Piston for machine for fluids such as hydrogen, and machine for fluids comprising such piston

Abstract

The invention relates to a piston (3) for a machine (1) for low-temperature or high-pressure fluids, such as liquid hydrogen, comprising a body (31) intended to be mounted inside a sleeve (2) of a fluid machine (1) so as to move back and forth relative thereto and intended to form, together with said sleeve (2), a chamber (4) for compressing or pumping fluids, the piston (3) further comprises a plurality of peripheral seals (5) arranged sequentially along the longitudinal direction (X) of the piston (3), the seals (5) defining stages (6) between the peripheral seals along the longitudinal direction (X) of the piston (3), at least two of the plurality of seals (5) each comprising a through-flow cross-section (51) intended to allow a fluid to flow between the stages (6), characterized in that all or some of the stages (6) have a volume that is non-uniform in the longitudinal direction (X).

Description

[0001] This invention relates to a piston for use in a fluid machine. The invention also relates to a fluid machine incorporating such a piston.

[0002] Fluid machines can be pumps or compressors. The fluid in question can be liquid hydrogen at cryogenic temperatures or under high pressure.

[0003] A fluid machine includes a sleeve and a piston, which are mounted to be movable relative to each other.

[0004] Specifically, the piston includes a body designed to be mounted inside the sleeve for reciprocating movement relative to the sleeve, the body being designed to form, together with the sleeve, a chamber for compressing or pumping fluid. Furthermore, the piston includes a plurality of peripheral seals arranged sequentially along the longitudinal direction of the piston.

[0005] These seals define volumes between them, which are referred to as stages. At least two of the plurality of seals each include a flow passage section designed to allow fluid to flow between these stages.

[0006] In the fluid machine described above, the flow of fluid through the flow cross section of the seal is designed to reduce the pressure difference recorded on either side of the seal closest to the compression chamber (referred to as the proximal seal) and thus maintain the mechanical strength of the seal.

[0007] However, the pressure differential recorded at the seal furthest from the compression chamber (referred to as the distal seal) remains very large. This distal seal is then exposed to a state known as the sonic state, in which the flow rate of fluid across its flow passage depends primarily on the upstream pressure of the fluid. Prolonged exposure of the distal seal to the sonic state adversely affects its mechanical strength and increases the risk of premature rupture.

[0008] This leads to the risk of leaks in fluid machinery.

[0009] In the case of cryogenic fluids, leakage caused by a rupture of the distal seal (or any other seal) results in the fluid being undesirably vaporized and heated. This vaporization (also known as evaporation loss) represents fluid loss in addition to losses caused by poor sealing of the seal.

[0010] Therefore, there is a need to develop pistons and fluid machines for fluid machines that at least partially overcome the disadvantages listed above.

[0011] Therefore, according to a first aspect, the present invention relates to a piston that conforms to its general definition given in the preceding preamble. According to this aspect of the invention, all or some of the flow passage sections of these seals are non-uniform in the longitudinal direction of the piston. As an alternative to or supplement to the above options, all or some of these stages have a volume that is non-uniform in the longitudinal direction of the piston.

[0012] By providing a non-uniform flow cross-section in the longitudinal direction of the piston and / or inter-seal stages with non-uniform volumes, the present invention discloses the possibility of better controlling the pressure and pressure differential exposed to each of these seals, particularly the distal and proximal seals. Therefore, the present invention reveals a way to normalize the pressure differential at each inter-seal stage.

[0013] The two options of the solution proposed in this invention (i.e., non-uniform flow cross section or non-uniform stage volume) contribute, individually or in combination, to the same technical effects described above.

