Integrated expander generator for hydrogen applications with magnetic bearings

Abstract

A hydrogen-expansion generator machine (100) for hydrogen use has a machine inlet (111) and a machine outlet (112), and includes an impeller (110) that expands hydrogen and is directly connected to a generator (120), and at least one magnetic bearing (130) that is cooled by a hydrogen flow taken in from the machine inlet (111). The expander generator machine (100) is located inside a casing (140), and preferably, hydrogen flows through an appropriate path inside the casing (140) to cool at least one magnetic bearing (130). Advantageously, the generator (120) is also cooled by the hydrogen flow taken in from the machine inlet (111).

Description

Technical Field

[0001] The subject matter disclosed herein relates to a hydrogen expander generator with magnetic bearings. More specifically, the subject matter disclosed herein relates to an integrated expander generator that enables the use of magnetic bearings and, optionally, hydrogen as a cooling fluid for the generator.

Background Art

[0002] A hydrogen expander generator is a rotary machine that expands a fluid through an impeller to release expansion work that drives the impeller to rotate. Typically, the impeller is mechanically coupled to a transmission mechanism that transfers the rotation to the shaft of the generator, thus generating electrical energy. When both the impeller and the generator are housed within a common casing, it is called an integrated machine.

[0003] Hydrogen applications are becoming increasingly important in the energy revolution. However, there are several drawbacks and potential risks associated with the use of hydrogen in rotary machines, specifically in expander generators. For example, the Chinese Patent Publications Nos. 113374538A and 113374581A aim to overcome the problem of hydrogen leakage in expander generators for hydrogen applications, which can pose an explosion risk due to the low critical ignition energy of hydrogen. According to these documents, a rotary seal (such as a seal generated by a dry gas seal) is established between the rotating shaft and the casing by using an inert isolation gas such as nitrogen. Furthermore, it is known from the Chinese Patent Publication No. 113513580A to use a lubrication system to lubricate a reduction box located between the hydrogen expander and the generator, and the reduction box reduces the rotational speed of the shaft of the generator and typically meets the rotational speed requirements of mechanical bearings and other rotary machine components.

[0004] However, it is desirable to have a safe high-speed rotating machine that does not require the introduction of operating gas and / or liquid (such as seal gas or lubrication).

Summary of the Invention

[0005] According to one aspect, the subject matter disclosed herein is an expander generator machine that receives hydrogen from a machine inlet and discharges the expanded hydrogen to a machine outlet, comprising an impeller mechanically connected to a generator, and further comprising at least one magnetic bearing cooled by a hydrogen stream taken in from the machine inlet. The expander generator machine is located inside a casing. According to some embodiments, the hydrogen stream taken in from the machine inlet flows through an appropriate path inside the casing to cool at least the magnetic bearing. Advantageously, the generator is also cooled by the hydrogen stream taken in from the machine inlet. According to some embodiments, hydrogen is used only to cool the generator and not for cooling the magnetic bearing.

Brief Description of the Drawings

[0006] Many of the disclosed embodiments of the present invention, and the attendant advantages thereof, will be better understood and readily appreciated when considered in connection with the accompanying drawings, by reference to the following detailed description of the invention for carrying out the invention.

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Embodiments for Carrying Out the Invention

[0007] According to one aspect, the subject matter disclosed herein relates to a rotating machine for generating electrical energy by expanding hydrogen through an impeller that rotates by the energy released during the expansion of hydrogen. The impeller receives hydrogen from a machine inlet, the hydrogen is expanded by the impeller as it flows through the impeller blades, and the finally expanded hydrogen is discharged to a machine outlet. The impeller is directly connected to the shaft of a generator having a rotating part integral with the shaft and a stator part integral with the casing, and generates electrical energy by the rotation of the shaft that generates a rotating magnetic field. A first portion of the hydrogen supplied to the machine inlet is deflected and used to cool at least one magnetic bearing (which can be a radial bearing or a thrust bearing) acting on the shaft, and then is advantageously sent to the machine outlet to be expanded by the impeller and mixed with the discharged hydrogen. Advantageously, a second portion of the hydrogen supplied to the machine inlet is deflected and used to cool the generator. It should be noted that according to some embodiments, the first portion of the hydrogen used to cool at least one magnetic bearing and the second portion of the hydrogen used to cool the generator can be the same hydrogen stream.

