Apparatus and method for fluid compression

Abstract

The invention relates to a fluid compression apparatus (1) comprising a sealed enclosure (13) for containing a cryogenic fluid bath (16), a first (3) and a second compression chamber (4), an inlet system (2) for the first chamber (3), a transfer system (6) from the first (3) to the second (4) chamber, the apparatus (1) further comprising a communicating discharge port (7) for the outlet of compressed fluid from the second chamber, the apparatus (1) further comprising a discharge port equipped with a valve (9) for the discharge of the first compression chamber (3) into the bath (16) to allow excess liquid to escape during fluid compression in the first chamber (3), the discharge port communicating with the enclosure (13) via at least one flow restrictor (10) configured to attenuate the velocity and / or intensity of the discharged liquid flow by limiting its pressure drop. Abstract figure: Fig. 1

Description

Title of the invention: Apparatus and method for fluid compression

[0001] The invention relates to a device and a method for compressing fluid.

[0002] The invention relates more particularly to a multi-stage fluid compression apparatus comprising a sealed enclosure intended to contain a cryogenic fluid bath comprising a liquid phase, the upper part of the enclosure being intended to contain a gaseous head, a first compression chamber, a second compression chamber, an inlet system communicating with the first compression chamber configured to allow the entry of fluid into said first compression chamber, a transfer system communicating with the first and second compression chambers and configured to allow the transfer of pre-compressed fluid from the first compression chamber to the second compression chamber, the apparatus further comprising an outlet communicating with the second compression chamber and configured to allow the outlet of compressed fluid from the second compression chamber,wherein the inlet system comprises one or more valves configured to ensure the entry of fluid to be compressed into the first compression chamber during an inlet phase and to prevent the exit of fluid during the compression phase, the apparatus further comprising a discharge port allowing communication between the first compression chamber and the bath to allow excess liquid trapped in the first compression chamber to escape during fluid compression in the first compression chamber.

[0003] To increase the performance and volumetric efficiency of liquid hydrogen pumps, it is essential to have good thermodynamic quality of the inlet liquid. This is to prevent cavitation due to pressure drop and thermal ingress. The high-pressure compression of the liquid drawn from a reservoir containing the pump (bath or "sump") is often preceded by a first compression (or pre-compression) stage. This pre-compression is generally a compression stage with a lower ratio than the second compression stage. This first compression stage draws in nearly saturated liquid at the saturation temperature of the bath and mechanically subcools it by pressurization to ensure proper filling without "flash" vaporization at the compression stage.

[0004] In particular, where the two compression stages are carried out by opposite movements of the same piston, the filling phase of the second compression stage therefore takes place at the same time as the compression in the first stage.

[0005] Since the diameters of the chambers are different but the piston stroke is identical, the Swept volumes can therefore be different (typically the volume of the first stage is larger than that of the second stage). Assuming that the fluid density remains relatively constant (due to low compressibility in the absence of flash vaporization) during admission into the second stage, it may be essential to vent some of the pressurized liquid from the first compression chamber.

[0006] It is known to provide lights or channels connecting the first compression chamber and the bath to naturally evacuate this excess fluid to the bath.

[0007] This evacuation of excess liquid from the first compression stage can generate vaporization gas in the bath.

[0008] One object of the present invention is to overcome all or part of the disadvantages of the prior art noted above.

[0009] To this end, the device according to the invention, which also conforms to the generic definition given in the preamble above, is essentially characterized in that it includes an evacuation valve configured to control the evacuation of liquid via the evacuation orifice and to prevent the entry of fluid into the first compression chamber via the evacuation orifice, the evacuation orifice communicating with the enclosure via at least one flow restrictor configured to attenuate the speed and / or intensity of the evacuated liquid flow by limiting its pressure loss.

[0010] Furthermore, embodiments of the invention may include one or more of the following features: - the flow restrictor comprises at least one of the following: a set of diffusion holes, a nozzle made of porous material with a permeability preferably greater than five darcy, - the flow restrictor comprises at least one of the following: a nozzle made of porous sintered material, for example bronze or stainless steel, preferably cylindrical or conical in shape, - the speed bump has a length between 15mm and 450mm and a diameter preferably between 10mm and 80mm, - the drain outlet communicates with the enclosure via at least one drain pipe opening into the enclosure within the bath, and is located in and / or above the liquid level of the bath in the enclosure. - the exhaust duct includes a portion extending within the enclosure parallel to the vertical direction and / or transversely to the vertical direction, - The exhaust duct extends from the bottom to the top of the enclosure, - The exhaust outlet communicates with the enclosure via several exhaust ducts opening into the enclosure. - The device includes a movable piston to ensure fluid compression in the first and second compression chambers during alternating opposing movements, - the container contains a bath made up of cryogenic liquid, for example liquefied hydrogen.

