U.S. patent application number 10/943291 was filed with the patent office on 2006-03-23 for systems and methods for providing cooling in compressed air storage power supply systems.
Invention is credited to James A. Andrews, Scott D. Logan, David E. Perkins, Joseph F. Pinkerton, Robert E. Radke.
Application Number | 20060059937 10/943291 |
Document ID | / |
Family ID | 35613912 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060059937 |
Kind Code |
A1 |
Perkins; David E. ; et
al. |
March 23, 2006 |
Systems and methods for providing cooling in compressed air storage
power supply systems
Abstract
A system and method for cooling electrical machines (e.g.,
generators), sub-systems (e.g., power electronics), and components
(e.g., bearings) in an electrical generation system such as a
compressed air storage (CAS) energy system or a thermal and
compressed air storage (TACAS) energy system is provided. Cooling
is derived from the thermal expansion of a compressed gas, which
may be the same gas used to drive a turbine-generator of CAS or
TACAS energy system.
Inventors: |
Perkins; David E.; (Austin,
TX) ; Andrews; James A.; (Austin, TX) ; Radke;
Robert E.; (Dripping Springs, TX) ; Pinkerton; Joseph
F.; (Austin, TX) ; Logan; Scott D.; (Cedar
Park, TX) |
Correspondence
Address: |
Andrew Van Court;FISH & NEAVE IP GROUP
ROPES & GRAY LLP
1251 Avenue of the Americas
New York
NY
10020
US
|
Family ID: |
35613912 |
Appl. No.: |
10/943291 |
Filed: |
September 17, 2004 |
Current U.S.
Class: |
62/259.2 ;
62/401; 62/86 |
Current CPC
Class: |
Y02E 60/16 20130101;
H02K 5/20 20130101; F05D 2260/234 20130101; H02K 9/19 20130101;
F02C 7/18 20130101; Y02E 60/15 20130101; H02K 11/046 20130101; H02J
15/006 20130101; F02C 6/16 20130101 |
Class at
Publication: |
062/259.2 ;
062/086; 062/401 |
International
Class: |
F25B 9/00 20060101
F25B009/00; F25D 23/12 20060101 F25D023/12; F25D 9/00 20060101
F25D009/00 |
Claims
1. A method for cooling components and/or subsystems of an
electrical generation system, comprising: providing a source of
compressed gas; decompressing said compressed gas, the
decompression of which causes the temperature of said compressed
gas to drop to a predetermined temperature; and cooling at least
one component and/or subsystem with said decompressed gas.
2. The method defined in claim 1, further comprising: regulating
said decompressing such that said compressed gas is decompressed to
a predetermined pressure.
3. The method defined in claim 1, further comprising: using said
compressed gas to generate electrical power.
4. The method defined in claim 1, further comprising: maintaining
the temperature of said at least one component and/or subsystem at
a predetermined temperature with said decompressed gas.
5. The method defined in claim 1, wherein said cooling comprises
routing said decompressed gas to, or proximal to, an electrical
machine.
6. The method defined in claim 1, wherein said cooling comprises
routing said decompressed gas to, or proximal to, at least one
bearing that supports a rotor of a turbine-generator.
7. The method defined in claim 1, wherein said cooling comprises
routing said decompressed gas to, or proximal to, power
electronics.
8. The method defined in claim 1, further comprising: routing said
decompressed gas from said at least one component and/or subsystem
to at least one other component and/or subsystem.
9. The method defined in claim 1, further comprising: distributing
heat retained by said decompressed gas while cooling said at least
one component and/or subsystem to another component and/or
subsystem.
10. A system for cooling components and/or subsystems of an
electrical generation system, comprising: a source of compressed
gas; a valve coupled to said source of compressed gas and operative
to control the decompression of said compressed gas, the
decompression of which causes the temperature of said compressed
gas to drop to a predetermined temperature; and at least one
component and/or subsystem connected downstream of said valve and
is cooled by said decompressed gas.
11. The system defined in claim 10, wherein said valve is a
pressure regulator.
12. The system defined in claim 10, wherein said at least one
component and/or subsystem comprises an electrical machine.
13. The system defined in claim 10, wherein said at least one
component and/or subsystem comprises at least one bearing.
14. The system defined in claim 10, wherein said at least one
component and/or subsystem comprises power electronics.
15. The system defined in claim 10, further comprising: a housing
that receives said decompressed gas, said housing constructed to
route said decompressed gas to, or proximal to, said at least one
component and/or subsystem.
16. The system defined in claim 10, further comprising: a
turbine-generator connected to receive decompressed gas used to
cool said at least one component and/or subsystem, said
turbine-generator being driven by said decompressed gas to generate
power.
17. The system defined in claim 16, wherein said turbine generator
if further connected to receive said decompressed gas substantially
directly from said valve.
18. The system defined in claim 16, further comprising: a thermal
storage unit connected to receive decompressed gas used to cool
said at least one component and/or system, said thermal storage
unit heats said decompressed gas to a predetermined temperature,
and said thermal storage unit is connected to provide said heated
decompressed gas to said turbine-generator.
19. A method for cooling equipment in a backup energy system,
comprising: providing a source of compressed gas; selectively
decompressing said compressed gas, the decompression of which
causes the temperature of said compressed gas to drop to a
predetermined temperature; and routing said decompressed gas to, or
proximal to, an electrical machine to remove heat from said
electrical machine while said backup energy system is operating in
an emergency mode of operation.
20. The method defined in claim 19 further comprising: maintaining
an operating temperature of said electrical machine at a desired
operating temperature.
21. The method defined in claim 19, wherein said desired operating
temperature is a sub-ambient temperature.
22. The method defined in claim 19 further comprising: driving a
turbine with said selectively decompressed gas; and powering said
electrical machine when said turbine is being driven.
23. The method defined in claim 19 further comprising: routing a
first portion of said decompressed gas to a turbine; routing a
second portion of said decompressed gas to, or proximal to, said
electrical machine; and re-routing said second portion to said
turbine after said second portion has been routed to said
electrical machine.
24. The method defined in claim 23, wherein said re-routing
comprises heating said second portion prior to providing said
re-routed second portion to said turbine.
