System for safing a circuit of risk-posing fluid, and associated method

Abstract

A system (2) for safing a portion (1P) in which an aircraft risk-posing fluid circulates, the safing system (2) comprising a conditioning box (3) configured to be mounted around the portion (1P) of the fluid circuit (1), an inert fluid (4) filling a conditioning volume (30) defined between the portion (1P) and the conditioning box (3); a cooling circuit (5) for cooling the inert fluid (4) that is fluidically connected to the conditioning box (3) so as to form a sealed loop for circulating the inert fluid (4); a mechanical pump (6) mounted on the cooling circuit (5) and configured to circulate the inert fluid (4) in the cooling circuit (5) and in the conditioning box (3) and a heat exchanger (7) mounted on the cooling circuit (5) and configured to cool the inert fluid (4).

Description

Safety system for a hazardous fluid circuit and associated process

[0001] The present invention relates to the field of securing installations through 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 different countries. 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 less energy-intensive and 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 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, particularly 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, such as 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 and delivered to the turbomachine via a fuel circuit. The fuel circuit comprises several pipes and components, such as a mechanical pump to circulate the fuel through the circuit's pipes, and a heat exchanger to preheat the fuel before injection into the turbomachine's combustion chamber.

[0008] In practice, because the hydrogen molecule is very small, the connections between equipment and piping cannot be completely airtight. In other words, it is not possible to guarantee the absence of fuel leaks in the fluid circuit, which can be a significant drawback. Such fuels are flammable gases and can detonate upon contact with air. Therefore, to ensure the safe use of hydrogen for aeronautical applications, it is necessary to control the generation of fuel leaks into the air, as well as their potential effects.

[0009] In this regard, systems exist that ensure continuous ventilation when the fuel circuit is pressurized, thus limiting fuel accumulation in a relatively confined environment in the event of a leak. For example, hydrogen is a gas that can become flammable if its concentration in air exceeds 4%. Continuous ventilation eliminates the risk of fuel reaching such concentrations. However, the airflow required to generate this ventilation is drawn from the airflow entering the turbomachine, resulting in reduced turbomachine efficiency. Furthermore, the fuel leak could come into contact with hot equipment, which is undesirable.

[0010] It is also known to use so-called "double-walled" fuel lines, in which an inner line allows fuel circulation and an outer line, usually under vacuum, contains the fuel in case of a leak in the inner line. However, double-walled fuel lines significantly increase the aircraft's mass. Furthermore, these lines have a larger diameter, and their installation in a turbomachine, with its often congested environment, is complex. In addition, it is not possible to reliably contain a leak, for example, if the outer line is damaged.

[0011] The invention aims to eliminate at least some of these drawbacks by providing a reliable and efficient system for securing a hazardous fluid transport circuit in an aircraft. In particular, the invention aims to limit the risk of contact between the hazardous fluid and the air in the turbomachine, while also limiting the risk of overheating around the hazardous fluid circuit.

[0012] Incidentally, documents US2023043843A1 and EP4311778A1 describe an aircraft fuel system that includes a sealed chamber mounted around one or more components of the fuel system. The sealed chamber is filled with an inert gas or placed under vacuum. PRESENTATION OF THE INVENTION

[0013] The invention relates to a system for securing a portion of a fluid circuit in which a fluid posing a risk to aircraft circulates, the security system comprising: a sealed 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, an inert fluid filling at least part of the conditioning volume, the security system being remarkable in that it comprises at least: a cooling circuit for the inert fluid fluid fluidly connected to the conditioning box, the cooling circuit being connected, on the one hand, to an outlet of the conditioning box and, on the other hand, to an inlet of the conditioning box, so as to form a sealed loop for the circulation of the inert fluid between the conditioning box and the cooling circuit,a mechanical pump mounted on the cooling circuit and configured to circulate the inert fluid in the cooling circuit and in the conditioning unit, and a heat exchanger mounted on the cooling circuit and configured to cool the fluid by transferring heat with a heat transfer fluid.

[0014] The use of a conditioning unit eliminates various leaks in a constrained environment with diverse equipment, such as an aircraft turbomachine. This allows, for example, leaks to be treated very close to a turbomachine's combustion chamber, avoiding the need for heavy and cumbersome double-walled piping, unlike prior art systems.

