WO2004039455A1

WO2004039455A1 - System of fire suppression in fuel tank of vehicle or airplane

Info

Publication number: WO2004039455A1
Application number: PCT/IL2003/000881
Authority: WO
Inventors: Josef Turner; Alexander Levin
Original assignee: Josef Turner; Alexander Levin
Priority date: 2002-10-29
Filing date: 2003-10-27
Publication date: 2004-05-13
Also published as: AU2003278568A1; IL152535A0

Abstract

The proposed fire suppression system can be classified as a passive system, i.e. it does not include application of special mechanical means, sensors and gas generator devices in case of fire. This system provides constant presence of fire suppressing powder or microscopic encapsulated particles in the entire volume of fuel found in the fuel tank and it prevents fire spreading as a result of an accident. Blast or impacting ballistic threats. At the same time, the system also includes a sub-unit for the separation of the fire suppressing powder or microscopic encapsulated particles from the fuel itself when it flows into the vehicle or airplane engine. In addition, the proposed system is provided with another sub-unit, which sustains uniform and homogeneous distribution of the powder or microscopic encapsulated particles of the fire suppression substance in the entire volume of the fuel in the fuel tank.

Description

SYSTEM OF FIRE SUPPRESSION IN FUEL TANK OF VEHICLE OR AIRPLANE

Technical Field

This invention relates to the field of fire suppression systems intended at preventing the spreading of fire in cases of structural failure of fuel tanks installed in military or civil vehicle such as tanks, buses, etc. or airplanes, as well as preventing damages to the surrounding area.

The structural failure can be caused by impacting ballistic threats without exploding, electrical sparks in a fuel tank or when fuel is coming in contact with hot fragments - all as a result of accidents and sabotage. A significant portion of all combat losses in aviation has been caused due to fires and as a result of fuel spreading and inflammation.

Background Art

There are several basic requirements from fire suppression systems installed inside or outside a fuel tank of a military /civil vehicle or airplane:

1. The system can be integrated into an existing fuel tank without any significant structural modification.

2. The system of fire suppression does not cause any damage to the structure of the fuel tank in the process of its operation.

3. The system of fire suppression can be easily replaced after its activation.

4. The system of fire suppression is activated for a very short time.

5. The system occupies a small space.

There are three main types of fire suppression methods:

1. By significant diminution of oxygen concentration in the fire zone;

2. By cooling the fire zone;

3. By using chemical substances, which interrupt the combustion process.

A common active fire-suppression system includes a unit with fire suppression materials. This unit should be installed in the internal space of the fuel tank or positioned externally. The fire suppression material is dispersed in the tank space by a signal/command from suitable sensors, which activate in turn a pyrotechnical sub- unit. Dry powders as sodium bicarbonate or diammonium acidic phosphate, nitrogen or carbon dioxide, liquid or gaseous halocarbons and water can be used for fire suppression. However, maintainance of such fire suppression systems is very costly and requires constant attention. Another disadvantage is that such systems cannot prevent fire in cases of crashing and fuel spreading in the surrounding area.

There are several U.S. patents describing different systems of fire suppression in fuel tanks of vehicles or airplanes.

Detailed analysis of requirements for fire suppression systems applied in aviation is presented in U.S. Patent No.5 826 664. U.S. Patent No. 5 826 664 proposes a fire and explosion suppression system, which is mounted externally on a fuel tank and which injects a supressant medium into the fuel tank via an opening in the fuel tank wall. The fire and explosion suppression system includes a container for housing a suppressant medium. Besides, there is a removable opening connected to the predefined opening in the tank wall. The fire and explosion suppression system also includes an actuator, such as a detonator, for activating the suppressant medium upon detection of fire or explosion within the tank. The fire and explosion suppression system includes in addition a reclosable valve for sealing the predefined opening in the tank wall.

U.S. Patent No, 5 762 148 describes a fixed hollow panel, either channeled or unchanneled internally with extinguishant sealed inside, mounted on the exterior surfaces of a highway vehicle or airplane fuel tank. When the vehicle or airplane on which this device is mounted is impacted in an accident, and the resulting impact deforms or ruptures the fuel tank, the attached device is also ruptured and releases the extinguishant contained inside the device. This is intended at extinguishing fires or inerting against potential fires in the vicinity of the fuel tank, where splashing or misting fuels may come in contact with sparks, hot fragments or other ignition sources for a brief instant, hence protecting against accident-induced vehicle or airplane fires in a simple, lightweight and low cost manner.