25. The method defined in claim 24, wherein said heating comprises
recovering heat from said electrical machine.
26. The method defined in claim 25, wherein said heating is
performed by an exhaustless heater.
27. The method according to claim 23 further comprising: routing a
third portion of said decompressed gas directly to at least one
bearing.
28. A method for providing backup power to a critical load in the
event of a disturbance in the supply of power from a primary power
source, comprising: providing a compressed gas; driving a turbine
with said compressed gas; powering an electrical machine with said
turbine to provide backup power; and cooling at least said
electrical machine with said compressed gas.
29. The method defined in claim 28, wherein said cooling comprises:
decompressing said compressed gas to provide a cool gas; and
routing said cool gas to, or proximal to, said electrical
machine.
30. The method defined in claim 29, wherein said routing comprises:
providing said cool gas to a stator housing of said electrical
machine.
31. The method defined in claim 29, wherein said routing comprises:
providing said cool gas to a bearing that supports a shaft being
driven by said turbine.
32. The method defined in claim 28, wherein said cooling comprises
maintaining said electrical machine at a desired operating
temperature.
33. A method for maintaining a desired operating temperature of an
electrical generator being driven by a turbine in an electrical
generation system, comprising: providing a compressed gas;
regulating the expansion of said compressed gas, the expansion of
which causes said compressed gas to cool; routing said cool gas to
a stator housing of said electrical generator; and removing heat
from said electrical generator as said cool gas passes through said
stator housing.
34. The method defined in claim 33 further comprising: driving a
turbine with said compressed gas; and powering said electrical
machine with said turbine to provide power.
35. A backup energy system, comprising: a source of compressed gas;
a valve connected to said source and operative to decompress said
compressed gas, the decompression of which causes the temperature
of said compressed gas to drop to a predetermined temperature; and
a path connected to said valve that routes said decompressed gas
to, or proximal to, an electrical machine to remove heat from said
electrical machine while said backup energy system is operating in
an emergency mode of operation.
36. The system defined in claim 35, further comprising: a turbine
connected to the portion of said path exiting said electrical
machine, said turbine powers said electrical machine as said
decompressed gas being routed through said path drives the turbine
blades of said turbine.
37. The system defined in claim 36, wherein said path is a first
path and said turbine comprises at least one bearing for supporting
a shaft, said system further comprising: a second path connected to
said valve that routes said decompressed gas to, or proximal to,
said at least one bearing.
38. The system defined in claim 35, further comprising: an
exhaustless heater connected to the portion of said path exiting
said electrical machine, said heater heats said decompressed gas to
a predetermined temperature; and a turbine connected to the output
of said exhaustless heater, said turbine powers said electrical
machine as said heated decompressed gas drives the turbine blades
of said turbine.
39. The system defined in claim 38, wherein said exhaustless heater
is a thermal storage unit.
40. The system defined in claim 35, further comprising: a stator
housing connected to said path and to said electrical machine, said
stator housing enables said decompressed gas to absorb heat
generated by said electrical machine.
41. The system defined in claim 35, wherein said path is a first
path and said electrical machine comprises at least one bearing for
supporting a shaft, said system further comprising: a second path
connected to said valve and routes said decompressed gas to, or
proximal to, said at least one bearing to remove heat from said at
least one bearing while said backup energy system is operating in
an emergency mode of operation.
42. The system defined in claim 35, wherein said path is a first
path, said first path routes said decompressed gas to said
electrical machine, a thermal storage unit, and to a turbine.
43. The system defined in claim 42, further comprising a second
path connected to said valve that routes said decompressed gas to
said turbine.
44. The system defined in claim 35, wherein said predetermined
temperature is a temperature lower than the temperature of said
compressed gas stored in said air source.
45. The system defined in claim 35, wherein said compressed gas is
compressed air.
46. The system defined in claim 35, wherein said valve is a
pressure regulator.
47. A system for maintaining a desired operating temperature of an
electrical generator being driven by a turbine in a compressed air
storage system, comprising: a source of compressed gas; a valve
that regulates the expansion of said compressed gas, the expansion
of which causes said compressed gas to cool; and a stator housing
mounted to said electrical machine and connected to receive said
cool gas from said valve, said stator housing constructed to enable
said cool gas to remove heat from said electrical generator as said
cool gas passes through said stator housing.
48. The system defined in claim 47, further comprising: an
exhaustless heater connected to receive said cool gas exiting said
stator housing, said heater heats said cool gas to a predetermined
temperature, wherein said turbine is connected to receive said
heated gas from said heater.
49. The system defined in claim 47, further comprising: at least
one bearing housing connected to receive said cool gas from said
valve, said at least one bearing housing constructed to enable said
cool gas to remove heat generated by a bearing housed within said
bearing housing.
50. The system defined in claim 48, wherein said at least one
bearing housing is coupled to, or within, said electrical
machine.
51. The system defined in claim 48, wherein said at least one
bearing housing is coupled to, or within, said turbine.
52. The system defined in claim 48, wherein said gas exiting said
at least one bearing housing is combined with said gas exiting said
stator housing.
53. The system defined in claim 48, wherein said valve is a first
valve, said system further comprising: a second valve connected to
said first valve and operative to reduce the pressure of said cool
gas provided to said at least one bearing housing, and wherein said
gas exiting said at least one bearing is vented to atmosphere.
54. The system defined in claim 47, further comprising control
circuitry operative to control the operation of said valve.
55. A stator housing, comprising: a stator jacket having an inner
diameter, an outer diameter, and an annular groove of a
predetermined width and depth; and a stator jacket sleeve having an
inlet port and an outlet port and constructed to slide over said
stator jacket to provide an airtight seal over said annular groove
such that when said sleeve is slid in position over said jacket, an
annular channel is formed to permit a fluid to flow from said inlet
port through said annular channel to said outlet port.
56. The housing defined in claim 55, wherein said stator jacket
sleeve has an inner diameter that is greater than said outer
diameter of said stator jacket but only to an extent that yields
said airtight seal.
57. The housing defined in claim 55, wherein said stator jacket
comprises a plurality of o-ring grooves.
58. The housing defined in claim 57 further comprising an o-ring
positioned in each of said plurality of o-ring grooves.
