Cryogenic pump

Abstract

A piston pump (1) suitable for pumping fluids at very low temperatures, such as hydrogen, the pump having a suction side (A) and a compression side (B), the suction side (A) being provided for the liquid and having an inlet (4) intended to be coupled to a liquid supply reservoir external to the pump (1), a suction chamber (3) for receiving the fluid, and a first fluid degassing duct (5) in communication with the suction chamber (3), the compression side (B) comprising a pump cylinder (2) carrying an assembly (8) for compressing and delivering the liquid, the cylinder (2) comprising a second chamber (6) in communication with the suction chamber (3), the fluid at very low temperature circulating to cool the compression and delivery assembly (8), piston pump.

Description

Technical Field

[0001] The present invention belongs to the technical field of cryogenic pumps applicable to gases liquefied at very low temperatures such as hydrogen.

Background Art

[0002] A cryogenic pump generally comprises a cylinder carrying an assembly for compression and delivery with a cylinder liner, and a piston moves axially to form a compression chamber. When this piston moves, the fluid is alternately sucked from the suction side towards the compression chamber and then compressed to be discharged through a dedicated opening.

[0003] The movement of the piston generates heat due to the friction of the piston rings of the piston within the cylinder liner, and this heat propagates into the compression chamber, heating the fluid and being able to convert a part of the fluid from an incompressible liquid state to a compressible gaseous state. As a result of hydraulic shock and / or cavitation formation, the efficiency of the pump decreases and the wear of the pump is accelerated. Therefore, it is necessary to ensure that the heat generation area is sufficiently cooled.

[0004] Most piston pumps are characterized by cooling and degassing only on the suction side. However, on the one hand, since a part of the accumulated heat is not released on the compression side, the cooling of the compression and delivery assembly is not proper, and on the other hand, the heat generated within the cylinder is sent to the suction chamber through a single degassing duct for release, resulting in heating of the liquid within the suction chamber. This process is generally not disadvantageous when used with standard cryogenic fluids up to -196°C such as nitrogen, for example, but when used with cryogenic fluids such as hydrogen having a liquefaction temperature of about -255°C, the pump may cavitate or deform due to insufficient cooling.

[0005] An object of the present invention is to propose a solution to the above problems.

Summary of the Invention

[0006] For this purpose, the present invention is a piston pump suitable for pumping cryogenic fluids such as hydrogen, the pump having a suction side and a compression side,

[0007] the suction side being provided with an inlet intended for liquid and coupled to a liquid supply reservoir external to the pump, a suction chamber for receiving the fluid, and a first fluid degassing duct in communication with the suction chamber,

[0008] the compression side comprising a pump cylinder having an assembly for compressing and delivering the liquid,

[0009] the cylinder comprising a second chamber in communication with the suction chamber, the fluid circulating to cool the compression and delivery assembly, relating to a piston pump.

[0010] The second chamber may have a length covering at least a part of the compression and delivery assembly. For example, the second chamber may surround the compression and delivery assembly.

[0011] The compression and delivery assembly generates heat which may propagate into the compression chamber. The second chamber allows a fluid at a very low temperature to cool the compression and delivery assembly, thereby avoiding heating of the fluid reaching the compression chamber and thus limiting gas formation.

[0012] According to one embodiment, the cylinder may comprise a first casing and an inner cylinder body carrying the compression and delivery assembly, the first casing being attached to the cylinder body so as to at least partially form the second chamber together with the body, the body having a concave shape allowing the fluid to flow into the second chamber.

[0013] The concave shape means that the body has an opening along its length, allowing the movement of the cooling fluid.

[0014] Advantageously, the pump may further comprise a second outward degassing duct that communicates with the second chamber and is configured to enable degassing of the fluid circulating within the second chamber.

[0015] The heat generated by the compression and delivery assembly is partially released through this second degassing duct, which prevents these hot gases from flowing back towards the suction chamber, thereby limiting the heating of this fluid and the risk of cavitation.

[0016] According to one embodiment, the compression and delivery assembly - a pump liner and a cylinder head that may be integral with each other and coaxial with the liner, - a piston that is axially movable within a liner that forms a fluid compression chamber together with the cylinder head, the cylinder head coupling the liner to the suction chamber, - a delivery opening disposed in the liner.

[0017] Advantageously, the cylinder head may comprise a pre-pressure chamber that communicates with the suction chamber.

[0018] For example, the pre-pressure chamber may include a volume formed by the wall of the cylinder head and a movable valve attached to a rod coaxial with the piston is disposed. For example, the rod is attached to the piston such that movement of the piston moves the valve.

