EP2633197A1

EP2633197A1 - Multiple motor drivers for a hermetically-sealed motor-compressor system

Info

Publication number: EP2633197A1
Application number: EP11836783.8A
Authority: EP
Inventors: Jose L. Gilarranz; Pascal Lardy
Original assignee: Dresser Rand Co
Current assignee: Dresser Rand Co
Priority date: 2010-10-27
Filing date: 2011-07-26
Publication date: 2013-09-04
Also published as: EP2633197A4; US20130294939A1; WO2012057885A1

Abstract

A fluid compression system is disclosed having a hermetically-sealed housing with at least two motors and a compressor arranged therein. The motors may be arranged either on both sides of the compressor or in a tandem configuration on one side of the compressor. The motors may be adapted to drive both the compressor and at least one blower device coupled to a free end of shaft that extends through the housing, the blower device being configured to circulate a cooling fluid throughout the housing and thereby cool the motors and any accompanying radial/axial bearings.

Description

MULTIPLE MOTOR DRIVERS FOR A HERMETICALLY-SEALED

MOTOR-COMPRESSOR SYSTEM

Cross-reference to Related Applications

[0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 61/407, 148, entitled "Multiple Motor Drivers for a Hermetically-Sealed Motor-Compressor System," and filed on October 27, 2010. The contents of the priority application are hereby incorporated by reference in their entirety.

Background

[0002] A motor is often combined with a compressor in a single housing to provide what is known as a motor-compressor device. Via a shared rotating shaft supported on each end by a rotor-bearing system, the motor drives the compressor in order to generate a flow of compressed process gas. When used to drive a compressor, such as a centrifugal compressor, the motor is required to rotate at sufficiently high speeds to facilitate efficient compression of the process gas.

[0003] The compression range of the motor-compressor, however, may be limited by the power capacity of the motor driver, which is typically a constant-torque machine. In fact, there are many industrial applications in the field where the compressor power requirements exceed the power capacity of the motor driver. In such instances, the process requirements are often served by multiple motor- compressor arrangements, which can significantly increase the cost, weight, and footprint of the application.

[0004] Accordingly, there is a need for an improved motor-compressor arrangement that can supplement the power deficiencies of a single motor driver with a reduced cost when compared to the multiple unit approach.

Summary

[0005] Embodiments of the disclosure may include a fluid compression system. The fluid compression system may include a hermetically-sealed housing having a multi-section shaft extending from a first end of the housing to a second end of the housing, a compressor arranged within the housing and including a driven section of the shaft, and a first motor being disposed within the housing axially- adjacent the compressor at the first end, the first motor including a first motor rotor section of the shaft. The fluid compression system may also include a second motor disposed within the housing axially- adjacent the compressor at the second end, the second motor including a second motor rotor section of the shaft, wherein the first and second motor rotor sections are coupled to the driven section at opposing ends such that the motors are configured to simultaneously drive the driven section of the shaft and thereby rotate the compressor.

[0006] Embodiments of the disclosure may further provide a method of compressing a fluid. The method may include disposing a first motor, a second motor, and a compressor within a hermetically- sealed housing, the housing having a shaft that extends from a first end of the housing to a second end of the housing, and wherein the first and second motors and the compressor are each coupled to the shaft. The method may further include rotating the shaft with the first motor to provide torque to the shaft and drive the compressor at a first power/torque level, and rotating the shaft with the second motor concurrently with the first motor to provide additional torque to the shaft and drive the compressor at a second power/torque level, wherein the second power/torque level is greater than the first power/torque level.

[0007] Embodiments of the disclosure may further provide a fluid compression system. The fluid compression system may include a hermetically-sealed housing having a shaft extending from a first end of the housing to a second end of the housing, a compressor arranged within the housing at the first end and including a driven section of the shaft, and a first motor disposed within the housing at the second end and axially-offset from the compressor, the first motor including a first motor rotor section of the shaft and being in fluid communication with at least one internal cooling passage. The fluid compression system may also include a second motor disposed within the housing interposing the compressor and the first motor, the second motor including a second motor rotor section of the shaft and in fluid communication with at least one internal cooling passage, wherein the first and second motors are configured to drive the driven section of the shaft in tandem and thereby rotate the compressor.

Brief Description of the Drawings

[0008] The present disclosure is best understood from the following detailed description when read with the accompanying Figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0009] Figure 1 illustrates an exemplary fluid compression system, according to one or more embodiments disclosed.

[0010] Figure 2 illustrates another exemplary fluid compression system, according to one or more embodiments disclosed.

[0011] Figure 3 illustrates a schematic flow chart of a method for compressing a working fluid, according to one or more embodiments disclosed.

