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 TWO-PHASIC 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] Since 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 weight 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 connection, 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 speed at the tip of the blades. It has become increasingly desirable to introduce a breakthrough.

[0005] Thus, gas aircraft projects have emerged. The combustion of gases with a short or non-existent carbon chain, possibly with oxygen, is little or non-polluting. On the other hand, the storage of H2, 02 or Cl or C2 gases due to the small size of the gas molecule is difficult and subject to risks of leaks.

[0006] On the ground, the storage of hydrogen, methane, ethane, ethylene, acetylene or oxygen is generally carried out in pressurized envelopes 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 limited duration proportional to the volume stored.

[0007] Furthermore, gas stored in the liquid state cannot be used by an internal or external combustion engine or a fuel cell. Final consumption requires gas in a temperature range and a pressure range specified by the manufacturer of the consumer unit.

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

[0009] The need has arisen to condition the gas within an aircraft for its consumption on board. WO2022263307 describes a fuel circuit comprising a buffer tank and a plurality of compression modules for supplying the buffer tank, each compression module comprising: an elementary tank of fixed volume, an elementary heat source for increasing the temperature of the fuel in the elementary tank in an isochoric manner, 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 by a return circuit in which a gas flow circulates.

[0010] The present invention improves the situation.

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

[0012] The invention provides a high pressure two-phase buffer tank device for the distribution of combustible gas to at least one gas-consuming member, from at least one source of liquefied gas. The device comprises a tank and a closure member, the tank comprising a structural wall, thermally insulating and gas-tight, and an inner layer with a specific heat capacity lower than the structural wall and tight to liquefied gas. The inner layer with low specific heat capacity or thermal inertia allows for low gasification during the filling time of the buffer tank. The inner layer reduces thermal conduction. Once filling is complete, the buffer tank is closed. Gasification is then sought to be able to supply combustible gas downstream. Gasification is a disadvantage during the brief filling phase and is desired during the following phase. The gas can be used as fuel in a combustion engine or as fuel in a fuel cell.After gasification, the terms "fuel gas" are used in the following.

[0013] In one embodiment, the structural wall comprises a first structural and thermally insulating layer, made of a carbon fiber composite material, and at least one second gas-tight layer made of a polymer, the inner layer having a lower specific heat capacity than the first layer and the second layer. 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 layer and the third layer have good insulating properties.

[0015] In one embodiment, the inner layer is made of a metallic material, notably chosen from: aluminum, 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 period, 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 adherent to the structural wall. The inner layer may have a small thickness. 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 based on aluminum.

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

[0018] In one embodiment, the inner layer is free relative to the structural wall, gas-tight and forming with the third layer a chamber in communication with the exterior, said chamber being filled with insulating gas. The inner layer delimits a peripheral chamber filled with gas separated 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, if 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 strength.

[0021] In one embodiment, the closure member comprises a plug and at least one passage 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 source of liquefied gas and at least one gas consuming member comprises at least one first, all-or-nothing, controlled valve at the outlet of each source of liquefied gas; a cryogenic distributor connected to each first controlled valve, and supplied with liquid; second, all-or-nothing, controlled valves, connected to the cryogenic distributor, in parallel; buffer tank devices, supplied with liquid, each 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 reducer mounted at the outlet of the third controlled valves; and a manifold supplied by the pressure reducer to supply said at least one less one consumer organ. The distribution of combustible gas is ensured from liquefied gas stored at cryogenic temperature and low pressure.

[0023] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

[0024] [Fig-1] schematically illustrates in perspective a distribution assembly 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 to a cooling step.

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

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

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

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

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

[0036] The gas distribution assembly is designed to be stationary or carried by a vehicle, in particular an aircraft: airplane, drone, helicopter, etc. The assembly is supplied with liquid and provides gas under a chosen pressure. In other words, the fuel or oxidant is stored at very low temperature 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, therefore a volume approximately 800 times higher. A cryogenic tank is unable to withstand high pressures, in particular greater than 10 bars.

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

[0038] The Applicant has identified a need for distribution of gas from reservoirs aeronautical cryogenics whether 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 cryogenic tank damage requiring release of the contents into the atmosphere.

[0041] The Applicant has realized that the buffer tank needs to be thermally insulated from the outside, with a very low thermal capacity with respect to the liquefied gas entering when filling the buffer tank, of low mass, of small size, resistant to temperatures from -253° to +50°, resistant to temperature variations, resistant to mechanical stresses, in particular accelerations and vibrations and resistant to the internal pressure of the combustible gas which may exceed 500 bars, or even 700 bars. The structure of the buffer tank requires a highly robust construction.