[0008] Next, embodiments of the present disclosure will be described in detail, and examples thereof are illustrated in the drawings. The examples and the drawings are provided as an explanation of the present disclosure and should not be construed as limiting the present disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the scope or spirit of the present disclosure. In the following description, like reference numerals are used in the illustration of the embodiments of the figures to indicate elements that perform the same or similar functions. Further, for the sake of clarity of illustration, some reference numerals may not be repeated in all the figures.

[0009] Figure 1 schematically shows a first embodiment of an innovative expander generator machine, generally designated by reference numeral 100 (hereinafter referred to as "expander generator"). Further, for clarity, in Figure 1 (and generally all figures), the circulation of hydrogen within the very schematic expander generator is emphasized (see the numerous black arrows in the figure). Note that other fluids can circulate within the expander generator (as will be described below). Typically, and without limitation, referring to Figure 1, the expander generator 100 has a machine inlet 111 and a machine outlet 112, and includes an impeller 110 configured to expand hydrogen and a generator 120 configured to generate electrical energy, with both the impeller 110 and the generator 120 housed within a casing 140.

[0010] The impeller 110, specifically a radial inflow turbine, receives the compressed hydrogen supplied to the inlet 111 of the machine, expands it, and is configured to release expansion work. For example, in Figure 1, two machine inlets 111 are shown, located on opposite sides of the central axis A of the expander generator 100. Specifically, the impeller 110 has a plurality of impeller blades that define a plurality of passages through which the hydrogen flows, expands, and is then discharged as expanded hydrogen at the machine outlet 112. Thus, the hydrogen supplied to the impeller 110 reduces in pressure and temperature from the inlet 111 to the outlet 112 of the machine. Typically, the compressed hydrogen supplied to the machine inlet 111 is already at a very low temperature, such as -230°C to -150°C.

[0011] As already mentioned above, the expansion of hydrogen through the impeller 110 releases expansion work that can drive the impeller 110. Referring to Figure 1 without limitation, the impeller 110 is mechanically connected, preferably directly (i.e., without further elements therebetween), to a generator 120 that is preferably a permanent magnet generator.

[0012] More specifically, the generator 120 includes a rotating hub 121 and a rotating magnetic assembly 122 mechanically coupled to the rotating hub 121, and the impeller 110 is mechanically connected to the rotating hub 121 of the generator 120. Specifically, the rotating hub 121 has a cylindrical shape and includes a recess, typically a tubular recess located on the outer surface of the rotating hub 121, and the recess houses the rotating magnetic assembly 122, preferably a permanent magnet rotating magnetic assembly.

[0013] The generator 120 further includes a stationary magnetic assembly 123 disposed around (i.e., facing) the rotating magnetic assembly 122 and preferably including an electromagnet. Advantageously, the stationary magnetic assembly 123 and the rotating magnetic assembly 122 define a gap therebetween. As will be more clearly explained below, according to one or more embodiments, the expander generator 100 may further include a cooling system configured to circulate a cooling fluid to cool the rotating magnetic assembly 122 and / or the stationary magnetic assembly 123 of the generator 120. Specifically, the cooling fluid may circulate within the gap between the rotating magnetic assembly 122 and the stationary magnetic assembly 123.

[0014] Referring non - limitingly to FIG. 1, the expander generator 100 further includes at least one magnetic bearing 130 that acts on, specifically supports, the rotating hub 121. According to the embodiment of FIG. 1, the at least one magnetic bearing 130 is a radial magnetic bearing. Preferably, the at least one magnetic bearing 130 is located between the impeller 110 and the rotating magnetic assembly 122 and the stationary magnetic assembly 123 of the generator 120. Note that the casing 140 further houses the at least one magnetic bearing 130. Specifically, the rotating element of the at least one magnetic bearing 130 is integral with the rotating hub 121, and the stator element of the at least one magnetic bearing 130 is integral with the casing 140.