Detailed Description

[0012] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure.

[0013] Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to." All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term "or" is intended to encompass both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B," unless otherwise expressly specified herein.

[0014] Figure 1 illustrates an exemplary fluid compression system 100 according to embodiments described herein. The system 100 includes at least two drivers, such as motors 102a and 102b, coupled to a compressor 104 and an integrated separator 106 via a rotatable shaft 108. In the illustrated embodiment, the motors 102a,b are arranged on opposing axial sides of the compressor 104 and configured to drive the compressor 104 and separator 106 combination. In other embodiments, the separator 106 may be omitted from the system 100 so that motors 102a,b only drive the compressor 104.

[0015] The motors 102a,b, the compressor 104, and the separator 106 are each positioned within a hermetically-sealed housing 1 10 having a first end 1 1 1 and a second end 1 13. The housing 1 10 provides both support and protection for the motors 102a, b, the compressor 104, and the separator 106 components, such that each component shares the same pressure-containing casing.

[0016] The shaft 108 extends substantially the whole length of the housing 1 10, from the first end 1 1 1 to the second end 1 13, and includes a first motor rotor section 1 12a, a second motor rotor section 1 12b, and a driven section 1 14 arranged between the first and second motor rotor sections 1 12a,b. As illustrated, the first motor rotor section 1 12a of the shaft 108 corresponds to the rotor of the first motor 102a, and the second motor rotor section 1 12b corresponds to the rotor of the second motor 102b. The driven section 1 14 of the shaft 108 includes both the compressor 104 and the integrated separator 106. Moreover, the driven section 1 14 may be connected to the first motor rotor section 1 12a via a first coupling 1 16a and the second motor rotor section 1 12b via a second coupling 1 16b, such that when the first and second rotor sections 1 12a, b rotate, they drive the driven section 1 14. The first and second couplings 1 16a,b may be any type of shaft 108 coupling known to those skilled in the art, and may include a flexible or a rigid coupling. The first and second couplings 1 16a,b may be disposed within corresponding first and second cavities 1 15a and 1 15b, respectively, defined within the housing 1 10.

[0017] In operation, the motors 102a,b work together to rotate the compressor 104 (and the separator 106, if used) providing more power and torque than could be achieved with the use of a single motor. Because the amount of power delivered by each motor 102a,b is inherently limited, the use of two motors in series allows an increase in the power capability and capacity of the overall fluid compression system 100 or motor/compressor arrangement, which allows an extension of the process capabilities that can be met by the compressor 1 14.

[0018] Each motor 102a,b may be a permanent magnet-type electric motor, having permanent magnets 1 17 on the rotor and having a stator 1 18, or an induction-type machine with a squirrel cage mounted on the rotor (1 17) and having a stator 1 18. As will be appreciated, other types of motors 102 may be used, such as, but not limited to, synchronous, brushed DC motors, etc.

[0019] The motor rotor sections 1 12a,b and driven section 1 14 of the shaft 108 are supported at or near each end, respectively, by one or more radial bearings 120. Each radial bearing 120 are directly or indirectly supported by the housing 1 10, and in turn provide rotational support to the motor rotor sections 1 12a,b and driven section 1 14. In one embodiment, the bearings 120 may be magnetic bearings, such as active or passive magnetic bearings. In other embodiments, however, othertypes of bearings 120 may be used. In addition, at least one axial thrust bearing 122 may be arranged on the shaft 108 between the compressor 104 and the first motor 102a. In other embodiments, the axial thrust bearing 122 may be arranged outboard from the first motor 102a, at or near the end of the shaft 108 adjacent the first end 1 1 1 of the housing 1 10. The axial thrust bearing 122 may be a magnetic bearing and be configured to at least partially bear axial thrusts generated by the compressor 104.

[0020] The compressor 104 may be a multi-stage centrifugal compressor with one or more, in this case three, compressor stages or impellers 124. As can be appreciated, however, any number of impellers 124 may be implemented or used without departing from the scope of the disclosure. The separator 106 separates and removes higher-density components from lower-density components contained within a process gas introduced into the system 100. Any higher-density components removed from the process gas are discharged from the separator 106 via a discharge line 126, thereby providing a relatively dry process gas to the succeeding compressor 104. Especially in subsea applications where the process gas is commonly multiphase, any separated liquids discharged via line 126 may accumulate in a collection vessel (not shown) and be subsequently pumped back into the process gas at a downstream pipeline location (not shown). Otherwise, separated liquids may be drained into said collection vessel and disposed of properly, as known in the art.

