Fluid compression apparatus and method

Abstract

A fluid compression apparatus having a plurality of compression stages, comprising: a sealed enclosure for containing a bath of cryogenic fluid having a liquid phase, an upper portion of the enclosure for containing a gas headspace; a first compression chamber; a second compression chamber; a suction system in communication with the first compression chamber and configured to allow fluid to enter the first compression chamber; a transfer system in communication with the first and second compression chambers and allowing fluid pre-compressed in the first compression chamber to be transferred to the second compression chamber, the apparatus further comprising a discharge orifice in communication with the second compression chamber and allowing fluid compressed therein to exit, the suction system comprising a valve, the apparatus includes a first compression chamber configured to ensure that a fluid to be compressed enters the first compression chamber during a suction phase and to prevent the fluid from exiting during a compression phase, and a discharge port that allows communication between the first compression chamber and the bath to allow excess liquid trapped in the first compression chamber to exit during fluid compression therein. The invention also relates to a method for pumping cryogenic fluid by using the device.

Description

Technical Field

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

[0002] More particularly, the present invention relates to a fluid compression device having a plurality of compression stages, the fluid compression device comprising: a sealed housing intended to receive a bath of a cryogenic fluid having a liquid phase, an upper portion of said housing being intended to receive a gas headspace; a first compression chamber; a second compression chamber; an intake system in communication with said first compression chamber and configured to allow fluid to enter said first compression chamber; a transfer system in communication with said first compression chamber and said second compression chamber and configured to allow the fluid pre-compressed in said first compression chamber to be transferred to said second compression chamber, the device further comprising a discharge orifice in communication with said second compression chamber and configured to allow the fluid compressed in said second compression chamber to leave, wherein said intake system comprises one or more valves configured to ensure that the fluid to be compressed enters said first compression chamber during the intake phase and to prevent the fluid from leaving during the compression phase, the device further comprising a discharge port / discharge orifice allowing communication between said first compression chamber and said bath so that the excess liquid trapped in said first compression chamber leaves during the compression of the fluid in said first compression chamber. Background Art

[0003] In order to improve the performance and volumetric efficiency of a liquid hydrogen pump, it is crucial to have good liquid thermodynamic properties at the inlet. This is to avoid cavitation caused by pressure drop and heat input. The high-pressure compression of the liquid withdrawn from a storage tank (bath or pool) containing the pump is typically carried out before the first compression stage (or pre-compression). This pre-compression is typically a compression stage with a lower rate than the second compression stage. The first compression stage sucks in a quasi-saturated liquid at the saturation temperature of the bath and mechanically subcools it by pressurization in order to achieve good filling in the compression stage without "flashing" vaporization.

[0004] In particular, in the case where the two compression stages are achieved by the opposite movement of the same piston, the stage of filling the second compression stage thus occurs simultaneously with the compression in the first stage.

[0005] Since the diameters of the chambers are different, but the piston strokes are the same, the discharged volumes may be different (usually the volume of the first stage is larger than that of the second stage). Assuming that the density of the fluid remains relatively constant during entry into the second stage (because there is little compressibility without flashing), it may be necessary to discharge some pressurized liquid from the first compression chamber.

[0006] It is known to provide ports or channels establishing communication between the first compression chamber and the bath in order to naturally discharge the excess fluid into the bath.

[0007] This discharge of excess liquid from the first compression stage generates vaporized gas in the pool. SUMMARY OF THE INVENTION

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

[0009] To this end, the basic feature of the device according to the invention, which is otherwise in line with the general definition given in the above preamble, is that it has a discharge valve configured to control the discharge of liquid via the discharge port and to prevent fluid from entering the first compression chamber via the discharge port, the discharge port being in communication with the housing via at least one flow retarder configured to attenuate the velocity and / or intensity of the discharged liquid flow by restricting the pressure drop of the discharged liquid flow.

[0010] Furthermore, embodiments of the present invention may have one or more of the following features:

[0011] - The flow retarder includes at least one of the following: a set of diffuser holes; a nozzle made of a porous material having a permeability preferably greater than 5 darcies;

[0012] - The flow retarder includes at least one of the following: a nozzle made of a porous sintered material, such as bronze or stainless steel, the nozzle preferably being cylindrical or conical;

[0013] - The length of the flow retarder is in the range of 15 mm to 450 mm, and the diameter of the flow retarder is preferably in the range of 10 mm to 80 mm;

[0014] - The discharge port is in communication with the housing via at least one discharge pipe leading to the housing, the at least one discharge pipe being located in the bath so as to be able to be in the bath of the housing and / or above the liquid level of the bath of the housing;

[0015] - The discharge pipe has a portion extending into the housing parallel to the vertical direction and / or transversely to the vertical direction;

[0016] - The discharge pipe extends from the bottom of the housing towards the top of the housing;

[0017] - The discharge port is in communication with the housing via a plurality of discharge pipes leading to the housing;

[0018] - The device includes a piston that is movable so as to compress the fluid in the first compression chamber and in the second compression chamber during alternating opposite movements;

[0019] - The container contains a bath composed of a cryogenic liquid (such as liquefied hydrogen).

