EP0956883A1 - Fire extinguishing device with thermochemical gas generator - Google Patents

Abstract

The extinguisher (1) consists of a reservoir (2) of an extinguishing liquid, and a thermochemical gas generator (3) containing e.g. solid propergol which gives off carbon dioxide, nitrogen and water vapor on combustion and expels the water-based liquid in a fine spray. The gas generator is connected to a mixing chamber (4) fed by a controlled flow of gas and liquid to produce a mixture with a pressure of between about 0.5 and 10 MPa. The gas generator can be located inside or separate from the liquid reservoir.

Description

The present invention relates to a device fire extinguisher. More particularly it relates to a device using a generator thermochemical gas to produce a mixture of gases blanket and misty extinguishing liquid on a fire.

The fires or fires considered here are basically of two types. The first type concerns solid fires, generally of organic origin, whose combustion takes place by the formation of embers; these fires are sometimes assimilated to fires of area. The second type concerns fires of liquids or liquefiable solids. The extinguishing system according to the invention finds its justification in several types of application: it can be used against fires developing in closed or semi-closed rooms, but also in the case of a fire caused by an explosion, requiring a time of very short operation. Likewise, it is suitable for extinction of aircraft engine fires requiring high flow rates and a blast effect, and protection of objects to replace carbon dioxide currently in force.

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

A first method uses gases which inhibit reactions in the combustion chain. These gases are halogenated hydrocarbons such as "HALON". The fire extinguishers using such gases are very efficient and effective. But, due to their effects on the ozone layer and under the environmentalist push some of these gases are prohibited for use or not recommended; other products or methods are research.

A second method uses inerting gases which expel oxygen and smother the fire. These gases are for example carbon dioxide, nitrogen or argon. The devices that use them are heavy and require significant maintenance: bottles storage of liquefied gases or under high pressure. Of more, when these devices are implemented in closed premises they require procedures for the evacuation of personnel who are exposed to risk of suffocation for high gas rates necessary for inerting.

A third method is the misting of liquid extinction, the droplets formed act by different mechanisms. Fine droplets screen infrared radiation and reduce overheating surfaces subject to this radiation, vaporization extinguishing liquid constituting these droplets on the one hand absorbs heat and therefore cools the medium and on the other hand flushes out oxygen and helps inerting of the environment.

Note that the technique of extinction by misting differs from 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 for spray the liquid. For example the patent application WO 95/00205 describes a device comprising a pyrotechnic generator whose 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 conditions operating conditions to obtain, in a small footprint, quantity of inert gases sufficient 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 the product and object regulations pyrotechnics. These regulations define procedures for classifying these products and objects in risk classes, to each of these classes are associated with rules defining in particular the operating conditions to be observed. For a widest exploitation it is desirable that the fire extinguisher is classified in the class of lowest risks.

The fire extinguisher according to the invention includes a liquid reservoir and a thermochemical gas generator such that it also has a supplied mixing chamber by controlled gas flows from the generator thermochemical 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 mixture and extinguishing liquid in said mixing chamber is between about 0.5MPa and about 10MPa.

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

Piping, the length and layout of which are appropriate for the area to be protected, connects said mixing chamber with one or more diffusers. The number and arrangement of diffusers are adapted to configuration of the room and objects protected against the fire. These are the diffusers, which are nozzles initiated, which regulate, according to the incoming flows, the pressure of the mixture in the mixing chamber.

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

Preferably the liquid tank extinguisher is arranged, at least partially, around of the thermochemical generator.

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

Advantageously, the extinguishing liquid is based water which is the cheapest and most liquid efficient for extinguishing fires. At this water we can add different additives especially for further improve its extinguishing power, avoid gel.

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

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

In a first realization the communication between the thermochemical generator and the mixing is done by an orifice which allows to maintain an internal pressure of the thermochemical generator which is greater than about double the pressure in the mixing chamber. In this case, the orifice is said sonically initiated and generator operation is decoupled from that of the mixing chamber.

In a second realization the communication between the thermochemical generator and the mixing is done by an orifice which allows to maintain a slight pressure drop between the generator and the mixing chamber. In this configuration the generator and mixing chamber operation are no longer decoupled, but the pressure in the thermochemical generator is weaker and the envelope of the generator may be thinner and therefore more slight.

Advantageously, for these two configurations, the communication port between the generator thermochemical and the mixing chamber is initially closed with a seal. This seal protects the thermochemical humidity generator and facilitates activation of the thermochemical generator at the time of ignition. Preferably this seal, in general metallic, is petalable to avoid projecting into the mixing chamber, then in the pipes, more or less significant metal pieces risking to plug diffusers.

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

The thermochemical generator includes a block of propellant contained in an envelope suitably sized and protected to withstand pressure and in the heat. The solid propellant chosen is such that its combustion mainly 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 extinguishant tank can be pressurized by an auxiliary device: for example a "sparklet" of liquid carbon dioxide or nitrogen, a permanent pressurization or an auxiliary generator of gas. But preferably the generator thermochemical, described in the previous paragraph, includes a means of pressurizing the liquid reservoir extinguishing by appropriately removing gas arranged, which avoids the use of devices and greatly simplifies the operation of the device. This means of pressurizing the reservoir of extinguishing liquid has a regulator to regulate and stagger the pressures in the different parts of the extinguishing device.

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

According to another preferred embodiment, the generator thermochemical and the mixing chamber are arranged vertically so that the extinguishing liquid surrounds, as long as possible, during the 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 liquid injection system in said chamber mixed. This dip tube makes it possible to use almost all the extinguishing liquid.

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

Control of gas and liquid flow rates extinguisher injected into the mixing chamber and the operating pressure range of this chamber allow for functional optimization sought: suitable rate of inerting gas and suitable droplet sizes.