[0021] A balance piston 125, including an accompanying balance piston seal 127, may be arranged on the shaft 108 between the compressor and the second motor 102b. Due to the pressure rise developed through the compressor 104, a pressure difference is created such that the compressor 104 has a net axial thrust in the direction of its inlet. The balance piston 125 serves to counteract that force, and any compressor 104 thrust not absorbed by the balance piston 125 may be otherwise absorbed by the thrust bearing(s) 122.

[0022] Still referring to Figure 1 , the system 100 further includes a closed-loop cooling system configured to regulate the temperature of the motors 102a, b and bearings 120, 122 during operation of the system 100. In one embodiment, the closed-loop cooling system includes a first blower device 128a disposed at or near a free end 134a of the first motor rotor section 1 12a, located outboard from the first motor 102a, and a second blower device 128b disposed at or near a free end 134b of the second motor rotor section 1 12b, located outboard from the second motor 102b. Each blower device 128a,b includes an impeller, such as a first impeller 130a and a second impeller 130b, respectively, disposed within the housing 1 10 and configured to generate head pressure required to circulate cooling fluid through the closed-loop cooling circuit described below. In at least one embodiment, each impeller 130a, b may be a centrifugal compression impeller and may be mounted on or otherwise attached to the respective free ends 134a,b of the motor rotor sections 1 12a,b of the shaft 108. Consequently, rotation of the shaft 108 will also drive each impeller 130a,b and thereby draw cooling fluid into each blower device 128a,b to be compressed and circulated throughout the closed-loop cooling circuit.

[0023] In one or more embodiments, the closed-loop cooling system may include only the first blower device 128a or otherwise include only the second blower device 128b, without departing from the scope of the disclosure. In other embodiments, the closed-loop cooling system may include a single blower device (not shown) coupled to the exterior of either the first end 1 1 1 or the second end 1 13 of the housing 1 10. In said embodiment, the impeller of the single blower device may be mounted on or otherwise attached to the free end 134a or 134b of the shaft 108 as it extends through the first end 1 1 1 or second end 1 13, respectively. Such an embodiment is discussed in detail in co-pending U.S. Pat. App. No. 61/407,059 (Atty. Dock. # 42495.600) entitled "Method and System for Cooling a Motor- Compressor with a Closed-Loop Cooling Circuit," and filed on October 27, 2010, the contents of which are hereby incorporated by reference to the extent consistent with the present disclosure. [0024] In operation, a process gas to be compressed or otherwise treated is introduced into the system 100 via an inlet 142. The process gas may include, but is not limited to, a hydrocarbon gas, such as a mixture of natural gas or methane derived from a production field or via a pressurized pipeline. In other embodiments, the process gas may include air, C0₂, N₂, ethane, propane, i-C₄, n-C₄, i-C₅, n-C₅, and/or combinations thereof.

[0025] In at least one embodiment, especially in subsea oil and gas applications, the process gas may be a "wet" process gas having both liquid and gaseous components, or otherwise including a mixture of higher-density and lower-density components. Accordingly, the separator 106 receives the process gas via the inlet 142 and removes portions of high-density components therefrom, thereby generating a substantially dry process gas. The liquid and/or higher-density components extracted from the process gas by the separator 106 are removed via the discharge line 126, as described above. The compressor 104 receives the substantially dry process gas from the separator 106 and compresses the dry gas through the successive stages of impellers 124 to thereby produce a compressed process gas that is ejected from the compressor 104 via a process discharge 144.

[0026] To contain the process gas within the housing 1 10 and prevent "dirty" process gas from leaking into the adjacent bearing assemblies 120, 122, the closed-loop cooling circuit, and motors 102a, b, the system 100 includes one or more buffer seals 146. The buffer seals 146 may be radial seals arranged at or near each end of the driven section 1 14 of the shaft 108 and inboard of the bearings 120.

[0027] In one or more embodiments, the buffer seals 146 may be brush seals or labyrinth seals. In other embodiments, the buffer seals 146 may be dry gas seals or carbon ring seals configured to receive a feed of pressurized seal gas via lines 148. When compared to conventional labyrinth or brush seals, the use of carbon rings buffer seals 146 may significantly reduce the amount of seal gas that is consumed, thereby increasing compressor performance efficiency. Moreover, carbon ring seals are less expensive and less susceptible to damage than conventional dry gas seal assemblies, especially when processing wet process gases. Appropriate implementation of carbon ring seals as buffer seals 146 in the system 100 is also described in co-pending U.S. Pat. App. No. 61/407,059 (42495.600), indicated above as being incorporated by reference.

