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Title:
CENTRIFUGAL COMPRESSOR HAVING AN INTEGRATED ELECTRIC MOTOR
Document Type and Number:
WIPO Patent Application WO/2019/199318
Kind Code:
A1
Abstract:
Single-and multi-stage compressors independently drive impellers in each compressor stage with one or more electric motors that are incorporated in the compressor casing. In multi-stage embodiments, impellers in respective compressor stages are capable of being driven at different rotational speeds. In some embodiments, the electric motor is a ring-type electric motor, where the rotor is coupled to a circumscribing impeller. The rotor in turn circumscribes the stator. In other embodiments, the electric motor is a flat or pancake-type electric motor, where its rotor is coupled to an axial sidewall of the impeller, and its stator is disposed axially outboard of and in opposed relationship with the rotor body. In some embodiments, the compressor stage incorporates a pair of flat or pancake-type electric motors. In some embodiments, rotors of the electric motors have permanent magnet-type rotor magnets, while in other embodiments the rotor magnets are electromagnetic rotor magnets.

Inventors:
KUZDZAL, Mark J. (3294 West Valley View, Allegany, New York, 14706, US)
Application Number:
US2018/027488
Publication Date:
October 17, 2019
Filing Date:
April 13, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
DRESSER-RAND COMPANY (500 Paul Clark Drive, Olean, New York, 14760, US)
International Classes:
F04D25/06; F04D17/12; F04D29/058
Domestic Patent References:
WO1996018818A11996-06-20
WO2015114136A12015-08-06
WO2016158173A12016-10-06
Foreign References:
US20150104335A12015-04-16
US8632302B22014-01-21
Attorney, Agent or Firm:
MORA, Enrique J. (Siemens Corporation- Intellectual Property Dept, 3501 Quadrangle Blvd. Ste. 230Orlando, Florida, 32817, US)
Download PDF:
Claims:
CLAIMS

What is claimed is:

1. A compressor, comprising:

a compressor casing, defining an impeller cavity;

a diffuser, in fluid communication with the impeller cavity;

an impeller disposed within and circumscribed by the impeller cavity, and configured to rotate therein about a longitudinal axis of the compressor; and

an electric motor, disposed within the compressor casing, and circumscribed by the impeller cavity, for driving the impeller, the electric motor having:

a rotor coupled to a surface of the impeller and including a plurality of rotor magnets that are electromagnets or permanent magnets; and

a stator coupled to the compressor casing, in opposing, spaced relationship to the rotor, and including a plurality of electromagnets configured to generate a magnetic field for rotating the rotor and only the impeller that is coupled thereto.

2. The compressor of claim 1, further comprising:

the rotor including an annular rotor body retaining the plurality of rotor magnets; and

the stator including an annular stator body, the annular rotor body being disposed radially outward of the annular stator body,

wherein the magnetic field generated by the stator centers the rotor in the impeller cavity in a single axial position, relative to the longitudinal axis of the compressor.

3. The compressor of claim 2, further comprising:

a stationary diaphragm coupled to the casing, and defining at least a portion of the impeller cavity;

the impeller having an inner annular surface defining a central opening through which a portion of the stationary diaphragm extends, the inner annular surface further defining an annular groove; and

the annular rotor body seated within the annular groove defined in the inner annular surface of the impeller.

4. The compressor of claim 2, further comprising the annular stator body defining an annular groove configured to seat therein a second plurality of stator electromagnets, for supporting and positioning the impeller within the impeller cavity axially and radially.

5. The compressor of claim 1, further comprising:

the impeller having a pair of axially oriented sidewalls, respectively defining sidewall surfaces, and radially oriented blades between the sidewalls, relative to the longitudinal axis of the compressor, the impeller blades terminating in blade tips;

the diffuser axially and radially aligned with the blade tips of the impeller;

the rotor of the electric motor including an annular rotor body retaining the plurality of rotor magnets coupled to one of the sidewall surfaces of the impeller; and the stator of the electric motor including an annular stator body disposed axially outboard of and in opposed relationship with the rotor body.

6. The compressor of claim 5, further comprising a pair of first and second electric motors, axially flanking the axially oriented sidewalls of the impeller, each electric motor respectively having its annular rotor body coupled to its respective, opposing sidewall surface of the impeller, and its annular stator body coupled to the compressor casing in opposing, axially spaced relationship with its rotor body.

7. The compressor of claim 6, further comprising:

the impeller having a hollow annular hub concentrically aligned with the longitudinal axis of the compressor and projecting axially from both of the axially oriented sidewalls thereof, the hub defining respective inner and outer annular surfaces; the compressor casing axially extending into the inner annular surface of the hub in opposed relationship;

the annular stator body of each respective electric motor concentrically nested over the outer annular surface of its corresponding hub;

a second plurality of electromagnets, for supporting and positioning the impeller within the impeller cavity, interposed between the inner annular surface of the hub and a portion of the compressor casing that extends axially therein.

8. The compressor of claim 7, further comprising:

the compressor casing defining an inlet, circumscribed by the inner annular surface of the impeller hub, that is in fluid communication with impeller cavities, formed between the impeller blades and the axially oriented sidewalls of the hub, and with the diffuser.

9. The compressor of claim 1, further comprising a controller operably controlling distribution of electrical energy by an electrical power source to each respective plurality of electromagnets in the stator thereof, for selectively varying rotational speed of the impeller.

10. A compressor comprising:

a longitudinal axis;

a compressor casing extending along the longitudinal axis, and defining therein a plurality of sequential compression stages that are in fluid communication with each other;

an inlet coupled to the compressor casing and configured to receive a process fluid from a process fluid source;

each of the plurality of compression stages fluidly coupled with the inlet and configured to compress the process fluid, each compression stage having:

an impeller cavity in the compressor casing;

a diffuser in the compressor casing, in fluid communication with the impeller cavity;

an impeller disposed within and circumscribed by the impeller cavity, and configured to rotate therein about the longitudinal axis of the compressor independently of at least one other impeller of the compressor; and

an electric motor, disposed within the compressor casing, and circumscribed by the impeller cavity, for driving the impeller, the electric motor having:

a rotor coupled to a surface of the impeller and including a plurality of rotor magnets that are electromagnets or permanent magnets; and

a stator coupled to the compressor casing, in opposing, spaced relationship to the rotor, and including a plurality of electromagnets configured to generate a magnetic field for rotating the rotor and only the impeller that is coupled thereto; and a volute fluidly coupled to a last compression stage of the plurality of compression stages and configured to discharge the process fluid from the compressor.

11. The compressor of claim 10, at least one of the electric motors in one of the compression stages further comprising:

the rotor including an annular rotor body retaining the plurality of rotor magnets; and

the stator including an annular stator body, the annular rotor body being disposed radially outward of the annular stator body,

wherein the magnetic field generated by the stator centers the rotor in the impeller cavity in a single axial position, relative to the longitudinal axis of the compressor.

12. The compressor of claim 10, at least one of the compression stages further comprising:

the impeller having a pair of axially oriented sidewalls, respectively defining sidewall surfaces, and radially oriented blades between the sidewalls, relative to the longitudinal axis of the compressor, the impeller blades terminating in blade tips;

the diffuser axially and radially aligned with the blade tips of the impeller;

the rotor of the electric motor including an annular rotor body retaining the plurality of rotor magnets coupled to one of the sidewall surfaces of the impeller; and the stator of the electric motor including an annular stator body disposed axially outboard of and in opposed relationship with the rotor body.

