Subcooling of the outlet fluid from a cryogenic pump

Abstract

The invention relates to a piston pump (1) for liquefied gases, such as hydrogen, said pump (1) comprising: - a supply inlet (10A) and a filling outlet (20A) - a suction chamber (2) for receiving fluid from said inlet (10A), and - a fluid degassing chamber (3) communicating with a degassing outlet (20B), - a compression and discharge assembly (30) comprising a compression chamber having a compression outlet (50A) fluidly connected to the filling outlet (20A) of the piston pump (1), the compression outlet (50A) being offset from the filling outlet (20A), the compression outlet (50A) and the filling outlet (20A) being connected to each other via a connecting portion (5) that runs at least partly through said degassing chamber (3).

Description

Subcooling of the outlet fluid from a cryogenic pump

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

[0002] A piston pump essentially has a pump cylinder with a cylinder liner and a compression chamber, a pump piston which is linearly guided within the cylinder liner, an intake valve arranged in an intake area of the compression chamber and used for the intake of the cryogenic fluid, and an outlet valve arranged in an outlet area of the compression chamber and used for the discharge of the cryogenic fluid.

[0003] The pump piston is conceived to move back and forth in the cylinder liner to carry out the pumping process and to form or enlarge and shrink the compression chamber through the back-and-forth movement of the pump piston.

[0004] More particularly, as this piston moves, the fluid is alternately drawn from the suction side towards the compression chamber, then pressurized in order to be evacuated through the dedicated outlet.

[0005] In some filling applications, the fluid evacuated through the dedicated outlet needs to be at the coldest possible temperature, in order to achieve the highest possible fluid density.

[0006] However, the fluid leaving the pump may be heated mainly due to the friction generated by the movement of the piston rings with respect to the pump liner, and due to its compression. The heating generated by the movement of the piston rings can be partially mitigated by dissipating it through the fluid present in the degassing chamber, where the heated liquid can be evaporated in the form of a gas. The degassing outlet is intended to evacuate this gas to optimize cooling of the compression and discharge assembly.

[0007] However, the degassing outlet is not sufficient to enable the outlet fluid to be cooled to the lowest possible temperature in some filling applications.OBJECT OF THE INVENTION

[0008] The aim of the present invention is to provide a solution to the technical problems described above by proposing a piston pump for cryogenic fluid that enables the outlet fluid to be cooled further.

[0009] To this end, the object of the invention is a piston pump for liquefied gases, such as hydrogen, said pump comprising:

[0010] - a supply inlet designed to be connected to a fluid supply tank external to the pump,

[0011] - a filling outlet designed to be connected to a filling device,

[0012] - a suction chamber for receiving fluid from said inlet, and

[0013] - a fluid degassing chamber communicating with a degassing outlet,

[0014] - a compression and discharge assembly comprising a compression chamber having a compression outlet fluidly connected to the filling outlet of the piston pump,

[0015] the compression outlet being offset from the fluid outlet,

[0016] the compression outlet and the filling outlet being connected to each other via a connecting portion that runs at least partly through said degassing chamber.

[0017] According to one embodiment of the invention, the piston pump extends along a main axis and said connecting portion extends at least partially along a secondary axis which can be parallel to the main axis.

[0018] According to one embodiment of the invention, said connecting portion extends over at least 20% of the length of the degassing chamber.

[0019] According to one embodiment of the invention, said connecting portion houses an outlet valve.

[0020] According to one embodiment of the invention, said connecting portion has a body configured to be at least partly in contact with the fluid present in the degassing chamber.

[0021] According to one embodiment of the invention, said compression outlet is formed at least partly in a pump cylinder of the compression and discharge assembly.

[0022] According to one embodiment of the invention, said connecting portion and the cylinder are a single piece.

[0023] According to one embodiment of the invention, said connecting portion is a separate part intended to connect the compression outlet to the fluid outlet.

[0024] According to one embodiment of the invention, said connecting portion has a section with a diameter that is reduced with respect to a main diameter of the connecting portion.

[0025] Further features and advantages of the invention will become apparent from the following detailed description, which can be understood with reference 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.DESCRIPTION OF THE DRAWINGS

[0026] shows a perspective view of a piston pump for liquefied gases.

[0027] shows a partial sectional view of the piston pump shown in

[0028] shows a sectional view of an enlargement of the connecting section shown in

[0029] 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 the fluid and discharging the fluid.

[0030] The inlet body 10 of the piston pump 1 comprises a supply inlet 10A designed to be connected to an external fluid supply tank and a surplus fluid discharge outlet 10B intended to be connected, preferably, to the same supply tank.

[0031] The outlet body 20 of the piston pump 1 comprises a degassing outlet 20B and a filling outlet 20A having an axis A20. As will be described in more detail below, the outlet body 20 of the piston pump 1 comprises 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 input 20C provided on the outlet body 20.

[0032] The surplus fluid discharge outlet 10B is intended to return to the tank the surplus fluid that is not used for cooling the piston pump 1.

[0033] The degassing outlet 20B is intended to evacuate gases that may result from the heating of the fluid that may take place in the outlet body 20.

