Degassing separation for cryogenic pump

Abstract

TITLE: Degassing Separation for Cryogenic Pump The invention relates to a piston pump (1) for liquefied gases, such as hydrogen, comprising a degassing gas separation device (4) arranged between the suction chamber (2) and the degassing chamber (3), the separation device (4) comprising a main body (40) having at least one through-passage (41) connecting the suction chamber (2) and the degassing chamber (3) and a means (42) for closing said passage, the closing means (42) being configured to: - in a closed position (P0), obstruct said passage when the degassing pressure is greater than the suction pressure, - in an open position (P1), open said through-passage (41) when the degassing pressure is less than or equal to the suction pressure. Figure for the abstract: Figure 1

Description

Title of the invention: Degassing separation for cryogenic pumps. Technical field

[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 comprises 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 outlet of the cryogenic fluid.

[0003] The pump piston is designed to move alternately in the cylinder liner in order 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 particularly, during the movement of this piston, the fluid is alternately pulled from the suction side towards the compression chamber, then compressed to be evacuated 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 its vent outlet, resulting in the fluid in the suction chamber heating up. This process is generally not a problem for use with common cryogenic fluids down to -196°C, such as nitrogen, but with a cryogenic fluid, such as 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 applicable to liquefied gases at very low temperatures.

[0007] To this end, the invention relates to a piston pump for liquefied gases, such as hydrogen, said pump comprising:

[0008] - a fluid inlet intended to be connected to a fluid supply reservoir outside the pump,

[0009] - a suction chamber for receiving the fluid from said inlet and configured to be at a pressure known as suction pressure, and

[0010] - a fluid degassing chamber communicating with a degassing outlet and configured to be at a so-called degassing pressure,

[0011] the piston pump comprising a degassing gas separation device arranged between the suction chamber and the degassing chamber,

[0012] the separation device comprising a main body having at least one through passage connecting the suction chamber and the degassing chamber and a means for closing said passage,

[0013] the shuttering means being configured for:

[0014] - in a closed position, to obstruct said passage when the pressure of Degassing is greater than the suction pressure.

[0015] - in an open position, open said passage when the degassing pressure is less than or equal to the suction pressure.

[0016] Thus, in the event of degassing in the degassing chamber, the return of hot degassing gases to the suction chamber is prevented. The heating of the suction chamber receiving the fluid is limited. During suction, the fluid contained in the suction chamber is thus protected from overheating and the risk of cavitation. Pumping the fluid is facilitated.

[0017] According to one embodiment, the piston pump includes a compression and discharge assembly comprising a piston cylinder in which a pump piston can slide, the piston cylinder forming said main body of the separation device.

[0018] Such a main body makes it easier to manufacture and assemble the piston pump.

[0019] According to one embodiment, the separation device includes a retaining ring for at least one sealing means, the retaining ring being provided to ensure a seal between the suction chamber and the degassing chamber in said sealing position.

[0020] This ensures that the chambers can be at distinct pressures, or even temperatures, at least in the said closing position.

[0021] According to one embodiment of the invention, the separation device comprises at least one housing for the sealing means comprising an opening to allow the passage of the fluid from the suction chamber to the degassing chamber in said open position, the sealing means being configured to move in said housing between said sealing position and said open position, the housing being preferably formed in the retaining ring and / or in the main body.

[0022] Such a housing advantageously allows control of the flow of the fluid in the passage depending on the arrangement of the sealing means relative to the opening of the housing.

[0023] According to one embodiment of the invention, the sealing means comprises openings.

[0024] Such openings allow the fluid to flow through the sealing means without requiring any arrangement of material in the retaining ring or in the main body of the separation device.

[0025] According to one embodiment of the invention, the sealing means has a central zone of material and peripheral zones devoid of material forming the openings, the central zone is provided to seal the opening of the housing in said sealing position and to partially seal said through passage in said opening position, and the peripheral zones are provided to allow the passage of the fluid from the suction chamber to the degassing chamber in said opening position.

[0026] The shape of the sealing device thus allows the opening of the housing to be sealed only in the sealed position. It will be understood that said opening has a diameter between the diameter of the housing opening and the diameter of the housing.

[0027] According to one embodiment of the invention, said through passage is provided to open into the degassing chamber near the degassing outlet.

[0028] Such an arrangement of the through passage makes it possible to keep this passage clear of the fluid present in the degassing chamber.

[0029] According to one embodiment of the invention, the separation device comprises a plurality of through passages each associated with a closing means.

[0030] According to one embodiment of the invention, the sealing means is made of a low-density material, such as PTFE or PCTFE, so that it can be moved between said sealing position and said opening position as a function of the suction pressure and the degassing pressure.

