HIGH-PRESSURE BIPHASIC BUFFER TANK DEVICE

Abstract

High-pressure two-phase buffer tank device High-pressure two-phase buffer tank device 7 for the distribution of combustible gas to at least one gas-consuming device 3, from at least one liquefied gas source 2, the device comprising a tank 27 and a shut-off device 28, the tank 27 comprising a structural wall, thermally insulating and gas-tight, and an inner layer 34 with a lower specific heat capacity than the structural wall and gas-tight.

Description

Title of the invention: HIGH-PRESSURE BIPHASIC BUFFER TANK DEVICE

[0001] The present invention relates to the field of cryogenics.

[0002] Cryogenics offers solutions for maritime, rail and road transport, and stationary gas storage.

[0003] From its beginnings, aeronautics has used high-octane gasoline engines. After 1945, the development of the jet engine and the turbine led to the use of kerosene, which has a higher molecular mass than gasoline, a higher energy density, a higher efficiency, and lower flammability. These fuels are generally stored in tanks located in the wings, in the fuselage-wing junction, or in the tail.

[0004] The trend towards reducing carbon dioxide emissions has led to more fuel-efficient engines. However, the gains in carbon dioxide emissions are diminishing as certain technologies mature, particularly the tip speed of the turbine blades. It has become increasingly desirable to introduce a break in this trend.

[0005] Thus, gas-powered aircraft projects emerged. The combustion of short-chain or non-existent carbon gases, possibly with oxygen, is relatively pollution-free. However, storing H2, O2, Cl, or C2 gases is difficult and subject to leakage risks due to the small size of the gas molecules.

[0006] On the ground, the storage of hydrogen, methane, ethane, ethylene, acetylene, or oxygen is generally carried out in pressure vessels that are too heavy, too bulky, and contain too much pressure potential energy to be carried on board an aircraft, or in welded and / or glued cryogenic tanks. Cryogenic storage is limited to a duration proportional to the volume stored.

[0007] Furthermore, the gas stored in liquid form is not usable by an internal or external combustion engine or a fuel cell. Final consumption requires gas within a temperature and pressure range specified by the manufacturer of the consuming component.

[0008] Cryogenics and aeronautics have very dissimilar requirements, making their compatibility difficult.

[0009] The need arose to condition the gas within an aircraft for its fuel consumption on board. WO2022263307 describes a fuel circuit comprising a buffer tank and a plurality of compression modules to feed the buffer tank, each compression module comprising: an elementary tank of fixed volume, an elementary heat source to increase the temperature of the fuel in the elementary tank isochorically, an inlet valve connecting the elementary tank to an upstream part of the fuel circuit, an outlet valve connecting the elementary tank to the buffer tank and a degassing valve connecting the elementary tank to the cryogenic tank via a return circuit in which a gaseous flow circulates.

[0010] The present invention improves the situation.

[0011] The invention proposes a high-pressure two-phase buffer tank device.

[0012] The invention proposes a high-pressure two-phase buffer tank device forThe system distributes combustible gas to at least one gas-consuming device from at least one liquefied gas source. The device comprises a tank and a closure device. The tank has a structural wall that is thermally insulated and gas-tight, and an inner layer with a lower specific heat capacity than the structural wall. This inner layer, with its low specific heat capacity or thermal inertia, allows for minimal gasification during the filling of the buffer tank. The inner layer reduces thermal conduction. Once the tank is filled, it is sealed. Gasification is then required to supply combustible gas downstream. Gasification is a drawback during the brief filling phase and is desirable during the subsequent phase. The gas can be used as fuel in an internal combustion engine or as a fuel in a fuel cell.After gasification, the term "combustible gas" is used in the following.

[0013] In one embodiment, the structural wall comprises a first structural and thermally insulating layer made of carbon fiber-based composite material, and at least a second gas-tight layer made of polymer, the inner layer having a lower specific heat capacity than both the first and second layers. The first layer is strong and of low mass.

[0014] In one embodiment, the structural wall comprises a third layer that is more thermally insulating than the first and second layers, the inner layer then having a lower specific heat capacity than the third layer. The second and third layers have good insulating properties.

[0015] In one embodiment, the inner layer is made of a metallic material, in particular selected from: aluminium, stainless steel, titanium, Inconel and ferronickel with a Ni content of between 30 and 40%, and has a thickness of between 10 and 300 microns. The inner layer has a low thermal capacity. Thus, during the filling process, the inner layer provides little energy to the liquefied gas when it is at a higher temperature than the liquefied gas.

[0016] In one embodiment, the inner layer is adhered to the structural wall. The inner layer may be thin. The inner layer may have a thickness of 10 to 300 microns. The inner layer may be made of a lightweight and conductive material, for example, aluminum-based.