[0034] With reference to, a sectional view of the interior of the piston pump 1 is shown.

[0035] The inlet body 10 comprises an inner casing 10' and an outer casing 10'' delimiting between them an insulating space that can be placed under vacuum to thermally insulate the inner casing thereof.

[0036] The inner casing 10' of the inlet body 10 is connected to the supply inlet 10A of the piston pump 1 and comprises a filter 10C through which the fluid enters.

[0037] The outlet body 20 comprises an inner casing 20' and an outer casing 20'' which also delimit between them an insulating space that can be placed under vacuum to thermally insulate the inner casing 20' thereof.

[0038] Advantageously, an insulating material, in particular a multi-layer insulator, can be arranged in the insulating space of the inlet body 10 or outlet body 20.

[0039] The inner casing 20' of the outlet body 20 is connected to the filling outlet 20A and the degassing outlet 20B of the piston pump 1 and partly houses a compression and discharge assembly 30.

[0040] The compression and discharge assembly 30 comprises the pump cylinder 31, within which the previously introduced pump piston 32 slides.

[0041] The pump cylinder 31 is arranged in the inner casing 20' of the outlet body 20.

[0042] The inner casing 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.

[0043] The degassing outlet 20B is fluidically connected to the degassing chamber 3.

[0044] The fluid inlet 10A is fluidically connected to the suction chamber 2.

[0045] These chambers 2, 3 are delimited by the pump cylinder 31 mounted without clearance in the inner casing 20' of the outlet body 20.

[0046] As illustrated, the pump cylinder 31 houses a pump liner 34 within which the pump piston 32 can slide back and forth between a position forming a fluid-filled compression chamber and a compression position in which the compression chamber is emptied of fluid through a compression outlet 50A that passes through the liner 34 and the pump cylinder 31.illustrates the compression position of the pump piston 32.

[0047] The pump cylinder 31 is associated with an intake valve 35 arranged in the suction chamber 2 and used for the intake of the fluid, and an outlet valve 36 used for the discharge of the pressurized fluid.

[0048] The compression and discharge assembly 30 comprises,inter alia:

[0049] - the pump cylinder 31, the pump liner 34 and the intake valve 35, which are integral and coaxial,

[0050] - the pump piston 32 which is axially movable in the liner 34 forming a fluid compression chamber with the intake valve 35.

[0051] The pressurized fluid can be discharged from the compression chamber via a compression outlet 50A connecting the compression chamber to a connecting portion 5 intended for evacuating the pressurized fluid.

[0052] However, the pressurized fluid is heated due to its being compressed and due to the friction generated by the movement of the rings 32A of the piston 32 with respect to the pump liner 34. While this heating can be limited through dissipation thereof into the degassing chamber 3 in the form of gas through the degassing outlet 20B, the cooling of the pressurized fluid is not sufficient to guarantee the lowest possible temperature at the filling outlet 20A.

[0053] To ensure subcooling, the connecting portion 5 is intended to lengthen the path of the pressurized fluid in the degassing chamber 3 in order to enable it to be cooled by the fluid comprised inside the degassing chamber 3 along the connecting portion 5 housed in the degassing chamber 3.

[0054] As shown, the compression outlet 50A has an axis A50 and the filling outlet 20A has an axis A20. The axes A50 and A20 of the compression outlet 50A and the discharge outlet 20A are advantageously offset from one another, so as to ensure a longer path for the pressurized fluid leaving the compression outlet 50A through the degassing chamber 3.

[0055] To ensure this longer path for the pressurized fluid in the degassing chamber 3, a connecting portion 5 is provided to link the compression outlet 50A to the filling outlet 20A. Advantageously, the connecting portion 5 is intended to run at least partly through the degassing chamber 3.

[0056] It will be understood that the pressurized fluid is separated from the fluid contained in the degassing chamber 3. However, the connecting portion 5 allows heat exchange between the pressurized fluid and the fluid present in the degassing chamber 3.

[0057] For this purpose, the connecting portion 5 can be formed by a body 51, at least part of the outer wall of which is in contact with the fluid present in the degassing chamber 3. In this way, it is possible to optimize the cooling of the compressed fluid using the fluid present in the degassing chamber, by dissipating heat through the walls of the connecting portion 5.

[0058] The body 51 of the connecting portion 5 advantageously has a reduced section 51, in order to generate an additional external surface in contact with the fluid in the degassing chamber 3.

[0059] As shown in, said connecting portion 5 has a reduced section 51 with a diameter D2 that is reduced with respect to a main diameter D1 of the connecting portion 5.

[0060] The connecting portion 5 preferably extends along a secondary axis A1 parallel to the main axis A0 of the piston pump 1. It can be envisaged that the connecting portion 5 extends over at least 20% of the length L of the degassing chamber 3.

[0061] The compression outlet 50A opens into an inlet channel 51 formed in the body 50 of said portion 5. The inlet channel 51 can be angled to modify the path of the compression fluid from a flow direction parallel to the axis A50 of the compression outlet 50A to a flow direction parallel to the secondary axis A1 of said portion 5.

