FR2778576A1 - FIRE EXTINGUISHING DEVICE COMPRISING A THERMOCHEMICAL GAS GENERATOR - Google Patents

Abstract

The present invention relates to an extinguishing device (1) comprising a reservoir (2) for extinguishing liquid and a thermochemical gas generator (3) for misting said extinguishing liquid. The problem is to obtain the optimum operating conditions and to have a device with maximum operating safety. For this, said device (1) is such that it further comprises a mixing chamber supplied with controlled flows of gas from the generator (3) and of extinguishing liquid from the reservoir (2) and that said chamber (4 ) is connected to at least one diffuser (5) such that the pressure of the mixture of gas and extinguishing liquid in the mixing chamber (4) is between approximately 0.5 MPa and approximately 10 MPa. The device according to l The invention is preferably used for extinguishing fires in closed or semi-closed premises.

Description

The present invention relates to a fire extinguishing device.

  More particularly, it relates to a device using a thermochemical gas generator to produce a mixture of inerting gas and extinguishing liquid misted on a fire. The fires or fires considered here are essentially of two types. The first type concerns solid fires, generally of organic origin, the combustion of which takes place by the formation of embers; these fires are sometimes assimilated to surface fires. The second type concerns fires of liquids or liquefiable solids. The extinguishing device here15 considered is used in particular against fires

  developing in closed or semi-closed premises.

  Three methods are used to extinguish these

types of fires or fires.

  A first method uses gases which inhibit chain reactions of combustion. These gases are halogenated hydrocarbons such as "HALON". Extinguishing devices using such gases are very effective and efficient. However, due to their effects on the ozone layer and under the environmental pressure, some of these gases are prohibited for use or not recommended; other products or methods are sought. A second method uses inerting gases which expel oxygen and suppress the fire. These gases are, for example, carbon dioxide, nitrogen or argon. The devices that use them are heavy and require significant maintenance: liquefied gas or high pressure storage cylinders. In addition, when these devices are used in closed premises they require procedures for the evacuation of personnel who are exposed to the risk of asphyxiation for high gas rates

necessary for inerting.

  A third method is the misting of extinguishing liquid, the droplets formed act by different mechanisms. The fine droplets shield infrared radiation and reduce the heating of the surfaces subjected to this radiation, the vaporization of the extinguishing liquid constituting these droplets on the one hand absorbs heat and therefore cools the medium and on the other hand flushes out the medium. and contributes to

inerting of the environment.

  Note that the technique of extinguishing by mist differs from the spraying technique used by devices such as "sprinklers" for which the room is flooded, the fire controlled but

not necessarily off.

  Still other devices are used to carry out the vaporization of liquid. For example, patent application WO 95/00205 describes a device comprising a pyrotechnic generator whose combustion products are directed to a water tank adjoining the pyrotechnic generator. These products of combustion vaporize the water which is then entrained

on the fire.

  A first problem is to find optimal operating conditions to obtain, in a small footprint, sufficient inerting gases and effective misting of the liquid.

  of extinction in particular by the size of the droplets.

  A second problem is related to the use of a thermochemical gas generator which is subject to regulations on pyrotechnic products and objects. These regulations define procedures for classifying these products and objects in risk classes, with each of these classes being associated with rules defining in particular the operating conditions to be observed. For the widest possible use, it is desirable that the extinguishing device be classified in the class of

lowest risks.

  The fire extinguisher device according to the invention comprises a reservoir of extinguishing liquid and a thermochemical gas generator such that it also comprises a mixing chamber supplied with controlled gas flows from the thermochemical generator and extinguishing liquid from the tank and that said mixing chamber is connected to at least one diffuser such as the pressure of the gas and extinguishing liquid mixture in said mixing chamber

  is between about 0.5 MPa and about lOMPa.

  The gas flow rate, coming from the thermochemical generator, is controlled by the geometry of the propellant block of the thermochemical generator and the geometry of the orifice putting the generator in communication with the mixing chamber. The flow of extinguishing liquid from the tank is controlled by the system

  injecting liquid into the mixing chamber.