13. The compressor of claim 12, said at least one of the compression stages further comprising a pair of first and second electric motors, axially flanking the axially oriented sidewalls of the impeller, each electric motor respectively having its annular rotor body coupled to its respective, opposing sidewall surface of the impeller, and its annular stator body coupled to the compressor casing in opposing, axially spaced relationship with its rotor body.

14. The compressor of claim 13, said at least one of the compression stages further comprising:

the impeller having a hollow annular hub concentrically aligned with the longitudinal axis of the compressor and projecting axially from both of the axially oriented sidewalls thereof, the hub defining respective inner and outer annular surfaces; the compressor casing axially extending into the inner annular surface of the hub in opposed relationship;

the annular stator body of each respective electric motor concentrically nested over the outer annular surface of its corresponding hub;

a second plurality of electromagnets, for supporting and positioning the impeller within the impeller cavity, interposed between the inner annular surface of the hub and a portion of the compressor casing that extends axially therein.

15. The compressor of claim 10, further comprising a controller operably controlling distribution of electrical energy by an electrical power source to each respective plurality of electromagnets in the stator of each of the respective electric motors in each of the compression stages, for selectively varying rotational speed of the impeller therein.

16. A method of operating a compressor, comprising:

fluidly coupling a process fluid source with an inlet of the compressor, the compressor having a longitudinal axis, a compressor casing extending along the longitudinal axis, and defining therein a plurality of sequential compression stages that are in fluid communication with the compressor inlet and each other, each compression stage having:

an impeller cavity in the compressor casing;

a diffuser in the compressor casing, in fluid communication with the impeller cavity;

an impeller disposed within and circumscribed by the impeller cavity, and configured to rotate therein about the longitudinal axis of the compressor independently of at least one other impeller of the compressor; and an electric motor, disposed within the compressor casing, and circumscribed by the impeller cavity, for driving the impeller, the electric motor having:

a rotor coupled to a surface of the impeller and including a plurality of rotor magnets; and

a stator coupled to the compressor casing, in opposing, spaced relationship to the rotor, and including a plurality of electromagnets configured to generate a magnetic field for rotating the rotor and only the impeller that is coupled thereto; in each compression stage, driving each respective impeller with its respective electric motor independently of other compression stages;

compressing the process fluid flowing through each of the compression stages to form a compressed process fluid; and

discharging the compressed process fluid from the compressor.

17. The method of claim 16, wherein driving each impeller in each respective compression stage with its respective electric motor further comprises rotating at least one impeller in one compression stage at a different rotational speed than that of another impeller in another compression stage.

18. The method of claim 16, further comprising:

detecting a parameter of the process fluid at a location in the compressor via one or more sensors; and

setting a rotational speed of a first impeller in one compression stage independently of rotational speed of a second impeller in another compression stage, in response to the process fluid parameter detected by at least one of the one or more sensors.

19. The method of claim 18, further comprising setting the rotational speed of the first impeller in the one compression stage with a controller that operably controls distribution of electrical energy by an electrical power source to each respective plurality of electromagnets in the stator of the electric motor driving the first impeller, the controller receiving a signal generated by at least one sensor of the at least one of the one or more sensors that is indicative of a parameter of the process fluid and setting the rotational speed of the first impeller based on the received signal.

20. The method of claim 19, further comprising: driving each impeller in each respective compression stage with its respective electric motor, under common control of the controller or under distributed control by a plurality of different controllers that are respectively coupled to one or more dedicated compression stages of the compressor.

Description:
CENTRIFUGAL COMPRESSOR HAVING AN INTEGRATED

ELECTRIC MOTOR

BACKGROUND

[0001] The invention relates to compressors. More particularly, the invention relates to compressors with integrated electric motor drives.

[0002] Compressors and systems incorporating compressors are often utilized in numerous industrial environments ( e.g ., petroleum refineries, offshore oil production platforms, and subsea process-control systems). Conventional compressors compress a process fluid by applying kinetic energy to the process fluid to transport the process fluid from a low-pressure environment to a high-pressure environment. In some applications, the compressed process fluid discharged from the compressors is utilized to perform work efficiently, or operate one or more downstream processes or components thereof.

[0003] Generally, compressors, such as centrifugal compressors, include a rotary shaft having one or more impellers mounted thereto, each of the impellers being configured to increase the static pressure and/or the velocity of the process fluid flowing therethrough. The rotary shaft is typically supported by a plurality of radial bearings and driven by an external driver, such as a motor, an internal combustion engine, or a turbine. To that end, the driver may include a drive shaft typically coupled to the rotary shaft of the compressor via a gearbox to allow the rotary shaft to spin at varying speeds, to adjust, amongst other properties, the pressure and/or flow rate of the compressed process fluid discharged from the compressor.

[0004] Compressors employing rotary shafts as disclosed above are susceptible to certain drawbacks. For example, as each impeller is mounted to the rotary shaft, the impellers are constrained to rotate at the same speed, thereby preventing each impeller from rotating at an optimized speed thereof to provide for maximum efficiency of the compressor. In addition, many operating sites of the compressor may have limited footprint space (e.g., offshore oil production sites), and as such, there is an increased interest and demand for more compact compressors. In compressors employing rotary shafts, the radial bearings supporting the rotary shaft are typically disposed in bearing housings at each end of the compressor, thereby inhibiting a reduction in size of the compressor. Further, in instances in which the compressor is driven by an external driver coupled thereto via a gearbox, the space constraints at the operating site may prevent the use of the compressor, or call for the elimination of other process components or support facilities to accommodate the compressor, driver, and gearbox.

SUMMARY

[0005] Exemplary embodiments described herein feature a compressor. The compressor includes a compressor casing, defining an impeller cavity. A diffuser is in fluid communication with the impeller cavity. An impeller is disposed within and circumscribed by the impeller cavity. It is configured to rotate in the impeller cavity about a longitudinal axis of the compressor. An electric motor is disposed within the compressor casing, and circumscribed by the impeller cavity, for driving the impeller. The electric motor has a rotor coupled to a surface of the impeller. It includes a plurality of rotor magnets that are electromagnets or permanent magnets. The motor has a stator coupled to the compressor casing, in opposing, spaced relationship to the rotor. The stator includes a plurality of electromagnets configured to generate a magnetic field, for rotating the rotor and only the impeller that is coupled thereto.

[0006] Other exemplary embodiments of the disclosure feature a multi-stage compressor comprising a longitudinal axis, with a compressor casing extending along the longitudinal axis, and defining therein a plurality of sequential compression stages that are in fluid communication with each other. An inlet is coupled to the compressor casing and configured to receive a process fluid from a process fluid source. Each of the plurality of compression stages is fluidly coupled with the inlet and configured to compress the process fluid. Each compression stage has an impeller cavity in the compressor casing. Each compression stage has a diffuser in the compressor casing, in fluid communication with the impeller cavity. An impeller is disposed within and circumscribed by the impeller cavity, and configured to rotate therein about the longitudinal axis of the compressor, independently of at least one other impeller of the compressor. An electric motor is disposed within the compressor casing, and circumscribed by the impeller cavity, for driving the impeller. Each electric motor has a rotor coupled to a surface of the impeller and includes a plurality of rotor magnets that are electromagnets or permanent magnets. A stator is coupled to the compressor casing, in opposing, spaced relationship to the rotor. Each stator includes a plurality of electromagnets configured to generate a magnetic field for rotating the rotor and only the impeller that is coupled to it. The compressor has a volute fluidly coupled to a last compression stage of the plurality of compression stages, which is configured to discharge the process fluid from the compressor.

