FIRE, EXPLOSION AND LIQUIFACTION PROTECTION SYSTEM

Abstract

Creation of a protected space in the interior of a vehicle surrounding elements of the vehicle’s fuel system stops subsequent unsafe leakage of fuel and flammable gas into other interior spaces of the vehicle. It limits both the potential for the build-up of flammable gas in the interior of the vehicle and the potential of detonation. The protected space, if used to protect a cryogenic fuel system, also protects against liquefaction occurring. In the event that the protected fuel system has a failure the design will cause forced ventilation to occur to safely vent the protected space and protect the vehicle from the failure.

Claims

1. A vehicle comprising: a fuel system including a fuel tank and one or more fuel system components outside of the fuel tank, and a protected space for protecting the vehicle from fire, detonation and/or liquefaction wherein the protected space includes: an enclosure defining a closed volume containing the one or more fuel system components; and a fused opening in fluid communication with the closed volume and an external atmosphere, the fused opening having a closed configuration in which the closed volume is sealed and an open configuration in which the closed volume is open to the external atmosphere, the fused opening being reconfigurable from the closed configuration to the open configuration in response to a pressure in the closed volume equalling or exceeding a threshold pressure.

2. The vehicle according to claim 1, comprising one or more inflammable filler elements filling a substantial part of the closed volume.

3. The vehicle according to claim 2, wherein the one or more inflammable filler elements comprise one or more of: one or more spacer elements having a shape configured to substantially conform to a shape of at least a portion of the enclosure; and a plurality of microbeads or microcapsules.

4. The vehicle according to claim 2, wherein the one or more fuel system components contains, or is configured to contain, a cryogenic fuel and the one or more inflammable filler elements are formed from a thermally insulating material.

5. The vehicle according to claim 1, wherein the fused opening comprises a lip configured to project into an air flow over the vehicle when the fused opening is in the open configuration to thereby ventilate the closed volume.

6. The vehicle according to claim 5, wherein the fused opening comprises an interior air deflector configured to cooperate with the lip to increase ventilation of the enclosure in the open configuration.

7. The vehicle according to claim 6, wherein the interior air deflector comprises an air scoop having an inwardly curved profile.

8. The vehicle according to claim 1, wherein the fused opening comprises a fused panel configured to become at least partially detached from the enclosure in the open configuration.

9. The vehicle according to claim 8, wherein the fused opening comprises a lip configured to project into an air flow over the vehicle when the fused opening is in the open configuration to thereby ventilate the closed volume, and the lip is concealed by the fused panel in the closed configuration.

10. The vehicle according to claim 9, wherein the fused opening comprises an exterior panel defining the lip, wherein the exterior panel and the fused panel together define a continuous exterior surface of the vehicle in the closed configuration.

11. The vehicle according to claim 1, including one or more electrical drives for the one or more fuel system components, the one or more electrical drives being mounted outside the closed volume.

12. The vehicle according to claim 1, wherein the one or more fuel system components contains, or is configured to contain, a cryogenic fuel, and the enclosure provides a sealed closed volume in the closed configuration.

13. The vehicle according to claim 1, wherein the vehicle is an aircraft.

14. A vehicle comprising: a fuel system including a fuel tank and one or more fuel system components outside of the fuel tank, and a protected space for protecting the vehicle from fire, detonation and/or liquefaction wherein the protected space includes: an enclosure defining a sealed closed volume housing the one or more fuel system components; and one or more inflammable filler elements filling a substantial part of the sealed closed volume.

15. A vehicle according to claim 14, wherein the one or more inflammable filler elements comprises one or more spacer elements having a shape configured to substantially conform to a shape of at least a portion of the enclosure.

16. A vehicle according to claim 14, wherein the one or more inflammable filler elements comprises a plurality of microbeads or microcapsules.

17. A vehicle according to claim 15, wherein a plurality of microbeads or microcapsules are arranged in a residual volume around the one or more spacer elements .

18. A vehicle according to claim 16, wherein the one or more spacer elements comprise channels to direct filling of the microbeads or microcapsules into the protected space.

19. A vehicle according to claim 17, wherein the plurality of microbeads or microcapsules comprise a mixture of sizes of microbeads or microcapsules.

