EP0956883B1 - Fire extinguishing device with thermochemical gas generator - Google Patents

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 fogging liquid mist on a fire.

The fires or fires considered here are essentially of two types. The first type concerns fires of solids, generally of organic origin, whose combustion is done by the formation of embers; these fires are sometimes comparable to surface fires. The second type concerns fires of liquids or liquefiable solids. The extinguishing device according to the invention finds its justification in several types of application: it can be used against fires developing in closed or semi-closed premises, but also in the case of a fire caused by an explosion , requiring a very short running time. Likewise, it is suitable for extinguishing aircraft engine fires requiring high flow rates and a blast effect, and for protecting objects to replace the current carbon dioxide.

Three methods are used to extinguish these types of fires or fires.

A first method uses gases that inhibit the chain reactions of combustion. These gases are halogenated hydrocarbons such as "HALON". The extinguishing devices using such gases are very efficient and effective. But, because of their effects on the ozone layer and under the environmental push, some of these gases are prohibited to use or not recommended; other products or methods are sought.

A second method uses inert gases that drive out oxygen and quell 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 storage bottles or high pressure. In addition, when these devices are implemented in closed rooms they require procedures for evacuation of personnel who are exposed to risks of asphyxiation for the high levels of gas required for inerting.

A third method is the misting of the extinguishing liquid, the droplets formed act by different mechanisms. The fine droplets shield the 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 thus cools the medium and on the other hand hunt oxygen and contributes to the inerting of the medium.

Note that the technique of extinction by misting differs from the spraying technique used by devices such as "sprinklers" for which the room is flooded, fire controlled but not necessarily extinguished.

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

The document DE 298 13 961 U1 discloses an extinguishing device comprising an extinguishing liquid reservoir, a thermochemical gas generator and a mixing chamber.

A first problem is to find optimal operating conditions to obtain, in a small space, inerting gases in sufficient quantity and efficient misting of the extinguishing liquid, in particular by the size of the droplets.

A second problem is related to the use of a thermochemical gas generator that is subject to regulations on products and pyrotechnic objects. This regulation defines procedures allowing to classify these products and objects in risk classes, to each of these classes are associated rules defining in particular the operating conditions to be respected. For the widest operation, it is desirable that the extinguishing device be classified in the lowest risk category.

The fire extinguishing device according to the invention comprises an extinguishing liquid reservoir, a thermochemical gas generator, a mixing chamber fed by controlled flow rates (see the paragraph below) of gas from the thermochemical generator and extinguishing liquid from the tank. Said mixing chamber is connected to at least one diffuser, said at least one diffuser is sized to adjust, as a function of the inflow, the pressure of the gas and liquid extinguishing mixture in said mixing chamber between about 0.5 MPa and about 10MPa.

The flow of gas from the thermochemical generator is controlled by the geometry of the propellant block of the thermochemical generator and the geometry of the orifice bringing the generator in communication with the mixing chamber. The flow of extinguishing liquid from the reservoir is controlled by the liquid injection system in the mixing chamber.

Piping, whose length and arrangement are appropriate to the area to be protected, connects said mixing chamber to one or more diffusers. The number and arrangement of the diffusers are adapted to the configuration of the premises and objects protected against fire. It is these diffusers, which are primed nozzles, which regulate, as a function of the inflow, the pressure of the mixture in the mixing chamber.

Advantageously, the extinguishing device is such that the pressure in the mixing chamber is between about 2 MPa and about 5 MPa. Preferably, the pressure in the mixing chamber is approximately 4 MPa.

Preferably the extinguishing liquid reservoir is arranged, at least partially, around the thermochemical generator.

According to another embodiment of the invention, the reservoir is arranged in the extension of the thermochemical generator.

Advantageously, the extinguishing liquid is based on water, which is the cheapest and most effective liquid for extinguishing fires. To this water can be added various additives, especially for further improve its extinguishing power, avoid freezing.

In the mixing chamber, the gas and liquid extinguishing mixture is saturated with extinguishing liquid so as to form a biphasic mixture comprising condensed droplets of extinguishing liquid. The aerodynamic shear of these droplets during the passage in the diffusers produces the misting of the extinguishing liquid.

