Low-temperature immersion type fuel pump

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 moving the cryogenic fluid from the inlet to the outlet; wherein the pump shaft (4) is mounted concentrically in a hollow motor drive shaft (22); and wherein the installation of the pump shaft (4) and the motor drive shaft (22) is a collet collet for interlocking the motor drive shaft (22) and the pump shaft (4) at the tips of these shafts.

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. Because the top end of the pump shaft is provided with a threaded portion engaged by a nut, the pump shaft is mounted on the top of the hollow rotor, and below the motor, a plurality of impellers are mounted to the pump shaft.

[0005] Similar assemblies for coaxially mounting a pump shaft to a motor drive shaft using a threaded portion and a nut are known from US 3,764,236 or JP H07 30396 U. However, this type of assembly can be disadvantageous, particularly under low temperature conditions, because the threaded engagement can loosen during operation of the pump and thereby lose the secure mounting between the two shafts.

[0006] Purpose of the Invention

[0007] The object of the present invention is to provide an improved submerged pump for pumping liquefied fluids, in particular a cryogenic submerged fuel pump for pumping liquefied fuels, which is of compact design and has improved efficiency. Summary of the invention

[0008] 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, liquefied petroleum gas (LPG) or similar liquefied cryogenic medium fluids), wherein the pump includes: a housing having a lower fluid inlet and an upper fluid outlet and accommodating: a vertically oriented pump shaft having a top end and a lower end; a permanent magnet motor having a rotor and a stator, the rotor having a hollow motor drive shaft, the stator surrounding the rotor, the drive shaft having a top end and a lower end; at least one impeller, the impeller being mounted in the region of the lower end of the pump shaft for moving the cryogenic fluid from the inlet to the outlet; wherein the pump shaft is concentrically mounted in the hollow motor drive shaft at the top end of the pump shaft and the top end of the drive shaft; and wherein the mounting of the pump shaft and the motor shaft is a collet clamp connection for interlocking the motor and pump shaft at the top ends of these shafts.

[0009] It was found to be advantageous to use a collet clamp connection between the hollow motor shaft and the pump shaft as this allows a compact design and a secure connection, particularly for the low temperatures at which the pump operates (e.g. cryogenic conditions). The collet clamp connection allows thermal expansion and contraction of the shaft due to the low operating temperatures without compromising the secure fit of the pump shaft in the motor shaft, thereby ensuring that the shaft is securely connected. By the design according to the invention, the pump can be operated at temperatures as low as ÷160°C or even as low as ÷200°C under submerged conditions without air.

[0010] By means of the pump according to the invention a slim design can be provided. Thus, 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. Preferably, a plurality of impellers may be provided on the pump shaft to provide a multi-stage centrifugal pump.

[0011] In an embodiment, the pump shaft is a smooth shaft, such as a rod-like shaft with a constant diameter. This allows simple manufacture and assembly of the pump.

[0012] Advantageously, the collet clamp connection that mounts the pump shaft to the motor shaft is a collet clamp made of an alloy suitable as a low temperature material. More preferably, the alloy is a metal alloy, such as bronze or stainless steel. This ensures a stable and fixed connection under cryogenic conditions.

[0013] In a preferred embodiment, the collet clamp connection comprises a clamping collet having a conical outer clamping surface engaging the hollow motor shaft and a cylindrical inner clamping surface clamping the collet around the pump shaft, and wherein the clamping collet is mounted to the motor shaft by a clamping nut. The clamping collet design allows a secure clamping around the pump shaft and ensures that mutual angular displacement of the motor and pump shafts does not occur during operation of the pump.

[0014] In a preferred embodiment of the pump according to the invention, a main bearing is provided at the upper end of the motor shaft for absorbing any axial forces provided in the pump. This has been found to be advantageous, since only a single bearing is required to absorb the axial forces in the pump. Preferably, the main bearing is a hybrid bearing, in particular a hybrid ball bearing, such as a hybrid ball bearing. Thus, axial forces as well as radial forces can be absorbed.

[0015] Advantageously, a lower bearing is also provided at the lower end of the motor shaft for bearing any radial forces. In one embodiment, the lower bearing may be a carbon guide bearing.

[0016] Preferably, the motor shaft is provided with a coating for additional hardness, such as a spray coating forming a crack-free coating, in order to provide a durable shaft that is resistant to wear. DETAILED DESCRIPTION

[0017] The present invention is described below with reference to the accompanying drawings, in which:

[0018] Figure 1 is a side sectional view of a low temperature immersed fuel pump according to an embodiment of the present invention;

[0019] Figure 2 yes Figure 1 A side sectional view of a permanent magnet synchronous motor of a pump in FIG.

[0020] Figure 3 is with Figure 2 A cross-sectional view of a permanent magnet synchronous motor orthogonal to the view;

[0021] Figure 4 is a cross-sectional view of a rotor in a permanent magnet synchronous motor without magnets installed;

[0022] Figure 5 yes Figure 4 A detailed view of part B in FIG.

[0023] Figure 6 yes Figure 5 A detailed view of section C in FIG.

[0024] 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.

[0025] Figure 8 is an end view of the clamping chuck.

[0026] 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.

[0027] 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".

[0028] 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 .

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] The rotor body 23 is securely mounted on the motor shaft by any suitable means.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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'.

[0040] 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.

[0041] 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.

[0042] 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).

[0043] 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.

[0044] 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.

[0045] 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 .

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 fluid, in particular a cryogenic immersed fuel pump for pumping liquefied fuel, wherein the liquefied fuel is 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 a vertically oriented pump shaft having a top end and a lower end; A permanent magnet motor having a rotor and a stator, the rotor having a hollow motor drive shaft, the stator surrounding the rotor, the drive shaft having a top end and a bottom end; at least one impeller mounted in the region of the lower end of the pump shaft for moving cryogenic fluid from an inlet to an outlet; wherein the pump shaft is concentrically mounted in the hollow motor drive shaft at the top end of the pump shaft and the top end of the motor drive shaft; and wherein the mounting of the pump shaft and the motor drive shaft is a collet clamp connection for interlocking the motor and the pump shaft at the top ends of these shafts.

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 pump shaft is a smooth shaft, such as a rod-like shaft with a constant diameter.

5. A pump according to any one of the preceding claims, wherein The collet clamp connection that mounts the pump shaft to the motor shaft is a collet clamp made from an alloy suitable as a low temperature material.

6. The pump according to claim 5, wherein The alloy is a metal alloy, such as bronze or stainless steel.

7. A pump according to any one of the preceding claims, wherein The collet clamp connection comprises a clamping collet having a conical outer clamping surface engaging the hollow motor shaft and a cylindrical inner clamping surface clamping the collet around the pump shaft, and wherein the clamping collet is mounted to the motor shaft by a clamping nut.

8. The pump according to claim 7, wherein The clamping collet further comprises a conical collar surface, and wherein the clamping nut is provided with an inner surface having a conical shape engaging with the conical collar surface of the collet clamp.

9. The pump according to claim 8, wherein The clamping nut is threadedly engaged on the end section of the motor shaft.

10. 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.

11. The pump according to claim 10, wherein The main bearing is a hybrid bearing, in particular a hybrid ball bearing.

12. 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 absorbing any radial forces.

13. The pump according to claim 12, wherein The lower bearing is a carbon guide bearing.

14. A pump according to any one of the preceding claims, wherein The motor shaft is provided with a coating for additional hardness, such as a spray coating that results in a crack-free coating.

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