Multistage turbomachine with embedded electric motors

Patent metadata

Field	Value
Publication number	US-10294949-B2
Application number	US-201515115722-A
Country	US
Kind code	B2
Filing date	Feb 2, 2015
Priority date	Feb 3, 2014
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

A multistage turbomachine is disclosed, comprising a casing with a fluid inlet and a fluid outlet and a plurality of stages arranged in the casing. A flow path extends from the fluid inlet to the fluid outlet through the sequentially arranged stages. Each stage is comprised of a rotating impeller and an electric motor embedded in the casing and arranged for rotating the impeller at a controlled rotary speed. Each electric motor comprises a motor rotor, arranged on the impeller and integrally rotating therewith, and a motor stator stationarily arranged in the casing. Pairs of sequentially arranged impellers are configured for rotation in opposite directions.

First claim

What is claimed is:

1. A multistage turbomachine, comprising:
a casing with a fluid inlet and a fluid outlet; and
a plurality of stages sequentially arranged in the casing with a first stage positioned adjacent the fluid inlet, a last stage positioned adjacent the fluid outlet and at least one intermediate stage positioned between the first stage and the last stage; wherein:
a flow path extends from the fluid inlet to the fluid outlet through the sequentially arranged stages;
each stage is comprised of a rotating impeller and an electric motor embedded in the casing and arranged for rotating the impeller at a controlled rotary speed;
each electric motor comprises a motor rotor arranged on the impeller and integrally rotating therewith and a motor stator stationarily arranged in the casing;
pairs of sequentially arranged impellers are configured for rotation in opposite directions; and
a control arrangement configured and arranged to rotate each impeller at a rotational speed which can vary from one impeller to the other,

wherein the control arrangement controls the rotary speed of the stages to be identical at a set gas volume fraction (GVF) %; if the GVF % becomes lower than the set GVF %, the control arrangement controls the rotary speed of the first stage to be decreased and the rotary speed of the at least one intermediate stage to be increased; and if the GVF % becomes higher than the set GVF %, the control arrangement controls the rotary speed of the first stage to be increased and the rotary speed of the at least one intermediate stage to be decreased.

2. The turbomachine of claim 1 ,
wherein at least some of the stages comprise serially arranged axial impellers and at least some of the stages comprise serially arranged radial impellers.

3. The turbomachine of claim 1 , wherein the impellers rotating in opposite directions are arranged directly adjacent to one another.

4. The turbomachine of claim 1 , wherein the control arrangement is configured for controlling at least one parameter of the electric motors as a function of at least one compressibility-related parameter.

5. The turbomachine of claim 4 , wherein the at least one parameter of the electric motors is selected from the group consisting of: the rotational speed, the torque, the power, or a combination thereof.

6. The turbomachine of claim 4 , wherein the at least one compressibility-related parameter is proportional to the gas volume fraction of the fluid.

7. The turbomachine of claim 1 , further comprising a central, non-rotating shaft.

8. The turbomachine of claim 1 , wherein the impellers of at least some of the stages are supported on the respective motor stators by respective bearings.

9. The turbomachine of claim 1 , wherein the motor stator of at least some of the stages is arranged around the respective motor rotor mounted on the impeller, wherein the motor stator is surrounding the motor rotor.

10. The turbomachine of claim 1 , further comprising supporting bearings lubricated and cooled by the fluid processed by the turbomachine.

11. The turbomachine of claim 1 , further comprising:
a liquid/gas separator arranged downstream of the fluid outlet; and
at least one of a liquid recirculating duct and a gas recirculating duct;
wherein the liquid recirculating duct is in fluid communication with liquid-refrigerated supporting bearings of at least some of the impellers, and/or the gas recirculating duct is in fluid communication with a gap between the motor stator and the motor rotor of at least some of the impellers.

12. The turbomachine of claim 1 , wherein the motor rotor of at least some of the stages comprises permanent magnets.

13. The turbomachine of claim 12 , wherein at least some of the impellers are provided with an impeller shroud, and wherein the permanent magnets thereof are arranged at the shroud of the respective impeller.

14. The turbomachine of claim 1 , wherein each stage comprises a power control circuit arranged in the casing, configured to control the relevant electric motor.

15. The turbomachine of claim 1 , wherein the rotary speeds of the stage impellers are controlled so as to be reduced from upstream to downstream, upon an increase of fluid density across the stages.

16. The turbomachine of claim 1 , wherein the embedded electric motors comprise a motor stator with a modular structure, comprised of a plurality of yokes circumferentially arranged around a rotation axis, each yoke including at least one electric coil wound around a respective magnetic core.

17. A method for boosting the pressure of a variable-compressibility fluid, the method comprising:
sequentially arranging a plurality of impellers for rotation in a casing of a turbomachine with a first impeller positioned adjacent a fluid inlet of the casing, a last impeller positioned adjacent a fluid outlet of the casing and at least one intermediate impeller positioned between the first impeller and the last impeller;
rotating the sequentially arranged impellers in opposite directions with a respective electric motor embedded in the casing;
processing a fluid through the impellers;
boosting a fluid pressure from a suction pressure to a delivery pressure;
controlling at least one operating parameter of the embedded motors such that impellers rotate at different rotational speeds;
controlling the rotary speed of the impellers to be identical at a set gas volume fraction (GVF) %;
controlling the rotary speed of the first stage to be decreased and the rotary speed of the at least one intermediate stage to be increased if the GVF % becomes lower than the set GVF %; and
controlling the rotary speed of the first stage to be increased and the rotary speed of the at least one intermediate stage to be decreased if the GVF % becomes higher than the set GVF %.

18. The method of claim 17 , wherein the at least one operating parameter of the embedded motors is controlled as a function of a parameter related to compressibility of the fluid.

19. The method of claim 17 , further comprising rotating the embedded motors at a rotational speed which decreases from a most upstream impeller to a most down-stream impeller.

20. The method of claim 18 , further comprising rotating the embedded motors at a rotational speed which decreases from a most upstream impeller to a most down-stream impeller, and wherein a speed difference between the most upstream impeller and the most downstream impeller is set as a function of a parameter related to the compressibility of the fluid.

Assignees

• Nuovo Pignone Srl

Inventors

• Bergamini Lorenzo
• Cipriani Marco

Classifications

• F04D17/122

  the individual rotor discs being, one for each stage, on a common shaft and axially spaced, e.g. conventional centrifugal multi- stage compressors · CPC title

• F04D29/181

  Axial flow rotors (F04D29/185 take precedence) · CPC title

• F04D15/0066

  by changing the speed, e.g. of the driving engine · CPC title

• F04D19/024

  with contrarotating parts · CPC title

• F04D19/026

  with a plurality of shafts rotating at different speeds (F04D19/022 takes precedence) · CPC title