Cryogenic expansion turbine with magnetic bearings
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- CHART ENERGY & CHEMICALS INC
- Filing Date
- 2023-04-11
- Publication Date
- 2026-04-17
AI Technical Summary
Cryogenic turbo expanders face challenges with magnetic bearings, as the continuous power required for active magnetic bearings generates heat, which can lead to gas leakage and contamination, and high temperature superconducting bearings require effective cooling to maintain efficiency.
The implementation of a cryogenic expansion turbine with a bearing cooling fluid circuit that directs a stream of cooling fluid through electromagnetic bearings, effectively cooling them and managing heat buildup, while also ensuring the bearings are supported without physical contact.
This solution effectively cools the magnetic bearings, preventing heat-induced gas leakage and contamination, while maintaining the efficiency and low friction characteristics of magnetic bearings in cryogenic applications.
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Abstract
Description
[Technical field]
[0001] Claiming priority
[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 330,005, filed April 12, 2022, the contents of which are incorporated herein by reference.
[0002]
[0002] This disclosure relates generally to cryogenic fluid expansion devices, and more particularly to cryogenic expansion turbines having magnetic bearings that provide cooling for the bearings. [Background technology]
[0003]
[0003] Turbine expansion devices, or turboexpanders, are used to expand, and thus refrigerate, cryogenic gases in industrial processes such as the liquefaction of hydrogen or natural gas. The work done by the cryogenic gas in rotating the expander wheel of the turboexpander cools the gas in the expander. As the cryogenic gas expands, the centrifugal or axial flow of the cryogenic gas through a turbine is often used to drive a compressor, generator, or other braking device, thereby extracting work from the expanding gas. The expanded gas may be partially liquefied.
[0004]
[0004] When a turboexpander is used to drive a compressor or generator, the expander wheel is typically placed at one end of a rotating shaft and the compressor wheel or generator is placed at the opposite end of the rotating shaft. The rotating shaft operates at very high rotational speeds (typically 25,000 revolutions per minute or more) and must therefore be supported by suitable bearings.
[0005]
[0005] Magnetic bearings have been used in cryogenic turboexpanders because they support the rotating shaft within the bearing housing without physical contact. As a result, the bearings have low friction and are not subject to wear or speed limitations. Most magnetic bearings are active magnetic bearings and therefore use electromagnets that require continuous power. As a result, heat builds up in the electric coils of the electromagnets and therefore in the bearing housing, making cooling desirable.
[0006]
[0006] Furthermore, since the bearing operates at a temperature significantly higher than that of the cryogenic turboexpander operating at a cryogenic temperature, a seal surrounding the rotating shaft must be placed between the bearing housing and the turboexpander. When the temperature of the bearing increases, the pressure in the bearing housing increases and gas may leak through the seal into the turboexpander. Proper management of the bearing temperature is desirable to avoid damage to the seal. When the seal is damaged, the cold gas in the turboexpander may be contaminated with the warm fluid leaking from the bearing, and the cold fluid leaking from the turboexpander may damage the bearing. High temperature superconducting (HTS) magnetic bearings utilize the temperature of the refrigerated gas to eliminate electrical resistance in the bearing, but separation of the fluid in the HTS magnetic bearing housing and the turboexpander housing may still be required in some conditions, such as when the compressor braking device is driven by the turboexpander at steady state conditions. Summary of the Invention [Means for solving the problem]
[0007]
[0007] There are several aspects of the present subject matter that can be embodied separately or together in the methods, apparatus, and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and describing these aspects together is not intended to exclude using these aspects separately or claiming such aspects separately or in different combinations as described in the claims appended hereto.
[0008] In one aspect, a cryogenic expansion turbine includes a turboexpander configured to receive and expand a cryogenic gas supply stream, a resistance device, and a rotating shaft operatively connecting the turboexpander and the resistance device. A bearing housing has a bearing cooling fluid inlet port and a bearing cooling fluid outlet port. A plurality of electromagnetic bearings are disposed within the bearing housing and rotatably support the rotating shaft. A bearing cooling circuit directs a flow of bearing cooling fluid through the bearing cooling fluid inlet port and into the bearing housing, thereby cooling the plurality of electromagnetic bearings. The resulting warmed bearing cooling fluid exits the bearing housing through the cooling fluid outlet port.
