System for securing a high-risk fluid circuit and associated processes

Abstract

A system (2) for securing a portion (1P) of a fluid circuit (1) in which a fluid at risk for aircraft circulates, the securing system (2) comprising a conditioning box (3) configured to be mounted around the portion (1P), a conditioning volume (30) being defined between the portion (1P) and the conditioning box (3), a buffer element (4) at least partially filling the conditioning volume (30), the buffer element (4) being an inert component comprising at least one of a fluid element having a dynamic viscosity of between 10-3 and 103 Pa.s or a solid element having a porosity rate of less than or equal to 80%, so as to limit the propagation speed in the conditioning volume (30). Abstract figure: Figure 3

Description

Title of the invention: System for securing a high-risk fluid circuit and associated methods 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, 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 and is conveyed to the turbomachine by a fuel circuit. The fuel circuit comprises a plurality of pipes and equipment, for example a mechanical pump for circulating the fuel flow in the pipes of the fuel circuit, and a heat exchanger, for heating the fuel flow for injection into the combustion chamber of the turbomachine.

[0008] In practice, near the combustion chamber, the pressure inside the fuel circuit pipes can reach several tens of bars (10xl05 Pa). In addition, the pipes are mounted in an environment in which vibration levels and temperatures are high. All of these conditions can damage the pipes or equipment, which can lead to fuel leaks. Such fuels are flammable gases and can be detonating on contact with air.

[0009] In order to secure the use of fuel for an aeronautical application, it is necessary to control the generation of hydrogen leaks into the air, as well as its possible effects.

[0010] In this respect, systems comprising a conditioning box are known in the prior art, which make it possible to isolate the equipment of the fuel circuit in an inert or vacuum environment. However, such systems are impractical in the event of maintenance operations and it is complex to maintain a satisfactory vacuum level. In addition, the pipes and equipment of the fuel circuit mounted near the turbomachine may be exposed to debris (from the rotating parts of the turbomachine for example) which may damage the pipes. In the event of failure, the debris may form, on the one hand, a breach in the pipe, causing a fuel leak, and, on the other hand, a breach in the wall of the box, causing an air leak. The air and the fuel may then come into contact inside the box, therefore in a confined environment, which is not desirable.

[0011] Systems are also known which provide continuous ventilation when the fuel circuit is under pressure, which makes it possible to limit the accumulation of fuel in a substantially confined environment in the event of a leak. Indeed, for example, hydrogen is a gas which can become explosive if its volume concentration in the air is between 4% and 75%. Continuous ventilation makes it possible to avoid the risk of fuel ending up in such concentrations. However, the airflow required to generate such ventilation is taken from the airflow entering the turbomachine and causes losses in the efficiency of the turbomachine.

[0012] The invention thus aims to eliminate at least some of these drawbacks by proposing a reliable and effective system for securing a high-risk fluid circuit of an aircraft, which, in the event of a leak, makes it possible to limit the risk of contact between the high-risk fluid and the air in the turbomachine. PRESENTATION OF THE INVENTION

[0013] 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: • a conditioning box configured to be mounted around the portion of the fluid circuit, a conditioning volume being defined between the portion and the conditioning box, • at least one buffer element at least partially filling the packaging volume.

[0014] The security system is remarkable in that the buffer element is an inert component comprising at least one of a fluid element having a dynamic viscosity of between 103 and 103 Pa.s or a solid element having a porosity rate of less than or equal to 80% so as to limit the speed of propagation in the packaging volume.

[0015] The buffer element is thus in the form of a material capable of forming in the conditioning box an environment in which the speed of movement of a fluid is lowered. This makes it possible to slow down both the propagation of the air surrounding the conditioning box and the fluid circulating in the circuit. Thus, in the event of a leak of hazardous fluid appearing in the conditioning box, the propagation of the leak is advantageously slowed down, which makes it possible to delay the contact between the hazardous fluid and the air. Slowing down the propagation of the leak of hazardous fluid also saves time to enable intervention by implementing countermeasures, for example by cutting off the circulation of the hazardous fluid in the portion.