[0019] This pre-pressure chamber supplies fluid from the suction chamber to the compression chamber. Since the volume of the pre-pressure chamber is larger than the volume of the compression chamber, the compression chamber is completely supplied with subcooled liquid from the suction chamber.

[0020] Advantageously, the cylinder head and / or the cylinder may comprise a graduated discharge port to enable adjustment of the pressure within the compression chamber. Thus, this creates advantageous properties for fluids that deviate from the saturation curve.

[0021] Advantageously, the pump comprises a second casing that is outside the first casing and forms a space intended to be discharged together with the first casing.

[0022] This thermally insulates the pump from the outside, limits heat exchange, and thereby limits the heating of the fluid.

[0023] Advantageously, an insulating material is disposed between the first casing and the second casing.

[0024] Preferably, the insulating material can be a multi-layer insulator. This provides better thermal insulation for the pump.

[0025] In one embodiment, the multi-layer insulator can preferably alternately include layers of aluminum and layers of glass fiber that are stacked on top of each other. Advantageously, the number of these layers can be between 10 and 100.

Brief Description of the Drawings

[0026] Further features and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings, which are given by way of non-limiting examples.

[0027]

Figure 1

Figure 2

Figure 3

[0028] Unless otherwise specified, the same elements appearing in different drawings have their own reference numerals.

Modes for Carrying Out the Invention

[0029] An embodiment of the pump 1 according to the present invention is shown in FIG. 1 as seen as a whole from the outside. The pump 1 has a suction side A and a compression side B. The suction side A is formed by a first casing 31 and has a suction chamber 3 having a first opening 4 that functions as a liquid inlet to the suction chamber 3. The opening 4 is configured to be coupled to an external reservoir (not shown) that contains a fluid at a very low temperature, for example hydrogen. The suction chamber 3 further comprises a second opening 5 for degassing the fluid entering the suction chamber 3. This second opening 5 is also configured to be coupled to the external reservoir.

[0030] Optionally, the suction side A may also comprise a second casing 32 that is external to the first casing 31. The two casings form a space that can be vented to thermally insulate this suction side A.

[0031] The compression side B comprises a pump cylinder 2 that includes a cylinder body 21 shown in FIG. 2. The cylinder body 21 carries a compression and delivery assembly 8 described later.

[0032] The cylinder 2 also comprises a first casing 22 that is external to the cylinder body 21. The cylinder 2 may also comprise a second casing 23 that is external to the first casing 22. As can be seen in FIG. 2, the first casing 22 and the second casing 23 form a space that can be vented to create thermal insulation for the cylinder 2 against the outside.

[0033] Advantageously, in order to enhance the thermal insulation of the cylinder 2, an insulating material 10, specifically a multi-layer insulator, may be disposed between the first casing 22 and the second casing 23.

[0034] The first casing 22 of the cylinder 2 forms, together with the cylinder body 21, a second chamber 6 that is attached to the cylinder body 21 and coupled to the suction chamber 3 via an opening 24, whereby a fluid at a very low temperature enters the second chamber 6 so as to cool the compression and delivery assembly 8.

[0035] To enable the circulation of the liquid in the second chamber 6, the cylinder body 21 has a hollow shape. In the illustrated embodiment, the rear portion of the body is hollowed out to form the rear portion 62 of the second chamber 6 together with the first casing 22. The front portion of the body is also hollowed out to form the front portion 61 of the second chamber 6. The intermediate portion of the cylinder body 21 is also hollow to allow the fluid to pass from the front portion 61 to the rear portion 62, but at the same time has a contact point 64 with the first casing 22. FIG. 3 is a partial cross-sectional view taken along line III-III of FIG. 1 showing an embodiment of the hollow shape of the intermediate portion of the body 21.

[0036] Advantageously, the cylinder 2 may comprise a second degassing duct 9 communicating with the second chamber 6 to enable the degassing of the fluid circulating in the second chamber 6.

[0037] The compression and delivery assembly 8 - a pump liner 81 and a cylinder head 84 that are integral and coaxial, - a piston 82 axially movable within a liner 81 that forms a fluid compression chamber together with the cylinder head 84, the cylinder head 84 coupling the liner 81 to the suction chamber 3, the piston 82, - a delivery opening 85 arranged in the liner 81, as shown in FIG. 2.