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

The generator classification problem thermochemical can be solved by choosing a propellant classified as low risk. But in addition, the arrangement of the extinguishing liquid tank around of the gas generator and possibly around the mixing chamber, which constitutes a very compact, solves the problems mentioned above. Of a hand, the presence of this liquid reservoir around the thermochemical generator significantly reduces risk of a possible explosion due to heating outside of this generator and therefore allows to store the device in minimum risk class with light conditions of use. Else apart the presence of this liquid envelope increases the thermal inertia of the device and homogenizes its temperature during operation which allows 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 block propellants are essentially inert gases, and preexisting in nature, there is no production of halogenated gases prohibited or not recommended. Plus the rate gases which participate in the inerting being weak, it is compatible with the presence of personnel in the local.

Depending on the device produced, the gases generated carry the cloud of misted water which gives it a certain dynamic that 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.

FIG. 1 schematically represents a very compact embodiment in which the thermochemical generator is in the low position and is entirely surrounded by the reservoir of extinguishing liquid.

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 twice 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 tank 2.

The generator 3 comprises a propellant block 10, in the present example it is a full block, burning in cigarettes, 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. 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 practically 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 liquid injection system 26 of extinction. 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.

Bondage devices such as, for example the loading port of the thermochemical generator, the extinguisher filling port, possible drain valves, watertight passages are neither detailed nor shown in these figures.

When the fire is detected, by a system appropriate, an ignition order is sent to the ignition device 9,29,49 of the propellant block. This sequence can be fully automatic. She 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 solid propellant block 10.30.50, the pressure in the generator combustion chamber thermochemical increases up to the rupture pressure from the cover 7 ', 8'. For compact configurations part of the gases produced are held by means of pressurize 11, 21 and pressurize the tank 2.20 of extinguishing liquid. For the configuration of the FIG. 3 an auxiliary generator 51 pressurizes the tank 42. The extinguishing liquid is expelled to the 6,26,46 injection system in the mixing chamber 4,24,44.

The gases emerging in the mixing chamber 4,24,44 through port 7,8 mix with liquid extinguishing sprayed by the injection system 6,26,46 there is cooling of this mixture. The droplets of extinguishing liquid are entrained by gases to diffusers 5,25,45. The so-called diffusers 5,25,45 distribute the gas-liquid extinguishing mixture by misting it in the room to be protected.

The propellants used in the device according to the invention must essentially produce gases; preferably the gases produced are carbon dioxide, nitrogen vapor of water. Most of the lower risk propellants and generating non-toxic gases suitable for this kind of use; for example the propellants described in patent applications FR 2 713 632, based on a binder oxygenated thermoplastic with an oxidizing charge mainly ammonium nitrate; FR 2,728,562 to base of 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 charge oxidant is a mixture of ammonium nitrate and potassium and ammonium perchlorates.

The propellant block has the form of a channel block central or preferably a full block taking into account 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. His initiation can be done electrically or mechanically by a percussion device triggered automatically or manually after fire detection.

The extinguishing liquid is essentially based of water. To remove some inconvenience and further improve its performance we add some additives to increase the extinguishing power: chemical retardants, to avoid freezing: products antifreeze ... All these additives are known to the man of profession of the field which can select the products which adapt to the device and constraints regulatory.

For a room of around 30m ^3, the extinguishing device according to the invention comprises a propellant block of around 4kg and a water reserve of around 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 200 µm and whose gases lower the final oxygen level in the room to around 19%.

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

Claims (17)

Fire extinguisher (1,20,40) comprising a reservoir (2,22,42) of liquid and a thermochemical generator (3,23,43) gas characterized in that it comprises a mixture (4,24,44) fed by controlled flow rates of gas from generator (3,23,43) and 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 as the pressure of the gas mixture and extinguishing liquid in said chamber (4,24,44) is between about 0.5MPa and about 10MPa. Extinguishing device according to claim 1 characterized in that the pressure in the chamber mixture is between about 2MPa and about 5MPa. 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. Extinguishing device according to one of Claims 1 to 3, characterized in that the liquid is water-based. 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. 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). Extinguishing device according to one of claims 1 to 6 characterized in that the communication between the generator (3) and the mixing (4) is done by an orifice (7) which allows maintain an internal pressure of the generator (3) which is greater than about double the pressure in the mixing chamber (4). Extinguishing device according to one of claims 1 to 6 characterized in that the communication between the generator (23) and the mixing (24) is done by an orifice (8) which allows maintain a slight pressure drop between the generator (23) and the mixing chamber (24). Extinguishing device according to claim 7 or 8 characterized in that the orifice (7,8) is initially closed with a seal. Extinguishing device according to one of previous claims characterized in that the generator (3,23,43) includes an ignition device (9,29,49) whose operation is controlled by a fire detection system. 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. Extinguishing device according to one of previous claims characterized in that the generator (3,23,43) has a pressurization means (11,31,51) of the reservoir (2,22,42) of liquid of extinction. Extinguishing device according to claim 12 characterized in that the pressurizing means (11,31) is equipped with a regulator. Extinguishing device according to claim 13, characterized in that the liquid reservoir (2,22) of extinction surrounds the generator (3.30). Extinguishing device according to claim 14, characterized in that the liquid reservoir (2) also surrounds the mixing chamber (4) located in the extension of the orifice of communication between the generator (3) and the mixture (4). Extinguishing device according to claim 1,5,14 or 15, characterized in that the mixture (4) overcomes the generator (3) and in that a dip tube (12) connects the bottom of the tank (2) to the injection system (6) in said mixing chamber. Extinguishing device according to one of claims 1 or 2 characterized in that the tank (2,22) is arranged in the extension of the generator thermochemical.

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