Pistons for machines for fluids such as hydrogen and machines for fluids including such pistons
The piston design with non-uniform flow path cross-sections and stage volumes addresses the issue of seal rupture in fluid machines by standardizing pressure differences, enhancing seal durability and reducing leakage.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- LAIR LIQUIDE SA POUR LETUDE & LEXPLOITATION DES PROCEDES GEORGES CLAUDE
- Filing Date
- 2024-05-30
- Publication Date
- 2026-06-23
Smart Images
Figure 2026520588000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a piston for a fluid machine. The present invention also relates to a fluid machine including such a piston.
Background Art
[0002] The fluid machine can be a pump or a compressor. The fluid in question can be liquid hydrogen in a cryogenic state or under high pressure.
[0003] The fluid machine includes a sleeve and a piston that are mounted so as to be able to move relative to each other.
[0004] Specifically, the piston includes a body intended to be mounted inside the sleeve so as to move back and forth relative to it, and the body is intended to form, together with the sleeve, a chamber for compressing or pumping a fluid. Further, the piston includes a plurality of peripheral seals arranged in series along the longitudinal direction of the piston.
[0005] The seals define a volume called a stage between them. At least two of the plurality of seals each include a flow path cross-section intended to allow fluid to flow between the stages.
[0006] In a fluid machine as described above, the flow of fluid through the flow path cross-section of the seal reduces the pressure difference recorded on either side of the seal closest to the compression chamber (referred to as the proximal seal), and thus is intended to maintain the mechanical strength of this seal.
[0007] However, the pressure difference 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 called the sonic state, in which the flow velocity of the fluid through its flow path cross-section mainly depends 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 poses a risk of leakage in fluid machinery.
[0009] In the case of cryogenic fluids, leakage resulting from the rupture of the distal seal (or any other seal) can lead to undesirable evaporation and heating of the fluid. Such evaporation (also known as boil-off) represents fluid loss in addition to the losses caused by the seal's failure to seal properly. [Overview of the project] [Problems that the invention aims to solve]
[0010] As a result, there is a need to develop pistons and fluid machines for fluid machinery that overcome at least some of the shortcomings listed above. [Means for solving the problem]
[0011] For this purpose, according to a first aspect, the present invention relates to a piston as defined in its comprehensive definition given in the Preamble above. According to this aspect of the present invention, all or part of the flow path cross-section of the seal is non-uniform in the longitudinal direction of the piston. As an alternative or addition to the above option, all or part of the stage has a non-uniform volume in the longitudinal direction of the piston.
[0012] By providing inter-seal stages having non-uniform flow path cross-sections and / or non-uniform volumes in the longitudinal direction of the piston, the present invention offers the possibility of better control over the pressure and pressure difference to which each of the seals, particularly the distal seal and the proximal seal, is subjected. The present invention therefore provides a method for standardizing the pressure difference in various inter-seal stages.
[0013] The two options of the solution proposed by the present invention, namely a non-uniform flow channel cross-section or a non-uniform stage volume, contribute individually or in combination to the same technical effect 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, each of which is positioned to hold a seal. - The seal includes a portion that protrudes radially from the piston body. - The channel cross-section is formed in the radially protruding portion. - The flow path cross-section of the piston's central seal is smaller than the flow path cross-section of the piston's proximal seal. - The flow path cross-section of the piston's central seal is smaller than the flow path cross-section of the piston's distal seal. - The channel cross-section of the distal seal is larger than the channel cross-section of the proximal seal. - The cross-sectional shape of the seal's flow path changes longitudinally, with a decreasing profile followed by an increasing profile. - The flow path cross-sections of the two consecutive seals are positioned at an angle to each other with respect to the longitudinal direction. - The volume of the central stage is larger than the volume of the proximal stage. - The volume of the central stage is larger than the volume of the distal stage. - The stage volume changes in the longitudinal direction, with an increasing profile followed by a decreasing profile. - All or part of the stage has uneven heights in the longitudinal direction. - The profile of the change in stage volume is similar to the profile of the change in stage height. - The piston includes a series of peripheral grooves formed along its body within the stage. - All or part of the groove has a depth defined along the radial direction of the piston. - The groove depth is non-uniform in the longitudinal direction. - The profile of the change in stage volume in the longitudinal direction is similar to the profile of the change in groove depth in the longitudinal direction.
[0015] According to a second aspect, the present invention relates to a machine for cryogenic or high-pressure fluids, including a sleeve and a piston as described according to any one of the embodiments described above.
[0016] Further specific features and advantages will become apparent by reading the following description provided with reference to the following drawings.