[0017] In one embodiment, the inner layer is free from the structural wall and gas-porous. Alternatively, the inner layer is free from the structural wall and provided with at least one opening in its upper part. The inner layer delimits a peripheral chamber filled with combustible gas, separated, at least largely, from the contents of the tank and serving as temporary insulation during filling.

[0018] In one embodiment, the inner layer is free from the structural wall, gas-tight, and forms a chamber with the third layer in communication with the outside, said chamber being filled with insulating gas. The inner layer delimits a peripheral chamber filled with gas separate from the contents of the tank and serving as insulation.

[0019] In one embodiment, the inner layer is less insulating than each of the first and second layers and, where applicable, is less insulating than the third layer and has a lower thermal capacity than the third layer. The desired properties of the inner layer are low mass and low thermal capacity.

[0020] In one embodiment, the layers of the structural wall are mutually adherent. The cohesive layers of the wall provide high robustness.

[0021] In one embodiment, the sealing element comprises a plug and at least one through-hole for filling with liquefied gas and for withdrawing combustible gas. Inspection of the device is facilitated.

[0022] In one embodiment, a gas distribution assembly between at least one liquefied gas source and at least one gas-consuming device comprises at least one first on / off valve, controlled at the outlet of each liquefied gas source; a cryogenic distributor connected to each first controlled valve and supplied with liquid; second on / off controlled valves connected in parallel to the cryogenic distributor; buffer tank devices, each supplied with liquid by one of said second controlled valves, and supplying gas; third controlled valves, mounted at the outlet of each buffer tank device, to supply gas; a pressure regulator mounted at the outlet of the third controlled valves; and a manifold supplied by the pressure regulator to supply said manifold to the first controlled valve. minus one consuming organ. The distribution of combustible gas is ensured from liquefied gas stored at cryogenic temperature and low pressure.

[0023] Other features and advantages of the invention will become apparent from an examination of the detailed description below, and the accompanying drawings, in which:

[0024] [Fig-1] schematically illustrates in perspective a distribution set according to one aspect of the invention.

[0025] [Fig.2] schematically illustrates in axial section a device according to one aspect of the invention.

[0026] [Fig.3] is a detail view of the previous one.

[0027] [Fig.4] is a variant of the previous one.

[0028] [Fig. 5] schematically illustrates in axial section a device according to one aspect of the invention.

[0029] [Fig.6] schematically illustrates in axial section a device according to one aspect of the invention.

[0030] [Fig.7] schematically illustrates in axial section a device according to one aspect of the invention has a cooling stage.

[0031] [Fig.8] schematically illustrates in axial section a device according to one aspect of the invention has a filling step.

[0032] [Fig.9] schematically illustrates in axial section a device according to one aspect of the invention has a pressure ramp-up stage.

[0033] [Fig. 10] schematically illustrates in axial section a device according to one aspect of the invention at a withdrawal stage.

[0034] [Fig. 11] schematically illustrates in axial section a device according to one aspect of the invention at a stage of bringing it to ambient pressure.

[0035] The attached drawings may not only serve to complete the invention, but also contribute to its definition, if necessary.

[0036] The gas distribution system is designed to be stationary or transported by a vehicle, particularly an aircraft: airplane, drone, helicopter, etc. The system is supplied with liquid and delivers gas at a chosen pressure. In other words, the fuel or oxidizer is stored at very low temperatures in liquid form in a cryogenic tank. As an embodiment, gaseous hydrogen at 0°C and 1 atmosphere has a density approximately 800 times lower than liquid hydrogen at -253°C, and therefore a volume approximately 800 times greater. A cryogenic tank is not capable of withstanding high pressures, particularly those exceeding 10 bar.

[0037] The stored gas is chosen from hydrogen, methane, ethane, ethylene, acetylene and oxygen.

[0038] The Applicant has identified a need for gas distribution from aeronautical cryogenic tanks, whether they are structurally linked to the aircraft structure, installed in the aircraft or carried by the aircraft.

[0039] From another point of view, aircraft are currently subject to a maximum distance rule from a landing runway, expressed in flight hours according to ETOPS certification. This distance depends on the type of aircraft.

[0040] Wishing to ensure a high level of safety as well as a perception of this safety by users, the Applicant identified the need to fly even in the event of a cryogenic tank failure requiring a release of the contents into the atmosphere.

[0041] The Applicant realized that the buffer tank needs to be thermally insulated from the outside, have very low thermal capacity with respect to the liquefied gas entering the buffer tank for filling, be lightweight, compact, resistant to temperatures from -253°C to +50°C, resistant to temperature variations, resistant to mechanical stresses, including accelerations and vibrations, and resistant to the internal pressure of the combustible gas, which can exceed 500 bar, or even 700 bar. The structure of the buffer tank requires a highly robust construction.

