RU2176925C1 - Method and apparatus for producing fire-suppressing mixture - Google Patents

Abstract

FIELD: firefighting method and equipment. SUBSTANCE: method involves grinding gas-powder mixture in auger-type swirler; accelerating gas powder in supersonic nozzle and directing to knock wave generated during running of supersonic flow onto conical body positioned at supersonic nozzle outlet end. Preliminarily ground fire-suppressing powder colliding with knock wave serving as penetrable barrier is dispersed into aerosol. Finely dispersed gas-aerosol mixture is formed by means of nozzles into atomized cloud or compact flow and supplied into fire zone. Apparatus has auger-type swirler, arranged at supersonic nozzle inlet end, and conical body and nozzle head which are arranged at supersonic nozzle outlet end. Apparatus may be arranged in vessel containing fire-suppressing powder, when it is employed in stationary fire-extinguishing units, and may be detached from vessel by means of flexible hoses, when apparatus is used as column mount or hand-held gun. Apparatus may be connected to hose of knapsack-type or mobile fire-extinguishers. EFFECT: increased efficiency, simplified method and construction and enhanced reliability in operation. 6 cl, 2 dwg

Description

 The present invention relates to a method for producing a fire extinguishing mixture and a device for its implementation and can be used in the development of technical means for volumetric and local fire extinguishing, that is, it can be used to extinguish fires in conditionally sealed rooms, as well as to extinguish open fires by supplying directed jet of extinguishing agent to the burning area.

 Known methods for producing a fire extinguishing mixture, consisting in the fact that as the starting components use a fire extinguishing powder and compressed air or inert gas, which carry out the fluidization of the powder, and the resulting gas-powder mixture using nozzles serves in the fire [1, 2, 3]. In this case, the extinguishing powder is placed in cylindrical or spherical containers equipped with an aerofoil or nozzles for supplying compressed gas, which is stored in separate cylinders connected to the powder containers by a pipeline and a locking and starting device.

The disadvantage of these methods is the high consumption of fire extinguishing powder due to the low fire extinguishing efficiency of the gas-powder mixture. According to [1], the extinguishing efficiency of the gas-powder mixture is 0.6 kg / m ³ . In this case, the concentration of powder in the gas-powder mixture is in the range of 70 ... 140 kg / kg.

 It is known from the theory of powder quenching [4] that the smaller the size of the powder particles, the higher their fire extinguishing ability. However, an increase in the dispersion of fire extinguishing powders with existing methods for their preparation and use dramatically reduces operational properties (increased moisture absorption, clumping and caking), which excludes the possibility of their use in technical fire extinguishing equipment. Therefore, the most promising is the method of obtaining a fire extinguishing mixture, providing simultaneous production of highly dispersed powder particles and feeding them into the fire.

 Such methods for producing fire extinguishing mixtures are known [5, 6, 7, 8, 9]. They are based on the burning of pyrotechnic or solid propellant charges. In this case, pyrotechnic compositions are subjected to combustion, including nitrates and / or alkali metal perchlorates and a fuel-binder in stoichiometric ratios. In some charge formulations, ballistic gunpowder is used as a combustible binder [7].

 Upon combustion of such compositions, a fire extinguishing mixture is formed, consisting of inert gases (nitrogen, carbon dioxide, water vapor) and condensed compounds of alkali and / or alkaline earth metals (oxides, hydroxides, carbonates, bicarbonates, chlorides, etc.) in the form of micron-sized solid particles (spray can).

 The ratio of solid and gas phases by mass, at which high extinguishing efficiency of the resulting mixture of extinguishing aerosol is ensured for various charge formulations is in the range 0.5 ... 1.5 kg / kg [5].

 This method of producing fire extinguishing mixtures has a number of significant disadvantages.

 Firstly, the temperature of the fire extinguishing mixtures obtained by burning pyrotechnic compositions is 1700 ... 2000 K, which leads to a sharp increase in the volumetric average temperature inside the protected room.

