Valve for a cryogenic fluid

Abstract

A valve for a cryogenic fluid and a supply circuit for a cryogenic fluid, the valve comprising: a control chamber (11); a first flow chamber (12) that communicates with the control chamber (11) via a control orifice (14); a second flow chamber (13) that communicates with the first flow chamber (12) via a flow orifice (15) that forms a valve seat; a linear-stroke actuator (20) that is accommodated in the control chamber (11) and configured to actuate a control rod (24) which penetrates the control orifice (14) and extends axially into the first flow chamber (12); a valve gate (25) that is movable between a closed position and an open position; and bellows (30) that surround the control rod (24) and are sealed while being axially stretchable.

Description

Valve for cryotechnical fluid Technical Field

[0001] This presentation concerns a valve for cryogenic fluids and a circulation circuit for cryogenic fluids. Such a valve can be used, in particular, in a circulation circuit for liquid propellant in an engine, for example, a hydrogen-powered aircraft engine. Previous technique

[0002] To drastically reduce the carbon footprint of commercial aircraft, hydrogen-powered aircraft engine projects are under development. However, using hydrogen in such an aircraft engine raises numerous technical implementation challenges. In particular, this hydrogen is generally stored and distributed in liquid form, and therefore at cryogenic temperatures, before potentially being heated prior to its admission into the engine's combustion chamber. While cryogenic propellant technology is well-established in the space sector, it cannot be directly transposed to the aeronautical field due to the specific characteristics of this sector.

[0003] One of the challenges encountered concerns the fuel supply system and, more specifically, the pump within this system. Indeed, existing pumps used in the space sector are designed to provide relatively constant fuel flow rates: thus, these pumps have a limited number of operating points, which simplifies their design and allows for highly precise optimization of the pump to the operating conditions. Conversely, an aircraft engine must be able to operate in very different situations, with significantly different thrust regimes depending on the flight phase: taxiing, takeoff, cruise, landing, etc.

[0004] Due to the very low temperatures, on the order of 20 K, and very high pressures, on the order of 10 bar and potentially up to 70 bar, of the liquid hydrogen supplied by the engine's fuel system, the pump can may be required to operate in unstable operating ranges when the flow through the pump is too low.

[0005] Another challenge lies in designing valves capable of operating at very low temperatures while controlling low flow rates. Indeed, valves currently used in the aeronautical field are not designed to withstand the passage of cryogenic fluids, whereas valves currently used in the space sector are designed to handle much higher flow rates.

[0006] Finally, for aeronautical applications, the valve must be capable of performing a very large number of missions without degrading. Most valves used in the space sector are designed for only a single mission and therefore could not guarantee a satisfactory operating time for aeronautical applications.

[0007] There is therefore a real need for a cryotechnical fluid valve and a cryotechnical fluid circulation circuit that are free, at least in part, from the disadvantages inherent in the aforementioned known configurations. Description of the invention

[0008] This presentation relates to a valve for cryogenic fluid, comprising a control chamber, a first circulation chamber communicating with the control chamber via a control port and configured to be connected to a first cryogenic fluid line, a second circulation chamber communicating with the first circulation chamber via a circulation port, forming a valve seat, and configured to be connected to a second cryogenic fluid line, a linear stroke actuator housed in the control chamber and configured to actuate a control rod passing through the control port and extending axially into the first circulation chamber, and a shutter movable between a closed position, in which it is clamped against the valve seat, and an open position, in which it is at least partially away from the valve seat, the valve being configured so that the position of the obturator is at least partly controlled by the position of the control stem, and a bellows, sealed but axially stretchable, surrounding the control stem, a first end of the bellows being integral with a wall of the first circulation chamber, and a second end of the bellows being integral with the control stem.

[0009] The use of a linear stroke actuator allows fine adjustment of the flow rate of cryotechnical fluid passing through the circulation orifice by acting precisely on the valve shutter and therefore on the fluid passage area thus determined.