[0015] As shown in FIG. 1, at least one magnetic bearing 130 is fluidly connected to the machine inlet 111 and is configured to be cooled by a hydrogen flow taken in from the machine inlet 111. In other words, a part of the hydrogen supplied to the machine inlet 111 cannot be expanded by the impeller 110, but is supplied to at least one magnetic bearing 130 to cool the bearing. Specifically, hydrogen can flow through at least the gap between the rotating element and the stator element of at least one magnetic bearing 130. It should be noted that a part of the hydrogen used to cool at least one magnetic bearing 130 can be defined as "small" when compared with the amount of hydrogen expanded by the impeller 110.

[0016] Referring non - limitingly to FIG. 1, the expander generator 100 further includes a fluid conduit 113 that fluidly connects the machine inlet 111 and at least one magnetic bearing 130. Specifically, the expander generator 100 has one fluid conduit 113 for each machine inlet 111. Advantageously, the fluid conduit 113 is at least partially defined by the back surface of the impeller 110. More advantageously, the fluid conduit 113 is at least partially defined by the back surface of the impeller 110 and the inner wall of the casing 140. In other words, a part of the hydrogen supplied to at least one magnetic bearing 130 flows through the fluid conduit 113. Preferably, one or more seal elements, such as a labyrinth seal and / or a sliding ring seal, are located upstream of at least one magnetic bearing 130. For example, the seal can be located in the fluid conduit 113 or on the rotating hub 121, specifically, between the impeller 110 and at least one magnetic bearing 130. It should be noted that the temperature of the hydrogen downstream of the magnetic bearing 130 is higher than the temperature upstream of the magnetic bearing 130 (and thus can be called "heated hydrogen") due to the heat removed from the bearing. According to the embodiment shown in FIG. 1, the heated hydrogen downstream of the magnetic bearing 130 is discharged outside the casing 140. Advantageously, the hydrogen flows through a dedicated channel defined within the casing 140 that allows the hydrogen to flow outside the casing 140.

[0017] Preferably, the impeller 110 further includes at least one internal channel 114 that fluidly couples the fluid conduit 113 and the impeller blades, thereby equalizing the pressure (and thus the force) acting on the impeller, specifically on the back surface and the front surface of the impeller, i.e., the surface on which the impeller blades are located.

[0018] A second embodiment 200 of the expander generator will be described below with reference to FIG. 2. Note that the elements 210, 211, 212, 213, 214, 220, 221, 222, 223, 230, and 240 in FIG. 2 may be identical or similar to the elements 110 (impeller), 111 (mechanical inlet), 112 (mechanical outlet), 113 (fluid conduit), 114 (internal channel), 120 (generator), 121 (rotating hub), 122 (rotating magnetic assembly), 123 (stationary magnetic assembly), 130 (magnetic bearing), and 140 (casing) in FIG. 1, respectively, and may perform identical or similar functions. Also note that the only difference between FIG. 1 and FIG. 2 is the circulation of hydrogen within the machine, as will become apparent below.

[0019] According to the embodiment of FIG. 2, at least one magnetic bearing 230 (specifically, a radial magnetic bearing) is also fluidly coupled to the mechanical outlet 212, such that the cooling fluid, i.e., hydrogen from the mechanical inlet 211, flows through the fluid conduit 213, removes heat from at least one magnetic bearing 230, and is then discharged to the mechanical outlet 212. In other words, at least one magnetic bearing 230 is configured to discharge the heated hydrogen stream at the outlet 212. Specifically, the heated hydrogen discharged by at least one magnetic bearing 230 is mixed with the expanded hydrogen expanded by the impeller 210 at the mechanical outlet 212 (see the black arrow starting downstream of the radial magnetic bearing 230 and ending at the mechanical outlet 212).