Each bottle of this suppression system also generally requires a separate ignition system for firing a pyrotechnic actuator (such as gas generator or squib) that overpressurizes the suppressor bottle so as to burst a scored frangible disk in the delivery neck of the bottle, thereby releasing the agent.

As a result, the possibility of an inadvertent short or "spark" firing the pyrotechnic actuator and accidentally releasing the agent into the tank is increased. As will be apparent, the accidental ignition of even a single bottle could cause significant structural damage to the tank if the tank was full at the time. Even if the tank wasn't damaged, it would be necessary to open the fuel tank to replace the discharged bottle, often a time-consuming activity given the limited access to most fuel tanks and the likelihood of creating leaks when the tank is resealed.

In order to achieve accessibility to the fire and explosion suppression system, it has been proposed to apply externally mounted suppressant delivery systems.

These fire and explosion suppression systems are based on penetration through the tank walls in case of fire and the following delivery of suppression medium into the internal space of the fuel tank. Examples of such fire and explosion suppression systems include those described in U.S. Patent No. 4 702 322 (the '322 patent) and U.S. Patent No. 5 031701 (the 701 patent). The system presented in the '322 patent includes an externally mounted fire and explosion suppression device incoφorating a bottle of pressurized fluid suppressant agent. The pressurized bottle has a primary duct ending in a seal disposed against the exterior surface of a tank wall. The fire and explosion suppressant system of the '322 patent also includes a pyrotechnic charge disposed within a secondary duct. The secondary duct is oriented at an angle to the primary duct in a way that actuation of the pyrotechnic charge will cut through the seal at the end of the first duct. As a result, the fire and explosion suppression system of the '322 patent can directly inject the suppressant into the fuel tank without requiring a distribution hose to be pressurized. Typically, the pyrotechnic charge is actuated by a flash detection device or another sensor, which, in turn, is activated by fire or explosion within the tank to rupture the tank wall, and release the suppressant into the tank.

However, the systems described in the '322 and 701 patents, suffer from a number of drawbacks. These drawbacks include necessity to perforate the tank wall in order to deliver the suppressant. As a result, the opening (or openings) in the tank wall should be repaired.

U.S. Patent No. 4 132 271 describes a military vehicle or aiφlane equipped with a hollow panel containing a fire suppressant, the panel being located directly inboard from one of the vehicle or aiφlane fuel tanks, whereby enemy projectiles fired into the tank also penetrate the panel; a fire suppressant sprays out of the hole formed by the projectile, thereby preventing the formation or extinguishing of a potential fireball within the vehicle or aiφlane before it can grow into a massive holocaust of lethal proportions. A foraminous screen is positioned on the inboard face of the panel to prevent the panel from fragmenting as the suppressant enlarges the hole formed by the projectile.

Disclosure of Invention

The proposed system of fire suppression for fuel tanks with fuel of low volatility (like kerosene) meets all requirements described above. This system can be classified as a passive system, i.e. it does not include application of special mechanical and pyrotechnic means or any kind of sensors in a case of fire. At the same time, the proposed system can demonstrate implementation of the first and third principles of fire suppression, which have been described in the background of this invention.

This system provides constant presence of fire suppressing powder or microscopic encapsulated particles in the entire volume of fuel in the fuel tank and it prevents fire spreading as a result of an accident, blast or impacting ballistic threats. At the same time, the system includes also a sub-unit for separating the fire suppressing powder or microscopic encapsulated particles from the fuel itself when it is supplied to the engine of a vehicle or aiφlane. Furthermore, the system can be provided with another sub-unit, which sustains unified distribution of the powder or encapsulated particles of the fire suppression substance in the entire volume of the fuel existing in the fuel tank.

The system can be widely used in military and civil vehicles or aiφlanes.

The fuel tank can be provided with inlet and outlet connections for charging and discharging fire suppressing powder or microscopic encapsulated particles.

Preferable size of the powder or microscopic encapsulated particles is 20 ÷ 100 microns.

If the fire suppressing powder can be dissolved in small amounts of water contained in the fuel (as in the case of sodium bicarbonate), then the fuel tank is provided with a special cartridge with desiccant (for example - silicagel), which ensures desiccation of the fuel.

Mixing the powder or microscopic encapsulated particles in the fuel can be performed by a set of ultrasound transducers installed in the bottom section of the fuel tank and/or by an impeller with a drive situated outside the fuel tank. In the latter case, the fuel tank is provided with a proper stuffing box for the impeller shaft. There is also a possibility of obtaining good mixing by strong jets of fuel from nozzles.