[0062] Advantageously, the connecting portion 5 houses the outlet valve 36 used for discharging the pressurized fluid.

[0063] As shown, the inlet channel 51 opens onto the outlet valve 36. The arrangement of the outlet valve 36 in said portion 5 advantageously makes it possible to optimize the space that it occupies in the piston pump 1.

[0064] An outlet channel 52 is also formed in the body 50 of said portion 5. The outlet channel 52 can also be angled to modify the path of the compression fluid from a flow direction parallel to the secondary axis A1 of said portion 5 to a flow direction parallel to the axis A20 of the filling outlet 20A.

[0065] The body 51 may include a leg 53 intended to optionally cooperate with the degassing outlet 20. Advantageously, this leg 53 is intended to partially form the filling outlet 20A.

[0066] It can be envisaged that the connecting portion 5 is a separate part, that is, a part separate from the pump cylinder 31, or alternatively a part formed integrally with the pump cylinder 31. In the latter case, the leg 53 can be separated from the body 51 of said portion 5, to facilitate assembly of the pump 1.

[0067] A description will now be given of the operation of the piston pump 1 shown, provided with the improvements according to the invention.

[0068] Before the piston pump 1 starts up, fluid enters the suction chamber 2 via the supply inlet 10A of the inlet body 10, and the surplus of this fluid returns to the tank via the surplus fluid discharge outlet 10B. The fluid cools the suction chamber 2 and the intake chamber 4 as it passes, on the one hand, through the filter 10C. As long as the suction chamber 2 has not cooled down completely, the fluid returns to the tank taking with it a fraction of gas generated by contact with the elements to be cooled.

[0069] Degassing takes place via the degassing outlet 20B until the degassing chamber 3 has cooled to below the saturation temperature of the fluid.

[0070] Once the suction chamber 2 and the degassing chamber 3 have cooled down, the pump 1 can be started up.

[0071] When the actuating rod 33 of the piston is pulled by a drive system, it causes the piston 32 to move backwards, and the intake valve 35 opens, causing fluid to be then sucked into the compression chamber from the intake chamber 4 (that is, fluid contained in the suction chamber 2) via the intake passages 35A of the intake valve 35.

[0072] The sucked-in fluid fills the compression chamber until the piston 32 reaches the end of its stroke. The return stroke of the piston 32 causes the closing of the valve 35B and the compression of the fluid contained in the compression chamber until it causes the opening of the outlet valve 36 housed in the connecting portion 5. The pressurized fluid then proceeds to flow through the connecting portion 5. The walls of the body 51 of said portion 5 allow for a heat exchange between the pressurized fluid and the fluid present in the degassing chamber 3, facilitating the dissipation of the accumulated heat from the pressurized fluid. The heat thus transferred to the fluid present in the degassing chamber 32 can therefore be dissipated by evaporation in the form of gas via the degassing outlet 20B.

[0073] The pressurized fluid thus cooled that leaves the outlet valve 36 can be sent back for discharge via the filling outlet 20A of the outlet body 20 through the compression outlet 50A.

[0074] Although the present description refers to specific examples of 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 can be combined in additional embodiments. Consequently, the description and drawings should be considered in an illustrative rather than a restrictive sense.

Claims

A piston pump (1) for liquefied gases, such as hydrogen, said pump (1) comprising:- a supply inlet (10A) designed to be connected to a fluid supply tank external to the pump (1),- a filling outlet (20A) designed to be connected to a filling device,- a suction chamber (2) for receiving fluid from said inlet (10A), and- a fluid degassing chamber (3) communicating with a degassing outlet (20B),- a compression and discharge assembly (30) comprising a compression chamber having a compression outlet (50A) fluidly connected to the filling outlet (20A) of the piston pump (1),the compression outlet (50A) being offset from the filling outlet (20A),the compression outlet (50A) and the filling outlet (20A) being connected to each other via a connecting portion (5) that runs at least partly through said degassing chamber (3).The piston pump (1) according to the preceding claim, wherein the piston pump (1) extends along a main axis (A0) and said connecting portion (5) extends at least partially along a secondary axis (A1) which can be parallel to the main axis (A).The piston pump (1) according to one of the preceding claims, wherein said connecting portion (5) extends over at least 20% of the length (L) of the degassing chamber (3).The piston pump (1) according to one of the preceding claims, wherein said connecting portion (5) houses an outlet valve (36).The piston pump (1) according to one of the preceding claims, wherein said connecting portion (5) has a body (51) configured to be at least partly in contact with the fluid present in the degassing chamber (3).The piston pump (1) according to one of the preceding claims, wherein said compression outlet (50A) is formed at least partly in a pump cylinder (31) of the compression and discharge assembly (30).The piston pump (1) according to the preceding claim, wherein said connecting portion (5) and the cylinder are a single piece.The piston pump (1) according to one of the preceding claims, wherein said connecting portion (5) is a separate part intended to connect the compression outlet (50A) to the filling outlet (20A).The piston pump (1) according to one of the preceding claims, wherein said connecting portion (5) has a section with a diameter (D2) that is reduced with respect to a main diameter (D1) of the connecting portion (5).

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