Advantageously, the mixing chamber is supplied with extinguishing liquid by an injection system disposed around said mixing chamber. The injection system is made by one or more circumferential rows of holes or nozzles disposed around the mixing chamber. Preferably, this injection is done at the upstream part of this mixing chamber.

In a first embodiment, the communication between the thermochemical generator and the mixing chamber is via an orifice which makes it possible to maintain an internal pressure of the thermochemical generator which is greater than approximately twice the pressure in the mixing chamber. In this case, the orifice is said sonically initiated and the operation of the generator is decoupled from that of the mixing chamber.

In a second embodiment, the communication between the thermochemical generator and the mixing chamber is via 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 generator envelope 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 lid. This cover protects the thermochemical generator from moisture and facilitates the setting in regime of the thermochemical generator at the time of the ignition. Preferably this seal, generally metallic, is petalable to avoid projecting into the mixing chamber, and then into the pipes, metal pieces more or less important clogging of the diffusers.

The thermochemical generator comprises an ignition device whose operation is controlled by a fire detection system.

The thermochemical generator has a propellant block contained in a suitably dimensioned envelope and protected to withstand pressure and heat. The solid propellant chosen is such that its combustion produces essentially 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, so that the device has an extended action time.

The extinguishing liquid reservoir may 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 means for pressurizing the reservoir of the extinguishing liquid by a gas sampling suitably arranged, which avoids the use of auxiliary devices and greatly simplifies the operation of the device. This means of pressurizing the extinguishing liquid reservoir comprises an expander for regulating and staggering 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 quenching liquid tank also surrounds the mixing chamber located 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, for as long as possible during operation, the thermochemical generator and optionally the mixing chamber.

In a first embodiment the mixing chamber overcomes the pyrotechnic generator and a dip tube connects the bottom of the quench liquid reservoir to the liquid injection system in said mixing chamber. This dip tube makes it possible to use almost all the extinguishing liquid.

In a second embodiment, the thermochemical generator overcomes the mixing chamber.

Controlling the flow rates of gas and extinguishing liquid injected into the mixing chamber and the operating pressure range of this chamber make it possible to achieve the desired functional optimization: suitable rate of inerting gas and appropriate sizes of the droplets.

The cloud of misting produced by mixing with the extinguishing liquid and by expansion by the diffusers is "lukewarm" which avoids on the one hand the thermal shocks on equipment and recondensations on the equipment and on the other hand of possible burns of personnel present near the broadcasters.

The classification problem of the thermochemical generator can be solved by the choice of a propellant classified as low risk. But in addition, the arrangement of the extinguishing liquid tank around the gas generator and possibly around the mixing chamber, which is a very compact assembly, solves the problems mentioned above. On the one hand, the presence of this liquid reservoir around the thermochemical generator considerably reduces the risks of a possible explosion by external heating of this generator and thus allows the device to be stored in a minimum risk class with little use conditions. 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 that is favorable for improving the final misting.

In addition to the solution of the aforementioned problems this device has other advantages.

The gases produced by the combustion of the propellant block are essentially inert gases, and existing in nature, there is no production of halogenated gases prohibited or discouraged. In addition the rate of gases that participate in inerting being low, it is compatible with the presence of staff in the room.

Depending on the device made, the generated gases carry the cloud of misted water which gives it a certain dynamic that promotes extinction, including hidden fires.

Below the invention is explained in more detail by the description of three particular embodiments, it is understood that these examples are not limiting.

The figure 1 schematically represents a very compact embodiment in which the thermochemical generator is in a low position and is completely surrounded by the extinguishing liquid reservoir.

The figure 2 represents, likewise, an embodiment of the invention in which the thermochemical generator is in the up position.

The figure 3 schematically represents an embodiment in which the different elements are separated.

The figure 1 represents a first particular embodiment of the invention. In this embodiment of the extinguishing device 1, the extinguishing liquid reservoir 2 completely surrounds the thermochemical generator 3 of gas in the down position and the chamber mixing 4 placed above on the same vertical axis. The communication between the thermochemical generator 3 and the mixing chamber 4 is via 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 about twice that prevailing in the mixing chamber 4. Initially this orifice is closed by a operculum 7 ', this seal is petalable to avoid splashing metal in the extinguishing device. The breakdown pressure of the lid is chosen as a function of the ignition pressure of the generator 3 and the pressure necessary to obtain the pressurization of the extinguishing liquid in the tank 2.

