Cylinder of optimized geometry for supercooling, for a cryogenic pump

Abstract

The invention relates to a piston pump (1) for liquefied gases, the pump (1) comprising: - a body (20) comprising an inner casing (20') and an outer casing (20'') delimiting between them an insulation space, the inner casing (20') delimiting an inner volume (3) forming a degassing chamber at least partially accommodating a compression and delivery assembly (30) comprising a piston (32) and a pump cylinder (31), the piston (32) and the pump cylinder (31) being partially accommodated in the inner casing (20'), such that segments (32A) of the piston (32) are accommodated in the degassing chamber (3), the portion of the pump cylinder (31) accommodated in the inner volume (3) comprising a section (40) extending radially into the inner volume (3), the section (40) comprising at least one fin (44) configured to dissipate heat given off by the segments (32A).

Description

Cylinder with optimized geometry for supercooling, for cryogenic pump

[0001] The invention relates to the technical field of cryogenic pumps applicable to liquefied gases at very low temperatures, such as hydrogen. STATE OF THE ART

[0002] A piston pump essentially consists of a pump cylinder with a cylinder liner and a compression chamber, a pump piston which is guided linearly in the cylinder liner, an inlet valve disposed in an inlet area of ​​the compression chamber and used for the admission of the cryogenic fluid, and an outlet valve disposed in an outlet area of ​​the compression chamber and used for the discharge of the cryogenic fluid.

[0003] The pump piston is designed to move alternately within the cylinder liner to perform the pumping process and to form or enlarge and reduce the compression chamber by the alternating movement of the pump piston.

[0004] More specifically, during the movement of this piston, the fluid is alternately pulled from the suction side towards the compression chamber, then compressed to be discharged via a dedicated opening.

[0005] Most piston pumps have a vent on the suction side. However, the cooling of the suction area is not optimal because the heat generated in the cylinder is carried to the suction chamber and then expelled through the vent outlet, causing the fluid in the suction chamber to heat up. This process is generally not a problem when using common cryogenic fluids down to -196°C, such as nitrogen, but with a cryogenic fluid like hydrogen, which has a melting point around -255°C, the pump can cavitate or lose its prime due to insufficient cooling.

[0006] The present invention aims to provide a solution to the technical problems described above by proposing a piston pump for cryogenic fluid that limits its heating.

[0007] To this end, a piston pump for liquefied gases extending along a main axis, such as hydrogen, is proposed, said pump comprising:

[0008] - a body comprising an inner shell and an outer shell delimiting between them an insulating space that can be evacuated to thermally insulate the inner shell,

[0009] - the inner casing extending along the main axis between a first end and a second end and delimiting an internal volume forming a degassing chamber housing at least in part a compression and discharge assembly comprising a pump piston and a pump cylinder intended to guide the pump piston,

[0010] - the pump piston and pump cylinder being at least partially housed within the inner casing, such that segments of the pump piston are arranged along the main axis between said first end and said second end,

[0011] - the portion of the pump cylinder arranged along the main axis between said first end and said second end comprises a section extending radially with respect to the main axis within said internal volume,

[0012] said section comprising at least one fin configured to allow the dissipation of heat released by the segments,

[0013] said fin comprising a plurality of through openings provided to increase the exchange surface of the fin with a cryogenic liquid contained in the degassing chamber.

[0014] According to one embodiment of the invention, the plurality of through openings has an oblong shape.

[0015] According to one embodiment, the plurality of through openings has a circular shape.

[0016] According to one embodiment, the plurality of openings represents at least 10% of the total surface area of ​​a fin, advantageously at least 20% of the total surface area of ​​a fin.

[0017] According to one embodiment of the invention, the fins have a length extending along the main axis between the first end and the second end of the degassing chamber.

[0018] Advantageously, the fins have a length at least equal to 50% of the axial length of the degassing chamber.

[0019] According to one embodiment, said section comprises a plurality of fins.

[0020] According to one embodiment, said section is arranged opposite the segments of the pump piston.

[0021] According to one embodiment, the fin(s) have a thickness that decreases radially from said section.

[0022] According to one embodiment, the fin(s) extend radially to be in contact with the inner casing.