[0028] The seal gas in lines 148 is a pressurized process gas that may be derived from the discharge 144 of the compressor 104 and filtered for injection into the buffer seals 146. In other embodiments, however, especially in applications having dry gas seals as buffer seals 146, the seal gas in lines 148 may be a source of clean hydrocarbon gas, hydrogen, or inert gases such as helium, nitrogen, or C0₂. During operation of the system 100, the seal gas creates a pressure differential designed to prevent process gas leakage across the buffer seals 146 and into locations of the housing 1 10 where the bearings 120, 122 and the motors 102a,b are located. [0029] In order to cool or otherwise regulate the temperature of the motors 102a,b and the bearings 120, 122 during operation, cooling fluid is circulated throughout the housing 1 10 in a cooling loop, or closed-loop cooling circuit, powered by at least one of the blower devices 128a, b. The blower devices 128a, b immerse the motors 102a, b and accompanying bearings 120, 122 in an atmosphere of pressurized cooling fluid. In one or more embodiments, the cooling fluid may be the same as the seal gas in lines 148. In other embodiments, the cooling fluid, seal gas, and process gas may all be the same fluid, which may prove advantageous in maintaining and designing any auxiliary systems.

[0030] Since each impeller 130a,b may be directly coupled to a corresponding rotor section 1 12a,b, each impeller 130a, b operates as long as at least one motor 102a, b is in operation and driving the shaft 108. As each impeller 130a, b rotates, it draws in cooling fluid, compresses it, and ultimately ejects the cooling fluid via respective outlets 140a or 140b and into lines 154a or 154b, respectively. Valves 153a and 153b may be communicably coupled to lines 154a, b, respectively, to regulate or otherwise control the head pressure of the cooling fluid as the system 100 reaches its normal operating speed. In other embodiments, one or both of the valves 153a,b may be entirely omitted from the system 100 and the cooling fluid may instead be circulated at a pressure proportional to the rotational speed of the shaft 108 and the existing flow resistance within the cooling loop.

[0031] In at least one embodiment, the cooling fluid in lines 154a,b may be directed through respective heat exchangers 156a and 156b adapted to reduce the temperature of the cooling fluid, and also directed to respective gas conditioning skids 157a and 157b configured to filter the cooling fluid. In one embodiment, the heat exchangers 156a, b are a single heat exchanger fluidly coupled to both lines 154a, b, and the gas conditioning skids 157a, b are a single gas conditioning skid also fluidly coupled to both lines 154a,b. In one embodiment, the gas conditioning skids 157a,b and/or the heat exchangers 156a,b may include a density-based separator (not shown), or the like, configured to remove any condensation generated by reducing the temperature of the cooling fluid.

[0032] Other embodiments contemplated herein include placing the heat exchangers 156a,b and accompanying gas conditioning skids 157a,b prior to the blower devices 128a, b. As can be appreciated, cooling and conditioning the cooling fluid priorto entering the blower devices 128a, b may prove advantageous, since a lower-temperature working fluid will demand less power from the motors 102a,b to compress and circulate the cooling fluid.

[0033] At least one external gas conditioning skid 159 may also be included in the system 100 and configured to provide the seal gas for the buffer seals 146 via lines 148 during system 100 start-up and during normal operation. During start-up there may exist a pressure differential between the area surrounding the compressor 104 and the area surrounding each motor 102a, b. The seal gas entering the buffer seals 146 may leak into the area surrounding the motors 102a,b until reaching the desired suction pressure of the compressor 104. The external conditioning skid 159 may also provide initial fill gas via line 164 to provide pressurized cooling fluid for the system 100 until an adequately pressurized source of process gas/cooling fluid may be obtained from the discharge 144 of the compressor 104. Accordingly, the initial fill gas may be cooling fluid or process gas added to the system 100. During normal operation, fill gas from line 164 may also be used in the event there is a sudden change in pressure in the system 100 and pressure equilibrium between the compressor 104 and the motor 102 must be located in order to stabilize the cooling loop.

[0034] The cooled and filtered cooling fluid is discharged from the first gas conditioning skid 157a and into line 158a. Line 158a is subsequently separated into lines 160 and 162 before injecting the cooling fluid into internal cooling passages 150a and 150b, respectively, defined within the housing 1 10 and configured to cool the first motor 102a and bearings 120 that support the first motor rotor section 1 12a. As the cooling fluid circulates around the first motor 102a and passes through the adjacent bearings 120 (i.e., through a gap formed between each bearing 120 and the shaft 108), heat is drawn awayfrom the first motor 102a and each adjacent bearing 120. The cooling fluid returns or otherwise loops back to the first impeller 130a either by passing through the bearings 120 outboard from the first motor 102a, or by passing through the bearings 120 inboard of the first motor 102a and into the first cavity 1 15a where it circulates through a first return line 166a fluidly coupled to the first impeller 130a.