  A pipe, the length and arrangement of which are appropriate for the area to be protected, connects said mixing chamber to one or more diffusers. The number and arrangement of diffusers are adapted to the configuration of the room and the objects protected against fire. These diffusers, which are primed nozzles, regulate, depending on the incoming flow rates,

  the pressure of the mixture in the mixing chamber.

  Advantageously, the extinguishing device is such that the pressure in the mixing chamber is between approximately 2MPa and approximately 5MPa. Preferably, the pressure in the mixing chamber is around 4 MPa. Preferably the extinguishing liquid tank is arranged, at least partially, around

of the thermochemical generator.

  Advantageously, the extinguishing liquid is water-based, which is the cheapest and most effective liquid for extinguishing fires. Various additives can be added to this water, in particular to further improve its extinguishing power, to prevent freezing. In the mixing chamber, the mixture of gas and quenching liquid is saturated with quenching liquid so as to constitute a two-phase mixture comprising condensed droplets of quenching liquid. The aerodynamic shearing of these droplets when passing through the diffusers produces the misting of the

extinguishing liquid.

  Advantageously, the mixing chamber is supplied with extinguishing liquid by an injection system arranged around said mixing chamber. The system

  injection is achieved by one or more circumferential rows of holes or nozzles arranged around the mixing chamber. Preferably, this injection takes place at the upstream part of this mixing chamber.

  In a first embodiment, the communication between the thermochemical generator and the mixing chamber takes place through an orifice which makes it possible to maintain an internal pressure of the thermochemical generator which

  is greater than about twice the pressure in the mixing chamber. In this case, the orifice is said to be sonically primed and the operation of the generator 15 is decoupled from that of the mixing chamber.

  In a second embodiment, the communication between the thermochemical generator and the mixing chamber takes place through an orifice which makes it possible to maintain a slight pressure drop between the generator and the mixing chamber. In this configuration, the operation of the generator and the mixing chamber are no longer decoupled, but the pressure in the thermochemical generator is lower and the envelope of the generator may be thinner and therefore lighter. Advantageously, for these two configurations, the communication orifice between the thermochemical generator and the mixing chamber is initially closed by a cover. This cover protects the thermochemical generator from humidity and facilitates the start-up of the thermochemical generator at the time of ignition. Preferably this cover, generally metallic, is petalable to avoid projecting into the mixing chamber, then into the pipes, more or less large metal pieces risking

to plug diffusers.

  The thermochemical generator includes an ignition device whose operation is controlled by a

fire detection system.

  The thermochemical generator comprises a block of propellant contained in an envelope suitably sized and protected to withstand pressure and heat. The solid propellant chosen is such that its combustion essentially produces gases and in particular gases such as carbon dioxide, nitrogen and water vapor. The shape and dimensions of the block are adapted to obtain an operating time of a few tens of seconds to a few minutes, to

  that the device has an extended action time.

  The extinguishing liquid tank can be pressurized by an auxiliary device: for example a "sparklet" of liquid carbon dioxide or nitrogen, a permanent pressurization or an auxiliary gas generator. But preferably the thermochemical generator, described in the preceding paragraph, comprises a means of pressurizing the reservoir of the extinguishing liquid by a suitably arranged gas sample, which avoids the use of auxiliary devices and greatly simplifies the operation of the device. This means of pressurizing the extinguishing liquid tank includes a pressure reducer to regulate and stagger the pressures in the different parts

of the extinguishing device.

  Very advantageously the extinguishing liquid tank completely surrounds the thermochemical generator. According to a preferred embodiment, the extinguishing liquid reservoir also surrounds the mixing chamber situated in the extension of the

thermochemical generator.

  According to another preferred embodiment, the thermochemical generator and the mixing chamber are arranged vertically so that the extinguishing liquid surrounds, as long as possible, during operation, the thermochemical generator and

  possibly the mixing chamber.

