RU2401679C1 - Foam generator of acoustic type - Google Patents

Abstract

FIELD: fire-fighting equipment.

SUBSTANCE: in foam generator of acoustic type conical diffuser is movably fastened on one of hollow cylindrical body ends, inside of which coaxially to it and with clearance to it placed is tube, supplying foam former water solution, on one of whose ends coaxially to socket of conical diffuser rigidly fastened is nozzle, performing functions of sprayer, which has external surface in form of blunted cone, whose conicity coincides with diffuser conicity, and consists of two separate parts, fastened to each other in such way, that between its parts there is gap "a", formed by two its coaxial conical surfaces, directed opposite to conical surface of blunted cone, which forms its external surface. On smaller base of nozzle blunted cone made is cylindrical milling, forming with external tube surface ring-shaped resonating cavity A. Resonating cavity B is formed in butt end of body, facing nozzle side, in form of open toroidal surface, part of which together with internal surface of body and external surface of tube form nozzle chink. Perpendicular to body fixed is tube for air supply under pressure, and tube, supplying foam former water solution, is fastened with its second end to confuser, rigidly connected with flange for connecting with aggregate for supply of foam former water solution, cylindrical shell rigidly connects flange with conical diffuser.

EFFECT: increase of efficiency of foam generator, which produces foam of low factor at boundary values of its operation conditions.

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Description

The invention relates to fire fighting equipment, and in particular to structures of foam generators.

The closest technical solution, chosen as a prototype, is a foam generator (see Recommendations for the design of an automatic sub-layer fire extinguishing system in reinforced concrete tanks and steel vertical tanks with a fixed and floating roof at Transneft facilities, M., 1996, p. 20, Fig. 7; p. 23, Fig. 10), consisting of a hollow cylindrical body, a conical diffuser, a pipe body with a tip coaxially located with a tip supplying an aqueous solution of a foaming agent.

A disadvantage of the known foam generator is the inability to produce foam of low multiplicity at boundary values of the operating conditions of the foam generator.

In sublayer fire extinguishing systems, the foaming agent is fed into the foam generator at a pressure of 8-10 atm., According to the "Fire Safety Standards 61-97". In the case when the foaming agent is supplied to the foam generator at the lower limit of permissible pressure (8 atm.) Or the negative ambient temperature is close to the lower limit of the permissible temperature of use of the foaming agent (-15 ° С), the foam generator begins to produce foam with a multiplicity below the allowable limit, i.e. less than 3. For this reason, to extinguish a fire in a reservoir with flammable liquids, a foaming agent volume is required that is much larger than the standard volume. In addition, part of the volume of the foam of small multiplicity does not float onto the flammable liquid mirror in the combustion zone, but is deposited on the bottom of the tank due to its greater specific gravity, relative to the specific gravity of the flammable liquid.

A technically achievable result is an increase in the efficiency of the foam generator that produces foam of low multiplicity at boundary values of the working conditions of the foam generator.

This is achieved by the fact that in an acoustic type foam generator consisting of a hollow cylindrical body, a conical diffuser, a pipe coaxially located with a tip supplying an aqueous solution of a foaming agent, the conical diffuser is movably fixed at one end of the hollow cylindrical body, and inside the body, coaxially to it, located with a gap to the body, a pipe supplying an aqueous solution of a foaming agent, while at one end of the pipe is fixed a tip that acts as a sprayer and is located coaxially with the bell of the conical diffuser, while the outer surface of the tip is made in the form of a truncated cone, the taper of which coincides with the cone of the diffuser, and the tip is rigidly attached to the end of the pipe, for example, by means of a threaded connection, while the tip consists of two separate parts fastened together by bolt fastening element so that between its parts there is a gap "a" formed by two coaxial conical surfaces of these separate parts, and the direction of the conical of shapes that form a gap “a” of the opposite conical surface of the truncated cone forming its outer surface, and a cylindrical groove is made on the smaller base of the truncated cone of the tip, which forms an annular resonating cavity A with the outer surface of the pipe, and at the end of the body facing the tip, the secondary resonant cavity B is located, formed at the end of the casing and shaped as an open toroidal surface, and the nozzle gap is formed by two cylindrical surfaces - the inner surface of the housing and the outer surface of the pipe, as well as part of the toroidal surface of the resonant cavity B, while the pipe for supplying air under pressure is attached perpendicular to the body, and the pipe supplying the aqueous solution of the foaming agent is attached with its second end to the confuser, rigidly connected to a flange for connecting to the unit for supplying an aqueous solution of a foaming agent, and a cylindrical shell rigidly connects the flange with a conical diffuser.

The drawing shows a General view of the foam generator of the acoustic type.