[0038] Optionally, the cylinder head 84 comprises a pre-pressure chamber 840 communicating with the suction chamber 3. For example, the pre-pressure chamber 840 is formed by a wall portion 841 that forms part of the cylinder head 84 and forms a space, and a movable valve 843 attached to a rod 842 coaxial with the piston 82 is arranged therein.

[0039] Advantageously, the cylinder head 84 may comprise a graduated discharge port 846 for adjusting the pressure in the compression chamber.

[0040] Possible pump operation

[0041] Before the pump 1 is started, the fluid reaches the suction chamber 3 through the inlet 4, passes through the filter 33 so as to cool the suction chamber 3 and the pre-pressure chamber 840, then passes through the opening of the valve 843, and returns to the reservoir through the opening 5. As long as the pre-pressure chamber 840 is not completely cooled, the fluid returning to the external reservoir contains a small amount of gas generated by contact with the elements to be cooled.

[0042] The fluid can also enter the second chamber 6 so as to cool the compression and delivery assembly 8. The fluid rises to a certain level in the second degassing duct 9. Degassing is carried out through the duct 9 until the second chamber 6 is cooled to the saturation temperature of the fluid.

[0043] When the suction chamber 3 and the parts are completely cooled, the pump 1 can be started.

[0044] When the rod 83 of the piston 82 is pulled (from left to right in FIG. 2) by the drive system, the rod 842 is moved, the plate 844 presses the valve 843, whereby the fluid present in the pre-pressure chamber 840 is pushed towards the compression chamber formed by the liner 81, the piston 82, and the cylinder head 84. The passage is through the opening 845, and the opening 845 is closed when the piston 82 returns (in the direction from right to left in FIG. 2), whereby the fluid is compressed by the piston 82 in the compression chamber and then discharged through the opening 85. A valve (not shown) that closes the opening 85 opens so as to allow the pressurized fluid to flow out of the pump 1.

[0045] The movement of the piston assembly 82 and the piston ring (not labeled) in the liner 81 generates heat that evaporates a small amount of cryogenic fluid. The second degassing duct 9 makes it possible to discharge the gaseous portion present in the second chamber 6 without returning it to the suction chamber 3 as is often the case with known pumps.

Claims

1. A piston pump (1) suitable for pumping a fluid at a very low temperature, such as hydrogen, said pump (1) having a suction side (A) and a compression side (B), said suction side (A) being provided for the liquid and intended to be coupled to a liquid supply reservoir external to said pump (1), an inlet (4), a suction chamber (3) for receiving said fluid, and a first fluid degassing duct (5) communicating with said suction chamber (3), said compression side (B) comprising a pump cylinder (2) carrying an assembly (8) for compressing and delivering said liquid, said cylinder (2) comprising a second chamber (6) communicating with said suction chamber (3), and said fluid at a very low temperature circulating to cool said compression and delivery assembly (8), piston pump (1).

2. said cylinder (2) comprising a first casing (22) and an internal cylinder body (21) carrying said compression and delivery assembly (8), said first casing (22) being attached to said cylinder body (21), and said cylinder body (21) having a concave shape enabling said fluid circulation within said second chamber (6), pump (1) according to claim 1.

3. The pump (1) according to claim 1 or 2, further comprising a second degassing duct (9) communicating with said second chamber (6) and configured to enable degassing of said fluid circulating within said second chamber (6).

4. Said compression and delivery assembly (8) comprises - a pump liner (81) and a cylinder head (84) that are integral and coaxial, - a piston (82) axially movable within said liner (81) forming a fluid compression chamber together with said cylinder head (84), said cylinder head (84) coupling said liner (81) to said suction chamber (3), piston (82), - a delivery opening (85) arranged in said liner, pump (1) according to any one of claims 1 to 3.

5. The pump (1) according to claim 4, wherein said cylinder head (84) comprises a pre-pressure chamber (840) communicating with said suction chamber (3).

6. The pump (1) according to claim 4 or 5, wherein the cylinder head (84) comprises a discharge port (846) configured to enable the pressure in the compression chamber to be adjusted.

7. The pump (1) according to any one of claims 2 to 6, wherein the cylinder (2) comprises a second casing (23) that is external to the first casing (22) and forms a space intended to be discharged together with the first casing (22).

8. The pump (1) according to claim 7, wherein an insulating material (10) is disposed between the first casing (22) and the second casing (23).

9. The pump (1) according to claim 8, wherein the insulating material (10) is a multi-layer insulator.

10. The pump (1) according to claim 9, wherein the multi-layer insulator alternately includes layers of aluminum and layers of glass fiber.

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