Immersion fuel pump for pumping liquefied fluid

Abstract

The present disclosure relates to 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 pump comprising a housing (1) having a lower fluid inlet (3 ') and an upper fluid outlet (3' ') and housing: a vertically oriented pump shaft (4); a permanent magnet motor (2) having a rotor with a hollow motor drive shaft (22) and a stator (24) surrounding the rotor; at least one impeller (5) mounted to the pump shaft (4) for centrifugally moving the cryogenic fluid from the pump inlet to the pump outlet; wherein a main liquid flow (6) having a main flow direction from the pump inlet to the pump outlet is arranged coaxially around the electric motor (2); and a secondary liquid flow (7) for cooling the electric motor (2) and lubricating bearings (27, 28) in the pump, the secondary flow (7) being a reverse liquid flow, which is substantially opposite in direction to the main flow (6), passing through the electric motor (2) from the region of the pump outlet to a radially central space (7A) on the upper side of the at least one impeller (5) in the region of the pump inlet (3 '), and wherein the secondary flow (7) is substantially opposite in direction to the main flow (6). A filter (71) is provided at the inlet of the secondary liquid flow path (7).

Description

Technical Field

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

[0002] Submerged fuel pumps for liquefied fuels such as LNG 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] WO 2015 / 081314 A2 also discloses a hollow permanent magnet rotor in which a pump shaft is mounted. The pump shaft is mounted on the top of the hollow rotor through a nut, and below the motor, a plurality of impellers are mounted to the pump shaft.

[0005] Purpose of the Invention

[0006] In order to ensure efficient pump performance, it is important that the motor and the cryogenic pump are not heated during operation, so that the liquefied fuel becomes gaseous. It is therefore an object of the present invention to provide an improved submerged fuel pump for pumping liquefied fluids, in particular a cryogenic submerged fuel pump for pumping liquefied fuels, which is compact in design and has improved efficiency. Summary of the invention

[0007] In the present invention, several embodiments of an immersed pump for pumping liquefied fluids are described, in particular a cryogenic immersed fuel pump for pumping liquefied fuels (such as liquefied natural gas (LNG), hydrogen, methanol, ethane, liquefied petroleum gas (LPG) or similar liquefied cryogenic medium fluids), the pump comprising a housing having a lower fluid inlet and an upper fluid outlet and accommodating a vertically oriented pump shaft; a permanent magnet motor having a rotor and a stator, the rotor having a hollow motor drive shaft, and the stator surrounding the rotor; at least one impeller mounted to the pump shaft for centrifugally moving the cryogenic fluid from the pump inlet to the pump outlet; wherein a primary liquid flow having a mainstream direction from the pump inlet to the pump outlet is coaxially arranged around the motor; and a secondary liquid flow for cooling the motor and lubricating bearings in the pump, wherein the secondary flow is a reverse liquid flow that is substantially opposite to the mainstream direction and passes through the motor from the area of ​​the pump outlet to a radial center space on the upper side of at least one impeller in the area of ​​the pump inlet, and wherein a filter is arranged at the inlet of the secondary liquid flow path.

[0008] By the present invention, an effective and simple solution is provided to provide cooling of the motor and lubrication of the bearings of the pump. The first liquid flow is a main liquid flow, in which the pressure increases from the inlet to the outlet. Due to the pressure difference in the pump, a reverse secondary flow is provided, so that a small part of the main flow is reversed into a secondary flow through the motor to cool the motor and lubricate the bearings.

[0009] By the present invention, it has also been found to be advantageous that a filter is provided at the inlet of the secondary liquid flow path. Thus, the motor and bearings are protected from contamination, thereby extending the life of the pump. It has been found that such a pump can have a very long pump life of up to at least 26,000 hours.

[0010] Furthermore, the main cargo liquid is used to lubricate and cool the motor of the pump, without the need to use a separate liquid for these functions during operation of the pump. This is particularly advantageous and when the cargo is a cryogenic liquid. To ensure proper operation of the filter, the filter is preferably a cryogenic filter.

[0011] The filter is preferably a side flow filter having a substantially radial inlet filter flow and an axial outlet filter flow.Therefore, a backflow can be established in a simple manner.