 The methods used to lower the temperature due to the supply of liquid carbon dioxide [8] to the combustion zone of the pyrotechnic charge [8] or due to air ejection [9] greatly complicate the design of the device, and the use of special nozzles filled with a porous cooler sharply reduces the velocity of the dispersed flow, which contributes to the coagulation of fine particles particles into larger conglomerates. As a result, the fire extinguishing efficiency of the resulting mixture decreases by 2 ... 2.5 times [5].

Secondly, in some formulations, ballistic gunpowders are used as a combustible binder [7]. However, the nature of the ballistic combustible base determines the disadvantage of this method of obtaining a fire extinguishing mixture, because during the burning of nitrocellulose powders, in addition to inert gases, such components as N ₂ O, NO, NO ₂ and others enter the gas component of the fire extinguishing mixture, which greatly affects the toxicological properties of the fire extinguishing mixture.

 Thirdly, pyrotechnic and solid propellant charges for producing fire extinguishing mixtures (fire extinguishing aerosol) are sabotage-hazardous products, since burning them in an enclosed space passes into an explosion [10]. Under the current criminal situation in the country, the widespread use and uncontrolled use of such charges can lead to unpredictable results.

 Fourthly, the design schemes of the fire extinguishing aerosol generators, the specifics of the ignition unit device, as well as the degree of temperature reduction of the extinguishing mixture (extinguishing aerosol) do not allow the use of these devices to protect explosive rooms and zones of class B-1a, which reduces their scope.

 A known method and device that provides the use of energy of compressed gas for spraying a fire extinguishing agent with a pulsed feed [11].

 The device for pulsed supply and fine dispersion of substances consists of a variable-section ejection pipe made in the form of a Laval nozzle and having a flat elastic multi-segment valve at the output end, a compressed gas reservoir and a quick-acting shut-off valve connecting the reservoir to the inlet end of the ejection pipe. When the device is operating, the potential energy of the compressed gas enclosed in the tank is converted into the kinetic energy of the extinguishing agent stream.

 The disadvantage of this device is the incomplete use of the potential energy of the compressed gas, which reduces the energy of the jet of extinguishing agent and its degree of dispersion, as a result of which the efficiency of the device and extinguishing the fire is reduced.

 These disadvantages are visible when considering the operation of the device, taking into account the analysis of the laws of gas dynamics [12].

Since the process of expansion of the gas during the displacement of the liquid from the exhaust pipe is adiabatic, the equation expressing the relationship between pressure and volume is:
P _o V $\genfrac{}{}{0ex}{}{\text{to}}{\text{o}}$ = P • V ^k , (1)
where P ₀ is the initial gas pressure in the tank;
V ₀ - the initial volume of gas in the tank;
P is the current gas pressure in the gas cavity of the tank and the exhaust pipe;
V is the current volume of gas in the gas cavity of the tank and the exhaust pipe;
K is the adiabatic exponent. For air, it is 1.4.

из которой с учетом уравнения (1) получим:

где V_а - объем, занимаемый рабочим газом при атмосферном давлении.The potential energy of compressed gas P ₀ can be determined by the formula:

from which, taking into account equation (1), we obtain:

where V _a is the volume occupied by the working gas at atmospheric pressure.

где V_кон - объем, занимаемый газом при полном вытеснении огнетушащего вещества из трубы выброса, т.е. объем резервуара и объем трубы выброса.The final pressure in the tank and in the exhaust pipe when the fire extinguishing agent is completely displaced from it is determined from equation (1):

where V _kon is the volume occupied by the gas during the complete displacement of the extinguishing agent from the exhaust pipe, i.e. tank volume and discharge pipe volume.

 According to the description, the volume of the reservoir for compressed gas is equal to the volume of the cavity of the exhaust pipe, and the initial pressure in the reservoir is 4.0 MPa. Given the above data according to equations (3) and (4), it is easy to determine that 30% of the potential energy of the compressed gas is not used during the operation of the device.

 Since the final gas pressure in the tank-exhaust pipe system after displacement of the extinguishing agent according to formula (4) and the data given in the description will be more critical, the remaining gas due to the fact that the exhaust pipe is made in the form of a Laval nozzle (supersonic nozzle) will expire from the device at a speed above the speed of sound. However, it after displacement of the extinguishing agent from the device will not affect its spray.