20. An aircraft comprising: a cryogenic fuel system, which supplies a propulsion system of the aircraft, the cryogenic fuel system including a fuel tank and one or more fuel system components outside of the fuel tank, and a protected space within a vehicle structure for protecting the vehicle from fire, detonation and/or liquefaction wherein the protected space includes: an enclosure defining a closed volume containing the one or more fuel system components; a fused opening in fluid communication with the closed volume and an external atmosphere, the fused opening having a closed configuration in which the closed volume is sealed and an open configuration in which the closed volume is open to the external atmosphere, the fused opening being reconfigurable from the closed configuration to the open configuration in response to a pressure in the closed volume equalling or exceeding a threshold pressure; and one or more inflammable filler elements, formed from a thermally insulating material, filling a substantial part of the closed volume.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0055] FIG. 1 illustrates a representative fuel system installed in a vehicle structure that may be protected by the invention;

[0056] FIG. 2 illustrates an exploded view showing the build-up of a protected space according to an embodiment of the invention;

[0057] FIG. 3 illustrates an assembled view of a protected space according to an embodiment of the invention; and

[0058] FIG. 4 illustrates an embodiment of the invention in which a fused panel and surrounding structure creates a forced ventilation of the interior of the protected space in the case of the fused panel being triggered.

DETAILED DESCRIPTION

[0059] In most vehicle fuel systems, the fuel system consists of a number of different types of components or elements, and the installed fuel system passes through different distinct internal zones of the vehicle formed by the vehicle’s structural elements. These different zones containing elements of the fuel system may each have different types of safety implications, or safety risk factors. These safety implications may be increased susceptibility to physical impacts, say from tyre debris release, proximity to a source of electrical charge that could spark a fire, or the thermal environment of the zone. The description herein of the invention should be read to allow for any single element of the protective system to be embodied in isolation, or in any combination of the elements.

[0060] FIG. 1 shows a representative fuel system installation 100, installed into a vehicle structure 10, which supplies the propulsion system 11 of the vehicle. This representative fuel system includes a fuel storage tank 12, pipes 13, valves 14, pumps 15 and other types of equipment (not shown) that have a direct connection to the fuel system. For example the invention could be used to provide protection for a fuel cell installation (not shown) on a vehicle rather than valves 14 and pumps 15.

[0061] Many of these system elements are typically not of simple geometry, making their protection difficult, and the invention very practical as a protection means. They may also often have rotating elements and seals rather than hard connections, meaning permeation of fuel and leakage is more likely. In preferred embodiments the protected space re-uses or is enclosed by structural elements of the vehicle that already exist for other purposes as is indicated in FIG. 1, however it is also possible that the designer finds it beneficial to make a completely separate or partially separate enclosure to create the protected space.

[0062] FIG. 2 shows a build-up view (or exploded view) of a protected space 200 and the associated protections for fire, explosion and liquefaction that can be included. The enclosure of the protected space 200 in the illustrated embodiments is formed from part of the interior structure 201 of the vehicle and from an enclosing element 204, a closing element 209, sealed maintenance panel 211 and external surface 214. The enclosure thus defines a closed volume within the protected space 200.

[0063] The vehicle structure 201 in some embodiments will have distinct structural mounting features 202 to connect the enclosing element 204 to the vehicle structure 201 and seal it. The structural mounting features 202 may include outwardly-projecting flanges as illustrated, to provide one or more lapped joints with the enclosing element 204. The vehicle structure 201 may also have penetrations 203 to allow sealed connections to pipes 13 that are connected with an adjacent interior zone. These penetrations 203 will have an appropriate seal or sealant element around the penetrating pipe 13 to substantially seal the protected space 200.

