Electric pump with insulated stator

Abstract

This disclosure relates to an electric pump comprising a casing defining an inlet and an outlet. The electric pump includes a rotor and a stator within the casing. The rotor is cooled by the pump's active fluid, and the stator is positioned in a sealed dry chamber to prevent the active fluid from entering the dry chamber. A heat exchanger is used to cool the stator. A turbine driven by the rotor draws the active fluid into the casing through the inlet. The active fluid passes through the heat exchanger to absorb heat from the stator before reaching the turbine. The active fluid is discharged from the casing by the turbine through the outlet. Figure for the abstract: Fig. 1

Description

Title of the invention: Electric pump with insulated stator Technical field

[0001] The present disclosure relates generally to pumps. More particularly, the present disclosure relates to electric pumps with components cooled by the working fluid of the pumps.

[0002] BACKGROUND

[0003] Electric pumps include a housing defining an inlet and an outlet. A rotor and a stator are mounted in the housing. The stator surrounds the rotor. The rotor includes a shaft coupled to an impeller for moving the working fluid through the housing in a direction from the inlet to the outlet. The housing may be configured such that the working fluid contacts the rotor and stator to provide cooling to the rotor and stator.

[0004] SUMMARY

[0005] The present disclosure relates to an electric pump having a housing defining an inlet and an outlet. The electric pump has a rotor and a stator within the housing. The rotor is cooled by the working fluid of the pump and the stator is positioned in a dry chamber which is sealed to prevent the working fluid from entering the dry chamber. A heat exchanger is used to cool the stator. An impeller driven by the rotor draws the working fluid into the housing through the inlet. The working fluid passes through the heat exchanger to draw heat from the stator before reaching the impeller. At the impeller, the working fluid is pressurized and forced toward the outlet where the working fluid is discharged from the pump. In one example, an insulation sleeve surrounding the rotor is used to isolate the stator from the working fluid which cools (e.g., in a bath) the rotor.In one example, the isolation chamber also prevents the working fluid from applying pressure to the stator. In one example, the turbine is a centrifugal turbine surrounded by a volute passage. In one example, the isolation tube is sealed relative to the housing by means of seals such as radial seals positioned adjacent to opposite ends of the isolation tube.

[0006] Various additional aspects will be indicated in the following description. The aspects may relate to individual features and combinations of features. It is understood that the foregoing general description and the following detailed description are provided by way of example and explanation only and are not limiting of the broad inventive concepts upon which the examples described herein are based. Brief description of the drawings

[0007] The accompanying drawings, which are incorporated in and form an integral part of the specification, illustrate several aspects of the present disclosure. A brief description of the drawings is as follows:

[0008] [Fig.l] is a cross-sectional view of an electric pump in accordance with the principles of the present disclosure;

[0009] [Fig.2] represents a centrifugal turbine and a volute passage of the electric pump of [Fig.l]; and

[0010] [Fig.3] is a cross-sectional view of a two-impeller version of the electric pump of [Fig.l]. DETAILED DESCRIPTION

[0011] Certain aspects of the present disclosure relate to electric pumps having rotor assemblies cooled by a working fluid and stators isolated from the working fluid. In some examples, it may be useful to isolate the stator from the working fluid to prevent the stator from being exposed to relatively high hydraulic pressures associated with the working fluid. For example, a pump designed to convey a working fluid such as supercritical carbon dioxide is often sized to accommodate pump inlet pressures greater than or equal to 137.8951 bar (2,000 pounds per inch (psi)), greater than or equal to 155.132 bar (2,250 psi), or greater than or equal to 172.3689 bar (2,500 psi). In some applications and with certain types of stators, such relatively high pressures may cause damage to portions of the stators (e.g., the stator windings) if the stators are exposed to such pressures.

[0012] [Fig. 1] depicts an electric pump 20 according to the principles of the present disclosure. In some examples, the electric pump 20 may be configured to pump a working fluid having a relatively low viscosity and relatively high inlet pressures. An example of a typical material may include supercritical carbon dioxide. In some examples, the electric pump 20 may be configured to accommodate inlet pressures greater than or equal to 137.8951 bar (2,000 psi), or greater than or equal to 155.132 bar (2,250 psi), or greater than or equal to 172.3689 bar (2,500 psi).