[0014] Embodiments of the present invention may have one or more of the following features: - The piston body includes a series of peripheral slots, and the seals are arranged in these peripheral slots respectively; - The seal includes a portion that protrudes radially relative to the piston body; - The flow passage section is formed at the radially protruding portion; - The flow passage cross-section of the piston's intermediate seal is smaller than that of the piston's proximal seal; - The flow passage cross-section of the piston's intermediate seal is smaller than that of the piston's distal seal; - The flow passage cross-section of the distal seal is larger than that of the proximal seal; - The flow passage section of the seal is designed to reduce the curve change in the longitudinal direction, and then to increase the curve change; - The flow cross sections of the two consecutive seals are arranged to be angularly offset from each other about the longitudinal direction; - The volume of the intermediate stage is larger than that of the proximal stage; - The volume of the intermediate stage is larger than that of the distal stage; - The volume of these levels changes with an increasing curve in the longitudinal direction, followed by a decreasing curve; - All or some of these levels have a non-uniform height in the longitudinal direction; - The volume variation curves of these levels are similar to the height variation curves of these levels; - The piston includes a series of peripheral grooves formed in the stage along the body; - All or some of these grooves have a defined depth along the radial direction of the piston; - The depth of the groove is non-uniform in the longitudinal direction; - The volume variation curves of these levels in the longitudinal direction are similar to the depth variation curves of these grooves in the longitudinal direction.

[0015] According to a second aspect, the present invention relates to a machine for cryogenic or high-pressure fluids, the machine comprising a sleeve and a piston as described in any of the embodiments described above.

[0016] Further specific features and advantages will become apparent from the following description provided with reference to the accompanying drawings:

[0017] [ Figure 1 [ ] is a longitudinal cross-sectional view showing a first embodiment of a machine according to the invention, the machine including a sleeve, a piston, and a seal defining a uniform grade;

[0018] [ Figure 2 [This is a front view showing a first example of a piston of a machine according to a first embodiment, the piston being provided with a seal having a non-uniform flow cross section;]

[0019] [ Figure 3 [This is a front view showing a second example of a piston of a machine according to the first embodiment, the piston being further provided with an annular groove of the first type;]

[0020] [ Figure 4 [This is an isometric cross-sectional view showing a third example of a piston of a machine according to the first embodiment, the piston being provided with a second type of annular groove;]

[0021] [ Figure 5 [ ] is a longitudinal cross-sectional view showing a second embodiment of a machine according to the invention, the machine including a sleeve, a piston, and a seal defining a non-uniform level;

[0022] [ Figure 6 [This is a graph illustrating a first example of the variation in the flow coefficient associated with the flow cross-section of the seal, relating to the first embodiment of the machine;]

[0023] [ Figure 7 The first embodiment of the machine is illustrated with a graph showing a second example of the variation in the flow coefficient associated with the flow cross-section of the seal;

[0024] [ Figure 8 The first embodiment of the machine is illustrated with a graph showing a second example of the variation in the flow coefficient associated with the flow cross-section of the seal;

[0025] [ Figure 9The second embodiment of the machine is shown in a graph illustrating an example of the variation in inter-stage distance.

[0026] like Figure 1 and Figure 5 The invention relates to a fluid machine 1. It can be a pump or a compressor. The fluid in question can be hydrogen at cryogenic conditions or high pressures (20 bar to 400 bar or higher).

[0027] Machine 1 includes a sleeve 2 and a piston 3, with the piston at least partially disposed inside the sleeve 2. The sleeve 2 and piston 3 are mounted to be able to translate relative to each other along the longitudinal axis X of machine 1. For this purpose, either the sleeve 2 or the piston 3 is connected to an actuator (not shown).

[0028] When piston 3 is connected to actuator, piston 3 may include a head 31 (or body) disposed in sleeve 2 and an arm 32 extending outside sleeve 2. Arm 32 is connected to actuator.

[0029] Sleeve 2 and piston 3 (and particularly the head 31 of piston 3) form a chamber 4 for compressing or pumping fluid. Sleeve 2 includes at least one inlet orifice and at least one outlet orifice for allowing fluid to enter or exit chamber 4. The inlet and outlet orifices are not shown.

[0030] To ensure that chamber 4 is sealed during the compression or pumping of fluid, machine 1 includes multiple seals 5.