[0011] The invention also relates to a cryogenic fluid pumping method using such an apparatus in which the container contains a bath of liquefied cryogenic fluid, the method comprising, a liquid admission step into the first compression chamber via the admission system and a fluid compression step in the second compression chamber, then, a fluid admission step into the second compression chamber via the transfer system and a fluid compression step in the first compression chamber during which excess fluid is evacuated from the first compression chamber to the bath via the discharge port and at least one retarder.

[0012] The 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] Other features and advantages will become apparent from the following description, given with reference to the figures in which: Brief description of the figures

[0014] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which:

[0015] [Fig-1] is a schematic and partial vertical cross-sectional view, illustrating a first example of an embodiment of a device according to the invention,

[0016] [Fig.2] is a schematic and partial vertical cross-sectional view illustrating a second embodiment of a device according to the invention,

[0017] [Fig.3] is a schematic and partial vertical cross-sectional view illustrating a third embodiment of a device according to the invention,

[0018] [Fig.4] is a schematic and partial vertical cross-sectional view illustrating a fourth embodiment of an apparatus according to the invention,

[0019] [Fig.5] is a schematic and partial vertical cross-sectional view illustrating a fifth embodiment of an apparatus according to the invention,

[0020] [Fig. 6] is a schematic and partial vertical cross-sectional view illustrating a sixth embodiment of an apparatus according to the invention. Detailed description

[0021] In all figures, the same references refer to the same elements.

[0022] In this detailed description, the following are examples. The fact that the description refers to one or more embodiments does not mean that the features apply only to a single embodiment. Simple features from different embodiments can also be combined and / or interchanged to provide other embodiments.

[0023] The fluid compression device 1 shown in [Fig.1] comprises two compression stages in series.

[0024] The device 1 includes in particular a first compression chamber 3 (relatively low pressure compression) and a second compression chamber 4 (relatively high pressure).

[0025] The apparatus 1 includes an intake system 2 communicating with the first compression chamber 3 and which is configured to allow the entry of fluid (liquid) to be compressed into said first compression chamber 3.

[0026] The intake system 2 includes, for example, at least one of the following: one or more check valves, one or more orifices or light(s), at least one flat disc valve or any other device or valve allowing the entry of fluid to be compressed into the first compression chamber 3 during an intake phase and preventing the exit of fluid during the compression phase.

[0027] In particular, this inlet system 2 (valve(s) and / or other) can be configured to open in the event of a predetermined pressure differential between its two ends. Furthermore, the first chamber 3 can optionally be equipped with a valve or other safety element configured to limit the pressure within the chamber below a predetermined safety threshold.

[0028] As illustrated, the second compression stage (with the second compression chamber 4) is not necessarily immersed in the liquid bath 16; it may be partially or totally above the bath 16. Preferably, the first compression stage (with the first compression chamber 3) is not necessarily immersed in the liquid bath 16; at least the intake system is immersed in or connected to the liquid bath.

[0029] The device 1 also includes a non-return transfer system 6 communicating with the first 3 and second 4 compression chambers and configured to allow the transfer of compressed fluid from the first 3 compression chamber to the second 4 compression chamber (during and / or at the end of the fluid compression phase in the first 3 compression chamber) but which remains closed during the compression phase in the second 4 compression chamber. This transfer system 6 may be of the same type as that of the inlet system 2.

[0030] The apparatus 1 may include a piston 5 that moves in translation (driven by a motor) in a reciprocating motion to ensure the compression of the fluid in the first 3 and second 4 compression chambers. For example, the movement compression in one chamber simultaneously ensures admission into the other chamber (and vice versa).

[0031] The device 1 further includes a discharge port 7 communicating with the second compression chamber 4 and configured to allow the outlet of high-pressure compressed fluid from the second compression chamber 4 (during or at the end of the compression phase in this chamber 4). The discharge port 7 may be provided with a non-return system which may be of the same type as that of the inlet system 2 (for example, closed as long as the pressure differential between the second compression chamber 4 and the outside is below a predetermined threshold).