[0016] A viscous fluid or a solid with limited porosity also allows the buffer element to limit the flow rate of a leak by filling, for example, a breach caused by high-energy debris, for example coming from a rotating part of a turbomachine of the aircraft. The buffer element thus makes it possible to fulfill a role similar to a patch by limiting the quantity of fluid at risk evacuated through the breach, which makes it possible to limit the concentration of fluid at risk.

[0017] A porous solid element has the advantage of both limiting the propagation of the fluid at risk while being able to absorb part of the fluid at risk in the event of a leak, which limits the flow rate of the leak.

[0018] The buffer element also makes it possible to limit the volume of air in the conditioning box, which limits the risk of reaction with a risky fluid, for example a flammable gas.

[0019] In addition, the buffer element being an inert component, it makes it possible to further limit the flammability of the risky fluid mixture with air even when its concentration is not limited. The inert buffer element also makes it possible to form effective thermal insulation around the portion of the fluid circuit.

[0020] Preferably, in the event of the possibility of a breach occurring caused by high-energy debris, the viscosity of the fluid in the buffer element is chosen as a function of: the dimensions of the potential debris and therefore the breach which may appear in the conditioning box due to the projection of said debris, and the time taken to isolate the leak caused.

[0021] In one embodiment, the buffer element is an intumescent material, capable of expanding under the effect of heat. Such a material makes it possible to form a lightweight buffer element which makes it possible to limit the mass of the aircraft while effectively securing the fluid circuit at risk. In addition, in the event of the appearance of a breach generated by the projection of high-energy debris for example, an intumescent material makes it possible, thanks to the heat generated by the high-energy debris, to effectively participate in sealing the breach.

[0022] Preferably, the buffer element in the form of an intumescent material is an element in a malleable state before compression and heating and in a hardened state after compression and heating. More preferably, the buffer element expands at a temperature between 250 and 1500°C.

[0023] Preferably, the buffer element in the form of an intumescent material is a polymer material comprising at least one component from each of the following categories: • an acid, preferably boric acid, phosphoric acid or sulfuric acid, or a source of organic acid, preferably urea phosphates or melamine phosphates, or a source of inorganic acid, preferably ammonium borates, ammonium phosphate, diammonium phosphate, ammonium polyphosphate or ammonium sulfate, • a carbon source component, preferably a polyalcohol capable of dehydration, more preferably pentaerythritol, a simple sugar (arabinose, maltose) or a polysaccharide (cellulose, starch), and • a blowing component configured to generate non-combustible gases under the effect of heat, preferably melamine (NH3, H2O, CO2), guanidine (NH3, H2O, CO2) or urea (NH3, H2O, CO2).

[0024] In an alternative embodiment, the buffer element is a non-Newtonian fluid whose viscosity increases when it is subjected to a force. An increased viscosity, under the effect of the projection of high-energy debris for example, makes it possible to lower the volume of air near the fluid at risk, which is particularly advantageous for limiting the concentration of air in contact with a reducing fluid. In addition, after the passage of the high-energy debris, that is to say when it is no longer subjected to the force generated by the debris, the non-Newtonian fluid, by returning to a state of lowered viscosity, has the advantage of being able to limit the flow rate of the leak by at least partially plugging the breach caused by the high-energy debris.

[0025] In one embodiment, the buffer element is in the form of a gelatin, which makes it possible to limit the volume of air near a leak of hazardous fluid. A gelatin also makes it possible to ensure that a narrower passage is formed for the hazardous fluid in the event of a leak, making it possible to limit its flow rate.

[0026] Alternatively, the buffer element is in the form of a powder, which makes it possible to limit the volume of air near a risky fluid leak. A solid powder also has the advantage of being practical to store while presenting a limited risk of alteration.