Operation of these mixing sub-units can be regulated according to measured concentrations of fire suppressing powder or microscopic encapsulated particles in different places of the fuel tank. Such measuring can be performed, for example, on the base of dielectric characteristics in these places, or a laser technology, or acoustic sensors.

Separation of the powder or microscopic encapsulated particles from the fuel, when it is delivered into an engine, is performed by a centrifugal separator installed externally to the fuel tank, or by filters installed in the lower section of the fuel tank. In the case of application of the centrifugal separator, it is possible to install an auxiliary self-cleaning filter, which is placed on the line communicating the centrifugal separator with the engine. This auxiliary self-cleaning filter ensures complete cleaning the fuel from particles of the fire suppressing powder, whereas concentrated suspension of the fire suppressing powder from this auxiliary filter is returned into the fuel tank or into an auxiliary vessel.

In the case of application of the centrifugal separator, a concentrated suspension of the fire suppressing powder or microscopic encapsulated particles from this separator is returned into the fuel tank or accumulated in the auxiliary vessel for following charging into the fuel tank when it is filled with new portion of fuel.

Besides, such design provides possibility to mix fuel in a fuel tank with concentrated suspension of the fire suppressing powder or microscopic encapsulated particles only in the case of emergency (for example, landing or take-off of an aiφlane); when the emergency conditions are over, the fire suppressing powder or microscopic encapsulated particles are returned into the auxiliary vessel.

In the second case, the outer surface of the filters should be constantly cleaned from a layer of disposed particles. There are some possible methods of doing it. For example, irradiation of the filters' surface with ultrasonic radiation, or application of fuel jets generated by subdividing the fuel stream pumped from the fuel tank unto two sub-streams: the first one is directed into the engine and the second one flows backwards into the fuel tank with a set of nozzles, which shape jets directed on the filters' surface.

In the latter case, such jets may serve for mixing and equalization of concentration of the suspension of particles in the fuel tank.

It is possible, for example, to apply two filters installed in the fuel tank, these filters operate alternately; one filter is filtering suspension of fire suppressing powder or microscopic encapsulated particles in fuel and the other is cleaned by reverse flow of the fuel portion from the fuel pump (the other portion is supplied into the engine). A proper system of valves ensures such regime of operation and alternation of the filters' functioning.

Besides, it is possible to apply a hydraulic accumulator, which is positioned on the line communicating the fuel pump with the engine. In combination with a proper system of valves (including a three-way valve), it allows to clean periodically the abovementioned filter by backward flow of the fuel from the hydraulic accumulator, at the same time, this fuel is supplied from the hydraulic accumulator to the engine.

Other possibilities of cleaning the filter include a self-cleaning mechanism by special wipers and, in certain situations, rotation of the filter itself.

These self-cleaning methods are known and acceptable in water-filtering systems.

It should be noted that the fire suppression medium in the fuel tank can be composed as a mixture of particles that suppress fire in different ways. For example, such mixture can contain particles of sodium bicarbonate, which is decomposing at temperatures higher than 60°C with formation of water and carbon dioxide, and microscopic encapsulated particles of silicagel impregnated with Halon (for example, Halon FE25/HFC-125). Furthermore, it is possible that the aforementioned microscopic encapsulated particles can contain aqueous solution of soluble salt with fire suppression properties.

It is a primary objective of this invention to provide a simple, immediate, reliable and cheap passive system of fire suppression for different vehicles or aiφlanes.

Another objective of the invention is to provide a fire suppression system, which is actuated immediately with fire initiation and causes its suppression without any operation system (without a sensor, a gas generator, etc.).

It is an additional objective of this invention to ensure presence in the air of small particles of substances interrupting combustion process when fuel droplets, which are formed in the case of spilling fuel from the disrupted fuel tank, are spread around. All these when hot fragments or parts come in touch with the fuel.

Brief Description of Drawings

FIG. 1 demonstrates a cross-section of a fuel tank with a separator installed outside of it and an impeller with an outer drive.

FIG. 2 shows a cross-section of a fuel tank with a filter installed in it and a set of ultrasound transducers installed in the lower section of this fuel tank.

FIG. 3 shows a cross-section of a fuel tank with a filter installed in it and a set of nozzles fastened at the bottom section of this fuel tank.

Best Mode for Carrying Out the Invention

FIG. 1 shows a cross-section of a fuel tank with a separator installed outside of it and an impeller with an outer drive.