Brief Description of the Drawings
[0017] [Figure 1] Figure 1 is a longitudinal cross-sectional view showing a first embodiment of a machine according to the present invention, the machine including a sleeve, a piston, and a seal defining a range of a uniform stage. [Figure 2] Figure 2 is a front view showing a first example of a piston of a machine according to the first embodiment, the piston including a seal having a non-uniform flow path cross-section. [Figure 3] Figure 3 is a front view showing a second example of a piston of a machine according to the first embodiment, the piston further including a first type of annular groove. [Figure 4] Figure 4 is an isometric cross-sectional view showing a third example of a piston of a machine according to the first embodiment, the piston including a second type of annular groove. [Figure 5] Figure 5 is a longitudinal cross-sectional view showing a second embodiment of a machine according to the present invention, the machine including a sleeve, a piston, and a seal defining a range of a non-uniform stage. [Figure 6] Figure 6 is a graph showing a first example of a change in a flow coefficient related to a flow path cross-section of a seal with respect to the first embodiment of the machine. [Figure 7] Figure 7 is a graph showing a second example of a change in a flow coefficient related to a flow path cross-section of a seal with respect to the first embodiment of the machine. [Figure 8] Figure 8 is a graph showing a second example of a change in a flow coefficient related to a flow path cross-section of a seal with respect to the first embodiment of the machine. [Figure 9] Figure 9 is a graph showing an example of a change in an internal stage distance with respect to the second embodiment of the machine.
Modes for Carrying Out the Invention
[0018] As shown in Figures 1 and 5, the present invention relates to a fluid machine 1. The fluid machine 1 may be a pump or a compressor. The fluid in question may be hydrogen under cryogenic or high pressure conditions (20 bar to 400 bar or higher).
[0019] Machine 1 includes a sleeve 2 and a piston 3, at least partially positioned inside the sleeve 2. The sleeve 2 and piston 3 are mounted so that they can move relative to each other in a translational manner along the longitudinal direction X of machine 1. To do this, either the sleeve 2 or the piston 3 is connected to an actuator (not shown).
[0020] In the case of a piston 3 connected to an actuator, the piston 3 may include a head 31 (or body) located within the sleeve 2 and an arm 32 extending outside the sleeve 2. The arm 32 is connected to the actuator.
[0021] The sleeve 2 and piston 3 (specifically the head 31 of the piston 3) form a chamber 4 for compressing or pumping fluid. The sleeve 2 includes at least one inlet opening and at least one outlet opening for the fluid to enter and exit the chamber 4. The inlet and outlet openings are not shown.
[0022] The machine 1 includes a plurality of seals 5 to ensure that the chamber 4 is securely sealed during fluid compression or pumping.
[0023] The seal 5 is fastened to the wall of the piston 3, specifically to the wall of the piston head 31. Specifically, the seal 5 is arranged in series along the piston head 31 around the piston head 31. The seal 5 is therefore configured to contact the inner wall of the sleeve 2.
[0024] Furthermore, the seal 5, together with the walls of the piston 3 and the sleeve 2, defines a continuous stage 6. These stages 6 communicate with each other and with the chamber 4 through a flow channel cross-section 51 provided in the seal 5. The stages 6 thus form a reservoir for storing fluid.
[0025] Seal 5 is said to be non-airtight due to the presence of the flow path cross-section 51.
[0026] The flow channel cross-section 51 may be formed by the opening in the annular seal 5 and / or the gap between the two ends of the release ring seal.
[0027] Furthermore, the flow channel cross-sections 51 of the two consecutive seals are preferably offset from each other at an angle with respect to the longitudinal direction X of the machine 1. Advantageously, this angular offset is, for example, 180°.
[0028] Finally, each channel cross-section 51 is related to the head loss coefficient. The product of the channel cross-section 51 and the head loss coefficient is called the flow coefficient.
[0029] In the following, one of the seals 5 located in the center of the head 31 of the piston 3 is 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 pressurizing chamber 4 is 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 pressurizing chamber 4 is referred to as the "distal seal 5c".
[0030] Furthermore, one of the stages 6 located in the center of the piston 3 is called the "central stage 6a". The stage intended to be closest to the compression or pumping chamber 4 is called the "proximal stage 6b". The stage intended to be furthest from the compression or pumping chamber 4 is called the "distal stage 6c".
[0031] According to the present invention, all or part of the flow channel cross-section 51 of the seal is non-uniform along the piston 3 (or the head 31 of the piston 3). In a modified form, or in addition, all or part of the stage 6 is non-uniform along the piston 3 (or the head 31 of the piston 3).