[0015] In the event of overheating of the equipment in the section of the fluid circuit requiring protection, or of the environment in which this section of the fluid circuit is installed, the protection system advantageously cools the inert fluid in the conditioning chamber. This prevents any risk of the hazardous fluid leaking into an excessively hot environment should damage occur. The cooling circuit associated with the heat exchanger draws inert fluid from the conditioning chamber and reinjects cooled inert fluid to maintain a sufficiently low temperature around the section of the fluid circuit.

[0016] Furthermore, while securing the portion of the fluid circuit, the safety system advantageously allows for the dissipation of heat generated by the turbomachine using a compact system. In other words, the turbomachine's cooling function is effectively performed by the inert fluid, unlike prior art circuits where this function was achieved by an airflow.

[0017] Cooling the inert fluid also cools the walls of the equipment in the fluid circuit section. This eliminates the need to limit the temperature of the equipment walls in the fluid circuit section, as was the case in prior art, to mitigate the risk of auto-ignition of the hazardous fluid. This also eliminates the need to limit the temperature of the hazardous fluid in the fluid circuit section.

[0018] A closed-loop system between the conditioning unit and the cooling circuit also helps to limit the amount of inert fluid used, which advantageously limits the costs of the safety system.

[0019] Furthermore, thanks to the safety system according to the invention, the turbomachine maintains optimal efficiency, since its performance is not limited by the extraction of an air flow, for example, as was the case in the prior art.

[0020] In a preferred embodiment, the heat transfer fluid circulating in the heat exchanger to cool the inert fluid is the hazardous fluid, thus eliminating the need for a dedicated heat transfer fluid circulation loop. This also allows the hazardous fluid to be preheated, which is particularly advantageous when it is a fuel stream from a cryogenic tank that must be heated before being introduced into the turbomachine's combustion chamber.

[0021] Preferably, the safety system includes a control valve mounted on the cooling circuit and configured to allow or prevent the circulation of the inert fluid within the cooling circuit. Such a control valve allows the inert fluid cooling to be adapted as needed. In particular, for example, depending on the aircraft's operating phases, during which the equipment in the critical fluid circuit typically operates at varying speeds, resulting in varying degrees of equipment heating, the control valve allows the inert fluid to be cooled intermittently or continuously. Intermittent control of the control valve also helps to limit the costs associated with the mechanical pump's consumption for circulating the inert fluid in the circulation loop.The overall energy consumption of the security system is therefore less than the energy consumption required in prior art systems.

[0022] In one preferred configuration, the safety system includes a temperature sensor mounted within the conditioning chamber and configured to measure the temperature of the inert fluid within the chamber, thus detecting any overheating of the inert fluid. The flow rate of the mechanical pump can then be advantageously regulated based on the fluid temperature. If a control valve is installed, its opening can be triggered, for example, when the inert fluid reaches a predetermined temperature. This ensures optimal temperature control.

[0023] Alternatively or in addition, the safety system includes at least one temperature sensor configured to be mounted on at least one of the pieces of equipment in the portion of the fluid circuit to be secured and to measure the temperature of said equipment, so as to detect an increase in its temperature and adapt the cooling of the inert fluid accordingly.

[0024] In one embodiment, the safety system includes at least one detection device for detecting the presence of hazardous fluid or air in the air conditioning unit, so as to prevent a leak. In one aspect, the detection device is mounted in the air conditioning unit and / or in the cooling circuit.

[0025] In a first embodiment, the detection device is a detector of the presence of hazardous fluid, for example a hydrogen sensor, capable of detecting a concentration of hazardous fluid, for example greater than or equal to a predetermined threshold.

[0026] As a complementary or alternative method, the detection device is an oxygen sensor, capable of detecting an oxygen concentration, for example, greater than or equal to a predetermined threshold.

[0027] In one preferred configuration, the safety system includes a computer designed to control at least the mechanical pump, thereby regulating the flow rate of the inert fluid in the cooling circuit. This allows the temperature of the potentially hazardous fluid in the heat exchanger to be regulated by adjusting its flow rate.

[0028] In the embodiment where the safety system includes a temperature sensor, the control unit is also configured to detect a temperature greater than or equal to a predetermined threshold. Preferably, the control unit is also configured to control a regulating valve to allow the circulation of the inert fluid in the cooling circuit, thereby lowering its temperature. This allows the cooling system to be activated or deactivated.

[0029] In the embodiment in which the security system includes a detection device, the computer is also configured to detect a concentration of air and / or hazardous fluid greater than or equal to a predetermined threshold, and to emit an alert signal, so as to allow the implementation of countermeasures.