[0027] In an alternative embodiment, the buffer element comprises a combination of one or more fluid element(s) having a dynamic viscosity of between 103 and 103 Pa.s and / or one or more solid element(s) having a porosity rate of less than or equal to 80%. The buffer element thus has optimal properties for slowing the spread of fluid at risk in the event of a leak while forming a buffer element whose mass is limited and which also makes it possible to limit the risks of flammability.

[0028] According to one aspect, the packaging volume is entirely filled by the buffer element, allowing a packaging box that is simple to implement and mount around the portion of the fluid circuit.

[0029] Alternatively, the conditioning box comprises an inner wall and an outer wall extending around the inner wall, an inner conditioning volume being defined between the portion of the fluid circuit and the inner wall and an outer conditioning volume being defined between the inner wall and the outer wall, the inner conditioning volume having a pressure strictly lower than atmospheric pressure, the buffer element completely filling the outer conditioning volume.

[0030] Such an embodiment makes it possible to form around the portion of the fluid circuit both a volume filled by the buffer element to slow the propagation of risky fluid in the conditioning box and a vacuum volume to increase the inerting and thermal insulation of the portion of the fluid circuit.

[0031] Alternatively, the conditioning box comprises an inner wall and an outer wall extending around the inner wall, an inner conditioning volume being defined between the portion of the fluid circuit and the inner wall and an outer conditioning volume being defined between the inner wall and the outer wall, the buffer element completely filling the inner conditioning volume, the securing system comprising a device for ventilating the outer conditioning volume.

[0032] Such an embodiment makes it possible to form around the portion to be secured both a volume filled by the buffer element to slow the propagation of risky fluid in the packaging box and a ventilated volume to evacuate any leak which might come out of the volume containing the buffer element, so as to limit its concentration in the air in a confined space.

[0033] In an alternative embodiment, the packaging volume comprises both an interior packaging volume, an intermediate packaging volume extending around the interior packaging volume, and an exterior packaging volume extending around the intermediate packaging volume, the buffer element completely filling the intermediate packaging volume, the interior packaging volume having a pressure strictly lower than atmospheric pressure and the securing system comprising a device for ventilating the exterior packaging volume.The securing system thus makes it possible to form around the portion to be secured both a vacuum volume to thermally insulate the portion, a volume filled by the buffer element to slow the spread of risky fluid in the conditioning box and a ventilated volume to evacuate any leak that might come out of the volume containing the buffer element, so as to limit its concentration in the air in a confined space.

[0034] In one embodiment, the conditioning box is made from a composite material comprising reinforcing fibers impregnated in a polymer resin, making it possible to limit the propagation of stresses in the event of cracks while forming a lightweight safety system. The conditioning box is thus also advantageously airtight and sealed against the buffer element.

[0035] Preferably, the safety system comprises a device for detecting a leak of fluid at risk, so as to allow the implementation of countermeasures in the event of detection of a leak, in particular, a power cut. in fluid.

[0036] Preferably, the sensing device is mounted in the fluid circuit and is configured to measure a pressure difference with a predetermined pressure.

[0037] Alternatively, the detection device is mounted in the conditioning box and is configured to measure, in the conditioning box, a pressure difference with a predetermined pressure.

[0038] The invention also relates to an aircraft comprising a fluid circuit in which a fluid at risk circulates and comprising a portion to be secured, and a system for securing the portion of the fluid circuit as described previously.

[0039] The invention also relates to a method of mounting a security system as described above, the method comprising the steps of: • position the conditioning box around the portion of the fluid circuit, • inject the buffer element into at least part of the packaging volume, and • close the packaging box tightly.

[0040] Finally, the invention relates to a method for using a safety system as described above, the method comprising a step consisting of propagating a leak of fluid at risk in the packaging volume delimited by the packaging box, the flow rate of the leak being limited thanks to the buffer element. PRESENTATION OF THE FIGURES

[0041] 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.

