U.S. patent application number 13/880884 was filed with the patent office on 2013-11-07 for multiple motor drivers for a hermetically-sealed motor-compressor system.
This patent application is currently assigned to DRESSER-RAND COMPANY. The applicant listed for this patent is Jose L. Gilarranz, Pascal Lardy. Invention is credited to Jose L. Gilarranz, Pascal Lardy.
Application Number | 20130294939 13/880884 |
Document ID | / |
Family ID | 45994288 |
Filed Date | 2013-11-07 |
United States Patent
Application |
20130294939 |
Kind Code |
A1 |
Gilarranz; Jose L. ; et
al. |
November 7, 2013 |
MULTIPLE MOTOR DRIVERS FOR A HERMETICALLY-SEALED MOTOR-COMPRESSOR
SYSTEM
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.
Inventors: |
Gilarranz; Jose L.; (Katy,
TX) ; Lardy; Pascal; (Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gilarranz; Jose L.
Lardy; Pascal |
Katy
Houston |
TX
TX |
US
US |
|
|
Assignee: |
DRESSER-RAND COMPANY
Olean
NY
|
Family ID: |
45994288 |
Appl. No.: |
13/880884 |
Filed: |
July 26, 2011 |
PCT Filed: |
July 26, 2011 |
PCT NO: |
PCT/US11/45270 |
371 Date: |
July 23, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61407148 |
Oct 27, 2010 |
|
|
|
Current U.S.
Class: |
417/53 ;
417/338 |
Current CPC
Class: |
H02K 7/14 20130101; F04D
25/0606 20130101; H02K 16/00 20130101; F04D 29/058 20130101; F04D
29/5806 20130101; F04D 25/0686 20130101; F04D 17/12 20130101; F04D
25/16 20130101; F04D 25/08 20130101 |
Class at
Publication: |
417/53 ;
417/338 |
International
Class: |
F04D 25/06 20060101
F04D025/06 |
Claims
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; 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; 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.
2. (canceled)
3. The fluid compression system of claim 1, 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 1, 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.
11. 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; cooling the first and
second motors and the plurality radial bearings with the cooling
fluid; and returning the cooling fluid to the second impeller in
the closed-loop circuit.
12. The method of claim 11, 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; 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; 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.
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. (canceled)
19. The fluid compression system of claim 16, 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.
21-30. (canceled)
31. The method of claim 12, further comprising filtering the
cooling fluid with a gas conditioning skid.
32-37. (canceled)
Description
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
Oct. 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] FIG. 1 illustrates an exemplary fluid compression system,
according to one or more embodiments disclosed.
[0010] FIG. 2 illustrates another exemplary fluid compression
system, according to one or more embodiments disclosed.
[0011] FIG. 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] FIG. 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 110 having
a first end 111 and a second end 113. The housing 110 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 110, from the first end 111 to the second end 113, and
includes a first motor rotor section 112a, a second motor rotor
section 112b, and a driven section 114 arranged between the first
and second motor rotor sections 112a,b. As illustrated, the first
motor rotor section 112a of the shaft 108 corresponds to the rotor
of the first motor 102a, and the second motor rotor section 112b
corresponds to the rotor of the second motor 102b. The driven
section 114 of the shaft 108 includes both the compressor 104 and
the integrated separator 106. Moreover, the driven section 114 may
be connected to the first motor rotor section 112a via a first
coupling 116a and the second motor rotor section 112b via a second
coupling 116b, such that when the first and second rotor sections
112a,b rotate, they drive the driven section 114. The first and
second couplings 116a,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 116a,b may be disposed
within corresponding first and second cavities 115a and 115b,
respectively, defined within the housing 110.
[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 114.
[0018] Each motor 102a,b may be a permanent magnet-type electric
motor, having permanent magnets 117 on the rotor and having a
stator 118, or an induction-type machine with a squirrel cage
mounted on the rotor (117) and having a stator 118. 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 112a,b and driven section 114 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 110, and in turn
provide rotational support to the motor rotor sections 112a,b and
driven section 114. In one embodiment, the bearings 120 may be
magnetic bearings, such as active or passive magnetic bearings. In
other embodiments, however, other types 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 111 of the housing 110. 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 FIG. 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 112a, 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 112b,
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 110
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 112a,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 111 or the second
end 113 of the housing 110. 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 111 or second end 113, 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
Oct. 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, CO.sub.2, N.sub.2,
ethane, propane, i-C.sub.4, n-C.sub.4, i-C.sub.5, n-C.sub.5, 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 110 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 114 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 CO.sub.2. 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 110 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 110 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 112a,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 prior to 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 110 and configured to cool
the first motor 102a and bearings 120 that support the first motor
rotor section 112a. 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 away from 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 115a 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
110 to cool the bearings 120, 122 that support the driven section
114 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 114, 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 114 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 116a and is
ultimately discharged into the first cavity 115a. The cooling fluid
coursing through internal cooling passage 152b may cool the
bearings 120 adjacent the second coupling 116b and in due course
escape into the second cavity 115b.
[0037] The cooling fluid in line 170 may be split or otherwise
introduced into internal cooling passages 152c and 152d defined
within the housing 110 to cool the second motor 102b and adjacent
bearings 120 that provide support to the second motor rotor section
112b. 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 115b 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 111 of the housing 110, and a second pressure balance
line 172b fluidly coupled to both the second return line 166b and
the second end 113 of the housing 110. 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 115a,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 FIG. 2, depicted is another exemplary fluid
compression system 200, similar in some respects to the fluid
compression system 100 described above in FIG. 1. Accordingly, the
system 200 may be best understood with reference to FIG. 1, where
like numerals correspond to like components that will not be
described again in detail. Similar to the system 100 of FIG. 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 110 having a first end 111 and a second
end 113.
[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 112a,b and a driven section
114. However, it is only the second motor rotor section 112b that
is coupled to the driven section 114 of the shaft 108 via the
second coupling 116b, whereas the first motor rotor section 112a is
coupled to the opposing end of the second motor rotor section 112b
via the first coupling 116a. 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 FIG. 2 may be
substantially similar to the closed-loop cooling system of FIG. 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 112a 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 112b of the shaft 108. It
will be further appreciated that the closed-loop cooling system of
FIG. 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
113 of the housing 110, 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 114 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 111 of the
housing 110 and is ultimately discharged via line 174. The cooling
fluid in the internal cooling passage 152b may escape into the
second cavity 115b. In one embodiment, the second cavity 115b 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 115b.
[0044] Cooling fluid collected in the first and second cavities
115a,b is discharged into a return line 176 fluidly coupled to each
cavity 115a,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 113 of the
housing 110 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 FIG. 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.
* * * * *