System for securing an aircraft fluid circuit at risk, associated mounting method and method of use

Abstract

A system (2) for securing a portion (1P) of a fluid circuit (1) in which a fluid at risk for an aircraft (A) circulates, the securing 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 inner casing pressure (Pc) strictly lower than atmospheric pressure; at least one inner casing (4) configured to be mounted around the portion (1P) of the fluid circuit (1) in the outer casing (3) and defining a sealed inner enclosure, the inner casing (4) having an inner casing pressure (Pe); and a drainage pump (5) fluidically connected to the inner casing (4) and configured to suck up any leak (F) of fluid in the inner casing (4) and evacuate it outside the outer casing (3). Abstract figure: Figure 3

Description

Title of the invention: System for securing an aircraft fluid circuit at risk, associated mounting method and method of use 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 applies in particular to securing an aircraft fuel circuit.

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various States. In particular, an ambitious standard applies both to new types of aircraft and those in circulation requiring the implementation of technological solutions in order to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0003] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the impact factors in all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products 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 and minimizing greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work covers new generations of aircraft engines, the lightening of aircraft, particularly through the materials used and lighter on-board equipment, the development of the use of electrical technologies to ensure propulsion, and, as essential complements to technological progress, aeronautical biofuels.

[0006] To this end, the invention is the result of technological research aimed at very significantly improving the performance of aircraft 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 limit the size and mass of the tanks of an aircraft. For this purpose, the fuel is stored in a cryogenic tank of the aircraft and is conveyed to the turbomachine by a fluid circuit. For example, the fuel flow is stored in the cryogenic tank at a temperature of the order of -253 to -251°C (20 to 22 Kelvins).

[0008] In order to be able to circulate in the structure of the aircraft to the combustion chamber of the turbomachine M, the fuel Q must be conditioned, that is to say pressurized and heated, to pass into the gaseous state. For this, with reference to [Fig.l], a flow of fuel Q circulates in the fluid circuit CQ and successively passes through a mechanical pump PO and a heat exchanger EC. The mechanical pump PO is configured to circulate the flow of fuel Q in the fluid circuit CQ. The heat exchanger EC is configured to provide calories to the flow of fuel Q in order to heat it so that it can be injected into the turbomachine M.

[0009] In practice, the fuel flow Q is heated in the heat exchanger EC from calories from heat sources of the aircraft. For example, as shown in [Fig. 1], it is known to heat the fuel flow Q from calories transferred by the exhaust air flow coming from the turbine stage TU of the turbomachine M, the exhaust air flow coming from the combustion, in the combustion chamber CC, between the fuel flow Q and a compressed air flow. The transfer of calories is carried out, in a known manner, by means of a heat transfer fluid FC, for example an inert gas such as nitrogen, which makes it possible to avoid the risk of contact, in the heat exchanger EC, between an oxidizing fluid and a reducing fluid.

[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 seals made of flexible material to tightly connect the various pieces of equipment in the fluid circuit CQ, such as for example the mechanical pump PO, the heat exchanger EC or even a closing valve V which controls the circulation and the flow rate of the fuel flow Q in the fluid circuit CQ. Consequently, it is not possible to ensure the absence of fuel leaks Q in the fluid circuit CQ, which can present a significant drawback.

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

[0012] For this, it is known to use a safety system by box 100, also shown in [Fig.l], which extends around all the cryogenic equipment of the fluid circuit CQ and allows them to be isolated from the air. A vacuum pump 101 makes it possible to create a vacuum inside the box 100 and to drain to the outside of the box 100 any leaks of fuel Q that may appear at the junctions of the equipment. The drainage makes it possible to prevent the fuel Q from accumulating in the box 100. The vacuum provided by the pump 101 also makes it possible to avoid transfers of calories (cold or hot) by convection or conduction, by eliminating the transmission vector which is the air.