[0042] [Fig.l] is a schematic representation of an aircraft comprising a fuel circuit for supplying two propulsion turbomachines.

[0043] [Fig.2] is a schematic representation of a turbomachine of [Fig.l] in which a safety system according to one embodiment of the invention is mounted.

[0044] [Fig.3] is a close-up view of the securing system of [Fig.2].

[0045] [Fig.4] is a view along a cross-sectional plane of the securing system of [Fig.2].

[0046] [Fig. 5] is a schematic representation along a cross-sectional plane of a security system according to a second embodiment of the invention.

[0047] [Fig. 6] is a schematic representation along a cross-sectional plane of a security system according to a third embodiment of the invention.

[0048] [Fig.7] represents a diagram of the steps of a method of mounting the security system of [Fig.3].

[0049] [Fig.8] represents a diagram of the steps of a method of using the security system of [Fig.3].

[0050] 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

[0051] With reference to [Fig. 1], there is shown an aircraft A comprising a plurality of turbomachines M.

[0052] As is known, the turbomachine M allows the movement of the aircraft A from the acceleration of an upstream to downstream air flow.

[0053] For this, with reference to [Fig. 2], the turbomachine M comprises a propulsion member 91, mounted on a propulsion shaft 92, which converts the rotational movement into an air flow which enables the propulsion of the aircraft A. To drive the rotation of the propulsion member 91, the turbomachine M successively comprises from upstream to downstream along a longitudinal axis X, a compression module 93, a combustion chamber 94 and a turbine stage 95. The compression module 93 is configured to receive an incoming air flow and compress it so as to supply the combustion chamber 94. The combustion, in the combustion chamber 94, between a fuel flow and the compressed air flow generates an exhaust air flow which drives the turbine stage 95 in rotation to generate the thrust of the aircraft.The rotation of the turbine stage 95 then causes the rotation of the propulsion shaft 92, which in turn drives the compression module 93 and the propulsion member 91.

[0054] In practice, in the turbomachine M, a failure may occur at the level of the rotating elements, for example in the rotating parts of the compression module 93, which may lead to the ejection of high-energy debris. As is known and shown in [Fig. 2], in the turbomachine M, the debris may be projected according to a zone called the “burst zone” ZE. The burst zone ZE extends in a space between an upstream plane PI and a downstream plane P2 extending radially from the propulsion shaft 92 respectively directly upstream of the propulsion member 91 and directly downstream of the turbine stage 95, each plane PI, P2 being inclined at an angle of +5° respectively upstream of the propulsion member 91 and downstream of the turbine stage 95. In the event of projection of high-energy debris into the burst zone ZE, the turbomachine M may be damaged, as will be described in more detail below.

[0055] As shown in Figures 1 and 3, the turbomachine M is powered by fuel Q from a tank R of fuel Q. In this example, fuel Q is dihydrogen but it goes without saying that the invention applies to any type of high-risk fuel, in particular methane. In general, the invention applies to any circuit for transporting a high-risk fluid.

[0056] 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 of the turbomachine M, the fuel Q must be heated.

[0057] For this, with reference to [Fig. 3], the aircraft A comprises a fuel circuit 1 which connects the cryogenic tank R to the turbomachine M. The fuel circuit 1 comprises a portion IP capable of generating fuel leaks which must be contained to ensure the safety of the aircraft A. In practice, the leaks may be due to a malfunction of the rotating parts of the turbomachine M and to the projection of debris into the burst zone ZE. In this example, as shown in [Fig. 2], the portion IP extends into the turbomachine M and more precisely into the burst zone ZE of the turbomachine M. It goes without saying that the portion IP could extend to a different location in the fuel circuit 1, between the cryogenic tank R and the combustion chamber of the turbomachine M. Similarly, it goes without saying that the fuel leak could come from a failure specific to the fuel circuit 1.The IP portion extends in this example to ambient air.