The fuel tank 101 comprises of envelope 102 with an inlet connection 103 for charging the fuel tank 101 with fuel 118, an outlet connection 104 serving for the delivery of fuel from the fuel tank 101 by a fuel pump 105 to separator 106. Fuel, which is separated from particles with fire suppressing properties, is delivered to engine 124 via pipe 114 with valve 115 and a hydraulic pressure damper 123, and concentrated suspension of fire suppressing particles in fuel is directed into an auxiliary accumulation vessel 107. This auxiliary accumulation vessel 107 is connected to an auxiliary inlet connection 108 of the fuel tank 101 by pipe 112 and pump 113. The auxiliary accumulation vessel is provided with impeller 116, drive 117 and a suspension concentration sensor 125.

Sleeve 119 of the fuel tank 101 serves for installation cartridge 120 with desiccant 121.

In addition, the fuel tank 101 is provided with impellers 109 and stuffing boxes 1 10. Rotation of impellers 109 is performed by drives 11 1. A suspension concentration sensor 122 is installed on the internal wall of the fuel tank 101.

FIG. 2 demonstrates a cross-section of a fuel tank with a filter installed in it and a set of ultrasound transducers installed in the lower section of this fuel tank.

The fuel tank 201 comprises of envelope 202 with an inlet connection 203 for charging the fuel tank 201 with fuel. An outlet connection 204 serves for discharging suspension of fuel with fire suppressing particles from the fuel tank 201. Pump 205 supplies the fuel into filter 206 installed in bottom section of the fuel tank 201, and thereafter this fuel, which is separated from the small particles of fire suppressing substances, is supplied in engine 212 through pipe 209, a hydraulic pressure damper 208 and valve 210. A set of ultrasound transducers 207 is installed in the bottom of the fuel tank 201. These transducers help clean the surface of filter 206 and, at the same time, for equalization of suspension concentration in the entire volume of the fuel tank 201 filled with fuel.

In addition, there is impeller 213 with motor 214, this impeller is situated in lower section of the fuel tank 201.

Sensor 211 installed on the internal wall of envelope 202 serves for measuring concentration of the fire suppressing particles in the fuel.

Sleeve 204 at the bottom section of fuel tank 201 serves to discharge the suspension of fire suppressing particles from this fuel tank.

FIG. 3 shows a cross-section of a fuel tank with a filter installed in it and a set of nozzles fastened in the bottom section of this fuel tank.

The fuel tank 301 comprises of envelope 302 with an inlet connection 303 for charging the fuel tank 301 with fuel. Pump 305 supplies the fuel into filter 306 installed in bottom section of the fuel tank 301, and thereafter this fuel, which is separated from the small particles of fire suppressing substances, is supplied in engine 311 through pipe 309, a hydraulic pressure damper 314 and valve 310. Besides, there is a bypass line 315 with valve 316.

There is an auxiliary pump 308, which supplies fuel to a set of nozzles 307 installed in the bottom of fuel tank 301 and nozzle 312 installed in the housing of filter 306. The jet coming out of this nozzle 312 serves for cleaning the surface of filter 306 and, jets from nozzles 307 serves for equalization of suspension concentration in the entire volume of the fuel tank 301 filled by fuel.

Sensor 313 installed on the internal wall of envelope 302 serves for measuring concentration of the fire suppressing particles in the fuel.

Sleeve 304 at the bottom section of the fuel tank 301 serves for discharging the suspension of fire suppressing particles from this fuel tank.

Industrial Applicability

The proposed invention can be widely used in construction and upgrading military/civil vehicles and aiφlanes.

Claims

1. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane, which comprise of:

- powder or microscopic encapsulated particles, which are present in the fuel of the said fuel tank; said powder or said microscopic encapsulated particles have fire suppressing properties;

- a means for equalization of concentration of said powder or said microscopic encapsulated particles in the entire volume of fuel in said fuel tank;

- a means for separating portions of said fuel, when they are supplied to an engine by a pump, from said powder or said microscopic encapsulated particles; while doing so, the obtained concentrated suspension of said powder or said microscopic encapsulated particles in said fuel, is returned into the said fuel tank or accumulated in an auxiliary vessel for following mixing with following portions of fuel charged in said fuel tank.

2. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 1, wherein said system is provided with a means for desiccation of fuel charged in said fuel tank.

3. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane, as claimed in Claim 2, wherein said means for desiccation of fuel is a permeable cartridge filled with desiccant; said cartridge is installed in the internal space of said fuel tank.

4. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 3, wherein said desiccant is silicagel.

5. A system of fire suppression in a fuel tank of a civil or military vehicle or airplane as claimed in Claim 1, wherein said powder is sodium bicarbonate.

6. A system for fire suppression in a fuel tank as claimed of civil or military vehicle or aiφlane as claimed in Claim 1 , wherein said powder is diammonium acidic phosphate.