[0042] The filling step is carried out by liquefied gas. The pressure in the buffer tank is lower than the pressure of the source supplying the liquefied gas, by pumping or flow under pressure differential. The buffer tank is at ambient temperature to within 10 or 20°, the ambient temperature being between -56° at altitude and +50° on the ground in hot conditions. However, the enthalpy of vaporization of said liquefied gases is low. The introduction of liquefied gas into the buffer tank, which has a temperature 50 to 300° 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 supply gas to one or more consuming members 3. Here, two consuming members 3 have been shown, for example two thrusters, an electric power generator or an air heater. A flow meter 22 is arranged at the outlet of each liquefied gas source 2. The gas distribution assembly 1 can be carried on board an aircraft.

[0045] The liquefied gas sources 2 comprise, here, two cryogenic tanks arranged in parallel. Each cryogenic tank is provided 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 operating pressure of the order of 6 to 10 bars.

[0047] The gas distribution assembly 1 comprises a first valve 11 for each cryogenic tank. The first valve 11 is mounted on the outlet pipe 4. The first valves 11 are controlled with an open position and a closed position. The intermediate positions of the first valves 11 are dynamic in that the first valves 11 are in motion while passing through said intermediate positions. In other words, the first valves 11 are on / off. The first valves 11 may be arranged immediately downstream of the flow meters 22. Optionally, the flow meters 22 are downstream of the first valves 11.

[0048] The first valves 11 open into a cryogenic distributor 5. The cryogenic distributor 5 may comprise a common pipe 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. On each of said outlets are mounted second valves 12. The second valves 12 are controlled with an open position and a closed position. The intermediate positions of the second valves 12 are dynamic in the sense that the second valves 12 are in movement while passing into said intermediate positions. In other words, the second valves 12 are all or nothing. The second valves 12 are here three in number.

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

[0051] Downstream of each second valve 12 is mounted a buffer tank device 7. 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 increase or gasification step 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 the order of 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 part of the operating stages and single-phase gas in the other operating stages.Each buffer tank device 7 can be equipped with a heating member 8, external in the mode of [Fig.l].

[0052] Downstream of each buffer tank device 7 is installed a third valve 13 for supplying gas and a pressure reducer 9 downstream of the third valve 13. The pressure reducer 9 limits the pressure to supply gas at a consumption pressure set by the manufacturer of the consumer member 3. The pressure reducer 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 can be provided. The fourth valves 14 are all or nothing.

[0054] The fourth valves 14 or the regulators 9, depending on the option chosen, open into a manifold 10. The manifold 10 may comprise a pipe connecting the outlets of the fourth valves 14 or the regulators 9. The manifold 10 sees gas pass through. The manifold 10 is connected downstream to supply pipes 23 to the consumer members 3. In general, a supply pipe 23 is provided for each consumer member 3. Each supply pipe 23 may be equipped with a controlled supply valve 24. The supply valve 24 has a variable flow rate.

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

[0056] Downstream of each buffer tank device 7 is installed a fifth valve 15 to supply gas and a second manifold downstream of the fifth valves 15. The second manifold is connected to the compressor 20. The fifth valves 15 make it possible to isolate the buffer tanks 7 and the compressor 20. The fifth valves 15 are controlled. The fifth valves 15 are all or nothing.

[0057] The compressor 20 increases the pressure to supply gas at a pressure equal to a consumption pressure set by the manufacturer of the consumer member 3. The consumption pressure is lower than the maximum pressure in the buffer tank device 7. The compressor 20 makes it possible to take gas from a buffer tank device 7 whose pressure is lower than the consumption pressure to supply the collector 10 and the consumer members 3. A more complete emptying of the buffer tank device 7 makes it possible to increase the autonomy provided by the gas contained in a buffer tank device 7 or to reduce the volume of the buffer tank device 7.

[0058] Emptying the buffer tank device 7 sufficient to bring the internal pressure of the buffer tank device 7 to a value lower than the pressure in one of the cryogenic tanks makes it possible, during filling following emptying, to transfer the liquid from the cryogenic tank to the buffer tank device 7 by pressure difference. Thus, the liquid from the cryogenic tank is sucked by the buffer tank device 7 until pressure equilibrium is reached. A cryogenic pump can be dispensed with, resulting in a saving in mass and energy consumption.