[0013] Referring to [Fig.l], the electric pump 20 includes a housing 22 defining an inlet 24 and an outlet 26. A rotor chamber 28 and a stator chamber 30 are defined within the housing 22. The stator chamber 30 surrounds the rotor chamber 28 and is isolated from the rotor chamber 28 by an isolation sleeve 32. A rotor assembly 34 is positioned within the rotor chamber 28. The rotor assembly 34 includes a rotor shaft 36 that extends along a rotor axis 38. The rotor assembly 34 is rotatable about the rotor axis 38. A stator assembly 40 surrounds the rotor assembly 34. The stator assembly 40 is positioned within the stator chamber 30. The stator chamber 30 is isolated from the rotor chamber 28 such that working fluid present in the rotor chamber 28 is prevented from entering the stator chamber 30. Preferably, the stator chamber 30 is a dry chamber and is configured such that working fluid being pumped through the electric pump is prevented from contacting or applying hydraulic pressure to the stator assembly 40.

[0014] It will be appreciated that the rotor assembly 34 and the stator assembly 40 are configured to operate as an electric motor, with the rotor assembly 34 being the rotating portion of the electric motor and the stator assembly 40 being the non-rotating portion of the electric motor. In some examples, the stator assembly 40 generates magnetic fields that cause the rotor assembly 34 to rotate. It will be appreciated that the rotor assembly 34 and / or the stator assembly 40 may include additions such as wire windings (e.g., copper wire windings), magnets, or other components commonly used in electric motors.

[0015] The electric pump 20 is preferably configured such that the working fluid is allowed to enter the rotor chamber 28 to cool the rotor assembly 34 in a bath. As previously indicated, the insulation sleeve 32 is configured to prevent the entry of the working fluid into the stator chamber 30. In one example, the insulation sleeve 32 is sealed relative to the housing 22 such that the housing and the insulation sleeve 32 cooperate to prevent the working fluid from flowing from the rotor chamber 28 to the stator chamber 30.

[0016] Rather than being cooled by direct contact with the working fluid, the stator assembly 40 is preferably cooled by a heat exchanger 42 through which the working fluid passes. The heat exchanger 42 surrounds the stator assembly 40 and in some examples is in contact with an outer diameter of the stator assembly 40. The working fluid flowing through the heat exchanger 42 draws heat from the stator assembly 40 to cool the stator assembly 40. In one example, the heat exchanger 42 has a metal construction and may be manufactured using an additive manufacturing process. Using an additive manufacturing process, an arrangement of fluid passages may be defined within the heat exchanger 42. The fluid passages are configured to pass in close proximity to the stator assembly 40 to promote efficient transfer of heat from the stator assembly 40 to the working fluid flowing through the heat exchanger 42.

[0017] The electric pump 20 also includes a turbine 44 coupled to the rotor shaft 36 for drawing the working fluid from the inlet 24 through the heat exchanger 42 to a turbine chamber 46 in which the turbine 44 is mounted. The working fluid is pressurized in the turbine chamber 46 and directed toward the outlet 26 of the housing 22 such that the working fluid is discharged from the housing 22 through the outlet 26. In one example, the turbine 44 is a centrifugal turbine and a volute passage 48 is defined by the housing 22 around the turbine 44 (see [Fig. 2]). Rotation of the turbine 44 directs the working fluid out of the turbine chamber 46 into the volute passage 48. The housing 22 may include an impeller cover 80 that attaches to a main body of the housing 22 and defines a portion of the turbine chamber 46. Circulation of the working fluid takes place around the volute passage 48 and is discharged from the pump housing 22 through the outlet 26 (see [Fig. 2]). Diffuser vanes 50 may be provided between the impeller 44 and the scroll passage 48 to help produce a smoother flow around the circumference of the impeller 44 in the scroll passage 48.In one example, the turbine 44 is coaxially aligned with the rotor shaft 36 and rotates in unison with the rotor shaft 46 as the rotor assembly 34 rotates about the rotor axis 38. Thus, the rotor assembly 34 drives the rotation of the turbine 44 about the rotor axis 38.