 As for the rate of outflow of the extinguishing agent from the exhaust pipe when it is displaced by compressed gas, in accordance with the laws of hydraulics [13], for the case under consideration, it depends only on the pressure of the displacing gas in the tank and the hydraulic resistance of the multi-segment valve at the outlet end of the exhaust pipe.

 In accordance with the continuity condition, the fluid flow rate during its movement along the ejection pipe of variable cross-section cannot be reached by the speed of sound, since the density of the liquid remains constant. And only for gas, when it flows in the expanding part of the exhaust pipe, the density decreases and, as a result, the gas velocity increases, which can reach a speed greater than the speed of sound.

 The closest technical solution, selected as a prototype by the number of common essential features, is a powder fire extinguisher [14].

 The specified fire extinguisher includes a casing filled with fire extinguishing powder, a gas source with means for supplying it to the bottom of the fire extinguisher, a shut-off-start valve and ejector-type exhaust nozzles made in the form of a diffuser-confuser, i.e., in the form of a conical tapering nozzle installed inside a cylindrical nozzle in which the acoustic oscillator is located, made in the form of a resonator plate located axisymmetrically to a gas-powder jet, with the possibility of moving the resonator along the outer Induction nozzle. In addition, in the body of the fire extinguisher on the side of the outlet there is a chipper for a fluidized powder jet.

 The disadvantage of this device is the low fire extinguishing ability of the gas-powder mixture, since a careful analysis of the operation of the device shows that grinding particles of the fire extinguishing powder does not occur in this device.

Ускорение газового потока до сверхзвукового (M>1) можно достичь только лишь в сверхзвуковом коническом расширяющемся сопле или в специально профилированном сопле Лаваля.First, in accordance with the laws of gas dynamics [12], the speed of a gas jet flowing out of a conical narrowing nozzle can reach the speed of sound M = 1 only at the nozzle exit. Here M is the Mach number, which is the ratio of the velocity of the gas stream V _g to the speed of sound propagation in the gas a, i.e.

The acceleration of the gas flow to supersonic (M> 1) can only be achieved in a supersonic conical expanding nozzle or in a specially profiled Laval nozzle.

 Secondly, from the analysis of the working processes of the gas ejector, it follows that if the velocity of the ejection jet emanating from the nozzle is equal to or greater than the speed of sound (M≥), then with the distance from the nozzle taking into account the ejected air, the core of the ejection gas-powder jet decreases. The speed of the gas-powder mixture and the ejected air is gradually equalized over the cross section of the mixing chamber (cylindrical nozzle), while the flow rate of the extinguishing mixture becomes subsonic (M <1).

 This stream interacts with the resonator and excites acoustic vibrations in it. Powder particles passing through the zone of acoustic vibrations are affected by acoustic waves rather than shock waves, since shock waves arise only when a supersonic flow runs onto obstacles.

 Thirdly, the influence of acoustic waves causes coagulation, i.e. sticking together of fine particles in a gas stream, and not their dispersion, i.e., grinding. This property of acoustic vibrations is widely used in industry for cleaning dust from exhaust gas into the atmosphere [17].

 The aim of the invention is to increase the fire extinguishing efficiency of the mixture.

 This goal is achieved by the fact that due to the full use of the potential energy of compressed gas and the kinetic energy of the gas-powder jet, the extinguishing powder at the outlet of the device is ground to a finely dispersed state — aerosol, because it is known [4] that the smaller the particle size of the extinguishing powder, the higher its fire extinguishing ability.

 In [5], it was shown that a change in the concentration of the dispersed phase in the gas in the direction of increase or decrease leads to a decrease in the fire extinguishing ability of the mixture. This is due, on the one hand, to the fact that in a fire extinguishing mixture with a decrease in the concentration of solid particles, the mass fraction of inert gas increases, which has a lower fire extinguishing ability compared to condensed particles, which in this case determines a decrease in fire extinguishing ability. On the other hand, an increase in the concentration of solid-phase particles by reducing the mass fraction of inert gas leads to significant dynamic coagulation and an increase in particle size, which ultimately also reduces the fire extinguishing ability of the mixture.