[0059] The gas distribution device 1 offers a combination of individual states of each cryogenic tank, each buffer tank device 7 and each consumer member 3. Several consumer members 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 particular 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 open and the other first valves 11 are closed. When one of the consumer members 3 is being supplied, the corresponding supply valve 24 is open.

[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, in particular 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 emptying mode, the second valve 12 connected to said buffer tank device 7 is closed. In the first part of emptying, the pressure in the buffer tank device 7 is higher than the consumption pressure. The third valve 13 connected to said buffer tank device 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 reduction of pressure in the regulator 9 and is supplied to the manifold 10 at the consumption pressure. The gas is then consumed by the consumer organ(s) 3.

[0064] At a given moment, among three buffer tanks 7, one is in filling mode, another in gasification 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 arranged at the outlet of each source of liquefied gas 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 instruction, for example from the consumer members 3 or from a central control unit, and liquid flow rate data from the flow meters 22. The control unit 25 generates and sends instructions to said first, second, third, fourth and fifth controlled valves and to the controlled supply valves 24. The instructions can be “open” or “closed”. The control unit 25 manages said combination of individual states.

[0067] Alternatively, the first valves 11 may be replaced by at least one multi-way valve having several inlets and one outlet. In this case, it is advantageous to provide a multi-way valve with mixed positions, in particular at least one position for simultaneous emptying of two or more sources of liquefied gas 2 to reduce the pressure while avoiding loss into the atmosphere.

[0068] Alternatively, the second valves 12 can be replaced by at least one multi-way valve having an 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, the third valves 13 opening into the single regulator 9. In this case, the third valves 13 can be replaced by at least one multi-way valve having several inlets and one outlet to the regulator. The fourth valves 14 are then replaced by a single fourth valve 14, possibly not controlled.

[0070] Alternatively, the fifth valves 15 may 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 provided to accommodate a essentially liquid content at cryogenic temperature and a gaseous content at high pressure. The essentially liquid content comprises 80 to 90% liquid and a gaseous atmosphere. The gaseous content can reach a high pressure of several hundred bars. The buffer tank device 7 can be carried by an aircraft, internally, for example in the fuselage or in a wing in the case of a wing of sufficient thickness, or externally, for example under a wing.

[0072] In the embodiment of Figures 2 and 3, the buffer tank device 7 comprises a tank 27 and a closure member 28. The tank 27 is rigid. The tank 27 is thermally insulating. The tank 27 is gas-tight. The tank 27 is resistant to cryogenic temperatures inside said tank 27. The tank 27 is resistant to rapid temperature changes. In the embodiments shown, the tank 27 is multi-layered.

[0073] An opening 29 is provided in the tank 27. In the opening 29 is arranged the closure member 28 ensuring the maintenance of the contents, and allowing the filling with the contents and the emptying of the contents towards downstream members.

[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 to the inside, a first layer 31, a second layer 32 and a third layer 33, see [Fig. 3]. Alternatively, the wall comprises, from the outside to the inside, 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, its rigidity and an external mechanical connection with a tank support 27. The first layer 31 may be thermally insulating. The inner layer 34 has a specific heat capacity lower than a specific heat capacity of 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 part, a bottom in the shape of an arc of a circle, for example hemispherical, and a top in the shape of an arc of a circle, for example hemispherical. The top is surmounted by a neck 30 which delimits a bore. The neck 30 may have a thickness greater than the thickness of the central part and the bottom to absorb the mechanical forces transmitted by the closure 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, and a matrix. The first layer 31 is resistant to cryogenic temperatures and rapid temperature variations. The first layer 31 has a first thickness. The 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, here, over the height of the tank 27.

[0078] The second layer 32 is gas-tight. The second layer 32 makes the tank 27 leak-tight, if necessary against small molecules such as H2. The leak-tightness of the second layer 32 is better than 10 10 Pa.mVs against 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 adherent. The second layer 32 is continuous, except for the opening 29. The second layer 32 extends, here, over the height of the tank 27 less 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 may be made of polymer, for example fiber-reinforced PU foam. Alternatively, the third layer 33 may 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 may be between 1 and 100 mm. The second layer 32 and the third layer 33 are preferably mutually adherent. The third layer 33 is continuous, except for the opening 29. The third layer 33 extends, here, over the height of the tank 27 less 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 impervious to liquefied gas. Gas-tightness is optional. The inner layer 34 provides the tank 27 with 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, resistant to cryogenic temperatures and low surface mass is used for the intended use.