[0020] The present invention also relates to a method for pumping cryogenic fluids using such a device, wherein the container houses a bath of liquefied cryogenic fluid, the method comprising the steps of allowing liquid to enter the first compression chamber via an inhalation system and compressing the fluid in the second compression chamber, and then allowing the fluid to enter the second compression chamber via a transfer system and compressing the fluid in said first compression chamber, during which excess fluid is discharged from said first compression chamber to said bath via a discharge port and at least one retarder.

[0021] The present invention may also relate to any alternative device or method comprising any combination of the above or following features falling within the scope of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Further specific features and advantages will become apparent by reading the following description with reference to the drawings.

[0023] The present invention will be better understood by reading the following description, which is given by way of example only and with reference to the drawings, in which:

[0024] Figure 1 is a schematic partial vertical cross-sectional view showing a first exemplary embodiment of a device according to the present invention;

[0025] Figure 2 is a schematic partial vertical cross-sectional view showing a second exemplary embodiment of a device according to the present invention;

[0026] Figure 3 is a schematic partial vertical cross-sectional view showing a third exemplary embodiment of a device according to the present invention;

[0027] Figure 4 is a schematic partial vertical cross-sectional view showing a fourth exemplary embodiment of a device according to the present invention;

[0028] Figure 5 is a schematic partial vertical cross-sectional view showing a fifth exemplary embodiment of a device according to the present invention;

[0029] Figure 6 is a schematic partial vertical cross-sectional view showing a sixth exemplary embodiment of a device according to the present invention. DETAILED DESCRIPTION

[0030] In all the drawings, the same reference numerals refer to the same elements.

[0031] In this detailed description, the following embodiments are examples. Although the description refers to one or more embodiments, this does not mean that these features are applicable only to a single embodiment. The various features of different embodiments can also be combined and / or interchanged to provide other embodiments.

[0032] Figure 1 The fluid compression device 1 shown includes two compression stages in series.

[0033] In particular, the device 1 includes a first compression chamber 3 (compressed at a relatively low pressure) and a second compression chamber 4 (at a relatively high pressure).

[0034] The device 1 includes a suction system 2 in communication with the first compression chamber 3, the suction system 2 being configured to allow the fluid (liquid) to be compressed to enter the first compression chamber 3.

[0035] The suction system 2 includes, for example, at least one of the following: 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 to be compressed to enter the first compression chamber 3 during the suction phase and prevents the fluid from leaving during the compression phase.

[0036] In particular, the suction system 2 (valves and / or the like) can be configured to open in the presence of a given pressure difference between its two ends. Additionally, possibly, the first compression chamber 3 can be equipped with a pressure relief valve or other safety element configured to limit the pressure in the chamber below a given safety threshold.

[0037] As shown, the second compression stage (which has the second compression chamber 4) does not have to be immersed in the liquid bath 16; it can be partially or entirely located above the bath 16. Preferably, the first compression stage (which has the first compression chamber 3) does not have to be immersed in the liquid bath 16; at least the suction system is immersed or connected to the liquid bath.

[0038] The device 1 further includes a check transfer system 6 that is in communication with the first compression chamber 3 and the second compression chamber 4 and is configured to allow the fluid compressed in the first compression chamber 3 to be transferred to the second compression chamber 4 (during and / or at the end of the fluid compression phase in the first compression chamber 3), but remains closed during the compression phase in the second compression chamber 4. The check transfer system 6 can be of the same type as the suction system 2.

[0039] The device 1 can include a piston that is capable of translating in an alternating motion (actuated by a drive member) to compress the fluid in the first compression chamber 3 and the second compression chamber 4. For example, the compression motion in one chamber simultaneously ensures the entry into the other chamber (or vice versa).

[0040] The device 1 further includes a discharge orifice 7 that communicates with the second compression chamber 4 and is configured to allow the high-pressure compressed fluid to leave the second compression chamber 4 (during or at the end of the compression phase in the second compression chamber 4). The discharge orifice 7 may be provided with a check system that may be of the same type as the suction system 2 (e.g., the check system closes as long as the pressure difference between the second compression chamber 4 and the outside is below a given threshold).