[0007] Additional exemplary embodiments provide a method for operating a compressor, by fluidly coupling a process fluid source with an inlet of the compressor. The compressor has a longitudinal axis. The compressor casing extends along the longitudinal axis, and defines therein a plurality of sequential compression stages that are in fluid communication with the compressor inlet and each other. Each compression stage has an impeller cavity in the compressor casing, and a diffuser in the compressor casing, in fluid communication with the impeller cavity. An impeller is disposed within and circumscribed by the impeller cavity. The impeller is configured to rotate within the impeller cavity about the longitudinal axis of the compressor independently of at least one other impeller of the compressor. An electric motor is disposed within the compressor casing, and circumscribed by the impeller cavity, for driving the impeller. The electric motor has a rotor coupled to a surface of the impeller and includes a plurality of rotor magnets. A stator of the electric motor is coupled to the compressor casing, in opposing, spaced relationship to the rotor. It includes a plurality of electromagnets configured to generate a magnetic field for rotating the rotor and only the impeller that is coupled thereto. In each compression stage, each respective impeller is driven with its respective electric motor independently of other compression stages. The process fluid flowing through each of the compression stages is compressed to form a compressed process fluid, which is subsequently discharged by the compressor. [0008] The respective features of the exemplary embodiments of the invention that are described herein are applied jointly or severally in any combination or sub- combination.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present disclosure is best understood from the following detailed description when read with the accompanying Figures.

[0010] Figures 1A-1C illustrate a longitudinal, cross-sectional view of three stages of an exemplary multi-stage compressor, according to one or more embodiments.

[0011] Figure 2 illustrates an exploded view of an exemplary ring-type electric motor with the compressor omitted for clarity purposes, according to one or more embodiments.

[0012] Figure 3 is a schematic, longitudinal, cross-sectional view of another exemplary embodiment of a multi-stage compressor, which incorporates flat or pancake-type motors.

[0013] Figure 4 illustrates a fragmentary cross-sectional view of a stage of the compressor of Figure 3.

[0014] Figure 5 illustrates an exploded view of the impeller and motor of the compressor stage of Figure 4.

[0015] Figure 6 illustrates a flowchart depicting a method for operating a compressor, according to one or more embodiments disclosed.

[0016] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale. DETAILED DESCRIPTION

[0017] Single-and multi-stage compressor embodiments described herein independently drive respective impellers in each compressor stage with one or more electric motors that are incorporated in the compressor casing of that compressor stage. In multi-stage embodiments, impellers in respective compressor stages are capable of being driven at different rotational speeds. In some embodiments, the electric motor is a ring-type electric motor, where the rotor is coupled to a circumscribing impeller. The rotor in turn circumscribes the stator. In other embodiments, the electric motor is a flat or pancake-type electric motor, where its rotor is coupled to an axial sidewall of the impeller, and its stator is disposed axially outboard of and in opposed relationship with the rotor body. In some embodiments, rotors of the electric motors have permanent magnet-type rotor magnets, while in other embodiments the rotor magnets are electromagnetic rotor magnets.

[0018] Figures 1A-1C illustrate a longitudinal, cross-sectional view of an exemplary compressor 100, according to one or more embodiments. As illustrated, the compressor 100 is a radial-inlet centrifugal compressor. In other embodiments, the compressor 100 may be an axial-inlet centrifugal compressor. The compressor 100 is configured to compress or pressurize a process fluid received from a process fluid source or an upstream process component (not shown).

[0019] The process fluid pressurized, circulated, contained, or otherwise utilized in the compressor 100 may be a fluid in a liquid phase, a gas phase, a supercritical state, a subcritical state, or any combination thereof. The process fluid may be a mixture. The process fluid may include one or more high molecular weight process fluids, one or more low molecular weight process fluids, or any mixture or combination thereof.

[0020] As used herein, the term "high molecular weight process fluids" refers to process fluids having a molecular weight of about 30 grams per mole (g/mol) or greater. Illustrative high molecular weight process fluids may include, but are not limited to, hydrocarbons, such as ethane, propane, butanes, pentanes, and hexanes. Illustrative high molecular weight process fluids may also include, but are not limited to, carbon dioxide (CO2) or process fluid mixtures containing carbon dioxide. As used herein, the term "low molecular weight process fluids" refers to process fluids having a molecular weight less than about 30 g/mol. Illustrative low molecular weight process fluids may include, but are not limited to, air, hydrogen, methane, or any combination or mixtures thereof.

[0021] In an exemplary embodiment, the compressor 100 may have a compression ratio of at least about 6:1 or greater. For example, the compressor 100 may compress the process fluid to a compression ratio of about 6:1, about 6.1:1, about 6.2:1, about 6.3:1, about 6.4:1, about 6.5:1, about 6.6:1, about 6.7:1, about 6.8:1, about 6.9:1, about 7:1, about 7.1:1, about 7.2:1, about 7.3:1, about 7.4:1, about 7.5:1, about 7.6:1, about 7.7:1, about 7.8:1, about 7.9:1, about 8:1, about 8.1:1, about 8.2:1, about 8.3:1, about 8.4:1, about 8.5:1, about 8.6:1, about 8.7:1, about 8.8:1, about 8.9:1, about 9:1, about 9.1:1, about 9.2:1, about 9.3:1, about 9.4:1, about 9.5:1, about 9.6:1, about 9.7:1, about 9.8:1, about 9.9:1, about 10:1, about 10.1:1, about 10.2:1, about 10.3:1, about 10.4:1, about 10.5:1, about 10.6:1, about 10.7:1, about 10.8:1, about 10.9:1, about 11:1, about 11.1:1, about 11.2:1, about 11.3:1, about 11.4:1, about 11.5:1, about 11.6:1, about 11.7:1, about 11.8:1, about 11.9:1, about 12:1, about 12.1:1, about

12.2:1, about 12.3:1, about 12.4:1, about 12.5:1, about 12.6:1, about 12.7:1, about

12.8:1, about 12.9:1, about 13:1, about 13.1:1, about 13.2:1, about 13.3:1, about

13.4:1, about 13.5:1, about 13.6:1, about 13.7:1, about 13.8:1, about 13.9:1, about

14:1, or greater.

[0022] The compressor 100 may be a supersonic compressor or a subsonic compressor. The compressor 100 includes a plurality of compression stages (three shown l02a-c). Each compression stage l02a-c of the compressor 100 may be a subsonic compression stage or a supersonic compression stage. In at least one embodiment, the compressor 100 may include a plurality of subsonic compression stages. In another embodiment, the compressor 100 may include at least one subsonic compression stage and at least one supersonic compression stage. In other embodiments, the compressor is a single-stage, subsonic or supersonic compressor.