[0032] The device 1 may include a compressed gas discharge line comprising a first lower end connected to this discharge port 7 and a second upper end located in the upper part of the device 1 to collect the compressed high-pressure fluid.

[0033] Preferably, the first compression chamber 3 is configured to promote the escape of gas through the ports or valves.

[0034] For example, one or more openings and / or ports (not shown) may be provided in any portion of the wall delimiting at least part of the first compression chamber 3. These openings may be designed so that, during the admission phase (expansion of chamber 3), any gas present in the first compression chamber 3 can escape through these openings and be replaced by liquid from the surrounding bath. This ensures complete liquid filling at the admission stage. Furthermore, during the compression phase, these openings can release excess liquid by controlling the volume of liquid trapped within them (this volume can be determined by the position of the openings 26).

[0035] As illustrated, the compression apparatus 1 may include a thermally insulated, sealed enclosure 13 containing a cryogenic cooling fluid bath 16. In particular, the first compression chamber 3 and optionally the second compression chamber 4 may be immersed in a liquid phase. The upper part of the enclosure 16 may include a gaseous vent that collects any leaks in the apparatus 1.

[0036] The compression device 1 further includes an evacuation orifice allowing fluidic communication between the first compression chamber 3 and bath 16 and configured to allow excess liquid trapped in the first compression chamber 3 to exit during compression in the first compression chamber 3.

[0037] A drain valve 9 is preferably provided to control the evacuation of liquid via the drain port and to prevent the entry of fluid into the compression chamber 3 via the drain port.

[0038] As illustrated, the discharge port communicates with the enclosure 13 via at least one flow restrictor 10 configured to attenuate the speed and / or intensity of the discharged liquid flow by breaking the jet and using a relatively large discharge area.

[0039] The retarder 10 is preferably configured to reduce the effect of pressure losses generated by diffusion or friction or violent shocks due to vigorous discharged jets. The retarder "breaks" such jets.

[0040] Such a retarder 10 produces a non-abrupt evacuation of the flow which loses its speed but which converts the speed into pressure rather than into pressure loss.

[0041] This limits friction or possible splashing of liquid towards hot areas of the suction bath wall which could cause its evaporation.

[0042] The flow restrictor 10 may include, for example, a nozzle made of porous material (see [Fig. 1], [Fig. 2], [Fig. 3], and [Fig. 4]). For example, porous sintered materials may include: a bronze or stainless steel sinter, for example, cylindrical or conical in shape. The length may be between 15 mm and 450 mm. The diameter may be between 10 mm and 80 mm. The permeability may be greater than five darcy (>5D), one darcy being equal to 10¹² m².

[0043] This allows the discharged jet to be "broken" without pressure loss while reducing the contact of the near-saturated liquid with potentially hotter parts or vapor of the bath 16.

[0044] As illustrated, the discharge port can communicate with the enclosure 13 via at least one discharge conduit 11 (two in the illustrated examples) opening into the enclosure 13. Each conduit 11 can be provided with a retarder 10.

[0045] The discharge conduit(s) 11 may extend: - horizontally and open, for example, at the bottom of container 13, into the liquid bath, - horizontally then vertically upwards, uncork for example at the bottom of the container, in the liquid bath cf. [Fig.3], - horizontally then vertically, opening, for example, at the junction between the liquid bath and the gaseous space, - horizontally then vertically and open out for example above the liquid bath and the gaseous sky cf. [Fig.1] and [Fig.2].

[0046] The retarder 10 is preferably provided at the downstream end of the discharge conduit 11 (in the container / bath).

[0047] Thus, as illustrated, the ends of the evacuation conduits 10 can be oriented upwards or downwards or horizontally.

[0048] In particular, it is possible to orient the evacuation conduit(s) 10 vertically in order to reduce the contact between potential bubbles and the liquid in the bath 16. In this way the bubbles tend to rise to the top of the bath and therefore towards the gaseous sky while the liquid flows into the liquid phase.

[0049] In the case of discharge into the gaseous phase, the discharged liquid can trickle down and slowly flow into the liquid phase. In this way, heat exchange between the liquid and gaseous phases is limited. As illustrated, the two discharge conduits 11 can be connected to the same discharge valve 9 via a common chamber.

