Aircraft fluid circuit safety system, assembly method and associated operating method

Abstract

A containment system (2) for a portion (1P) of a fluid circuit (1) carrying a fluid that is hazardous to an aircraft (A), the containment system (2) comprising: an outer casing (3) configured to be mounted around the portion (1P) of the fluid circuit (1) and defining a sealed outer enclosure, the outer casing (3) having an internal casing pressure (Pc) strictly lower than atmospheric pressure; at least one inner jacket (4) configured to be mounted around the portion (1P) of the fluid circuit (1) within the outer casing (3) and defining a sealed inner enclosure, the inner jacket (4) having an internal jacket pressure (Pe); and a drain pump (5) fluidically connected to the inner jacket (4) and configured to draw any leakage (F) of fluid from the inner jacket (4) and discharge it outside the outer casing (3). Abstract figure: Figure 3

Description

Title of the invention: System for securing a fluid circuit at risk in an aircraft, method of assembly and method of use associated technical field

[0001] The present invention relates to the field of securing installations in which a hazardous fluid circulates, for example a flammable or explosive fluid. The invention is particularly applicable to securing an aircraft fuel system.

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation have moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the weight reduction of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0006] To this end, the invention is the result of technological research aimed at significantly improving aircraft performance and, in this sense, contributes to reducing the environmental impact of aircraft. For this purpose, the invention applies in particular to a cryogenic fuel circuit for supplying an aircraft turbomachine.

[0007] It is known to store fuel, for example hydrogen or methane, in liquid form to reduce the size and mass of an aircraft's fuel tanks. For this purpose, the fuel is stored in a cryogenic tank on the aircraft and conveyed to the turbomachine via a fluid circuit. As an example, the fuel stream is stored in the cryogenic tank at a temperature of approximately -253 to -251°C (20 to 22 Kelvin).

[0008] In order to circulate within the aircraft structure to the combustion chamber of the turbomachine M, the fuel Q must be conditioned, i.e., pressurized and heated, to become gaseous. For this purpose, as shown in [Fig. 1], a flow of fuel Q circulates in the fluid circuit CQ and passes successively through a mechanical pump PO and a heat exchanger EC. The mechanical pump PO is configured to circulate the flow of fuel Q through the fluid circuit CQ. The heat exchanger EC is configured to supply heat to the flow of fuel Q to warm it so that it can be injected into the turbomachine M.

[0009] In practice, the fuel stream Q is heated in the heat exchanger EC using heat from hot sources in the aircraft. For example, as shown in [Fig. 1], it is known to heat the fuel stream Q using heat transferred by the exhaust air stream from the turbine stage TU of the turbomachine M, the exhaust air stream being a product of combustion in the combustion chamber CC between the fuel stream Q and a compressed air stream. The heat transfer is achieved, in a known manner, via a heat transfer fluid FC, for example an inert gas such as nitrogen, which avoids the risk of contact between an oxidizing fluid and a reducing fluid in the heat exchanger EC.

[0010] However, between the cryogenic tank R and the heat exchanger EC, the fuel flow Q circulates at very low temperatures, close to cryogenic temperatures. Such temperatures do not allow the use of flexible material seals to create a leak-proof connection between the various components of the fluid circuit CQ, such as the mechanical pump PO, the heat exchanger EC, or even a shut-off valve V that controls the circulation and flow rate of the fuel Q in the fluid circuit CQ. Consequently, it is not possible to ensure the absence of fuel Q leaks in the fluid circuit CQ, which can be a significant drawback.

[0011] Furthermore, at cryogenic temperatures, it is necessary to thermally insulate the CQ fluid circuit from the ambient air to limit the risk of ice formation or frost on pipes and equipment.

[0012] For this purpose, it is known to use a containment system consisting of a chamber 100, also shown in [Fig. 1], which extends around all the cryogenic equipment in the fluid circuit CQ and isolates it from the air. A vacuum pump 101 creates a vacuum inside the chamber 100 and drains any fuel Q leaks that may occur at the equipment junctions to the outside of the chamber 100. This drainage prevents fuel Q from accumulating in the chamber 100. The vacuum provided by the pump 101 also eliminates heat transfer (cold or hot) by convection or conduction, by removing the air as the transmission medium.

[0013] In practice, the vacuum pump 101 must operate continuously to maintain the vacuum and drain any fuel leaks Q from the outside of the chamber 100. This necessitates the use of a high-performance vacuum pump, which presents several drawbacks. Such a vacuum pump is quite bulky, which is impractical, especially in an aeronautical environment. Furthermore, the vacuum pump is heavy, increasing the aircraft's fuel consumption and therefore its greenhouse gas emissions. In addition, such a pump is energy-intensive and generates heat, which is undesirable in the presence of a fuel Q such as hydrogen or methane. Moreover, fuel leaks Q into the sealed chamber 100 can affect the maintenance of the vacuum, which can compromise the thermal insulation of the fluid circuit CQ.