[0023] According to one embodiment, the fin(s) has a length along the main axis extending between a first point and a second point, at least a part of the segments being configured to be arranged along the main axis between said first point and said second point during the stroke of the piston.

[0024] According to one embodiment, the fin(s) have a star-shaped configuration.

[0025] According to one embodiment, said body includes a degassing outlet provided for evacuating gases that may result from the heating of the fluid that may be produced in said degassing chamber.

[0026] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for which reference should be made to the accompanying drawings. It will be understood that the invention is described in relation to a specific, non-limiting piston pump configuration.

[0027] This represents a perspective view of a piston pump for liquefied gases.

[0028] Lare represents a partial cross-sectional view of the piston pump shown at ladont whose pump cylinder has an optimized shape.

[0029] This represents a perspective view of the pump cylinder.

[0030] Lare represents a different configuration of the pump cylinder.

[0031] Lare represents another different configuration of the pump cylinder.

[0032] Figures 1 and 2 show a piston pump 1 for liquefied gases, such as hydrogen. The piston pump 1 extends along a main axis A and comprises an inlet body 10 for supplying fluid to the pump 1 and an outlet body 20 for compressing and discharging the fluid.

[0033] The inlet body 10 of the piston pump 1 includes a fluid inlet 10A intended to be connected to an external fluid supply tank and a discharge outlet 10B of excess fluid intended to be connected, preferably, to the same supply tank.

[0034] The outlet body 20 of the piston pump 1 includes a degassing outlet 20A and a fluid outlet 20B. As will be described in more detail later, the outlet body 20 of the piston pump 1 includes a pump cylinder 31 linearly guiding a pump piston 32. The linear movement of the pump piston 32 is actuated by means of an actuating rod 33 connected to the pump piston 32 from a control inlet 20C provided on the outlet body 20.

[0035] The excess fluid discharge outlet 10B is intended to return to the reservoir the excess fluid not used for cooling piston pump 1.

[0036] The degassing outlet 20A is intended to evacuate gases that may result from the heating of the fluid that may be produced in the outlet body 20.

[0037] With reference to the diagram, a cross-sectional view of the inside of piston pump 1 has been shown.

[0038] The inlet body 10 comprises an inner envelope 10' and an outer envelope 10'' delimiting between them an insulation space which can be evacuated to thermally insulate its inner envelope.

[0039] The inner casing 10' of the inlet body 10 is connected to the fluid inlet 10A of the piston pump 1.

[0040] The outlet body 20 comprises an inner envelope 20' and an outer envelope 20'' also delimiting between them an insulation space which can be evacuated to thermally insulate its inner envelope 20'.

[0041] Advantageously, an insulating material, in particular a multilayer insulator, can be arranged in the insulation space of the inlet body 10 or the outlet body 20.

[0042] The inner casing 20' of the outlet body 20 is connected to the fluid outlet 20B and degassing of the piston pump 1 and it partially houses a compression and discharge assembly 30.

[0043] The compression and discharge assembly 30 includes the pump cylinder 31 in which the previously introduced pump piston 32 slides.

[0044] More specifically, the compression and discharge assembly 30 includes, among other things:

[0045] - the pump cylinder 31, a pump sleeve 34 and an inlet valve 35, joined and coaxial,

[0046] - a pump piston 32 movable axially in the sleeve 34 forming a fluid compression chamber with the inlet valve 35.

[0047] The pump cylinder 31 houses the pump sleeve 34, within which the pump piston 32 can slide alternately between a position forming the fluid-filled compression chamber and a compression position where the compression chamber is emptied of fluid. Figure 32 illustrates the compression position of the pump piston 32.

[0048] An opening 34B is provided at the level of segments 34A of the sleeve 34 to allow leaks to be evacuated at the level of these segments 34A.

[0049] The pump cylinder 31 is associated with the inlet valve 35 (partially shown) located in the suction chamber 2 and used for the admission of the fluid, and an outlet valve (not shown) located in the fluid outlet 20B used for the discharge of the pressurized fluid.

[0050] The inner envelope 20' of the outlet body 20 delimits a volume separated into two distinct chambers 2, 3, namely a suction chamber 2 at a so-called suction pressure and an internal volume 3 forming a degassing chamber 3 at a so-called degassing pressure.

