Electric motor having permanent magnets and immersion fuel pump having such electric motor

Abstract

The present disclosure relates to an electric motor for a pump, such as a submerged fuel pump for pumping liquefied fluids, in particular a low temperature submerged fuel pump for pumping liquefied fuels such as liquefied natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG), and the like, the electric motor comprising a rotor having a rotor body mounted on a motor shaft, and wherein the plurality of permanent magnets are disposed along a periphery of the rotor body, and wherein the rotor further comprises a mechanical magnet retention system for retaining the magnets in place in the rotor body; a stator having a coil arranged concentrically around the rotor; wherein the mechanical magnet retention system comprises a plurality of axially oriented slots in the periphery of the rotor body wherein the permanent magnets are retained in the slots, and wherein the axially oriented slots are formed with lateral tangential extensions in the periphery of the rotor body such that the slots are formed between two radially oriented side webs and a peripheral outer web, and a radially inward slot side is formed in the rotor body.

Description

Technical Field

[0001] The present invention relates to a pump motor, such as an immersed fuel pump for pumping a liquefied fluid, in particular a cryogenic immersed fuel pump for pumping a liquefied fuel such as liquefied natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG) or similar liquefied cryogenic medium fluids. Background Art

[0002] Submerged fuel pumps for liquefied fuels such as LNG driven by permanent magnet electric motors are well known in the art.

[0003] In WO 2015 / 081314 A2, a cryogenically immersed multistage pump assembly is disclosed, which includes a vertically oriented pump shaft. A permanent magnet motor includes a rotor attached to the pump shaft and a stator arranged around the rotor. A first-stage impeller assembly includes a first impeller attached to the pump shaft, and the first impeller is configured to move a cryogenic fluid from a first impeller inlet to a first impeller outlet when the pump shaft is rotated by the motor.

[0004] The disclosed pump also includes a hollow permanent magnet rotor in which a pump shaft is mounted. The pump shaft is mounted on the top of the hollow rotor by a nut, and below the motor, a plurality of impellers are mounted to the pump shaft.

[0005] WO 2015 / 065699 A2 discloses a rotor assembly for a permanent magnet motor of a pump assembly, the pump assembly including an electric submersible pump. In the rotor assembly, a plurality of permanent magnets are held by retaining clips in a rotor core. The magnets may be arranged in cavities or recesses in the surface of the rotor.

[0006] Purpose of the Invention

[0007] An object of the present invention is to provide an improved permanent magnet motor for a submerged fuel pump for pumping liquefied cryogenic fluids, wherein the magnets are arranged on the rotor close to its annular surface to improve efficiency. Summary of the invention

[0008] In the present invention, several embodiments of an electric motor for a pump are described, the pump being an immersed fuel pump for pumping a liquefied fluid, in particular a cryogenic immersed fuel pump for pumping a liquefied fuel, such as liquefied natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG) or similar liquefied cryogenic medium fluids, the motor comprising a rotor having a rotor body mounted on a motor shaft, and wherein a plurality of permanent magnets are arranged along the periphery of the rotor body, wherein the rotor also comprises a mechanical magnet retaining system for retaining the magnets in position in the rotor body; a stator having coils arranged concentrically around the rotor; wherein the mechanical magnet retaining system comprises a plurality of axially oriented slots in the periphery of the rotor body, wherein the permanent magnets are retained in the slots, and wherein the axially oriented slots are formed with lateral tangential extensions in the periphery of the rotor body, such that the slots are formed between two radially oriented side webs and a peripheral outer web, and radially inward slot sides are formed in the rotor body.

[0009] The use of an internal permanent magnet synchronous motor for an immersion cryogenic fuel pump is advantageous due to the high efficiency and compact design. By positioning the magnets in the slots and mechanically retaining the magnets in the slots, the magnets are held in a position close to the rotor surface, thereby ensuring that the magnetic field is as strong as possible and thereby ensuring the efficiency of the permanent magnet motor. Furthermore, when operating under cryogenic conditions, it is advantageous for the magnets to be held mechanically rather than, for example, glued in place, as the low temperatures may compromise the structural integrity of the glue. Preferably, each slot may be provided with a system of leaf spring members to retain the magnets inserted in each slot.

[0010] In order to ensure that the permanent magnets are most effective, it is important to ensure that the magnets are positioned close to the outer surface of the rotor body. Therefore, it has been found to be advantageous that the axially oriented slots are formed in the periphery of the rotor body with lateral tangential extensions such that the slots are formed between two radially oriented side webs and the peripheral outer web, and the radially inward slot side is formed in the rotor body. Preferably, the leaf spring members may be arranged in shallow recesses in the slots, for example shallow recesses formed in the radially inward slot side of the rotor body.