59. The housing defined in claim 55, wherein said inner diameter of
said jacket is such that said jacket slides over the stator of an
electrical machine.
60. A stator housing, comprising: an inlet port; an outlet port; at
least one annular channel that is connected to said inlet and
outlet ports to permit flow of fluid from said inlet port through
said at least one annular channel to said outlet port; and a
pressure sleeve that is fixed to an inner diameter of said housing
to provide pressure containment of fluid flowing through said at
least one annular channel.
61. The housing defined in claim 60, wherein said at least one
annular channel comprises at least two annular channels, said
housing further comprising: a first axial flow channel connected to
said input port and to said at least two annular channels; and a
second axial flow channel connected to said output port and to said
at least two annular channels.
62. The housing defined in claim 60, wherein said stator housing is
cast.
63. The housing defined in claim 60, wherein said stator housing is
machined.
64. An electrical generator assembly, comprising: a generator
comprising a stator having an outer diameter; and a stator housing
having an inner diameter that enables said housing to fit flush
against the outer diameter of said stator, said stator housing
comprising: an inlet port; an outlet port; at least one annular
channel connected to said inlet and outlet ports to permit flow of
fluid from said inlet port through said at least one annular
channel to said outlet port; and a pressure sleeve that forms said
inner diameter of said housing and provides pressure containment of
fluid flowing in said at least one annular channel.
65. The assembly defined in claim 64, wherein said pressure sleeve
fits flush against said outer diameter of said stator.
66. The assembly defined in claim 64, wherein said stator fits
flush against said pressure sleeve.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to systems and methods for removing
heat from a system. More particularly, this invention provides heat
exchanging techniques to remove heat from various components and/or
subsystems of electrical generation systems such as thermal and
compressed air storage (TACAS) backup energy systems or compressed
air storage (CAS) backup energy systems. Electrical generation
systems may include components and/or subsystems such as electrical
machines and power electronics that may require cooling.
[0002] Electrical machines such as generators and motors are well
known in the art. Such machines are used in thousands of different
applications, some of which include the generation of electric
power. Electric power is generated, for example, when the rotor of
a generator is driven by a prime mover (e.g., turbine) to produce a
rotating magnetic field within the machine. The rotating magnetic
field induces voltage within the stator windings of the generator
that is output as electrical energy.
[0003] During operation, heat may be generated by the stator core,
stator windings, bearings, rotor, and/or other sources during
generator operation. Such heat may be detrimental to generator
performance and operation. For example, excess heat can decrease
the flux capacity of permanent magnets in the generator and damage
generator components such as bearings and generator windings.
[0004] Conventional methods for cooling the stator to remove heat
include auxiliary cooling fans, circulating water systems, and/or
circulating oil systems. Other systems may use compressors to route
bleed air over the stator to cool the generator. Though such
cooling systems are able to cool generators, they require
substantial maintenance and a supply of power to operate. Moreover,
such cooling systems are typically unable to maintain an operating
temperature of the generator below a desired temperature (e.g., an
ambient air temperature).
[0005] Generators are often coupled to a turbine by a shaft to form
a power generation system known as a turbine-generator.
Turbine-generators are highly customizable for a given application
such as a micro-turbine system available from Capstone Turbine
Corporation of Chatsworth, Calif. This micro-turbine system
operates at high shaft speeds, drives a permanent magnet alternator
(e.g., a generator rotor), and requires cooling to remove heat from
the stator during operation.
[0006] During operation, such micro-turbine systems derive stator
cooling from shaft-mounted compressor inlet air, compressor bleed
air, auxiliary cooling fans, or circulating oil. The turbine is
powered by a fuel source (e.g., gas, coal, nuclear) that heats the
air being supplied to drive the turbine. Thus, as long as fuel is
supplied, the turbine-generator can provide power. Accordingly,
such micro-turbines and other fuel-powered turbine-generators can
run continuously for thousands or tens of thousands of hours.
However, such turbine-generators are subject to several drawbacks,
at least one being pollution. Combustion of fuel (or in nuclear
applications fission of a fuel) is necessary to drive the turbine.
Another drawback is that costly or maintenance intensive bearings
(e.g., air bearings, oil film journal bearings, or magnetic
bearings) are needed to sustain the long operational lives of these
turbine-generators.
[0007] Power electronics are often used in electrical generation
systems to perform various tasks including, but not limited to,
driving electrical machines, conditioning power derived from an
electrical machine, and selectively providing power to subsystems
(e.g., a flywheel energy backup system or a thermal storage unit).
Heat may be generated while power electronics are performing these
tasks. Conventional techniques for removing heat from power
electronics include using a finned heat sink and a fan. The heat
sink transfers heat from the power electronics to the ambient
environment (e.g., the air surrounding the heat sink). The fan may
be used to force air over the fins to improve the rejection of heat
to the ambient environment. Water cooling may be used in power
electronics that operate at a higher power density.
[0008] These power electronic cooling techniques suffer from many
of the same drawbacks experienced in cooling electrical machines.
That is, substantial maintenance and a supply of power to operate
the cooling mechanism may be required. In addition, such cooling
systems are typically unable to maintain an operating temperature
of the power electronics below a desired temperature (e.g., an
ambient air temperature). Furthermore, the power density is usually
limited to a finite power density because conventional cooling
systems lack the requisite cooling capacity to prevent the power
electronics from overheating if such finite power density is
exceeded.
[0009] In view of the foregoing, it is an object of this invention
to provide improved cooling of components and/or subsystems of an
electrical generation system.
[0010] It is also an object of the present invention to provide
improved cooling of an electrical machine and power electronics
used in an electrical generation system.
[0011] It is an additional object of the present invention to
provide improved cooling that reduces maintenance requirements.
[0012] It is still a further object of the present invention to
promote electrical machine design flexibility and to reduce
electrical machine manufacturing cost.
SUMMARY OF THE INVENTION
[0013] These and other objects of the invention are accomplished
using the expansion of stored compressed gas, which is the same
compressed gas used to drive a turbine-generator, to cool
components and/or subsystems (e.g., electrical machine, power
electronics, etc.) of an electrical generation system (e.g., a
TACAS or CAS backup energy system). As gas expands, it cools. Thus,
in accordance with this invention, compressed gas is expanded
across a valve, the expansion of which cools the gas to, for
example, sub-ambient temperatures, and is then routed to one or
more components and/or subsystems of the electrical generation
system.