[0031] The seal 5 is fastened to the wall of the piston 3, and particularly to the wall of the head 31 of the piston 3. Specifically, the seal 5 is arranged sequentially around and along the head 31 of the piston 3. Thus, the seal 5 is configured to contact the inner wall of the sleeve 2.

[0032] Furthermore, the seal 5, together with the wall of the piston 3 and the wall of the sleeve 2, defines a continuous stage 6. These stages 6 communicate with each other and with the chamber 4 by means of a flow passage section 51 provided at the seal 5. Thus, the stages 6 form a reservoir for storing fluid.

[0033] Seal 5 is considered non-sealed because of the presence of flow passage section 51.

[0034] The flow passage section 51 can be formed by the orifice in the annular seal 5 and / or the gap between the two ends of the open-ring seal.

[0035] Furthermore, the flow passage sections 51 of the two consecutive seals are preferably offset at an angle relative to each other about the longitudinal axis X of the machine 1. Advantageously, this angular offset is, for example, 180°.

[0036] Finally, each flow section 51 is associated with a head loss coefficient. The product of the flow section 51 and the head loss coefficient is called the flow coefficient.

[0037] In the following text, the seal located at the center of the head 31 of the piston 3 will be referred to as the "center seal 5a". The seal located at the first end of the piston 3 and intended to be closest to the compression or pumping chamber 4 will be referred to as the "proximal seal 5b". Finally, the seal located at the second end of the piston 3 and intended to be furthest from the compression or pumping chamber 4 will be referred to as the "distal seal 5c".

[0038] Furthermore, the stage located at the center of piston 3 in stage 6 will be referred to as "center stage 6a". The stage intended to be closest to the compression or pumping chamber 4 will be referred to as "proximal stage 6b". The stage intended to be furthest from the compression or pumping chamber 4 will be referred to as "distal stage 6c".

[0039] According to the invention, all or some of the flow passage sections 51 of the seal are non-uniform along the piston 3 (or the head 31 of the piston 3). As a variant or supplement, all or some of the stages 6 have a non-uniform volume along the piston 3 (or the head 31 of the piston 3).

[0040] "Non-uniform" flow cross sections are understood to mean that not all flow cross sections have the same size (or the same dimensions).

[0041] Advantageously, such as [ Figure 2 ]and[ Figure 3 As shown more clearly in the first embodiment of machine 1, at least one central seal 5a has a flow cross section 51 that is smaller than the flow cross section 51 of the proximal seal 5b and smaller than the flow cross section 51 of the distal seal 5c.

[0042] Advantageously, the flow passage section 51 of the seal 5 extends along the piston 3 (and more specifically, along the head 31 of the piston 3) from the proximal seal 5b to the central seal 5a to reduce the curve change, and then from the central seal 5a to the distal seal 5c to increase the curve change.

[0043] It should be noted that the flow cross section 51 of the distal seal 5c can be larger than the flow cross section 51 of the proximal seal 5b.

[0044] Similar to the flow cross-section, the flow coefficient decreases along the piston 3 (and more specifically, along the head 31 of the piston 3) from the proximal seal 5b to the central seal 5a, and then increases from the central seal 5a to the distal seal 5c. Figure 6 ]and[ Figure 7 Each provides an example of how the flow coefficient varies along the head 31 of the piston 3.

[0045] In particular, in [ Figure 6 In [ ], the flow coefficient variation curve is symmetrical with respect to the central seal 5a. In contrast, in [ Figure 7 In the figure, the curve becomes asymmetrical because the flow cross section 51 of the distal seal 5c is much larger than that of the proximal seal 5b.

[0046] For piston 3, which includes N seals, the change of flow coefficient K(i) along the longitudinal direction of machine 1 can be given by the following function: in, C is the reference emission factor; A is the reference flow passage section; i represents the position of seal 5; and Let be any factor, where .