[0030] According to one aspect, the safety system includes: an inert fluid reservoir fluidically connected to the conditioning unit or cooling circuit, and an injection valve configured to allow or prohibit the injection of inert fluid from the inert fluid reservoir into the conditioning unit or cooling circuit.

[0031] The inert fluid reservoir allows, in the event of a leak for example, the injection of inert fluid into the air conditioning chamber to lower the concentration of air and / or hazardous fluid. A virtually constant volume of inert fluid is thus maintained within the air conditioning chamber, ensuring aircraft safety, for example, while awaiting countermeasures. The inert fluid reservoir also serves as a useful backup.

[0032] In one embodiment, the safety system includes a purge valve or a pressure relief valve connected to a hazardous fluid evacuation circuit, so as to evacuate a hazardous fluid leak present in the conditioning chamber.

[0033] The invention also relates to an aircraft comprising a fluid circuit linking a cryogenic tank to a combustion chamber of an aircraft turbomachine in order to supply it with a hazardous fluid, the aircraft comprising at least one safety system as described above securing a portion of the fluid circuit.

[0034] According to a preferred configuration, the aircraft comprises a primary and a secondary flow separated by an intermediate casing, with the conditioning unit located within this intermediate casing. The conditioning unit is thus mounted in an area close to the combustion chamber, and therefore in a hot zone where fluid management is complex. A portion of a potentially hazardous fluid circuit installed in a complex and congested environment can be advantageously and effectively secured.

[0035] Preferably, the mechanical pump is positioned remotely from the turbomachine, allowing for the cooling of a portion of the potentially hazardous fluid circuit, even when installed in a confined and cluttered environment. Advantageously, part of the cooling circuit is mounted outside the turbomachine.

[0036] Finally, the invention relates to a method of using a safety system as described above, the method of use comprising the steps of: circulating the inert fluid from the conditioning box in the cooling circuit, cooling the inert fluid in the heat exchanger by heat transfer with a heat transfer fluid before being reintroduced into the conditioning box. PRESENTATION OF THE FIGURES

[0037] 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.

[0038] This is a schematic representation of an aircraft including a fuel circuit to power two propulsion turbomachines.

[0039] This is a schematic representation of a turbomachine and a system for securing a portion of the fluid circuit according to one embodiment of the invention.

[0040] This is a close-up view of the security system.

[0041] This is a schematic representation of a security system according to an alternative implementation form.

[0042] It should be noted that the figures explain the invention in detail for implementing the invention, said figures being of course able to serve to better define the invention where appropriate. DETAILED DESCRIPTION OF THE INVENTION

[0043] With reference to the, there is represented an aircraft A comprising a plurality of turbomachines M.

[0044] As is known, the turbomachine M enables the movement of aircraft A by accelerating an airflow. To this end, the turbomachine M comprises a propulsion unit OP mounted on a drive shaft, which converts rotational motion into an airflow that propels the aircraft.

[0045] To drive the rotation of the propulsion unit OP, the turbomachine M comprises, successively along a longitudinal axis X, a compression stage CO, a combustion chamber CC, and a turbine stage TU. The compression stage CO is configured to receive an incoming airflow, corresponding in this example to a portion of the airflow from the propulsion unit OP, and compress it to supply the combustion chamber CC. Combustion in the combustion chamber CC, between a fuel flow Q and the compressed air flow, generates an exhaust airflow that drives the turbine stage TU in rotation, which, via the drive shaft, drives the compression stage CO and the propulsion unit OP.

[0046] In this example, the turbomachine M is a dual-flow turbomachine, in which the compression stage CO, the combustion chamber CC, and the turbine stage TU form a primary duct V1 for circulating a primary airflow. The turbomachine M also includes a secondary duct V2 for circulating a secondary airflow accelerated by the propulsion unit OP. An intermediate casing CA is mounted between the primary duct V1 and the secondary duct V2.

[0047] As described previously, in the combustion chamber CC, the air stream is mixed with a fuel stream Q. To achieve this, and again referring to the previous example, the turbomachine M is supplied with a fuel stream Q from a fuel tank R. In this example, the fuel Q is dihydrogen, but it is understood that the invention applies to any type of hazardous fuel, particularly methane. More generally, the invention applies to any system for transporting a hazardous fluid.