[0014] One of the components and/or subsystems cooled by the cool
gas is an electrical machine, sometimes referred to herein as an
electrical generator or generator. The cool gas may be routed
through a stator housing and removes heat from the electrical
generator, thereby yielding a desired electrical generator
operating temperature. The heat being removed by the cold gas may
be generated by electrical resistance losses in the stator
windings, hysteresis and/or eddy current losses in the laminated
stator core, stray load losses on the rotor due to laminated stator
core slot harmonics, and/or armature winding current harmonics,
rotor windage losses, and friction losses in the bearings located
within the electrical machine. In addition, the cold gas may remove
heat transferred to the electrical machine by conduction from a
turbine, which drives the rotor of the electrical generator.
[0015] The cool gas can be routed to other components and/or
subsystems of the electrical generation system in addition to, or
to the exclusion of, the electrical generator. For example, cool
gas may be routed directly to bearings (e.g., thrust-end and
non-thrust end bearings) housed in the electrical machine. As
another example, cool gas may be routed directly to a bearing
housed (e.g., a thrust-end bearing) in the turbine. Cooling such
bearings, regardless of whether they are located in the electrical
machine or turbine, extends their operational life. As a further
example, cool gas may be routed to a power electronics housing to
cool power electronics being utilized in connection with the
electrical generation system.
[0016] The cooling means according to the present invention may be
implemented in a CAS backup energy system or a TACAS backup energy
system. Such systems may provide emergency backup power in the
event of a disturbance in utility power. For example, if utility
power fails, compressed gas is drawn from an air reservoir (e.g.,
pressure tank) and supplied to a turbine. The compressed gas drives
the turbine, which in turn powers the electrical generator. Thus,
the compressed gas being used to ultimately generate electrical
power is also used to cool the components and/or subsystems of the
backup energy system.
[0017] The cooling means according to the present invention may
also be implemented in other systems that use compressed gas. For
example, continuously operating TACAS or CAS systems (e.g., systems
that do not provide backup power) may be used to provide a
continuous supply of power. Such systems may use a compressor to
provide continuous compressed gas for use in cooling components
and/or subsystems and for driving a turbine-generator.
[0018] In TACAS systems, a portion of the cool gas may be heated to
a predetermined temperature before being routed to the turbine. The
cool gas may be heated by a heating system, such as a thermal
storage unit, to increase the operating efficiency of the turbine.
If desired, the portion of the cool gas being heated by the heating
system may be routed through certain components and/or subsystems
(e.g., stator housing and/or power electronics housing) before
being supplied to the heating system. Such an arrangement may
improve the heating discharge efficiency of the heating system
because heat loss picked up by the cool gas passing through the
components and/or subsystems is recovered and delivered to the
heating system. Thus, a regenerative heating mechanism is built
into the operation of the TACAS system which enhances its operating
efficiency.
[0019] An advantage of the present invention is that the
temperature of the gas being routed to the components and/or
subsystems may be substantially lower than the heat-exchanging
mediums (e.g., ambient air, oil, water, etc.) used by conventional
heat exchangers. As a result, this correlates to a lower operating
temperature not previously achieved in prior art cooling systems. A
lower operating temperature promotes reduced generator sizing
(e.g., smaller stator core and stator windings and smaller rotors)
and increased generator design flexibility, and thus less cost.
Moreover, reduced sizing further decreases spool-up time required
for the turbine-generator to start producing emergency power.
Another advantage of the present invention is that independent
cooling systems, such as fans, compressors, oil circulating
systems, are not needed to provide cooling. This correlates to less
cost, elimination of a need to power such systems, elimination of
maintenance, increased reliability, and a more compact system.
[0020] Another aspect of the present invention includes a power
electronics housing which routes cool gas in direct contact with,
or proximal to, the power electronics of the electrical generation
system. The power electronics housing may include a thermally
conductive body to which the power electronics are mounted and heat
sinks. Cool gas derived in accordance with the principles of the
invention may be routed through the thermally conductive body to
extract heat generated by the power electronics during an active
mode of operation of the electrical generation system. The heat
sinks may extract heat from the power electronics during both
standby and active modes of operation of the electrical generation
system.
[0021] An advantage of cooling the power electronics with the
expanded gas is that it increases the cooling capacity beyond that
previously achieved with conventional cooling techniques, thereby
permitting the power density of the power electronics to be
increased to levels not previously sustainable by conventional
cooling techniques.