[0047] It should be noted that the flow coefficient associated with the flow cross section 51 of the distal seal 5c A larger value can be taken compared to the value provided by the function K(i) above. This value can be within the following range: .

[0048] By providing a change in the flow coefficient (and the flow cross-section of the seal) according to a sine function (such as the function described above), and by fixing the flow cross-section of the distal seal 5c within the above range, the present invention enables the filling of the first and last stages 6 of the machine 1 to be accelerated.

[0049] Therefore, this invention allows for a reduction in the pressure difference exposed to the first and last seals, and limits the time these seals are exposed to sonic conditions. This extends the service life of the first and last seals and reduces the risk of leakage through these seals.

[0050] The flow coefficient can be increased along piston 3 (and more specifically, along the head 31 of piston 3) from proximal seal 5b to distal seal 5c to amplify the curve variation. Figure 8 This demonstrates that change.

[0051] For piston 3, which includes N seals, the change of flow coefficient K(i) along the longitudinal direction of machine 1 can therefore be given by the following function: in: ; e1(i'), e2(i') and FA (i') is a function that depends on the thermodynamic state of the fluid in stage i.

[0052] The distribution of the flow coefficient K(i) given above is valid under the following conditions: in: f: Piston frequency; X: coefficient; Q(i): A function that depends on the thermodynamic state of the fluid at stage i.

[0053] Advantageously, refer again [ Figure 1 The piston 3 is provided with annular slots 33 designed to receive the seal 5. These slots 33 are regularly distributed along the head 31 of the piston 3. Therefore, the seal 5 is also regularly distributed along the head 31 of the piston 3.

[0054] It should be noted that in [ Figure 1 In the machine 1 shown, the seal 5 has a portion that protrudes radially relative to the head 31 of the piston 3. The volume of each stage 6 of the machine 1 is defined by the wall of the head 31 of the piston 3, the wall of the sleeve 2, and the protrusion of the adjacent seal 5.

[0055] exist[ Figure 3 ]and[ Figure 4 In the example shown, the head 31 of the piston 3 is provided with a series of annular grooves 34. In particular, the grooves 34 are arranged sequentially along the head 31 of the piston 3. The grooves 34 have a defined depth in the radial direction of the piston 3. The grooves 34 alternate with the seal 5.

[0056] For including according to [ Figure 3 ]or[ Figure 4 The fluid machine 1 with piston 3 of [ ], and including according to [ Figure 2 Compared to the piston 3 of the machine 1, each of the seal stages 6 has a larger volume. These increased volumes allow for the storage of a larger amount of fluid in the stages 6, and thus limit the pressure and pressure difference exposed to the proximal seal 5b and the distal seal 5c. This allows the fluid pressure to be distributed evenly among the individual seals 51.

[0057] It should be noted that, according to [ Figure 4 The groove 34 of piston 3 is proportional to [ Figure 3 The groove 34 of the piston 3 is deep. Therefore, including according to [ Figure 4 The piston 3 of the machine 1 enables a larger amount of fluid to be stored in the seal stage 6.

[0058] Advantageously, such as [ Figure 5As shown in the second embodiment of fluid machine 1 in the figure, at least one central stage 6a has a volume greater than that of the proximal stage 6b and greater than that of the distal stage 6c.

[0059] Advantageously, the volume of stage 6 increases the curve change along piston 3 from proximal stage 6b to central stage 6a, and then decreases the curve change from central stage 6a to distal stage 6c.

[0060] exist[ Figure 5 In the example shown, each stage 6 has a different height (interstage distance), but its inner and outer radii are the same as those of the other stages 6. The inner and outer radii of stage 6 are defined relative to the longitudinal axis X of machine 1 and are associated with the wall of the head 31 of piston 3 and the wall of sleeve 2, respectively.

[0061] Therefore, the change in the height (or distance) of level 6 is proportional to the change in the volume of these levels 6. Thus, the change in the height (or distance) of level 6 can follow a curve similar to the curve described above regarding the change in volume. Figure 9 This demonstrates the change in altitude of Level 6.