[0023] Any one or more compression stages l02a-c of the compressor 100 may have a compression ratio greater than about 1:1. For example, any one or more compression stages l02a-c of the compressor 100 may have a compression ratio of about 1.1:1, about 1.2:1, about 1.3:1, about 1.4:1, about 1.5:1, about 1.6:1, about

I.7:1, about 1.8:1, about 1.9:1, about 2:1, about 2.1:1, about 2.2:1, about 2.3:1, about 2.4:1, about 2.5:1, about 2.6:1, about 2.7:1, about 2.8:1, about 2.9:1, about 3:1, about 3.1:1, about 3.2:1, about 3.3:1, about 3.4:1, about 3.5:1, about 3.6:1, about 3.7:1, about 3.8:1, about 3.9:1, about 4:1, about 4.1:1, about 4.2:1, about 4.3:1, about 4.4:1, about 4.5:1, about 4.6:1, about 4.7:1, about 4.8:1, about 4.9:1, about 5:1, about 5.1:1, about 5.2:1, about 5.3:1, about 5.4:1, about 5.5:1, about 5.6:1, about 5.7:1, about 5.8:1, about 5.9:1, about 6:1, about 6.1:1, about 6.2:1, about 6.3:1, about 6.4:1, about 6.5:1, about 6.6:1, about 6.7:1, about 6.8:1, about 6.9:1, about 7:1, about 7.1:1, about 7.2:1, about 7.3:1, about 7.4:1, about 7.5:1, about 7.6:1, about 7.7:1, about 7.8:1, about 7.9:1, about 8.0:1, about 8.1:1, about 8.2:1, about 8.3:1, about 8.4:1, about 8.5:1, about 8.6:1, about 8.7:1, about 8.8:1, about 8.9:1, about 9:1, about 9.1:1, about 9.2:1, about 9.3:1, about 9.4:1, about 9.5:1, about 9.6:1, about 9.7:1, about 9.8:1, about 9.9:1, about 10:1, about 10.1:1, about 10.2:1, about 10.3:1, about 10.4:1, about 10.5:1, about 10.6:1, about 10.7:1, about 10.8:1, about 10.9:1, about 11:1, about

II.1:1, about 11.2:1, about 11.3:1, about 11.4:1, about 11.5:1, 11.6:1, about 11.7:1, about 11.8:1, about 11.9:1, about 12:1, about 12.1:1, about 12.2:1, about 12.3:1, about 12.4:1, about 12.5:1, about 12.6:1, about 12.7:1, about 12.8:1, about 12.9:1, about 13:1, about 13.1:1, about 13.2:1, about 13.3:1, about 13.4:1, about 13.5:1, about 13.6:1, about 13.7:1, about 13.8:1, about 13.9:1, about 14:1, or greater. In an exemplary embodiment, the compressor 100 may include a plurality of compression stages l02a-c, where a first compression stage l02a (Figure 1A) of the plurality of compressor stages l02a-c may have a compression ratio of about 1.4:1, a second compression stage l02b (Figure 1B) of the plurality of compressor stages may have a compression ratio of about 1.3:1, and a third or last compression stage l02c (Figure 1C) may have a compression ratio of about 1.2:1. [0024] As illustrated in Figures 1A-1C, the compressor 100 includes a casing 104 configured to support and/or protect one or more components of the compressor 100. The casing 104 may also be hermetically sealed and thus configured to contain the process fluid flowing through one or more portions or components of the compressor 100. To that end, as shown in Figure 1A, the compressor 100 includes an inlet 106 e.g ., a radial inlet) coupled to the casing 104 and defining in conjunction with the casing 104 an inlet cavity 108 configured to receive and direct the process fluid to the first compression stage l02a of the plurality of compression stages l02a-c.

[0025] Each of the respective compression stages l02a-c includes an impeller l lOa-c and a stationary diaphragm H2a-c. As shown, each of the stationary diaphragms H2a-c is coupled to the casing 104. Each stationary diaphragm H2a-c defines an impeller cavity H4a-c and a diffuser H6a-c fluidly coupled to the impeller cavity H4a-c. As illustrated in Figures 1A-1C, the impellers l lOa-c are disposed in respective impeller cavities 1 l4a-c and configured to rotate therein.

[0026] The compression stages l02b and l02c further include respective return channels 118b and 118c fluidly coupled to the respective diffusers 116a and 116b of the immediate upstream compression stages l02a and l02b. The compressor 100 further includes a collector or volute 120 fluidly coupled with the diffuser 116c of the last compression stage l02c. Accordingly, as arranged, the compressor 100 may have a fluid pathway (indicated by the“—“ line and arrows) through which the process fluid may flow, the fluid pathway being formed from the inlet cavity 108, the impeller cavities H4a-c, the diffusers H6a-c, the return channels 118b, 118c, and the volute 120.

[0027] As illustrated in Figures 1A-1C, the compressor 100 includes a plurality of inlet guide vane assemblies l22a-c. Each inlet-guide assembly l22a-c is disposed within a respective compression stage l02a-c and upstream of the impeller l lOa-c and is configured to impart predetermined or desired fluid properties and/or fluid flow attributes to the process fluid flowing through the fluid pathway. Such fluid properties and/or fluid flow attributes may include flow pattern ( e.g ., swirl distribution), velocity, flow rate, pressure, temperature, and/or any suitable fluid property and fluid flow attribute to enable the compressor 100 to function as described herein. Each inlet guide vane assembly l22a-c may include one or more inlet guide vanes (one shown in each assembly, l24a-c) disposed in the fluid pathway upstream of the respective impeller l lOa-c and configured to impart the one or more fluid properties and/or fluid flow attributes to the process fluid flowing through the fluid pathway and into each impeller l lOa-c.

[0028] The inlet guide vanes l22a-c may also be configured to vary the one or more fluid properties and/or fluid flow attributes imparted to the process fluid flowing through the fluid pathway and into each impeller. For example, respective portions of the inlet guide vanes l22a-c may be moveable (e.g., adjustable) to vary the one or more fluid properties and/or fluid flow attributes (e.g, swirl, velocity, mass flowrate, etc) imparted to the process fluid flowing through the fluid pathway. In an exemplary embodiment, the inlet guide vanes l22a-c may be configured to move or adjust within the fluid pathway, as disclosed in U.S. Patent No. 8,632,302, the subject matter of which is incorporated by reference herein to the extent consistent with the present disclosure. The inlet guide vanes l22a-c may be airfoil shaped, streamline shaped, or otherwise shaped and configured to impart, at least partially, the one or more fluid properties on the process fluid flowing through the fluid pathway and into each impeller l lOa-c.

[0029] As disclosed above, each impeller cavity H4a-c may include a respective impeller l lOa-c disposed therein. Each impeller l lOa-c may have a hub l26a-c having an inner annular surface l28a-c defining a central opening l30a-c. Each impeller l lOa-c may further include a plurality of blades l32a-c, extending from the hub l26a-c to a tip l34a-c thereof. In an exemplary embodiment, illustrated in Figures 1A-1C, each impeller l lOa-c has an impeller shroud affixed to and rotating with the impeller. In other embodiments, the shroud is stationary or static, coupled to the casing 104. In which case, the impeller is referred to as an open or "unshrouded" impeller (not shown). The impellers 1 lOa-c rotate about a longitudinal axis 136 of the compressor 100 to increase the static pressure and/or the velocity of the process fluid flowing therethrough.

[0030] As illustrated in Figures 1A-1C, each compression stage l02a-c includes a respective electric motor l38a-c, at least partially integrated therein. Each motor l38a-c is configured to drive and rotate its corresponding impeller l lOa-c about the longitudinal axis 136 of the compressor 100, to increase the static pressure and/or the velocity of the process fluid flowing therethrough. In one or more embodiments, each electric motor l38a-c is a ring motor. An exemplary ring motor may be the Model TG71XX ring motor manufactured by ThinGap, LLC of Camarillo, CA. In other embodiments, the electric motor l38a-c is a brushless DC electric motor, or a permanent magnet DC electric motor, or a variable-speed AC motor (not shown).