[0009]
[0009] In another aspect, a method for cooling electromagnetic bearings in a cryogenic expansion device having a turboexpander operably connected to a resistive load by a rotating shaft supported by an electromagnetic bearing in a bearing housing includes the steps of directing a bearing cooling fluid to the bearing housing, cooling the electromagnetic bearings using the bearing cooling fluid to result in the production of warmed bearing cooling fluid, and withdrawing the warmed bearing cooling fluid from the bearing housing.
[0010] In yet another aspect, a cryogenic expansion turbine includes a turboexpander configured to receive and expand a cryogenic gas supply stream, a resistance device, and a rotating shaft operatively connecting the turboexpander and the resistance device. A bearing housing has a bearing cooling fluid inlet port and a bearing cooling fluid outlet port. A plurality of electromagnetic bearings are disposed within the bearing housing and rotatably support the rotating shaft. A cooling jacket at least partially surrounds the bearing housing. A bearing cooling circuit is configured to direct a flow of bearing cooling fluid into the cooling jacket, thereby cooling the plurality of electromagnetic bearings, and a resulting warmed bearing cooling fluid exits the cooling jacket. [Brief description of the drawings]
[0011] [Figure 1] 1 is a schematic diagram of a first embodiment of a cryogenic expansion turbine of the present disclosure. [Diagram 2]
[0012] FIG. 2 is a schematic diagram of a second embodiment of a cryogenic expansion turbine of the present disclosure. [Diagram 3]
[0013] FIG. 2 is a schematic diagram of a third embodiment of a cryogenic expansion turbine of the present disclosure. [Figure 4]
[0014] FIG. 13 is a schematic diagram of a fourth embodiment of a cryogenic expansion turbine of the present disclosure. [Diagram 5]
[0015] FIG. 13 is a schematic diagram of a fifth embodiment of the cryogenic expansion turbine of the present disclosure. [Figure 6]
[0016] FIG. 13 is a schematic diagram of a sixth embodiment of a cryogenic expansion turbine of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012]
[0017] A more detailed description of the system and method according to the present disclosure is described below. It should be understood that the following description of the specific system and method is intended to be illustrative and does not cover all possible variations or applications. Therefore, the scope of the present disclosure is not intended to be limiting and should be understood to include variations or embodiments that may occur to those skilled in the art.
[0013]
[0018] It should be noted that, herein, lines, conduits, piping, passageways, and similar structures, and corresponding streams, may be referred to together by the same element numbers as depicted in the figures.
[0014]
[0019] Reference numerals introduced in the specification in connection with a depicted figure may be repeated in one or more subsequent figures to share elements or components without additional description in the specification to provide context for other features.
[0015]
[0020] In the claims, letters are used to identify the claimed steps (e.g., a., b., and c.). These letters are used to aid in referencing the method steps and are not intended to indicate the order in which the claimed steps are performed unless and only to the extent such an order is expressly recited in the claims.
[0016]
[0021] The embodiments described below refer to hydrogen gas as the cryogenic gas feed stream expanded in the turboexpander, however, the techniques of the present disclosure may be used to expand other cryogenic fluids. Additionally, the embodiments described below use hydrogen as the recirculation and bearing cooling fluid, however, alternative fluids known in the art may be used.
[0017]
[0022] A first embodiment of a cryogenic expansion turbine of the present disclosure is shown generally at 10 in FIG. 1. The cryogenic expansion turbine 10 includes a turbo expander 12 connected by a rotating shaft 16 and a resistance device, which in this embodiment is a compressor 14. The rotating shaft 16 is rotatably mounted within a bearing housing 18 by active or electromagnetic bearings 22a-d. As is known in the art, seals are provided about the rotating shaft at the two points where it exits the bearing housing 18. Suitable active or electromagnetic bearings may be obtained from SKF Group, Gothenburg, Sweden, or Waukesha Bearings, Waukesha, Wisconsin, USA. Examples of suitable active magnetic bearings are provided in U.S. Patent No. 4,652,780 to Murakami et al., U.S. Patent No. 4,720,649 to Habermann et al., U.S. Patent No. 9,845,829 to Hay et al., and U.S. Patent No. 10,030,703 to Bauce et al., the contents of each of which are incorporated herein by reference. Examples of high temperature superconducting (HTS) magnetic bearings suitable for the embodiments described below are disclosed in European Patent Application No. 1835188 to Nexans and U.S. Patent No. 5,789,837 to Shin et al., the contents of each of which are incorporated herein by reference.
[0018]
[0023] As is known in the art, the turboexpander 12 includes an inlet, an outlet, and an expander wheel such that gas entering the turboexpander is expanded and the resulting cooled fluid exits the turboexpander. The compressor 14 includes an inlet, an outlet, and a compressor wheel that is rotated by an expander wheel that rotates via a rotating shaft 16 such that the turboexpander 12 and the compressor 14 are operatively connected by the rotating shaft 16.