[0012] In a particular embodiment, the filter is a self-cleaning filter, such as a side stream filter. This improves system cleanliness and is advantageous because the filter can be maintenance free or at least have a long time between servicing.

[0013] In a preferred embodiment, the pump shaft extends below the motor shaft, wherein at least one impeller is mounted to the shaft below the motor. This allows a slender design of the pump. Preferably, a plurality of impellers are provided on the pump shaft to provide a multi-stage centrifugal pump.

[0014] Preferably, the radial central space on the upper side surrounds the pump shaft so that the path of the secondary liquid flow leaves adjacent to the pump shaft on the upper side of at least one impeller. The impeller generates pressure by rotating, thereby forcing the main flow to flow outwards from the radial central area to its periphery. Therefore, the pressure is lowest in the radial central area of ​​the impeller, and this is used to establish the secondary flow.

[0015] In the pump according to the invention, the secondary liquid flow is a partial flow of the main flow. In particular, the secondary liquid flow is a small amount of the main liquid flow, preferably at least 15-35 times smaller, such as about 30 times smaller. The secondary flow is driven when the pressure at the center of the upper side of the impeller is lower than the pressure at the pump outlet. The flow path through the motor and the bearing is designed and dimensioned so that the flow resistance ensures that only a small amount of the main flow passes through the pump in the reverse direction.

[0016] Therein, a plurality of axially oriented flow channels are provided in a stator of an electric machine for cooling, and wherein the channels form a majority of a secondary flow path providing cooling for the electric machine.

[0017] In some preferred embodiments of the pump, a main bearing is provided at the upper end of the motor shaft for absorbing any axial forces provided in the pump. In particular, the main bearing may be a hybrid bearing, in particular a hybrid ball bearing, wherein the bearing is lubricated by a secondary liquid flow.

[0018] Preferably, a lower bearing is also provided at the lower end of the motor shaft for absorbing any radial forces in the pump. The lower bearing may preferably be a carbon guide bearing.

[0019] In the pump described in the present disclosure, preferably, the housing has an inlet housing portion including a plurality of intermediate chambers accommodating the impeller, a lower flow branch portion, a central motor housing portion and an upper flow branch portion and an upper outlet housing portion, and wherein the main flow path is arranged through these housing portions. The housing design allows the first flow (i.e., the main flow) to have a coaxial flow path around the motor so that the main flow also provides cooling of the motor.

[0020] In particular, the housing may be provided with a lower flow branch, the lower flow branch being provided with a flow path for diverting the main flow around the motor, the lower flow branch having a central entry position in fluid communication with the inlet housing portion (i.e., the intermediate chamber), and a radial flow delivery position; and wherein the central housing portion is coaxially provided with a flow channel at a radial position, the flow channel being in fluid communication with the corresponding flow path of the lower flow branch; and wherein the upper flow branch is provided with a flow path between a radially outward receiving position to a central outlet flow outlet, and the radially outward receiving position being in fluid communication with the coaxial flow channel of the central housing portion. The filter is preferably arranged in the upper outlet housing portion. This housing design is advantageous because the lower flow branch portion and the upper flow branch portion can be similar or even identical in shape, which facilitates the manufacture of components and the assembly of the pump. Preferably, the housing portions are provided with external assembly flanges and are assembled to each other by circumferentially arranged support bolts. This further facilitates easy and simple assembly of the pump. DETAILED DESCRIPTION

[0021] The present invention is described below with reference to the accompanying drawings, in which:

[0022] Figure 1 is a side sectional view of a low temperature immersed fuel pump according to an embodiment of the present invention;

[0023] Figure 2 yes Figure 1 A side sectional view of a permanent magnet synchronous motor of a pump in FIG.

[0024] Figure 3 is with Figure 2 A cross-sectional view of the permanent magnet synchronous motor orthogonal to the view;

[0025] Figure 4 is a cross-sectional view of a rotor in a permanent magnet synchronous motor without magnets installed;

[0026] Figure 5 yes Figure 4 A detailed view of part B in FIG.

[0027] Figure 6 yes Figure 5 A detailed view of section C in FIG.

[0028] 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.