[0031] Turning now to Figure 2 with continued reference to Figures 1A-1C, Figure 2 illustrates an exploded view of the electric motor 138a with the compressor 100 omitted for clarity purposes, according to one or more embodiments. Although not shown, the electric motors 138b and 138c may be illustrated similarly and include the same components as the electric motor 138a. Each electric motor l38a-c has a stator l40a-c and a rotor l42a-c disposed radially outward from the stator l40a-c in a nested relationship therewith.

[0032] As arranged, the electric motor l38a-c may be referred to as an“inside-out motor” or an“out-runner motor”. As illustrated in Figures 1A-1C, the rotor l42a-c is disposed in an annular groove l44a-c defined in the inner annular surface l28a-c of the impeller l lOa-c. The stator l40a-c is disposed within an annular groove l46a-c defined in an inner annular surface l48a-c of the stationary diaphragm H2a-c defining in part the impeller cavity 1 l4a-c.

[0033] The rotor l42a-c includes an annular rotor body l50a-c having an outer annular surface l52a-c and an inner annular surface l54a-c radially opposing the outer annular surface l52a-c. The outer annular surface l52a-c of the annular rotor body l50a-c is coupled to the inner annular surface l28a-c of the impeller l lOa-c. As shown most clearly in Figure 2, the rotor l50a-c further includes a plurality of permanent magnets 156 (a pair indicated) coupled to the annular rotor body l50a between the outer and inner annular surfaces l52a, l54a thereof. The plurality of permanent magnets 156 is arranged in pairs thereof, with the permanent magnets 156 of each pair being spaced equidistantly from each other circumferentially about the annular rotor body l50a and forming opposing poles.

[0034] In an embodiment, the plurality of permanent magnets 156 includes one pair of permanent magnets. In another embodiment, the plurality of permanent magnets 156 includes two pairs of permanent magnets 156. In another embodiment, the plurality of permanent magnets 156 includes three pairs of permanent magnets 156. In other embodiments, the plurality of permanent magnets 156 includes four pairs of permanent magnets 156, five pairs of permanent magnets 156, six pairs of permanent magnets 156, or more. As shown in Figure 2, the plurality of permanent magnets 156 includes 16 pairs of permanent magnets 156. The number of pairs of permanent magnets 156 may be dependent at least in part on the diameter of the rotor l42a-c.

[0035] Each stator l40a-c includes an annular stator body l60a-c having an outer annular surface l62a-c and an inner annular surface l64a-c radially opposing the outer annular surface l62a-c. The inner annular surface l64a-c of the annular stator body l60a-c is coupled to the inner annular surface l48a-c of the stationary diaphragm H2a-c as illustrated in Figures 1A-1C. The annular stator body l60a-c of Figure 2 is coreless. Alternatively, the annular stator body l60a-c may have an iron core (not shown) similar to a brushless DC motor.

[0036] In embodiments including an iron core, the annular stator body l60a-c may include a laminated annular plate (not shown) at an axial end of the annular stator body l60a-c. The laminated annular plate may have a plurality of slots through which a plurality of wires (not shown) may be wrapped in the form of coils to provide a plurality of windings (not shown) configured to form electromagnets having magnetic poles when energized with electrical energy. In embodiments in which the process fluid is or includes a corrosive gas, the windings may be encompassed in cans (not shown) to protect the wires from corrosion.

[0037] In embodiments including a coreless annular stator body l60a-c as shown in Figure 2, the annular stator body l60a-c may be or include one or more layers of composite material, and the stator l40a-c may include a plurality of coils 166 embedded in the composite material of the annular stator body l60a-c. When energized, the plurality of coils 166 may form electromagnets configured to conduct electrical energy to generate magnetic fields to drive the rotor l42a-c. Each coil 166 of the plurality of coils 166 may be arranged to form opposing poles, such that the electrical energy provided to a coil 166 may result in the coil 166 being an electromagnet when energized and opposing poles of the rotor l42a-c and stator l40a- c being attracted to one another, resulting in the rotor poles moving toward the stator poles.

[0038] Each electric motor l38a-c may further include a controller l68a-c electrically coupled to a power source (not shown) external of the compressor 100 and configured to selectively provide electrical energy to the plurality of coils 166 to vary the polarity of the respective electromagnet. Each electric motor l38a-c may also include one or more sensors 170 communicatively coupled to the controller l68a-c and configured to determine the position and/or rotational speed of the respective rotor l42a-c. The sensor(s) 170 may detect and transmit the axial and radial positions and/or rotational speed of the rotor l42a-c to the respective controller l68a-c. In one or more embodiments, the sensor(s) 170 may be Hall Effect sensors.

[0039] Each controller l68a-c may include one or more processors 172 configured to process the information received from the sensor(s) 170 and to open or close one or more switches (not shown) of the controller l68a-c to respectively provide electrical energy to or prevent electrical energy from reaching the respective coil 166 based at least in part on the information provided by the sensor(s) 170. In some embodiments, one or more of the controllers l68a-c are combined in a single controller that controls jointly one or more of the motors l38a-c. As arranged, each of the impellers l lOa-c may spin at the same speed, substantially similar speeds, or differing speeds via the respective electric motors l38a-c and controllers l68a-c to optimize the performance of the compressor 100.

[0040] As illustrated in Figures 1A-1C and 2, the controllers l68a-c may be coupled to the respective annular stator bodies l60a-c and thus may be disposed within the casing 104. In at least one embodiment, one or more of the controllers l68a-c may be disposed external of the casing 104. In one or more embodiments, each controller l68a-c may communicate with at least one other controller l68a-c directly through a wired or wireless connection, or indirectly through a main controller (not shown). The controllers l68a-c may communicate with at least one other controller l68a-c to optimize the aerodynamic performance of the compressor 100.

[0041] Each controller l68a-c may be electrically coupled to the power source, and in some embodiments the main controller, via a respective wire or electrical conduit l74a-c. In one or more embodiments, each electrical conduit l74a-c may be fed through a conduit pathway l76a-c defined in the stationary diaphragm H2a-c and extending radially to the respective inlet-guide vane assembly l22a-c. The electrical conduit l74a-c may be directed through an opening in the inlet-guide vane l24a-c and electrically coupled to the stator l40a-c. In other embodiments, the conduit pathway l76a-c may extend axially from a location external of the casing 104.

[0042] As driven by the electric motors l38a-c, the rotation of the respective impellers l lOa-c may draw the process fluid to and through the impellers l lOa-c and accelerate the process fluid to the respective tips l34a-c of the impellers l lOa-c, thereby increasing the static pressure and/or the velocity of the process fluid. The plurality of blades l32a-c may be configured to impart the static pressure (potential energy) and/or the velocity (kinetic energy) to the process fluid to raise the velocity of the process fluid.

[0043] The process fluid at the tips l34a-c of the impellers l lOa-c may be subsonic and have an absolute Mach number less than one. For example, the process fluid at the tip l34a of the impeller 1 lOa may have an absolute Mach number less than 1, less than 0.9, less than 0.8, less than 0.7, less than 0.6, less than 0.5, less than 0.4, less than 0.3, less than 0.2, or less than 0.1. Accordingly, in such embodiments, the compressor 100 discussed herein may be "subsonic," as the impellers 1 lOa-c may be configured to rotate about the longitudinal axis 136 at a speed sufficient to provide the process fluid at the tips l34a-c thereof with an absolute Mach number of less than one.