[0014] The invention thus aims to eliminate at least some of these drawbacks by providing a reliable and efficient system for securing a potentially hazardous fluid circuit in an aircraft, which ensures both thermal insulation of the fluid circuit and optimal drainage of fluid leaks. The invention specifically aims at a high-performance, vacuum-pump-free securing system. PRESENTATION OF THE INVENTION

[0015] The invention relates to a system for securing a portion of a fluid circuit in which a fluid that poses a risk to an aircraft circulates, the security system comprising: • an external casing configured to be mounted around the portion of the fluid circuit, the external casing defining a sealed external enclosure around the portion of the fluid circuit, the external casing having an internal casing pressure strictly lower than atmospheric pressure, • at least one inner casing configured to be mounted around the portion of the fluid circuit in the outer casing, the inner casing defining a sealed inner enclosure around the portion of the fluid circuit, so as to define a double sealed enclosure, the inner shell having an internal shell pressure, and a drainage pump fluidically connected to the inner casing, the drainage pump being configured to suck up any fluid leakage in the inner casing and evacuate it outside the outer casing.

[0016] The containment system forms a double-walled, sealed structure in which the outer casing provides thermal insulation, while the inner casing, combined with the drainage pump, drains any leaks of hazardous fluid. This containment system thus separates the thermal insulation function from the drainage function, advantageously eliminating the need for a high-performance vacuum pump to maintain a vacuum within the containment system. Consequently, it is not necessary to install such a pump in the aircraft, reducing its mass and facilitating the integration of the containment system. Eliminating the need for a high-performance vacuum pump in the aircraft also reduces fuel consumption and greenhouse gas emissions.

[0017] The internal pressure of the caisson, which is lower than atmospheric pressure, makes it possible to create a relative vacuum in the external caisson, which makes it possible to thermally insulate the portion of the fluid circuit from the outside of the caisson effectively.

[0018] Thanks to the safety system according to the invention, in the event of a leak in the inner casing, the leak is drained by the drainage pump and the vacuum level inside the outer casing remains unchanged. In other words, it is not necessary to re-establish the vacuum inside the outer casing and thermal insulation is continuously maintained.

[0019] Preferably, the drainage pump is configured to generate a power output of between 1 and 5 kW. This power allows the pump to drain leaks of hazardous fluid without creating a pressure difference within the internal enclosure. In other words, the drainage pump is advantageously lightweight and compact, unlike the prior art vacuum pump, since it is not configured to create a pressure difference but to generate a flow rate that allows the air and hazardous fluid mixture to circulate in the event of a leak.

[0020] Preferably, the internal pressure of the casing is strictly lower than the internal pressure of the outer casing, so as to prevent the inner casing from being pressed against the portion of the fluid circuit. Leaks of hazardous fluid can thus occur in the inner casing and be easily discharged to the outside by the drain pump, without risking any retention of hazardous fluid within the inner casing.

[0021] Thanks to the inner casing, which has a lower vacuum level than the outer casing, it is not necessary to add individual internal leak recovery systems to each piece of equipment in the fluid circuit section. This represents a significant weight saving while limiting the size of the section within the safety system. Fluid circuit integration is also simplified.

[0022] Preferably, the internal pressure of the casing is lower than atmospheric pressure, so as to limit the mixing of fuel and air in a confined space. Preferably, the internal pressure of the casing is on the order of 100 Pa, which ensures a sufficiently low air concentration to eliminate the risk of ignition in the event of a fuel leak.

[0023] Such internal envelope pressure ensures that the inner envelope is not pressed against the fluid circuit equipment, thus eliminating any risk of damage or wear to the inner envelope in contact with the equipment while ensuring that any fluid leakage that may occur can be evacuated.

[0024] According to one aspect, the internal pressure of the chamber is on the order of 10 Pa, ensuring effective thermal insulation of the safety system. Thanks to this internal chamber pressure, the hazardous fluid can circulate in the fluid circuit at cryogenic temperatures without risk of damaging the external environment of the fluid circuit, and in particular the turbomachine.