[0032] A "non-uniform" channel cross-section is understood to mean a channel cross-section that does not all have the same size (or dimensions).
[0033] Advantageously, as is clearly shown by Figures 2 and 3 with respect to a first embodiment of machine 1, at least one central seal 5a has a flow channel cross-section 51 that is smaller than the flow channel cross-section 51 of the proximal seal 5b and smaller than the flow channel cross-section 51 of the distal seal 5c.
[0034] Advantageously, the flow path cross-section 51 of the seal 5 changes along the piston 3 (more specifically along the head 31 of the piston 3), with a decreasing profile from the proximal seal 5b to the central seal 5a, followed by an increasing profile from the central seal 5a to the distal seal 5c.
[0035] Please note that the channel cross-section 51 of the distal seal 5c may be larger than the channel cross-section 51 of the proximal seal 5b.
[0036] Similar to the flow path cross-section, the flow coefficient changes along the piston 3 (more specifically along the head 31 of the piston 3), with a decreasing profile from the proximal seal 5b to the central seal 5a, followed by an increasing profile from the central seal 5a to the distal seal 5c. Figures 6 and 7, respectively, provide examples of the change in the flow coefficient along the head 31 of the piston 3.
[0037] Specifically, in Figure 6, the flow coefficient change profile is symmetrical with respect to the central seal 5a. In contrast, in Figure 7, this profile is asymmetrical because the flow channel cross-section 51 of the distal seal 5c is much larger than the flow channel cross-section 51 of the proximal seal 5b.
[0038] For a piston 3 containing N seals, the change in the flow coefficient K(i) along the longitudinal direction of the machine 1 can be given by the following function:
number
[0039] It should be noted that the flow coefficient K(N) associated with the flow channel cross-section 51 of the distal seal 5c can be assumed to be greater than the value provided by the function K(i) above. This value may be within the following range: K(N)=(1+F A )CA≦K(N)≦3(1+F A )CA
[0040] By providing a change in the flow coefficient (and the flow path cross-section of the seal) due to a sine function such as the sine function described above, and by fixing the flow path cross-section of the distal seal 5c within the above range, the present invention makes it possible to accelerate the filling of the first and final stages 6 of machine 1.
[0041] Accordingly, the present invention makes it possible to reduce the pressure difference to which the first seal and the last seal are subjected and to limit the time that these seals are exposed to sonic conditions. This results in an improved service life of the first seal and the last seal and a reduced risk of leakage through these seals.
[0042] The flow coefficient changes along the piston 3 (more specifically along the head 31 of the piston 3), and the profile may increase from the proximal seal 5b to the distal seal 5c. Figure 8 illustrates such a change.
[0043] For a piston 3 containing N seals, the change in the flow coefficient K(i) along the longitudinal direction of the machine 1 can therefore be given by the following function:
number
[0044] The distribution of the flow coefficient K(i) given above is valid under the following conditions.
number
[0045] Advantageously, referring again to Figure 1, the piston 3 is provided with annular slots 33 intended to receive seals 5. These slots 33 are regularly distributed along the head 31 of the piston 3. Thus, the seals 5 are also regularly distributed along the head 31 of the piston 3.
[0046] Note that in the machine 1 shown in Figure 1, the seal 5 has a portion that protrudes radially from 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 protruding portion of the adjacent seal 5.
[0047] In the example shown in Figures 3 and 4, the head 31 of the piston 3 is provided with a series of annular grooves 34. Specifically, the grooves 34 are arranged in series along the head 31 of the piston 3. The grooves 34 have a depth defined radially along the piston 3. The grooves 34 alternate with the seals 5.
[0048] Compared to the fluid machine 1 including the piston 3 as shown in Figure 3 or Figure 4, the inter-seal stage 6 has a larger volume than the machine 1 including the piston 3 as shown in Figure 2. These increased volumes allow for the storage of a larger volume of fluid within the stage 6, and thus limit the pressure and pressure difference to which the proximal seal 5b and distal seal 5c are subjected. This allows for a more uniform distribution of fluid pressure among the various seals 51.
[0049] Note that the groove 34 of piston 3 in Figure 4 is deeper than the groove 34 of piston 3 in Figure 3. Therefore, machine 1 including piston 3 in Figure 4 allows for the storage of a larger volume of fluid within the inter-seal stage 6.
[0050] Advantageously, as shown in Figure 5 with respect to a second embodiment of the fluid machine 1, 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.