[0048] Such fuel Q is stored in 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, as shown in Figures 2 and 3, aircraft A includes a fuel circuit 1 which connects the cryogenic tank R to the combustion chamber CC of the turbomachine M.

[0050] With reference to the diagram, the fuel flow Q circulates from upstream to downstream in the fuel circuit 1 by means of a mechanical pump PO or similar device. The fuel flow Q preferably passes through a heat exchanger EC, in which it exchanges heat with a heat transfer fluid FC to be warmed. In this example, the heat exchanger EC is configured to heat the fuel flow Q to its vaporization temperature. Similarly, in this example, the fuel flow Q is heated in the heat exchanger EC by heat transferred from a heat source in the aircraft, for example, the exhaust gases from the turbine stage TU of the turbomachine M. It is understood that the fuel flow Q could pass through more than one heat exchanger EC to, for example, warm the fuel flow Q progressively. In this example, a control valve W allows the flow rate of the fuel flow Q in the fuel circuit 1 to be controlled.It goes without saying that fuel circuit 1 could include a different number of pieces of equipment.

[0051] In this example, the fuel system 1 includes a portion 1P that is susceptible to fuel leaks Q, which must be contained to ensure aircraft safety. In this example, the control valve W and the heat exchanger EC are mounted on portion 1P of the fuel system 1. It is understood that portion 1P could include a variety of equipment. Similarly, it is understood that the fuel system 1 could include multiple portions 1P that are susceptible to leaks. In this example, portion 1P extends inside the turbomachine M, forming a confined environment.

[0052] More specifically, in this example, portion 1P is located in a compartment of the turbomachine M, specifically in the intermediate casing CA. Such a compartment contains numerous components and is quite large. Furthermore, it is subjected to high temperatures due to its proximity to the combustion chamber CC.

[0053] According to one aspect of the invention, portion 1P of fuel circuit 1 is secured by a security system 2 which will now be presented in detail.

[0054] With reference to the, the security system 2 includes a conditioning box 3, mounted around the portion 1P of the fuel circuit 1 to be secured and filled with an inert fluid 4, and a cooling circuit 5 connected to the conditioning box 3.

[0055] The conditioning unit 3 is positioned, in this example, within the turbomachine compartment M, to eliminate the need for double piping and ensure optimal safety. More specifically, the conditioning unit 3 is positioned, in this example, within the intermediate housing CA, as shown in the figure. It goes without saying that the conditioning unit 3 could alternatively be positioned differently on the fuel circuit 1.

[0056] The conditioning box 3 defines a closed and airtight enclosure around section 1P of the fuel circuit 1. This prevents any contact with air and oxygen that could increase the risk of detonation.

[0057] The dimensions of the conditioning box 3 are determined to correspond to the portion 1P of the fuel circuit 1 to be secured, while allowing the mounting of the conditioning box 3, in this example, in the intermediate casing CA of the turbomachine M.

[0058] Preferably, the conditioning box 3 is made of a material that is airtight, impermeable to inert fluid 4, and impermeable to fuel Q. In one embodiment, the conditioning box 3 is made of a solid material, for example, a composite material comprising reinforcing fibers impregnated in a polymer resin (e.g., carbon, glass, or aramid fibers impregnated in an epoxy resin), which limits crack propagation, for example. Alternatively, the conditioning box 3 is made of a flexible material, for example, a rubber-like polymer, silicone, or TFE (or Teflon®), which allows for easier assembly in a confined environment such as a turbomachine nacelle M. It goes without saying that the conditioning box 3 could be made of a different material.

[0059] A conditioning volume 30 is defined between portion 1P of fluid circuit 1 and conditioning box 3.

[0060] According to one aspect, with reference to the, the conditioning box 3 includes a filling orifice 33, configured to cooperate with a tool, for example an injection nozzle, and to allow the introduction of the inert fluid 4 into the conditioning volume 30. The filling orifice 33 is preferably resealable in a hermetic manner.

[0061] Preferably, the conditioning box 3 comprises a plurality of sealing elements (not shown), mounted at an upstream end and a downstream end of portion 1P of the fuel circuit 1, corresponding to the inlet and outlet of portion 1P in the conditioning box 3. It is understood that the conditioning box 3 may comprise a different number of sealing elements. In particular, the conditioning box 3 comprises as many sealing elements as there are inlets and outlets of fluid circuit lines in the conditioning box 3.

[0062] Preferably, the conditioning unit 3 includes an access opening (not shown), for example a hatch, to allow access to section 1P of the fuel circuit 1, for example for maintenance. The access opening must be able to be sealed tightly.