[0011] According to an advantageous embodiment, the leaf spring member is arranged in a plurality of shallow recesses in the slot. Furthermore, the leaf spring member may preferably be adapted to provide a radially outwardly directed force on the magnet when the magnet is inserted into the slot. This ensures that the magnet is held in an outward position with minimal clearance / play. In a preferred embodiment, the magnet has a cross-sectional shape that fits tightly into the slot on the leaf spring.

[0012] According to an advantageous embodiment, the leaf spring member is arranged in a plurality of shallow recesses in the slot. Furthermore, the leaf spring member may preferably be adapted to provide a radially outwardly directed force on the magnet when the magnet is inserted into the slot. This ensures that the magnet is held in an outward position with minimal clearance / play. In a preferred embodiment, the magnet has a cross-sectional shape that fits tightly into the slot on the leaf spring.

[0013] In some embodiments of the invention, the coaxial slots in the rotor are open at both ends for inserting the magnets. Depending on the rotor design and size, this may be advantageous and facilitates easy and correct assembly of the rotor.

[0014] In some embodiments, a total of six slots are provided evenly distributed along the cylindrical surface of the rotor, and wherein the magnetic polarity of adjacent magnets on the rotor surface is altered.

[0015] In other embodiments, a total of twelve slots are arranged to be evenly distributed along the cylindrical surface of the rotor. The motor topology can be optimized and selected according to actual needs. In some selected embodiments of the motor for a cryogenic pump, the permanent magnets are arranged in pairs with the same magnetic pole orientation so that the magnets on the surface are arranged in a NNSSNNSS configuration.

[0016] In some preferred embodiments, the rotor body is made of a plurality of sheet-like laminates made of magnetic steel, in particular electrical steel. The sheet-like laminates have a thickness of less than 1 mm, preferably about 0.35 mm to 0.5 mm, and are bonded together by adhesive. In an embodiment, the leaf springs can be laser cut into the laminates and thus made of the same material.

[0017] By the present invention, the motor is preferably adapted for use with a cryogenic pump having a high capacity for pumping liquefied fluids and adapted to operate at speeds up to 6,000 rpm.

[0018] In a preferred embodiment of the motor according to the present disclosure, the stator is provided with a coaxially arranged cooling channel on its cylindrical outer surface. Furthermore, the stator is mounted inside a cylindrical motor housing, so that the channel is formed between the stator and the motor housing. Thus, a compact motor with good cooling performance is achieved, making the motor suitable for powering a cryogenic pump.

[0019] In another aspect of the present invention, there is provided an immersed fuel pump for pumping liquefied fluids, in particular a cryogenic immersed fuel pump for pumping liquefied fuels such as liquefied natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG), etc.), wherein the pump comprises a housing having a lower fluid inlet and an upper fluid outlet and accommodating: a vertically oriented pump shaft; a permanent magnet motor as described above; at least one impeller mounted to the pump shaft for moving the cryogenic fluid from the inlet to the outlet; and wherein the pump shaft is concentrically mounted in a hollow motor drive shaft at the top end of these shafts. DETAILED DESCRIPTION

[0020] The present invention is described below with reference to the accompanying drawings, in which:

[0021] Figure 1 is a side sectional view of a low temperature immersed fuel pump according to an embodiment of the present invention;

[0022] Figure 2 yes Figure 1 A side sectional view of a permanent magnet synchronous motor of a pump in FIG.

[0023] Figure 3 is with Figure 2 A cross-sectional view of the permanent magnet synchronous motor orthogonal to the view;

[0024] Figure 4 is a cross-sectional view of a rotor in a permanent magnet synchronous motor without magnets installed;

[0025] Figure 5 yes Figure 4 A detailed view of part B in FIG.

[0026] Figure 6 yes Figure 5 A detailed view of section C in FIG.

[0027] Figure 7 Is used to connect Figure 2 A side view of the clamping chucks for the motor shaft and the pump shaft shown in FIG.

[0028] Figure 8 is an end view of the clamping chuck.

[0029] exist Figure 1 , a cross-sectional view of a cryogenic immersed fuel pump for pumping liquefied fuels such as liquefied natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG), etc. is shown. The pump comprises a housing 1 having a lower fluid inlet 3' and an upper fluid outlet 3". The pump further comprises a vertically oriented pump shaft 4 and a permanent magnet motor 2.