[0035] On the other side of the system 100, cooled and filtered cooling fluid is discharged from the second gas conditioning skid 157b and into line 158b. Line 158b is subsequently separated into lines 168 and 170, where line 168 is split and introduced into internal cooling passages 152a and 152b defined within the housing 1 10 to cool the bearings 120, 122 that support the driven section 1 14 of the shaft 108. As the cooling fluid nears the bearings 120, the buffer seals 146 generally prevent the cooling fluid from passing into the separator 106 and/or compressor 104. Instead, the cooling fluid freely passes through the bearings 120 toward the ends of the driven section 1 14, simultaneously drawing heat away from the bearings 120. As can be appreciated, there may be embodiments where at least a small portion of the seal gas in lines 148 provided to the buffer seals 146 may be combined with the cooling fluid at each end of the driven section 1 14 of the shaft 108.

[0036] The cooling fluid coursing through the internal cooling passage 152a may also be configured to cool the axial thrust bearing 122 as it channels toward the first coupling 1 16a and is ultimately discharged into the first cavity 1 15a. The cooling fluid coursing through internal cooling passage 152b may cool the bearings 120 adjacent the second coupling 1 16b and in due course escape into the second cavity 1 15b.

[0037] The cooling fluid in line 170 may be split or otherwise introduced into internal cooling passages 152c and 152d defined within the housing 1 10 to cool the second motor 102b and adjacent bearings 120 that provide support to the second motor rotor section 1 12b. As the cooling fluid circulates around the second motor 102b and passes through the adjacent bearings 120 on each side, heat is drawn away to cool the first motor 102b and each adjacent bearings 120. The cooling fluid returns or otherwise loops back to the second impeller 130b either by passing through the bearings 120 outboard from the second motor 102b, or by passing through the bearings 120 inboard of the second motor 102b and into the second cavity 1 15b where it circulates through a second return line 166b fluidly coupled to the second impeller 130b.

[0038] The system 100 may further include a first pressure balance line 172a fluidly coupled to both the first return line 166a and the first end 1 1 1 of the housing 1 10, and a second pressure balance line 172b fluidly coupled to both the second return line 166b and the second end 1 13 of the housing 1 10. The pressure balance lines 172a,b counteract or otherwise equalize axial forces generated by the respective impellers 130a,b. A third pressure balance line 172c may fluidly connect the first and second cavities 1 15a,b so as to maintain a substantially constant cooling fluid pressure between the first impeller 130a and the second impeller 130b. It should be noted here again that, although not shown, the cooling loops for both motors 102a,b may be combined into a single cooling loop system that uses only one cooler and one gas conditioning skid or system.

[0039] The embodiments described herein are advantageous for a variety of reasons. For example, since the system 100 employs two motors 102a, b within the same hermetically-sealed housing 100, the power and torque capability of the system 100 is dramatically increased. Furthermore, the system 100 may prove advantageous in motor-compressor applications having a laminated shaft 108, as opposed to a solid shaft 108 design. Laminated shafts for high-speed motors are generally not designed to work in a drive-through configuration which would require one motor to deliver increased amounts of torque to a single end of the compressor 104, and would probably otherwise fail under such an increase in power. Instead, the system 100 as described delivers torque to the compressor 104 from both ends of the compressor 104 via the first and second motors 102a,b, thereby dividing the torque input to separated portions of the shaft 108.

[0040] Referring now to Figure 2, depicted is another exemplary fluid compression system 200, similar in some respects to the fluid compression system 100 described above in Figure 1 . Accordingly, the system 200 may be best understood with reference to Figure 1 , where like numerals correspond to like components that will not be described again in detail. Similar to the system 100 of Figure 1 , the system 200 may include at least two prime movers, such as motors 102a and 102b, coupled to the compressor 104 and the separator 106 via the rotatable shaft 108. The motors 102a,b, the compressor 104, and the separator 106 are each positioned within the hermetically-sealed housing 1 10 having a first end 1 1 1 and a second end 1 13.

[0041] The motors 102a,b in system 200 are arranged in tandem and power the compressor 104 and separator 106 from a single side of the compressor 104. The first motor 102a and its accompanying bearings 120 and blower device 128a are arranged on the outboard side of the second motor 102b. The shaft 108 may again include first and second motor rotor sections 1 12a,b and a driven section 1 14. However, it is only the second motor rotor section 1 12b that is coupled to the driven section 1 14 of the shaft 108 via the second coupling 1 16b, whereas the first motor rotor section 1 12a is coupled to the opposing end of the second motor rotor section 1 12b via the first coupling 1 16a. As will be appreciated, the tandem arrangement of the motors 102a,b may be disposed on either side of the compressor 104 without departing from the scope of the disclosure.