[0022] Another aspect of the present invention includes stator
housings which route cool gas in direct contact with, or proximal
to, the wound stator core of an electrical generator. The stator
housing may be machined to fit flush (e.g., air tight) against the
stator core to maximize heat exchanging efficiency. Such stator
housings may have one or more annular channels for routing cool gas
around the stator. Stator housings may include a pressure sleeve to
prevent gas from damaging the laminated stator core and/or windings
or appurtenances thereof during power generation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other features of the present invention, its
nature and various advantages will become more apparent upon
consideration of the following detailed description, taken in
conjunction with the accompanying drawings, in which like reference
characters refer to like parts throughout, and in which:
[0024] FIG. 1 is a schematic diagram of a known thermal and
compressed air storage backup energy system;
[0025] FIG. 2 is a block diagram that generally illustrates how a
cooling fluid is derived in accordance with the principles of the
present invention;
[0026] FIG. 3 is a schematic diagram of a thermal and compressed
air storage backup energy system showing a valve and gas routing
configuration for cooling a generator in accordance with the
principles of the present invention;
[0027] FIG. 4 is a schematic diagram of a thermal and compressed
air storage backup energy system showing a valve and gas routing
configuration for cooling bearings housed in a generator in
accordance with the principles of the present invention;
[0028] FIG. 5 is a schematic diagram of a thermal and compressed
air storage backup energy system showing a valve and gas routing
configuration for cooling a bearing housed in a turbine in
accordance with the principles of the present invention;
[0029] FIG. 6 is a schematic diagram of a thermal and compressed
air storage backup energy system showing a valve and gas routing
configuration for cooling power electronics in accordance with the
principles of the present invention;
[0030] FIG. 7 is a three-dimensional exploded perspective view of a
power electronics housing in accordance with the principles of the
present invention;
[0031] FIG. 8 is cross-sectional view of a turbine-generator having
a stator housing in accordance with the principles of the present
invention;
[0032] FIG. 9A is a three-dimensional perspective view of a stator
jacket of the stator housing of FIG. 8 in accordance with the
principles of the present invention;
[0033] FIG. 9B is a three-dimensional perspective view of a jacket
housing of the stator housing of FIG. 8 in accordance with the
principles of the present invention
[0034] FIG. 10A is a three-dimensional perspective view of an
alternative stator housing in accordance with the principles of the
present invention;
[0035] FIG. 10B is a cross-sectional view the stator housing taken
along lines B-B of FIG. 10A in accordance with the principles of
the present invention;
[0036] FIG. 10C is a cross-sectional view of the stator housing
taken along lines C-C of FIG. 10A in accordance with the principles
of the present invention;
[0037] FIG. 11 is a cross-sectional view a generator assembly
having the stator housing of FIG. 10A in accordance with the
principles of the present invention;
[0038] FIG. 12A is cross-sectional view of an alternative stator
housing in accordance with the principles of the present
invention;
[0039] FIG. 12B is three-dimensional, partial cutaway, perspective
view of the stator housing of FIG. 12A in accordance with the
principles of the present invention;
[0040] FIG. 13 is three-dimensional, partial cutaway, perspective
view of another alternative stator housing in accordance with the
principles of the present invention;
[0041] FIG. 14A is cross-sectional view of yet another alternative
stator housing in accordance with the principles of the present
invention; and
[0042] FIG. 14B is three-dimensional, partial cutaway, perspective
view of the stator housing of FIG. 14A in accordance with the
principles of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0043] Cooling according to the principles of the present invention
can be implemented in many different types of electrical generation
systems, particularly systems that derive electrical power from
stored compressed gas. Such systems include, but are not limited
to, CAS systems and TACAS systems. To further facilitate
understanding of the present invention, a brief discussion of such
a system is provided to set forth a possible framework in which the
invention may be practiced.
[0044] FIG. 1 shows a schematic of a known TACAS backup energy
system 100. Backup energy system 100 may be connected to utility
input 110 which supplies power to a critical load 180 during normal
operating conditions. Persons skilled in the art will appreciate
that utility input 110 may be any type of primary power source, AC
or DC.
[0045] Backup energy system 100 includes motor 120, compressor 122,
one way valve 124, pressure tank 126, valve 128, thermal storage
unit 130, turbine 140, electrical machine 150, power conversion
circuitry 160, and control circuitry 190. If desired, optional
transient power supply 170 (e.g., flywheel energy storage system,
ultracapacitor, batteries, etc.) may also be provided. Electrical
machine 150 may be a machine capable of functioning as a motor and
a generator. During normal operating conditions, utility input 110
supplies power to critical load 180. Utility input 110 may also
power motor 120, which drives compressor 122 to charge pressure
tank 126 with compressed air. The compressed air may be pushed
through one way valve 124 to prevent feedback. Persons skilled in
the art will appreciate that pressure tank 126 can be substituted
with a different type of air storage reservoir such as a cavern
(e.g., underground salt dome).
[0046] Although control circuitry 190 is not shown to be connected
to any of the components included in backup energy system 100,
persons skilled in the art will appreciate that control circuitry
190 can perform control and monitoring functions well known and
understood in the art. For example, control circuitry 190 can cause
valve 128 to OPEN when utility power fails.
[0047] In the event of a power failure, compressed air stored in
pressure tank 126 is routed through valve 128 to thermal storage
unit 130. Thermal storage unit 130 heats the compressed air prior
to being routed to turbine 140. Thermal storage unit 140 may be an
exhaustless heater (e.g., a non-polluting heater). Examples of and
discussion of the operation of such thermal storage units can be
found, for example, in co-pending, commonly assigned U.S. patent
application Ser. No. 10/738,825, filed Dec. 16, 2003, U.S. patent
application Ser. No. ______, filed ______ (Attorney Docket No.
AP-53), and U.S. patent application Ser. No. ______, filed ______
(Attorney Docket No. AP-46 CIP), each of which are hereby
incorporated by reference in their entireties. The heated
compressed air drives the turbine which in turn powers electrical
machine 150. Electrical machine 150 operates as a generator and
provides electrical power to power conversion circuitry 160 which
conditions the power before providing it to critical load 180.
[0048] The foregoing discussion of backup energy system 100 is not
intended to be a thorough discussion of TACAS systems, but is
intended to provide a general framework of a system in which the
present invention may be implemented. For a more detailed
explanation of TACAS uninterruptible power supply systems, as
briefly described above, and variations thereof, see co-pending,
commonly assigned U.S. patent application Ser. No. 10/361,728,
filed Feb. 5, 2003, which is hereby incorporated by reference in
its entirety. The present invention can be incorporated in other
emergency backup power delivery systems such as those described in
co-pending, commonly assigned U.S. patent application Ser. No.
10/361,729, filed Feb. 5, 2003, which is hereby incorporated by
reference in its entirety.
[0049] The CAS and TACAS backup energy systems may be used in the
context of industrial backup utility power. Alternatively, the
present invention may be used in any application associated with
generating power, such as in thermal and solar electric plants. The
present invention may be used in continuously operating CAS and
TACAS systems to generate a continuous supply of power.
Furthermore, the present invention may be used in any other
application using stored compressed gas in one form or another.
[0050] FIG. 2 is a block diagram illustrating how cool gas is
derived and used to cool components and/or subsystems of an
electrical generation system in accordance with the principles of
the present invention. The cool gas is obtained by expanding a
stored compressed gas across valve 220. The compressed gas is
stored at air source 210, which may be a pressure tank, a cavern, a
salt dome, or other device capable of containing a pressurized gas.
Valve 220 may be a device capable of turning down the pressure of
the compressed gas received from air source 210 to a predetermined
pressure. For example, valve 220 may be a pressure regulator or a
flow control valve.
