Fluid compression apparatus and method

Abstract

To provide a fluid compression apparatus and method, which comprises first and second compression chambers, an intake system into the first chamber, a transfer system from the first chamber to the second chamber, a piston for ensuring the compression of the fluid in the first and second chambers, and an orifice for discharging the compressed fluid.SOLUTION: An intake system (2) comprises one or more valves (2). An apparatus further comprises a discharge orifice (8) allowing communication between a first compression chamber (3) and a bath (16) to allow surplus liquid trapped in the first compression chamber (3) to leave during a compression movement of a piston (5) in the first compression chamber (3). The apparatus comprises a discharge valve (9) configured to control the discharge of liquid via the discharge orifice (8) and to prevent fluid from entering the compression chamber (3) via the discharge orifice (8).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a fluid compression device and method.

[0002] More particularly, the present invention is a fluid compression device having a plurality of compression stages, comprising a sealed housing intended to contain a bath of cryogenic fluid having a liquid phase, wherein the upper part of the housing is intended to contain a gas head space, a first compression chamber, a second compression chamber, a suction system in communication with the first compression chamber and configured to allow a fluid for compression to enter the first compression chamber, a transfer system in communication with the first and second compression chambers and configured to allow transfer of fluid from the first compression chamber to the second compression chamber, a movable piston for ensuring compression of the fluid in the first and second compression chambers, the device also comprising a discharge orifice in communication with the second compression chamber and configured to allow compressed fluid to exit, the second compression chamber being defined by a part of the piston body and a fixed wall of the device, the piston being capable of translating in a first longitudinal direction, wherein the suction system comprises one or more valves configured to ensure that the fluid for compression enters the first compression chamber during the suction stage and to prevent the fluid from exiting during the compression stage, the device further comprising a discharge orifice enabling communication between the first compression chamber and the bath so as to allow surplus liquid trapped in the first compression chamber to exit during the compression movement of the piston in the first compression chamber. The present invention relates to a fluid compression device.

Background Art

[0003] In order to improve the performance and volumetric efficiency of a liquid hydrogen pump, it is essential to have good thermodynamic quality of the liquid during suction. This is to avoid cavitation due to pressure drop and heat input. The high-pressure compression of the liquid drawn from a tank (bath or sample) containing the pump is often preceded by a first compression stage (or pre-compression). This pre-compression is generally a compression stage having a lower ratio than the second compression stage. The first compression stage sucks in a sub-saturated liquid at the saturation temperature of the bath and mechanically sub-cools the sub-saturated liquid by pressurization in order to achieve good filling without "flash" evaporation in the compression stage.

[0004] When two compression stages are generated by the movement of a single piston in opposite directions, the stage of filling the second compression stage is thus carried out simultaneously with the compression in the first stage.

[0005] Although the diameters of these chambers are different, the piston strokes are the same, so as a result, the stroke volumes can be different (typically, the first stage has a larger volume than the second stage). Assuming that the density of the fluid remains relatively constant (since there is little compressibility in the absence of flash evaporation), it may be essential to release a portion of the pressurized liquid from the first compression chamber during the inflow to the second stage.

[0006] It is a known practice to provide a port or channel connecting the first compression chamber and the bath in order to naturally release this surplus fluid to the bath.

[0007] This solution is not entirely satisfactory. This release of surplus liquid from the first compression stage can generate vaporized gas in the bath. SUMMARY OF THE INVENTION

[0008] One object of the present invention is to overcome all or some of the above-mentioned drawbacks of the prior art.

[0009] For this purpose, the device according to the invention, or else a device corresponding to its general definition given in the preamble, essentially comprises a discharge valve configured to control the discharge of liquid through a discharge orifice and to prevent fluid from entering the compression chamber through the discharge orifice.

[0010] In addition, embodiments of the invention may comprise one or more of the following features: - The discharge valve is a check valve comprising, for example, a shut-off flap acted upon by a spring. - The discharge orifice communicates with the housing via a flow retarder configured to attenuate the velocity and / or intensity of the flow of the discharged liquid by limiting its pressure drop. - The flow retarder comprises at least one of a nozzle made of a porous material and a set of diffuser holes. - The discharge orifice communicates with the housing via at least one discharge duct emerging in the housing in the bath, such that the discharge orifice is located in and / or above the bath of the housing. - The discharge duct has a portion extending into the housing parallel to and / or transverse to the longitudinal direction. - The discharge duct extends from the lower part to the upper part of the housing. - The discharge orifice communicates with the housing via a plurality of discharge ducts emerging in the housing. - The container contains a bath consisting of a cryogenic liquid, for example liquid hydrogen.