[0044] In one or more embodiments, the process fluid at the tip l34c of the impeller l lOc may be supersonic and have an absolute Mach number of one or greater. For example, the process fluid at the tip l34c of the impeller l lOc may have an absolute Mach number of at least 1, at least 1.1, at least 1.2, at least 1.3, at least 1.4, at least 1.5, at least 1.6, at least 1.7, at least 1.8, at least 1.9, at least 2.0, at least 2.1, at least 2.2, at least 2.3, at least 2.4, or at least 2.5.

[0045] Accordingly, in such embodiments, the compressor 100 discussed herein is said to be "supersonic," as the impeller l lOc may be configured to rotate about the longitudinal axis 136 at a speed sufficient to provide the process fluid at the tip l34c thereof with an absolute Mach number of one or greater or with a fluid velocity greater than the speed of sound. In a supersonic compressor or a stage thereof, the rotational or tip speed of the impeller 1 lOc may be about 500 meters per second (m/s) or greater.

[0046] For example, the tip speed of the impeller l lOc may be about 510 m/s, about 520 m/s, about 530 m/s, about 540 m/s, about 550 m/s, about 560 m/s, about 570 m/s, about 580 m/s, about 590 m/s, about 600 m/s, about 610 m/s, about 620 m/s, about 630 m/s, about 640 m/s, about 650 m/s, about 660 m/s, about 670 m/s, about 680 m/s, about 690 m/s, about 700 m/s, or greater.

[0047] Each compression stage l02a-c may further include a plurality of electromagnetic bearings, including electromagnets 180 and permanent magnets 184. The electromagnets 180 (one shown in each stage) are disposed in respective annular grooves 181 (one shown in each stage) defined in a radially extending face of the stationary diaphragm adjacent a toe l82a-c of the impeller l lOa-c. In another embodiment, the plurality of electromagnets 180 is disposed in an annular groove (not shown) defined in a radially extending face of the stationary diaphragm H2a-c adjacent the heel of the impeller l lOa-c. Each impeller l lOa-c includes a corresponding plurality of permanent magnets 184 (one shown in each impeller l lOa- c) disposed within the toe l82a-c or heel thereof. The plurality of electromagnets 180 may be electrically coupled to the power source and the respective controllers l68a-c. The controllers l68a-c may be configured to vary the polarity of the respective electromagnets 180 to selectively increase or decrease the axial distance of the impeller l lOa-c from the respective stationary diaphragm 1 l2a-c. The electromagnets 180 and permanent magnets 184 may be configured to at least partially support and/or counter thrust loads or forces generated by the respective impellers l lOa-c.

[0048] As illustrated in Figures 1A-1C, each compression stage l02a-c of the compressor 100 may include passages l86a-c for venting higher-pressure process fluid to a known balance piston (not shown). Known balance pistons are configured to balance an axial thrust generated by a respective impeller l lOa-c during one or more modes of operating the compressor 100. In at least one embodiment, each balance piston and the respective impeller l lOa-c may be separate components. For example, the balance piston and the respective impeller l lOa-c may be separate annular components coupled with one another. In another embodiment, the balance piston may be integral with the respective impeller l lOa-c, such that the balance piston and the respective impeller l lOa-c may be formed from a single piece. Incorporation of balance pistons in the compressor 100 is optional.

[0049] Each respective compression stage l02a-c preferably includes a labyrinth seal l87a-c, interposed between the impeller cavity H4a-c and the outer circumferential periphery of the impeller l lOa-c, and configured to reduce substantially or prevent process flow leakage from a higher-pressure impeller outlet, downstream of the impeller tips l34a-c, back to the region of the guide vane assemblies l22a-c. Each compression stage l02a-c also preferably includes a labyrinth seal l88a-c adjacent to a respective passage l86a-c and configured to reduce substantially or prevent process fluid from leaking from the higher-pressure region of the impeller l lOa-c back to the region of the guide vane assemblies l22a-c. Each respective seal l88a-c also acts to “catch” or support its respective impeller l lOa-c in the event the electrical current supply to the electromagnets 187 is lost, and the impeller falls out of the failed magnetic field(s) while rotating.

[0050] Optionally, a plurality of gas vent ports l89a-c may be located in the casing 104 and fluidly coupled to respective impeller cavities H4a-c. The gas vent ports l89a-c may be externally controlled by a valve or gas conditioning skid (not shown) to cool each of the coils 166 of one or more of the motors l38a-c, by allowing a dry gas to circulate through the impeller cavity H4a-c. In at least one embodiment, the gas vent ports l89a-c may also be used as gas injection ports. Gas may be selectively injected or vented through the gas vent ports l89a-c to both pressurize and maintain the desired pressure within the impeller cavities 1 l4a-c.

[0051] In an exemplary operation of the compressor 100, with continued reference to Figures 1A-1C and 2, the electric motors l38a-c may drive the compressor 100 from rest to the steady state mode of operation by accelerating or rotating the respective impellers l lOa-c at the same speed, substantially similar speeds, or different speeds. The impellers l lOa-c may rotate about the longitudinal axis 136. The acceleration and/or rotation of the impeller l lOa at a first speed may draw the process fluid into the compressor 100 via the inlet cavity 108. The inlet guide vanes l24a disposed in the inlet cavity 108 may induce one or more flow properties ( e.g ., swirl) to the process fluid flowing therethrough.

[0052] The rotation of the impeller 1 lOa may further draw the process fluid from the inlet cavity 108 to and through the rotating impeller l lOa, and urge the process fluid to the tip l34a of the impeller l lOa, thereby increasing the velocity (e.g., kinetic energy) thereof. The process fluid from the impeller l lOa may be discharged from the tip l34a thereof and directed to the diffuser 116a fluidly coupled therewith. The diffuser H6a may receive the process fluid from the impeller l lOa and convert the velocity ( e.g ., kinetic energy) of the process fluid from the impeller l lOa to potential energy (e.g., increased static pressure).

[0053] The diffuser 116a may direct the process fluid downstream to the return channel 118b, where the process fluid may be directed to the second compression stage l02b. The inlet guide vanes l24b upstream of the impeller l lOb may induce one or more flow properties (e.g, swirl) to the process fluid flowing therethrough. The acceleration and/or rotation of the impeller 11 Ob at a second speed may draw the process fluid to and through the rotating impeller 11 Ob, and urge the process fluid to the tip l34b of the impeller 1 lOb, thereby increasing the velocity (e.g, kinetic energy) thereof. The second speed of the impeller 1 lOb may be the same, substantially similar to, or different from the first speed of the impeller l lOa. The process fluid from the impeller l lOb may be discharged from the tip l34b thereof and directed to the diffuser 116b fluidly coupled therewith. The diffuser 116b may receive the process fluid from the impeller 11 Ob and convert the velocity (e.g, kinetic energy) of the process fluid from the impeller 11 Ob to potential energy (e.g, increased static pressure).

[0054] The diffuser 116b may direct the process fluid downstream to the return channel 118c, where the process fluid may be directed to the last compression stage l02c. The inlet guide vanes l24c upstream of the impeller l lOc may induce one or more flow properties (e.g, swirl) to the process fluid flowing therethrough. The acceleration and/or rotation of the impeller 1 lOc at a third speed may draw the process fluid to and through the rotating impeller l lOc, and urge the process fluid to the tip l34c of the impeller l lOc, thereby increasing the velocity (e.g, kinetic energy) thereof.

