Integrated motor and fluid pump
An electric pump powered by an electric motor having a stator disposed within a hollow rotor is provided. Impellers on the rotor outer surface extend into a fluid flow path defined by the pump. One or more torque-producing rotor sections are driven by a plurality of independently controllable stator sections disposed within the rotor cavity. The relative positions of the rotor and stator are maintained by a plurality of bearings configured to allow rotation of the rotor and defining a bearing span. The pump is configured such that the stator and rotor share the same bearing span. Such an arrangement reduces motor windage losses relative to conventional motors in which the rotor is disposed within the stator, owing to a reduction in the diameter of the air gap between the stator and the rotor. In addition, the peripheral speed of the pump is increased owing to an increase in the rotor diameter.
1. An electric pump comprising:
(a) a hollow rotor defining a rotor inner surface, a rotor outer surface and a rotor cavity;
(b) a stator comprising a plurality of independently controllable stator sections disposed within the rotor cavity;
(c) a plurality of bearings configured to allow rotation of the hollow rotor;
(d) a fluid recirculation system comprising a production fluid circuit, wherein the production fluid circuit comprises:
a plurality of perforations disposed on a portion of the hollow rotor and located proximate to one or more fluid outlets; the plurality of perforations extending in a radial direction into the hollow rotor; and
a lubrication flow path extending from the plurality of perforations to a fluid flow path defined by the electric pump via the plurality of bearings,
wherein the hollow rotor comprises (i) one or more impellers fixed to the rotor outer surface, and (ii) one or more torque-producing complements to the plurality of independently controllable stator sections.
2. The electric pump according to claim 1 , wherein the stator and the hollow rotor are configured as a squirrel cage induction motor.
3. The electric pump according to claim 1 , wherein the stator and the hollow rotor are configured as an interior permanent magnet motor.
4. The electric pump according to claim 3 , wherein the stator and the hollow rotor are configured as a surface permanent magnet motor.
5. The electric pump according to claim 3 , wherein the stator and the hollow rotor are configured as an inset permanent magnet motor.
6. The electric pump according to claim 1 , wherein the stator and the hollow rotor are configured as a synchronous reluctance motor.
7. The electric pump according to claim 1 , wherein the one or more impellers are configured as a single pump stage.
8. The electric pump according to claim 1 , wherein the one or more impellers are configured as a plurality of pump stages.
9. The electric pump according to claim 8 , wherein at least two of the pump stages are arranged back to back and configured for parallel pumping of a production fluid.
10. The electric pump according to claim 8 , wherein at least two of the pump stages are arranged back to back and configured for series pumping of a production fluid.
11. The electric pump according to claim 1 , wherein one or more of the independently controllable stator sections comprise stator windings arranged in a distributed winding configuration.
12. The electric pump according to claim 1 , wherein one or more of the independently controllable stator sections comprise stator windings arranged in a concentrated winding configuration.
13. The electric pump of claim 1 , wherein the lubrication flow path is configured to receive a portion of a production fluid from the one or more fluid outlets via the plurality of perforations and circulate the portion of the production fluid for lubricating the plurality of bearings.
14. The electric pump of claim 1 , wherein the fluid recirculation system further comprises a processed production fluid circuit, and wherein the processed production fluid circuit comprises:
a conduit;
a separator coupled to the conduit; and
a pressure drop control valve coupled to the conduit, wherein the conduit extends from the separator to the lubrication flow path.
15. The electric pump of claim 14 , wherein the separator is configured to receive a portion of a production fluid from the one or more fluid outlets and separate a liquid-only fraction from the portion of the production fluid, wherein the conduit is configured to circulate the liquid-only fraction to the lubrication flow path for lubricating the plurality of bearings, and wherein the pressure drop control valve is configured to regulate a flow of the liquid-only fraction in the conduit.
16. The electric pump of claim 1 , wherein the fluid recirculation system further comprises a coolant fluid circuit, wherein the coolant fluid circuit comprises:
a closed-loop conduit;
a fluid pump coupled to the closed-loop conduit; and
a cooler coupled to the closed-loop conduit, wherein the closed-loop conduit extends from a cooler to the fluid pump via a stator cooling channel disposed within the stator.
17. The electric pump of claim 16 , wherein the closed-loop conduit is configured to circulate a coolant fluid into the stator cooling channel for absorbing heat from the stator, wherein the fluid pump is configured to regulate a flow of the coolant fluid in the closed-loop conduit, and wherein the cooler is configured to cool the coolant fluid before circulating the coolant fluid into the stator cooling channel.
18. An electric pump comprising:
(a) a hollow rotor defining a rotor inner surface, a rotor outer surface and a rotor cavity;
(b) a stator comprising a plurality of independently controllable stator sections disposed within the rotor cavity;
(c) a plurality of bearings configured to allow rotation of the hollow rotor;
(d) one or more diffusers extending into a fluid flow path defined by the electric pump;
(e) a fluid recirculation system comprising a production fluid circuit, wherein the production fluid circuit comprises:
a plurality of perforations disposed on a portion of the hollow rotor and located proximate to one or more fluid outlets; the plurality of perforations extending in a radial direction into the hollow rotor; and
a lubrication flow path extending from the plurality of perforations to the fluid flow path via the plurality of bearings,
wherein the hollow rotor comprises (i) one or more impellers fixed to the rotor outer surface and extending into the fluid flow path, and (ii) a plurality of torque-producing complements to the plurality of independently controllable stator sections.
19. The electric pump according to claim 18 , wherein the fluid recirculation system is configured to use ambient production fluid as a coolant.
20. The electric pump according to claim 18 , wherein the fluid recirculation system comprises a dedicated fluid cooling circuit configured to cool the stator.
21. The electric pump according to claim 18 , wherein the fluid recirculation system is configured to bring coolant fluid into contact with one or more of the plurality of bearings.
22. The electric pump according to claim 18 , wherein the stator and hollow rotor are configured as a squirrel cage induction motor, an interior permanent magnet motor, a surface permanent magnet motor, an inset permanent magnet motor; a synchronous reluctance motor; or a combination thereof.
23. The electric pump according to claim 18 , wherein the one or more impellers are configured as a plurality of pump stages.
24. An electric pump comprising:
(a) a hollow rotor defining a rotor inner surface, a rotor outer surface and a rotor cavity;
(b) a stator comprising a plurality of independently controllable stator sections disposed within the rotor cavity;
(c) a plurality of bearings configured to allow rotation of the hollow rotor;
(d) one or more diffusers extending into a fluid flow path defined by the electric pump;
(e) a fluid recirculation system comprising a production fluid circuit, wherein the production fluid circuit comprises:
a plurality of perforations disposed on a portion of the hollow rotor and located proximate to one or more fluid outlets; the plurality of perforations extending in a radial direction into the hollow rotor; and
a lubrication flow path extending from the plurality of perforations to the fluid flow path via the plurality of bearings;
(f) a pump housing; and
(g) one or more fluid inlets,
wherein the hollow rotor comprises (i) one or more impellers fixed to the rotor outer surface and extending into the fluid flow path, and (ii) a plurality of torque-producing complements to the plurality of independently controllable stator sections.