[0051] The internal volume 3 forming a degassing chamber 3 extends along the main axis A between a first end A1 and a second end A2.

[0052] The degassing outlet 20A is fluidly connected to the degassing chamber 3.

[0053] Fluid inlet 10A is fluidically connected to suction chamber 2.

[0054] The fluid in the degassing chamber 3 can be heated primarily due to friction generated by the movement of the piston rings 32A of the piston 32 relative to the pump liner 34 and by compression. This heating of the fluid leads to its evaporation as a gas in the degassing chamber 3. The degassing outlet 20A is provided to evacuate this gas in order to optimize the cooling of the compression and discharge assembly 30.

[0055] As will be described below, the shape of the cylinder has been optimized to further optimize the dissipation of heat accumulated by the fluid in the degassing chamber (i.e. the internal volume 3) and thus optimize the cooling of the liner 34.

[0056] As shown, at least a portion of the pump cylinder 31 and at least a portion of the pump 32 are arranged in the pump 1 along the main axis A between said first end A1 and said second end A2.

[0057] This part of the pump 32 includes segments 32A. The movement of the pump 32 is designed to allow the filling of a compression chamber. Without being limited to this, regardless of the stroke of the piston 32, the segments 32A are arranged in the pump 1 along the main axis A between said first end A1 and said second end A2.

[0058] The movement of the piston 32 leads to a heating of the fluid present in the degassing chamber 3 due mainly to the friction generated by the movement of the piston rings 32A of the piston 32 relative to a pump liner 34 and by compression.

[0059] To permit the dissipation of heat accumulating at the pump cylinder 31, piston 32 and liner 34 and transferred by thermal dissipation to the fluid, at least a portion of the pump cylinder 31 arranged in the pump 1 along the main axis A between said first end A1 and said second end A2, comprises a section 40 which extends radially into the internal volume 3 by at least one fin 44.

[0060] As shown in the figure, this section 40 of the pump cylinder 31 comprises a plurality of vanes 44 which extend radially from the pump cylinder 31, in a star configuration.

[0061] The fins 44 extend radially and come into contact with the inner shell 20', presenting the largest possible surface area, so that the heat accumulated by the fins 44 can be transferred to the fluid from the body of the pump cylinder 31 to this inner shell 20'.

[0062] In one configuration, the inner casing 20' and the aforementioned part of the piston cylinder 31 are made from a single piece. This optimizes heat dissipation performance.

[0063] Advantageously, the fins 44 have a flared shape, decreasing from the cylinder body 31 towards the inner shell 20'. Such a shape facilitates the radial dissipation of heat from the cylinder body.

[0064] The fins 44 advantageously have a length extending along the main axis A between a first point P1 and a second point P2.

[0065] It will be understood that at least a portion of the segments 32A are configured to be positioned along the main axis A between said first point P1 and said second point P2 throughout the entire stroke of the piston 32, or preferably a majority of the stroke of the piston 32, so that the heat resulting from the friction of the piston 32 in the cylinder liner 34 can be dissipated into the fluid via the fins 44 thus formed. Preferably, the length of the fins 44 is between 30 and 150 millimeters.

[0066] As shown in the figure, section 40 is positioned opposite the segments 32A of the pump piston 32. Preferably, section 40 is configured to be opposite the segments 32A of the piston 32 throughout the entire stroke of the piston 32. This ensures that the heat transfer from the segments 32A to section 40 of the pump cylinder 31 is optimized.

[0067] According to another embodiment, illustrated in the figure, the section 40 of the pump cylinder 31 comprises a plurality of fins 44 of generally rectilinear shape extending radially from the cylinder 31 towards the inner shell 20', in the internal volume 3 forming the degassing chamber.

[0068] Advantageously, the plurality of 44' openings represents at least 10% of the total surface area of ​​a 44' fin.

[0069] Advantageously, each fin 44 comprises a plurality of oblong, through-through openings 44'. These through-through openings extend completely through each fin 44, i.e., through its thickness. These openings 44' are distributed over all or part of the surface of the fins 44, either regularly or irregularly. This configuration increases the contact area between the fins 44 and the cryogenic fluid circulating in the degassing chamber 3, thus facilitating heat exchange between the fins and the fluid. Consequently, the heat dissipation generated by the friction of the piston rings 32A is optimized.