[0055] The third speed of the impeller 1 lOc may be the same, substantially similar to, or different from the first speed of the impeller l lOa and/or the second speed of the impeller 110b. The first speed, the second speed, and the third speed may be determined by the respective controllers l68a-c to optimize the aerodynamic performance of the compressor 100. The process fluid from the impeller 1 lOc may be discharged from the tip l34c thereof and directed to the diffuser 116c fluidly coupled therewith. The diffuser 116c may receive the process fluid from the impeller l lOc and convert the velocity ( e.g ., kinetic energy) of the process fluid from the impeller 1 lOc to potential energy (e.g., increased static pressure).

[0056] The diffuser H6c may direct the process fluid downstream to the volute 120 fluidly coupled therewith. The volute 120 may collect the process fluid and deliver the process fluid to one or more downstream pipes and/or process components (not shown). The volute 120 may also be configured to increase the static pressure of the process fluid flowing therethrough by converting the kinetic energy of the process fluid to increased static pressure.

[0057] Figures 3-5 show an alternate embodiment compressor 200, wherein each compressor stage 202a-e of the exemplary five-stage compressor incorporates a pair of respective, opposed, pancake-type, flat motors 238 that are integral with their corresponding compressor impeller 2l0a-e. For clarity in Figures. 4 and 5, the respective, opposed, pancake-type flat motors are designated as 238a and 238b. Other compressor stage embodiments incorporate a single pancake-type flat motor that is oriented on one of the axial sides of the compressor impeller. In some embodiments, the pancake-type flat motors have permanent magnet-type rotor magnets, while in other embodiments, the pancake-type flat motors have electromagnet-type rotor magnets. In some embodiments, each stage 202a-e is incorporated in a separate, modular compressor casing 204a-e, which is shown schematically by dashed lines. The casings 204a-e are joined by their axial ends to other axially aligned casings. Thus, the number of compressor stages is selectively varied by incorporating fewer or lesser casing 204a-e modules. Vertically joined casings 204a-e advantageously eliminate need for horizontal split lines in the compressor casing and a concomitant, potential cause of fluid leakage. In other embodiments, the compressor is a single- stage compressor, or one with fewer or greater than five stages. Gas flow pathways of the working process fluid are shown in dashed lines, from the axial inlet 206 to the inlet cavity, to the collector or volute 220. Gas flow and compression properties and characteristics of the working process fluid through inlet 206, guide vane assemblies 222, impeller cavities 214, impeller blades 232, diffusers 216, return channels 218 between compressor stages 202a-e and to the volute 220 are comparable to those of the subsonic or supersonic compressor 100 of Figures 1A-C, and 2. Thus, description of such structure and flow characteristics imparted by them on the working fluid within the flow path is not repeated. The primary structural difference between the compressor embodiment 100 and the embodiment 200 is incorporation of the pair flat or pancake-style motors 238 in each stage of the latter, as opposed to the ring-style motors l38a-c in the former.

[0058] Figure 4 is a fragmentary, partial cross-sectional view of an exemplary compressor stage 202, which highlights the structural relationship among the compressor casing 204, the impeller 210, and a pair of flat or pancake-type motors 238a-b. The general structure of the exemplary compressor stage 202 of Figure 4 is configurable for any one or more stages of a compressor, such as the stages 202a-e of the compressor 200 of Figure 3. A single-stage compressor embodiment optionally includes a modular type of compressor casing. In the embodiment of Figure 4, the compressor casing 204 incorporates a stationary diaphragm that defines the impeller cavity 214. The impeller cavity 214 circumscribes the impeller 210 and the opposed, pancake-type flat motors 238a and 238b that are disposed therein. Construction of the impeller 210 is analogous to that of a vented, automobile brake rotor. Specifically, referring to Figures 4 and 5, the impeller 210 has a hollow hub 226, defining an inner annular surface 228 and a central opening 230. The impeller 210 has a plurality of blades 232, extending generally radially, in two or three dimensions, from the hub 226 to a tip 234 thereof. The impeller 210 has a pair of axial sidewalls 229a-b flanking the blades 232, which in combination define a plurality of process-fluid flow passages between the hub 226 and the blade tips 234. The impeller 210 rotates about a longitudinal axis 236 of the compressor stage 202, to increase the static pressure and/or the velocity of the process fluid flowing therethrough.

[0059] As illustrated in Figures 4 and 5, the compression stage 202 includes a pair of opposing, flat or pancake-type electric motors 238a-b, at least partially integrated within the compressor casing 204 and the impeller 210 and circumscribed by the impeller cavity 214. The motors 238a-b drive and rotate the corresponding impeller 210 about the longitudinal axis 236 of the compressor stage 202, to increase the static pressure and/or the velocity of the process fluid flowing therethrough. In one or more embodiments, the flat or pancake-type electric motors 238a-b are respectively a brush or brushless DC electric motor, or a permanent magnet, DC electric motor, or a variable-speed AC motor.

[0060] Turning now to Figure 5 with continued reference to Figure 4, the former illustrates an exploded view of a DC, permanent magnet embodiment of the respective, opposed, pancake-type, flat electric motors 238a-b with the impeller 210, but with the other components of the compressor stage 200 omitted for clarity purposes, according to one or more embodiments. The electric motors 238a-b have respective, stators 240a-b coupled within the circumscribing impeller cavity 214 defined within the stationary diaphragm of the casing 204. The stators 240a-b are axially flanking and nested with the respective corresponding rotors 242a-b, and are disposed radially outwardly of the impeller 210 and the impeller hub 226. The rotors 242a-b are respectively coupled to the axial sidewalls 229a-b of the impeller 210, rotating therewith.

[0061] As arranged, the paired electric motors 238a-b referred to as“flat motors” or “pancake-type motors”, as compared to the annular-type, external drive motors that are commonly used to power compressors via an external shaft. The electric motors 238a-b are paired and powered, so that their respective, axially directed electro- motive fields are opposed and cancel each other. This eliminates the need to incorporate a balancing piston in the compressor section 202, because there are no axially directed resultant forces. Elimination of a balancing piston simplifies and conserves volumetric space within the compressor section; it also eliminates compressed fluid bleed losses.

[0062] Each of the respective rotors 242a-b includes an annular rotor body 250a-b having an outer axial surface 252a-b and an inner axial surface 254a-b radially opposing the outer axial surface 252a-b. The inner axial surfaces 254a-b of the annular rotor body 250a-b are coupled to the respective, corresponding axial sidewalls 229a-b of the impeller 210. Referring to Figure 5, the each rotor 242a-b further includes a plurality of permanent magnets 256, which are coupled to the annular rotor body 250a-b between the outer 252a-b and inner 254a-b axial surfaces, thereof. The plurality of permanent magnets 256 is arranged in pairs thereof (see, e.g., 256(+) and 256(-) on rotor 242b of Figure 5), with the permanent magnets of each pair being spaced equidistantly from each other circumferentially and radially about the annular rotor body 250b and forming opposing magnetic poles. In various embodiments, the plurality of permanent magnets 256 includes one pair of permanent magnets or multiple pairs of permanent magnets. The number of pairs of permanent magnets 256 may be dependent at least in part on the diameter of the rotor 242a-b.

[0063] Each stator 240a-b includes an annular stator body 260a-b having an outer axial surface 262a-b and an inner axial surface 264a-b radially opposing the outer axial surface 262a-b. The outer axial surface 262a-b of the annular stator body 260a- b faces and is coupled with the surface of the compressor casing 204 that forms the impeller cavity 214. Each of the annular stator bodies 260a-b has an iron core (not shown) and a laminated, axial end plate 263 a-b at the outer axial surface 262a-b thereof. The laminated annular plate 263 a-b may have a plurality of slots through which a plurality of wires are wrapped in the form of coils 266a-b, to provide a plurality of windings configured to form electromagnets having magnetic poles when energized with electrical energy through the exemplary terminals PN. In embodiments in which the process fluid is or includes a corrosive gas, the windings 266a-b may be encompassed in cans (not shown) to protect the wires from corrosion.

