Piston for a machine for a fluid such as hydrogen, and machine for a fluid comprising such a piston

Abstract

The invention relates to a piston (3) for a machine (1) for a cryogenic fluid or a fluid under high pressure, such as liquid hydrogen, the piston (3) comprising a body (31) intended to be mounted inside a sleeve (2) of the machine (1) for a fluid in a reciprocating relative movement, and to form, with the sleeve (2), a chamber (4) for compressing or pumping the fluid, the piston (3) also comprising a plurality of peripheral sealing gaskets (5) arranged in series in a longitudinal direction (X) of the piston (3), the gaskets (5) delimiting therebetween stages (6) in the longitudinal direction (X) of the piston (3), at least two of the plurality of gaskets (5) each comprising a flow section (51) intended to allow the fluid to flow between the stages (6), characterised in that all or some of the stages (6) have non-uniform volumes in the longitudinal direction (X).

Description

Piston for a fluid machine, such as hydrogen, and fluid machine comprising such a piston

[0001] The invention relates to a piston for a fluid machine. The invention also relates to a fluid machine comprising such a piston.

[0002] The fluid machine can be a pump or a compressor. The fluid considered can be liquid hydrogen in a cryogenic state or under high pressure.

[0003] A fluid machine comprises a jacket and a piston which are mounted to move relative to each other.

[0004] In particular, the piston comprises a body intended to be mounted inside the liner in a relative reciprocating movement, the body being intended to form with the liner a compression or pumping chamber for the fluid. In addition, the piston comprises a plurality of peripheral seals arranged in series along a longitudinal direction of the piston.

[0005] The joints define between them volumes called stages. At least two of the plurality of joints each comprise a passage section intended to allow fluid flow between the stages.

[0006] In a fluid machine as described above, the flow of fluid through the passage sections of the seals is designed to reduce the pressure difference recorded on either side of the seal closest to the compression chamber (called the proximal seal), and thus to preserve the mechanical strength of this seal.

[0007] However, the pressure difference recorded at the seal furthest from the compression chamber (called the distal seal) remains very significant. This distal seal is then exposed to a so-called sonic state in which the fluid flow rate through its passage section depends mainly on the upstream fluid pressure. Prolonged exposure of the distal seal to the sonic state affects its mechanical strength and increases the risk of premature failure.

[0008] This results in a risk of leaks in the fluid machine.

[0009] In the case of cryogenic fluid, leaks due to a rupture of the distal seal (or any other seal) cause unwanted vaporization and heating of this fluid. Such vaporization (also called boil-off) represents a loss of fluid in addition to that caused by a seal defect.

[0010] Therefore, there appears to be a need to develop a piston for a fluid machine and a fluid machine which at least partially overcome the disadvantages listed above.

[0011] To this end, according to a first aspect, the invention relates to a piston conforming to the generic definition given in the preamble above. According to this aspect of the invention, all or part of the passage sections of the seals are non-uniform along the longitudinal direction of the piston. Alternatively or in addition to the above option, all or part of the stages have non-uniform volumes along the longitudinal direction of the piston.

[0012] By providing non-uniform passage sections and / or inter-seal stages with non-uniform volumes along the longitudinal direction of the piston, the invention opens up the possibility of better controlling the pressure and the pressure difference to which each of the seals is exposed, and in particular the distal seal and the proximal seal. The invention thus opens the way to standardizing the pressure difference at the level of the different inter-seal stages.

[0013] Both options of the solution proposed by the invention, namely non-uniform passage sections or non-uniform floor volumes, each contribute or in combination to the same technical effects above.

[0014] Embodiments of the invention may comprise one or more of the following features:- the piston body comprises a series of peripheral grooves in which the seals are respectively arranged;- the seals comprise portions projecting radially relative to the piston body;- the passage sections are formed at the radially projecting portions;- the passage section of a middle seal of the piston is smaller than the passage section of a proximal seal of the piston;- the passage section of the middle seal of the piston is smaller than the passage section of a distal seal of the piston;- the passage section of the distal seal is larger than the passage section of the proximal seal;- the passage section of the seals varies in the longitudinal direction according to a decreasing profile then an increasing profile;- the passage sections of two successive seals are arranged with an angular offset relative to each other around the longitudinal direction;- the volume of a middle stage is greater than the volume of a proximal stage;- the volume of a middle stage is greater than the volume of a distal stage;- the volume of the stages varies in the longitudinal direction according to an increasing profile then a decreasing profile;- all or part of the stages have a non-uniform height in the longitudinal direction;- the variation profile of the volume of the stages is similar to a variation profile of the height of the stages;- the piston comprises a series of peripheral grooves formed along the body, in the stages;- all or part of the grooves have a depth defined in a radial direction of the piston;- the depth of the grooves is non-uniform in the longitudinal direction;- the variation profile of the volume of the floors in the longitudinal direction is similar to a variation profile of the depth of the grooves in the longitudinal direction.;

[0015] According to a second aspect, the invention relates to a cryogenic or high pressure fluid machine, comprising a jacket and a piston described according to any one of the embodiments above.