[0042] The filling step is carried out using liquefied gas. The pressure in the buffer tank is lower than the pressure of the source supplying the liquefied gas, whether by pumping or flow under differential pressure. The buffer tank is at ambient temperature, within 10 or 20°C, with ambient temperatures ranging from -56°C at altitude to +50°C at ground level in warm conditions. The enthalpy of vaporization of said liquefied gases is low. Introducing liquefied gas into the buffer tank, which has a temperature 50 to 300°C higher than the liquefied gas, causes extremely rapid gasification at a very early stage. The pressure in the buffer tank increases abruptly. Filling stops.

[0043] The need arose to make filling easier, more repeatable and more reliable. To this end, a buffer tank device and a gas distribution assembly were designed.

[0044] In the embodiment illustrated in [Fig. 1], a gas distribution assembly 1 is supplied by liquefied gas sources 2 to provide gas to one or more consuming devices 3. Here, two consuming devices 3 are shown, for example, two thrusters, an electrical power generator, or an air heater. A flow meter 22 is located at the outlet of each liquefied gas source 2. The gas distribution assembly 1 can be installed on an aircraft.

[0045] The liquefied gas sources 2 here comprise two cryogenic tanks arranged in parallel. Each cryogenic tank is equipped with an outlet pipe 4. The terms upstream and downstream refer to the direction of flow of the fluid, liquid then gas, in normal operation.

[0046] Each cryogenic tank is insulated to contain liquefied gas, for example liquid hydrogen at -253°C. Each cryogenic tank is capable of withstanding a maximum working pressure of around 6 to 10 bar.

[0047] The gas distribution assembly 1 includes a first valve 11 for each cryogenic tank. The first valve 11 is mounted on the outlet line 4. The first valves 11 are actuated with an open position and a closed position. The intermediate positions of the first valves 11 are dynamic in that the first valves 11 move through said intermediate positions. In other words, the first valves 11 are either on or off. The first valves 11 can be arranged immediately downstream of the flow meters 22. Optionally, the flow meters 22 are located downstream of the first valves 11.

[0048] The first valves 11 open into a cryogenic distributor 5. The cryogenic distributor 5 may include a common conduit 6 connecting the outlets of the first valves 11. The distributor is cryogenic in the sense that it sees liquefied gas pass through it.

[0049] The cryogenic distributor 5 comprises a plurality of outlets, here three. Secondary valves 12 are mounted on each of these outlets. The secondary valves 12 are actuated with an open position and a closed position. The intermediate positions of the secondary valves 12 are dynamic in that the secondary valves 12 move through these intermediate positions. In other words, the secondary valves 12 are either on or off. There are three secondary valves 12 in this instance.

[0050] Unlike the space domain where a cryogenic valve is used once and does not need to be closed, the first valves 11 and the second valves 12 are resealable, for example solenoid valves.

[0051] Downstream of each second valve 12, a buffer tank device 7 is mounted. Three buffer tanks 7 are provided in this embodiment. Each buffer tank device 7 also serves as a gasifier. Insulation can be avoided. Each buffer tank device 7 receives liquid and supplies gas downstream. A pressure rise or gasification stage occurs in each buffer tank device 7 between filling and emptying. Each buffer tank device 7 is capable of withstanding a maximum operating pressure of approximately 300 to 1000 bar. Each buffer tank device 7 is designed to operate in a temperature range from -253°C to +60°C. The buffer tanks 7 are two-phase in some of the operating stages and single-phase gaseous in others. the other operating steps. Each buffer tank device 7 can be equipped with an external heating element 8 in the mode of [Fig.1].

[0052] Downstream of each buffer tank device 7, a third valve 13 is installed to supply gas, and a pressure regulator 9 is installed downstream of the third valve 13. The pressure regulator 9 reduces the pressure to supply gas at a consumption pressure set by the manufacturer of the consuming device 3. The pressure regulator 9 is active when the pressure in the buffer tank device 7 is higher than the consumption pressure and inactive otherwise. The consumption pressure is lower than the maximum pressure of the buffer tank device 7. The consumption pressure is independent of the maximum pressure of the cryogenic tanks. The third valves 13 are on / off.

[0053] Downstream of each regulator 9, a fourth controlled valve 14 may be provided. The fourth valves 14 are on / off.

[0054] The fourth valves 14 or the pressure regulators 9, depending on the option chosen, open into a manifold 10. The manifold 10 may include a pipe connecting the outlets of the fourth valves 14 or the pressure regulators 9. Gas flows through the manifold 10. The manifold 10 is connected downstream to supply lines 23 leading to the consuming devices 3. Generally, a supply line 23 is provided for each consuming device 3. Each supply line 23 may be equipped with a pilot-operated supply valve 24. The supply valve 24 is variable flow.