[0030] The pump shaft 4 extends through the motor 2. Below the motor 2, a plurality of impellers 5 (such as Figure 1 The three shown) are mounted on the pump shaft 4 to provide a multi-stage centrifugal pump. Because these impellers or blades 5 are centrifugally mounted to the pump shaft 4, as the impellers 5 are rotated by the pump shaft 4, the impellers or blades 5 move the cryogenic fluid from the pump inlet 3' to the pump outlet 3".

[0031] The main flow of the liquefied fluid constitutes the main liquid flow from the pump inlet 3' to the pump outlet 3". Figure 1 Indicated by reference numeral 6. Figure 1 As shown, the main flow 6 is arranged coaxially around the electric motor 2 .

[0032] like Figure 1 As shown, the components of the pump are accommodated in a housing 1. The housing includes a plurality of intermediate chambers 1A stacked one above the other, a lower flow branch portion 1B, a central motor housing portion 1C, an upper flow branch portion 1D, and an upper outlet housing portion 1E, each intermediate chamber accommodating an impeller 5, and a main flow path 6 is provided through these housing portions 1A-1E.

[0033] These housing parts 1A-1E are provided with external assembly flanges and are assembled to one another by means of circumferentially arranged support bolts 1F.

[0034] The lower flow branch 1B is provided with a flow path for diverting the main flow 6 around the motor 2. Thus, the lower flow branch 1B has a central entry position in fluid communication with the uppermost top portion of the intermediate chamber 1A and radial flow delivery positions.

[0035] The center housing portion 1C is coaxially provided with a flow passage 61 at a radial position (see Figure 3 ), which is in fluid communication with the corresponding flow path of the lower flow branch 1B. The upper flow branch 1D is provided with a flow path between a radially outward receiving position to a central outlet flow outlet, wherein the radially outward receiving position is in fluid communication with the coaxial flow passage 61 of the central housing portion 1C.

[0036] The pump motor 2 is Figure 2 and Figure 3 The details are shown in more detail in Figures 4 to 6 . The motor 2 is housed in a motor housing 21, the motor 2 comprising a rotor assembly having a rotor body 23 mounted on a motor shaft 22, and wherein a plurality of permanent magnets 231 are arranged within the rotor body 23 along a periphery 234 of the rotor body 23. The motor further comprises a stator 24 having a plurality of coils concentrically arranged around the rotor assembly. The rotor assembly further comprises a mechanical magnet retaining system for retaining the magnets 231 in position in the rotor body 23. The mechanical magnet retaining system comprises a plurality of axially oriented slots 232 in the periphery 234 of the rotor body, wherein the permanent magnets 231 are retained.

[0037] The rotor body 23 is securely mounted on the motor shaft by any suitable means.

[0038] The motor shaft 22 is hollow, and the pump shaft 4 is concentrically mounted in the hollow motor drive shaft 22, as shown in FIG. Figure 1 As shown in . The assembly of the pump shaft 4 and the motor shaft 22 is provided by a collet clamp connection for interlocking the motor shaft 22 and the pump shaft 4 at the top ends of the shafts 4, 22. The pump shaft 4 is a smooth shaft, preferably a cylindrical elongated shaft with a constant diameter.

[0039] The collet clamp connection that mounts the pump shaft 4 to the motor shaft 22 is a collet clamp 41 made of an alloy suitable as a low temperature material, such as a metal alloy, for example bronze or stainless steel.

[0040] See also Figure 1 , Figure 2 as well as Figure 7 and Figure 8 The collet clamp connection comprises a clamping collet 41 having a conical outer clamping surface 41A engaging with a corresponding conical inner surface of the end section of the hollow motor shaft 22 and a cylindrical inner clamping surface 41B surrounding the clamping collet 41 of the pump shaft 4. The clamping collet 41 is secured to the pump shaft 4 by means of a clamping nut 29 (see Figure 2 ) is mounted to the motor shaft 22, the clamping nut 29 is provided with a conical inner surface which engages a conical collar surface 41C of the collet clamp 41. By tightening the clamping nut 29 to the end of the motor shaft 22, the clamping nut is threadedly engaged with the end section of the motor shaft 22, and the clamping collet 41 is pressed into the receiving surface of the motor shaft 22.