[0016] Other features and advantages will appear on reading the description below, made with reference to the following figures in which:

[0017] is a longitudinal sectional view illustrating a first embodiment of the machine according to the invention, the machine comprising a sleeve, a piston and seals delimiting uniform stages;

[0018] is a front view showing a first example of a piston of the machine according to the first embodiment, the piston being provided with seals having non-uniform passage sections;

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

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

[0021] is a longitudinal sectional view illustrating a second embodiment of the machine according to the invention, the machine comprising a sleeve, a piston and seals delimiting non-uniform stages;

[0022] is a graph illustrating, in relation to the first embodiment of the machine, a first example of variation of a flow coefficient associated with the passage sections of the joints;

[0023] is a graph illustrating, in relation to the first embodiment of the machine, a second example of variation of the flow coefficient associated with the passage sections of the joints;

[0024] is a graph illustrating, in relation to the first embodiment of the machine, a second example of variation of the flow coefficient associated with the passage sections of the joints;

[0025] is a graph illustrating, in relation to the second embodiment of the machine, an example of variation of the inter-stage distance.

[0026] As illustrated in Figures 1 and 5, the invention relates to a fluid machine 1. It may be a pump or a compressor. The fluid concerned may be hydrogen in a cryogenic state or under high pressure (20 bar to 400 bar or more).

[0027] The machine 1 comprises a sleeve 2 and a piston 3 arranged at least partly inside the sleeve 2. The sleeve 2 and the piston 3 are mounted to move in relative translation relative to each other along a longitudinal axis X of the machine 1. To do this, one between the sleeve 2 and the piston 3 is connected to an actuator (not shown).

[0028] In the case of a piston 3 connected to the actuator, the piston 3 may comprise a head 31 (or a body) which is arranged in the sleeve 2, as well as an arm 32 which extends outside the sleeve 2. The arm 32 is connected to the actuator.

[0029] The sleeve 2 and the piston 3 (and in particular the head 31 of the piston 3) form a chamber 4 for compressing or pumping the fluid. The sleeve 2 comprises at least one inlet port and at least one outlet port for discharging the fluid into or out of the chamber 4. The inlet and outlet ports are not illustrated.

[0030] In order to ensure sealing of the chamber 4 during a phase of compression or pumping of the fluid, the machine 1 comprises a plurality of sealing joints 5.

[0031] The sealing gaskets 5 are fixed to a wall of the piston 3, and in particular to a wall of the head 31 of the piston 3. In particular, the sealing gaskets 5 are arranged around the head 31 of the piston 3, and in series along the head 31 of the piston 3. The gaskets 5 are thus configured to be in contact with an internal wall of the liner 2.

[0032] Furthermore, the sealing joints 5 define with a wall of the piston 3 and a wall of the jacket 2 successive stages 6. These stages 6 communicate with each other, and communicate with the chamber 4 thanks to passage sections 51 provided at the level of the joints 5. The stages 6 thus form fluid storage reservoirs.

[0033] The joints 5 are said to be leaking due to the presence of the passage sections 51.

[0034] The passage sections 51 may be formed by orifices in annular seals 5 and / or gaps between two ends of open ring seals.

[0035] Furthermore, the passage sections 51 of two successive joints are preferably angularly offset from each other around the longitudinal axis X of the machine 1. Advantageously, this angular offset is for example 180°.

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

[0037] Subsequently, one of the seals 5 positioned at a central portion of the head 31 of the piston 3 will be called a “central seal 5a”. A seal located at a first end of the piston 3 and intended to be closest to the compression or pumping chamber 4 will be called a “proximal seal 5b”. Finally, a seal located at a second end of the piston 3 and intended to be furthest from the compression or pumping chamber 4 will be called a “distal seal 5c”.

[0038] Furthermore, one of the stages 6 located at the central portion of the piston 3 will be called "central stage 6a". The stage intended to be closest to the compression or pumping chamber 4 will be called "proximal stage 6b". The stage intended to be furthest from the compression or pumping chamber 4 will be called "distal stage 6c".

[0039] According to the invention, all or part of the passage sections 51 of the seals are non-uniform along the piston 3 (or the head 31 of the piston 3). Alternatively or in addition, all or part of the stages 6 have non-uniform volumes along the piston 3 (or the head 31 of the piston 3).