[0018] The rotor shaft 36 has a first end 52 and a second end 54 opposite the first end. The first end 52 couples to the turbine 44 and is supported by a first bearing 56 coupled to the housing 22 that provides both radial and axial bearing functionality. In one example, the first bearing 56 is attached to the housing 22 so as to be axially fixed along the rotor axis 38. In one example, the first bearing 56 may be configured to support the rotor shaft 36 for rotation about the rotor axis 38 and in some examples, it may be configured as a hydrodynamic bearing such that the rotor shaft 36 is fluidly supported within the bearing 56. The bearing 56 may be disposed between first and second spacers 58, 60 attached to the rotor shaft 36.Thus, the axial contact between the spacers 58, 60 and the bearing 56 limits or restricts the axial movement of the rotor shaft 36 relative to the housing 22 along the rotor axis 38. The second end 54 of the rotor shaft 36 is supported by a second bearing 57 which may provide radial bearing functionality which may include a hydrodynamic bearing. In one example, the second bearing 57 does not function as an axial bearing and the rotor shaft 36 may move axially relative to the radial bearing 57 to allow for thermal expansion and contraction of the rotor shaft 36. In one example, the housing 22 may be configured such that working fluid pressure is allowed to act on the opposite ends of the rotor shaft 36 to provide axial force balancing.In some examples, passages may be provided within the housing 22 to ensure that the working fluid can flow to regions adjacent to the opposite axial ends of the rotor shaft 36.

[0019] In some examples, the insulation sleeve 32 may have a construction composite. For example, the insulation sleeve 32 may include different portions having different material constructions. In one example, the insulation sleeve 32 may include an inner sleeve portion 64 having a metallic construction (e.g., steel or aluminum) and an outer sleeve portion 66 mounted within a recess defined outside the inner sleeve portion 64. In one example, the outer sleeve portion 66 may include a construction that includes carbon fibers. The insulation sleeve 32 is preferably sealed relative to the housing 22. For example, sealing arrangements 39 may be provided adjacent opposite ends of the insulation sleeve 32. In one example, each of the sealing arrangements 39 may include a seal 70 (e.g., a gasket such as an O-ring or the like) and a backing ring 72 to prevent deformation / extrusion of the seal under pressure.In one example, the seals 70 are radial seals mounted in circumferential grooves defined around the circumference of the insulation sleeve 32 adjacent the ends of the insulation sleeve 32. The seals 70 preferably seal at corresponding sealing surfaces defined by the housing 22.

[0020] [Fig. 3] shows another example of an electric pump 120 according to the principles of the present disclosure. The electric pump 120 is similar to the electric pump 20, except that the electric pump 120 has a dual-impeller design, as opposed to the single-impeller design.

[0021] Aspects of the present invention

[0022] Aspect 1. An electric pump for pumping a working fluid, the pump comprising:

[0023] a housing defining an inlet and an outlet;

[0024] a rotor chamber and a stator chamber within the housing, the stator chamber surrounding the rotor chamber and being insulated from the rotor chamber by an insulation sleeve;

[0025] a rotor assembly positioned within the rotor chamber, the rotor assembly including a rotor shaft extending along a rotor axis, the rotor assembly rotatable about the rotor axis;

[0026] the electric pump being configured such that the working fluid is allowed to enter the rotor chamber to cool in a bath the rotor assembly, the insulation sleeve being adapted to prevent the working fluid from entering the stator chamber from the rotor chamber, the stator chamber being a dry chamber;

[0027] a stator assembly surrounding the rotor assembly, the stator assembly being positioned within the stator chamber;

[0028] a heat exchanger positioned around the stator assembly to suck the heat of the stator assembly; and

[0029] a turbine coupled to the rotor shaft for drawing the working fluid from the inlet through the heat exchanger and for discharging the working fluid through the outlet.

[0030] Aspect 2. An electric pump according to aspect 1, wherein the impeller rotates with the shaft about the rotor axis, wherein the impeller is a centrifugal impeller positioned within a turbine chamber of the housing, and wherein the housing defines a volute passage which extends around the impeller to direct working fluid from the impeller to the outlet.

[0031] Aspect 3. An electric pump according to any one of the above aspects, further comprising a diffuser having vanes positioned between the turbine and the volute passage.

[0032] Aspect 4. An electric pump according to any of the above aspects, wherein the electric pump is sized to accommodate inlet pressures greater than 137.8951 bar (2,000 pounds per square inch (psi)) or greater than 155.132 bar (2,250 psi) or equal to 172.3689 bar (2,500 psi).

[0033] Aspect 5. An electric pump according to any one of the above aspects, wherein the working fluid is supercritical carbon dioxide.

[0034] Aspect 6. An electric pump according to any one of the above aspects, wherein the heat exchanger has an additively manufactured metal construction.

[0035] Aspect 7. An electric pump according to any of the above aspects, wherein the rotor shaft has a first end adjacent the impeller supported by a first bearing and an opposite second end supported by a second bearing, the first bearing providing radial and axial bearing functionality and the second bearing providing only radial bearing functionality.