[0025] In a first embodiment, the inner casing is made of a material with a modulus of elasticity E between 0.5 x 10³ and 5 x 10³ MPa. Preferably, the modulus of elasticity E of the inner casing is between 1 x 10³ MPa and 1.6 x 10³ MPa. The material is thus semi-rigid and allows for the formation of a substantially flexible inner casing, thereby reducing its size. Such a material makes it possible to secure the portion of the fluid circuit in a constrained environment, particularly near an aircraft turbomachine. This also reduces the mass of the safety system, which is particularly advantageous in an aeronautical environment that aims to limit greenhouse gas emissions from aircraft. A semi-rigid inner casing is also easier for operators to install and reduces the physical strain on them.

[0026] In a second embodiment, the inner casing is made of a material whose modulus of elasticity E is between 5 x 10³ and 200 x 10³ MPa. Preferably, the modulus of elasticity E of the inner casing is between 5 x 10³ and 100 x 10³ MPa. The material is thus rigid and makes it possible to form a double rigid barrier that is more resistant to the temperatures of the environment in which the A portion of the fluid circuit is installed.

[0027] In one embodiment, the protection system includes at least one insulation wall mounted in the outer casing, the insulation wall being configured to thermally insulate a first internal volume of the outer casing and a second internal volume of the outer casing. Such an insulation wall allows the installation of fluid circuit equipment with different temperatures, without the temperature of one of them affecting neighboring equipment in the portion of the fluid circuit. In other words, the insulation wall limits thermal radiation to protect certain equipment in the portion of the fluid circuit.

[0028] According to one aspect, the protection system comprises several inner enclosures, all of said inner enclosures being configured to be mounted around the portion of the fluid circuit, each inner enclosure being configured to be mounted respectively around an independent part of the portion of the fluid circuit. Several inner enclosures can advantageously be mounted independently of each other, which facilitates their installation in the protection system. This is particularly advantageous when the portion of the fluid circuit to be encapsulated has large dimensions.

[0029] Preferably, the safety system is free of a vacuum pump when used in the aircraft, which limits the mass and size of the safety system and thus limits the aircraft's fuel consumption.

[0030] In one embodiment, the drainage pump is an active pump, preferably a hydraulic or electric pump, which allows efficient drainage of fuel leaks while limiting any risk of accumulation of hazardous fluid in the inner casing in the event of a leak from one of the fluid circuit components.

[0031] Alternatively, the drainage pump is a passive pump and includes a device operating according to the Venturi effect, which makes it possible to avoid the need for the installation of specific equipment and thus to limit the mass and size of the safety system, which represents an important advantage in particular in an aeronautical environment.

[0032] In one embodiment, the hazardous fluid circulating in the fluid circuit is a cryogenic fuel.

[0033] The invention also relates to an aircraft comprising at least one fluid circuit in which a hazardous fluid circulates and at least one system for securing a portion of the fluid circuit as described above.

[0034] Furthermore, the invention relates to a method for mounting a safety system as described above, to secure a portion of the fluid circuit, the mounting method comprising the steps of: • create an initial vacuum in the inner casing using a vacuum pump, • fluidly connect the drainage pump to the inner casing, • create a second vacuum level in the outer casing using the vacuum pump, this second vacuum level being lower than the first vacuum level in the inner casing, and • Remove the vacuum pump.

[0035] Thanks to this mounting method, a high-performance vacuum pump is used only during the installation of the safety system. It is then removed and advantageously not carried on board the aircraft, thus significantly reducing the mass of both the safety system and the aircraft. The in-flight energy consumption of the safety system is also advantageously reduced since it is not necessary to run a high-performance vacuum pump continuously.

[0036] The invention finally relates to a method of using a safety system as described above, the method of use comprising a step consisting of sucking up, by means of the drainage pump, a leak of hazardous fluid present in the inner casing and evacuating it to the outside of the outer casing.

[0037] Thanks to the safety system according to the invention, a high-performance vacuum pump is not required when using the safety system, since the vacuum level inside the chamber is not altered in the event of a leak of hazardous fluid. Thermal insulation is ensured. PRESENTATION OF THE FIGURES

[0038] The invention will be better understood upon reading the following description, given by way of example, and referring to the following figures, given by way of non-limiting examples, in which identical references are given to similar objects.

[0039] Fig. 1 is a schematic representation of a system for securing a fluid circuit at risk according to the prior art.

[0040] Fig. 2 is a schematic representation of an aircraft comprising a fuel circuit supplying a turbomachine.

[0041] Fig. 3 is a schematic representation of a fuel circuit security system according to a first embodiment of the invention.

[0042] Fig. 4 is a close-up view of the security system of Fig. 3.

[0043] Figure 5 is a schematic representation of a circuit safety system of fuel according to a second embodiment of the invention.

[0044] Figure 6 is a schematic representation of a circuit safety system of fuel according to a third embodiment of the invention.