[0010] The use of a sealed bellows allows for the complete isolation of the control chamber, which houses the actuator, from the cryogenic fluid circulation. This protects the actuator from direct contact with the cryogenic fluid, which could damage it. Furthermore, this bellows provides thermal decoupling, at least partially, between the control chamber and the circulation chambers, while still allowing the actuator command to be transmitted to the shutter. Indeed, the bellows can extend axially to follow the movement of the control rod without breaking or compromising the seal. It is therefore possible to maintain a warmer environment in the control chamber compared to the circulation chambers, enabling the use of an actuator that would otherwise be unable to operate at the temperature of the cryogenic fluid.

[0011] In this presentation, cryotechnical fluid means a fluid, preferably a liquid, whose temperature is less than 120 K, preferably less than 80 K, preferably even less than 30 K. The pressure of the cryotechnical fluid may exceed 2 bars, preferably 10 bars or even 50 bars.

[0012] In some embodiments, the cryotechnical fluid is a liquid propellant, for example liquid dihydrogen H2, liquid dioxygen O2, liquid dinitrogen N2, liquid helium He or liquid methane CH4.

[0013] In some embodiments, the maximum flow rate of the valve is less than 100 g / s, preferably less than 50 g / s, and preferably even less than 10 g / s.

[0014] In some embodiments, the maximum hydraulic passage cross-section of the valve is less than 25 mm 2 preferably less than 10 mm 2preferably even less than 5 mm 2 .

[0015] In some embodiments, the control chamber is maintained under vacuum or in a neutral atmosphere. This allows the actuator to be kept in a controlled environment conducive to its proper operation. In particular, this can help to thermally insulate the actuator from the circulating chambers. When the chamber is maintained under vacuum, the residual pressure within the chamber can be less than 30 mbar. When the chamber is maintained in a neutral atmosphere, it can be filled with helium (He) or nitrogen (N2).

[0016] In some embodiments, the temperature in the control chamber is greater than 50 K, preferably greater than 150 K.

[0017] In some embodiments, the actuator includes a piezoelectric actuator. Such an actuator, with its very short stroke, allows for particularly precise adjustment of the control rod position and therefore the position of the gate. This makes it particularly well-suited for forming a valve that provides fine flow rate control. Furthermore, such an actuator has high stiffness, meaning the valve's passage area depends almost exclusively on the actuator's control voltage. Open-loop control of the actuator can then be implemented without significant risk of drift.

[0018] In some embodiments, the piezoelectric actuator is equipped with a stroke amplifier, preferably of the pantograph type. Since the native stroke of a piezoelectric actuator is very short, such an amplifier amplifies the actuator's movement and thus increases the maximum stroke of the control rod.

[0019] In some embodiments, the maximum stroke of the actuator is less than 5 mm, preferably less than 1 mm, preferably even less than 0.5 mm. This maximum stroke is preferably measured after amplification when an amplifier is used. The actuator is therefore very precise and particularly suitable for a valve controlling low flow rates.

[0020] In some embodiments, the height of the control chamber, in the axial direction, is less than 10 cm, preferably less than 6 cm. The valve is thus particularly compact.

[0021] In some embodiments, the second circulation chamber is configured as the upstream chamber of the valve, while the first circulation chamber is configured as the downstream chamber. In such a case, it is understood that the pressure is higher in the second circulation chamber than in the first. However, the reverse configuration is possible. In some configurations, the upstream and downstream positions could also vary over time depending on the operation of the circuit in which the valve is installed. In particular, in the configurations described, when the obturator is fixed to the end of the control stem, the intrinsic sizing of the valve makes it insensitive to the pressure effects on the obturator compared to those generated by the actuator. This allows for the straightforward reversal of the upstream and downstream connections.

[0022] In some embodiments, the circulation orifice is circular, preferably centered approximately on the axis of the control rod. This facilitates centering the obturator on its seat and promotes a good seal of the obturator in the closed position. The diameter of this orifice can be, in particular, on the order of 6 mm.