[0019]
[0024] A hydrogen cryogenic gas feed stream 24 enters the turboexpander 14 and is expanded while working, with the resulting cooled hydrogen fluid feed stream exiting as stream 26. The turboexpander may be located within a cold box 28, and the cooled hydrogen fluid stream proceeds to a liquefaction process.
[0020]
[0025] A compressor 14 is provided with a recirculation fluid circuit, generally indicated at 30 in FIG. 1. A hydrogen gas recirculation stream 32 enters the compressor 14 and is compressed. As a result, the turboexpander 12 serves to rotate the compressor 14. The resulting warmed recirculation stream exits the compressor as stream 34 and is cooled in an aftercooler 36. By way of example only, the aftercooler may be a heat exchanger using ambient air or a refrigerant as the cooling stream. The recirculation fluid circuit includes a recirculation fluid withdrawal line 38 having a corresponding withdrawal valve 42. When the withdrawal valve 42 is open, cooled fluid 44 from the aftercooler 36 may be directed to exit the recirculation fluid circuit through line 38. Alternatively, when the valve 42 is closed, which is the normal mode of operation, the fluid 44 may be directed through the expansion valve 46 to provide a fluid pressure resistance such that the turboexpander 12 serves to rotate the compressor 14. As a result, expanded cooled stream 32 is formed (when supply valve 48 is closed).
[0021]
[0026] Additional hydrogen recirculation fluid can be supplied to the recirculation circuit through a supply line 52 when the supply valve 48 is opened. As previously described, the withdrawal valve 42 can be opened to withdraw fluid from the recirculation fluid circuit 30. The supply valve 48 and withdrawal valve 42 can be automated and provided with feedback control by a pressure controller 54 so that an appropriate amount of fluid can be maintained in the recirculation circuit. A rate controller 55 can also be provided for the expansion valve 46, which can also be automated. By way of example only, the rate controller can be an external loop feeding into a pressure controller (i.e., a cascade control scheme). Similar valve control schemes can be used for the systems of Figures 2 and 3 described below.
[0022]
[0027] The system of FIG. 1 is provided with a bearing cooling circuit generally designated 72. A bearing cooling fluid, such as hydrogen gas from a pressurized source, is in fluid communication with a bearing circuit cooling fluid line 62 provided with a control valve 64. By way of example only, the cooling fluid may be pressurized to approximately 20 psi above the pressure at the outside diameter of the expander wheel of the turbo expander 12. When the control valve 64 is open, hydrogen cooling gas is provided to the interior of the bearing housing through the cooling fluid inlet port as indicated by arrows 66a, 66b, and 66c. Although three cooling fluid inlet ports are shown in FIG. 1, the housing may alternatively have only one inlet port or more than three inlet ports. The coils of the active magnetic bearings 22a-22d are cooled by the hydrogen gas cooling fluid, and the warmed cooling fluid exits the bearing housing 18 through the cooling fluid outlet port and the lines of the bearing cooling circuit as indicated by arrows 68. Although one cooling fluid outlet port is shown in FIG. 1, the housing may alternatively have more than one outlet port.
[0023]
[0028] The warmed hydrogen gas cooling fluid 68 exiting the bearing housing 18 may be directed to the compressor of the liquefaction system or to other destinations. As a result, the system of Figure 1 features an open-loop bearing cooling circuit.
[0024]
[0029] A second embodiment of the system of the present disclosure is shown generally at 200 in Figure 2 and includes a closed-loop bearing cooling circuit 272. The configuration and operation of the system 200 of Figure 2 is the same as that of Figure 1, except for the configuration of the bearing cooling circuit.
[0025]
[0030] In the system of FIG. 2, cooling fluid line 202 branches off from line 204 of a recirculation fluid circuit generally designated 230. As a result, a portion of the hydrogen in the recirculation circuit flows through line 202 and into the interior of bearing housing 208 through a cooling fluid inlet port, as indicated by arrow 206. Although one cooling fluid inlet port is shown in FIG. 2, the housing may alternatively have more than one inlet port. The coils of active magnetic bearings 222a-222d are cooled by the hydrogen gas cooling fluid, and the warmed cooling fluid exits bearing housing 208 through a cooling fluid outlet port and line 216. Although one cooling fluid outlet port is shown in FIG. 2, the housing may alternatively have more than one outlet port.