[0040] By "non-uniform" passage sections we mean passage sections that are not all the same size (or dimensions).

[0041] Advantageously, as better illustrated in la and in la in relation to the first embodiment of the machine 1, at least one central seal 5a has a passage section 51 smaller than the passage section 51 of the proximal seal 5b, and smaller than the passage section 51 of the distal seal 5c.

[0042] Advantageously, the section 51 of passage of the seals 5 varies along the piston 3 (and more specifically along the head 31 of the piston 3) according to a decreasing profile from the proximal seal 5b to the central seal 5a, then according to an increasing profile from the central seal 5a to the distal seal 5c.

[0043] It should be noted that the passage section 51 of the distal seal 5c may be greater than the passage section 51 of the proximal seal 5b.

[0044] Like the passage section, the flow coefficient varies along the piston 3 (and more specifically along the head 31 of the piston 3) according to a decreasing profile from the proximal seal 5b to the central seal 5a, then according to an increasing profile from the central seal 5a to the distal seal 5c. Laet laeach give an example of variation of the flow coefficient along the head 31 of the piston 3.

[0045] In particular, at 1a, the variation profile of the flow coefficient is symmetrical with respect to the central seal 5a. On the other hand, at 1a, this profile becomes asymmetrical due to a passage section 51 of the distal seal 5c which is significantly greater than that of the proximal seal 5b.

[0046] [Corrected according to rule 26, 10.10.2024]For a piston 3 comprising N seals, the evolution of the flow coefficient K(i) in the longitudinal direction of the machine 1 can be given by the following function: WhereC represents a reference discharge coefficient;A represents a reference passage section;the joint rank 5; and an arbitrary factor, with .

[0047] [Corrected according to rule 26, 10.10.2024]It should be noted that the flow coefficient associated with the section 51 of passage of the distal seal 5c can take a value greater than that provided by the function K(i) above. This value can be included in the interval below:

[0048] By providing for an evolution of the flow coefficient (and of the passage section of the seals) according to a sinusoidal function such as that described above, and by fixing the passage section of the distal seal 5c to a value included in the above interval, the invention makes it possible to accelerate the filling of the first and last stages 6 of the machine 1.

[0049] Thus, the invention makes it possible to reduce the pressure difference to which the first seals and last seals are exposed, and to limit the time these seals are exposed to the sonic state. This results in an improvement in the service life of the first seals and last seals and a reduction in the risk of leaks through these seals.

[0050] The flow coefficient can vary along the piston 3 (and more specifically along the head 31 of the piston 3) according to an increasing profile from the proximal seal 5b to the distal seal 5c. Illustrates such an evolution.

[0051] [Corrected according to rule 26, 10.10.2024]For a piston 3 comprising N seals, the evolution of the flow coefficient K(i) in the longitudinal direction of the machine 1 can thus be given by the following function: Or : ;e1(i'), e2(i') and F A (i') are functions that depend on the thermodynamic state of the fluid in stage i.

[0052] [Corrected according to rule 26, 10.10.2024]The distribution of the flow coefficient K(i) as given above is valid under the following condition: where: f: the piston frequency; X: a coefficient; Q(i): a function which depends on the thermodynamic state of the fluid at stage i

[0053] Advantageously, with reference again to the, the piston 3 is provided with annular grooves 33 intended to receive the sealing gaskets 5. These grooves 33 are regularly distributed along the head 31 of the piston 3. Thus, the sealing gaskets 5 are also regularly distributed along the head 31 of the piston 3.

[0054] It should be noted that on the machine 1 illustrated in the, the seals 5 have portions which extend radially projecting relative to the head 31 of the piston 3. The volume of each stage 6 of the machine 1 is delimited by a wall of the head 31 of the piston 3, a wall of the sleeve 2 as well as by projecting portions of the adjacent seals 5.

[0055] In the examples illustrated in the set, the head 31 of the piston 3 is provided with a series of annular grooves 34. In particular, the grooves 34 are arranged in series along the head 31 of the piston 3. The grooves 34 have a depth defined in the radial direction of the piston 3. The grooves 34 alternate with the seals 5.

[0056] For a fluid machine 1 comprising a piston 3 according to the or, the inter-seal stages 6 each have a larger volume compared to a machine 1 comprising a piston 3 according to the. These increased volumes make it possible to store a larger quantity of fluid at the stages 6, and thus to limit the pressure and the pressure difference to which the proximal seal 5b and the distal seal 5c are exposed. In this way, the fluid pressure can be distributed uniformly between the different sealing joints 51.

[0057] It should be noted that the grooves 34 of the piston 3 according to the are deeper than the grooves 34 of the piston 3 according to the. The machine 1 comprising the piston 3 according to the thus allows a larger quantity of fluid to be stored at the inter-joint stages 6.