[0031] Such a material advantageously allows for the formation of a low-density sealing means, thereby reducing its pressure resistance. Furthermore, such a material advantageously exhibits low coefficients of friction. In addition, the shape of the sealing means limits its size within the pump volume without requiring oversizing of the pump.

[0032] According to one embodiment of the invention, the sealing means is removable.

[0033] Thus, it is possible to replace the existing sealing means having a certain density with another sealing means having a different density. In this way, Depending on the nature of the fluid to be pumped, the sealing method can be adapted to allow its movement.

[0034] Advantageously, the closing means is a valve.

[0035] 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 of the invention.

[0036] Fig. 1 represents a perspective view of a piston pump for liquefied gases.

[0037] Figure [Fig. 2] shows a partial cross-sectional view of the piston pump shown in the [Fig.1] equipped with a separation device according to the invention.

[0038] Fig. 3 represents a front cross-sectional view of Fig. 2.

[0039] Fig. 4A represents an enlargement of the separation device in an open position.

[0040] Fig. 4B represents an enlargement of the separation device in a closed position.

[0041] Figures 1 and 2 show a piston pump 1 for liquefied gases, such as hydrogen. The piston pump 1 comprises an inlet body 10 for supplying fluid to the pump 1 and an outlet body 20 for compressing and discharging the fluid.

[0042] 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.

[0043] 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 with reference to [Fig. 2], 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.

[0044] The excess fluid discharge outlet 10B is intended to return to the reservoir the excess fluid not used for cooling the piston pump 1.

[0045] The degassing outlet 20A is intended to evacuate gases that may result from heating of the fluid that may be produced in the outlet body 20.

[0046] With reference to [Fig.2], a cross-sectional view of the inside of the piston pump 1 is shown.

[0047] 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.

[0048] The inner casing 10' of the inlet body 10 is connected to the fluid inlet 10A of the piston pump 1 and includes a filter 10C through which the fluid enters.

[0049] 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'.

[0050] 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.

[0051] 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.

[0052] The compression and discharge assembly 30 includes the pump cylinder 31 in which the previously introduced pump piston 32 slides.

[0053] The pump cylinder 31 is arranged in the inner casing 20' of the outlet body 20.

[0054] 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 a degassing chamber 3 at a so-called degassing pressure.

[0055] The degassing outlet 20A is fluidly connected to the degassing chamber 3.

[0056] The fluid inlet 10A is fluidly connected to the suction chamber 2.

[0057] These chambers 2, 3 are delimited by the pump cylinder 31 mounted without play in the inner casing 20' of the outlet body 20.

[0058] As illustrated, the pump cylinder 31 comprises a cylindrical body 31A extending along a main axis A from which a circular projection 31B extends radially. The circular projection 31B is designed to cooperate without play with the inner casing 20' of the outlet body 20 in which the pump cylinder 31 is housed.

[0059] The pump cylinder 31 houses a pump sleeve 34 in which the pump piston 32 can slide alternately between a position forming a compression chamber filled with fluid and a compression position where the compression chamber is emptied of fluid through a discharge opening 34A of the sleeve 34. [Fig.2] illustrates the compression position of the pump piston 32.

[0060] The pump cylinder 31 is associated with an inlet valve 35 disposed in the suction chamber 2 and used for the admission of the fluid, and an outlet valve 36 disposed in the fluid outlet 20B used for the discharge of the pressurized fluid.

[0061] The compression and discharge assembly 30 comprises, among other things:

[0062] - the pump cylinder 31, the pump sleeve 34 and the intake valve 35, solid and coaxial,

[0063] - the pump piston 32 movable axially in the sleeve 34 forming a chamber fluid compression with the inlet valve 35,

[0064] - and the outlet valve 36.

[0065] The intake valve 35 includes an intake cylinder head 35A having a series of intake passages 35A1 connecting the compression chamber to the suction chamber 2.

[0066] Furthermore, the intake cylinder head 35A includes a fluid intake chamber 4 opening into the suction chamber 2.

[0067] The intake valve 35 includes a conical valve 35B arranged at the end of the cylinder head 35A on the side of the compression chamber. The cone of the valve 35B is designed to close the intake passages 35A1 when the compression chamber is filled with fluid and pressurized, and to open these passages 35A1 during the admission of aspirated fluid, until the compression chamber is filled.

[0068] 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. The degassing outlet 20A is provided to vent this gas in order to optimize the cooling of the compression and discharge assembly 30.

[0069] In order to avoid gas circulation from the degassing chamber 3 to the suction chamber 2, the invention provides a degassing gas separation device 4 arranged between the suction chamber 2 and the degassing chamber 3.