[0055] The gas distribution device 1 may include at least one compressor 20 connected to the manifold 10. Generally, two compressors 20 are provided in parallel for redundancy. The compressor 20 is electric. The compressor 20 may be equipped with a pilot-operated upstream valve. The compressor 20 delivers gas into the manifold 10. In particular, the manifold 10 consists of a single pipe in the case of a single consuming device 3.

[0056] Downstream of each buffer tank device 7, a fifth valve 15 is installed to supply gas, and a second manifold is installed downstream of the fifth valves 15. The second manifold is connected to the compressor 20. The fifth valves 15 allow the buffer tanks 7 and the compressor 20 to be isolated. The fifth valves 15 are controlled. The fifth valves 15 are on / off.

[0057] The compressor 20 increases the pressure to supply gas at a pressure equal to a consumption pressure set by the manufacturer of the consuming component 3. The consumption pressure is lower than the maximum pressure in the buffer tank device 7. The compressor 20 allows gas to be drawn from a buffer tank device 7 whose pressure is lower than the consumption pressure to supply the manifold 10 and the consuming components 3. A more complete emptying of the buffer tank device 7 increases the autonomy supplied by the gas. contained in a buffer tank device 7 or to reduce the volume of the buffer tank device 7.

[0058] Draining the buffer tank device 7 sufficiently to reduce its internal pressure to a value lower than the pressure in one of the cryogenic tanks allows, during the subsequent refilling, the transfer of liquid from the cryogenic tank to the buffer tank device 7 by pressure difference. Thus, the liquid from the cryogenic tank is drawn into the buffer tank device 7 until pressure equilibrium is reached. A cryogenic pump is therefore unnecessary, resulting in a saving in mass and energy consumption.

[0059] The gas distribution device 1 offers a combination of individual states for each cryogenic tank, each buffer tank device 7, and each consuming unit 3. Several consuming units 3 can be active simultaneously. In normal mode, one cryogenic tank is being emptied while the others are inactive and therefore closed. However, in certain situations, for example, to reduce the pressure in several cryogenic tanks, a special mode can be provided in which several cryogenic tanks are being emptied. The buffer tanks 7 have a filling mode, a gasification mode, a gas storage mode, and an emptying mode.

[0060] When one of the cryogenic tanks is being emptied, the corresponding first valve 11 is opened and the other first valves 11 are closed. When one of the consuming devices 3 is being supplied, the corresponding supply valve 24 is opened.

[0061] When one of the buffer tanks 7 is in filling mode, the second valve 12 connected to said buffer tank device 7 is open, and at least one of the first valves 11 is open. The other second valves 12 are closed, except in the case where simultaneous filling of two buffer tanks 7 is performed. The third valve 13 connected to said buffer tank device 7 is closed. The fifth valve connected to said buffer tank device 7 is closed.

[0062] When one of the buffer tanks 7 is in gasification mode, the second valve 12 connected to said buffer tank device 7, the third valve 13 connected to said buffer tank device 7, and the fifth valve 15 connected to said buffer tank device 7 are closed. The gasification mode is of short duration, particularly in the case of a warm ambient atmosphere and / or heating of the buffer tank device 7.

[0063] When one of the buffer tanks 7 is in drain mode, the second valve 12 connected to said buffer tank device 7 is closed. In the first part of the drain, the pressure in the buffer tank device 7 is higher than the consumption pressure. The third valve 13 connected to said buffer tank device Valve 7 is open, the corresponding fourth valve 14 is open, and the fifth valve connected to said buffer tank device 7 is closed. The gas undergoes a pressure reduction in the pressure regulator 9 and is supplied to the manifold 10 at the consumption pressure. The gas is then consumed by the consuming device(s) 3.

[0064] At any given time, among three buffer tanks 7, one is in filling mode, another in gasification and then storage mode, and the third in emptying mode. Since the modes have different durations, it is also possible to find two buffer tanks 7 in filling mode and the third in emptying mode, or vice versa. It is also possible to find two buffer tanks 7 in storage mode and the third in emptying mode, or vice versa.

[0065] In the embodiment, a flow meter 22 is disposed at the outlet of each liquefied gas source 2. The flow meters 22 make it possible to know with sufficient precision the quantity of liquid supplied to such buffer tank device 7.

[0066] In one embodiment, the gas distribution device 1 comprises a control unit 25 receiving an external setpoint, for example from the consuming devices 3 or from a central control unit, and liquid flow data from the flow meters 22. The control unit 25 generates and sends setpoints to the first, second, third, fourth, and fifth controlled valves and to the controlled supply valves 24. The setpoints can be "open" or "closed". The control unit 25 manages this combination of individual states.

[0067] Alternatively, the first valves 11 can be replaced by at least one multiport valve having several inlets and one outlet. In this case, it is advantageous to provide a multiport valve with mixed positions, in particular at least one position for simultaneously draining two or more sources of liquefied gas 2 in order to reduce the pressure while preventing loss to the atmosphere.