[0011] The present invention also relates to a method for pumping cryogenic fluids using such a device, where the container includes a bath of liquefied cryogenic fluid, and the method comprises, simultaneously during a first movement of the piston, flowing liquid into a first compression chamber via an intake system, and compressing the fluid in a second compression chamber; and then, during a second opposite movement of the piston, flowing fluid into the second compression chamber via a transfer system, and compressing the liquid in the first compression chamber, where excess fluid is discharged from the first compression chamber via a discharge orifice therebetween.

[0012] The present invention may also relate to any alternative device or method comprising any combination of the above or below features within the scope of the claims.

[0013] Further significant features and advantages will become apparent upon reading the following description provided with reference to the figures.

[0014] The present invention will be better understood by way of example only and upon reading the subsequent description with reference to the accompanying drawings.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

[0016] Throughout the drawings, the same reference numerals are associated with the same elements.

[0017] In the embodiments for carrying out the present invention, the following embodiments are examples. The description refers to one or more embodiments, but this does not mean that these features are applicable only to a single embodiment. The individual features of different embodiments can also be combined and / or exchanged to provide other embodiments.

[0018] The fluid compression device 1 shown in [FIG. 1] includes two compression stages in series generated by a single piston 5 driven by an alternating movement by a drive member 11.

[0019] The device 1 particularly includes a first compression chamber 3 (at a relatively low pressure) and a second compression chamber 4 (at a relatively high pressure).

[0020] The device 1 includes an intake system 2 that communicates with the first compression chamber 3 and is configured to allow the fluid for compression to enter the first compression chamber 3.

[0021] The suction system 2 comprises, for example, at least one of one or more check valves, one or more orifices or ports, at least one flat disk valve, or any other device or valve that allows the fluid for compression to enter the first compression chamber 3 during the suction phase (here, the upward stroke of the piston 5) and prevents the fluid from exiting during the compression phase (here, the downward stroke of the piston 5).

[0022] In particular, this suction system 2 (valve(s) and / or the like) can be configured to open when there is a predetermined pressure difference between its two ends. Additionally, the first chamber 3 can optionally be equipped with a safety valve or other safety element configured to limit the pressure inside the chamber below a predetermined safety threshold.

[0023] The device 1 also comprises a check transfer system 6 that communicates with the first compression chamber 3 and the second compression chamber 4 and is configured to allow the transfer of fluid from the first compression chamber 3 to the second compression chamber 4 (during and / or at the end of the compression phase of the fluid in the first compression chamber 3), but remains closed during the compression phase in the second compression chamber 4. This transfer system 6 can be of the same type as the suction system 2.

[0024] The device 1 comprises a piston 5 that can translate (detailed below) to ensure the compression of the fluid in the first compression chamber 3 and the second compression chamber 4.

[0025] The device 1 further comprises a discharge orifice 7 that communicates with the second compression chamber 4 and is configured to allow the high-pressure compressed fluid to exit from the second compression chamber 4 (during or at the end of the compression phase in this chamber 4). The discharge orifice 7 can be provided with a check system, which can be of the same type as the suction system 2 (for example, closed as long as the pressure difference between the second compression chamber 4 and the outside is below a predetermined threshold).

[0026] As illustrated, the second compression chamber 4 can be defined by a part of the body of the piston 5 and a fixed wall of the device. The piston 5 can translate in the longitudinal direction A, for example, vertically in a certain operating configuration.

[0027] As illustrated, the piston 5 comprises, for example, a tubular part mounted around a fixed central guide 12. The end part of the central guide 12 forms, for example, a fixed wall that defines a part of the second compression chamber 4. The device 1 comprises a sealing system (not shown for the sake of simplicity) formed between the central guide 12 and the piston 5 (piston ring(s), seal(s), or the like). In the longitudinal direction A of the translation of the piston 5, the suction system 2 is preferably located at the first end of the device 1, the discharge orifice 7 is located at the second end of the device, and the transfer system 6 is located between the suction system 2 and the discharge orifice 7.

[0028] The discharge orifice 7 can be located at the lower end of the central guide 12 (the fixed upper end of the second compression chamber 4). The device 1 can comprise a compressed gas discharge duct having a first lower end connected to this discharge orifice 7 and a second upper end located at the upper part of the device 1 for collecting the compressed high-pressure fluid.

[0029] As illustrated, one end of the piston 5 forms a movable surface for compressing the fluid in the first compression chamber 3, while the tubular part of the piston 5 forms a movable sleeve that cooperates with the end part of the central guide 12 so as to form a system for compressing the fluid in the second compression chamber 4 (in this second compression stage, the end part of the central guide 12 thus forms a fixed piston that cooperates with the movable sleeve).

[0030] As illustrated, the first compression chamber 3 can be formed in a tubular cavity 14 or a fixed chamber whose lower end is closed. Thus, the lower part of the first compression chamber 3 can be defined by this fixed lower cavity 14. The suction system 2 can be located at the lower end of the lower cavity 14.