The acoustic foam generator consists of a hollow cylindrical body 1, a conical diffuser 2, movably mounted on one of its ends. Inside the housing 1, coaxial to it, is located with a gap 3 to the housing 1, a pipe 8, which supplies an aqueous solution of a foaming agent. At one end of the pipe 8, a nozzle 4 is fixed, which acts as a sprayer, and it is located coaxially with the socket of the diffuser 2. The outer surface of the tip 4 is made in the form of a truncated cone, the taper of which coincides with the conicity of the diffuser 2. The tip 4 is rigidly attached to the end of the pipe 8 by threaded connection. It consists of two separate parts 4 and 6, fastened together by a bolt fastening element 7, so that between its parts there is a gap "a" formed by two coaxial conical surfaces of these separate parts, and the direction of the conical surfaces forming the gap "a" opposite to the conical surface of the truncated cone forming its outer surface. A cylindrical groove is made on the smaller base of the truncated cone of the tip, which forms an annular resonating cavity A. with the outer surface of the pipe 3. At the end of the body facing the side of the tip 4, there is a secondary resonant cavity B formed in the end of the body and made in the form of an open toroidal surface. The nozzle gap 5 is formed by two cylindrical surfaces: the inner surface of the housing 1 and the outer - pipe 8 and part of the toroidal surface of the resonating cavity B.

Perpendicular to the housing 1, a tube 12 is attached to it for supplying air (gas) under a pressure of about 0.3 ... 0.6 MPa. A pipe 8 supplying an aqueous solution of a foaming agent is fastened with its second end to a confuser 9, rigidly connected to a flange 10 for connection to an assembly (not shown in the drawing) for supplying an aqueous solution of a foaming agent. The cylindrical shell 11 rigidly connects the flange 10 with a conical diffuser 2.

Foam acoustic type operates as follows.

The foaming agent aqueous solution flows through the pipe 8 into the tip 4, and from there through the gap “a” it enters the zone of acoustic vibrations, the source of which is the gaseous medium flowing from the nozzle gap 5 into the resonating cavity A.

Under the influence of the energy of acoustic vibrations, the aqueous solution of the foaming agent is sawn up and then, carried away by the gaseous medium exhausted in the emitter (having a certain direction due to the gap between the tip 4 and the diffuser 2), it forms a spray of liquid. The desired shape of the torch can be obtained by moving the diffuser 2 along the axis of the atomizer. Acoustic vibrations arising in the “nozzle slot 5 - resonant cavity A” system are amplified in the secondary resonant cavity B. Acoustic vibrations ensure the fragmentation of a heterogeneous foam and the formation of a finely dispersed (1-2 mm across) homogeneous foam at the outlet of the foam generator. Such a foam, consisting of small bubbles, easily passes through a layer of flammable liquid and almost all floats on its surface, providing effective fire fighting. The resistance to crushing of small bubbles is explained by the fact that the surface tension forces on a small bubble are very large and very large external forces are required to tear the bubble shell.

In the case of a heterogeneous structure of the foam bubbles (large and small), large bubbles have a very thin shell and small surface tension forces, so when they pass through a layer of flammable liquid they burst, the aqueous solution of the foaming agent from which the bubble was deposited, due to its larger specific gravity to the bottom of the tank and actually does not contribute to extinguishing the fire. Only small bubbles reach the burning surface. To extinguish a fire with the help of foam generators that produce foam of a heterogeneous structure, more time and a greater amount of foaming agent are required, which has a greater cost.

Even under the boundary conditions of the foam generator, i.e. at low pressures of the foaming agent aqueous solution at the inlet of the foam generator (8 atm.) and low ambient temperatures (-15 ° C), the foam, under the pressure generated by the foam generator, is fed into the lower layer of flammable liquids in the tank, floats to the surface, where it forms spreading over the surface, a film resistant to fire, which is not destroyed by fire, which stops the access of oxygen to the combustion zone, and the fire stops.

Claims (1)

An acoustic type foam generator, consisting of a hollow cylindrical body, a conical diffuser, a coaxially arranged pipe body with a tip supplying an aqueous solution of a foaming agent, characterized in that the conical diffuser is movably fixed at one end of the hollow cylindrical body, a coaxial body of the pipe supplying an aqueous solution of a foaming agent, located inside the housing with a gap to it, and the tip is fixed at one end of the pipe coaxially with the bell of the conical diffuser and performs the functions p a aspirator, wherein the outer surface of the tip is made in the form of a truncated cone, the conicity of which coincides with the cone of the diffuser, and the tip is rigidly attached to the end of the pipe, for example, by means of a threaded connection, while the tip consists of two separate parts fastened together by a bolt fastening element such so that between its parts there is a gap "a" formed by two coaxial conical surfaces of these separate parts, and the direction of the conical surfaces forming the gap " a ”, opposite to the conical surface of the truncated cone forming its outer surface, and a cylindrical groove is made on the smaller base of the truncated cone of the tip, which forms an annular resonating cavity A with the outer surface of the pipe, and a secondary resonating cavity is located at the end of the body facing the tip B, formed at the end of the housing and made in the form of an open toroidal surface, and the nozzle gap is formed by two cylindrical surfaces - the inner the surface of the housing and the outer surface of the pipe, as well as part of the toroidal surface of the resonant cavity B, while perpendicular to the housing is attached a pipe for supplying air under pressure, and the pipe supplying the aqueous solution of the foaming agent is attached with its second end to the confuser, rigidly connected to the flange for connection to the unit for supplying an aqueous solution of a foaming agent, and a cylindrical shell rigidly connects the flange with a conical diffuser.

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