[0013] In practice, it is necessary for the vacuum pump 101 to operate continuously to ensure the vacuum and drain the fuel leaks Q to the outside of the box 100. It is then necessary to use a high-performance vacuum pump, which has many drawbacks. Indeed, such a vacuum pump has a large footprint, which is impractical, particularly in an aeronautical environment. In addition, the vacuum pump is heavy, which increases the aircraft's fuel consumption and therefore its greenhouse gas emissions. Furthermore, such a pump is energy-intensive and represents a source of heat, which is not desirable in the presence of a fuel Q such as hydrogen or methane. Furthermore, the fuel leaks Q in the sealed box 100 can impact the maintenance of the vacuum, which can affect the thermal insulation of the fluid circuit CQ.

[0014] The invention thus aims to eliminate at least some of these drawbacks by proposing a reliable and efficient system for securing a high-risk fluid circuit of an aircraft, which makes it possible to ensure both thermal insulation of the fluid circuit and optimal drainage of fluid leaks. The invention aims in particular at a high-performance vacuum pump-free security system. PRESENTATION OF THE INVENTION

[0015] The invention relates to a system for securing a portion of a fluid circuit in which a fluid at risk for an aircraft circulates, the securing system comprising: • an outer casing configured to be mounted around the portion of the fluid circuit, the outer casing defining around the portion of the fluid circuit a sealed outer enclosure, the outer 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 around the portion of fluid circuit a sealed inner enclosure, so as to define a double sealed enclosure, the inner envelope having an inner envelope pressure, and a drainage pump fluidly connected to the inner casing, the drainage pump being configured to suck up any fluid leakage in the inner casing and discharge it outside the outer casing.

[0016] The safety system makes it possible to form a sealed double wall in which the outer casing provides thermal insulation and the inner casing, associated with the drainage pump, ensures the drainage of any leaks of fluid at risk. Such a safety system thus makes it possible to separate the thermal insulation function from the drainage function, which advantageously makes it possible to avoid the continuous use of a high-performance vacuum pump to ensure the vacuum in the safety system. It is therefore not necessary to mount such a pump in the aircraft, which limits the mass of the latter and facilitates the integration of the safety system in the aircraft. Avoiding the need to mount a high-performance vacuum pump in the aircraft thus makes it possible to limit the aircraft's fuel consumption and greenhouse gas emissions.

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

[0018] Thanks to the safety system according to the invention, in the event of a leak appearing in the inner casing, the latter is drained by the drainage pump and the vacuum level inside the outer casing is not modified. In other words, it is not necessary to recreate the vacuum inside the outer casing and the thermal insulation is ensured continuously.

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

[0020] Preferably, the internal pressure of the box is strictly lower than the internal pressure of the casing, so as to prevent the internal casing from being pressed against the portion of the fluid circuit. Leaks of fluid at risk can thus appear in the internal casing and be evacuated to the outside by the drainage pump in a simple manner, without risking any retention of fluid at risk in the internal casing.

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

[0022] Preferably, the internal envelope pressure is lower than atmospheric pressure, so as to limit the mixing between the fuel and air in a confined space. Preferably, the internal envelope pressure has a pressure of the order of 100 Pa, which makes it possible to ensure a sufficiently low air concentration to avoid a risk of ignition in the event of a fuel leak.

[0023] Such an internal envelope pressure makes it possible to ensure that the internal envelope is not pressed against the equipment of the fluid circuit, which makes it possible to avoid any risk of damage or wear of the internal envelope in contact with the equipment while ensuring that any fluid leak that may appear can be evacuated.

[0024] According to one aspect, the internal pressure of the box is of the order of 10 Pa, making it possible to ensure effective thermal insulation of the safety system. Thanks to such an internal pressure of the box, the fluid at risk can circulate in the fluid circuit at cryogenic temperatures without risking damage to 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 whose modulus of elasticity E is 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 makes it possible to form a substantially flexible inner casing, which makes it possible to limit its bulk. Such a material makes it possible to secure the portion of the fluid circuit in a constrained environment, in particular, near an aircraft turbomachine. This also limits the mass of the securing system, which is particularly advantageous in an aeronautical environment which aims to limit greenhouse gas emissions from aircraft. A semi-rigid inner casing is also simpler for operators to put in place and limits their arduousness.