[0051] As the compressed gas passes through valve 220, it
decompresses (e.g., expands) to a lower pressure than that of the
compressed gas stored in air source 210. This HIGH-to-LOW pressure
drop results in a Joule-Thompson expansion of gas that results in a
substantial drop in gas temperature. For example, in a controlled
environment, expansion of gas from 4500 PSIA to 400 PSIA can
generate gas temperatures below 30 degrees centigrade. Such cool
gas temperatures are much lower than temperatures achieved using
conventional fans and water or oil cooling systems.
[0052] This cool gas is then used to cool various components and/or
subsystems of an electrical generation system 230. It will be
appreciated that the cool gas may be used to cool components and/or
subsystems 230 in a variety of different ways. For example, the
cool gas may be routed to components and/or subsystems
independently of each other. That is, a separate path may route
cool gas to each component and/or subsystem. As another example,
the cool gas may be routed to components and/or subsystems in
combination with each other. That is, a single series path or
multiple parallel paths may be used to route cool gas to two or
more components and/or subsystems.
[0053] If desired, the cool gas may be routed to a particular
component and/or subsystem and be immediately exhausted to the
ambient environment. In other configurations, the cool gas may be
routed to other components and/or subsystems of an electrical
generation system after cooling a desired component or subsystem.
For example, cool gas used to cool an electrical machine may be
routed to a thermal storage unit and then to a turbine.
[0054] It will be appreciated that the present invention has a
number of different applications, but to keep the discussion from
becoming too abstract, and to provide better comprehension and
appreciation of the invention, references will frequently be made
to specific uses of the invention. It is emphasized that these
examples merely represent a few of the many possible applications
of the invention.
[0055] FIG. 3 is a schematic of a backup energy system 300 that
cools an electrical machine in accordance with the principles of
the present invention. Backup energy system 300 is similar to
system 100 as described above, but is constructed to take advantage
of a naturally occurring cooling process that occurs during
decompression of a gas (e.g., air or argon). Backup system 300 may
include utility input 310, motor 320, compressor 322, one way valve
324, air reservoir 328, valve 330, valve 332, thermal storage unit
340, turbine 350, and electrical machine 360. It is understood that
system 300 can also include other components such as compressor 122
and motor 120 of FIG. 1, but have been omitted to avoid cluttering
the figure. It is further understood that turbine 350 and
electrical machine 360 may function together as a
turbine-generator, but are shown independent of each other to
facilitate ease of discussion.
[0056] Valve 330 regulates the pressure of the gas provided from
air source 328 as the gas is delivered downstream to turbine 350.
As the gas reaches valve 332, valve 332 directs a portion of the
regulated air to path 336 and the balance of the regulated air to
path 338. The gas in path 338 is routed to electrical machine 360
and then routed to thermal storage unit 340, which heats the gas.
The gas in path 336 bypasses thermal storage unit 340, but is
recombined with heated gas exiting thermal storage unit 340 before
being supplied to turbine 350. This combined gas then drives
turbine 350, which in turn drives electrical machine 360 to produce
electrical power.
[0057] The particular valve (e.g., valves 330 and 332) and gas
routing configuration (e.g., paths 336 and 338) shown in FIG. 3
employs a dual gas path routing system to achieve a greater degree
of control over the inlet temperature and pressure of the gas being
supplied to turbine 350. Examples of such dual path routing systems
are described in more detail in co-pending, commonly assigned U.S.
patent application Ser. No. ______, filed (Attorney Docket No.
AP-48) and co-pending, commonly assigned U.S. patent application
Ser. No. ______, filed ______ (Attorney Docket No. AP-50), both of
which are hereby incorporated by reference in their entireties. If
desired, the present invention can be implemented in a single path
gas routing system for routing gas to a turbine. In such an system,
bypass path 336 may be omitted.
[0058] During an emergency mode of operation, valve 330 regulates
the expansion of the compressed gas being supplied by air reservoir
328 to a predetermined pressure. This creates a HIGH-to-LOW
pressure drop, resulting in a Joule-Thompson expansion of gas that
results in a substantial drop in the gas temperature.
[0059] After the gas expands, the cool gas is routed to electrical
machine 360. More particularly, the cool gas may be routed to a
stator housing (not shown), such as those shown in FIGS. 8-14, to
remove heat being produced during the generation of electric power.
The stator housing permits cool gas to be directly applied to, or
routed proximal to, the stator of electrical machine 360. A stator
may include the stationary portions of the electrical machine,
including a stator core, stator core laminations, and stator
windings.
[0060] As the cold air passes through the stator housing, heat
generated by electrical machine 360 during operation may be
absorbed by the cool gas. Thus, the stator housing functions as a
heat exchanger and the cool gas functions as the heat exchanging
medium. After the cool gas absorbs heat from electrical machine
360, the partially heated gas may be routed to thermal storage unit
340.
[0061] An advantage of routing the partially heated gas to thermal
storage unit 340 is that it increases the heating discharge
efficiency of thermal storage unit 340. Thus, thermal storage unit
340 may not have to impart as much heat energy into the gas being
supplied to turbine 350 to discharge the gas at a predetermined
temperature. Moreover, recovering the heat losses of electrical
machine 360 in the gas being supplied to thermal storage unit 340
may enable thermal storage unit 340 to be sized smaller and/or
operate at a lower temperature.
[0062] The cooling methodology according to the principles of the
invention can prevent other heat sources from adversely affecting
the operating temperature of electrical machine 360. For example,
the cooling of the stator can extract heat from bearings housed
within electrical machine 360. Such bearings may include a non
thrust-end bearing, a thrust-end bearing, or both. An added benefit
of cooling bearings is that it prolongs their operational life.
Stator cooling may extract heat from the rotor of electrical
machine 360. Other sources of heat removed by the cool gas include
resistance losses, eddy current losses, and hysteresis losses.
[0063] Another example of heat being removed from electrical
machine 360 may include heat that is imparted to electrical machine
360 by turbine 350. In some applications, turbine 350 may be
directly coupled to electrical machine 360. Thus, the heat of the
inlet gas being supplied to drive turbine 350 may be transferred to
electrical generator by way of conduction or convection, or a
combination thereof.