[0062] Advantageously, the height of stage 6 varies along piston 3, which includes N seals, using the following function: in: For reference height; i represents the position of seal 5 along piston 3; and Let be any factor, where .

[0063] In a variant not shown, the head 31 of piston 3 may include a groove 34 having a non-uniform radial depth along the head 31, while the distance between the seals remains constant along the head 31. The depth of the groove 34 may vary along the head of piston 3 according to a sinusoidal function similar to the sinusoidal function described above regarding the variation in the height of stage 6.

Claims

1. A piston (3) for a machine (1) for a cryogenic or high-pressure fluid, such as liquid hydrogen, the piston (3) comprising a body (31) intended to be mounted inside a sleeve (2) of the fluid machine (1) for reciprocating relative to the sleeve, and intended to form, together with the sleeve (2), a chamber (4) for compressing or pumping the fluid, the piston (3) further comprising a plurality of peripheral seals (5) arranged sequentially along the longitudinal direction (X) of the piston (3), the seals (5) defining stages (6) between the peripheral seals along the longitudinal direction (X) of the piston (3), at least two of the plurality of seals (5) each comprising a flow cross section (51) intended to allow the fluid to flow between the stages (6), characterized in that, All or some of these levels (6) have a non-uniform volume in the longitudinal direction (X).

2. The piston (3) as described in the preceding claim, characterized in that, The volume of the intermediate stage (6a) is greater than that of the proximal stage (6b) and greater than that of the distal stage (6c).

3. The piston (3) as claimed in any one of claims 1 and 2, characterized in that, The volume of these stages (6) increases the curve variation in the longitudinal direction (X), and then decreases the curve variation.

4. The piston (3) as described in the preceding claim, characterized in that, All or some of these levels (6) have a non-uniform height in the longitudinal direction (X), and the volume variation curve of these levels (6) is similar to the height variation curve of these levels (6).

5. The piston (3) as described in any of the preceding claims, characterized in that, The body (31) of the piston (3) includes a series of peripheral grooves (34) formed along the body (31) in these stages (6).

6. The piston (3) as described in the preceding claim, characterized in that, All or some of these grooves (34) have a defined depth along the radial direction of the piston (3), and the depth is non-uniform in the longitudinal direction (X).

7. The piston (3) as described in claims 1 and 6, characterized in that, The volume of these stages (6) of the piston varies in the longitudinal direction (X) similarly to the depth of these grooves (34) in the longitudinal direction (X).

8. The piston (3) as claimed in any of the preceding claims, characterized in that, The body (31) of the piston (3) includes a series of peripheral slots (33), in which seals (5) are arranged respectively, and the seals (5) include a portion that protrudes radially relative to the body (31) of the piston (3), and a flow passage section (51) is formed at the portion that protrudes radially.

9. The piston (3) as claimed in any of the preceding claims, characterized in that, The flow cross section (51) of the intermediate seal (5a) of the piston (3) is smaller than the flow cross section (51) of the proximal seal (5b) of the piston (3) and smaller than the flow cross section (51) of the distal seal (5c) of the piston (3).

10. The piston (3) as described in the preceding claim, characterized in that, The flow cross section (51) of the distal seal (5c) is larger than the flow cross section (51) of the proximal seal (5b).

11. The piston (3) as described in any of the preceding claims, characterized in that, The flow cross section (51) of these seals (5) decreases the curve change in the longitudinal direction (X) and then increases the curve change.

12. The piston (3) as described in any of the preceding claims, characterized in that, The flow cross sections (51) of the two consecutive seals (5) are arranged to have an angular offset relative to each other about the longitudinal direction (X).

13. A machine (1) for cryogenic or high-pressure fluids such as liquid hydrogen, the machine comprising a sleeve (2) and a piston (3) as described in any of the preceding claims, the piston (3) being mounted to be movable within the sleeve (2).

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