[0058] In this example, the IP portion comprises several pieces of equipment such as a mechanical pump PO, a control valve W, a heat exchanger EC, etc. It goes without saying that the IP portion could comprise a variety of pieces of equipment. Similarly, it goes without saying that the fuel circuit 1 may comprise a plurality of IP portions capable of generating fuel leaks Q.

[0059] As shown in Figures 2 and 3, the IP portion of the fuel circuit 1 is secured by a security system 2 which will now be presented in detail.

[0060] With reference to [Fig. 3], the securing system 2 comprises a conditioning box 3, mounted around the portion IP of the fuel circuit 1 to be secured, and a buffer element 4 which at least partially fills the conditioning box 3.

[0061] The conditioning box 3 defines around the portion IP of the fluid circuit 1 a closed and sealed enclosure.

[0062] The dimensions of the conditioning box 3 are determined to correspond to the portion IP of the fuel circuit 1 to be secured. In particular, the dimensions of the conditioning box 3 are determined, in this example, to extend around the portion IP in the burst zone ZE.

[0063] The packaging box 3 is preferably made of a rigid material, in order to protect the IP portion of the fuel circuit 1 effectively. More preferably, the conditioning box 3 is made of a material that is airtight and impermeable to the buffer element 4. In this example, the outer box 3 is made of a composite material comprising reinforcing fibers impregnated in a polymer resin, for example carbon, glass or aramid fibers impregnated in an epoxy resin. Such materials make it possible to limit the propagation of stresses in the event of cracks, for example, the crack being able to come from high-energy debris resulting from a failure in one of the rotating parts of the turbomachine M, while limiting the resistance to the penetration of the debris.

[0064] A conditioning volume 30 is defined between the portion 1P of the fluid circuit 1 and the conditioning box 3.

[0065] In a first embodiment, with reference to [Fig. 4], the conditioning box 3 comprises a single outer wall 31, mounted around the portion IP. In this embodiment, a single conditioning volume 30 is defined between the portion 1P of the fluid circuit 1 and the outer wall 31 of the conditioning box 3. The buffer element 4 then fills the entire conditioning volume 30.

[0066] In a second embodiment, with reference to Figures 5 and 6, the packaging box 3 comprises an outer wall 31 and an inner wall 32, the outer wall 32 extending around the inner wall 32, so as to form a double-walled packaging box 3.

[0067] In this embodiment, the conditioning volume 30 comprises an interior conditioning volume 30i, defined between the portion IP of the fluid circuit 1 and the interior wall 31, and an exterior conditioning volume 30e, defined between the interior wall 31 and the exterior wall 32.

[0068] In a first embodiment shown in [Fig. 5], the buffer element 4 fills the entire outer packaging volume 30e. The inner packaging volume 30i preferably has a pressure strictly lower than atmospheric pressure, so as to place the inner packaging volume 30i under vacuum to thermally isolate the portion IP of the fluid circuit 1. In this example, the inner packaging volume 30i has a pressure of between 10 4 and 102 Pa.

[0069] In a second embodiment shown in [Fig. 6], the buffer element 4 fills the entire interior conditioning volume 30i. The exterior conditioning volume 30e preferably comprises a ventilation device 6, to make it possible to limit the concentration of fuel Q in a confined space inside the conditioning box 30. The ventilation device 6 may be in the form of air or nitrogen ventilation by means of scoops or a dedicated circulation system, for example.

[0070] According to a preferred aspect, with reference to [Fig. 3], the packaging box 3 comprises a filling orifice 34, configured to cooperate with a tool, for example an injection nozzle, and to allow the introduction of the buffer element 4 into the packaging volume 30. The filling orifice 34 is preferably resealable in a sealed manner.