[0026]
[0031] The warmed hydrogen gas cooling fluid in line 216 exits the bearing housing 208 and enters back into the recirculating fluid circuit by joining line 218. As a result, the system of Figure 2 features a closed-loop bearing cooling circuit.
[0027]
[0032] A cooling fluid supply line 220 is provided with a valve 224 and in communication with a pressurized source of hydrogen gas such that when valve 224 is opened, the cooling fluid circuit and the recirculation fluid circuit can be replenished with hydrogen gas as needed.
[0028]
[0033] The embodiment of FIG. 2 typically provides the advantages of not having to add extracted hydrogen to the bearing cooling fluid circuit and the efficiency provided by the compressor 214 (when powered by the turboexpander 212) providing a cooling flow of hydrogen gas to the bearings.
[0029]
[0034] Except for the above-mentioned components, the remainder of the system of FIG. 2 features the same structure and function as the previous embodiment.
[0030]
[0035] If additional braking is required for the system of Figure 2 such that the turboexpander performs additional work, or if additional compression is required for the recirculation and braking fluid circuits, an additional resistance device in the form of a second compressor may be added to the system of Figure 2, as shown in Figure 3. More particularly, with reference to Figure 3, the recirculation fluid circuit, generally designated 330, may include first and second compressor stages 314a and 314b. The first and second compressor stages 314a and 314b are both powered by the turboexpander 312 and may be separate compressors or may be separate stages of a single compressor.
[0031]
[0036] 3, the warmed cooling fluid exits the bearing housing 308 through the cooling fluid outlet port of the bearing cooling circuit 372 and line 316 and is directed to the inlet of the first compressor stage 314a. In addition, similar to the previous embodiment, stream 332, formed when cooled fluid 344 from the aftercooler 336 is directed through the expansion valve 346, is directed to the first compressor stage 314a. The warmed recycle stream exits the second compressor stage 314b as stream 334 and is cooled in the aftercooler 336.
[0032]
[0037] Except for the above-mentioned components, the remainder of the system of FIG. 3 features the same structure and function as the previous embodiment.
[0033]
[0038] A fourth embodiment of the system of the present disclosure is shown generally at 400 in FIG. 4. In this embodiment, high temperature superconducting (HTS) magnets are used for HTS magnetic bearings 422a-422d. HTS magnetic bearings also require cooling to offset heat losses, but because there is no electrical resistance, no heat is generated when the magnets are operated. The system of FIG. 4 includes a bearing cooling circuit 472, where a cooling fluid line 402 branches off from a hydrogen cryogenic gas supply line 424 that enters a turbo expander 414. As a result, when an inlet control valve 404 is open, a portion of the hydrogen gas supply from line 424 flows through the bearing cooling fluid inlet line 402 and through a cooling fluid inlet port into the interior of the bearing housing 408. By way of example only, the hydrogen gas in line 402 may be at approximately 60° K. Although one cooling fluid inlet port is shown in FIG. 4, the housing may alternatively have more than one inlet port. The HTS magnetic bearings 422a-422d are cooled by a hydrogen gas cooling fluid, which cools the superconducting material to the required cryogenic temperature (such as below 70° K), thereby avoiding or minimizing resistance and thereby heat generation due to electrical current. The warmed cooling fluid may exit the bearing housing 408 through a cooling fluid outlet port and a bearing cooling fluid outlet line 416 under the control of an outlet control valve 418 and returned to the main system compressor in the circuit with the hydrogen gas feed stream in line 424. In some alternative embodiments, the expander gas may exit through the compression circuit. Although one cooling fluid outlet port is shown in FIG. 4, the housing may alternatively have more than one outlet port.
[0034]
[0039] Warmed hydrogen gas cooling fluid exiting bearing housing 408 through line 416 and valve 418 may be directed to a liquefaction system compressor or other destination. Valve 418 may be automated and provided with feedback control, including temperature controller 428, to appropriately regulate the flow of fluid through line 416 to ensure sufficient cooling of high temperature superconducting magnetic bearings 422a-422d.
[0035]
[0040] As shown at 432 in FIG. 4, a portion of the hydrogen gas introduced into the bearing housing 408 may be returned to the turboexpander 412 to join stream 426 exiting the turboexpander 412 after expansion and cooling.
[0036]
[0041] As with the embodiment of Figure 3, the system of Figure 4 includes a recirculation fluid circuit, which may be a closed loop cycle generally designated 430, including two compressor stages 414a and 414b to provide sufficient cooling action within turboexpander 412. In some alternative embodiments, only one compressor may be sufficient.