[0051] Advantageously, the volume of stage 6 changes along piston 3, with the profile increasing from proximal stage 6b to central stage 6a, and then increasing from central stage 6a to distal stage 6c.
[0052] In the example shown in Figure 5, each stage 6 has a different height (distance between stages) but has an inner and outer radius that is the same as the inner and outer radii of the other stages 6. The inner and outer radii of the stages 6 are defined with respect to the longitudinal direction X of the machine 1 and relate to the walls of the piston head 31 and the sleeve 2, respectively.
[0053] Therefore, changes in the height (or distance) of Stage 6 are proportional to changes in the volume of these Stage 6 structures. As a result, changes in the height (or distance) of Stage 6 can follow a similar profile to the one described above with respect to changes in volume. Figure 9 shows the changes in the height of Stage 6.
[0054] Advantageously, the change in the height of the stage 6 along the piston 3 containing N seals can be described using the following function:
number
[0055] In unshown variants, the head 31 of the piston 3 may include grooves 34 with non-uniform radial depths along the head 31 of the piston 3, while the distance between seals remains constant along the head 31 of the piston 3. The depth of the grooves 34 may vary along the head of the piston 3 by a sine function similar to the sine function described above, in response to changes in the height of the stage 6.
Claims
1. A piston (3) for a machine (1) for cryogenic or high-pressure fluids such as liquid hydrogen, comprising a body (31) mounted inside a sleeve (2) of the fluid machine (1) so as to move back and forth therewith, and intended to form a chamber (4) for compressing or pumping the fluid together with the sleeve (2), also comprising a plurality of peripheral seals (5) arranged in series along the longitudinal direction (X) of the piston (3), wherein the seals (5) between them constitute a range of stages (6) along the longitudinal direction (X) of the piston (3). A piston (3) wherein at least two of the plurality of seals each include a flow channel cross-section (51) intended to allow the fluid to flow between the stages (6), wherein all or part of the flow channel cross-section (51) is non-uniform in the longitudinal direction (X), and the flow channel cross-section (51) of the central seal (5a) of the piston (3) is smaller than the flow channel cross-section (51) of the proximal seal (5b) of the piston (3), and is smaller than the flow channel cross-section (51) of the distal seal (5c) of the piston (3).
2. The piston (3) according to claim 1, wherein the body (31) of the piston (3) includes a series of peripheral slots (33) in which the seals (5) are each disposed, the seals (5) include a portion that protrudes radially from the body (31) of the piston (3), and the flow path cross section (51) is formed on the radially protruding portion.
3. The piston (3) according to claim 1 or 2, characterized in that the flow channel cross-section (51) of the distal seal (5c) is larger than the flow channel cross-section (51) of the proximal seal (5b).
4. The piston (3) according to any one of claims 1 to 3, characterized in that the flow path cross-section (51) of the seal (5) changes in the longitudinal direction (X), with a decreasing profile followed by an increasing profile.
5. The piston (3) according to any one of claims 1 to 4, characterized in that the flow path cross-sections (51) of two consecutive seals (5) are arranged at an angle to each other with respect to the longitudinal direction (X).
6. The piston (3) according to any one of claims 1 to 5, characterized in that all or part of the stage (6) has a non-uniform volume in the longitudinal direction (X).
7. The piston (3) according to claim 6, characterized in that the volume of the central stage (6a) is greater than the volume of the proximal stage (6b) and greater than the volume of the distal stage (6c).
8. The piston (3) according to claim 6 or 7, characterized in that the volume of the stage (6) changes in the longitudinal direction (X), with an increasing profile followed by a decreasing profile.
9. The piston (3) according to claim 8, characterized in that all or part of the stage (6) has a non-uniform height in the longitudinal direction (X), and the volume change profile of the stage (6) is the same as the height change profile of the stage (6).
10. The piston (3) according to any one of claims 1 to 9, characterized in that the body (31) of the piston (3) includes a series of peripheral grooves (34) formed along the body (31) within the stage (6).
11. The piston (3) according to claim 10, characterized in that all or part of the groove (34) has a depth defined along the radial direction of the piston (3), and the depth is non-uniform in the longitudinal direction (X).
12. The piston (3) according to claim 6 or 11, characterized in that it has a volume change profile of the stage (6) in the longitudinal direction (X) that is similar to the depth change profile of the groove (34) in the longitudinal direction (X).
13. A machine (1) for cryogenic or high-pressure fluids such as liquid hydrogen, comprising a piston (3) and a sleeve (2) as described in any one of claims 1 to 12, wherein the piston (3) is mounted so as to be movable inside the sleeve (2).