[0063] As described previously, the safety system 2 includes an inert fluid 4 which at least partially fills the conditioning volume 30. Preferably, the inert fluid 4 completely fills the conditioning volume 30 to limit the concentration of air or oxygen inside the conditioning box 3. The inert fluid 4 helps to limit any risk of contact between the fuel flow Q and an air flow in the event of a leak.

[0064] In this example, inert fluid 4 is chosen from helium, carbon dioxide, or nitrogen. It goes without saying that inert fluid 4 could be different.

[0065] According to one aspect of the invention, the safety system 2 comprises a cooling circuit 5 fluidically connected in a sealed manner to the conditioning box 3. This makes it possible to form a closed cooling loop.

[0066] Preferably, the cooling circuit 5 is made of an airtight and inert fluid-tight material 4. In this example, the cooling circuit 5 includes one or more pipes commonly used in aircraft for transporting fluids. In one aspect, the cooling circuit 5 is made of the same material as the conditioning unit 3, in this example a composite material comprising reinforcing fibers impregnated in a polymer resin. It is understood that the cooling circuit 5 could alternatively be made of a different material.

[0067] As shown in the figure, the cooling circuit 5 is connected, on the one hand, to an outlet 31 of the conditioning box 3 and, on the other hand, to an inlet 32 ​​of the conditioning box 3, so as to form a sealed loop for the circulation of the inert fluid 4 between the conditioning box 3 and the cooling circuit 5. In other words, the inert fluid 4 contained in the conditioning volume 30 is also able to circulate in the cooling circuit 5.

[0068] For this purpose, the safety system 2 includes a mechanical pump 6 mounted on the cooling circuit 5 and configured to circulate the inert fluid 4 both in the cooling circuit 5 and in the conditioning box 3.

[0069] In practice, upon contact with the equipment in section 1P to be secured and the environment of the turbomachine M, the inert fluid 4 heats up, and the cooling circuit 5 is configured to cool it, as will be described in more detail later. This ensures that the inert fluid 4 remains within an acceptable temperature range in which it can optimally neutralize any leakage of hazardous fluid.

[0070] Also, the mechanical pump 6 preferably has a variable flow rate in order to cool the inert fluid 4 to a greater or lesser extent.

[0071] In a preferred embodiment, the mechanical pump 6 is mounted remotely from the turbomachine M, as shown in the figure. This allows for a reduction in space requirements, for example, in the intermediate casing CA, which already houses a significant amount of equipment. It is understood that the mechanical pump 6 could be mounted in a different position, for example, in an external nacelle of the turbomachine M, externally delimiting the secondary flow V2.

[0072] To cool the inert fluid 4, the safety system 2 includes a heat exchanger 7 mounted on the cooling circuit 5 and configured to cool the inert fluid 4 using cooling energy transferred by a heat transfer fluid upstream of the inlet 32 ​​of the conditioning unit 3. In this example, the heat exchanger 7 is a tubular, plate, or finned heat exchanger. It is understood that the heat exchanger 7 can alternatively be of a different form.

[0073] In a preferred embodiment, as shown in the figure, the heat transfer fluid that circulates in the heat exchanger 7 to cool the inert fluid 4 is the fuel flow Q that circulates in the fuel circuit 1. This also allows the fuel flow Q to be preheated.

[0074] Alternatively, in the example where the conditioning unit 3 is mounted in the intermediate casing CA and the mechanical pump 6 is mounted remotely from the turbomachine M, the cooling circuit 5 passes through the secondary channel V2. Also, the inert fluid 4 can alternatively be cooled, in the heat exchanger 7, by cooling transferred by the secondary airflow circulating in the secondary channel V2 of the turbomachine M. It goes without saying that the heat transfer fluid could be different, for example, a dedicated fluid.

[0075] Preferably, the safety system 2 includes a control valve 8 mounted on the cooling circuit 5 and configured to allow or prohibit the circulation of the inert fluid 4 in the cooling circuit 5. The control valve 8 allows the flow rate of inert fluid 4 circulating in the cooling circuit 5 to be regulated, so as to regulate the cooling of the inert fluid 4 present in the conditioning volume 30, for example according to the phase of flight of the aircraft.