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

[0083] In the embodiment of [Fig.3], the inner layer 34 is adherent 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 low thickness, in particular between 10 and 300 microns.

[0084] In the embodiment of [Fig.4], the inner layer 34 is free relative 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 may then form a chamber 35. The chamber 35 may be of variable volume. The inner layer 34 may then have a thickness of between 0.01 and 1 mm.

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

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

[0087] The tank 27 comprises an insert 37. The insert 37 is sealed. 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 of 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 shape matching. The insert 37 may be fixed to the neck 30 and to the top of the tank 27 by gluing. The insert 37 is made in a single piece. The insert 37 has a central lumen forming the opening 29.

[0089] The opening 29 is axial. The opening 29 has a grooved or helical peripheral surface. Here, the groove or helix is ​​in the form of chevrons, seen in axial section, to lengthen the heat conduction path. The opening 29 may be coated with a coating of a material different from the material of the insert 37.

[0090] The closure member 28 is sealed. The closure member 28 is pressure-resistant. The closure member 28 is removable. The closure member 28 comprises a cap-forming body. The body comprises a lower portion 40 housed in the opening 29 and an upper portion 41 projecting from the opening 29. The upper portion 41 is in contact with an upper surface of the neck 30.

[0091] The closure member 28 comprises a filling line 42 passing through the body between the exterior and the interior of the tank 27.

[0092] The closure member 28 comprises a draw-off line 43 passing through the body between the outside and the inside of the tank 27. The draw-off line 43 can serve as a vent. The draw-off line 43 is provided for obtaining gas and supplying it downstream. In the body, the draw-off line 43 and the filling line 42 are parallel and spaced apart from each other.

[0093] In the embodiment shown in [Fig. 2], the closure member 28 comprises at least one additional feedthrough. In the additional feedthrough is mounted an internal heating member 44. Here, the heating member 44 passes through two additional feedthroughs. The heating member 44 serves to accelerate the gasification after filling and the second and third valves being closed or at least the second valve 12 being closed. The heating member 44 extends in a high area of ​​the tank, for example in the top of the tank and, if appropriate, in the cylindrical central part. The heating member 44 can be provided above the maximum level of liquefied gas. The heating member 44 extends into the gaseous headspace.

[0094] The heating member 44 may be electric, an additional feedthrough being sufficient.

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

[0096] In the embodiment of [Fig.l], the heating member 8 is mounted outside the tank 27. In the embodiments shown in Figures 5 and 6, the heating member 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 upper part 41 of the body of the closure member 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 with respect to the third layer 33 and gas-tight. The inner layer 34 forms with the wall, a chamber 35 in communication with the outside. The communication with the outside is used to fill the chamber 35 and to refill the chamber. Said chamber 35 is filled with insulating gas, for example Ar. After filling, said chamber 35 is closed. The heating of the liquefied gas when filling the tank is then 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 closure member 28.

[0099] Figures 7 to 11 show the steps of implementation of the buffer tank device 7. The buffer tank device 7 is in the operational state, with the closure member 28 firmly attached 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 carried out by supplying a liquefied gas into the tank 27 and degassing. The liquefied gas may be the same as in the following steps or a neutral gas, for example nitrogen. The withdrawal line 43 is open while the filling line 42 supplies the liquefied gas. The discharge 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 stage.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 step of filling with liquefied gas, precursor of the combustible gas, begins. Filling is carried out via the filling line 42. The withdrawal line 43 is opened then closed during the second step or closed from the start of the second step. A gaseous ceiling 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 step. The duration of the second step is as short as possible. The brevity of the second step is less crucial than the brevity of the first step. The invention makes it possible to reduce the duration of the second step. The pressure increases during the second step. The pressure at the end of the second step is equal to or lower than the pressure of the cryogenic tank supplying the liquefied gas. The pressure at the end of the second step is between 6 and 10 bars.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 step begins. The pressurization can be assisted by the heating member 44. The heating member 44 is activated for a sufficient time to allow the pressure in the tank 27 to reach the minimum pressure necessary to supply combustible gas downstream. The heating member 44 is inactive during the other steps. The withdrawal line 43 is closed and the filling line pleating 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 crucial 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 is simultaneous with a rise in temperature.