[0023] In some embodiments, the obturator is installed in the first or second circulation chamber. When the obturator is installed in the upstream circulation chamber, the pressure of the cryogenic fluid exerts a force on the obturator, tending to close the valve. This promotes centering of the obturator when it is free and ensures a good seal in the closed position.

[0024] In some embodiments, the shutter is fixed to the distal end of the control rod. The position of the shutter, and therefore the cross-section of passage, is thus directly determined by the position of the control rod and therefore by the actuator.

[0025] In some embodiments, the obturator is separate from the control rod. In such a configuration, the obturator is located in the upstream circulation chamber so that the pressure of the cryogenic fluid tends to press the obturator against the control rod: in this way, the position of the obturator, and therefore the flow area, remains determined by the position of the control rod. However, the obturator remains free to reposition itself and, in particular, to recenter itself on its seat in the closed position, even if the control rod is slightly off-center: this promotes good sealing of the obturator in its closed position.

[0026] In some embodiments, the obturator is retained in a cage provided in the first or second circulation chamber. Such a cage, perforated to allow the cryogenic fluid to pass through, prevents the obturator from making excessive excursions, even in the event of instability in the cryogenic fluid circulation.

[0027] In some embodiments, the shutter is axisymmetric. This facilitates centering and a good seal of the shutter.

[0028] In some embodiments, the shutter has a portion whose cross-section decreases in the axial direction, this portion preferably being a truncated cone or a truncated sphere.

[0029] In some embodiments, the obturator is a ball, preferably spherical. The diameter of the ball can be, in particular, on the order of 8 mm.

[0030] In some embodiments, the obturator is a cylindrical sleeve, closed at least at one of its axial ends, and whose peripheral surface includes at least one aperture. Such a cylindrical sleeve allows for better control of the valve's passage area as a function of the position of the control rod. In particular, it is possible to configure the geometry of this aperture to adjust the relationship determining the passage area as a function of the position of the cylindrical sleeve connected to the control rod.

[0031] In some embodiments, at least one opening in the cylindrical socket is rectangular or triangular. A rectangular opening results in a linear control law of the passage section as a function of the position of the control rod while a triangular opening results in a non-linear control law.

[0032] In some embodiments, the actuator is configured to continuously adjust the position of the control rod so as to continuously control the position of the shutter between the closed position and a maximum open position. The valve can thus be continuously and precisely adjusted to any operating point between its two extreme positions.

[0033] In some embodiments, the actuator is configured to be controlled in open loop. This eliminates the need for a position sensor in the valve.

[0034] In some embodiments, the valve includes a sensor configured to determine the position of the control rod. This may, in particular, be a position sensor taking the form, for example, of a Hall effect probe used in proximity measurement.

[0035] In some embodiments, the actuator is configured to be controlled in a closed loop. This ensures greater accuracy in valve control.

[0036] In some embodiments, the bellows wall is corrugated, with the corrugations running in succession along the axial direction. These corrugations provide the bellows with a degree of elasticity in the axial direction. Preferably, these corrugations are axisymmetric.

[0037] In some embodiments, the bellows has a resting length greater than 15 mm, preferably greater than 20 mm. Preferably, this resting length does not exceed 50 mm.

[0038] In some embodiments, the bellows has, at rest, a maximum outside diameter of between 6 and 10 mm.

[0039] In some embodiments, the depth of the bellows corrugations is between 1 and 2 mm. "Corrugation depth" here refers to the difference between the diameter measured at the crests and the diameter measured at the level of the troughs. Preferably, all the undulations are identical.

[0040] In some embodiments, the bellows is hydroformed.

[0041] In some embodiments, the bellows is metallic, preferably made of steel. Such a metallic material is capable of withstanding the cryotechnical temperatures of the cryotechnical fluid.

[0042] In some embodiments, the stiffness of the bellows, in the face of an axial extension force, is less than 30 N / mm.