[0037]
[0042] Except for the above-mentioned components, the remainder of the system of FIG. 4 features the same structure and function as the previous embodiment.
[0038]
[0043] In the HTS magnetic bearing of the embodiment of FIG. 4, the magnetic field can be much stronger than in conventional magnetic bearings. In addition, HTS-based motors and generators (related to the embodiments described below) can be reduced to one-third of their original size. With stronger magnetic fields and smaller size, higher RPM and higher efficiency can be achieved. The same is true for HTS generator braking devices.
[0039]
[0044] A fifth embodiment of the system of the present disclosure is shown generally at 500 in FIG. 5 and uses a generator / eddy current damper 502 in place of compressors 414a and 414b of FIG. 4 as a resistance device to turbo expander 512. Such a generator may optionally be provided as an HTS generator since cryogenic gas is already nearby for use therewith. As a result, generator 502 acts as an eddy current damper. The remainder of the system of FIG. 5 features the same structure and function as the system of FIG. 4.
[0040]
[0045] It should be understood that the generator / eddy current damping device 502 of Figure 5 can be used in place of any of the compressors of Figures 1-4 as a resistance device. Additionally, any of the compressors of Figures 1-4 can be supplemented with the generator / eddy current damping device 502 of Figure 5 such that the shaft rotated by the turbo expander of each embodiment rotates both the compressor and the generator / eddy current damping device as a resistance device.
[0041]
[0046] In a sixth embodiment of the disclosed system, the cooling jacket 606 at least partially surrounds the bearing housing 608 as an alternative to directing cooling gas into the bearing housing to cool the magnetic bearings. The cooling jacket features an inlet port to receive water, as indicated by arrow 605. As a result, the outer sidewall of the bearing housing 608 is surrounded by the cooling water to provide cooling for the inner bearings 622a-622d. As indicated by arrow 607, the jacket features an outlet port, as cooler water enters through the inlet port 605, warmed water or evaporated gases exit the jacket through the outlet port. As a result, the cooling water circulates through the jacket. In an embodiment in which the bearings 622a-622d are HTS magnetic bearings, the outer sidewall of the bearing housing 608 may be surrounded by liquid nitrogen to provide cooling for the inner bearings.
[0042]
[0047] The remainder of the system of FIG. 6 features the same structure and functionality as the system of FIG.
[0043]
[0048] While preferred embodiments of the present disclosure have been shown and described, it will be apparent to those skilled in the art that changes and modifications can be made therein without departing from the spirit of the disclosure, the scope of which is defined by the following claims.
Claims
1. a. A turbo expander configured to receive and expand a cryogenic gas supply flow, b. Resistors and, c. A rotating shaft that operably connects the turbo expander and the resistance device, d. A bearing housing having a bearing cooling fluid inlet port and a bearing cooling fluid outlet port, e. A plurality of electromagnetic bearings arranged within the bearing housing and rotatably supporting the rotating shaft, f. A bearing cooling circuit configured such that the flow of bearing cooling fluid is guided to the bearing housing through the bearing cooling fluid inlet port, thereby cooling the plurality of electromagnetic bearings, and the resulting heated bearing cooling fluid exits the bearing housing through the bearing cooling fluid outlet port. A cryogenic expansion turbine equipped with a
2. The cryogenic expansion turbine according to claim 1, wherein the resistor includes a compressor.
3. The cryogenic expansion turbine according to claim 2, further comprising a recirculating fluid circuit including a postcooler configured to receive compressed fluid from the compressor and an expansion valve configured to receive cooled fluid from the postcooler and guide the expanded fluid to the compressor.
4. The cryogenic expansion turbine according to claim 3, wherein the recirculating fluid circuit further includes a recirculating fluid extraction line having an extraction valve configured such that when the extraction valve is opened, recirculating fluid is extracted from the recirculating fluid circuit, and a recirculating fluid supply line having a supply valve configured such that when the supply valve is opened, recirculating fluid is added to the recirculating fluid circuit.
5. The cryogenic expansion turbine according to claim 3, further comprising a hydrogen recirculation fluid.
6. The cryogenic expansion turbine according to claim 3, wherein the bearing cooling circuit is configured to receive the flow of the bearing cooling fluid from the recirculating fluid circuit and to return at least a portion of the bearing cooling fluid from the recirculating fluid circuit.