The generator 3 comprises a propellant block 10, in the present example it is a solid block, burning in a cigarette, this block is appropriately inhibited. On the thermochemical generator 3 is mounted an ignition device 9 connected to a control system, not shown, this system can be electrical or mechanical. There is mounted on this thermochemical generator, a pressurizing means 11 which takes and holds gases of the thermochemical generator for pressurizing the reservoir 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 virtually 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 moves 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 dimensions suitable for several diffusers 5, for distributing and misting in the room, the products resulting from the mixing of the combustion gases and the extinguishing liquid.

The figure 2 represents another embodiment of the invention. The thermochemical generator 23 is above the mixing chamber 24. The extinction liquid reservoir 22 completely surrounds the generator 23 and only the upstream portion of the mixing chamber 24, at the level of the liquid injection system 26 extinction. The communication between the thermochemical generator 23 and the mixing chamber 24 is through a wide 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 previously, this orifice 8 is closed by an opal 8 'petalable. Pipes 33 connect the outlet of the mixing chamber 24 to diffusers 25. As previously the generator 23 comprises an ignition device 29 and a pressurizing means 31 of the reservoir 22 of extinguishing liquid.

The figure 3 represents a less compact embodiment of the invention. In this embodiment of the extinguishing device 40, the quenching liquid reservoir 42 is separated from the pyrotechnic generator 43 and the mixing chamber 44. A duct connects the quench liquid reservoir 42 to the injection system 46 placed around it the mixing chamber 44 which is extended by a pipe 53 terminating in a diffuser 45. The thermochemical generator 43 contains a propellant block 50 with a front combustion, ignited by an ignition device 49. The generator thermochemical is connected to the mixing chamber through an orifice 7, the type of nozzle initiated as in the example of the figure 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.

Servicing devices such as, for example the charging orifice of the thermochemical generator, the filling orifice in extinguishing liquid, any purge valves, sealed passages are neither detailed nor shown in these figures.

When the fire is detected, by a suitable system, an ignition command 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 the scene 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 up to the rupture pressure of the lid 7 ', 8 . For compact configurations, part of the gases produced are held by the pressurizing means 11, 21 and pressurize the reservoir 2.20 of extinguishing liquid. For the configuration of the figure 3 an auxiliary generator 51 pressurizes the tank 42. The extinguishing liquid is driven to the injection system 6.26.46 in the mixing chamber 4.24,44.

The gases opening into the mixing chamber 4,24,44 through the orifice 7,8 are mixed with the extinguishing liquid sprayed by the injection system 6.26.46 cooling of this mixture. The droplets of extinguishing liquid are entrained by the gases towards the diffusers 5,25,45. The said diffusers 5.25.45 distribute the gas-liquid extinction 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; preferentially, the gases produced are carbon dioxide, nitrogen and water vapor. Most low-risk propellants that generate non-toxic gases are suitable for this type of use; for example the propellants described in the patent applications FR 2,713,632 based on an oxygenated thermoplastic binder and whose oxidizing charge is predominantly 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 ammonium nitrate and potassium perchlorates and ammonium.

The propellant block has the shape of a central channel block or preferably of a solid block given the required operating times. This block is a free block suitably inhibited, this block is loaded and stalled 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 detection of the fire.

The extinguishing liquid is essentially water-based. To remove some disadvantages and further improve its performance is added certain additives to increase the extinguishing power: chemical retardants, to avoid freezing: anti-freeze products ... All these additives are known to those skilled in the art who can select products that adapt to the device and regulatory constraints.

For a room of about 30m ³ the extinguishing device according to the invention comprises a propellant block of about 4kg and a water reserve of about 12kg. The mixing chamber is pressurized to 4 MPa and saturated with water, the temperature of the mixture is about 250 ° C. The device produces a cloud of misted water whose average droplet diameter is less than 200 .mu.m and whose gases lower the final rate of oxygen in the room to about 19%.

Given the density of products, 1.7 for propellant, 1 for water, in a very compact configuration such as that described in figure 1 , the volume occupied by the device is close to that of a Halon device of equivalent performance.