[0026] In a second embodiment, the inner envelope 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 envelope is between 5 x 103 and 100 x 103 MPa. The material is thus rigid and makes it possible to form a rigid double barrier which is more resistant to the temperatures of the environment in which the portion of the fluid circuit is mounted.

[0027] In one embodiment, the security system comprises at least one insulating wall mounted in the outer casing, the insulating wall being configured to thermally insulate a first interior volume of the outer casing and a second interior volume of the outer casing. Such an insulating wall makes it possible to mount equipment of the fluid circuit whose temperature is different, without the temperature of one of them impacting the equipment neighboring the portion of the fluid circuit. In other words, the insulating wall makes it possible to limit thermal radiation to protect certain equipment of the portion of the fluid circuit.

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

[0029] Preferably, the safety system is free from a vacuum pump when used in the aircraft, which makes it possible to limit the mass and size of the safety system and thus makes it possible to limit the consumption of the aircraft.

[0030] In one embodiment, the drainage pump is an active pump, preferably a hydraulic pump or an 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 pieces of equipment in the fluid circuit.

[0031] Alternatively, the drainage pump is a passive pump and comprises a device operating according to the Venturi effect, which makes it possible to dispense with the need to mount specific equipment and thus makes it possible to limit the mass and size of the safety system, which represents a significant advantage, particularly 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 risky 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 of mounting a securing system as described above, for securing a portion of the fluid circuit, the mounting method comprising the steps of: • create a first level of vacuum in the inner envelope using a vacuum pump, • fluidly connect the drainage pump to the inner casing, • creating a second vacuum level in the outer casing using the vacuum pump, the second vacuum level being lower than the first vacuum level of the inner casing, and • remove the vacuum pump.

[0035] Thanks to such an assembly method, a high-performance vacuum pump is used only when installing the safety system. It is then removed and is advantageously not carried in the aircraft, which makes it possible to significantly limit the mass of the safety system and the aircraft. The in-flight energy consumption of the safety system is also advantageously limited since it is not necessary to operate a high-performance vacuum pump continuously.

[0036] The invention finally relates to a method of using a security system as described above, the method of use comprising a step consisting of sucking up, by means of the drainage pump, a leak of risky 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 necessary when using the safety system, since the vacuum level inside the box is not modified in the event of a leak of risky fluid. Thermal insulation is ensured. PRESENTATION OF FIGURES

[0038] The invention will be better understood on reading the description which follows, 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.l] is a schematic representation of a system for securing a high-risk fluid circuit 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 safety system according to a first embodiment of the invention.

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

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

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

[0045] [Fig.7] is a schematic representation of the steps of a method of mounting the security system of [Fig.3].

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

[0047] With reference to [Fig. 2], there is shown an aircraft A comprising a plurality of turbomachines M powered by fuel Q from a tank R of fuel Q. In this example, the fuel Q is dihydrogen but it goes without saying that the invention applies to any type of risky fuel, in particular, methane. In general, the invention applies to any circuit for transporting a risky fluid.

[0048] The fuel Q is stored in the tank R at cryogenic temperatures. For example, the fuel flow Q is stored in the cryogenic tank R at a temperature of the order of -253 to -251°C (20 to 22 Kelvins). At this temperature, the fuel flow Q is liquid. In order to be able 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 comprises 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 calories 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 goes without saying that the fuel flow Q could pass through more than one heat exchanger EC to heat, for example, the fuel flow Q gradually.In this example, a control valve VI makes it possible, upstream of the heat exchanger EC, to control the flow rate of the fuel flow Q in the fuel circuit 1 and a closing valve V2 makes it possible, downstream of the heat exchanger EC, to control the circulation of the fuel flow 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 equipment.

[0050] In this example, the fuel circuit 1 comprises a portion IP 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 closing valve V2 are mounted on the portion IP of the fluid circuit 1. It goes without saying that the portion IP could comprise a variety of equipment.

[0051] The IP portion of 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 envelope 4 mounted around the portion IP 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, in order to protect the IP portion of the fuel circuit 1 effectively. Preferably, the outer casing 3 is made of metal or a composite material. Such an outer casing 3 makes it possible to thermally insulate the IP portion of the fuel circuit 1 to prevent the formation of frost on the equipment of the turbomachine M due to the cryogenic temperatures of the fuel Q.