[0070] For this purpose, the pump cylinder 31 includes through passages 41 ([Fig.4A] and [Fig.4B]) provided to fluidly connect the suction chamber 2 and the degassing chamber 3 to each other.

[0071] As illustrated in [Fig.3], the pump cylinder 31 comprises five (but not limited to) through passages 41 distributed regularly around the main axis A, here masked by the openings 43A1 described later.

[0072] As can be seen in [Fig. 2], a through passage 41 is positioned near the degassing outlet 20A. It will be understood that such a through passage 41 is adjacent to the degassing outlet 20A in a section of the piston pump 1 passing through the main shaft and through a shaft of the degassing outlet 20A. It is ensured that at least this passage is immersed by the fluid present in the degassing chamber 3.

[0073] These through passages 41 allow, among other things, the circulation of the fluid present in the suction chamber 2 towards the degassing chamber 3 in order to allow the cooling of the compression and discharge assembly 30.

[0074] In the illustrated example, the separation device 4 comprises a plurality of through passages 41 formed in the pump cylinder 31 to connect the suction chamber 2 and the degassing chamber 3. It will be understood that here a main body 40 of the separation device 4 is formed by the piston cylinder 31, more particularly, by the circular projection 31B of the pump cylinder 31.

[0075] Each through passage 41 is associated with a means of closing the corresponding passage 42.

[0076] The separation device 4 further includes a retaining ring 43 for the sealing means 42. The retaining ring 43 is arranged to bear against the main body 40 to ensure a seal between the suction chamber 2 and the degassing chamber 3. For this purpose, a sealing gasket 44 is provided between the retaining ring 43 and the main body 40.

[0077] The retaining ring 43 comprises a plurality of housings 43A, each intended to correspond to a through passage 4L

[0078] Each housing 43A is dimensioned to allow the movement of the corresponding sealing means 42. To this end, a sealing means 42 has a thickness El less than a thickness E2 of the corresponding housing 43A.

[0079] As shown in [Fig.3], [Fig.4A] and [Fig.4B], each housing 43A includes an opening 43A1 leading into the suction chamber 2. As will be described in more detail later, this opening 43A1 is configured to allow the flow of fluid from the suction chamber 2 to the degassing chamber 3.

[0080] Each sealing means 42 can be moved within its housing 43A between a closed position PO preventing fluid flow through its through passage 41 and an open position PI allowing fluid flow through its through passage 4L

[0081] Each sealing means 42 is in the form of a disc of material having peripheral openings 42A. More particularly, each sealing means 42 comprises a central area Z0 of material and peripheral areas ZI devoid of material forming the peripheral openings 42A.

[0082] In the closed position PO, the closing means 42 closes the opening 43A1 of the housing 43A. In the open position PI, the closing means 42 releases the opening 43A1 of the housing 43A and partially closes the associated through passage 41, i.e., it closes the entrance of the associated through passage 41, so that the fluid can flow from the suction chamber 2 to the degassing chamber 3 through the peripheral areas 42 of the sealing means 42.

[0083] As can be noted, each through passage 41 has a diameter DI greater than the diameter D2 of the opening 43A1 of the housing 43A and less than the diameter D3 of the housing 43A, so that the sealing means 42 is retained in the housing 43A between its positions PO, PI.

[0084] We will now describe the operation of the piston pump 1 shown equipped with the improvements according to the invention.

[0085] Before the piston pump 1 starts, the fluid arrives at the suction chamber 2 via the fluid inlet 10A of the inlet body 10 and the excess returns to the reservoir via the excess fluid discharge outlet 10B to cool the suction chamber 2 and the inlet chamber 4 by passing, on the one hand, through the filter 10C, and on the other hand, through peripheral openings 100A connecting the fluid inlet 10A to the suction chamber 2. As long as the suction chamber 2 is not completely cooled, the fluid returns to the reservoir carrying with it a fraction of gas generated by contact with the elements to be cooled.

[0086] Since the suction pressure is higher than the degassing pressure during this filling process, the sealing means 42 are in their open position PI, allowing the fluid to enter the degassing chamber 3 to cool the compression and discharge assembly 30. The fluid rises in the degassing outlet 20A of the outlet body 20 to a certain level. Degassing occurs via this degassing outlet 20A as long as the degassing chamber 3 has not been cooled to the fluid's saturation temperature.

[0087] Once the suction chamber 2 and the degassing chamber 3 have cooled down, the pump 1 can be started.

[0088] When the piston actuating rod 33 is pulled by a drive system, it causes the piston 32 to move backward, the conical valve 35B to open, causing the fluid to be drawn into the compression chamber from the intake chamber 4 (i.e., from the fluid contained in the suction chamber 2) via the intake passages 35A1 of the intake valve 35.

