valve for cryotechnical fluid

Abstract

A valve for cryogenic fluid and a supply circuit for cryogenic fluid, the valve comprising a control chamber (11), a first circulation chamber (12) communicating with the control chamber (11) via a control port (14), a second circulation chamber (13) communicating with the first circulation chamber (12) via a circulation port (15), forming a valve seat, a linear stroke actuator (20) housed in the control chamber (11) and configured to actuate a control stem (24) passing through the control port (14) and extending axially into the first circulation chamber (12), a shutter (25) movable between a closed and an open position, and a bellows (30), sealed but axially extendable, surrounding the control stem (24). Fig. 2

Description

Title of the invention: Valve for cryotechnical fluid technical field

[0001] The present description relates to a valve for cryogenic fluid and a circulation circuit for cryogenic fluid. Such a valve can, in particular, be used in a circulation circuit for liquid propellant in an engine, for example, a hydrogen-powered aircraft engine. Previous technique

[0002] In order to drastically reduce the carbon footprint of commercial aircraft, hydrogen-powered aircraft engine projects are under development. However, the use of 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 possibly 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 difficulties encountered concerns the fuel supply circuit and, in particular, the pump of this supply circuit. Indeed, the pumps currently used in the space sector are designed to provide relatively constant supply flow rates: thus, these pumps have a reduced number of operating points, which simplifies their design and allows for highly optimized pump performance under operating conditions. Conversely, an aircraft engine must be able to operate in very different situations, with very different thrust regimes depending on the phase of flight: taxiing, takeoff, cruise, landing, etc.

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

[0005] Another difficulty concerns the design of valves capable of operating at very low temperatures while controlling low flow rates. Indeed, valves known to date in the aeronautical field are not designed to withstand the passage of a cryogenic fluid, whereas valves known to date in the space sector They, for their part, are sized to be traversed by much larger flow rates.

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

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

[0008] The present description relates to a valve for cryotechnical fluid, comprising a control room, a first circulation chamber, communicating with the control chamber via a control orifice, and configured to be connected to a first cryogenic fluid line, a second circulation chamber, communicating with the first circulation chamber via a circulation orifice, 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 orifice and extending axially into the first circulation chamber, a shutter, movable between a closed position, in which it is pressed 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 shutter is at least partly controlled by the position of the control stem, and a bellows, sealed but axially stretchable, surrounding the control rod, one end of the bellows being attached to a wall of the first circulation chamber, and a second end of the bellows being attached to the control rod.

[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 finely on the valve shutter and therefore on the fluid passage section thus determined.

[0010] The use of a sealed bellows makes it possible to completely isolate the control chamber, in which the actuator is housed, from the flow of cryogenic fluid. This protects the actuator from direct contact with cryogenic fluid, which could damage it. Furthermore, this bellows allows for decoupling Thermally, at least partially, the control chamber and circulation chambers are insulated, while still allowing the actuator command to be transmitted to the shutter. This is because 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 the present description, cryotechnical fluid means a fluid, preferably a liquid, whose temperature is less than 120 K, preferably less than 80 K, and 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 even more preferably less than 10 g / s.

[0014] In some embodiments, the maximum hydraulic passage area of ​​the valve is less than 25 mm2, preferably less than 10 mm2, and even more preferably less than 5 mm2.

[0015] In certain embodiments, the control chamber is maintained under vacuum or in a neutral atmosphere. This allows the actuator to be kept in a controlled atmosphere, conducive to its proper operation. In particular, this can help to thermally insulate the actuator from the circulation chambers. When the chamber is maintained under vacuum, it is understood that the residual pressure in 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 certain embodiments, the actuator includes a piezoelectric actuator. Such an actuator, with its very short stroke, allows for particularly fine adjustment of the position of the control rod and therefore of the position of the obturator. Such an actuator is thus particularly well-suited for forming a valve offering fine control of the flow rate. Furthermore, such an actuator benefits from high stiffness, so the valve's passage area depends almost exclusively on the actuator's control voltage. A control Open-loop operation of the actuator can then be considered 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 makes it possible to amplify the movement of the actuator and thus increase the maximum stroke of the control rod.

[0019] In certain embodiments, the maximum stroke of the actuator is less than 5 mm, preferably less than 1 mm, and even more preferably less than 0.5 mm. This maximum stroke is preferably measured after amplification when an amplifier is provided. The actuator is thus 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 to be the upstream chamber of the valve, while the first circulation chamber is configured to be 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 dimensions of the valve make it insensitive to the pressure effects on the obturator compared to those generated by the actuator. This makes it easy to reverse the upstream and downstream connections.

[0022] In certain embodiments, the circulation orifice is circular, preferably substantially centered 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 may, in particular, be on the order of 6 mm.

[0023] In certain embodiments, the obturator is installed in the first circulation chamber or in the 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 of the obturator in the closed position.

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

[0025] In certain 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 passage 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 certain 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 promotes centering and good sealing 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 may, in particular, be on the order of 8 mm.

[0030] In certain 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 said 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 certain embodiments, at least one opening in the cylindrical socket is rectangular or triangular. A rectangular opening results in a linear control law for the passage cross-section as a function of the position of the control rod, while a triangular opening results in a non-linear control law.

[0032] In certain embodiments, the actuator is configured to continuously adjust the position of the control rod so as to continuously control the position of the obturator 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, for example, the form of a Hall effect probe used in proximity measurement.