[0064] In preferred embodiments the enclosing element 204 for the protected space 200 will be made of one or more pieces and will be connected to the vehicle structure 201 with a suitable sealing element 205 sandwiched between the mating surfaces of the structural mounting features 202 and the enclosing element 204 to ensure that any joints are substantially sealed. Inside the enclosing element 204 the installed fuel system elements 206 (fuel system components) that are being protected will be installed. Inside the enclosing element 204, and clear of the vehicle structure 201, one or more non-flammable spacer elements 207 will be installed around the installed fuel system elements 206 to reduce the volume available for a flammable or explosive mixture to fill in the case of leakage inside the protected space 200. The non-flammable spacer elements 207 in preferable embodiments may be made from inflammable material like silicon. The non-flammable spacer elements 207 may be installed by mechanical attachment, adhesive fastening, or other appropriate means. After the installation of the non-flammable spacer elements 207, installation of the fuel system elements 206 will be completed, and installation checks performed. Afterwards, in some embodiments of the invention one or more additional non-flammable spacer elements 208 may be added to further reduce the volume available for a flammable or explosive mixture in the case of leakage. Then in preferred embodiments the closing element 209 will be used to close the protected space 200, with a further suitable sealing element 210 between mating surfaces of the enclosing element 204 and closing element 209 to ensure any joints are substantially sealed. Embodiments where the closing element 209 and the enclosing element 204 are integrated together into a single part are possible, as is the possibility that these elements are formed by existing structural elements of the vehicle in place on the vehicle for another purpose, such as structural load carrying for an example.

[0065] It is also possible for a different sequence of installation to the above where the installation of the fuel system elements 206 occurs before the enclosing element 204 is assembled to the vehicle structure 201.

[0066] To ensure that the fuel system elements 206 can be accessed for maintenance operations a sealed maintenance panel 211 and an appropriate sealing element 212 will be incorporated into the design of the protected space 200 in preferred embodiments. In the illustrated embodiments the sealing element 212 provides a sealed joint between the maintenance panel 211 and the closing element 209.

[0067] Any electric actuation motors 213 of any contained equipment such as valves 206a or pumps 206b will be mounted on the external surfaces of the enclosure of the protected space 200 defined by the any combination of the vehicle structure 201, enclosing element 204, closing element 209 and maintenance panel 211. These actuation motors 213 will act through sealed drive elements and will be electrically isolated from the interior to make the protected space 200 separate and isolated from any ignition sources.

[0068] In preferred embodiments, to allow over-pressure due to a leakage to be addressed and vented from the vehicle, at least one external surface 214 of the protected space 200 will be connected to the exterior of the vehicle. This external surface 214 will have a suitable seal 215 to ensure that the whole of the protected space 200 will be substantially sealed in normal operations and without leakage. By substantially sealing the protected space 200 it will not be possible for a continuous entry flow of air to enter the interior of the protected space 200 and hence the possibility for the cryogenic fuel system elements 206 having liquification occurring on their surfaces is substantially restricted. To allow the release of over-pressure from the interior of the protected space 200 due to any leakage failure of the enclosed fuel system elements 206, the external surface 214 will have a cut out for one or more fused openings in the form of fused pressure panels 216 that are usually substantially sealed to the external surface 214, but designed to fail and separate when the pressure inside the protected zone 200 exceeds a pre-defined failure pressure. This separation of the fused panel 216 will thereby ensure the protected space 200 does not experience excessive over-pressure with the risk of structural failure and that any leaking fuel and vapours will ultimately be discharged from the vehicle safely. Further, the designed failure (i.e. deployment or activation) of the fused pressure panel(s) 216 will be easily detectable in a pre-flight inspection before any subsequent operation of the vehicle allowing corrective maintenance to repair any leaks or other failures to take place and to restore all levels of protection of the fuel system 100.

[0069] In some embodiments to further restrict the available space in the closed volume of the protected space 200 that a flammable or explosive mixture could build-up in, inert microbeads or microcapsules (such as glass microbeads) can be introduced into the unfilled interior of the protected space 200 to occupy a high proportion of the internal volume. These microbeads or microcapsules in preferred embodiments will introduced via a dedicated inlet 217, to allow the optimum filling of the protected space 200, and the dedicated inlet 217 can be completely closed by an appropriate lid or cap completing the sealing of the protected zone 200. By using a mixture of sizes of microbeads or microcapsules, any residual unfilled space in the protected space 200 can filled up by another 74%-84% based on mathematical analysis of the packing ratio of such spheres. The microbeads or microcapsules can be used in addition to the non-flammable spacer elements 207, or in some embodiments the microbeads or microcapsules may be used exclusively without the inclusion of the non-flammable spacer elements 207 in the protected space 200. When the microbeads or microcapsules are used in conjunction with the non-flammable spacer elements 207 the latter should have appropriate channels cut within the non-flammable spacer elements 207 to direct the filling of the microbeads or microcapsules and ensure the optimum and complete filling of the protected space 200.