[0020] Note that both the rotating hubs 121 of FIG. 1 and 221 of FIG. 2 are longer than the casings 140 and 240. In other words, the rotating hubs 121 and 221 may terminate outside the casings 140 and 240. As is well known, a rotating shaft or hub is typically advantageously supported by two radial magnetic bearings located at the ends of the rotating shaft or hub, and possibly, the rotating hubs 121 and 221 may be supported by a second bearing (which may be a rotary bearing or a magnetic bearing) located outside the casings 140 and 240.

[0021] A third embodiment 300 of the expander generator will be described below with reference to FIG. 3. Note that the elements 310, 311, 312, 313, 314, 320, 321, 322, 323, 330, and 340 of FIG. 3 may be the same as or similar to the elements 110 (impeller), 111 (mechanical inlet), 112 (mechanical outlet), 113 (fluid conduit), 114 (internal channel), 120 (generator), 121 (rotating hub), 122 (rotating magnetic assembly), 123 (stationary magnetic assembly), 130 (magnetic bearing), and 140 (casing) of FIG. 1, and may perform the same or similar functions.

[0022] According to the embodiment of FIG. 3, the expander generator 300 has two magnetic bearings, specifically, a radial magnetic bearing 330 and a thrust magnetic bearing 331 located downstream of the radial magnetic bearing 330. It should be noted that, according to a possibility not shown in any figure, the positions of the bearings can be swapped (i.e., the thrust magnetic bearing 331 can be located upstream of the radial magnetic bearing 330). Both the magnetic bearings 330 and 331 can be cooled by the compressed hydrogen flow from the machine inlet 311, specifically, they can be cooled in series. As already mentioned, a part of the hydrogen supplied to the machine inlet 311 is, for example, first supplied to the radial magnetic bearing 330 and then to the thrust magnetic bearing 331 to cool them, specifically, flowing through at least the gap between the rotating element and the stator element of the magnetic bearings 330 and 331 (see the small black arrows in FIG. 3). As described above, a part of the hydrogen can flow from the machine inlet 311 through the fluid conduit 313 partially defined by the back surface of the impeller 310 to reach the magnetic bearings 330 and 331. It should be noted that the hydrogen can be pumped by the disk of the thrust magnetic bearing 331 (which can have one or more appropriately shaped pumping surfaces and / or one or more appropriately shaped pumping devices) and discharged radially, for example, from the thrust magnetic bearing 331.

[0023] It should be noted that the temperature of the hydrogen downstream of the magnetic bearings 330 and 331 is higher than the temperature upstream of the magnetic bearings 330 and 331 due to the heat removed from the bearings (therefore, it can be called "heated hydrogen"). Advantageously, the heated hydrogen downstream of the magnetic bearings 330 and 331 is discharged to the outlet 312 and mixed with the hydrogen expanded by the impeller 310.

[0024] According to the embodiment shown in FIG. 3, the rotating magnetic assembly 322, and optionally the stationary magnetic assembly 323, are cooled by a cooling fluid, specifically by a cooling fluid supplied by an external source. It should be noted that this is particularly useful for minimizing the pressure loss of the machine. In fact, the magnetic bearings 330 and 331 can be cooled by a portion of the hydrogen supplied to the machine inlet 311, and the generator 320 can be cooled by one or more cooling fluids that may have a lower pressure than the hydrogen used to cool the magnetic bearings 330 and 331, thus reducing the pressure loss due to cooling. For example, the cooling fluid is configured to be supplied into the casing 340 and circulate within the gap defined between the rotating magnetic assembly 322 and the stationary magnetic assembly 323. However, the stationary magnetic assembly 323 and / or the rotating magnetic assembly 322 can be cooled by a cooling fluid with other suitable circulation configurations. For example, the rotating magnetic assembly 322, and optionally at least partially the stationary magnetic assembly 323 as well, can be cooled by a first cooling fluid that circulates within the gap defined between the rotating magnetic assembly 322 and the stationary magnetic assembly 323, and the stationary magnetic assembly 323 can also be cooled by a second cooling fluid that can circulate inside the stationary magnetic assembly 323, for example.