7. The cryogenic expansion turbine according to claim 6, wherein the recirculating fluid circuit supplies the flow of the bearing cooling fluid downstream of the postcooler and returns at least a portion of the bearing cooling fluid to the recirculating fluid circuit downstream of the expansion valve.
8. The cryogenic expansion turbine according to claim 6, wherein the bearing cooling circuit further comprises a bearing cooling fluid supply line and a bearing cooling fluid supply valve configured to supply the bearing cooling fluid to the bearing cooling circuit when opened.
9. The cryogenic expansion turbine according to claim 2, wherein the resistor device includes a first compressor stage and a second compressor stage.
10. The cryogenic expansion turbine according to claim 9, wherein the first compressor stage and the second compressor stage are the first and second stages of a single compressor.
11. The cryogenic expansion turbine according to claim 9, wherein the first compressor stage includes a first compressor and the second compressor stage includes a second compressor.
12. The cryogenic expansion turbine further comprises a gas supply line configured to supply the cryogenic gas supply flow to the turbo expander, and the bearing cooling circuit, g. A bearing cooling fluid inlet line configured to receive the bearing cooling fluid from the gas supply line and guide the bearing cooling fluid to the bearing cooling fluid inlet port, h. A bearing cooling fluid outlet line configured to receive heated bearing cooling fluid from the bearing cooling fluid outlet port of the bearing housing, The cryogenic expansion turbine according to claim 1, comprising:
13. The cryogenic expansion turbine according to claim 12, wherein the bearing cooling fluid inlet line includes an inlet control valve, and the bearing cooling fluid outlet line includes an outlet control valve.
14. The cryogenic expansion turbine according to claim 1, further comprising a hydrogen bearing cooling fluid.
15. The cryogenic expansion turbine according to claim 1, wherein the resistor includes an eddy current damping device.
16. The cryogenic expansion turbine according to claim 1, wherein the resistance device includes a compressor and an eddy current damping device.
17. The cryogenic expansion turbine according to claim 1, wherein the plurality of electromagnetic bearings are high-temperature superconducting magnetic bearings.
18. A method for cooling an electromagnetic bearing in a cryogenic expansion device having a turbo expander operably connected to a resistive load by a rotating shaft supported by an electromagnetic bearing in a bearing housing, the method being: a. A step of introducing bearing cooling fluid into the bearing housing, b. The step of cooling the electromagnetic bearing using the bearing cooling fluid, thereby generating a heated bearing cooling fluid, c. The step of removing the heated bearing cooling fluid from the bearing housing, Methods that include...
19. The method according to claim 18, wherein the bearing cooling fluid contains hydrogen gas at approximately 60°K.
20. The method according to claim 18, wherein the resistive load includes a compressor, and the method further includes a step of compressing a recirculating fluid using the compressor, wherein step a. includes a step of directing a portion of the recirculating fluid to the bearing housing as the bearing cooling fluid.
21. The method according to claim 18, further comprising the step of directing a cryogenic gas supply flow to the turbo expander, wherein step a. includes directing a portion of the cryogenic gas supply flow to the bearing housing as the bearing cooling fluid.
22. The method according to claim 21, wherein the cryogenic gas supply flow and the bearing cooling fluid include hydrogen gas.
23. The method according to claim 18, wherein the electromagnetic bearing is a high-temperature superconducting magnetic bearing.
24. a. A turbo expander configured to receive and expand a cryogenic gas supply flow, b. Resistors and, c. A rotating shaft that operably connects the turbo expander and the resistance device, d. A bearing housing having a bearing cooling fluid inlet port and a bearing cooling fluid outlet port, e. A plurality of electromagnetic bearings arranged within the bearing housing and rotatably supporting the rotating shaft, f. A cooling jacket that at least partially surrounds the bearing housing, g. A bearing cooling circuit configured such that the flow of bearing cooling fluid is guided to the cooling jacket, thereby cooling the plurality of electromagnetic bearings, and the resulting heated bearing cooling fluid exits the cooling jacket. A cryogenic expansion turbine equipped with a
25. The cryogenic expansion turbine according to claim 24, further comprising water as the bearing cooling fluid.
26. The cryogenic expansion turbine according to claim 24, wherein the resistor includes an eddy current damping device.
27. The cryogenic expansion turbine according to claim 24, wherein the resistor device includes a compressor.
28. The cryogenic expansion turbine according to claim 24, wherein the plurality of electromagnetic bearings are high-temperature superconducting magnetic bearings.
29. The cryogenic expansion turbine according to claim 28, further comprising nitrogen as the bearing cooling fluid.