7. A system for fire suppression in a fuel tank as claimed of civil or military vehicle or airplane as claimed in Claim 1, wherein said microscopic encapsulated particles contain small particles of silicagel impregnated with Halon and said small silicagel particles are covered by a polymer coating, which is stable in fuel and Halon.

8. A system for fire suppression in a fuel tank of civil or military vehicle or aiφlane as claimed in Claim 1, wherein fuel in said fuel tank contains suspension of a mixture of powder and microscopic encapsulated particles, said powder and said microscopic encapsulated particles have different mechanism of fire suppression.

9. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 1, wherein said means for equalization of concentration of said powder or said microscopic encapsulated particles in the entire volume of fuel in said fuel tank is designed as a set of nozzles installed in the lower section of said fuel tank; in this case, fuel supplied into an engine by said pump is subdivided into two streams: the first one flows to said engine, and the second one is supplied to said nozzles and serves for mixing said powder and/or said microscopic encapsulated particles in said fuel.

10. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 1, wherein there is at least one internal impeller, a motor with a reduction gearbox and a stuffing box, which is installed in the wall of said fuel tank; said impeller with said motor, said reduction gearbox and said stuffing box serve for equalization of concentration of said powder and/or said microscopic encapsulated particles in fuel in said fuel tank.

11. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 1, wherein said means for equalization of concentration of said powder or said microscopic encapsulated particles in the entire volume of fuel in said fuel tank is designed as a set of ultrasound transducers installed in the bottom section of said fuel tank.

12. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 1, wherein said means for separation of said fuel, when it is supplied to an engine by a pump, from said powder or said microscopic encapsulated particles, is a separator, which separates said suspension of said powder and/or said microscopic encapsulated particles into fuel and concentrates suspension of said powder and/or said microscopic encapsulated particles in fuel; said concentrated suspension of said powder and/or said microscopic encapsulated particles in fuel is accumulated in an auxiliary vessel for mixing with following portions of fuel when they are charged into said fuel tank, or returned immediately into said fuel tank.

13. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 13, wherein there is an additional filter, which is installed on a line communicating said separator and said engine.

14. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 1, wherein a means for separation of portions of said fuel from said powder or said microscopic encapsulated particles, while said fuel is supplied to an engine by said pump, is a filter installed in said fuel tank.

15. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 13, wherein a set of ultrasound transducers is installed in the bottom section of said fuel tank or on the outer housing of said filter, said set helps to clean the outer surface of said filter from a layer of aggregated particles of said powder and/or said microscopic encapsulated particles; at the same time said set of said ultrasound transducers serves as said means for equalization of concentration of said powder or said microscopic encapsulated particles in the entire volume of fuel in said fuel tank.

16. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 13, wherein a set of nozzles installed in the lower section of said fuel tank and/or in the outer housing of said filter, said nozzles serve for cleaning the outer surface of said filter from a layer of aggregated particles of said powder and/or said microscopic encapsulated particles; at the same time said set of said nozzles serves as said means for equalization of concentration of said powder and/or said microscopic encapsulated particles in the entire volume of fuel in said fuel tank.

17. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 13, wherein there are two filters installed in said fuel tank, said filters operate alternately; one said filter is filtering said suspension of fire suppressing powder or microscopic encapsulated particles in fuel and the other is cleaned by reverse flow of the fuel portion from said fuel pump, while the other portion is supplied into said engine; a proper system of the valves ensures such regime of operation and alternation of said filters' functioning after a certain period.

18. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 13, wherein said filter is cleaned mechanically by wipers.

19. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 13, wherein said filter is cleaned by a mechanism, which causes its rotation.

20. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 13, wherein there is a hydraulic accumulator, which is positioned on the line communicating said fuel pump with said engine; in addition, there is a proper system of valves (including a three-way valve), which allows to clean periodically said filter by backward flow of the fuel from said hydraulic accumulator, at the same time, this fuel is supplied from said hydraulic accumulator to said engine.

21. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 1, wherein said fuel tank is provided with a set of sensors measuring concentration of said powder and/or said microscopic encapsulated particles in fuel at different places of said fuel tank.

22. A system of fire suppression in a fuel tank of a civil or military vehicle or aiφlane as claimed in Claim 14, wherein said concentrated suspension of said powder or microscopic encapsulated particles in said auxiliary vessel is introduced in said fuel tank only in the case of emergency (for example, landing or take-off of an aiφlane); when the emergency conditions are over, the fire suppressing powder or microscopic encapsulated particles are returned into the auxiliary vessel.