[0025] Advantageously, the expander generator machine 300 further comprises at least one dry gas seal 341. According to the example shown in FIG. 3, the expander generator machine 300 has two dry gas seals 341 and 342, and the first dry gas seal 341 may be located at the first end of the fixed magnetic assembly 323 and the rotating magnetic assembly 322, specifically, between the first end and the magnetic bearings 330 and 331. The second dry gas seal may be located at the second end of the fixed magnetic assembly 323 and the rotating magnetic assembly 322. According to a variant of the embodiment shown in FIG. 3, the dry gas seal 342 is omitted. According to other possibilities, the dry gas seal 341 may be located elsewhere. Advantageously, the dry gas seal 341 helps to separate the impeller 310 from the generator 320, specifically, to separate the fluid expanded by the impeller (also used to cool the magnetic bearings) from the cooling fluid (used to cool the fixed magnetic assembly and / or the rotating magnetic assembly). Advantageously, the dry gas seal 342 helps to isolate the generator 320 from the environment surrounding the machine, specifically, the environment surrounding the casing 340.

[0026] According to one possibility, the cooling fluid is different from the fluid expanded by the impeller (i.e., hydrogen), for example, air or water. According to another possibility, the cooling fluid is hydrogen, for example, hydrogen supplied to the machine inlet, or hydrogen at a low pressure relative to the machine inlet, specifically, hydrogen coming from the machine outlet.

[0027] A fourth embodiment 400 of the expander generator will be described below with reference to FIG. 4. It should be noted that the elements 410, 411, 412, 413, 414, 420, 421, 422, 423, 430, and 440 in FIG. 4 may be the same as or similar to the elements 110 (impeller), 111 (machine inlet), 112 (machine outlet), 113 (fluid conduit), 114 (internal channel), 120 (generator), 121 (rotating hub), 122 (rotating magnetic assembly), 123 (fixed magnetic assembly), 130 (magnetic bearing), and 140 (casing) in FIG. 1, and may perform the same or similar functions.

[0028] According to the embodiment of FIG. 4, the expander generator 400 has three magnetic bearings, specifically, a first radial magnetic bearing 430, a thrust magnetic bearing 431 (note that the positions can be swapped) located downstream of the radial magnetic bearing 430, and a second radial magnetic bearing 342. Some (advantageously all) of the magnetic bearings 430, 431, and 432 can be cooled by the hydrogen flow from the machine inlet 411, specifically, they can be cooled in series and / or in parallel as will be more clearly described below.

[0029] Referring to FIG. 4 non - limitatively, a first portion of the hydrogen supplied to the machine inlet 411 is first supplied to, for example, the radial magnetic bearing 430 and then to the thrust magnetic bearing 431 to cool them. Specifically, it flows through the gap between at least the rotating element and the stator element of the magnetic bearings 430 and 431 (see the small black arrows in FIG. 4), and finally, the heated hydrogen is discharged to the machine outlet 412 (see the black arrow starting from downstream of the thrust magnetic bearing 431 and ending at the machine outlet 412). In other words, the magnetic bearings 430 and 431 are cooled in series.

[0030] Referring to FIG. 4 non - limitatively, a second portion of the hydrogen supplied to the machine inlet 411 is first supplied to, for example, the radial magnetic bearing 432 and then to the generator 420. Specifically, it circulates in the gap between the rotating magnetic assembly 422 and the fixed magnetic assembly 423. In other words, the magnetic bearing 432 and the generator 420 are cooled in series. According to another possibility not shown, the second portion of the hydrogen supplied to the machine inlet 411 is supplied only to the generator 420 to cool the generator 420.

[0031] Advantageously, the heated hydrogen downstream of the thrust magnetic bearing 431 and the heated hydrogen downstream of the generator 420 (i.e., after circulating in the gap between the rotating magnetic assembly 422 and the fixed magnetic assembly 423) are discharged to the machine outlet 412.