  In a first embodiment, the mixing chamber overcomes the pyrotechnic generator and a dip tube connects the bottom of the extinguishing liquid tank to the system for injecting the liquid into said mixing chamber. This dip tube makes it possible to use almost

all the extinguishing liquid.

  In a second embodiment the generator

  thermochemical overcomes the mixing chamber.

  The control of the gas and extinguishing liquid flow rates injected into the mixing chamber and the operating pressure range of this chamber allow the desired functional optimization to be achieved: suitable rate of inerting gas and

suitable droplet sizes.

  The mist cloud produced by mixing with the extinguishing liquid and by expansion by the diffusers is "lukewarm" which on the one hand avoids thermal shocks on the materials and recondensations on the equipment and on the other hand possible burns

  personnel present near the diffusers.

  The problem of classification of the thermochemical generator can be resolved by choosing a propellant classified as low risk. But in addition, the arrangement of the extinguishing liquid reservoir around the gas generator and possibly around the mixing chamber, which constitutes a very compact assembly, solves the problems mentioned above. On the one hand, the presence of this reservoir of liquid around the thermochemical generator considerably reduces the risks of a possible explosion by external heating of this generator and therefore makes it possible to classify the device in the minimum risk class with low conditions of use. binding. On the other hand, the presence of this liquid envelope increases the thermal inertia of the device and homogenizes its temperature during operation, which makes it possible to obtain a substantially constant two-phase mixture.

  conducive to improving the final misting.

  In addition to solving the problems previously

  mentioned this device has other advantages.

  The gases produced by the combustion of the propellant block are essentially inert gases, and preexisting in nature, there is no production of halogenated gases prohibited or not recommended. In addition, the rate of gases participating in inerting being low, it is compatible with the presence of personnel in the premises. Depending on the device produced, the gases generated carry the cloud of misted water which gives it a certain dynamic which promotes extinction, in particular

hidden lights.

  Below the invention is explained in more detail

  by the description of three particular realizations,

  it is understood that these examples are not limiting.

  Figure i schematically represents a very compact embodiment in which the thermochemical generator is in the low position and is entirely

  surrounded by the extinguishing liquid tank.

  FIG. 2 likewise represents an embodiment of the invention in which the thermochemical generator

is in the high position.

  FIG. 3 schematically represents an embodiment in which the different elements are separated. Figure 1 shows a first particular embodiment of the invention. In this embodiment of the extinguishing device 1, the extinguishing liquid tank 2 completely surrounds the thermochemical generator 3 of gas in the low position and the mixing chamber 4 placed above along a same vertical axis. The communication between the thermochemical generator 3 and the mixing chamber 4 takes place through an orifice 7; this orifice is of reduced size, it has the shape and dimensions of a nozzle neck such that the pressure in the thermochemical generator 3 is approximately double that prevailing in the mixing chamber 4. Initially this orifice is closed by a cover 7 ', this cover is petalable to avoid metal splashes in the extinguishing device. The pressure of breakdown of the cover is chosen as a function of the ignition pressure of the generator 3 and of the pressure necessary to obtain the pressurization of the extinguishing liquid in the reservoir 2.5. The generator 3 comprises a block of propellant 10, in the present example is a solid block, burning in cigarettes, this block is inhibited appropriately. On the thermochemical generator 3 is mounted10 an ignition device 9 connected to a control system, not shown, this system can be electrical or mechanical. Found, mounted on this thermochemical generator, a pressurization means 11 which takes and holds gases from the thermochemical generator to pressurize the tank 2 of extinguishing liquid. The extinguishing liquid is thus injected into the mixing chamber 4 by an injection system 6 arranged all around the latter and in its upstream part. This injection system 6 comprises

  a dip tube 12 which goes almost to the bottom of the tank 2 to use all the extinguishing liquid.