[0041] The device 1 may include a compressed gas discharge pipe that includes a first lower end connected to the discharge orifice 7 and a second upper end located in the upper part of the device 1 for collecting the compressed high-pressure fluid.

[0042] Preferably, the first compression chamber 3 is configured to urge the gas to escape via a port or valve.

[0043] For example, one or more ports and / or orifices (not shown) may be formed in any part of the wall that defines at least a part of the first compression chamber 3. These ports may be provided such that during the suction phase (when the first compression chamber 3 expands), any gas that may be present in the first compression chamber 3 can escape via these ports and make room for the liquid from the surrounding bath. This ensures that the liquid completely fills the chamber during suction. Additionally, during the compression phase, these ports may allow the excess liquid to flow out, thereby metering the volume of liquid that will be trapped therein (the volume may be determined by the position of the ports).

[0044] As shown in the figure, the compression device 1 may include a thermally insulating and sealed housing 13 for a bath 16 containing a cryogenic cooling fluid. In particular, the first compression chamber 3 and optionally the second compression chamber 4 may be immersed in the liquid phase. The upper part of the housing 16 may have a gas headspace that collects any leaks in the device 1.

[0045] The compression device 1 further includes a discharge port that allows fluid communication between the first compression chamber 3 and the bath 16 and is configured to let the excess liquid trapped in the first compression chamber 3 leave during compression in the first compression chamber 3.

[0046] Preferably, a discharge valve 9 is provided to control the discharge of the liquid via the discharge port and prevent fluid from entering the compression chamber 3 via the discharge port.

[0047] As shown in the figure, the discharge port communicates with the housing 13 via at least one flow retarder 10 that is configured to attenuate the velocity and / or intensity of the discharged liquid flow by breaking up the jet and using a relatively large discharge surface.

[0048] Preferably, the retarder 10 is configured to reduce the effect of the pressure drop caused by the violent impact or dispersion or friction resulting from the violently discharged jet. The retarder "breaks" this jet.

[0049] This retarder 10 produces a flowing non - sudden discharge, which loses velocity but converts the velocity into pressure rather than a pressure drop.

[0050] This limits the friction or possible splashing of the liquid towards the hot areas of the suction bath wall that would cause the liquid to vaporize.

[0051] The flow retarder 10 may include, for example, a nozzle made of a porous material, see Figure 1 , Figure 2 , Figure 3 and Figure 4 . For example, the porous sintered material may include: a sintered product made of bronze or stainless steel, which is, for example, cylindrical or conical in shape. The length may be in the range of 15 mm to 450 mm. The diameter may be in the range of 10 mm to 80 mm. The permeability may be greater than 5 darcies (>5 D), where 1 darcy is equal to 10 -12 m 2 .

[0052] This enables the "breaking" of the discharged jet without a pressure drop, while reducing the contact of the nearly saturated liquid with the potentially hotter parts of the bath 16 or the vapor.

[0053] As shown, the discharge port may communicate with the housing 13 via at least one discharge pipe 11 (two in the example shown) leading to the housing 13. Each pipe 11 may be provided with a retarder 10 respectively.

[0054] The one or more discharge pipes 11 may extend as follows:

[0055] - Horizontally and, for example, lead to the lower part of the container / housing 13 in the liquid bath;

[0056] - Horizontally and then vertically upward, and, for example, lead to the lower part of the container in the liquid bath, see Figure 3 ;

[0057] - Horizontally and then vertically, and, for example, open at the junction between the liquid bath and the gas headspace;

[0058] - Horizontally and then vertically, and, for example, lead to the gas headspace above the liquid bath, see Figure 1 and Figure 2 .

[0059] The retarder 10 is preferably provided at the downstream end of the discharge pipe 11 (in the container / in the bath).

[0060] Thus, as shown, the ends of the discharge pipes 11 may be oriented upward or downward or horizontally.

[0061] In particular, the one or more discharge pipes 11 can be vertically oriented to reduce the contact between potential bubbles and the liquid of the bath 16. Thus, when the liquid is injected into the liquid phase, the bubbles are directed to the top of the bath and thus to the gas headspace.

[0062] In the case of discharging into the gas section, the discharged liquid stream can flow out and be slowly injected into the liquid phase. Thus, the heat exchange between the liquid phase and the gas phase is limited. As shown, the two discharge pipes 11 can be connected to the same discharge valve 9 via a common chamber.