[0076] In one embodiment, with reference to the, the safety system 2 includes a temperature sensor 91A of the inert fluid 4 mounted in the conditioning box 3. The temperature sensor 91A is configured to detect a heating of the inert fluid 4 and, for example, send a control signal to open the control valve 8 when the inert fluid 4 reaches a predetermined limit temperature.

[0077] Alternatively, or in addition, and still with reference to the above, the safety system 2 includes a temperature sensor 91B on one of the pieces of equipment in the section 1P to be protected, in this example the heat exchanger EC. The temperature sensor 91B is configured to detect a rise in temperature in the equipment in section 1P and, for example, send a control signal to open the regulating valve 8 when the equipment reaches a predetermined temperature limit. It goes without saying that the safety system 2 could alternatively include a plurality of temperature sensors 91B mounted on each piece of equipment in the section 1P to be protected. Thanks to the safety system 2, the wall of the equipment in the section 1P to be protected can advantageously be cooled.

[0078] According to one aspect, with reference to the safety system 2, the safety system 2 includes a detection device 92 mounted in the conditioning unit 3 and / or in the cooling circuit 5. In a first embodiment, the detection device 92 is configured to detect the presence of fuel Q in the conditioning unit 3. In this example, the detection device 92 is a fuel Q presence detector, for example, a hydrogen sensor, capable of detecting a fuel Q concentration greater than or equal to a predetermined threshold. The detection device 92 could alternatively be configured to detect the presence of air, for example, an oxygen sensor. In this embodiment, the detection device 92 is a sensor capable of detecting an oxygen concentration greater than or equal to a predetermined threshold.It goes without saying that the security system 2 could alternatively include both a fuel sensor Q and an air sensor.

[0079] In a preferred embodiment, as shown in Figures 4 and 5, the safety system 2 includes a CAL computer configured to control the mechanical pump 6 to increase or decrease the flow of the inert fluid 4 in the cooling circuit 5, in order to cool it more or less.

[0080] Preferably, the CAL computer is also configured to control the regulating valve 8 in order to allow or prohibit the circulation of the inert fluid 4 in the cooling circuit 5, allowing, for example, cooling only when necessary.

[0081] In the embodiment in which the safety system 2 includes a temperature sensor 91, the CAL computer is preferably also configured to detect a temperature of one of the pieces of equipment in the portion 1P to be secured and / or of the inert fluid 4 in the conditioning box 3 which is higher than a predetermined threshold and to control the control valve 8 and / or the mechanical pump 6 according to the temperature detected.

[0082] Similarly, in the embodiment in which the safety system 2 includes a detection device 92, the computer CAL is preferably also configured to: determine that a concentration of fuel Q and / or oxygen in the conditioning chamber 3 is greater than or equal to the predetermined threshold, and issue an alert signal received by the pilot so that the latter can implement countermeasures, for example by commanding a stop of the flow of fuel Q in the portion 1P of the fuel circuit 1.

[0083] With reference to the, according to one aspect, the safety system 2 includes an inert fluid reservoir RI, fluidically connected to the conditioning chamber 3 and / or the cooling circuit 5. The inert fluid reservoir RI is configured to supply the conditioning chamber 3 and / or the cooling circuit 5 with inert fluid 4. In the event of a leak, the injection of inert fluid 4 limits the air concentration in the conditioning chamber 3 to ensure system safety, for example, while waiting for the fuel flow Q to stop in the section 1P to be secured. The safety system 2 also preferably includes an injection valve J configured to allow or prevent the injection of inert fluid 4 from the inert fluid reservoir RI into the conditioning chamber 3.

[0084] In one embodiment, the safety system 2 includes a purge valve and / or a pressure relief valve connecting the conditioning chamber 3 to a fuel evacuation circuit EV Q, shown in Figure 1, and configured to evacuate any potential fuel leak Q and secure the conditioning chamber 3 before it is opened, for example. Such an EV evacuation circuit is known to those skilled in the art and will not be described in further detail in this document.

[0085] The safety system 2 allows both the formation of an inert environment around the portion 1P of the fluid circuit 1 in which the temperature is controlled to avoid, in the event of a leak, any risk of ignition, and the cooling of the equipment in the portion 1P of the fluid circuit.

[0086] A method for using the safety system 2, as described previously, will now be described, with reference to [reference missing]. In this example, the safety system 2 includes a temperature sensor 91B mounted on one of the pieces of equipment in the section 1P to be protected. The control valve 8 of the cooling circuit 5 is initially closed.