[0043] In some embodiments, the first end of the bellows is fixed, preferably welded, to the wall of the first circulation chamber surrounding the control orifice.

[0044] In some embodiments, the second end of the bellows is fixed, preferably welded, to a flange extending radially from the control rod.

[0045] In some embodiments, the first and second circulation chambers do not have elastomeric seals. This is because an elastomeric seal would not withstand the temperature of the cryogenic fluid. Instead, polymer or metal-to-metal contact seals can be used.

[0046] The present exposition also relates to a circulation circuit for cryotechnical fluid, comprising a pump, having an inlet connected to an upstream line and an outlet connected to a downstream line, a recirculation line, extending from the downstream line to the upstream line, and a valve according to any of the preceding embodiments, installed on the recirculation line so as to control the flow of the recirculation line.

[0047] Thanks to such a recirculation line, it is possible to control the pump with a minimum flow rate high enough to ensure stable pump operation and to redirect, when this minimum flow rate exceeds the desired circulation flow rate, a portion of this flow upstream of The pump is used to obtain the desired flow rate downstream of the circulation circuit. Thus, if the desired flow rate is less than the minimum stable flow rate, the pump is driven at the minimum stable flow rate and the recirculation line valve is controlled to return the difference between the minimum stable flow rate and the desired circulation flow rate to the upstream line; if the desired flow rate is greater than the minimum stable flow rate, the pump is driven to ensure the desired circulation flow rate and the valve is controlled to close completely the recirculation line.

[0048] A valve according to the present exposition then makes it possible to accomplish this function of fine regulation of the recirculation line under cryotechnical conditions.

[0049] In some embodiments, the circulation circuit is a supply circuit intended to supply an engine with said cryotechnical fluid, possibly after heating the latter.

[0050] In some embodiments, the pump is a centrifugal pump, preferably a turbopump or a pump driven by an electric motor.

[0051] In this exposition, the terms "front" and "distal" are understood, along the direction of the control rod, on the obturator side; the terms "rear" and "proximal" are then understood on the opposite side from the obturator.

[0052] The aforementioned features and advantages, as well as others, will become apparent upon reading the detailed description that follows, along with examples of the proposed valve and circulation circuit implementation. This detailed description refers to the attached drawings. Brief description of the drawings

[0053] The attached drawings are schematic and are primarily intended to illustrate the principles of the presentation.

[0054] In these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference symbols.

[0055] [Fig. 1] Figure 1 represents an example of a circulation circuit.

[0056] [Fig. 2] Figure 2 represents an example of a valve, in an open state.

[0057] [Fig. 3] Figure 3 represents the valve from Figure 2, in a closed state. Description of the implementation methods

[0058] To make the explanation more concrete, examples of circulation circuits and valves are described in detail below, with reference to the attached drawings. It should be noted that the invention is not limited to these examples.

[0059] Figure 1 shows an example of a cryogenic fluid circulation circuit 1; more specifically, it is a liquid propellant supply circuit for an aircraft engine. The supply circuit 1 comprises a propellant tank 2, a centrifugal feed pump 3, and a feed outlet 4 connected to the engine. An upstream line 3m connects the propellant tank 2 to the inlet of the feed pump 3; a downstream line 3v connects the outlet of the pump 3 to the feed outlet 4. In this example, the tank 2 contains liquid hydrogen (H2) stored at approximately 20 K; the pressure downstream of the pump 3 is on the order of 10 bar.

[0060] The supply circuit 1 further includes a recirculation line 5 connecting the downstream line 3v to the upstream line 3m bypassing the supply pump 3. A pilot valve 10 is positioned on this recirculation line 5.

[0061] Figure 2 illustrates an example of such a pilot-operated valve 10. This valve 10 comprises a control chamber 11, a first circulation chamber 12 and a second circulation chamber 13.