[0063] In Figure 4 a variant of, the retarder 10 comprises a tube having a porous surface or consists of a tube having a porous surface, which tube extends vertically in the container / housing 13.

[0064] In Figure 5 a variant of, the retarder 10 comprises a tube perforated with a plurality of orifices or consists of a tube perforated with a plurality of holes to allow the liquid to flow out. For example, the size of the orifices is in the range of 0.05 mm to 1 mm.

[0065] In Figure 6 a variant of, the retarder 10 comprises a tube perforated with a plurality of orifices or consists of a tube perforated with a plurality of orifices, which is arranged in a serpentine manner around at least one of the two compression chambers.

[0066] The present invention is particularly advantageous for pumping hydrogen, for example in order to generate a very high-pressure hydrogen stream (for example at a pressure in the range of 100 bar to 1000 bar) at the outlet of the second compression stage.

Claims

1. A fluid compression device (1) having multiple compression stages, the fluid compression device comprising: A sealed housing (13) for a bath (16) designed to contain a cryogenic fluid having a liquid phase, an upper portion of the housing (13) being designed to contain a gas headspace; a first compression chamber (3); a second compression chamber (4); an intake system (2) in communication with the first compression chamber (3) and configured to allow fluid to enter the first compression chamber (3); a transfer system (6) in communication with the first compression chamber (3) and the second compression chamber (4) and configured to allow fluid pre-compressed in the first compression chamber (3) to be transferred to the second compression chamber (4), the device (1) further including a discharge orifice (7) in communication with the second compression chamber (4) and configured to allow fluid compressed in the second compression chamber to leave, wherein the intake system (2) includes one or more valves (2) configured to ensure that the fluid to be compressed enters the first compression chamber (3) during the intake phase and to prevent the fluid from leaving during the compression phase, the device (1) further including a discharge port that allows communication between the first compression chamber (3) and the bath (16) so that excess liquid trapped in the first compression chamber (3) leaves during compression of the fluid in the first compression chamber (3). It is characterized in that the device has a discharge valve (9) configured to control the discharge of liquid via the discharge port and to prevent fluid from entering the first compression chamber (3) via the discharge port, the discharge port being in communication with the housing (13) via at least one flow retarder (10) configured to attenuate the velocity and / or intensity of the discharged liquid flow by restricting the pressure drop of the discharged liquid flow.

2. The device according to claim 1, wherein The flow retarder (10) includes at least one of the following: a set of diffuser holes; a nozzle made of a porous material, preferably having a permeability greater than 5 darcies.

3. The device according to claim 1 or 2, characterized in that, The flow retarder (10) includes a nozzle made of a porous sintered material, such as bronze or stainless steel, preferably the nozzle made of a porous sintered material being cylindrical or conical.

4. The device according to any one of claims 1 to 3, characterized in that The length of the flow retarder (10) is in the range of 15 mm to 450 mm, and preferably, the diameter of the flow retarder is in the range of 10 mm to 80 mm.

5. The device according to any one of claims 1 to 4, characterized in that The discharge port is in communication with the housing (13) via at least one discharge pipe (11) leading to the housing (13), the at least one discharge pipe being located in the bath (16) so as to be in the bath of the housing (13) and / or above the liquid level of the bath of the housing (13).

6. The device according to claim 5, characterized in that, The discharge pipe (11) has a portion extending into the housing (13) parallel to and / or transverse to the vertical direction.

7. The device according to claim 5 or 6, characterized in that, The discharge pipe (11) extends from the bottom of the housing (13) towards the top of the housing (13).

8. The device according to any one of claims 5 to 7, characterized in that The discharge port is in communication with the housing (13) via a plurality of discharge pipes (11) leading to the housing (13).

9. The device according to any one of claims 1 to 8, characterized in that, The device includes a piston that is movable to compress the fluid in the first compression chamber (3) and in the second compression chamber (4) during alternating opposite movements.

10. The device according to any one of claims 1 to 9, characterized in that, The housing accommodates a bath constituted by a cryogenic liquid, such as liquefied hydrogen for example.

11. A method of pumping a cryogenic fluid using the apparatus according to any one of claims 1 to 10, wherein, The housing (13) accommodates a bath of liquefied cryogenic fluid, the method including the step of causing the liquid to enter the first compression chamber (3) via an intake system (2) and the step of compressing the fluid in the second compression chamber (4), and then the step of causing the fluid to enter the second compression chamber (4) via a transfer system (6) and the step of compressing the fluid in the first compression chamber (3), during the step of compressing the fluid in the first compression chamber (3), the excess fluid being discharged from the first compression chamber (3) to the bath via a discharge port and at least one flow retarder (10).

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