[0068] Alternatively, the second valves 12 can be replaced by at least one multi-way valve having one inlet and several outlets, one per buffer tank device 7. Said multi-way valve forms a distributor.

[0069] Alternatively, the regulators 9 are replaced by a single regulator 9, with the third valves 13 opening into this single regulator 9. In this case, the third valves 13 can be replaced by at least one multiport valve having several inlets and one outlet to the regulator. The fourth valves 14 are then replaced by a single fourth valve 14, which may be non-piloted.

[0070] Alternatively, the fifth valves 15 can be replaced by at least one multi-way valve having several inlets, one per buffer tank device 7, and an outlet to the compressor 20 or compressors 20. Said multi-way valve forms a manifold 10.

[0071] The buffer tank device 7 is shown in more detail in figures 2 to 11. The buffer tank device 7 is biphasic in that it is designed to house a predominantly liquid content at cryogenic temperatures and a gaseous content at high pressure. The predominantly liquid content comprises 80 to 90% liquid and a gaseous portion. The gaseous content can reach a high pressure of several hundred bars. The buffer tank device 7 can be carried by an aircraft, either internally, for example in the fuselage or in a wing if the wing is sufficiently thick, or externally, for example under a wing.

[0072] In the embodiment shown in Figures 2 and 3, the buffer tank device 7 comprises a vessel 27 and a sealing element 28. The vessel 27 is rigid. The vessel 27 is thermally insulating. The vessel 27 is gas-tight. The vessel 27 is resistant to cryogenic temperatures within said vessel 27. The vessel 27 is resistant to rapid temperature changes. In the embodiments shown, the vessel 27 is multilayered.

[0073] An opening 29 is provided in the tank 27. In the opening 29 is disposed the sealing member 28 ensuring the retention of the contents, and allowing filling by the contents and emptying of the contents towards downstream components.

[0074] The tank 27 comprises a wall and an inner layer 34. The wall is structural, thermally insulating, and gas-tight. The wall comprises, from the outside in, a first layer 31, a second layer 32, and a third layer 33, see [Fig. 3]. Alternatively, the wall comprises, from the outside in, a first layer 31 and a second layer 32, see [Fig. 4].

[0075] The first layer 31 is structural in that it gives the tank 27 its shape, rigidity, and an external mechanical connection to a tank support 27. The first layer 31 may be thermally insulating. The inner layer 34 has a lower specific heat capacity than the third layer 33. The first layer 31, second layer 32, and third layer 33 form a mechanical, thermal, and sealing assembly. The inner layer 34 is internal.

[0076] The tank 27 has a shape of revolution comprising a cylindrical central portion, a circular, for example hemispherical, bottom, and a circular, for example hemispherical, top. The top is surmounted by a neck 30 which defines a bore. The neck 30 may have a thickness greater than the thickness of the central portion and the bottom to withstand the mechanical forces transmitted by the sealing member 28. The neck 30 is formed by at least the first layer 31, optionally the second layer 32, and optionally the third layer 33.

[0077] The first layer 31 is made of composite materials. The first layer 31 comprises fibers, for example carbon or aramid fibers, and a matrix. The first Layer 31 is resistant to cryogenic temperatures and rapid temperature changes. The first layer 31 has a first thickness. This first thickness is sized according to the volume and shape of the tank and the external and internal pressures. The first layer 31 is continuous, except for the opening 29. The first layer 31 extends, in this case, over the height of the tank 27.

[0078] The second layer 32 is gas-tight. The second layer 32 provides the tank 27 with its airtightness, where applicable, to small molecules such as H2. The airtightness of the second layer 32 is better than 10⁻¹⁰ Pa·mVs to helium. The second layer 32 has a second thickness. The second thickness is less than the first thickness. The second layer 32 is made of polymers. The second thickness can be between 0.1 and 10 mm. The first layer 31 and the second layer 32 are preferably mutually bonded. The second layer 32 is continuous, except for the opening 29. The second layer 32 extends, here, over the height of the tank 27 minus the neck 30.

[0079] The third layer 33 is more thermally insulating than the first and second layers. The third layer 33 provides the tank 27 with its thermal insulation. The third layer 33 has a thermal conductivity of less than 100 mW.m*.K'. The third layer 33 can be made of polymer, for example, fiber-reinforced PU foam. Alternatively, the third layer 33 can be made of mineral wool. The third layer 33 has a third thickness. The third thickness is greater than the first thickness. The third thickness can be between 1 and 100 mm. The second layer 32 and the third layer 33 are preferably mutually bonded. The third layer 33 is continuous, except for the opening 29. The third layer 33 extends, in this case, over the height of the tank 27 minus the neck 30.