[0062] The first circulation chamber 12 extends from the control chamber 11, axially along a main axis A of the valve 10; a control orifice 14 is made, at the level of the main axis A, in the wall separating the first circulation chamber 12 from the control chamber 11.

[0063] The second circulation chamber 13 is provided as an extension of the first circulation chamber 12, in the axial direction; a circulation opening 15 is made, at the level of the main axis A, in the wall separating the second circulation chamber 13 from the first circulation chamber 12. In this example, the second circulation chamber 13 is the chamber upstream, thus connected to the downstream line 3v of pump 3, and the first circulation chamber 12 is the downstream chamber, thus connected to the upstream line 3m of pump 3.

[0064] An actuator 20, comprising a piezoelectric component 21 and an amplifier 22, is mounted in the control chamber 11. The piezoelectric component 21 extends in a direction orthogonal to the main axis A. The amplifier 22 takes the form of two pantographs 23, each mounted on an opposite face of the piezoelectric component 21. Each pantograph 23 thus comprises two elastic arms 23a, each fixed to an opposite end of the piezoelectric component 21 and joining at a central base 23b extending axially.

[0065] The piezoelectric component 21 has a predetermined rest length at rest; consequently, the actuator 20 as a whole has a predetermined rest height at rest, measured between the ends of the bases 23b of the two pantographs 23 of the amplifier 22. However, when an electrical voltage is applied to the piezoelectric component 21, the piezoelectric component 21 deforms so that its length increases; consequently, the arms 23a of the pantographs are spread apart, which brings the bases 23b closer together and therefore decreases the height of the actuator 20.

[0066] One of the bases 23b of the amplifier 22 is fixed in the control chamber 11, while the second base 23b is free to move. A control rod 24 is fixed to this second base 23b so as to extend axially along the main axis A: the control rod 24 thus extends through the control port 14 and along the first circulation chamber 12, substantially as far as the circulation port 15.

[0067] An obturator 25, here taking the form of a spherical ball, is disposed in the second circulation chamber 13, just opposite the circulation orifice 15 which forms a seat for said obturator 25.

[0068] In this example, the shutter 25 is free, that is, it is not fixed to the end of the control rod 24. The position of the shutter 25 is nevertheless constrained by the position of the control rod 24, the latter depending on its position, it may prevent the obturator 25 from pressing against the circulation orifice 15. Furthermore, a cage 26, installed in the second circulation chamber 13 and in which the obturator 25 is housed, allows the obturator 25 to be held radially.

[0069] Thus, when the actuator 20 is at rest, as shown in Figure 2, the actuator 20 has a maximum height H max , corresponding to its rest height; the control rod 24 is then in an advanced position in which it engages in the circulation orifice 15, thus pushing back the obturator 25 so as to prevent it from pressing against the circulation orifice 15. The valve 10 is thus in an open state in which propellant can pass from upstream to downstream of the second circulation chamber 13 to the first circulation chamber 12.

[0070] Conversely, as shown in Figure 3, when an electrical voltage is applied to the piezoelectric component 21, the height of the actuator 20 decreases until it reaches a minimum height H min , which retracts the control rod 24 into a retracted position in which it no longer obstructs the movement of the obturator 25; the obturator 25, under the effect of the fluid pressure, centers itself and then presses against the circulation orifice 15. The valve 10 is thus in a closed state in which the circulation of the propellant between the second circulation chamber 13 and the first circulation chamber 12 is cut off.

[0071] Of course, by adjusting the voltage supplied to the actuator 20, it is possible to finely control it in order to precisely adjust its height and therefore the position of the control rod 24, and consequently the position of the obturator 25, the latter being normally pulled back against the end of the control rod 24 by the pressure forces of the fluid. It is thus possible to precisely and continuously adjust the passage area of ​​the valve 10 between the two extreme states, fully open and closed, shown in Figures 2 and 3.

[0072] In this example, the maximum height H max The actuator's diameter is equal to 55.0 mm, while its minimum height is H. min is equal to 54.5 mm.