[0050] In the variant of [Fig.4] the retarder 10 comprises or is made up of a tube with a porous surface which extends vertically into the container 13.

[0051] In the variant of [Fig. 5], the retarder 10 comprises or is made up of a tube perforated with a multitude of orifices to allow the liquid to flow through. For example, the orifices have dimensions between 0.05 mm and 1 mm.

[0052] In the variant of [Fig.6], the retarder 10 comprises or is made up of a tube pierced with a multitude of orifices arranged in a serpentine pattern around at least one of the two compression chambers.

[0053] The invention is particularly advantageous for hydrogen pumping, for example for producing a very high pressure hydrogen flow at the outlet of the second compression stage (pressure between 100 and 1000 bar for example).

Claims

Demands

1. A multi-stage fluid compression apparatus (1) comprising a sealed enclosure (13) for containing a cryogenic fluid bath (16) having a liquid phase, the upper part of the enclosure (13) being for containing a gaseous head, a first compression chamber (3), a second compression chamber (4), an inlet system (2) communicating with the first compression chamber (3) configured to permit the entry of fluid into said first compression chamber (3), a transfer system (6) communicating with the first (3) and second (4) compression chambers and configured to permit the transfer of pre-compressed fluid from the first compression chamber (3) to the second (4) compression chamber,the apparatus (1) further comprising an outlet (7) communicating with the second compression chamber (4) and configured to allow the outlet of compressed fluid in the second compression chamber, wherein the inlet system (2) comprises one or more valves (2) configured to ensure the entry of fluid to be compressed into the first compression chamber (3) during an inlet phase and to prevent the outlet of fluid during the compression phase, the apparatus (1) further comprising an outlet allowing communication between the first compression chamber (3) and bath (16) to allow excess liquid trapped in the first compression chamber (3) to exit during fluid compression in the first compression chamber (3),the device (1) being characterized in that it comprises a discharge valve (9) configured to control the discharge of liquid via the discharge orifice and to prevent the entry of fluid into the first compression chamber (3) via the discharge orifice, the discharge orifice communicating with the enclosure (13) via at least one flow restrictor (10) configured to attenuate the speed and / or intensity of the discharged liquid flow by limiting its pressure loss.

2. Apparatus according to claim 1, characterized in that the flow retarder (10) comprises at least one of: a set of diffusion holes, a nozzle made of porous material having a permeability preferably greater than five darcy.

3. Apparatus according to claim 1 or 2, characterized in that the flow restrictor (10) comprises at least one of the following: a nozzle made of porous sintered material, for example bronze or stainless steel, preferably cylindrical or conical in shape.

4. Apparatus according to any one of claims 1 to 3, characterized in that the retarder (10) has a length between 15mm and 450mm and a diameter preferably between 10mm and 80mm.

5. Apparatus according to any one of claims 1 to 4, characterized in that the discharge orifice communicates with the enclosure (13) via at least one discharge conduit (11) opening into the enclosure (13) into the bath (16) to be located in and / or above the liquid level of the bath in the enclosure (13).

6. Apparatus according to claim 5, characterized in that the discharge conduit (11) comprises a portion extending into the enclosure (13) parallel to the vertical direction and / or transversely to the vertical direction.

7. Apparatus according to claim 5 or 6, characterized in that the discharge conduit (11) extends from the bottom to the top of the enclosure (13).

8. Apparatus according to any one of claims 5 to 7, characterized in that the discharge orifice (8) communicates with the enclosure (13) via several discharge conduits (11) opening into the enclosure (13).

9. Apparatus according to any one of claims 1 to 8, characterized in that it comprises a movable piston to ensure the compression of the fluid in the first (3) and second (4) compression chambers during alternating opposite movements.

10. Apparatus according to any one of claims 1 to 9, characterized in that the container contains a bath made of cryogenic liquid, for example liquefied hydrogen.

11. A cryogenic fluid pumping method using an apparatus according to any one of claims 1 to 10 in which the container (13) contains a bath of liquefied cryogenic fluid, the method comprising, a liquid admission step into the first compression chamber (3) via the admission system (2) and a fluid compression step into the second compression chamber (4), then, a fluid admission step into the second compression chamber (4) via the transfer system (6) and a fluid compression step into the first compression chamber (3) during which excess fluid is evacuated from the first compression chamber (3) to the bath via the discharge orifice (8) and at least one retarder (10).

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