  In this configuration, the flame front on the surface of the propellant changes in the same direction as the level of the free surface of the extinguishing liquid. The outlet of the mixing chamber is connected by pipes 13 of suitable dimensions to several diffusers 5, to distribute and mist in the room, the products resulting from the mixture of combustion gases and extinguishing liquid. Figure 2 shows another embodiment of

  the invention. The thermochemical generator 23 is

  above the mixing chamber 24. The extinguishing liquid reservoir 22 completely surrounds the generator 23 and only the upstream part of the mixing chamber 24, at the level of the injection system 26 for extinguishing liquid. Communication between the thermochemical generator 23 and the mixing chamber 24 takes place through a large orifice 8 so that it is not sonically initiated. This orifice creates a suitable pressure drop between the thermochemical generator and the mixing chamber. As before, this orifice 8 is closed by a seal 8 'petalable. Pipes 33 connect the outlet of the mixing chamber 24 to diffusers 25. As before, the generator 23 includes an ignition device 29 and a means of pressurizing 31 of the tank 22 of extinguishing liquid. FIG. 3 represents a less compact embodiment of the invention. In this embodiment of the extinguishing device 40, the extinguishing liquid reservoir 42 is separated from the pyrotechnic generator 43 and from the mixing chamber 44. A conduit connects the reservoir 42 of extinguishing liquid to the injection system 46 arranged around of the mixing chamber 44 which is extended by a pipe 53 ending in a diffuser 45. The thermochemical generator 43 contains a propellant block 50 with front combustion, ignited by an ignition device 49. The thermochemical generator is connected to the mixing chamber through an orifice 7, of the primed nozzle type as in the example of FIG. 1. Finally the reservoir 42 of extinguishing liquid is pressurized by an auxiliary device 51 whose operation is synchronized with that of the

  device 40 and in particular of the ignition device 49.

  Service devices such as, for example, the loading opening of the thermochemical generator, the filling opening with extinguishing liquid, any drain valves, watertight passages

  are neither detailed nor shown in these figures.

  When the fire is detected, by an appropriate system, an ignition order is transmitted to the

  ignition device 9,29,49 of the propellant block.

  This sequence can be fully automatic. It can also be triggered manually by an operator

  present on site or warned by an alarm.

  The operation of the ignition device 9,29,49 ignites the block 10,30, 50 of solid propellant, the pressure in the combustion chamber of the thermochemical generator increases until the pressure of rupture of the seal 7 ', 8 '. For compact configurations, part of the gases produced are held by the pressurization means 11, 21 and pressurize the reservoir 2.20 of extinguishing liquid. For the configuration of FIG. 3, an auxiliary generator 51 pressurizes the reservoir 42. The extinguishing liquid is expelled to the injection system 6,26,46 in the mixing chamber

4,24,44.

  The gases emerging in the mixing chamber 4,24,44 through the orifice 7,8 mix with the extinguishing liquid sprayed by the injection system 6,26,46 there is cooling of this mixture. The droplets of extinguishing liquid are entrained by the gases towards the diffusers 5,25,45. The said diffusers, 25.45 distribute the gas-liquid extinguishing mixture

  by misting it in the room to be protected.

  The propellants used in the extinguishing device according to the invention must essentially produce gases; preferably the gases produced are carbon dioxide, nitrogen from water vapor. Most propellants with reduced risk and generating non-toxic gases are suitable for this type of use; for example the propellants described in patent applications FR 2 713 632, based on an oxygenated thermoplastic binder and the oxidizing charge of which is mainly ammonium nitrate; FR 2 728 562 based on a silicone binder and whose oxidizing charge is ammonium perchlorate and sodium nitrate and FR 2 750 422 based on an oxygenated binder and whose oxidizing charge is a mixture of nitrate d ammonium and

  potassium and ammonium perchlorates.

  The propellant block has the form of a channel block

  central or preferably from a full account block-

  given the required operating times. This block is a free block suitably inhibited, this block is loaded and wedged in the structure of the thermochemical generator

and changed after operation.

  The ignition device is adapted to the shape of the block and the nature of the propellant. Its initiation can be done electrically or mechanically by a percussion device triggered automatically or

  manually after fire detection.