[0064] Removing heat from electrical machine 360 according to the
principles of the invention may result in a lower operating
temperature than that achieved with conventional air, water, or oil
cooled machines that reject heat to ambient conditions. This lower
operating temperature allows current and flux density of the stator
to be driven higher than the current and flux density that can be
achieved at higher temperatures. This results in a greater current
and flux carrying capacity for a given volume of the stator,
resulting in a reduction in the volume of stator material (e.g.,
iron and copper) needed to construct a generator.
[0065] A similar advantage is realized for use of magnetic
materials such as a rotor. With magnetic materials, the lower
operating temperature results in increased flux density for a given
volume of magnetic material. Thus, the volume of the magnetic
material can be reduced, yet still provide the same electrical
carrying capacity. The reduction in the volume of stator and
magnetic materials reduces generator manufacturing costs and
promotes increased generator design flexibility.
[0066] A further benefit of the reduction of rotor materials is
that the polar moment of inertia is decreased. This may result in
faster turbine-generation spool up time, thereby decreasing a time
lag in providing backup power in the event of a power failure.
Moreover, by bringing the turbine up to speed faster, less power
may need to be drawn from a transient power source (e.g., flywheel
backup energy system) during the transition period between utility
power failure and the time it takes for the turbine generator to
get up to speed and supply backup power.
[0067] It will be appreciated that the cooling methodology being
used in accordance with this invention can use regenerative
heating, which may result in a more efficiently operating and cost
effective backup power supply system. Regenerative heating may be
realized by redirecting heat picked up from electrical generator
360 (while being driven by turbine 350) to thermal storage unit
340. Thus, the same gas that cools, yet ultimately drives the
generator may be used to improve the operating efficiency of
thermal storage unit 340 and turbine 350.
[0068] FIG. 4 shows a backup energy system 400 employing cooling
according to the principles of the present invention to separately
cool bearings that are housed within the electrical machine. The
bearings may support a shaft load in a high-speed turbine-generator
arrangement, and thus may be prone to overheating. If desired,
bushing may be used in place of the bearings. Backup energy system
400 is similar to system 300 of FIG. 3 except that valve 434 may be
coupled downstream from valve 432 to route cool gas directly to
bearings 464 via path 439. One of bearings 464 may be a thrust end
bearing and the other may be non-thrust end bearing. As shown,
valve 434 is connected downstream from valve 432 and routes cool
gas at a predetermined pressure to path 439. Path 439 may be
connected to two air-tight chambers (not shown), which each house a
bearing 464, that permits the cool gas to extract heat from
bearings 464. The heat extracted from bearings 464 may be vented to
the ambient environment.
[0069] In an alternative arrangement, heat extracted from bearings
464 may be fed back into path 426 instead of being vented to
atmosphere. However, such an arrangement may require path 439 to be
connected directly downstream from valve 432, as opposed to being
connected downstream from a valve such as valve 434--that is, valve
434 is omitted. Moreover, this alternative arrangement permits heat
extracted from the stator jacket to be combined with heat extracted
from bearings 464 prior to being routed to thermal storage unit
440. As discussed above, recovering this heat energy may improve
the heating efficiency of thermal storage unit 440, thus permitting
increased flexibility in sizing the thermal storage unit and
adjusting the operating temperature of the thermal storage
unit.
[0070] FIG. 5 shows a backup energy system 500 employing cooling
according to the principles of the present invention to separately
cool a bearing that is housed within turbine 550. Backup energy
system 500 is similar to system 400 of FIG. 4, except that cool gas
is routed to bearing 554 (e.g., a thrust end bearing) housed within
turbine 550. As shown path 539 routes cool gas received downstream
of valve 532 to a bearing chamber (not shown), where heat is
extracted from end bearing 554 and routed to thermal storage unit
540 via path 526. Flow restriction device 570 may be used to limit
the quantity of cool gas delivered to the bearing.
[0071] Alternatively, instead of re-directing heat extracted from
bearing 554 back to thermal storage unit 540, the extracted heat
may be exhausted to the ambient environment. In such an
arrangement, it may be necessary to add an additional valve in path
539 to step down the pressure of the cool gas supplied by valve 532
to prevent excessive loss of compressed gas.
[0072] An advantage of cooling bearings in accordance with the
invention, coupled with the fact that backup power systems 300,
400, and 500 spend a majority of their operational lives in a
standby mode of operation, is that low cost bearings such as grease
lubricated bearings can be used. The cool gas may sufficiently cool
such bearings when the backup power system is in an active mode of
operation, thereby obviating the need to use conventional cooling
techniques such as oil cooling.
[0073] FIG. 6 shows a backup energy system 600 employing cooling
according to the principles of the present invention to cool power
electronics 662. Backup energy system 600 may include utility power
610 (e.g., an AC or DC power source), air source 628, valves 630
and 632, thermal storage unit 640, turbine 650, electrical machine
660, power electronics 662, transient power supply 670 (e.g.,
flywheel energy system), and load 680. Other components, such as a
motor and compressor for charging air source 628 are not shown to
avoid overcrowding the figure. In addition, paths for routing cool
gas to electrical machine 660 and bearings are not shown to avoid
overcrowding the figure, though it is understood that such paths
may be provided in backup energy system 600.
[0074] Power electronics 662 may continuously operate regardless of
whether backup energy system 600 is operating in a standby mode,
transient mode, or active mode. Therefore, power electronics 662
may continuously emit heat regardless of the mode of operation.
Power electronics 662 may include rectification electronics (e.g.,
AC to DC converters), inverting electronics (e.g., DC to AC
converters), capacitors, inductors, control circuitry, and other
components known to those skilled in the art.
[0075] During a standby mode, power electronics 662 may power
thermal storage unit 640 and transient power supply 670. Thermal
storage unit 640 may be powered so that it is heated to a
predetermined temperature suitable for heating gas passing
therethrough during an active mode of operation and to overcome
heat losses such as, for example, losses due to the environment.
Transient power supply 670 may be powered so that it can
instantaneously supply power to load 680 when utility power 610
fails.