[0064] In embodiments including a coreless annular stator body 260a-b, the annular stator body 260a-b may be or include one or more layers of composite material (not shown), and the stator 240a-b may include a plurality of coils 266a-b embedded in the composite material of the annular stator body 260a-b. When energized, the plurality of coils 266a-b form electromagnets configured to conduct electrical energy to generate magnetic fields to drive the corresponding rotor 242a-b. Each coil of the plurality of coils 266a-b may be arranged to form opposing poles, such that the electrical energy provided to a coil 266 may result in the coil being an electromagnet when energized and opposing poles of the rotor 242a-b and its corresponding stator 240a-b being attracted to one another, resulting in the rotor poles moving toward the stator poles.

[0065] Each electric motor 238a-b further includes a dedicated or shared controller 268 electrically coupled to a power source 269 external of the compressor stage 202 and configured to selectively provide electrical energy to the plurality of coils 266 (e.g., via terminals PN) to vary the polarity of the respective electromagnet. Each electric motor 238a-b may also include one or more sensors 270 communicatively coupled to its corresponding dedicated or shared controller 268 and configured to determine the position and/or rotational speed of the rotors 242a-b. The sensor(s) 270 may detect and transmit the axial and radial positions and/or rotational speed of the unified rotors 242a-b to the respective controller 268. In one or more embodiments, the sensor(s) 270 are Hall Effect sensors. As noted with respect to the controller 168 of Figure 2, control functions for respective electric motors 238 are handled jointly or severally in any combination by one or more controllers 268 and their corresponding sensors 270. Each controller 268 may include one or more processors 272 configured to process the information received from the sensor(s) 270 and to open or close one or more switches (not shown) of the controller to respectively provide electrical energy from the power source 269 to or prevent electrical energy from reaching the respective coil 266 based at least in part on the information provided by the sensor(s) 270. As arranged, each of the impellers 2l0a-e may spin at the same speed, substantially similar speeds, or differing speeds via the respective electric motors 238a-b and controller(s) 268, to optimize the performance of the compressor section 202

[0066] Each controller 268 may be electrically coupled to the power source 269, via a respective wire or electrical conduit 274a-b. In one or more embodiments, each electrical conduit 274a-b may be fed through a conduit pathway defined in the casing 204. [0067] Referring to Figure 4, each compression stage 202 includes a plurality of known electromagnetic bearings 280, shown schematically, which generate a magnetic levitation field in opposition to the inner annular surface 228 of the hub 226. The electromagnetic bearings 280 are electrically coupled to a power source, such as the power source 269 and the controller 268 in known fashion. In some embodiments, the controller(s) 268 are configured to vary the polarity of the respective electromagnets in the electromagnetic bearings 280, to increase or decrease selectively radial distance of the impeller 210 from the respective casing 204. In some embodiments, the electromagnetic bearings 280 are configured to at least partially support and/or counter axially directed thrust loads or forces generated by the impeller 210, if they are not totally cancelled by the opposed pair of motors 238a-b.

[0068] As illustrated in Figure 4, each compression stage 202 may include cooling passages 286a-b and/or additional gas ports in communication with the cooling passages (not shown), for bleeding higher-pressure process fluid to the stators 240a-b, and/or the rotors 242a-b, and/or the electromagnetic bearings 280. The compression stage 202 preferably includes a labyrinth seal 287a-b, interposed between the impeller cavity 214 and the inner circumferential periphery 228 of the impeller hub 226, and configured to regulate process flow coolant bleed from the higher-pressure impeller 210 outlet, downstream of the blades 232, back to respective the stators 240a-b and rotors 242a-b of the paired motors 238a-b and to the electromagnetic bearings 280. Seals 287a-b also act to“catch” or support the impeller 210 and its associated rotor structure 242a-b, in the event the electrical current supply to the electromagnetic bearings 280 is lost, and the impeller/rotor falls out of the bearings’ magnetic fields while rotating.

[0069] Figure 6 illustrates a flowchart depicting a method 300 for operating a compressor, according to one or more embodiments disclosed. The method 300 may include fluidly coupling a process fluid source with an inlet of the compressor, as at 302. The compressor may have a longitudinal axis and a plurality of compression stages. [0070] Each compression stage may include a stationary diaphragm defining an impeller cavity and a diffuser fluidly coupled to the impeller cavity. Each compression stage may also include an impeller disposed within the impeller cavity and configured to rotate therein about the longitudinal axis independently of at least one other impeller of the compressor. Each compression stage may further include an electric motor configured to drive the impeller. The electric motor may include a rotor coupled to the impeller and including a plurality of permanent magnets, and a stator coupled to the stationary diaphragm and including a plurality of electromagnets configured to generate a magnetic field to rotate the rotor.

[0071] The method 300 may also include driving each impeller with a respective electric motor, as at 304. The method 300 may further include compressing the process fluid flowing through each of the compression stages to form a compressed process fluid, as at 306. The method 300 may also include discharging the compressed process fluid from the compressor, as at 308.

[0072] It should be appreciated that all numerical values and ranges disclosed herein are approximate valves and ranges, whether or not "about" is used in conjunction therewith. It should also be appreciated that the term "about", as used herein, in conjunction with a numeral refers to a value that is +/- 5% (inclusive) of that numeral, +/- 10% (inclusive) of that numeral, or +/- 15% (inclusive) of that numeral. It should further be appreciated that when a numerical range is disclosed herein, any numerical value falling within the range is also specifically disclosed.

[0073] While there is reference to an exemplary controller platforms l68a-c and 268, architecture, and implementation by software modules executed by the processors 172, 272, it is also to be understood that exemplary embodiments of the invention may be implemented in various forms of hardware, software, firmware, special purpose processors, or a combination thereof. Preferably, aspects of the invention embodiments are implemented in software as a program tangibly embodied on a program storage device. The program may be uploaded to, and executed by, a machine comprising any suitable architecture. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (CPU), a random access memory (RAM), and input/output (I/O) interface(s). The computer platform also includes an operating system and microinstruction code. The various processes and functions described herein may be either part of the microinstruction code or part of the program (or combination thereof) which is executed via the operating system. In addition, various other peripheral devices may be connected to the computer/controller platform.

[0074] It is to be understood that, because some of the constituent controller l68a-c, 268 and sensor 170, 270 system components and method steps depicted in the accompanying figures are preferably implemented in software, the actual connections between the system components (or the process steps) may differ depending upon the manner in which the exemplary embodiments are programmed. Specifically, any of the computer platforms or devices may be interconnected using any existing or later discovered networking technology and may also all be connected through a lager network system, such as a corporate network, metropolitan network or a global network, such as the Internet.

[0075] Although various embodiments that incorporate the invention have been shown and described in detail herein, others can readily devise many other varied embodiments that still incorporate the claimed invention. The invention is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. In addition, it is to be understood that the terminology used herein is for the purpose of description and should not be regarded as limiting. The use of“including,”“comprising,” or“having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted”, “connected”,“supported”, and“coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and“coupled” are not restricted to physical, mechanical, or electrical connections or couplings.