[0045] Fig. 7 is a schematic representation of the steps of a process for assembling the securing system of Fig. 3.

[0046] It should be noted that the figures set out the invention in detail to implement the invention, said figures being of course able to serve to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0047] With reference to [Fig. 2], an aircraft A is shown comprising a plurality of turbomachines M powered by fuel Q from a fuel tank R containing fuel Q. In this example, the fuel Q is dihydrogen, but it is understood that the invention applies to any type of hazardous fuel, in particular, methane. More generally, the invention applies to any system for transporting a hazardous fluid.

[0048] The fuel Q is stored in the tank R at cryogenic temperatures. For example, the fuel stream Q is stored in the cryogenic tank R at a temperature of approximately -253 to -251°C (20 to 22 Kelvin). At this temperature, the fuel stream Q is liquid. In order to be introduced into a combustion chamber CC of the turbomachine M, the fuel Q must be heated.

[0049] For this purpose, with reference to [Fig. 3], the aircraft A includes a fuel circuit 1 which connects the cryogenic tank R to the combustion chamber CC of the turbomachine M. The fuel flow Q circulates from upstream to downstream in the fuel circuit 1 by means of a mechanical pump PO and passes through a heat exchanger EC, in which it exchanges heat with a heat transfer fluid FC. In this example, the heat exchanger EC is configured to heat the fuel flow Q to a vaporization temperature. It is understood that the fuel flow Q could pass through more than one heat exchanger EC to, for example, gradually reheat the fuel flow Q.In this example, a regulating valve VI, upstream of the heat exchanger EC, controls the flow rate of the fuel stream Q in the fuel circuit 1, and a shut-off valve V2, downstream of the heat exchanger EC, controls the flow of the fuel stream Q towards the combustion chamber CC of the turbomachine M. It goes without saying that the fuel circuit 1 could include a different number of pieces of equipment.

[0050] In this example, the fuel circuit 1 includes a portion IP which is capable of generating fuel leaks Q which must be contained to ensure the safety of the aircraft A. In this example, the mechanical pump PO, the control valve VI, the heat exchanger EC and the shut-off valve V2 are mounted on the portion IP of the fluid circuit 1. It is understood that the portion IP could include a variety of equipment.

[0051] The IP portion of the fuel circuit 1 is secured by a security system 2 which will now be presented in detail.

[0052] With reference to figures 3 and 4, the securing system 2 comprises an outer casing 3 and an inner enclosure 4 mounted around the IP portion of the fuel circuit 1 to be secured.

[0053] As shown in [Fig.3], the outer casing 3 is mounted around the IP portion of the fuel circuit 1 and defines around the IP portion of the fluid circuit 1 a sealed outer enclosure.

[0054] The dimensions of the outer casing 3 are determined to correspond to the IP portion of the fuel circuit 1 to be secured.

[0055] The outer casing 3 is preferably made of a rigid material to effectively protect the IP portion of the fuel circuit 1. Preferably, the outer casing 3 is made of metal or a composite material. Such an outer casing 3 thermally insulates the IP portion of the fuel circuit 1 to prevent frost formation on the turbomachine M equipment due to the cryogenic temperatures of the fuel Q.

[0056] Preferably, with reference to [Fig. 4], the outer casing 3 comprises a first sealing element 30A mounted at a first upstream end 13A of the IP portion of the fuel circuit 1, corresponding to the inlet of the IP portion into the outer casing 3, and a second sealing element 30B mounted at a first downstream end 13B of the IP portion of the fuel circuit 1, corresponding to the outlet of the IP portion of the outer casing 3. The outer casing 3 also comprises a third sealing element 30C mounted at an inlet of a heat transfer fluid circuit FC into the outer casing 3, the heat transfer fluid FC being configured to heat the fuel flow Q in the heat exchanger EC, as described previously, and a fourth sealing element 30D mounted at an outlet of the heat transfer fluid circuit FC from the outer casing 3. It is understood that the outer casing 3 may comprise a different number of sealing elements. 30.In particular, if the fuel circuit 1 and / or the heat transfer fluid circuit FC has more than one inlet and one outlet in the external casing 3, the latter includes as many sealing elements 30.

[0057] In this example, each sealing element 30 is in the form of a flexible component, for example an elastic ring, configured to ensure both the mechanical connection and the sealing of the outer casing 3 against fluids and fire.

[0058] Preferably, the outer casing 3 has an opening (not shown), for example a hatch, to allow access to the IP portion of the fuel circuit 1, for example for maintenance. The opening is resealable in a hermetic manner. The opening is preferably sized to allow the removal of equipment of the IP portion or the complete removal of the IP portion from the fuel circuit 1.