[0042] The closed-loop cooling system of Figure 2 may be substantially similar to the closed-loop cooling system of Figure 1. For example, cooling fluid in lines 160 and 162 is injected into internal cooling passages 150a and 150b, respectively to cool the first motor 102a and the bearings 120 that support the first motor rotor section 1 12a of the shaft 108. Moreover, the cooling fluid in line 170 is split and injected into internal cooling passages 152c,d to cool the second motor 102b and the bearings 120 that support the second motor rotor section 1 12b of the shaft 108. It will be further appreciated that the closed-loop cooling system of Figure 2 may omit either the first or the second blower device 128a,b without departing from the scope of the disclosure. In other embodiments, the closed-loop cooling system may include a single blower device (not shown) coupled to the exterior of the second end 1 13 of the housing 1 10, such as is disclosed in co-pending U.S. Pat. App. No. 61/407,059 (Atty. Dock # 42495.600), indicated above as being incorporated by reference.

[0043] The cooling fluid in line 168 is split and introduced into the internal cooling passages 152a, b to cool the bearings 120 that support the driven section 1 14 of the shaft 108. The cooling fluid in the internal cooling passage 152a may also cool the axial thrust bearing 122 as it channels toward the compressor end 1 1 1 of the housing 1 10 and is ultimately discharged via line 174. The cooling fluid in the internal cooling passage 152b may escape into the second cavity 1 15b. In one embodiment, the second cavity 1 15b may also receive cooling fluid via line 174. Accordingly, the cooling fluid channeled through the internal cooling passages 152a,b is combined or otherwise mixed within the second cavity 1 15b.

[0044] Cooling fluid collected in the first and second cavities 1 15a,b is discharged into a return line 176 fluidly coupled to each cavity 1 15a,b. The return line 176 recycles a portion of the cooling fluid back to each impeller 130a, b to thereby start the closed-loop cooling circuit over again. A balance line 178 may be fluidly coupled to the return line 176 and the motor end 1 13 of the housing 1 10 and to counteract or otherwise equalize axial forces generated by the impellers 130a,b.

[0045] Several variations of the system 200 may be undertaken without departing from the scope of the disclosure. For example, as described above, the first and second heat exchangers 156a, b may be a single heat exchanger, and the first and second gas conditioning skids 157a,b may be a single gas conditioning skid. Also, the first or the second heat exchanger 156a,b may be disposed before the blower devices 128a,b so as to decrease the temperature of the recycled cooling fluid before recompression in each impeller 130a,b. Furthermore, the separator 106 may be omitted from the system 200 so that the motors 102a,b only drive the compressor 104.

[0046] Referring now to Figure 3, illustrated is a flowchart depicting an exemplary method 300 of compressing a fluid. The method 300 may include arranging first and second motors and a compressor within a hermetically-sealed housing or casing, as at 302. The housing may have a shaft that extends from a first end to a second end of the housing. Each of the first and second motors and the compressor may be coupled to the shaft such that rotation of at least one of the motors necessarily drives the compressor and compresses the fluid. In one embodiment, the first and second motors are arranged within the housing on opposing sides of the compressor. In another embodiment, the first and second motors are arranged in tandem and axially-spaced from the compressor along the shaft. In at least one embodiment, a separator is also disposed within the housing, axially-spaced from the compressor.

[0047] The method 300 may also include rotating the shaft with the first motor to drive the compressor at a first power/torque level, as at 304. In an embodiment, the first power/torque level is proportional to the power capability and/or maximum torque that can be provided by the first motor when taking into account the mass of the compressor (and potentially the separator if employed), the work of compression, and any other frictional drag forces that must be overcome to rotate the shaft. The method 300 may further include rotating the shaft with the second motor to drive the compressor at a second or higher power/torque level, as at 306, wherein the second power/torque level is greater than the first power/torque level and greater than a power/torque level that could be achieved by a single motor. As can be appreciated, the addition of the second motor may provide supplementary torque to the shaft to complement the power capability of the first motor. Consequently, the compressor can handle more demanding power conditions than what the first motor alone could supply, thereby increasing the overall compression power of the motor-compressor system.