[0080] The inner layer 34 has a lower thermal capacity than each of the first, second, and third layers. The inner layer 34 is impermeable to liquefied gas. Gas impermeability is optional. The inner layer 34 gives the tank 27 reduced gas release during filling. The inner layer 34 is less insulating than each of the first, second, and third layers.

[0081] The inner layer 34 is made of metal, for example aluminum or aluminum alloy. More generally, the inner layer 34 is metallic. The metal of the inner layer 34 can be chosen from: aluminum, stainless steel, titanium, Inconel, and ferronickel. In the case of ferronickel, the Ni content is between 30 and 40%. Thus, a material with low heat capacity, resistance to cryogenic temperatures, and low surface mass is used for the intended application.

[0082] The inner layer 34 has a fourth thickness. The fourth thickness is less than the first, second, and third thicknesses. The fourth thickness can be between 10 and 300 microns.

[0083] In the embodiment of [Fig. 3], the inner layer 34 adheres to the wall. The inner layer 34 is applied to the third layer 33, for example, over its entire inner surface. The inner layer 34 can then have a small thickness, in particular between 10 and 300 microns.

[0084] In the embodiment of [Fig. 4], the inner layer 34 is free with respect to the wall. The inner layer 34 may be porous to combustible gas. The inner layer 34 may be impermeable to liquids, in particular to liquefied gas. The second layer 32 and the inner layer 34 can then form a chamber 35. The chamber 35 can have a variable volume. The inner layer 34 can then have a thickness between 0.01 and 1 mm.

[0085] Alternatively, see [Fig. 6], the inner layer 34 may be provided with at least one opening 36 in its upper part. This opening 36 allows gas to pass between the inner layer 34 and the wall, i.e., into the chamber 35. This opening 36 may be located in a sufficiently high position to be situated in the gas headspace at the end of the filling process and after filling. The gas headspace is the portion of the tank filled with gas above the liquid phase. The gas headspace is minimal at the end of the filling process and after filling.

[0086] In one embodiment, the tank 27 includes an interlayer between the third layer 33 and the inner layer 34. The interlayer forms additional insulation. The interlayer comprises a porous material capable of absorbing or adsorbing the combustible gas.

[0087] The tank 27 includes an insert 37. The insert 37 is leak-proof. The insert 37 is pressure-resistant. The insert 37 is capable of transmitting axial forces to the tank 27 during high-pressure phases.

[0088] The insert 37 has a generally annular shape. The insert 37 may be metallic. The insert 37 comprises a lower portion 38 widening downwards and a cylindrical upper portion 39. The lower portion 38 is in contact with an internal surface of the top of the tank 27. The upper portion 39 is in contact with a bore in the neck 30. The height of the insert 37 is greater than the height of the neck 30 and less than the sum of the heights of the neck 30 and the top of the tank 27. The insert 37 is held in position by conformity of shape. The insert 37 may be fixed to the neck 30 and the top of the tank 27 by bonding. The insert 37 is made in one piece. The insert 37 has a central opening 29.

[0089] The opening 29 is axial. The opening 29 has a grooved or helical peripheral surface. Here, the groove or helix is ​​chevron-shaped, as seen in axial section. to lengthen the thermal conduction path. The opening 29 can be lined with a coating of a material different from the material of the insert 37.

[0090] The sealing element 28 is leak-proof. The sealing element 28 is pressure-resistant. The sealing element 28 is removable. The sealing element 28 comprises a body forming a plug. The body comprises a lower portion 40 housed within the opening 29 and an upper portion 41 extending from the opening 29. The upper portion 41 is in contact with an upper surface of the neck 30.

[0091] The sealing member 28 includes a filling line 42 passing through the body between the outside and the inside of the tank 27.

[0092] The shut-off device 28 includes a draw line 43 passing through the body between the outside and the inside of the tank 27. The draw line 43 can serve as a vent. The draw line 43 is designed to obtain gas and supply it downstream. In the body, the draw line 43 and the filling line 42 are parallel and separated from each other.

[0093] In the embodiment shown in [Fig. 2], the shut-off member 28 includes at least one additional passage. An internal heating element 44 is mounted in this additional passage. Here, the heating element 44 passes through two additional passages. The heating element 44 serves to accelerate gasification after filling and when the second and third valves are closed, or at least the second valve 12 is closed. The heating element 44 extends into a high area of ​​the tank, for example, into the top of the tank and, if necessary, into the central cylindrical section. The heating element 44 may be located above the maximum level of liquefied gas. The heating element 44 extends into the gas headspace.

[0094] The heating element 44 can be electric, an additional through-hole being sufficient.

[0095] The heating element 44 can be a heat exchanger with a heat transfer fluid passing through a tube. The tube is spiral-shaped. The heating element 44 can have from two to five turns. The heat transfer fluid can be a gas, fuel, or combustion fluid. Two additional passages are provided for the inlet of the hot heat transfer fluid and the outlet of the cooled heat transfer fluid. Alternatively, the inlet and outlet share a single additional passage.