[0070] For new vehicle propulsion systems using cryogenic fuels, there is not only the risk of the leaking fuel creating a fire and explosion risk, but if any surfaces exposed to air fall below -183° C. the condensation of oxygen from the air can create an explosive mix even in the absence of a fuel leak. Therefore, in addition to the restriction in available space for flammable or explosive mixtures to build up, the microbeads or microcapsules and the non-flammable spacer elements 207 will also perform the function of creating an insulation layer around the fuel system elements 206 which will prevent and protect against the occurrence of liquefaction.

[0071] The dedicated inlet 217 to allow the effective introduction of the microbeads or microcapsules can be both used for the vehicle assembly or after maintenance to reintroduce the microbeads or microcapsules that have been removed to facilitate maintenance activity. In preferred embodiments the filling of the protected space 200 by microbeads or microcapsules during assembly or after maintenance will happen after all the assembly of the enclosing element 204, closing element 209, sealed maintenance panel 211, external surface 214 and fused pressure panel(s) 216 have been installed in place, along with all associated sealing.

[0072] FIG. 3 illustrates a preferred embodiment of the protected space 200 in its assembled state, with the interior elements obscured. In preferred embodiments the enclosing element 204, closing element 209, sealed maintenance panel 211 and external surface 214 should be structurally sized so, that in the worst case that the detonation of any leaked and explosive mixture in the unfilled volume of the protected zone 200 does occur, that these elements will sustain and contain the detonation force and only the fused pressure panel(s) 216 will fail, protecting the rest of the vehicle from damage. The detonation energy to be considered in such structural sizing can be significantly reduced by taking benefit of the installation of the non-flammable spacer elements 207, 208 and microbeads or microcapsules if these elements are included to fill the protected space 200.

[0073] An additional element of protection from the invention for the protected space 200 is the forced ventilation element illustrated in FIG. 4, which will only become active in the case that the fused pressure panel(s) 216 fails. In normal operation, where there is no failure of the fuel system elements 206 and consequently no failure of the fused panel(s) 216, the air flow 218 will travel around the aerodynamically smooth outer panel surfaces and have minimal disturbance to ensure the vehicle has minimal drag. However, if there is a failure of the fuel system elements 206 causing an over-pressure and consequentially the designed failure (i.e. deployment or activation) of the fused pressure panel(s) 216 then the geometrical design of the fused pressure panel(s) 216 and the surrounding fixed external surface 214 will be such that the detachment of the fused pressure panel(s) 216 will cause some part of the surrounding fixed external surface 214 to have an exposed lip 219 projecting into the air flow 220 created by the vehicle travelling through the air. This exposed lip 219 projecting into the air flow 220 will cause a forced ventilation into the protected space 200 due to the direction of the air flow 220. This exposed lip 219 may in preferred embodiments be created from a faired bump 221 that projects from the vehicle and remains faired with minimal drag in the normal operational condition where the fused pressure panel(s) 216 is fully attached. The internal air flow 220 and forced ventilation of the protected space may be enhanced by an internal scoop element 222 internally connected to the exposed lip 219. The forced ventilation caused by the direction of the air flow 220 is designed to be at a flow rate that at the normal operating speed of the vehicle that it would cause the combined air flow and typical fuel leakages mixture from the internal fuel system elements 206 to be below the flammability limits of the fuel used.

[0074] In some embodiments of the protective system, it may be accepted to have the protected space 200 without any non-flammable spacer elements 207, 208 and without any microbeads or microcapsules and instead rely solely on forced ventilation 220 after a failure of the fused panel(s) 216 using the system illustrated in FIG. 4. Where all the elements of the invention are present in a single system, the failure of the fused pressure panel(s) 216 would be designed to allow some or all of the microbeads or microcapsules to be released from the protected space 200 and from the vehicle, opening up the interior of the protected space 200 for the forced air flow 220 to ventilate the interior volume. If non-flammable spacer elements 207, 208 are included in the embodiment of the protection system and forced air flow 220 to ventilate the interior is desired, then air channels will be made in the non-flammable spacer elements 207, 208 to permit sufficient directed flow of air within the protected space 200 to reduce the mixture ratio within the protected space 200 to be below flammability limits.