[0059] According to one aspect of the invention, in use, the outer casing 3 has an internal casing pressure Pc strictly lower than atmospheric pressure, i.e., 105 Pa. In other words, the internal volume delimited by the outer casing 3 is under vacuum to limit the risk of mixing between the fuel Q and air in the event of a leak from portion IP of the fuel circuit 1. Preferably, the internal casing pressure Pc is between 1 and 10 Pa. In this example, the internal casing pressure Pc is on the order of 10 Pa.

[0060] To this end, in one embodiment, the outer casing 3 has a connection port 31 shown in [Fig. 4] and configured to connect a vacuum pump intermittently, so as to bring the internal volume of the outer casing 3 to the internal pressure of the casing Pc, as will be described in more detail later. The connection port 31 can be sealed airtight.

[0061] As described previously and shown in Figures 3 and 4, the inner enclosure 4 is mounted around the IP portion of the fuel circuit 1. More specifically, the inner enclosure 4 is mounted around the IP portion inside the outer casing 3 and defines a sealed inner enclosure around the IP portion of the fluid circuit 1. Thus, the outer casing 3 and the inner enclosure 4 define double protection for the IP portion of the fuel circuit 1.

[0062] The dimensions of the inner enclosure 4 are determined to correspond to the IP portion of the fuel circuit 1 to be secured.

[0063] In a first embodiment, the inner casing 4 is made of a flexible material. The inner casing 4 is thus deformable, so as to limit the size of the locking system 2. In particular, in this embodiment, the inner casing 4 is made of a material with a modulus of elasticity between 500 and 5000 MPa. Preferably, the modulus of elasticity is between 1000 and 1600 MPa. Such a modulus of elasticity makes it possible to form a semi-rigid inner casing 4, capable of deforming while being sufficiently robust to limit any risk of damage to the inner casing 4. In this example, the inner casing 4 is made of a polymer-type material (single-layer, multi-layer, composite, or other), for example, TFE (or Teflon®), natural or synthetic rubber, silicone, etc.To increase its mechanical resistance, the inner casing 4 may include reinforcement (a composite mesh, a band or other), for example, with polyester, nylon, aramid or steel.

[0064] In a second embodiment shown in [Fig. 5], the inner casing 4 is made of a substantially rigid material, ensuring effective thermal insulation of the IP portion of the fuel circuit 1 vis-à-vis cryogenic temperatures of the fuel Q circulating in the fuel circuit 1. Furthermore, the inner casing 4 is thus non-deformable, limiting any risk of damage to the safety system 3, by preventing, for example, any risk of cracking of the inner casing 4 upon contact with a corner or sharp edge of any of the components of the fuel circuit 1. In particular, in this embodiment, the inner casing 4 is made of a material with a modulus of elasticity E between 5x03 and 200x03 MPa. Preferably, the modulus of elasticity is between 5x03 and 100x03 MPa. In this example, the inner casing 4 is made of a metallic, composite, or any other material insensitive to the fuel Q and capable of withstanding negative pressure.In particular, in this embodiment, the inner casing 4 is, for example, made of the same material as the outer casing 3 to form a robust double wall and reinforce the thermal insulation of the IP portion of the fluid circuit 1.

[0065] Preferably, with reference to [Fig. 4], the inner casing 4 comprises a first sealing element 40A mounted at a second upstream end 14A of the IP portion of the fuel circuit 1, corresponding to the inlet of the IP portion into the inner casing 4, and a second sealing element 40B mounted at a second downstream end 14B of the IP portion of the fuel circuit 1, corresponding to the outlet of the IP portion of the inner casing 4. The inner casing 4 also comprises a third sealing element 40C mounted at an inlet in the inner casing 4 of the heat transfer fluid circuit FC and a fourth sealing element 40D mounted at an outlet of the heat transfer fluid circuit FC of the inner casing 4. It is understood that the inner casing 4 may comprise a different number of sealing elements 40.In particular, if the fuel circuit 1 and / or the heat transfer fluid circuit FC has more than one inlet and one outlet in the inner casing 4, the latter includes as many sealing elements 40.

[0066] In this example, each sealing element 40 is in the form of an elastic ring inside which an end IA, IB of the portion IP of the fuel circuit 1 or the heat transfer fluid circuit FC can extend. It is understood that each sealing element 40 could be in a different form, for example, in the form of a hose clamp, in particular, forming an integral part of a flange between two components of the fuel circuit 1.