  The extinguishing liquid is essentially water-based. To remove certain drawbacks and further improve its performance, certain additives are added to it to increase the extinguishing power: chemical retardants, to prevent freezing: antifreeze products, etc. All these additives are known to those skilled in the art. who can select the products that adapt to the system and regulatory constraints. For a room of approximately 30m3 the extinguishing device according to the invention comprises a propellant block of approximately 4kg and a water reserve of approximately 12kg. The mixing chamber is pressurized to 4MPa and saturated with water, the temperature of the mixture is approximately 250 C. The device produces a cloud of misted water whose average droplet diameter is less than gm and whose gases lower the final oxygen rate

in the room at around 19%.

  Given the density of the products, 1.7 for the propellant, 1 for the water, in a very configuration

  compact like that described in FIG. 1, the volume occupied by the device is close to that of a Halon device of equivalent performance.

Claims (16)

Claims   1. Fire extinguishing device (1,20,40) comprising a reservoir (2,22,42) of extinguishing liquid and a thermochemical generator (3,23,43) of gas characterized in that it includes a mixing chamber (4,24,44) supplied by controlled flows of gas from the generator (3,23,43) and extinguishing liquid from the tank (2,22,42) and that said chamber ( 4,24,44) is connected to at least one diffuser (5,25,45) such that the pressure of the gas and extinguishing liquid mixture in said chamber (4, 24,44)   is between about 0.5 MPa and about lOMPa.   2. Extinguishing device according to claim 1 characterized in that the pressure in the   mixture is between about 2MPa and about 5MPa.   3. Extinguishing device according to one of   claims 1 or 2 characterized in that the tank   (2,22,) is arranged at least partially around the thermochemical generator.   4. Extinguishing device according to one of   Claims 1 to 3, characterized in that the liquid is water-based.   5. Extinguishing device according to one of   claims 1 to 4 characterized in that the mixture   gas and extinguishing liquid, in the mixing chamber   (4,24,44) is saturated with extinguishing liquid.   6. Extinguishing device according to one of   claims 1 to 5 characterized in that the   mixture (4,24,44) is supplied with extinguishing liquid by an injection system (6,26,46) arranged around   said mixing chamber (4,24,44).   7. Extinguishing device according to one of   claims 1 to 6 characterized in that the   communication between the generator (3) and the mixing chamber (4) takes place through an orifice (7) which makes it possible to maintain an internal pressure of the generator (3) which is greater than approximately twice the pressure in the mixing chamber (4).   8. Extinguishing device according to one of   claims 1 to 6 characterized in that the   communication between the generator (23) and the mixing chamber (24) is through an orifice (8) which allows to maintain a slight pressure drop between the generator   (23) and the mixing chamber (24).   9. Extinguishing device according to claim 7 or 8 characterized in that the orifice (7,8) is initially closed with a seal.   10. Extinguishing device according to one of   previous claims characterized in that the   generator (3,23,43) comprises an ignition device (9,29,49) whose operation is controlled by a fire detection system.   11. Extinguishing device according to one of   previous claims characterized in that the   generator (3,23,43) comprises a block (10,30,50) of solid propellant whose combustion provides in particular   carbon dioxide, nitrogen and water vapor.   12. Extinguishing device according to one of   previous claims characterized in that the   generator (3,23,43) comprises means for pressurizing (11,31,51) the reservoir (2,22,42) of extinguishing liquid. 13. Extinguishing device according to claim 12 characterized in that the pressurization means (11,31) is equipped with a regulator.   14. Extinguishing device according to claim 13, characterized in that the reservoir (2,22) of liquid   of extinction surrounds the generator (3.30).   15. Extinguishing device according to claim 14, characterized in that the reservoir (2) of extinguishing liquid also surrounds the mixing chamber (4) located in the extension of the communication orifice between the generator (3) and the bedroom mixture (4).   16. Extinguishing device according to claim 1,5,14 or 15, characterized in that the mixing chamber (4) surmounts the generator (3) and in that a dip tube (12) connects the bottom of the tank (2) to   injection system (6) in said mixing chamber.