[0031] Accordingly, the upper part of the first compression chamber 3 can be defined by the lower end of the piston 5 and a sealing system (piston ring or the like) formed between the piston 5 and the wall of the lower cavity 14.

[0032] Preferably, the first compression chamber 3 is configured to facilitate the escape of gas through ports or valves. For example, as schematically shown, one or more ports 26 (or orifices) can be formed in the upper part of the lower cavity 14 (or any fixed wall portion defining at least a part of the first combustion chamber 3). These ports 26 can be provided such that when the piston 5 does not cover them (when the piston 5 is above at least a part of the ports 26), the first compression chamber 3 communicates with the outside. Thus, during the suction stage (as the chamber 3 enlarges), any gas that may be present in the first compression chamber 3 can escape through these ports 26 and yield its place to the liquid from the surrounding bath. This ensures that it is completely filled with liquid during suction. In addition, during the compression stage (when the piston 5 moves downward in the second compression chamber 3), these ports 26 can release excess liquid, thereby metering the volume of liquid trapped therein (this volume can be determined by the longitudinal position of the ports 26). Then, the piston 5 continues its compression stroke in the first compression chamber 3, and the ports 26 no longer communicate with the compression volume (which is isolated from the bath 16).

[0033] As illustrated, the compression device 1 can comprise a thermally insulated sealed housing 13 containing a bath 16 of cryogenic cooling fluid. In particular, the first compression chamber 3 and the second compression chamber 4 can be immersed in the liquid phase. The upper part of the housing 13 can have a gas head space that collects any leakage from the device 1.

[0034] The compression device 1 further comprises a discharge orifice 8 configured to enable fluid communication between the first compression chamber 3 and the bath 16 and to allow excess liquid trapped in the first compression chamber 3 to exit during the compression movement of the piston 5 in the first compression chamber 3.

[0035] The discharge valve 9 is provided to control the discharge of the liquid through the discharge orifice 8 and to prevent the fluid from entering the compression chamber 3 through the discharge orifice 8.

[0036] The discharge valve 9 is, for example, a check valve, for example, having a shut-off flap that is spring-loaded to a closed position on a seat.

[0037] [Figure 2] As illustrated for reference below, the discharge orifice 8 preferably communicates with the housing 13 via a flow retarder 10 configured to attenuate the velocity and / or intensity of the discharged liquid flow by limiting its pressure drop.

[0038] The retarder 10 is preferably configured to reduce the influence of the pressure drop caused by diffusion or friction or the intense impact of a forceful discharge jet. The retarder "breaks the momentum" of such a jet.

[0039] Such a retarder 10 produces a non-rapid discharge of the flow, and the flow loses velocity but converts it into pressure rather than a pressure drop. This limits the possible splashing or friction of the liquid towards the high-temperature region of the wall of the suction bath that could cause the liquid to evaporate.

[0040] The flow retarder 10 may comprise, for example, a nozzle made of a porous material. See [Figure 2], [Figure 3], [Figure 4], and [Figure 5]. For example, the porous sintered material may comprise a sintered body made of bronze or stainless steel, for example, cylindrical or conical. The length can be from 15 mm to 350 mm. The diameter can be from 10 mm to 45 mm. The permeability can be greater than 5 darcy (>5D), where 1 darcy is equal to 10 -12 m 2 is equal to.

[0041] This allows, without pressure drop, to "dampen the momentum" of the discharge injection and at the same time reduce the contact between the near-saturated liquid and the potentially warmer part or vapor of the bath 16.

[0042] As illustrated, the discharge orifice 8 can communicate with the housing 13 via at least one discharge duct 11 (two in the illustrated example) coming out of the housing 13. The discharge duct 11 can extend as follows: - Horizontally, for example, in a liquid bath, coming out of the lower part of the container, see [Figure 1], - Horizontally and then vertically upwards, for example, in a liquid bath, coming out of the lower part of the container, see [Figure 4], - Horizontally and then vertically, for example, at the junction between the liquid bath and the gas headspace, see [Figure 5], - Horizontally and then vertically, for example, above the liquid bath and the gas headspace, see [Figure 2] and [Figure 3].

[0043] When the retarder 10 is provided, the retarder 10 is preferably provided at the downstream end of the discharge duct 11 (in the container / bath).

[0044] Thus, as illustrated, the ends of the discharge duct 11 can be directed upwards or downwards or horizontally.

[0045] In particular, in order to reduce the contact between potential bubbles and the liquid of the bath 16, it is possible to direct the discharge duct(s) 11 vertically. In this way, the bubbles are directed slightly towards the upper part of the bath and thus towards the gas headspace, while the liquid flows into the liquid phase.