[0071] Preferably, still with reference to [Fig. 3], the conditioning box 3 comprises a first sealing member 33A mounted at an upstream end 1A of the portion IP of the fuel circuit 1, corresponding to the inlet of the portion IP into the outer box 3, and a second sealing member 33B mounted at a downstream end 1B of the portion IP of the fuel circuit 1, corresponding to the outlet of the portion IP of the outer box 3.In this example in which the portion IP comprises a heat exchanger EC, configured to heat the fuel flow Q from calories transferred by a hot source via a circulation loop of a heat transfer fluid FC, the conditioning box 3 also comprises a third sealing member 33C mounted at an inlet in the conditioning box 3 of a heat transfer fluid circuit FC and a fourth sealing member 33D mounted at an outlet of the heat transfer fluid circuit FC of the conditioning box 3. It goes without saying that the conditioning box 3 can comprise a different number of sealing members 33. 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 conditioning box 3, the latter comprises as many sealing members 33.

[0072] In this example, each sealing member 33 is in the form of an elastic seal, preferably an O-ring or a bi-cone seal.

[0073] Preferably, the conditioning box 3 comprises an access 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 access opening is closable in a sealed manner. The access 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.

[0074] As described previously, the security system 2 comprises a buffer element 4 mounted in the packaging box 3 and which at least partially fills the packaging volume 30.

[0075] According to one aspect of the invention, the buffer element 4 is an inert component, so as to limit any risk of contact between the fuel flow Q and an air flow. More specifically, the buffer element 4 comprises one or more solid material(s) having a porosity rate of less than or equal to 80% and / or one or more fluid material(s) having a viscosity of between 103 and 103 Pa.s. Thanks to such mechanical characteristics, the buffer element 4 is configured to slow down the speed of movement of the fuel flow Q in the conditioning box 3 in the event of a leak, so as to delay contact between the fuel flow Q and an air flow. The buffer element 4 having such characteristics also makes it possible to limit the flow rate of a leak by at least partially sealing a breach caused by high-energy debris for example, as will be described in more detail below.

[0076] In practice, the buffer element 4 may comprise a solid material, a liquid material or a combination of several solid materials, several liquid materials or one or more solid materials and one or more liquid materials as described above.

[0077] In particular, in one embodiment, the buffer element 4 comprises an intumescent material, capable of expanding under the effect of heat. Preferably, the intumescent material is initially in a malleable state and is configured to expand and harden under the effect of heat. Thus, when high-energy debris is projected, the latter generates heat, which, upon contact with the intumescent material, causes it to expand, thus limiting the volume of propagation of the leak and the quantity of air in the vicinity of the leak. In this example, the intumescent material is configured to expand at a temperature between 250 and 1500°C. Once heated and compressed, the intumescent material is in a hardened state. By way of example, the intumescent material is a polymer material comprising at least one component from each of the following categories: • an acid, preferably boric acid, phosphoric acid or sulfuric acid, or a source of organic acid, preferably urea phosphates or melamine phosphates, or a source of inorganic acid, preferably ammonium borates, ammonium phosphate, diammonium phosphate, ammonium polyphosphate or ammonium sulfate, • a carbon source component, preferably a polyalcohol capable of dehydration, more preferably pentaerythritol, a simple sugar (arabinose, maltose) or a polysaccharide (cellulose, starch), and • a blowing component configured to generate non-combustible gases under the effect of heat, preferably melamine (NH3, H2O, CO2), guanidine (NH3, H2O, CO2) or urea (NH3, H2O, CO2).

[0078] Alternatively or additionally, the buffer element 4 comprises a non-Newtonian fluid, that is to say a fluid which does not follow Newton's law of viscosity. In other words, a non-Newtonian fluid is in the liquid or viscous state when it is not subjected to any force and its viscosity depends on the stress to which it is subjected. Thus, in the event of debris being projected, the latter, upon coming into contact with the buffer element 4, will have the effect of increasing its viscosity, which will reduce the kinetic energy of the debris while limiting the volume of air near the leak caused by the debris.