[0102] The filling line 42 is closed. Once pressurization is obtained, the fourth withdrawal step begins. The withdrawal line 43 is open. The duration of the fourth step is variable depending on the demand for combustible gas downstream. The pressure at the end of the fourth step 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 step depends on the characteristics of the compressor 20 and may be lower than ambient pressure. In the absence of a compressor 20, the pressure at the end of the fourth step depends on the characteristics of the consumer member 3. The pressure at the end of the fourth step may be from 1 to 50 bars.

[0103] Once the pressurization is obtained, the fourth withdrawal stage begins. The withdrawal line 43 is open. The filling line 42 is closed. The duration of the fourth stage is variable according to the downstream demand for combustible gas. The temperature rises gradually according to the withdrawn flow rate. If the withdrawn flow rate is high, the temperature rise is slow. If the withdrawn 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 characteristics of the compressor and may be lower than ambient pressure. In the absence of a compressor, the pressure at the end of the fourth stage depends on the characteristics of the consumer member 3. The pressure at the end of the fourth stage may be from 1 to 50 bars.The pressure at the end of the fourth stage is at a level at which the withdrawal of combustible gas is zero.

[0104] Once the pressure at the end of the fourth stage is reached, the fifth stage of returning to ambient pressure begins. The fifth stage is optional. If the pressure at the end of the fourth stage is higher than ambient pressure, degassing 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 ambient pressure, for example 1013 hPa at ground level or 265 hPa at 10,000 m altitude. The fifth stage is provided in the absence of a compressor or if the compressor 20 does not provide sufficient flow or efficiency to provide a requested flow of fuel gas towards the end of the fourth step.

[0105] After the fifth step, either the tank 27 is cold enough and we move directly to the second step, or we move on 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 member 3 of said aircraft, from at least one source of liquefied gas 2 of said aircraft. The buffer tank device 7 comprises a tank 27 and a closure member 28. The tank 27 comprises a set of structural layers, thermally insulating and gas-tight, and an inner layer that is tight against liquefied gas and has a lower thermal capacity than each of the layers of the set of layers. The inner layer may be thermally conductive.

[0107] Thanks to the high-pressure two-phase buffer tank device, the low thermal capacity inner layer reduces the vaporization of the liquefied gas and therefore the pressure increase during filling. Losses are reduced. Filling time is reduced. 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

Claims

1. High pressure two-phase buffer tank device (7) for distributing combustible gas to at least one gas consuming member (3), from at least one source of liquefied gas (2), the device comprising a tank (27) and a closure member (28), the tank (27) comprising a structural wall, thermally insulating and gas-tight, and an inner layer (34) with a lower thermal capacity than the structural wall and tight to liquefied gas.

2. Device according to claim 1, in which the structural wall comprises a first structural and thermally insulating layer (31), made of carbon fiber composite material, at least one second gas-tight layer (32) made of polymer, the inner layer (34) having a lower thermal capacity than the first layer (31) and the second layer (32), and, where appropriate, a third layer (33) more thermally insulating than the first and second layers, the inner layer (34) then having a lower thermal capacity than the third layer.

3. Device according to one of the preceding claims, in which the inner layer (34) is made of a metallic material, notably chosen from: aluminum, 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 one of the preceding claims, in which the inner layer (34) is adherent to the structural wall.

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

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

7. A device according to any preceding claim, wherein the inner layer (34) is less insulating than each of the first and second layers and, where appropriate, is less insulating than the third layer and has a lower specific heat capacity than the third layer.

8. Device according to one of the preceding claims, in which the layers of the structural wall are mutually adherent.

9. Device according to one of the preceding claims, in which the closure member (28) comprises a plug and at least one passage for filling with liquefied gas and for withdrawing combustible gas.

10. Gas distribution assembly (1) between at least one source of liquefied gas (2) and at least one gas consuming member (3), comprising at least one first valve (11), all or nothing, controlled at the outlet of each source of liquefied gas (2), a cryogenic distributor (5) connected to each first controlled valve (11), and supplied with liquid, second valves (12), all or nothing, controlled, connected to the cryogenic distributor (5), in parallel, buffer tank devices (7) according to one of the preceding claims, supplied with liquid, each 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), to supply gas, a pressure reducer (9) mounted at the outlet of the third controlled valves (13), a manifold (10) supplied by the pressure reducer (9) to supply said at least one consumer organ (3).

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