[0056] Preferably, with reference to [Fig. 4], the outer casing 3 comprises a first sealing member 30A mounted at a first upstream end 13A of the portion IP of the fuel circuit 1, corresponding to the inlet of the portion IP into the outer casing 3, and a second sealing member 30B mounted at a first downstream end 13B of the portion IP of the fuel circuit 1, corresponding to the outlet of the portion IP of the outer casing 3. The outer casing 3 also comprises a third sealing member 30C mounted at an inlet in the outer casing 3 of a heat transfer fluid circuit FC, 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 member 30D mounted at an outlet of the heat transfer fluid circuit FC, of ​​the outer casing 3. It goes without saying that the outer casing 3 may comprise a different number of members sealing 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 outer casing 3, the latter comprises as many sealing members 30.

[0057] In this example, each sealing member 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 with respect to fluids and fire.

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

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

[0060] For this, in one embodiment, the outer casing 3 has a connection orifice 31 shown in [Fig.4] and configured to punctually connect a vacuum pump, so as to place the interior volume of the outer casing 3 at the interior casing pressure Pc, as will be described in more detail later. The connection orifice 31 is resealable in a sealed manner.

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

[0062] The dimensions of the inner casing 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 security system 2. In particular, in this embodiment, the inner casing 4 is made of a material whose modulus of elasticity is 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.In order to increase its mechanical resistance, the inner envelope 4 may include reinforcement (a composite mesh, a belt 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, making it possible to ensure effective thermal insulation of the IP portion of the fuel circuit 1 with respect to cryogenic temperatures of the fuel Q which circulates in the fuel circuit 1. In addition, the inner casing 4 is thus non-deformable, making it possible to limit any risk of damage to the safety system 3, for example by avoiding any risk of cracking of the inner casing 4 in contact with a corner or a sharp edge of one of the pieces of equipment of the fuel circuit 1. In particular, in this embodiment, the inner casing 4 is made of a material whose modulus of elasticity E is between 5x103 and 200x103 MPa. Preferably, the modulus of elasticity is between 5x103 and 100x103 MPa. In this example, the inner casing 4 is made of a metallic, composite material or any material insensitive to the fuel Q and capable of withstanding depression.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 member 40A mounted at a second upstream end 14A of the portion IP of the fuel circuit 1, corresponding to the inlet of the portion IP into the inner casing 4, and a second sealing member 40B mounted at a second downstream end 14B of the portion IP of the fuel circuit 1, corresponding to the outlet of the portion IP of the inner casing 4. The inner casing 4 also comprises a third sealing member 40C mounted at an inlet in the inner casing 4 of the heat transfer fluid circuit FC and a fourth sealing member 40D mounted at an outlet of the heat transfer fluid circuit FC of the inner casing 4. It goes without saying that the inner casing 4 may comprise a different number of sealing members 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 comprises as many sealing members 40.

[0066] In this example, each sealing member 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 of the heat transfer fluid circuit FC can extend. It goes without saying that each sealing member 40 could be in a different form, for example, in the form of a clamp, in particular, forming an integral part of a flange between two components of the fuel circuit 1.

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

[0068] According to one aspect of the invention, the inner casing 4 has an inner casing pressure Pe strictly greater than the inner box 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 inner box pressure Pc being lower than atmospheric pressure. Preferably, the inner 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 the air in the event of a leak from the portion IP of the fuel circuit 1. More preferably, the inner casing pressure Pe is between 10 Pa and 100 Pa. In this example, the inner casing pressure Pe is of the order of 100 Pa.

[0069] For this purpose, in one embodiment, the inner casing 4 has a connection port 41 configured to temporarily connect a vacuum pump, so as to place the inner volume of the inner casing 4 at the inner casing pressure Pe, as will be described in more detail later. The connection port 41 is resealable in a sealed manner.