[0079] Alternatively or additionally, the buffer element 4 comprises a material in the form of a gelatin, which has a high viscosity. In the event of a leak, a gelatin makes it possible to limit the volume of the leak by limiting its passage.

[0080] Alternatively or additionally, the buffer element 4 comprises a material which is in the form of a powder, so as to limit the volume of air around the fuel Q in the event of a leak. In addition, in the event of the appearance of debris passing through the conditioning box 3, the buffer element 4 in the form of powder will at least partially fill the gap caused by the debris, which will limit the leak.

[0081] Thanks to the buffer element 4, in the event of projection of debris causing a crack in the fuel circuit 1 and in the walls of the conditioning box 3, thus causing a fuel leak Q escaping from the portion IP of the fuel circuit 1, the fuel leak Q is propagated in the conditioning box 3 through the buffer element 4 and its flow rate as well as its propagation speed are advantageously limited. This makes it possible to delay the contact between the fuel flow Q and the air. In addition, thanks to its properties, the buffer element 4 is capable of at least partially sealing the crack to limit the flow rate of the fuel leak Q.

[0082] Preferably, still with reference to [Fig. 3], the safety system 2 comprises a device 5 for detecting a fuel leak Q. In this example, the detection device 5 is mounted in the fuel circuit 1 and is configured to measure, for example, a pressure difference with a predetermined pressure. The detection device 5 could alternatively be mounted in the conditioning box 3.

[0083] Preferably, the safety system 2 comprises a leak warning and isolation device (not shown), so as to limit the fuel leak Q. In this example, the detection device is in the form of a pressure sensor connected to a computer (also not shown) of the aircraft. The computer is configured to emit a warning signal, in particular to the pilot. Preferably, the computer is configured to command, for example, a stoppage of the circulation of fuel Q in the portion IP of the fuel circuit 1.

[0084] A method of mounting the safety system 2 as described above will now be described, with reference to [Fig. 7]. In this example, the conditioning box 3 comprises a single outer wall 31 defining a single conditioning volume 30 between the IP portion of the fuel circuit 1 and the wall exterior 31.

[0085] In a first step E1, the portion IP of the fuel circuit 1 is positioned in the conditioning box 3. In practice, the portion IP is inserted through the access opening (not shown). Each sealing member 33A, 33B, 33C, 33D is then mounted respectively at the upstream end IA and the downstream end IB of the portion IP of the fuel circuit 1 and at the inlet and outlet of the heat transfer fluid circuit FC in the conditioning box 3.

[0086] An operator then injects, in a second step E2, the buffer element 4 into the conditioning box 3, so as to fill the conditioning volume 30. In this example, the buffer element 4 is in the form of a viscous fluid, for example sprayed into the conditioning volume 30 via the insertion orifice 34 by means of a pressurized injection nozzle.

[0087] When the buffer element 4 completely fills the conditioning volume 30, the insertion orifice is sealed and the conditioning box 3 forms a sealed enclosure around the portion IP of the fuel circuit 1 filled by the buffer element 4.

[0088] A method of using the security system 2 as described previously with reference to [Fig.8] will now be described.

[0089] In this example, one of the rotating parts of the turbomachine M suffered a failure and debris from this rotating part was projected into the burst zone ZE. The debris passed through the portion IP of the fuel circuit 1 and the conditioning box 3, causing the formation of a breach, for example, in a pipe of the portion IP and in the conditioning box 3. In this example, the conditioning box 3 is manufactured from a composite material configured to limit the propagation of the crack in the outer wall 31 and to limit the stresses in the conditioning box 3. The crack in the portion IP of the fluid circuit 1 causes the appearance of a leak F of fuel Q in the conditioning volume 30 of the conditioning box 3.

[0090] In a first step EA, the leak F of fuel Q propagates in the conditioning volume 30 through the buffer element 4. Thanks to its mechanical properties, for example dynamic viscosity between 103 and 103 Pa.s, the flow rate of the leak F in the buffer element 4 is limited. Its propagation speed is therefore also advantageously limited. In addition, thanks to an inert buffer element 4, the concentration of fuel Q in the air is below a detonating threshold.