[0046] In the case of discharge to the gas part, the discharged liquid flow can come out little by little and flow slowly into the liquid phase. In this way, the heat exchange between the liquid phase and the gas phase is limited. As illustrated, the two discharge ducts 11 can be connected to a single discharge valve 9 via a common chamber.

[0047] In the modification of [FIG. 6], the retarder 10 comprises or consists of a tube having a porous surface extending vertically within the container 13.

[0048] In the modification of [FIG. 7], the retarder 10 comprises or consists of a tube perforated with a number of orifices to allow the liquid to flow out little by little. For example, the orifices have dimensions of 0.05 mm to 1 mm.

[0049] In the modification of [FIG. 8], the retarder 10 comprises or consists of a tube perforated with a number of orifices arranged in a coil around two compression chambers.

[0050] The present invention is particularly advantageous for pumping hydrogen, for example, to generate a flow of hydrogen at a very high pressure (for example, a pressure of 100 to 1,000 bar) at the outlet of the second compression stage.

Claims

1. A fluid compression device (1) having a plurality of compression stages, wherein the fluid compression device (1) comprises a sealed housing (13) intended to contain a cryogenic fluid bath (16) having a liquid phase, wherein the upper part of the sealed housing (13) is intended to contain a gas head space, a first compression chamber (3), a second compression chamber (4), an intake system (2) communicating with the first compression chamber (3) and configured to allow a compression fluid to enter the first compression chamber (3), a transfer system (6) communicating with the first compression chamber (3) and the second compression chamber (4) and configured to allow transfer of fluid from the first compression chamber (3) to the second compression chamber (4), and a movable piston (5) for ensuring compression of the fluid in the first compression chamber (3) and the second compression chamber (4). The fluid compression device (1) further comprises a discharge orifice (7) communicating with the second compression chamber (4) and configured to allow compressed fluid to exit. The second compression chamber (4) is defined by a part of the body of the movable piston (5) and a fixed wall of the fluid compression device. The movable piston (5) is capable of translating in a first longitudinal direction (A). Here, the intake system (2) comprises one or more valves (2) configured to ensure that the compression fluid enters the first compression chamber (3) during the intake stage and to prevent fluid from exiting during the compression stage. In a fluid compression device (1), the fluid compression device further comprises a discharge orifice (8) allowing communication between the first compression chamber (3) and the bath (16) such that excess liquid trapped in the first compression chamber (3) can exit during the compression movement of the movable piston (5) in the first compression chamber (3). The fluid compression device includes a discharge valve (9) configured to control the discharge of liquid through the discharge orifice (8) and prevent fluid from entering the first compression chamber (3) through the discharge orifice (8), and the discharge orifice (8) communicates with the sealed housing (13) through at least one discharge duct (11) that exits into the sealed housing (13) in the bath (16) such that the discharge orifice (8) is located in and / or above the bath of the sealed housing (13). Fluid compression device, characterized in that.

2. The fluid compression device according to claim 1, characterized in that the discharge valve (9) is a check valve, for example, comprising a shut-off flap that is acted upon by a spring.

3. The fluid compression device according to claim 1 or 2, characterized in that the discharge orifice (8) communicates with the sealed housing (13) via a flow retarder (10) configured to attenuate the velocity and / or intensity of the flow of the discharged liquid by limiting its pressure drop.

4. The fluid compression device according to claim 3, characterized in that the flow retarder (10) comprises at least one of a nozzle made of a porous material and a set of diffusion holes.

5. The fluid compression device according to any one of claims 1 to 4, characterized in that the discharge duct (11) has a portion extending into the sealed housing (13) parallel to and / or transverse to the longitudinal direction (A).

6. The fluid compression device according to any one of claims 1 to 5, characterized in that the discharge duct (11) extends from the lower part to the upper part of the sealed housing (13).

7. The fluid compression device according to any one of claims 1 to 6, characterized in that the discharge orifice (8) communicates with the sealed housing (13) through a plurality of discharge ducts (11) that exit into the sealed housing (13).

8. The fluid compression device according to any one of claims 1 to 7, characterized in that the container includes a bath composed of a cryogenic liquid, for example, liquid hydrogen.

9. A method for pumping a cryogenic fluid using the fluid compression device according to any one of claims 1 to 8, wherein the container (13) contains a bath of liquefied cryogenic fluid, and the method comprises, simultaneously during a first movement of the movable piston (5), introducing a liquid into the first compression chamber (3) via the suction system (2), and compressing the fluid in the second compression chamber (4); and then, during a second movement of the movable piston (5) in the opposite direction, introducing a fluid into the second compression chamber (4) via the transfer system (6), and compressing the liquid in the first compression chamber (3), wherein excess fluid is discharged from the first compression chamber (3) therebetween via the discharge orifice (8).

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