[0036] Aspect 8. An electric pump according to any of the above aspects, wherein the first bearing is coupled to the housing and is captured between spacers coupled to the rotor shaft, and wherein the second bearing is configured to accommodate changes in length of the rotor shaft caused by thermal expansion and contraction.

[0037] Aspect 9. An electric pump according to any of the above aspects, wherein the housing is configured such that the pressure of the working fluid can act on opposite ends of the rotor shaft to provide axial force balancing.

[0038] Aspect 10. An electric pump according to any one of the above aspects, wherein the impeller is a double-sided impeller.

[0039] Aspect 11. An electric pump according to any one of the above aspects, wherein the first and second bearings include hydrodynamic fluid bearings whose force is radially balanced.

[0040] Aspect 12. An electric pump according to any one of the above aspects, wherein the insulation sleeve has a composite construction.

[0041] Aspect 13. An electric pump according to any one of the above aspects, wherein the insulation sleeve includes an inner sleeve portion having a metal construction and an outer sleeve portion mounted to the inner sleeve portion having a carbon fiber construction.

[0042] Aspect 14. An electric pump according to any one of the above aspects, wherein the insulation sleeve has first and second ends, and wherein seals are placed adjacent the first and second ends to provide a seal between the insulation sleeve and the housing.

[0043] Aspect 15. An electric pump according to any one of the above aspects, wherein the seals comprise radial seals supported by reinforcing rings.

Claims

Claims

1. An electric pump for pumping a working fluid, the pump comprising: a housing defining an inlet and an outlet; a rotor chamber and a stator chamber within the housing, the stator chamber surrounding the rotor chamber and being isolated from the rotor chamber by an insulating sleeve having a composite construction; a rotor assembly positioned within the rotor chamber, the rotor assembly comprising a rotor shaft extending along a rotor axis, the rotor assembly being rotatable about the rotor axis; the electric pump being configured such that working fluid is allowed to enter the rotor chamber to cool in a bath the rotor assembly, the insulating sleeve being configured to prevent working fluid from entering the stator chamber from the rotor chamber, the stator chamber being a dry chamber;a stator assembly surrounding the rotor assembly, the stator assembly being positioned within the stator chamber; a heat exchanger positioned around the stator assembly for drawing heat from the stator assembly with an arrangement of fluid passages defined within the heat exchanger; and an impeller coupled to the rotor shaft for drawing working fluid from the inlet through the heat exchanger and for discharging the working fluid through the outlet.;

2. An electric pump according to claim 1, wherein the impeller rotates with the shaft about the rotor axis, wherein the impeller is a centrifugal impeller positioned within a turbine chamber of the housing, and wherein the housing defines a volute passage which extends around the impeller to direct working fluid from the impeller to the outlet.

3. An electric pump according to claim 2, further comprising a diffuser having vanes positioned between the impeller and the volute passage.

4. The electric pump of claim 1, wherein the electric pump is sized to accommodate inlet pressures greater than 137.8951 bar (2,000 pounds per square inch (psi)), or greater than 155.132 bar (2,250 psi) or equal to 172.3689 bar (2,500 psi).

5. An electric pump according to claim 1, wherein the working fluid is supercritical carbon dioxide.

6. An electric pump according to claim 1, wherein the heat exchanger has an additively manufactured metal construction.

7. An electric pump according to claim 1, wherein the rotor shaft has a first end adjacent the impeller supported by a first bearing and an opposite second end supported by a second bearing, the first bearing providing radial and axial bearing functionality and the second bearing providing only radial bearing functionality.

8. An electric pump according to claim 7, wherein the first bearing is coupled to the housing and is captured between spacers coupled to the rotor shaft, and wherein the second bearing is configured to accommodate changes in length of the rotor shaft caused by thermal expansion and contraction.

9. An electric pump according to claim 1, wherein the housing is configured such that the pressure of the working fluid can act on opposite ends of the rotor shaft to provide axial force balancing.

10. 0 An electric pump according to claims 2 and / or 7, wherein the impeller is a two-sided impeller, and wherein the composite construction of the insulation sleeve comprises an inner sleeve portion having a metal construction and an outer sleeve portion mounted on the inner sleeve portion having a carbon fiber construction, the insulation sleeve having a first and a second end, and wherein seals are placed adjacent the first and second ends to seal between the insulation sleeve and the casing, and wherein the seals comprise radial seals supported by reinforcing rings.

11. An electric pump according to claim 1, wherein the insulation sleeve comprises an inner sleeve portion having a metal construction and an outer sleeve portion mounted on the inner sleeve portion having a carbon fiber construction.

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