[0067] Preferably, the inner casing 4 has an opening (not shown) to allow access to the IP portion of the fuel circuit 1, for example, for maintenance. The opening is resealable. In this example, the opening is in the form of a zipper. It goes without saying that the opening could be in a different form, for example, in the form of a repositionable adhesive strip. The opening is preferably sized to allow the removal of equipment from portion 1P or the complete removal of portion IP from fuel circuit 1. Alternatively, it is understood that the inner enclosure 4 may be free of openings and may be configured to be removed for maintenance and replaced with a new inner enclosure 4.

[0068] According to one aspect of the invention, the inner casing 4 has an internal casing pressure Pe strictly greater than the internal chamber pressure Pc, so as to prevent the inner casing 4 from being pressed against the portion IP of the fluid circuit 1 due to the internal chamber pressure Pc being lower than atmospheric pressure. Preferably, the internal casing pressure Pe is also lower than atmospheric pressure, i.e., 105 Pa, so as to limit the risk of mixing between the fuel Q and air in the event of a leak from the portion IP of the fuel circuit 1. Even more preferably, the internal casing pressure Pe is between 10 Pa and 100 Pa. In this example, the internal casing pressure Pe is on the order of 100 Pa.

[0069] To this end, in one embodiment, the inner casing 4 has a connection port 41 configured to temporarily connect a vacuum pump, so as to bring the internal volume of the inner casing 4 to the internal pressure of the casing Pe, as will be described in more detail later. The connection port 41 is resealable in a leak-proof manner.

[0070] In one embodiment, as shown in [Fig. 6], the protection system 2 comprises several inner enclosures 4A, 4B, the set of inner enclosures 4A, 4B being configured to be mounted around the IP portion of the fluid circuit 1. Preferably, each inner enclosure 4A, 4B is configured to be mounted around an independent IIP portion 12P of the IP portion of the fluid circuit 1. In other words, the inner enclosures 4A, 4B are all mounted in the outer casing 3 around different equipment of the IP portion to be protected. In this example, the protection system 2 comprises two inner enclosures 4A, 4B; it is understood that the number of inner enclosures 4A, 4B could be greater than two.Several inner enclosures 4A, 4B advantageously limit their overall size, thus facilitating the installation of the safety system 2 around the IP portion of the fluid circuit 1. This embodiment also allows for independent maintenance of the equipment. In this embodiment, it is understood that the safety system 2 includes a sealing element 40 at each inlet and outlet of the fuel circuit 1 of each inner enclosure 4A, 4B.

[0071] Thanks to the outer casing 3 and the inner shell 4 associated with the different pressure levels, the securing system 2 is exempt from the need for a high-performance vacuum pump when used in the aircraft, which allows for This helps to limit the mass and size of the security system 2 and therefore of the aircraft. It also helps to limit production costs and the aircraft's energy consumption.

[0072] With reference to Figures 3 to 6, in order to drain fuel leaks F that might occur in the inner casing 4, the containment system 2 includes a drainage pump 5 fluidically connected to the inner casing 4 and configured to evacuate fuel leaks F Q to the outside of the outer casing 3. More specifically, the drainage pump 5 is configured to generate a flow rate sufficient to circulate the air and fluid mixture at risk in the event of a leak F. In other words, the drainage pump 5 has dimensions and characteristics configured to allow drainage of the leaks without generating sufficient power to create a pressure differential. The drainage pump 5 is therefore lightweight and compact.

[0073] Preferably, the drain pump 5 is configured to generate a power output of between 1 and 5 kW. This power output allows the drain pump 5 to drain a fuel leak Q without causing a pressure difference between the inner and outer chambers. Such a drain pump 5 is therefore lightweight and compact.

[0074] To drain any potential fuel leaks Q, in this example, the safety system 2 includes a drainage circuit 50 which connects the inner casing 4 to the outside of the safety system 2. In the case of a plurality of inner casings 4A, 4B, the drainage pump 5 is fluidically connected to each of them.

[0075] In a first embodiment, the drainage pump 5 is an active pump and is presented for example in the form of a hydraulic pump or an electric pump.

[0076] In a second embodiment, the drainage pump 5 is a passive pump and operates according to the venturi effect. In one example, the drainage circuit 50 includes, at the junction with the inner casing 4, a passage portion with a limited cross-section, which, due to the pressure difference between the inner casing 4 and the outside of the outer casing 3 and the narrowing of the passage cross-section, allows the fuel leaks Q to be drawn in and conveyed to the outside of the outer casing 3.

[0077] According to one aspect, the drainage pump 5 is connected to an aircraft computer, so as to be activated only when necessary, for example in the event of detection of a leak F.