[0048] The method 300 may further include supporting the shaft within the housing with a plurality of radial bearings, as at 308. As the shaft rotates, a first impeller coupled to a first free end of the shaft rotates and circulates a cooling fluid throughout the housing to cool the first and second motors and the bearings, as at 310. In one or more embodiments, the housing may define a plurality of internal cooling passages that are in fluid communication with the plurality of radial bearings and the first and second motors. As the cooling fluid circulates through the internal cooling passages, heat is drawn away from the motors and bearings, thereby cooling or otherwise regulating the temperature of said components. The cooling fluid is then returned to the first impeller, as at 312, thereby completing a closed-loop cooling circuit. Accordingly, after cooling the internal components, the cooling fluid is recycled back to the impeller to be recompressed and recirculated back through the housing. In embodiments including an axial thrust bearing also disposed about the shaft, the cooling fluid may be configured to remove heat therefrom also.

[0049] The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

Claims We claim:

1. A fluid compression system, comprising:

a hermetically-sealed housing having a multi-section shaft extending from a first end of the housing to a second end of the housing;

a compressor arranged within the housing and including a driven section of the shaft;

a first motor being disposed within the housing axially-adjacent the compressor at the first end, the first motor including a first motor rotor section of the shaft; and

a second motor disposed within the housing axially-adjacent the compressor at the second end, the second motor including a second motor rotor section of the shaft, wherein the first and second motor rotor sections are coupled to the driven section at opposing ends such that the motors are configured to simultaneously drive the driven section of the shaft and thereby rotate the compressor.

2. The fluid compression system of claim 1 , further comprising:

radial bearings disposed proximal each end of the first and second motor rotor sections and each end of the driven section, the radial bearings being in fluid communication with at least one internal cooling passage defined within the housing; and

a first impeller coupled to a free end of the second motor rotor section of the shaft, whereby rotation of the second motor rotor section drives the first impeller and circulates a cooling fluid in a closed cooling loop through internal cooling passages defined within the housing.

3. The fluid compression system of claim 2, further comprising a second impeller coupled to a free end of the first motor rotor section of the shaft, whereby rotation of the first motor rotor section drives the second impeller and circulates the cooling fluid in the closed cooling loop through the internal cooling passages.

4. The fluid compression system of claim 2, wherein the radial bearings are magnetic bearings.

5. The fluid compression system of claim 1 , further comprising a separator axially-spaced from the compressor and disposed within the housing, the separator being coupled to the driven section of the shaft.

6. The fluid compression system of claim 1 , wherein the first motor rotor section and the driven section are connected via a first coupling.

7. The fluid compression system of claim 6, wherein the second motor rotor section and the driven section are connected via a second coupling.

8. The fluid compression system of claim 1 , wherein the compressor is a multi-stage centrifugal compressor.

9. A method of compressing a fluid, comprising:

disposing a first motor, a second motor, and a compressor within a hermetically-sealed housing, the housing having a shaft that extends from a first end of the housing to a second end of the housing, and wherein the first and second motors and the compressor are each coupled to the shaft;

rotating the shaft with the first motor to provide torque to the shaft and drive the compressor at a first power/torque level; and

rotating the shaft with the second motor concurrently with the first motor to provide additional torque to the shaft and drive the compressor at a second power/torque level, wherein the second power/torque level is greater than the first power/torque level.

10. The method of claim 9, further comprising:

supporting the shaft within the housing with a plurality of radial bearings, the housing defining a plurality of internal cooling passages in fluid communication with the plurality of radial bearings and the first and second motors;

driving a first impeller coupled to a first free end of the shaft;

circulating a cooling fluid through at least one of the internal cooling passages of the housing with the first impeller;

cooling the first and second motors and the plurality radial bearings with the cooling fluid; and

returning the cooling fluid to the impeller in a closed-loop circuit.

1 1 . The method of claim 10, further comprising:

driving a second impeller coupled to a second free end of the shaft;

circulating the cooling fluid through at least one of the internal cooling passages of the housing with the second impeller;

returning the cooling fluid to the second impeller in the closed-loop circuit.

12. The method of claim 1 1 , further comprising directing the cooling fluid through a heat exchanger to reduce the temperature of the cooling fluid.

13. The method of claim 12, further comprising filtering the cooling fluid with a gas conditioning skid.

14. The method of claim 10, further comprising cooling an axial thrust bearing with the cooling fluid, the axial thrust bearing being disposed on the shaft between the compressor and the first motor.

15. The method of claim 10, further comprising separating high-density components from low- density components in the fluid with an integrated separator arranged within the housing and axially-spaced from the compressor, the integrated separator being coupled to the shaft such that rotation of the shaft drives the integrated separator.

16. A fluid compression system, comprising:

a hermetically-sealed housing having a shaft extending from a first end of the housing to a second end of the housing;

a compressor arranged within the housing at the first end and including a driven section of the shaft;

a first motor disposed within the housing at the second end and axially-offset from the compressor, the first motor including a first motor rotor section of the shaft and being in fluid communication with at least one internal cooling passage; and

a second motor disposed within the housing interposing the compressor and the first motor, the second motor including a second motor rotor section of the shaft and being in fluid

communication with at least one internal cooling passage, wherein the first and second motors are configured to drive the driven section of the shaft in tandem and thereby rotate the compressor.