[0029] Figure 8 is an end view of the clamping chuck.

[0030] 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.

[0031] 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".

[0032] 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 .

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The rotor body 23 is securely mounted on the motor shaft by any suitable means.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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'.

[0044] 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.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] 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.

[0049] 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 .

[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. An immersed fuel pump for pumping liquefied fluids, in particular a cryogenic immersed fuel pump for pumping liquefied fuels, wherein the liquefied fuels are 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 having a rotor with a hollow motor drive shaft and a stator surrounding the rotor; at least one impeller mounted to the pump shaft for centrifugally moving cryogenic fluid from a pump inlet to a pump outlet; wherein a main liquid flow having a main flow direction from the pump inlet to the pump outlet is arranged coaxially around the motor; and A secondary liquid flow for cooling the motor and lubricating bearings in the pump, wherein the secondary flow is a reverse liquid flow, which is substantially opposite to the main flow direction, from the area of ​​the pump outlet through the motor to the radial central space on the upper side of the at least one impeller in the area of ​​the pump inlet, and wherein a filter is provided at the inlet of the secondary liquid flow path.

2. The pump according to claim 1, wherein The pump shaft extends below the motor shaft, wherein the at least one impeller is mounted to the shaft below the motor.

3. The pump according to claim 1 or 2, wherein: A plurality of impellers are disposed on the pump shaft for providing a multi-stage centrifugal pump.

4. A pump according to any one of the preceding claims, wherein The radial central space on the upper side surrounds the pump shaft such that the path of the secondary liquid flow exits adjacent to the pump shaft on the upper side of the at least one impeller.

5. A pump according to any one of the preceding claims, wherein The filter is a side flow filter having a substantially radial inlet filter flow and an axial outlet filter flow.

6. A pump according to any one of the preceding claims, wherein The filter is a low temperature filter.

7. A pump according to any one of the preceding claims, wherein The filter is a self-cleaning filter.

8. A pump according to any one of the preceding claims, wherein The secondary liquid flow is a partial flow of the primary flow.

9. The pump according to claim 8, wherein The secondary liquid flow is a minor flow of the primary liquid flow, preferably at least 15-35 times smaller, such as about 30 times smaller.

10. A pump according to any one of the preceding claims, wherein The pressure at the central portion of the upper side of the impeller is lower than the pressure at the pump outlet.

11. A pump according to any one of the preceding claims, wherein A plurality of axially oriented flow passages are provided in the stator of the electric machine for cooling, and wherein the passages constitute a majority of the secondary flow path providing cooling for the electric machine.

12. A pump according to any one of the preceding claims, wherein A main bearing is provided at the upper end of the motor shaft for absorbing any axial forces provided in the pump.

13. The pump according to claim 12, wherein The main bearing is a hybrid bearing, in particular a hybrid ball bearing, and wherein the bearing is lubricated by the secondary liquid flow.

14. A pump according to any one of the preceding claims, wherein A lower bearing is provided at the lower end of the motor shaft for bearing any radial forces.

15. The pump according to claim 14, wherein The lower bearing is a carbon guide bearing.

16. A pump according to any one of the preceding claims, wherein The housing has: an inlet housing portion including one or more intermediate chambers for accommodating the impeller; a lower flow branch portion; a central motor housing portion and an upper flow branch portion; and an upper outlet housing portion, and wherein the primary flow path is provided through the housing portion.

17. The pump according to claim 16, wherein The lower flow branch is provided with: a flow path for diverting the main flow around the motor, the lower flow branch having a central entry location in fluid communication with the inlet housing portion and a radial flow delivery location; and wherein The center housing portion is coaxially provided with a flow passage at a radial position, the flow passage being in fluid communication with a corresponding flow path of the lower flow branch; and wherein The upper flow branch defines a flow path between a radially outward receiving location and a center outlet flow outlet, and the radially outward receiving location is in fluid communication with the coaxial flow passage of the center housing portion.

18. A pump according to claim 16 or 17, wherein The housing parts are provided with an outer assembly flange and are assembled to each other by means of circumferentially arranged support bolts.

19. A pump according to any one of claims 5 and 16 to 18, wherein The filter is disposed in the upper outlet housing portion.

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