[0041] The motor shaft 22 is supported in the motor housing 21 and therefore also in the pump housing 1 by a main bearing 27, which is arranged at the upper end of the motor shaft 22 to withstand any axial forces that may occur in the pump. In some currently preferred embodiments, the main bearing 27 is a hybrid bearing, in particular a hybrid ball bearing, such as a deep groove ball bearing. A lower bearing 28 is arranged at the lower end of the motor shaft 22 in the motor 2 to absorb any radial forces generated. The lower bearing 28 is a carbon guide bearing. The motor shaft 22 can also be provided with a coating for additional hardness, such as a spray coating that forms a crack-free coating. This ensures the performance of the motor shaft 22 under low temperature conditions.

[0042] like Figure 1 As shown, a secondary liquid flow 7 is provided for cooling the motor 2 and lubricating the bearings 27, 28 in the motor 2. The secondary liquid flow 7 is a partial flow of the primary flow 6. The secondary flow 7 is a reverse liquid flow from the area of ​​the pump outlet 3" through the motor 2 to the radial center space 7A on the upper side of the uppermost impeller 5 above the area of ​​the pump inlet 3'.

[0043] A filter 71 is provided in the upper outlet housing part 1E of the housing 1 at the inlet for the secondary flow 7. The filter 71 is provided at the inlet of the secondary liquid flow path 7, thereby preventing any contaminants in the main flow 6 from entering the motor 2 and the bearings 27, 28, thereby protecting the motor 2 and the bearings 27, 28 and extending the life of these components. The filter 71 is preferably a low temperature filter, and even more preferably, the filter 71 may be a self-cleaning filter, such as a side stream filter.

[0044] The first liquid flow 6 is a main flow in which the pressure increases from the inlet 3' to the outlet 3" in the pump. Due to the pressure difference in the pump a reverse secondary flow 7 is provided so that a small part of the main flow 6 is reversed through the motor 2 to cool the motor and lubricate the bearings 27, 28. The bearings are therefore lubricated by the main flow through the pump.

[0045] The pressure difference is achieved by providing an outlet for the secondary flow at the radially central space 7A on the upper side of the uppermost impeller 5 (or the only impeller in one embodiment of the invention if the pump is designed with only one impeller 5).

[0046] The secondary liquid flow 7 is a partial flow of the main flow 6. Due to the narrow passage through the motor 2 and the bearings 27, 28, the flow resistance in the secondary flow path 7 is quite high. This means that the secondary liquid flow 7 is only a small amount of the main liquid flow 6, for example about at least 15-35 times smaller.

[0047] Around the cylindrical outer periphery of the stator 24, a plurality of axially oriented flow channels 25 are used to cool the electric motor 2, as these channels 25 constitute the majority of the secondary flow path 7 providing cooling for the electric motor.

[0048] As mentioned above, the electric motor is a permanent magnet synchronous motor in which the magnets are arranged in slots on the rotor. Figures 4 to 6 In the mechanical magnet holding system, each slot 232 is provided with a leaf spring member 233 to hold the magnet 231 inserted into the slot 232. When the magnet 231 is inserted into the slot 232, the leaf spring member 233 is disposed in a shallow recess in the slot 232 and is adapted to provide a radially outwardly directed force on the magnet 231 (see Figure 3 ). The magnet 231 is provided with a cross-sectional shape that fits tightly into the slot 232 on the leaf spring 233 .

[0049] The axially oriented slot 232 is formed with a lateral tangential extension in the periphery of the rotor body, so that the slot is formed between two radially oriented side webs 232a, 232b and a peripheral outer web 232c, and a radially inward slot side 232d is formed in the rotor body. In addition, the leaf spring member 233 may also be disposed in a shallow recess 233a of the slot 232, which is formed on the radially inner slot side 232d of the rotor body 23.

[0050] The slot 232 is coaxially provided in the rotor 23, and the slot 232 may be opened at both ends for inserting the magnet 231. Figure 3 In the illustrated embodiment, a total of twelve slots 232 are arranged evenly distributed along the cylindrical surface 234 of the rotor body 23. Every third magnet 231 changes the magnetic polarity of adjacent magnets on the rotor surface, so that the magnets 231 on the surface 234 are arranged in a NNSSNNSS configuration.

[0051] In an embodiment, the rotor body 23 is made of a plurality of sheet-like laminates made of magnetic steel, in particular electrical steel. The sheet-like laminates may be thin, such as less than 1 mm thick, preferably between 0.35 mm and 0.5 mm thick. In another embodiment, the leaf spring 233 may be laser cut into the laminates and thus made of the same material.

[0052] In the present disclosure, terms such as "vertical", "horizontal", etc. are used. These terms should be understood as relative directional terms between related elements, flanges, etc.