In [1,15], it was pointed out that it is possible to consider the basic laws of motion of two-phase jets as single-phase jets with insignificant (1 ... 2 kg / kg) concentrations of the dispersed phase. However, due to the peculiarities of the movement of the two-phase mixture in the nozzles of rocket engines [16], the kinetic energy of the two-phase flow is used more efficiently when it is accelerated not in a supersonic profiled nozzle (Laval nozzle), but in a conical nozzle with an opening angle of 12 ... 15 ^o .

Для определения угла конического тела ω существует зависимость α = f(ω,M), представляемая графически в специальной литературе по газодинамике, например [12].It is known from the laws of gas dynamics [12] that when a supersonic flow runs onto obstacles, shock waves — shock waves — arise. If the barrier is located normal to the gas flow (90 ^o ), then a direct shock wave occurs, and if the obstacle is located at an angle to the flow, for example, a conical body, then oblique shock waves occur. In this case, the front of the shock wave is located at an angle α to the direction of the supersonic flow and depends on the angle of the conical body (projectile, supersonic plane, rocket, etc.). The range of variation of the angle α for oblique shock waves depends on the Mach number (M) and is in the range 90 ^° >α> α _o , where α _o is the limiting angle of inclination of the shock wave during oblique shock waves. It is determined from the expression

To determine the angle of the conical body ω, there exists a dependence α = f (ω, M), which is represented graphically in the specialized literature on gas dynamics, for example [12].

где K - показатель адиабаты. Для воздуха K = 1,4, для диоксида углерода K = 1,2.The main feature of the shock wave used by the applicant to solve the problem, as follows from the theory of shock waves, is that the thickness of the front of the shock wave is very small and is of the order of the mean free path of the molecule, i.e., it is the value of the molecular level. In this regard, in the front of the shock wave, the main parameters of the gas state (pressure, density, temperature) change stepwise. For example, the limiting ratio of the gas density in the shock wave (ρ ₁ ) and in the incident flow (ρ _n ), called the shock adiabat, is determined by the dependence

where K is the adiabatic exponent. For air, K = 1.4; for carbon dioxide, K = 1.2.

а для диоксида углерода

В соответствии с изложенным в заявляемом устройстве в качестве газа-носителя применяется диоксид углерода.Therefore, when moving a gas-powder mixture, where the carrier gas is air

and for carbon dioxide

In accordance with the foregoing, in the inventive device, carbon dioxide is used as a carrier gas.

Так как для диоксида углерода

(M²-1). Из этого выражения видно, что даже при движении газа со скоростью звука (M=1), ударная волна не возникает, а возникает только лишь при значениях M>1, т.е. при сверхзвуковых скоростях. Поэтому при взаимодействии струи со скоростью M<1 с резонатором (наиболее близкий аналог) ударные волны не могут возникнуть, а возникают лишь только акустические колебания.The ratio of the pressures in the front of the shock wave (P ₁ ) to the statistical pressure of the incoming flow (P _n ) is determined by the dependence:

Since for carbon dioxide

(M ² -1). It can be seen from this expression that even when the gas moves at the speed of sound (M = 1), a shock wave does not occur, but arises only at values of M> 1, i.e. at supersonic speeds. Therefore, when a jet interacts with a speed M <1 with a resonator (the closest analogue), shock waves cannot arise, but only acoustic vibrations arise.

 The essence of the method for producing a fire extinguishing mixture is that by aerating the extinguishing powder with compressed gas supplied to the bottom of the powder container and feeding the gas powder mixture into the nozzle and nozzles, according to the invention, the gas powder mixture is initially ground in a screw swirl, then it is dispersed in a supersonic nozzle and direct it to a shock wave that occurs when a supersonic gas-powder flow runs onto a conical body mounted at the exit of a supersonic nozzle, interacting with which as with a permeable barrier, the pre-ground extinguishing powder is dispersed into an aerosol, and the resulting ultrafine gas-aerosol mixture is formed using nozzles in the form of an atomized cloud or a compact jet and fed into the fire source.