[0078] In one embodiment, with reference to Figures 5 and 6, the securing system 2 comprises an insulation wall 6 mounted in the outer casing 3 and configured to divide the internal volume of the outer casing 3 into a first elementary volume 3A and a second elementary volume 3B. Each elementary volume 3A, 3B comprises a section 1 IP, 12P of the portion IP of fluid circuit 1. A single insulation wall 6 is described; however, it is understood that the securing system 2 could alternatively comprise more than one insulation wall 6 to thermally insulate more than two elementary volumes 3A, 3B in the outer casing 3. Alternatively, the insulation wall 6 is mounted in the inner casing 4, so as to thermally insulate two elementary volumes 4C, 4D from a single inner casing 4, as shown in [Fig. 5].

[0079] The insulation wall 6 is configured to thermally insulate the first elementary volume 3A and the second elementary volume 3B, so as to thermally insulate one (or more) piece(s) of fuel circuit 1 from the other fuel circuit 1 equipment present in the outer casing 3. For this purpose, the insulation wall 6 is preferably made of a rigid material, so as to form effective thermal protection. In this example, the insulation wall 6 comprises a stack of reflective material layers (known to those skilled in the art as Multi Layer Insulation), making it possible to limit heat loss by radiation. The insulation wall 6 may alternatively be made of a material that reduces heat loss.

[0080] In one embodiment, the safety system 2 includes a first pressure sensor (not shown) configured to measure the internal pressure of the outer casing Pc in the outer casing 3, so as to ensure optimal operation of the safety system 2. The safety system 2 also includes a second pressure sensor (not shown) configured to measure the internal pressure of the outer casing Pe in the inner casing 4.

[0081] According to one aspect, the security system 2 could include a fuel sensor, in particular a hydrogen sensor, to detect any leak F in the inner casing 4.

[0082] A method for mounting the security system 2 as described previously, with reference to [Fig.7], will now be described.

[0083] In a first step E1, the IP portion of the fuel circuit 1 is positioned in the inner casing 4. In practice, the IP portion is inserted through the access opening. The IP portion of the fuel circuit 1 and the inner casing 4 are then positioned in the outer casing 3. In practice, the IP portion and the inner casing 4 are inserted through the access opening.

[0084] The operator then fluidly connects the drainage pump 5 to the inner casing 4, in a step E2.

[0085] As illustrated in [Fig. 4], each sealing element 40A, 40B, 40C, 40D is then mounted respectively at each upstream end 14A and downstream end 14B of the IP portion of the fuel circuit 1 and at the inlet and outlet of the heat transfer fluid circuit FC in the inner casing 4. Similarly, each sealing element 30A, 30B, 30C, 30D is mounted respectively at each end 13A, 13B of the IP portion of the fuel circuit 1 and at the inlet and outlet of the heat transfer fluid circuit FC in the outer casing 3.

[0086] The opening of the inner envelope 4 is then closed so as to form a sealed inner enclosure around the IP portion of the fluid circuit 1.

[0087] In a third step E3, an operator connects a vacuum pump PV (different from the drainage pump 5) to the connection port 41 of the inner casing 4, so as to create a vacuum in the inner casing 4 by drawing out the air present in it. The vacuum is created until the pressure inside the inner casing 4 reaches a predetermined internal casing pressure Pe. In this example, the internal casing pressure Pe is approximately equal to 100 Pa. In other words, in this step, a first level of vacuum is achieved in the inner casing 4. When the internal pressure of the inner casing 4 reaches the internal casing pressure Pe, the vacuum pump PV is disconnected and the connection port 41 is sealed.

[0088] The opening of the outer casing 3 is then closed so as to form a sealed outer enclosure around the IP portion of the fluid circuit 1.

[0089] In a fourth step E4, an operator connects the vacuum pump PV to the connection port 31 of the outer casing 3, thereby creating a vacuum in the outer casing 3 by drawing out the air present within it. The vacuum is maintained until the pressure inside the outer casing 3 reaches a predetermined internal casing pressure Pc, this internal casing pressure being lower than the internal envelope pressure Pe. In this example, the internal casing pressure Pc is approximately equal to 10 Pa. In other words, in this step, a second vacuum level, lower than the first vacuum level, is achieved in the outer casing 3. In this example, the second vacuum level corresponds to 10% of the first vacuum level. When the pressure inside the outer casing 3 reaches the internal casing pressure Pc, the vacuum pump is disconnected and the connection port 31 is sealed.The inner enclosure 4 is not subjected to forces that would press it against the equipment in the IP portion. The inner enclosure 4 is thus deployed to accommodate any potential leak while having a smaller volume than the outer casing 3, which facilitates the management of the internal pressure of the Pe enclosure. The internal pressure of the Pc casing is advantageously not modified, and the outer casing 3 provides thermal insulation.