[0073] The valve 10 further includes a metal bellows 30, here made of stainless steel. The bellows 30, generally axisymmetric, comprises successive undulations in the axial direction. The rear end 31 of the bellows 30 is fixed to the wall of the first circulation chamber 12 so as to surround the control orifice 14. The front end 32 of the bellows is fixed to a radial flange 33 integral with the control rod 24.

[0074] The bellows 30 thus isolates the control chamber 11, and therefore the actuator 20, from the propellant circulation present in the first circulation chamber 21. However, thanks to its undulations, the bellows has an elasticity which allows it to follow the movement of the control rod 24 without breaking.

[0075] In this example, the bellows 30 has a stiffness of 27 N / mm and a rest length of 20 mm; its maximum diameter, measured at the crests of the corrugations, is 8.5 mm.

[0076] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

[0077] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

Claims

Claims

1. A control valve for cryogenic fluid, comprising a control chamber (11), a first circulation chamber (12), communicating with the control chamber (11) via a control orifice (14), and configured to be connected to a first cryogenic fluid line (3m), a second circulation chamber (13), communicating with the first circulation chamber (12) via a circulation orifice (15), forming a valve seat, and configured to be connected to a second cryogenic fluid line (3v), a control rod (24) passing through the control orifice (14) and extending axially in the first circulation chamber (12), a linear stroke actuator (20), housed in the control chamber (11) and configured to actuate the control rod (24), said linear stroke actuator (20) comprising a piezoelectric actuator (21), a shutter (25),movable between a closed position, in which it is pressed against the valve seat (15), and an open position, in which it is at least partially at a distance from the valve seat (15), the valve (10) being configured so that the position of the shutter (25) is at least partly controlled by the position of the control rod (24), and a bellows (30), sealed while being axially stretchable, surrounding the control rod (24), a first end (31) of the bellows (30) being secured to a wall of the first circulation chamber (12), and a second end (32) of the bellows (30) being secured to the control rod (24) and in which the maximum hydraulic passage section of the valve is less than 25 mm, 2 .

2. A valve according to claim 1, wherein the control chamber (11) is maintained under vacuum or in a neutral atmosphere.

3. Valve according to claim 1 or 2, wherein the piezoelectric actuator (21) is equipped with a stroke amplifier (22), preferably of the pantograph type.

4. A valve according to any one of claims 1 to 3, wherein the shutter (25) is attached to the distal end of the control rod (24).

5. A valve according to any one of claims 1 to 3, wherein the shutter (25) is separate from the control rod (24), and wherein the shutter (25) is retained in a cage (26) provided in the first circulation chamber (12) or the second circulation chamber (13).

6. A valve according to any one of claims 1 to 5, wherein the actuator (20) is configured to continuously adjust the position of the control rod (24) so ​​as to control the position of the shutter (25) continuously between the closed position and a maximum open position.

7. A valve according to any one of claims 1 to 6, wherein the wall of the bellows (30) is corrugated, the corrugations following one another in the axial direction.

8. A valve according to any one of claims 1 to 7, wherein the bellows (30) is metallic, preferably steel.

9. Valve according to any one of claims 1 to 8, in which the stiffness of the bellows (30), faced with an axial extension force, is less than 30 N / mm.

10. A valve according to any one of claims 1 to 9, wherein the first end (31) of the bellows (30) is fixed, preferably welded, to the wall of the first circulation chamber (12) surrounding the control orifice (14), and wherein the second end (32) of the bellows (30) is fixed, preferably welded, to a flange (33) extending radially from the control rod (24).

11. Circulation circuit for cryogenic fluid, comprising a pump (3), having an inlet connected to an upstream line (3m) and an outlet connected to a downstream line (3v), a recirculation line (5), extending from the downstream line (3v) to the upstream line (3m), and a valve (10) according to any one of the preceding claims, installed on the recirculation line (5) so as to control the flow rate of the recirculation line (5).

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