[0032] According to the example shown in FIG. 4, magnetic bearings 430 and 431 and magnetic bearings 432 and generator 420 are cooled in parallel. However, different configurations may be applied (see, for example, FIG. 5). For example, the magnetic bearings and the generator may be cooled in series, supplying hydrogen first to at least one magnetic bearing, then to the generator, or first to the generator, then to at least one magnetic bearing.

[0033] FIG. 5 shows another embodiment that is similar to the embodiment of FIG. 4, but differs in that the above-described first and second portions of hydrogen used to cool magnetic bearings 530, 531, and 532 and generator 520 are the same hydrogen stream. In particular, referring non-limitingly to FIG. 5, a portion of the hydrogen supplied to machine inlet 511 flows through fluid conduit 513 and is used to cool first radial magnetic bearing 530, thrust magnetic bearing 531, generator 520, and second radial magnetic bearing 532 in series. Finally, a portion of the hydrogen downstream of second radial magnetic bearing 532 is discharged as heated hydrogen at machine outlet 512 and preferably mixed with the expanded hydrogen expanded by impeller 510.

[0034] According to another possibility not shown in any of the figures, thrust magnetic bearing 531 is located downstream of generator 520, flows through fluid conduit 513, and may be cooled by a portion of the hydrogen supplied to machine inlet 511 that is used to cool first radial magnetic bearing 530, generator 520, thrust magnetic bearing 531, and finally second radial magnetic bearing 532 in series. According to yet another possibility not shown in any of the figures, thrust magnetic bearing 531 is located downstream of second radial magnetic bearing 532, flows through fluid conduit 513, and may be cooled by a portion of the hydrogen supplied to machine inlet 511 that is used to cool first radial magnetic bearing 530, generator 520, second radial magnetic bearing 532, and finally thrust magnetic bearing 531 in series.

[0035] A sixth embodiment 600 of the expander generator will be described below with reference to FIG. 6. It should be noted that the elements 610, 611, 612, 613, 614, 620, 621, 622, 623, 630, and 640 in FIG. 6 can be the same as or similar to the elements 110 (impeller), 111 (mechanical inlet), 112 (mechanical outlet), 113 (fluid conduit), 114 (internal channel), 120 (generator), 121 (rotating hub), 122 (rotating magnetic assembly), 123 (stationary magnetic assembly), 130 (magnetic bearing), and 140 (casing) in FIG. 1, and can perform the same or similar functions. It should be noted that the embodiment in FIG. 6 is similar to the embodiment in FIG. 4. The only difference between FIG. 6 and FIG. 4 is that, as will become apparent below, a second portion of the hydrogen used to cool the radial magnetic bearing 632 and the generator 620 is supplied by the mechanical outlet 612.

[0036] With non-limiting reference to FIG. 6, a portion of the hydrogen supplied to the mechanical inlet 611 is first supplied, for example, to the radial magnetic bearing 630 and then to the thrust magnetic bearing 631 to cool them. Specifically, it flows through the gaps between at least the rotating elements and the stator elements of the magnetic bearings 630 and 631 (see the small black arrows in FIG. 6). Finally, the heated hydrogen is discharged to the mechanical outlet 612 (see the black arrow starting from downstream of the thrust magnetic bearing 631 and ending at the mechanical outlet 612). In other words, the magnetic bearings 630 and 631 are cooled in series.

[0037] With non-limiting reference to FIG. 6, the radial magnetic bearing 632 and the generator 620 can be cooled by a portion of the hydrogen supplied by the mechanical outlet 612, specifically, a portion of the hydrogen discharged by the impeller 610. Advantageously, the machine 600 includes a control valve 680 located at the mechanical outlet 612 to enable extraction of hydrogen from the mechanical outlet 612. In fact, the control valve 680 causes a pressure drop, specifically a small pressure drop in the range of 1 to 1.5 bar, to enable the circulation of hydrogen, as will be more clearly explained below.

[0038] According to the embodiment of FIG. 6, a part of the hydrogen from the machine outlet 612 is first supplied to, for example, the radial magnetic bearing 632 and then to the generator 620. Specifically, it circulates in the gap between the rotating magnetic assembly 622 and the stationary magnetic assembly 623. In other words, the magnetic bearing 632 and the generator 620 are cooled in series.