[0053] Although the present invention has been described in conjunction with specific embodiments, it should not be interpreted as being limited in any way to the examples presented. The scope of the present invention is defined by the appended claims. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Moreover, references such as "a" or "an" should not be interpreted as excluding multiple. The use of figure marks in the claims should not be interpreted as limiting the scope of the present invention relative to the elements shown in the drawings. In addition, individual features mentioned in different claims may be advantageously combined, and these features mentioned in different claims do not exclude that the combination of features is impossible and advantageous.

[0054] The invention has been described above with reference to some currently preferred embodiments of an immersion fuel pump. However, it will be appreciated by the present invention that other embodiments and variations may be provided without departing from the scope of the invention as defined in the appended claims.

Claims

1. A motor for a pump, the pump being an immersed fuel pump for pumping a liquefied fluid, in particular a cryogenic immersed fuel pump for pumping a liquefied fuel, the liquefied fuel being a liquefied cryogenic medium fluid such as liquefied natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG) or the like, the motor comprising A rotor having a rotor body mounted on a motor shaft, and wherein, a plurality of permanent magnets disposed along a periphery of the rotor body, wherein the rotor further comprises a mechanical magnet retention system for retaining the magnets in position in the rotor body; a stator having coils arranged concentrically around the rotor; Wherein, the mechanical magnet retaining system includes a plurality of axially oriented slots located in the periphery of the rotor body, wherein the permanent magnets are retained in the plurality of axially oriented slots, and wherein the axially oriented slots are formed with lateral tangential extensions located in the periphery of the rotor body, so that the slots are formed between two radially oriented side webs and a peripheral outer web, and a radially inward slot side is formed in the rotor body.

2. The electric motor according to claim 1, wherein: Each slot is provided with a system of leaf spring members to retain the magnet inserted in the slot.

3. The electric motor according to claim 1 or 2, wherein: The leaf spring member is disposed in a shallow recess in the slot, such as formed in the radially inward slot side of the rotor body.

4. An electric motor according to any one of the preceding claims, wherein The leaf spring member is adapted to provide a radially outwardly directed force on the magnet when the magnet is inserted into the slot, such that the leaf spring subjects the permanent magnet to a radially outwardly directed retaining force to retain the magnet in the slot.

5. An electric motor according to any one of the preceding claims, wherein The magnet is provided with a cross-sectional shape that fits tightly into the slot on the leaf spring.

6. An electric motor according to any one of the preceding claims, wherein: The coaxial slots in the rotor are open at both ends for insertion of magnets.

7. An electric motor according to any one of the preceding claims, wherein A total of six slots are provided evenly distributed along the cylindrical surface of the rotor, and wherein the magnetic poles of adjacent magnets on the rotor surface are altered.

8. The electric motor according to any one of claims 1 to 6, wherein: A total of twelve slots are provided substantially evenly distributed along the cylindrical surface of the rotor.

9. The electric motor according to claim 8, wherein: The permanent magnets are arranged in pairs with the same pole orientation so that the magnets on the surface are arranged in a NNSSNNSS configuration.

10. An electric motor according to any one of the preceding claims, wherein The rotor body is made of a plurality of sheet-like laminates, and the plurality of sheet-like laminates are made of magnetic steel, in particular electrical steel.

11. The electric motor according to claim 10, wherein: The sheet-like laminate has a thickness of less than 1 mm, preferably a thickness of about 0.35 mm to 0.5 mm.

12. The electric motor according to any one of claims 2 to 5, wherein: The leaf springs are laser cut into the laminate and are therefore made of the same material.

13. An electric motor according to any one of the preceding claims, wherein: The motor is suitable for use in a cryogenic pump for pumping a liquefied fluid, and the motor is adapted to operate at speeds up to 6,000 rpm.

14. An electric motor according to any one of the preceding claims, wherein The stator is provided with a coaxially arranged cooling channel on its cylindrical outer surface.

15. An immersed fuel pump for pumping liquefied fluids, in particular a cryogenic immersed fuel pump for pumping liquefied fuels, such as liquefied natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG), etc., the pump comprising: A housing having a lower fluid inlet and an upper fluid outlet and accommodating vertically oriented pump shaft; A permanent magnet motor according to any one of the preceding claims; at least one impeller mounted to the pump shaft for moving cryogenic fluid from an inlet to an outlet; Therein, the pump shaft is mounted concentrically in the hollow motor drive shaft at the top end of these shafts.

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