[0089] The aspirated fluid fills the compression chamber until the end of the stroke of the piston 32. The return of the piston 32 causes the valve 35B to close and the fluid contained in the compression chamber to be compressed until the outlet valve 36 is opened for the discharge of the pressurized fluid through the fluid outlet 20B of the outlet body 20 via the discharge opening 34A of the sleeve 34.

[0090] The separation device 4 is activated by the release of heat caused by the movement of the piston pump 1, without being directly dependent on this movement.

[0091] More specifically, the separation device 4 is activated by the pressure difference between the suction chamber 2 and the degassing chamber 3.

[0092] During the cooling phase of the piston pump 1 (i.e., before it starts), and particularly during the operation of the piston pump 1, the cooling of the degassing chamber 3, which includes the compression and discharge assembly 30, causes the fluid contained in this degassing chamber 3 to heat up. This heating causes the fluid to evaporate into a gas. The recoil of the piston 32 creates a compression phenomenon at the rear of this piston, and this pressure is transmitted to the degassing chamber 3.The pressure in the degassing chamber 3, called the degassing pressure, is increased until it reaches a pressure called the overpressure, which is greater than the pressure in the suction chamber 2, called the suction pressure, causing the sealing means 42 to move in their housing 43A to reach their sealing position PO, so that the gas or fluid in the degassing chamber is prevented from reaching the suction chamber 2.

[0093] Of course, it will be understood that the sealing means 42 are provided in a low density material, so that their movement between their positions PI, P2 can result from the pressure difference between the two chambers 2, 3.

[0094] Although the present 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 in an illustrative rather than restrictive sense.

Claims

Demands

1. A piston pump (1) for liquefied gases, such as hydrogen, said pump (1) comprising: - a fluid inlet (10A) intended to be connected to a fluid supply reservoir external to the pump (1), - a suction chamber (2) for receiving the fluid from said inlet (10A) and configured to be at a suction pressure, and - a fluid degassing chamber (3) communicating with a degassing outlet (20A) and configured to be at a degassing pressure, the piston pump (1) comprising a degassing gas separation device (4) arranged between the suction chamber (2) and the degassing chamber (3), the separation device (4) comprising a main body (40) having at least one through passage (41) connecting the suction chamber (2) and the degassing chamber (3) and a means for closing said passage, the means shutter (42) being configured for: - in a shutter position (PO),obstruct said passage when the degassing pressure is greater than the suction pressure; - in an open position (PI), open said passage (41) when the degassing pressure is less than or equal to the suction pressure.

2. Piston pump (1) according to the preceding claim, comprising a compression and discharge assembly (30) having a piston cylinder (31) in which a pump piston (32) can slide, the piston cylinder (31) forming said main body (40) of the separation device (4).

3. Piston pump (1) according to any one of the preceding claims, wherein the separation device (4) comprises a retaining ring (43) of at least one sealing means (42), the retaining ring (43) being provided to ensure a seal between the suction chamber (2) and the degassing chamber (3) in said sealing position (PO).

4. Piston pump (1) according to the preceding claim, wherein the separation device (4) comprises at least one housing (43A) of the sealing means (42) comprising an opening (43A1) to permit the passage of the fluid from the suction chamber (2) to the degassing chamber (3) in said open position (PI), the sealing means (42) being configured to move in said housing (43A) between said sealing position (PO) and said open position (PI), the housing (43A) being preferably formed in the retaining ring (43) and / or in the main body (40).

5. Piston pump (1) according to any one of the preceding claims, wherein the sealing means (42) comprises openings (42A).

6. Piston pump (1) according to the preceding claim, wherein the sealing means (42) has a central zone (Z0) of material and peripheral zones (Zl) without material forming the openings (42A), the central zone (Z0) is provided to seal the opening (43A1) of the housing (43A) in said sealing position (PO) and partially seal said through passage (41) in said opening position (PI), and the peripheral zones (Zl) are provided to allow the passage of fluid from the suction chamber (2) to the degassing chamber (3) in said opening position (PI).

7. Piston pump (1) according to any one of the preceding claims, wherein said through passage (41) is provided to open into the degassing chamber (3) near the degassing outlet (20A).

8. Piston pump (1) according to any one of the preceding claims, wherein the main body (40) of the separation device (4) comprises a plurality of through passages (41) each associated with a closing means (42).

9. Piston pump (1) according to any one of the preceding claims, wherein the separation device (4) is made of a low-density material, such as PTFE or PCTFE, so that it can be moved between said shut-off position (PO) and said open position (PI) as a function of the suction pressure and the degassing pressure.

10. Piston pump (1) according to any one of the preceding claims, wherein the sealing means (42) is removable.

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