A device for implementing the method, comprising a container with a powder equipped with a chipper, a source of compressed gas with a means of supplying it to the bottom of the container with a powder, a shut-off / start valve, a cylindrical nozzle and a nozzle according to the invention, characterized in that the supersonic nozzle is made in the form of an expanding 12-15 ^o cone with an opening angle, at the entrance to which is placed a screw swirler configured as a hollow cylinder with an axially disposed therein core around which is wound a helical plane image yuschaya cylinder with a helical channel. And at the exit of the supersonic nozzle is a conical body and cylindrical nozzles. In addition, to obtain an atomized cloud, the cylindrical nozzles at the level of the conical body have round or slit-like openings. Also, carbon dioxide is used as a source of compressed gas. In this case, the chipper is made in the form of a cone, the top of which is directed towards the outlet of the container with the powder. Moreover, the screw channel is made with a variable pitch.

 In FIG. 1 and 2 show two modifications of the claimed device for producing a fire extinguishing mixture.

 The device (Fig. 1) consists of a cylindrical body 1. Inside of which the rod 2 is placed axisymmetrically. A screw plane (screw) is located around the rod with a variable twist pitch 3, which forms a helical channel at the entrance to the body with its cylindrical surface and rod. The output of the housing 1 is connected to the entrance to the supersonic nozzle 4, at the exit of which a conical-shaped body 5 is placed. The device is placed at the exit of the powder container 6, inside which a bump 7 is installed at the upper bottom, shaped in the form of a cone, the apex of which is directed to the side the outlet from the tank for leveling the gas powder flow directed to the entrance to the device. The container with carbon dioxide 8, equipped with a shut-off and start valve 9, is connected by a pipe 10 with an aerator 11 located in the bottom of the container with powder.

 The device operates as follows. When the shut-off valve 9 is activated, carbon dioxide enters the powder container 6 through the aerator 11. The powder is aerated and the gas-powder mixture enters the screw channel, where it swirls. When swirling the flow of the gas-powder mixture due to centrifugal forces, cross-separation of the extinguishing powder occurs relative to the flow, and its larger particles are discarded to the wall of the housing. As a result of the friction of particles on the wall of the body, the particles of the extinguishing powder are preliminarily crushed, which is directed by the gas flow to the entrance to the supersonic nozzle 4. In the supersonic nozzle, the gas-powder mixture accelerates to a speed greater than the speed of sound and runs onto the conical body 5 installed at the exit of the supersonic nozzles, resulting in the formation of shock wave 12. The pre-ground particles of the extinguishing powder, interacting with it as a permeable barrier, are finally dispersed, transforming Touching into an aerosol. The obtained ultrafine gas-aerosol mixture with the help of nozzle 13 is formed into a stream and fed into the fire for extinguishing in a local way. The preferred consumption concentration of the powder with respect to the gas is 0.6-2.6.

 In FIG. 2 shows a variant of the device in which it is located, inside the container with fire extinguishing powder 6. In this case, the entrance of the gas-powder mixture into the screw channel of the device is closed by the membrane 14. When the shut-off and start valve 9 is activated, the pressure in the vessel 6 rises to a predetermined level, at which the membrane 14 and the gas-powder mixture enters the helical channel.

 After the gas-powder jet passes through the helical channel, the supersonic nozzle and the shock wave obtained by the ultrafine gas-aerosol mixture with the nozzle 15 having round or slit-like openings located at the level of the base of the conical body, they are formed in the form of an atomized cloud and fed into the protected room to extinguish the fire with volumetric way.

 Obtained by the claimed method and device fire extinguishing mixture - fire extinguishing aerosol - provides fire extinguishing of fires of classes A, B, C, as well as electrical installations up to 1000 V. Fire extinguishing aerosol has unique fire extinguishing properties. It is an order of magnitude more effective than traditional gas and powder fire extinguishing agents, able to phlegmatize explosive atmospheres, does not destroy the ozone layer of the earth’s atmosphere and is non-toxic at extinguishing concentrations.

 A method and apparatus for producing a fire extinguishing aerosol form the basis for the development of a new generation of fire fighting equipment - aerosol fire fighting equipment.