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

[0036] In certain embodiments, the bellows wall is corrugated, with the corrugations following one another in the axial direction. These corrugations provide the bellows with a certain 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 troughs. Preferably, all the corrugations 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, onto a flange extending radially from the control rod.

[0045] In certain embodiments, the first circulation chamber and the second circulation chamber are devoid of elastomeric seals. Indeed, An elastomeric seal would not withstand the temperature of the cryogenic fluid. However, 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 sufficiently high to ensure stable pump operation and to redirect, when this minimum flow rate exceeds the desired circulation flow rate, a portion of this flow rate upstream of the pump in order to obtain the actual desired circulation flow rate downstream of the circulation circuit. Thus, if the desired flow rate is less than the minimum stability flow rate, the pump is driven at the minimum stability flow rate and the recirculation line valve is controlled to return the difference in flow rate between the minimum stability flow rate and the desired circulation flow rate to the upstream line; if the desired flow rate is greater than the minimum stability flow rate, the pump is driven to ensure said desired circulation flow rate and the valve is controlled to close completely to shut off the recirculation line.

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

[0049] In some embodiments, the circulation circuit is a supply circuit intended to supply a motor 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 the present description, the terms "front" and "distal" are understood, along the direction of the control rod, on the side of the obturator; the terms "rear" and "proximal" are then understood on the side opposite the obturator.

[0052] The aforementioned features and advantages, as well as others, will become apparent from the following detailed description and examples of embodiments of the valve and the proposed circulation circuit. This detailed description refers to the accompanying drawings. Brief description of the drawings

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

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

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

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

[0057] [Fig.3] Fig.3 represents the valve of Fig.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 accompanying drawings. It should be noted that the invention is not limited to these examples.

[0059] Figure 1 shows an example of a circulation circuit 1 for a cryogenic fluid; 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 is a liquid hydrogen (H2) tank, 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-operated valve 10 is positioned on this recirculation line 5.

[0061] Fig. 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 in the extension of the first circulation chamber 12, in the axial direction; a circulation orifice 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 the present example, the second circulation chamber 13 is the upstream chamber, thus connected to the downstream line 3v of the pump 3, and the first circulation chamber 12 is the downstream chamber, thus connected to the upstream line 3m of the 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, at rest, a predetermined rest length; consequently, the actuator 20 as a whole has, at rest, a predetermined rest height, 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] A shutter 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 shutter 25.

[0068] In this example, the obturator 25 is free, that is to say, it is not fixed to the end of the control rod 24. The position of the obturator 25 is nevertheless constrained by the position of the control rod 24, the latter being able, depending on its position, to 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 retained radially.

[0069] Thus, when the actuator 20 is at rest, as shown in [Fig.2], the actuator 20 has a maximum height Hmax, 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 [Fig. 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 Hmin, which retracts the rod control 24 in a retracted position in which it no longer hinders 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 the latter 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 returned against the end of the control rod 24 under the effect of the fluid pressure forces. 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 the present example, the maximum height Hmax of the actuator is equal to 55.0 mm while its minimum height Hminest is equal to 54.5 mm.

[0073] The valve 10 further comprises 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 the present example, the bellows 30 has a stiffness equal to 27 N / mm and a rest length equal to 20 mm; its maximum diameter, measured at the crests of the corrugations, is equal to 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 a 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

Demands

1. Control valve for cryotechnical fluid, comprising a control chamber (11), a first circulation chamber (12), communicating with the control chamber (11) via a control port (14), and configured to be connected to a first cryotechnical fluid line (3m), a second circulation chamber (13), communicating with the first circulation chamber (12) via a circulation port (15), forming a valve seat, and configured to be connected to a second cryotechnical fluid line (3v), a control stem (24) passing through the control port (14) and extending axially into the first circulation chamber (12), a linear stroke actuator (20), housed in the control chamber (11) and configured to actuate the control stem (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 away from the valve seat (15), the valve (10) being configured so that the position of the obturator (25) is at least partially controlled by the position of the control stem (24), and a bellows (30), sealed while being axially stretchable, surrounding the control stem (24), a first end (31) of the bellows (30) being integral with a wall of the first circulation chamber (12), and a second end (32) of the bellows (30) being integral with the control stem (24) and in which the maximum hydraulic passage cross-section of the valve is less than 25 mm2, and in which the control chamber (11) is maintained under vacuum.

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

3. Valve according to claim 1 or 2, wherein the obturator (25) is fixed to the distal end of the control rod (24).

4. Valve according to claim 1 or 2, wherein the obturator (25) is disjoint from the control rod (24), and wherein the obturator (25) is retained in a cage (26) provided in the first circulation chamber (12) or the second circulation chamber (13).

5. Valve according to any one of claims 1 to 4, wherein the actuator (20) is configured to continuously adjust the position of the control rod (24) so ​​as to continuously control the position of the obturator (25) between the closed position and a maximum open position.

6. Valve according to any one of claims 1 to 5, wherein the bellows wall (30) is corrugated, the corrugations succeeding one another in the axial direction.

7. Valve according to any one of claims 1 to 6, wherein the bellows (30) is metallic, preferably made of steel.

8. Valve according to any one of claims 1 to 7, wherein the stiffness of the bellows (30), facing an axial extension force, is less than 30 N / mm.

9. Valve according to any one of claims 1 to 8, 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 stem (24).

10. Cryogenic fluid circulation circuit, 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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