[0039] Advantageously, the heated hydrogen downstream of the thrust magnetic bearing 631 and the heated hydrogen downstream of the generator 620 (i.e., after circulating in the gap between the rotating magnetic assembly 622 and the stationary magnetic assembly 623) can merge and be discharged downstream of the machine outlet 612, specifically, downstream of the control valve 680.

[0040] According to another possibility not shown in any of the figures, the magnetic bearing 632 and the generator 620 can be cooled in parallel. In other words, a part of the hydrogen from the machine outlet 612 can be supplied between the generator 620 and the rotating magnetic assembly 622. Thereby, the first part of the hydrogen can flow through the gap between the rotating magnetic assembly 622 and the stationary magnetic assembly 623 to cool the generator 620, and the second part of the hydrogen can flow through the gap between the rotating element and the stator element of the radial magnetic bearing 632 to cool the radial magnetic bearing 632. Advantageously, the first part of the hydrogen can merge with the heated hydrogen downstream of the thrust magnetic bearing 631 after cooling the generator 620 (i.e., downstream of the generator 620) and be discharged downstream of the machine outlet 612, specifically, downstream of the control valve 680. Advantageously, the second part of the hydrogen can merge with the heated hydrogen downstream of the thrust magnetic bearing 631 after cooling the radial magnetic bearing 632 (i.e., downstream of the radial magnetic bearing 632) and be discharged downstream of the machine outlet 612, specifically, downstream of the control valve 680.

[0041] For clarity, it should be noted that in FIGS. 2, 3, 4, 5, and 6, the hydrogen flow used to cool the radial magnetic bearing and / or the thrust magnetic bearing and / or the generator is shown outside the machine casing. However, appropriate channels can be provided in the machine casing to circulate the hydrogen flow inside the casing.

[0042] According to some embodiments (not shown), expander generator machines, such as machines 100, 200, 300, 400, 500, and 600 in the figures, may include a second impeller. It should be noted that the second impeller can be an expander or a compressor that expands or compresses the hydrogen supplied to the machine, respectively. Specifically, the second impeller can be located at the end of the same expander generator machine as the first impellers 110, 210, 310, 410, 510, and 610 (i.e., the same rotating hub end), or at the end opposite to the first impellers 110, 210, 310, 410, 510, and 610 (i.e., the opposite rotating hub end). The supply of hydrogen from the machine inlets 112, 212, 312, 412, 512, and 612 to the first and second impellers can be in series or in parallel. According to an advantageous possibility, when the expander generator machine has a second impeller located at the rotating hub end opposite to the first impeller and the supply of hydrogen to the first and second impellers is in parallel, the thrust magnetic bearing can be omitted.

[0043] In conclusion, the expander generator machines 100, 200, 300, 400, 500, and 600 can utilize a portion of the fluid expanded by the impeller to advantageously cool at least one magnetic bearing of the machine, and preferably also the generator. Preferably, the expander generator machines 100, 200, 300, 400, 500, and 600 are configured such that during operation of the machine, the pressure of the environment inside the casing is higher than the pressure of the environment outside the casing. In other words, the casing is pressurized so that the ambient environment cannot leak into the casing. Even more preferably, oxygen is discharged from the environment inside the casing to avoid the risk of fire and / or explosion during installation or before startup of machines 100, 200, 300, 400, 500, and 600.