[0087] In a preliminary step E0, the temperature sensor 91B measures the equipment temperature and sends it to the CAL control unit, which compares it with a predetermined threshold. When the equipment temperature exceeds the predetermined threshold, the inert fluid 4 is likely to overheat. The CAL control unit then commands the opening of the regulating valve 8.

[0088] In a first step E1, thanks to the mechanical pump 6, the inert fluid 4 from the conditioning box 3 circulates in the cooling circuit 5.

[0089] In a second stage E2, the inert fluid 4 circulating in the cooling circuit 5 passes through the heat exchanger 7 in which it is cooled by means of heat exchanged, in this example, with the fuel flow Q. In parallel, the latter is advantageously preheated by the heat transferred by the inert fluid 4. At the outlet of the heat exchanger 7, the inert fluid 4 then flows towards the inlet 32 ​​of the conditioning box 3 into which it is reintroduced.

[0090] Thanks to the cooling circuit 5, the inert fluid 4 maintains, in the conditioning box 3, a temperature low enough to avoid any risk of overheating while allowing cooling of the equipment in the portion 1P of the fluid circuit 1. In the event of a leak in the portion 1P to be secured, the fuel Q is advantageously not introduced into a heated environment, which allows a high level of safety to be maintained.

Claims

A safety system (2) for a portion (1P) of a fluid circuit (1) in which a fluid that poses a risk to aircraft circulates, the safety system (2) comprising: a sealed conditioning box (3) configured to be mounted around the portion (1P) of the fluid circuit (1), a conditioning volume (30) being defined between the portion (1P) and the conditioning box (3), an inert fluid (4) filling at least part of the conditioning volume (30), the safety system (2) being characterized in that it comprises at least: a cooling circuit (5) for the inert fluid (4) fluidically connected to the conditioning box (3), the cooling circuit (5) being connected, on the one hand, to an outlet (31) of the conditioning box (3) and, on the other hand, to an inlet (32) of the conditioning box (3),in order to form a sealed circulation loop for the inert fluid (4) between the conditioning unit (3) and the cooling circuit (5), a mechanical pump (6) mounted on the cooling circuit (5) and configured to circulate the inert fluid (4) in the cooling circuit (5) and in the conditioning unit (3), and a heat exchanger (7) mounted on the cooling circuit (5) and configured to cool the inert fluid (4) by transferring heat with a heat transfer fluid (HF). Safety system (2) according to claim 1, wherein the heat transfer fluid circulating in the heat exchanger (7) to cool the inert fluid (4) is the fluid at risk. Safety system (2) according to any one of claims 1 to 2, the safety system (2) comprising a temperature sensor (91, 91A, 91B) mounted in the conditioning volume (30) and configured to measure the temperature of the inert fluid in the conditioning box (3). Safety system (2) according to any one of claims 1 to 3, the safety system (2) comprising at least one detection device (92) configured to detect the presence of hazardous fluid or air in the conditioning box (3). Safety system (2) according to any one of claims 1 to 4, the safety system (2) comprising a computer (CAL) configured to control at least the mechanical pump (6), so as to regulate the flow rate of the inert fluid (4) in the cooling circuit (5). Safety system (2) according to any one of claims 1 to 5, the safety system (2) comprising: an inert fluid (IF) reservoir fluidically connected to the conditioning box (3) or the cooling circuit (5), and an injection valve (J) configured to allow or prohibit the injection of inert fluid from the inert fluid (IF) reservoir into the conditioning box (3) or the cooling circuit (5). Aircraft comprising a fluid circuit (1) connecting a cryogenic tank (R) to a combustion chamber (CC) of an aircraft turbomachine (M) in order to supply it with a hazardous fluid, the aircraft comprising at least one safety system (2) according to any one of claims 1 to 6 securing a portion (1P) of the fluid circuit (1). Aircraft according to claim 7, the aircraft comprising a primary vein (V1) and a secondary vein (V2) delimited by an intermediate casing (CA), the conditioning box (3) is located in the intermediate casing (CA). Aircraft according to any one of claims 7 to 8, wherein the mechanical pump (6) is positioned at a distance from the turbomachine (M). Method of using a safety system (2) according to any one of claims 1 to 6, the method of use comprising the steps of: circulating (E1) the inert fluid (4) from the conditioning box (3) in the cooling circuit (5), cooling (E2) the inert fluid (4) in the heat exchanger (7) by heat transfer with a heat transfer fluid before being reintroduced into the conditioning box (3).

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