[0091] The detection device 5 mounted in the portion IP measures in parallel the pressure in the fuel circuit 1 and detects the leak, in a step EB. In this example, the detection device 5 then emits an alert signal, via a computer. In particular, the alert signal is received by the pilot who can then implement countermeasures, for example by ordering a stoppage of the fuel flow Q in the IP portion of the fuel circuit 1.

[0092] Thanks to the safety system 2 according to the invention and in particular to the buffer element 4 as described previously, the propagation of the fuel leak Q is slowed down, which makes it possible to delay the encounter between the fuel leak Q and an air flow A. The pilot thus has time to implement the countermeasures to isolate the leak F reliably and effectively.

Claims

Claims

1. System (2) for securing a portion (IP) of a fluid circuit (1) in which a fluid at risk for aircraft circulates, the securing system (2) comprising: • a conditioning box (3) configured to be mounted around the portion (IP) of the fluid circuit (1), a conditioning volume (30) being defined between the portion (IP) and the conditioning box (3), • at least one buffer element (4) at least partially filling the conditioning volume (30), • the securing system (2) being characterized in that the buffer element (4) is an inert component comprising at least one of a fluid element having a dynamic viscosity of between 103 and 103 Pa.s or of a solid element having a porosity rate of less than or equal to 80%, so as to limit the propagation speed in the conditioning volume (30).

2. Securing system (2) according to claim 1, in which the buffer element (4) is an intumescent material, capable of expanding under the effect of heat.

3. A securing system (2) according to claim 1, wherein the buffer element (4) is a non-Newtonian fluid.

4. Securing system (2) according to one of claims 1 to 3, in which the packaging volume (30) is entirely filled by the buffer element (4).

5. Securing system (2) according to one of claims 1 to 3, in which the conditioning box (3) comprises an inner wall (31) and an outer wall (32) extending around the inner wall (31), an inner conditioning volume (30i) being defined between the portion (IP) of the fluid circuit (1) and the inner wall (31) and an outer conditioning volume (30e) being defined between the inner wall (31) and the outer wall (32), the inner conditioning volume (30i) having a pressure strictly lower than atmospheric pressure, the buffer element (4) completely filling the outer conditioning volume (30e).

6. Securing system (2) according to one of claims 1 to 3, wherein the conditioning box (3) comprises an inner wall (31) and an outer wall (32) extending around the inner wall (31), an inner conditioning volume (30i) being defined between the portion (IP) of the fluid circuit (1) and the inner wall (31) and an outer conditioning volume (30e) being defined between the inner wall (31) and the outer wall (32), the buffer element (4) completely filling the inner conditioning volume (30i), the securing system (2) comprising a ventilation device (6) for the outer conditioning volume (30e).

7. Securing system (2) according to one of claims 1 to 6, in which the packaging box is made from a composite material comprising reinforcing fibers impregnated in a polymer resin.

8. Securing system (2) according to one of claims 1 to 7, the securing system (2) comprising a device (5) for detecting a leak of fluid at risk.

9. Aircraft comprising a fluid circuit, in which a fluid at risk circulates and comprising at least one portion to be secured, and a system for securing the portion of the fluid circuit according to one of claims 1 to 8.

10. Method for mounting a security system (2) according to one of claims 1 to 8, the method comprising the steps of: • positioning (El) the conditioning box (3) around the portion (IP) of the fluid circuit (1), • injecting (E2) the buffer element (4) into at least part of the conditioning volume (30), and • closing the conditioning box (3) in a sealed manner.

11. Method of using a security system (2) according to one of claims 1 to 8, the method comprising a step consisting of propagating a leak (F) of fluid at risk in the packaging volume (30) delimited by the packaging box (3), the flow rate of the leak (F) being limited by means of the buffer element (4).

Images