[0090] A method for using the security system 2, as previously described with reference to [Fig. 3], will now be described. The inner casing 4 and the The outer casing 3 is closed and sealed. An internal casing pressure Pe and an internal casing pressure Pc, lower than the internal casing pressure Pe, are applied respectively inside the inner casing 4 and inside the outer casing 3.

[0091] In this example, a leak F is detected, in a step EA, at one of the equipment in the portion IP of the fuel circuit 1. The leak F appears in the inner casing 4. In this example, the leak F is detected by a fuel sensor mounted in the inner casing 4.

[0092] The drain pump 5 is then activated to draw out the fuel leak F Q and discharge it outside the outer casing 3, in a step EB. Thanks to the drain pump 5 being connected to the inner casing 4, the internal pressure of the casing Pc is not altered by the drainage of the leak F and the thermal insulation is permanently ensured by the outer casing 3, which makes it possible to effectively secure the IP portion of the fuel circuit 1.

Claims

Demands

1. A containment system (2) for a portion (IP) of a fluid circuit (1) in which a fluid that is hazardous to an aircraft (A) flows, the containment system (2) comprising: • an outer casing (3) configured to be mounted around the portion (IP) of the fluid circuit (1), the outer casing (3) defining a sealed outer enclosure around the portion (IP) of the fluid circuit (1), the outer casing (3) having an internal casing pressure (Pc) strictly lower than atmospheric pressure, • at least one inner enclosure (4) configured to be mounted around the portion (IP) of the fluid circuit (1) in the outer casing (3), the inner enclosure (4) defining a sealed inner enclosure around the portion (IP) of the fluid circuit (1), so as to define a double sealed enclosure, the inner enclosure (4) having an internal enclosure pressure (Pe),and • a drainage pump (5) fluidically connected to the inner casing (4), the drainage pump (5) being configured to draw in any leakage (F) of fluid in the inner casing (4) and discharge it outside the outer casing (3).

2. A safety system (2) according to claim 1, wherein the internal pressure of the caisson (Pc) is strictly less than the internal pressure of the envelope (Pe), so as to prevent the inner envelope (4) from being pressed against the portion (IP) of the fluid circuit (1).

3. A security system (2) according to any one of claims 1 to 2, wherein the inner casing (4) is made of a material having a modulus of elasticity E between 0.5x03 and 5x03 MPa.

4. A security system (2) according to any one of claims 1 to 2, wherein the inner envelope (4) is made of a material whose modulus of elasticity E is between 5xl03 and 200xl03 Pa.

5. A security system (2) according to any one of claims 1 to 4, the security system (2) comprising at least one insulation wall (6) mounted in the outer casing (3), the insulation wall (6) being configured to thermally insulate a first internal volume (3A) from an external box (3) and a second internal volume (3B) from an external box (3).

6. A security system (2) according to any one of claims 1 to 5, the security system (2) comprising several inner enclosures (4A, 4B), the set of said inner enclosures (4A, 4B) being configured to be mounted around the portion (IP) of fluid circuit (1), each inner enclosure (4A, 4B) being configured to be mounted respectively around an independent part (IIP, 12P) of the portion (IP) of fluid circuit (1).

7. A securing system (2) according to any one of claims 1 to 6, the securing system (2) being free of a vacuum pump when used in the aircraft.

8. A security system (2) according to any one of claims 1 to 7, wherein the drainage pump (5) is an active pump, preferably a hydraulic pump or an electric pump.

9. A safety system (2) according to any one of claims 1 to 8, wherein the drainage pump (5) is a passive pump and includes a device operating according to the Venturi effect.

10. Safety system (2) according to any one of claims 1 to 9, wherein the hazardous fluid circulating in the fluid circuit (1) is a cryogenic fuel.

11. Aircraft comprising at least one fluid circuit (1) through which a hazardous fluid circulates and at least one system for securing a portion (IP) of the fluid circuit (1) according to any one of claims 1 to 1H

12. 1U. A method for assembling a safety system (2) according to any one of claims 1 to 10, for securing a portion (IP) of the fluid circuit (1), the assembly method comprising the steps of: • creating a first vacuum level in the inner casing (4) by means of a vacuum pump (PV), • fluidly connecting the drain pump (5) to the inner casing (4), • creating a second vacuum level in the outer casing (3) by means of the vacuum pump (PV), the second vacuum level being lower than the first vacuum level of the inner casing (4), and • remove the vacuum pump (PV).

13. Method of using a safety system (2) according to any one of claims 1 to 9, the method of use comprising a step of aspirating, by means of the drainage pump (5), a leak (F) of hazardous fluid present in the inner casing (4) and evacuating it to the outside of the outer casing (3).

Images