[0096] In the embodiment of [Fig.1], the heating element 8 is mounted outside the tank 27. In the embodiments shown in Figures 5 and 6, the heating element is absent or external and not shown.

[0097] In the embodiment of [Fig. 5], the aforementioned inner layer 34 is replaced by an outer layer 45. The outer layer 45 forms an insulating jacket surrounding the first layer 31. The outer layer 45 surrounds the part upper 41 of the body of the obturator 28. The outer layer 45 can be made of a cellular material, for example EPS. The outer layer 45 can be made of at least two removable parts.

[0098] In the embodiment of [Fig. 6], the inner layer 34 is free from the third layer 33 and gas-tight. The inner layer 34 forms, with the wall, a chamber 35 in communication with the outside. This communication with the outside serves for filling and refilling the chamber 35. Said chamber 35 is filled with an insulating gas, for example Ar. After filling, said chamber 35 is sealed. The heating of the liquefied gas during the filling of the tank is therefore very low. The outer layer 45 improves the insulation. The outer layer 45 forms an insulating jacket surrounding the first layer 31. The outer layer 45 surrounds the upper part 41 of the body of the sealing element 28.

[0099] Figures 7 to 11 show the implementation steps of the buffer tank device 7. The buffer tank device 7 is in its operational state, with the sealing element 28 firmly fixed to the tank 27. Starting from an empty tank at ambient temperature, generally between -56°C and +50°C, a first cooling step is carried out. The first step is performed by introducing a liquefied gas into the tank 27 and degassing it. The liquefied gas can be the same as in the following steps or a neutral gas, for example, nitrogen. The withdrawal line 43 is opened while the filling line 42 supplies the liquefied gas. The release of the liquefied gas causes very rapid evaporation and cooling of the interior of the tank 27, starting with the inner layer 34, then the third layer 33. The duration of the first step is as short as possible. The invention makes it possible to reduce the duration of the first step.The pressure at the end of the first stage is equal to the ambient pressure, for example around the aircraft.

[0100] Once the interior of the tank 27 has been brought to a chosen temperature, the second filling stage with liquefied gas precursor to the fuel gas begins. Filling is carried out via the filling line 42. The withdrawal line 43 is opened and then closed during the second stage or closed from the beginning of the second stage. A gas headspace of a few percent of the volume of the tank 27 is left. The filling line 42 is closed at the end of the second stage. The duration of the second stage is kept as short as possible. The brevity of the second stage is less critical than the brevity of the first stage. The invention makes it possible to reduce the duration of the second stage. The pressure increases during the second stage. The pressure at the end of the second stage is equal to or less than the pressure of the cryogenic tank supplying the liquefied gas. The pressure at the end of the second stage is between 6 and 10 bar.The presence of a cryogenic pump is avoided.

[0101] Once the tank 27 is filled with the desired quantity of liquefied gas, the third pressurization stage begins. Pressurization can be assisted by the heating element 44. The heating element 44 is activated for a sufficient duration to allow the pressure in the tank 27 to reach the minimum pressure required to supply combustible gas downstream. The heating element 44 is inactive during the other stages. The withdrawal line 43 is closed and the filling line 42 is closed during the third stage. The duration of the third stage is as short as possible—to make the buffer tank active in supplying combustible gas. The brevity of the third stage is less critical than the brevity of the first stage. The pressure at the end of the third stage is higher than the pressure of the cryogenic tank supplying the liquefied gas. The pressure at the end of the third stage is between 100 and 700 bar.The pressurization process occurs simultaneously with a temperature increase.

[0102] The filling line 42 is closed. Once pressurization is achieved, the fourth withdrawal stage begins. The withdrawal line 43 is opened. The duration of the fourth stage varies depending on the downstream fuel gas demand. The pressure at the end of the fourth stage depends on the presence or absence of a compressor 20 downstream of the buffer tank device 7. If a compressor 20 is provided (see [Fig. 1]), the pressure at the end of the fourth stage depends on the characteristics of the compressor 20 and may be lower than the ambient pressure. In the absence of a compressor 20, the pressure at the end of the fourth stage depends on the characteristics of the consuming device 3. The pressure at the end of the fourth stage can be from 1 to 50 bar.

[0103] Once pressurization is achieved, the fourth withdrawal stage begins. The withdrawal line 43 is opened. The filling line 42 is closed. The duration of the fourth stage varies depending on the downstream fuel gas demand. The temperature rises gradually according to the withdrawal flow rate. If the withdrawal flow rate is high, the temperature rise is slow. If the withdrawal flow rate is low, the temperature rise is rapid. The pressure at the end of the fourth stage depends on the presence or absence of a compressor 20 downstream of the buffer tank device 7. If a compressor 20 is provided, see [Fig. 1], the pressure at the end of the fourth stage depends on the compressor characteristics and may be lower than the ambient pressure. In the absence of a compressor, the pressure at the end of the fourth stage depends on the characteristics of the consuming device 3. The pressure at the end of the fourth stage can be from 1 to 50 bar.The pressure at the end of the fourth stage is at a level where the withdrawal of combustible gas ceases.