Claims (17)

1. A fire extinguisher device (1, 20, 40) comprising an extinction liquid reservoir (2, 22, 42), a thermochemical gas generator (3, 23, 43), and a mixing chamber (4, 24, 44) fed with a controlled flow of gas coming from said generator (3, 23, 43) and a controlled flow of extinction liquid coming from said reservoir (2, 22, 42), and said chamber (4, 24, 44) being connected to at least one outlet nozzle (5, 25, 45), said fire extinguisher device (1, 20, 40) being characterized in that:

   the flow of gas is controlled by the geometrical shape of the block of propellant of said thermochemical gas generator (3, 23, 43) and by the geometrical shape of an orifice (7, 8) putting said generator (3, 23, 43) into communication with said mixing chamber (4, 24, 44);

   the flow of extinction liquid is controlled by an injection system (6, 26, 46) for injecting the liquid into said mixing chamber (4, 24, 44); and

   said at least one outlet nozzle (5, 25, 45) is dimensioned to set, as a function of the incoming controlled flows, the pressure of the mixture of gas and of extinction liquid in said mixing chamber (4, 24, 44) in the range about 0.5 MPa to about 10 MPa.
2. The extinguisher device according to claim 1, characterized in that the pressure in said mixing chamber (4, 24, 44) lies in the range about 2 MPa to about 5 MPa.
3. The extinguisher device according to claim 1 or claim 2, characterized in that the reservoir (2, 22) is disposed at least in part around the themochemical generator (3, 23).
4. The extinguisher device according to any one of claims 1 to 3, characterized in that the extinction liquid is based on water.
5. The extinguisher device according to any one of claims 1 to 4, characterized in that the mixture of gas and of extinction liquid in the mixing chamber (4, 24, 44) is saturated with extinction liquid.
6. The extinguisher device according to any one of claims 1 to 5, characterized in that the mixing chamber (4, 24, 44) is fed with extinction liquid by said injection system (6, 26, 46) that is disposed around said mixing chamber (4, 24, 44).
7. The extinguisher device according to any one of claims 1 to 6, characterized in that the communication between said generator (3) and said mixing chamber (4) takes place via an orifice (7) that makes it possible to maintain an internal pressure in the generator (3) that is greater than about twice the pressure in the mixing chamber (4).
8. The extinguisher device according to any one of claims 1 to 6, characterized in that the communication between said generator (23) and said mixing chamber (24) takes place via an orifice (8) that makes it possible to maintain a small pressure drop between said generator (23) and said mixing chamber (24).
9. The extinguisher device according to claim 7 or claim 8, characterized in that the orifice (7, 8) is initially closed off by a seal.
10. The extinguisher device according to any one of claims 1 to 9, characterized in that the generator (3, 23, 43) is provided with an ignition device (9, 29 49) that is itself caused to operate by a fire detection system.
11. The extinguisher device according to any one of claims 1 to 10, characterized in that the generator (3, 23, 43) included a block of solid propellant (10, 30, 50), combustion of which delivers, in particular, carbon dioxyde, nitrogen, and steam.
12. The extinguisher device according to any one of claims 1 to 11, characterized in that the generator (3, 23, 43) includes pressurization means (11, 31, 51) for pressurizing the extinction liquid reservoir (2, 22, 42).
13. The extinguisher device according to claim 12, characterized in that the pressurization means (11, 31) are equipped with a pressure-reducing valve.
14. The extinguisher according to claim 13, characterized in that the extinction liquid reservoir (2, 22) surrounds the generator (3, 23).
15. The extinguisher device according to claim 14, characterized in that said extinction liquid reservoir (2) also surrounds the mixing chamber (4) that is situated in line with the orifice (7) via which said generator (3) and said mixing chamber (4) communicate.
16. The extinguisher device according to any one of claims 1, 5, 14, or 15, characterized in that the mixing chamber (4) overlies the generator (3) and in that a dip tube (12) connects the bottom of the reservoir (2) to the injection system (6) in said mixing chamber (4).
17. The extinguisher device according to claim 1 or claim 2, characterized in that the extinction liquid reservoir is disposed in line with the thermochemical generator.

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