[0070] In one embodiment, as shown in [Fig. 6], the securing system 2 comprises several inner casings 4A, 4B, all of the inner casings 4A, 4B being configured to be mounted around the portion IP of the fluid circuit 1. Preferably, each inner casing 4A, 4B is configured to be mounted around an independent part IIP, 12P of the portion IP of the fluid circuit 1. In other words, the inner casings 4A, 4B are all mounted in the outer casing 3 around different equipment of the portion IP to be secured. In this example, the securing system 2 comprises two inner casings 4A, 4B, it goes without saying that the number of inner casings 4A, 4B could be greater than two.Several inner casings 4A, 4B advantageously make it possible to limit the size of the latter, which makes it easier to mount the safety system 2 around the IP portion of the fluid circuit 1. Such an embodiment also makes it possible to carry out maintenance of the equipment independently of each other. In this embodiment, it goes without saying that the safety system 2 comprises a sealing member 40 at each inlet and at each outlet of the fuel circuit 1 of each inner casing 4A, 4B.

[0071] Thanks to the outer casing 3 and the inner envelope 4 associated with the different pressure levels, the securing system 2 is free from a high-performance vacuum pump during its use in the aircraft, which advantageously allows It is therefore advisable to limit the mass and size of the security system 2 and therefore of the aircraft. This also makes it possible to limit the production costs and the energy consumption of the aircraft.

[0072] With reference to Figures 3 to 6, in order to drain the fuel leaks F that could appear in the inner casing 4, the safety system 2 comprises a drainage pump 5 fluidically connected to the inner casing 4 and configured to evacuate the fuel leaks F Q to the outside of the outer casing 3. More precisely, the drainage pump 5 is configured to generate a flow rate making it possible to circulate the mixture of air and fluid at risk in the event of a leak F. In other words, the drainage pump 5 has dimensions and characteristics configured to allow the drainage of the leaks, without generating sufficient power to cause a pressure difference. The drainage pump 5 is thus light and compact.

[0073] Preferably, the drainage pump 5 is configured to generate a power of between 1 and 5 kW. Such power allows the drainage pump 5 to drain a fuel leak Q, without causing a pressure difference between the inner enclosure and the outside. Such a drainage pump 5 is thus light and compact.

[0074] To drain any possible fuel leaks Q, in this example, the safety system 2 comprises 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 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 comprises at the junction with the inner casing 4, a passage portion whose section is limited, allowing, due to the pressure difference between the inner casing 4 and the exterior of the outer casing 3 and the narrowing of the passage section, to suck up the fuel leaks Q and to convey them to the exterior of the outer casing 3.

[0077] According to one aspect, the drainage pump 5 is connected to a computer of the aircraft, 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 security system 2 comprises an insulating wall 6 mounted in the outer box 3 and configured to divide the interior volume of the outer box 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 goes without saying that the security 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 of a single inner casing 4, as shown in [Fig.5].

[0079] The insulating 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) pieces of equipment of the fuel circuit 1 from the other pieces of equipment of the fuel circuit 1 present in the external box 3. For this, the insulating wall 6 is preferably made of a rigid material, so as to form effective thermal protection. In this example, the insulating wall 6 comprises a stack of layers of reflective materials (known to those skilled in the art under the designation Multi Layer Insulation), making it possible to limit losses by thermal radiation. The insulating wall 6 can alternatively be made of a material making it possible to reduce thermal losses.

[0080] In one embodiment, the security system 2 comprises a first pressure sensor (not shown) configured to measure the internal pressure of the box Pc in the external box 3, so as to ensure optimal operation of the security system 2. The security system 2 also comprises a second pressure sensor (not shown) configured to measure the internal pressure of the envelope Pe in the internal envelope 4.

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

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

[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 fluidically connects the drainage pump 5 to the inner casing 4, in a step E2.

[0085] As illustrated in [Fig.4], each sealing member 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 member 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 casing 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 sucking out the air present in the latter. The vacuum is created until the pressure inside the inner casing 4 reaches a predetermined inner casing pressure Pe. In this example, the inner casing pressure Pe is substantially equal to 100 Pa. In other words, in this step, a first level of vacuum is created in the inner casing 4. When the inner pressure of the inner casing 4 is at the inner casing pressure Pe, the vacuum pump PV is disconnected and the connection port 41 is closed tightly.