[0104] Once the pressure at the end of the fourth step is reached, the fifth step, which restores pressure to ambient, begins. The fifth step is optional. If the pressure at the end of the fourth step is higher than the ambient pressure, degassing The fifth stage is carried out via the open withdrawal line 43. The filling line 42 is closed. The duration of the fifth stage is short. The temperature in the tank 27 decreases. The pressure at the end of the fifth stage is equal to the ambient pressure, for example, 1013 hPa at ground level or 265 hPa at an altitude of 10,000 m. The fifth stage is performed in the absence of a compressor or if the compressor 20 does not provide sufficient flow or efficiency to supply the required flow rate of combustible gas towards the end of the fourth stage.

[0105] After the fifth step, either the tank 27 is cold enough and we proceed directly to the second step, or we proceed to the first step.

[0106] In one embodiment, the high-pressure, two-phase aeronautical buffer tank device 7 is carried on board an aircraft for the distribution of combustible gas to at least one gas-consuming component 3 of said aircraft, from at least one liquefied gas source 2 of said aircraft. The buffer tank device 7 comprises a tank 27 and a shut-off device 28. The tank 27 comprises a set of structural layers that are thermally insulating and gas-tight, and an inner layer that is gas-tight and has a lower thermal capacity than each of the layers in the set of layers. The inner layer may be thermally conductive.

[0107] Thanks to the high-pressure two-phase buffer tank device, the inner layer with low thermal capacity reduces the vaporization of the liquefied gas and therefore the pressure rise during filling. Losses are reduced. The filling time is decreased. The probability of incomplete filling is reduced. The ratio of active service time, i.e., the duration of the fourth stage, to the duration of a buffer tank cycle is improved.

Claims

Demands

1. High-pressure two-phase buffer tank device (7) for distributing combustible gas to at least one gas-consuming device (3), from at least one liquefied gas source (2), the device comprising a tank (27) and a shut-off device (28), the tank (27) comprising a structural wall, thermally insulating and gas-tight, and an inner layer (34) having a lower specific heat capacity than the structural wall and being gas-tight, the structural wall comprising a first structural and thermally insulating layer (31) made of carbon fiber-based composite material, at least a second gas-tight layer (32) made of polymer, the inner layer (34) having a lower specific heat capacity than the first layer (31) and the second layer (32), the layers of the structural wall being mutually bonded.

2. Device according to claim 1, wherein the structural wall comprises a third layer (33) which is more thermally insulating than the first and second layers, the inner layer (34) in this case having a lower specific heat capacity than the third layer.

3. Device according to any one of the preceding claims, wherein the inner layer (34) is made of a metallic material, in particular selected from: aluminium, stainless steel, titanium, inconel and ferronickel with a Ni content of between 30 and 40%, and has a thickness of between 10 and 300 microns.

4. Device according to any one of the preceding claims, wherein the inner layer (34) is adherent to the structural wall.

5. Device according to any one of claims 1 to 4, wherein the inner layer (34) is free with respect to the structural wall and gas porous and / or provided with at least one light (36) in its upper part.

6. Device according to any one of claims 1 to 4, wherein the inner layer (34) is free with respect to the structural wall, gas-tight and forming with the third layer (33) a chamber (35) in communication with the outside, said chamber (35) being filled with insulating gas.

7. Device according to any one of the preceding claims, wherein the inner layer (34) is less thermally insulating than each of the first and second layers and, where applicable, is less thermally insulating than the third layer and has a lower specific heat capacity than the third layer.

8. Device according to any one of the preceding claims, wherein the sealing member (28) comprises a plug and at least one through-hole for filling with liquefied gas and for withdrawing combustible gas.

9. A gas distribution assembly (1) between at least one liquefied gas source (2) and at least one gas-consuming device (3), comprising at least one first on / off valve (11) controlled at the outlet of each liquefied gas source (2), a cryogenic distributor (5) connected to each first controlled valve (11) and supplied with liquid, second on / off controlled valves (12) connected in parallel to the cryogenic distributor (5), buffer tank devices (7) according to any one of the preceding claims, each supplied with liquid by one of said second controlled valves (12) and supplying gas, third controlled valves (13) mounted at the outlet of each buffer tank device (7) for supplying gas, a pressure regulator (9) mounted at the outlet of the third controlled valves (13), and a manifold (10) supplied by the pressure regulator (9) for supplying said at least one consumer organ (3).

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