[0058] Advantageously, as illustrated in relation to the second embodiment of the fluid machine 1, at least one central stage 6a has a volume greater than the volume of the proximal stage 6b, and greater than the volume of the distal stage 6c.

[0059] Advantageously, the volume of the stages 6 varies along the piston 3 according to an increasing profile from the proximal stage 6b to the central stage 6a, then according to a decreasing profile from the central stage 6a to the distal stage 6c.

[0060] In the example illustrated in , each stage 6 has a different height (inter-stage distance), but an internal radius and an external radius identical to those of the other stages 6. The internal radius and the external radius of a stage 6 are defined relative to the longitudinal axis X of the machine 1 and are associated respectively with a wall of the head 31 of the piston 3 and with a wall of the sleeve 2.

[0061] Thus, the variation in the height (or distance) of the floors 6 is proportional to the variation in the volume of these floors 6. Consequently, the variation in the height (or distance) of the floors 6 can follow a profile similar to that described above in relation to the variation in the volume. Illustrates an evolution in the height of the floors 6.

[0062] Advantageously, the variation of the height of the stages 6 along a piston 3 comprising N joints can be written using the following function: Or: represents a reference height; i represents the row of seal 5 along piston 3; and represents an arbitrary factor, with .

[0063] In a variant not shown, the head 31 of the piston 3 may comprise grooves 34 having non-uniform radial depths along the head 31 of the piston 3, while the inter-seal distance 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 following a sinusoidal function similar to that described above in relation to the variation in the height of the stages 6.

Claims

Piston (3) for a machine (1) for cryogenic or high-pressure fluid, such as liquid hydrogen, the piston (3) comprising a body (31) intended to be mounted inside a jacket (2) of the fluid machine (1) in a relative reciprocating movement, and to form with said jacket (2) a chamber (4) for compressing or pumping the fluid, the piston (3) also comprising a plurality of peripheral sealing seals (5) arranged in series in a longitudinal direction (X) of the piston (3), the seals (5) delimiting between them stages (6) in the longitudinal direction (X) of the piston (3), at least two of the plurality of seals (5) each comprising a passage section (51) intended to allow a flow of the fluid between the stages (6), characterized in that all or part of the stages (6) have non-uniform volumes in the longitudinal direction (X). Piston (3) according to the preceding claim, characterized in that the volume of a middle stage (6a) is greater than the volume of a proximal stage (6b), and greater than the volume of a distal stage (6c). Piston (3) according to any one of claims 1 or 2, characterized in that the volume of the stages (6) varies in the longitudinal direction (X) according to an increasing profile then a decreasing profile. Piston (3) according to the preceding claim, characterized in that all or part of the stages (6) have a non-uniform height in the longitudinal direction (X), the variation profile of the volume of the stages (6) being similar to a variation profile of the height of the stages (6). Piston (3) according to any one of the preceding claims, characterized in that the body (31) of the piston (3) comprises a series of peripheral grooves (34) formed along the body (31), in the stages (6). Piston (3) according to the preceding claim, characterized in that all or part of the grooves (34) have a depth defined in a radial direction of the piston (3), said depth being non-uniform in the longitudinal direction (X). Piston (3) according to claims 1 and 6, characterized in that it has a variation profile of the volume of the stages (6) in the longitudinal direction (X) similar to a variation profile of the depth of the grooves (34) in the longitudinal direction (X). Piston (3) according to any one of the preceding claims, characterized in that the body (31) of the piston (3) comprises a series of peripheral grooves (33) in which the seals (5) are respectively arranged, the seals (5) comprising portions projecting radially relative to the body (31) of the piston (3), the passage sections (51) being formed at the level of the radially projecting portions. Piston (3) according to any one of the preceding claims, characterized in that the passage section (51) of a middle seal (5a) of the piston (3) is smaller than the passage section (51) of a proximal seal (5b) of the piston (3), and smaller than the passage section (51) of a distal seal (5c) of the piston (3). Piston (3) according to the preceding claim, characterized in that the passage section (51) of the distal seal (5c) is larger than the passage section (51) of the proximal seal (5b). Piston (3) according to any one of the preceding claims, characterized in that the passage section (51) of the seals (5) varies in the longitudinal direction (X) according to a decreasing profile then an increasing profile. Piston (3) according to any one of the preceding claims, characterized in that the passage sections (51) of two successive seals (5) are arranged with an angular offset relative to each other around the longitudinal direction (X). Machine (1) for cryogenic or high-pressure fluid, such as liquid hydrogen, comprising a piston (3) according to any one of the preceding claims and a jacket (2), the piston (3) being mounted to move inside the jacket (2).

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