[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, so as to create a vacuum in the outer casing 3 by sucking out the air present in the latter. The vacuum is created until the pressure inside the outer casing 3 reaches a predetermined inner casing pressure Pc, the inner casing pressure Pc being lower than the inner casing pressure Pe. In this example, the inner casing pressure Pc is substantially equal to 10 Pa. In other words, in this step, a second vacuum level, lower than the first vacuum level, is created 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 is at the inner casing pressure Pc, the vacuum pump is disconnected and the connection port 31 is closed tightly.The inner casing 4 is not subjected to forces which tend to press it against the equipment of the IP portion. The inner casing 4 is thus deployed to receive a possible leak while having a smaller volume than the outer casing 3, which facilitates the management of the inner casing pressure Pe. The inner casing pressure Pc is advantageously not modified and the outer casing 3 ensures thermal insulation.

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

[0091] In this example, a leak F is detected, in a step EA, at one of the equipments of 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 drainage pump 5 is then activated to suck up the fuel leak F Q and evacuate it outside the outer casing 3, in a step EB. Thanks to the drainage pump 5 connected to the inner casing 4, the inner pressure of the casing Pc is not modified by the drainage of the leak F and the thermal insulation is ensured in a lasting manner by the outer casing 3, which makes it possible to secure the portion IP of the fuel circuit 1 effectively.

Claims

Claims

1. System for securing (2) a portion (IP) of a fluid circuit (1) in which a fluid at risk for an aircraft (A) circulates, the securing 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 around the portion (IP) of the fluid circuit (1) a sealed outer enclosure, the outer casing (3) having an inner casing pressure (Pc) strictly lower than atmospheric pressure, • at least one inner casing (4) configured to be mounted around the portion (IP) of the fluid circuit (1) in the outer casing (3), the inner casing (4) defining around the portion (IP) of the fluid circuit (1) a sealed inner enclosure, so as to define a double sealed enclosure, the inner casing (4) having an inner casing pressure (Pe),and • a drainage pump (5) fluidically connected to the inner casing (4), the drainage pump (5) being configured to suck up any possible leak (F) of fluid in the inner casing (4) and evacuate it outside the outer casing (3).,

2. Securing system (2) according to claim 1, in which the internal pressure of the box (Pc) is strictly lower than the internal pressure of the envelope (Pe), so as to prevent the internal envelope (4) from being pressed against the portion (IP) of the fluid circuit (1).

3. Securing system (2) according to one of claims 1 to 2, in which the inner casing (4) is made of a material whose modulus of elasticity E is between 0.5 x 03 and 5 x 03 MPa.

4. Securing system (2) according to one of claims 1 to 2, in which the inner casing (4) is made of a material whose modulus of elasticity E is between 5xl03 and 200xl03 Pa.

5. Securing system (2) according to one of claims 1 to 4, the securing system (2) comprising at least one insulating wall (6) mounted in the outer casing (3), the insulating wall (6) being configured to thermally insulate a first interior volume (3A) of the exterior box (3) and a second interior volume (3B) of the exterior box (3).

6. Securing system (2) according to one of claims 1 to 5, the securing system (2) comprising several inner casings (4A, 4B), all of said inner casings (4A, 4B) being configured to be mounted around the portion (IP) of fluid circuit (1), each inner casing (4A, 4B) being configured to be mounted respectively around an independent part (IIP, 12P) of the portion (IP) of fluid circuit (1).

7. Securing system (2) according to one of claims 1 to 6, the securing system (2) being free from a vacuum pump during its use in the aircraft.

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

9. Securing system (2) according to one of claims 1 to 8, in which the drainage pump (5) is a passive pump and comprises a device operating according to the Venturi effect.

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

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

12. 1U. Method for mounting a securing system (2) according to one of claims 1 to 10, for securing a portion (IP) of the fluid circuit (1), the mounting 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 drainage 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 security system (2) according to one of claims 1 to 9, the method of use comprising a step consisting of sucking up, by means of the drainage pump (5), a leak (F) of fluid at risk present in the inner casing (4) and evacuating it to the outside of the outer casing (3).

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