Claims

**Claim 1** An expander generator machine (100) having a machine inlet (111) and a machine outlet (112), - An impeller (110) configured to receive compressed hydrogen from the machine inlet (111), expand the compressed hydrogen through impeller blades, and discharge the expanded hydrogen at the machine outlet (112); - A generator (120) configured to generate electrical energy, comprising a rotating hub (121), a rotating magnetic assembly (122) mechanically connected to the rotating hub (121), and a stationary magnetic assembly (123) disposed around the rotating magnetic assembly (122); - At least one magnetic bearing (130) acting on the rotating hub (121); - A casing (140) housing the impeller (110), the generator (120), and the at least one magnetic bearing (130), The impeller (110) is mechanically connected to the rotating hub (121), The at least one magnetic bearing (130) is fluidly connected to the inlet (111), An expander generator machine (100) configured to be cooled by a hydrogen flow from the machine inlet (111). **Claim 2** The expander generator machine (100, 200, 300, 400, 500) according to claim 1, wherein at least one magnetic bearing (130, 230, 330, 430, 530) is located between the impeller (110, 210, 310, 410, 510) and the generator (120, 220, 320, 420, 520). **Claim 3** The expander generator machine (100, 200, 300, 400, 500) according to claim 1, wherein the pressure of the environment inside the casing (140, 240, 340, 440, 540) is configured to be higher than the pressure of the environment outside the casing during operation of the machine. **Claim 4** The expander generator machine (100, 200, 300, 400, 500) according to claim 1, wherein the environment inside the casing (140, 240, 340, 440, 540) is configured to be oxygen-free. **Claim 5** The at least one magnetic bearing (230, 330, 331, 430, 431, 432, 530, 531, 532) is fluidly connected to the machine outlet (212, 312, 412, 512) and is configured to discharge a heated hydrogen stream at the outlet (212, 312, 412, 512), the expander generator machine (200, 300, 400, 500) according to claim 1.

6. The expander generator machine (100, 200, 300, 400, 500) according to claim 1 further comprises a fluid conduit (113, 213, 313, 413, 513) fluidly connecting the machine inlet (111, 211, 311, 411, 511) and the at least one magnetic bearing (130, 230, 330, 430, 530), and the fluid conduit (113, 213, 313, 413, 513) is at least partially defined by the back surface of the impeller (110, 210, 310, 410, 510).

7. The expander generator machine (100, 200, 300, 400, 500) according to claim 6, wherein the impeller (110, 210, 310, 410, 510) comprises at least one internal channel (114, 214, 314, 414, 514) fluidly connecting the fluid conduit (113, 213, 313, 413, 513) and the impeller blades.

8. The expander generator machine (300, 400, 500) according to claim 1 further comprises a cooling system configured to circulate a cooling fluid to cool the rotating magnetic assembly (322, 422, 522) and / or the stationary magnetic assembly (323, 423, 523).

9. A gap is defined between the rotating magnetic assembly (322, 422, 522) and the stationary magnetic assembly (323, 423, 523), and the cooling fluid is configured to circulate within the gap, the expander generator machine (300, 400, 500) according to claim 8.

10. A first cooling system configured to circulate a first cooling fluid to cool the rotating magnetic assembly (322, 422), and optionally also the fixed magnetic assembly (323, 423); and a second cooling system configured to circulate a second cooling fluid to cool the fixed magnetic assembly (323, 423), the expander generator machine (300, 400) according to claim 8.

11. The expander generator machine (400, 500) according to claim 8, wherein the cooling fluid is hydrogen.

12. The expander generator machine (400) according to claim 10, wherein both the first cooling fluid and the second cooling fluid are hydrogen.

13. The cooling system is fluidly connected to the inlet (411, 511) and is configured to circulate a hydrogen flow from the machine inlet (411, 511), the expander generator machine (400, 500) according to claim 8.

14. The cooling system is fluidly connected to the machine outlet (412, 512) and is configured to discharge a heated hydrogen flow at the machine outlet (412, 512), the expander generator machine (400, 500) according to claim 8.

15. The cooling system is fluidly connected to the at least one magnetic bearing (432, 530, 531, 532), the expander generator machine (400, 500) according to claim 14.

16. The expander generator machine (400) according to claim 14, configured to discharge a heated hydrogen flow from the gap and a heated hydrogen flow from the at least one magnetic bearing (430, 431, 432) to the machine outlet (412).

17. The at least one magnetic bearing is a first radial magnetic bearing (430, 530), a thrust magnetic bearing (431, 531), and a second radial magnetic bearing (432, 532), the expander generator machine (400, 500) according to claim 1.

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