17. The fluid compression system of claim 16, further comprising:

a first coupling connecting the first motor rotor section to the second motor rotor section; and

a second coupling connecting the second motor rotor section to the driven section.

18. The fluid compression system of claim 17, further comprising:

radial bearings disposed proximal each end of the first and second motor rotor sections and each end of the driven section, the radial bearings being in fluid communication with at least one internal cooling passage; and a first impeller coupled to a free end of the first motor rotor section of the shaft, whereby rotation of the first motor rotor section drives the first impeller and circulates a cooling fluid in a closed cooling loop through the internal cooling passages.

19. The fluid compression system of claim 18, further comprising a second impeller coupled to the second motor rotor section of the shaft and disposed between the first and second motors, whereby rotation of the second motor rotor section drives the second impeller and circulates the cooling fluid in the closed cooling loop through the internal cooling passages.

20. The fluid compression system of claim 16, further comprising a separator axially-spaced from the compressor and disposed within the housing, the separator being coupled to the driven section of the shaft.

21. The fluid compression system or method of any of the preceding claims, further comprising: radial bearings disposed proximal each end of the first and second motor rotor sections and each end of the driven section, the radial bearings being in fluid communication with at least one internal cooling passage defined within the housing; and

22. The fluid compression system or method of any of the preceding claims, further comprising further comprising a second impeller coupled to a free end of the first motor rotor section of the shaft, whereby rotation of the first motor rotor section drives the second impeller and circulates the cooling fluid in the closed cooling loop through the internal cooling passages.

23. The fluid compression system or method of any of the preceding claims, wherein the radial bearings are magnetic bearings.

24. The fluid compression system or method of any of the preceding claims, further comprising a separator axially-spaced from the compressor and disposed within the housing, the separator being coupled to the driven section of the shaft.

25. The fluid compression system or method of any of the preceding claims, wherein the first motor rotor section and the driven section are connected via a first coupling.

26. The fluid compression system or method of any of the preceding claims, wherein the second motor rotor section and the driven section are connected via a second coupling.

27. The fluid compression system or method of any of the preceding claims, wherein the compressor is a multi-stage centrifugal compressor.

28. The fluid compression system or method of any of the preceding claims, further comprising: supporting the shaft within the housing with a plurality of radial bearings, the housing defining a plurality of internal cooling passages in fluid communication with the plurality of radial bearings and the first and second motors;

driving a first impeller coupled to a first free end of the shaft;

returning the cooling fluid to the impeller in a closed-loop circuit.

29. The fluid compression system or method of any of the preceding claims, further comprising: driving a second impeller coupled to a second free end of the shaft;

returning the cooling fluid to the second impeller in the closed-loop circuit.

30. The fluid compression system or method of any of the preceding claims, further comprising directing the cooling fluid through a heat exchanger to reduce the temperature of the cooling fluid.

31 . The method of claim 12, further comprising filtering the cooling fluid with a gas conditioning skid.

32. The fluid compression system or method of any of the preceding claims, further comprising cooling an axial thrust bearing with the cooling fluid, the axial thrust bearing being disposed on the shaft between the compressor and the first motor.

33. The fluid compression system or method of any of the preceding claims, further comprising separating high-density components from low-density components in the fluid with an integrated separator arranged within the housing and axially-spaced from the compressor, the integrated separator being coupled to the shaft such that rotation of the shaft drives the integrated separator.

34. The fluid compression system or method of any of the preceding claims, further comprising: a first coupling connecting the first motor rotor section to the second motor rotor section; and

35. The fluid compression system or method of any of the preceding claims, further comprising: radial bearings disposed proximal each end of the first and second motor rotor sections and each end of the driven section, the radial bearings being in fluid communication with at least one internal cooling passage; and

a first impeller coupled to a free end of the first motor rotor section of the shaft, whereby rotation of the first motor rotor section drives the first impeller and circulates a cooling fluid in a closed cooling loop through the internal cooling passages.

36. The fluid compression system or method of any of the preceding claims, further comprising a second impeller coupled to the second motor rotor section of the shaft and disposed between the first and second motors, whereby rotation of the second motor rotor section drives the second impeller and circulates the cooling fluid in the closed cooling loop through the internal cooling passages.

37. The fluid compression system or method of any of the preceding claims, further comprising a separator axially-spaced from the compressor and disposed within the housing, the separator being coupled to the driven section of the shaft.