1

GP2

00

about

00

where Ti and T2 are the supply temperature of the fire extinguisher in the liquid phase and the temperature of its crystallization, respectively, K;

Tc is the boiling point of the cryoproduct under pressure in the mixing zone, K;

Ci and Ca are the heat capacities of the fire extinguisher in the liquid and solid phases, respectively, kJ / kg-K;

Сз is the heat capacity of the vapor of a cryoproduct under constant pressure, kJ / kg-K;

P - heat of evaporation of cryoproduct. kJ / kg;

TI — heat of crystallization of a fire extinguisher, kJ / kg;

N - coefficient selected within

K 1M T2 / Tz;

t2 - mass consumption of fire extinguisher, kg / s.

An exemplary embodiment of the method is a device.

The drawing shows a device that implements the method.

The device includes a barrel 1, adjacent to it, on one side, the spray gun 2 of the fire extinguisher and flexible supply hose 3 of the cryoproduct, and on the opposite side, coaxial to the barrel of the nozzles 4, as well as the fire extinguisher manifold 5 covering the spray gun 2 of the fire extinguisher. and adjacent to the manifold 5 flexible hose 6 supply fire extinguisher. Nozzles 4 can be made tapering or in the form of a Lawal nozzle.

The method is carried out as follows.

The fire extinguisher (water) in the liquid phase is fed under pressure through the fire extinguisher supply hose 6 to the manifold 5. Water is sprayed through the sprayer 2 into the barrel 1. Through the hose 3 into the barrel 1 a cryo-product (liquid nitrogen) is fed. In barrel 1, water sprayed is mixed with liquid nitrogen. Mixing is ensured by supplying water droplets from the sprayer 2 at an angle of 5-15 ° to the direction of movement of the liquid nitrogen. For the complete phase transformation of the fire extinguisher and the cryoproduct, they are kept in the mixing zone for at least 0.5 s at a temperature below the crystallization temperature of the fire extinguisher, but above the boiling point of the cryoproduct under pressure in the mixing zone. The residence time is provided by regime parameters in the mixing zone: temperature, pressure, speed of movement of the mixture, as well as the length of the mixing zone. The granular state of the solid fire extinguisher is provided by spraying the liquid fire extinguisher into the droplets and mixing them with the cryoproduct.

In nozzle 4, the resulting mixture is accelerated to a speed not lower than the speed of sound propagation in pairs of the cryoproduct. This is ensured by the vapor pressure of the cryoproduct before the nozzle 4 above the critical pressure ratio (for nitrogen 1.9), as well as a decrease in pressure in the nozzle due to its special profile. Flow of cryoproduct with flow

mi

- (Ti - T2) C2 + (T2 - N Tz) C2 + g2

(N-1) T3C3 + Ti2

allows for temperature conditions for the phase transformation of the fire extinguisher from a liquid to a solid granular state and a cryoproduct from a liquid to a vapor state.

The dependence of the cryoproduct consumption on the fire extinguisher consumption was obtained empirically on the basis of the energy balance according to the condition of the phase transformation of the fire extinguisher and the cryoproduct.

In the considered example of implementation of the method with a pressure in the mixing zone 5, this boiling point Tz of liquid nitrogen will be 94.15 K, the limit of change

N coefficient: 1 N 2.9. With N 1.7, water consumption t2 1 kg / s; Ti-288.15 K water supply temperature; water crystallization temperature T2 273.15 K; heat capacity of water, 18 kJ / kg-K; ice heat capacity

with 2.09 kJ / kg-K; heat capacity of nitrogen at constant pressure Сз 1.11 kJ / kg-K; the heat of evaporation of liquid nitrogen is 175.4 kJ / kg and the heat of crystallization of water G2 332.4 kJ / kg, the flow rate of liquid nitrogen, 54 kg / s.

The temperature in the mixing zone in this case is 160 K, i.e. 66 K above the boiling point of liquid nitrogen at a pressure of 5 this and 113 K below the temperature

water crystallization. Consequently, conditions for evaporation of liquid nitrogen and freezing of water are provided in the mixing zone. Outside the specified interval, for example, at N 2.95 the consumption of liquid nitrogen

mi is 1.01 kg / s, and the temperature in the mixing zone is 277.7 K, i.e. 4.55 K higher than the freezing point of water. Therefore, the condition for the phase transition of the cooler from the liquid to the solid state is not met.

and the method is not implemented due to insufficient consumption of liquid nitrogen. At N 1, for example at N 0.95, the flow rate of liquid nitrogen m 1 is 4.46 kg / s, the temperature in the mixing zone is 89.4 K, i.e. 4.7 K below temperature

boiling in the mixing zone. In this case, the method is also not implemented, since due to the excessive consumption of the cryoproduct, the phase transition of the cryoproduct from the liquid to the vapor state is not carried out.

At 1.7 N and feed pressure of 5 this (A these) flow rate of the mixture of granulated ice and nitrogen vapors if tapering nozzles 4 are used and it is equal to the speed of sound propagation in nitrogen peers is 233 m / s, whereas In the known method, the flow rate of water is 23.2 m / s. those. the speed of the mixture is 10 times the speed of water, and the maximum ideal range of flow (without taking into account air resistance) is 100 times greater than the same range of flow with the known method.

When the pressure at the outlet of the nozzle 1 is eta (this is ensured when the nozzle in the form of a Laval nozzle is used, according to known dependencies), the flow rate of the mixture will be 345.3 m / s, and the feed distance will be 221.5 times the feed distance with the known method. The maximum ideal range in this case is 12 km.

At N 1.7, the ice granules have a temperature of 160 K and an energy effect, which can be estimated as the amount of heat absorbed in the combustion zone by a unit of mass of the fire extinguisher when it is heated from the supply temperature to 473 K, i.e. below the ignition rate of conventional combustible substances (for example, wood), is 3638 kJ / kg, whereas with the known method with water supply it is 3006 kJ / kg. With N 1.05, the supply temperature of the fire extinguisher is 98.9 K; energy impact of 3766 kJ / kg, i.e. 25.3% more than with the known method.

The impact on the combustion zone also increases due to the supply of cryogenic vapors along with the solid extinguisher, which displace air from the combustion zone.

FORUMAWLAH AND ISLANDS

Claims (2)

1. Fire extinguishing method consisting in supplying the fire extinguisher to the fire zone, so that, in order to increase the fire extinguisher supply range and fire extinguishing efficiency, before being fed to the fire zone, the fire extinguisher is sprayed, mixed with the cryogenic product, kept in the mixing zone until the complete phase transformation of the fire extinguisher from the liquid to the solid granular state, and the cryogenic product from the liquid to vapor state and disperse the resulting mixture to a speed not lower than the speed of sound propagation in the vapor of the cryoproduct. 2. The method according to claim 1, of which the supply is carried out with a mass flow rate mi 20  (Ti-T2) Ci + (T2 -NT3) C2 + G2 (N.-1) TzSz-G1. GP2 where Ti and T2 are the supply temperature of the fire extinguisher in the liquid phase and the temperature of its crystallization, respectively, K; Тз boiling point of cryoproduct with pressure in the mixing zone, K; Ci and C2 are the heat capacities of the fire extinguisher in the liquid and solid phase, respectively, kJ / kg-K; Сз is the heat capacity of the vapor of a cryoproduct with constant pressure, kJ / kg K; p is the heat of evaporation of the cryoproduct, kJ / kg; G2 - heat of crystallization of the fire extinguisher, kJ / kg; N - coefficient chosen within 1 M T2 / Tz; GP2 - mass fire extinguisher, 45 kg / s.