[0070] Furthermore, the presence of openings 44' formed in the fins 44 promotes the circulation of the cryogenic fluid through the fins 44, thus preventing the formation of localized hot pockets. The overall thermal efficiency of the piston pump 1 is thereby improved, particularly under prolonged operating conditions.

[0071] According to another embodiment, illustrated in Figure 1, the fins 44 comprise a plurality of circular through-holes 44" distributed over their surface. These openings 44" can extend in one or more rows, notably in the longitudinal direction of the fin 44, or radially.

[0072] Such a configuration, like the oblong 44'' openings described in reference to the, increases the exchange surface between the cryogenic fluid and the fins 44, thus improving heat dissipation.

[0073] Advantageously, the circular shape of the 44'' openings facilitates their manufacture, in particular by conventional drilling of the 44 fins, which reduces manufacturing costs and optimizes the industrial reproducibility of the piston pump 1.

[0074] Moreover, in the configuration illustrated in figures 4 and 5, the fins 44 have an increased axial length, so that they extend substantially over the length of the internal volume 3 forming the degassing chamber, that is to say between the first end A1 and the second end A2 of the internal envelope 20'.

[0075] Such an arrangement maximizes the heat exchange surface between the fins and the cryogenic fluid present in the degassing chamber 3 over the entire fluid path, which significantly improves the cooling capacity of the compression and discharge assembly 30. This also makes it possible to maintain a more constant low temperature over the entire stroke of the piston 32, even in prolonged phases of operation.

[0076] This arrangement can be combined with the presence of circular or oblong through openings, as described previously, to further increase heat dissipation.

[0077] Although this description refers to specific embodiments, modifications may be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the various embodiments illustrated or mentioned may be combined in additional embodiments. Therefore, the description and drawings should be considered illustrative rather than restrictive.

Claims

Piston pump (1) for liquefied gases extending along a main axis (A), such as hydrogen, said pump (1) comprising: - a body (20) comprising an inner casing (20') and an outer casing (20'') delimiting between them an insulation space that can be evacuated to thermally insulate the inner casing (20'), the inner casing (20') extending along the main axis (A) between a first end (A1) and a second end (A2) and delimiting an internal volume (3) forming a degassing chamber housing at least in part a compression and discharge assembly (30) comprising a pump piston (32) and a pump cylinder (31) provided to guide the pump piston (32), the pump piston (32) and the pump cylinder (31) being at least partially housed in the inner casing (20'),such that segments (32A) of the pump piston (32) are arranged along the main axis (A) between said first end (A1) and said second end (A2), the portion of the pump cylinder (31) arranged along the main axis (A) between said first end (A1) and said second end (A2) comprises a section (40) extending radially with respect to the main axis within said internal volume (3), said section (40) comprising at least one fin (44) configured to permit the dissipation of heat released by the segments (32A), said fin (44) comprising a plurality of through openings (44', 44'') provided to increase the exchange surface of the fin (44) with a cryogenic liquid contained in the degassing chamber. Piston pump (1) according to the preceding claim, wherein the openings are oblong in shape, alternatively circular in shape. Piston pump (1) according to the preceding claim, wherein said section (40) is arranged opposite the segments (32A) of the pump piston (32). Piston pump (1) according to any one of the preceding claims, wherein said section (40) comprises a plurality of vanes (44). Piston pump (1) according to the preceding claim, in which the vane(s) (44) have a thickness that decreases radially from said section (40). Piston pump (1) according to any one of claims 2 or 3, wherein the vane(s) (44) extend radially to be in contact with the inner casing (20'). Piston pump (1) according to any one of claims 2 to 5, wherein the vane(s) (44) has a length along the main axis (A) extending between a first point (P1) and a second point (P2), at least a portion of the segments (32) being configured to be arranged along the main axis between said first point (P1) and said second point (P2) during the stroke of the piston (32). Piston pump (1) according to any one of claims 2 to 6, wherein the vane(s) (44) have a star configuration. Piston pump (1) according to any one of the preceding claims, wherein said body (20) includes a degassing outlet (20A) provided to evacuate gases that may result from the heating of the fluid that may be produced in said degassing chamber.

Images