Possible embodiments of the invention
Option 1. Aerosol fire extinguishing vehicle. In this embodiment, the device can be installed directly on the container with a fire extinguishing powder and implemented in the form of a gun monitor or using flexible hoses can be removed from the container and used as a hand barrel.

 Option 2. Transportable and portable aerosol fire extinguishers. In this case, containers with extinguishing powder and carbon dioxide are placed on a trolley or on a wearable backpack with the device on a flexible hose.

 Option 3. The modular installation of aerosol fire extinguishing, installed permanently to protect the premises. In this case, the device is placed inside the powder container.

Sources of information
1. Isavnin M. Century. Extinguishing powder. - M.: Stroyizdat, 1983.

 2. USSR author's certificate N 917843, A 62 C 35/50, 1982

 3. USSR author's certificate N 1264954, A 62 C 35/50, 1986

 4. Baratov A.I., Vogman L.P. Fire extinguishing powder formulations. - M .: Stroyizdat, 1982.

 5. Agafonov V. V., Kopylov N. P. Aerosol fire extinguishing installations. Elements and characteristics, design, installation and operation. - M .: VNIIPO, 1999.

 6. Alikin V.N., Kuzmitsky, Stepanov A.E. Autonomous solid fuel aerosol fire extinguishing systems. - Perm, Ural Branch of the Russian Academy of Sciences, 1998.

 7. Patent WO 92/17244, A 62 D 1/00, 1992.

 8. Patent N 2115450, A 62 C 35/00, 1998.

 9. Patent N 2135236, A 62 C 3/00, 1998.

 10. Shidlovsky A.A. Fundamentals of pyrotechnics. - M.: Mechanical Engineering, 1973.

 11. Patent N 2144403, A 62 C 31/00, 1998.

 12. Abramovich G.N. Applied gas dynamics. - M.: Science, 1991.

 13. Agroskin I. I. Hydraulics. - M.-L .; State Energy Publishing House, 1964.

 14. Patent N 2135239, A 62 C 35/00, 1999.

 15. Laats MK. An experimental study of the dynamics of a dusty jet. - IFZh, 1966, 10 N 3.

 16. Alemasov V.E., Dregalin A.F., Tishin A.P. Theory of rocket engines. - M.: Mechanical Engineering, 1989.

 17. Shkolnikova R.I. Air-jet generators of acoustic vibrations for coagulation of aerosols. Acoustic journal 9, 3, 1963.

Claims (6)

 1. A method of producing a fire extinguishing mixture by aeration of a fire extinguishing powder with compressed gas supplied to the bottom of the powder container and feeding a gas-powder mixture into a nozzle and nozzles, characterized in that the gas-powder mixture is initially ground in a screw swirl, then it is dispersed in a supersonic nozzle and directed on a shock wave arising when a supersonic gas-powder flow runs onto a conical body mounted at the exit of a supersonic nozzle interacting with which as with a permeable barrier, anticipating ritelno crushed fire extinguishing powder is dispersed in an aerosol and producing ultra gas-aerosol mixture formed by the nozzles in the form of atomized cloud or a compact jet and is fed into the seat of fire. 2. A device for producing a fire extinguishing mixture containing a container with powder, equipped with a chipper, a source of compressed gas with a means of supplying it to the bottom of the container with powder, a shut-off and start valve, a cylindrical nozzle and a nozzle, characterized in that the supersonic nozzle is made in the form of an expanding a cone with an opening angle of 12-15 ^o , at the entrance to which a screw swirl is placed, made in the form of a hollow cylinder with an axisymmetrically located rod in it, around which a helical plane is formed, forming with cylindrical the core is a helical channel, and at the exit of the supersonic nozzle there is a conical body and cylindrical nozzles.  3. The device according to claim 2, characterized in that in order to obtain an atomized cloud, the cylindrical nozzles at the level of the conical body have round or slit-like openings.  4. The device according to claim 2, characterized in that carbon dioxide is used as a source of compressed gas.  5. The device according to claim 2, characterized in that the chipper is made in the form of a cone, the top of which is directed towards the outlet of the container with the powder.  6. The device according to claim 2, characterized in that the screw channel is made with a variable pitch.

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