[0076] Power electronics 662 may condition power supplied to load
680 by transient power supply 660 during a transient mode of
operation. Power electronics 662 may also condition power supplied
to load 680 from electrical machine 660 during an active mode
operation. It is during the transient and active modes of operation
that power electronics 662 emits the most heat. This heat is
removed using cooling in accordance with the principles of the
invention.
[0077] When backup energy system 600 emerges from a standby mode of
operation, compressed gas from air source 628 is expanded across
valve 630, the expansion of which cools the gas, and is directed to
power electronics 662. More particularly, valve 632 may direct cool
gas to a power electronics housing (not shown) to remove heat
generated by power electronics 662. After the gas exits the power
electronics housing, it may be directed to thermal storage unit 640
before being routed to turbine 650. The heat picked up from power
electronics 622 "pre-heats" the gas before it is supplied to
thermal storage unit 640, increasing its discharge efficiency.
[0078] During standby mode, power electronics 662 generates heat,
but generally not as much heat that is generated during the
transient and active modes of operation. Because heat losses are
less, a natural convection heat sink (not shown) may function as
the primary cooling mechanism during standby mode.
[0079] FIG. 7 shows a three-dimensional exploded view of a power
electronics housing 700 in accordance with the principles of the
present invention. Power electronics 762 may be mounted on
gas-cooled heat sink 724, which includes air inlet 720 and air
outlet 722. Heat sink 724 may be made using materials such as, for
example, aluminum, copper, gold, iron, steel, and alloys thereof,
or any other material with suitable thermal conductivity
properties. During the transient and active modes, cool gas is
routed to heat sink 724, entering at air inlet 720 and exiting at
air outlet 722. Heat sink 724 may have channels (not shown) for
routing the cool gas within the heat sink to maximize surface area
of gas exposure to heat sink 724, yielding greater heat exchanging
capacity.
[0080] Mounting brackets 710 and 714 may secure natural convection
heat sinks 730 and 732 adjacent to gas-cooled heat sink 724 and to
capacitors 712. Natural convection heat sinks 730 and 732 can
assist gas-cooled heat sink 724 in removing heat generated by power
electronics 762 during transient and active modes of operation.
Also, during standby modes of operation, natural convection heat
sinks 730 and 732 may remove heat generated by power electronics
762. Air currents that are naturally present due to the differences
in temperature at different heights of the system may enable heat
sinks 730 and 732 to remove heat from power electronics 762.
Natural convection heat sinks 730 and 732 may be made from
materials such as, for example, plastic, aluminum, copper, gold,
iron, steel, any alloys thereof, or any other material with
suitable thermal conductivity properties.
[0081] Removing heat from power electronics 762 according to the
principles of the present invention results in a greater cooling
capacity than that achieved with conventional air, water, or oil
cooled techniques. One benefit derived from the increased cooling
capacity may be that the operating temperature of power electronics
can be decreased to temperature levels lower than that achieved
with conventional cooling techniques. For example, in one
embodiment, the operating temperature of the power electronics may
be maintained below or near ambient temperatures.
[0082] Another benefit is that increased levels of power density
can be sustained for a long period of time without risk of
overheating power electronics 762. This may enable the power
electronics to operate in a "saturated" power density mode. A
"saturated" power density mode may be an operating condition in
which cooling according to the present invention permits the power
density of the power electronics to be increased to levels above
and beyond that which can be sustained by conventional cooling
systems (e.g., forced air, water, or oil cooling). That is, if such
increased levels of power density are demanded of power electronics
being cooled with conventional cooling systems, the power
electronics may cease to function, or if it can sustain operation,
such operation may be momentary (e.g., a few seconds).
[0083] The power electronics may operate in a normal power density
mode when lower levels of power density are required. Examples of
normal power density mode include standby modes of operation and
modes in which conventional cooling techniques, if such techniques
were to be used, may sufficiently cool the power electronics.
[0084] FIG. 8 shows a cross-sectional view of a generator-turbine
assembly having a stator housing 810 enclosing stator 820 in
accordance with the principles of the present invention. Stator 820
may sometimes be referred to herein as a wound stator core, which
may include the stator core, stator laminations, and stator
windings. As shown, electrical machine 860 may be mounted to
turbine 850 via mounting screw 862. Thrust end bearing 858 and
non-thrust end bearing 858 may support turbine-generator rotor 866.
During operation, heated compressed air is provided to air plenum
854 to drive turbine fan 856. The spinning of turbine 856 causes
rotor 866 to rotate, the rotation of which creates a magnetic field
that induces flux in stator 820. Time varying flux in wound stator
core 820 generates voltage in the stator windings that causes
current to flow in the windings when connected to an electrical
load. The time varying flux generates heat due to eddy currents and
hysteresis in the laminated core. Furthermore, currents in the
windings generate heat due to resistive losses. Core and winding
losses are removed by cool gas passing through stator housing
810.
[0085] Cool gas derived in accordance with this invention is
supplied to inlet 812, which is connected to an annular channel 816
that permits the cool gas to flow proximal to and around the stator
to outlet 814. Annular channel 816 may be a ring of predetermined
depth and width that is built into stator housing 810. Further note
that gas may split as it enters inlet 812, with a portion of gas
passing through a first half of annular channel 816 and the
remaining half passing through a second half of annular channel
816. As the cool gas passes through annular channel 816, it may
absorb heat from stator 820 and other components associated with
electrical machine 860.
[0086] FIGS. 9A and 9B show three-dimensional views of a stator
jacket 930 and a jacket housing 950 that slips over stator jacket
930 to form the stator housing shown in FIG. 8 in accordance with
the principles of the present invention. FIG. 9A shows jacket 930
that fits over the wound stator core of the electrical machine.
Depending on the size of the inner diameter, stator jacket 930 may
fit flush against the stator core to maximize the heat exchange
efficiency of stator housing 810. Stator jacket 930 has a channel
920, which has a diameter less than the outer diameter of stator
jacket 930 and a predetermined width. Channel 920 forms annular
channel 816 (shown in FIG. 8) when stator jacket housing 950 of
FIG. 9B is positioned in place over stator jacket 930. O-ring
channels 922 and 924 may be provided in stator jacket 930 to
support, for example, an o-ring that provides a sealed fit when
jacket housing 950 is slid in place over stator jacket 930. With
such an airtight fit, gas may be forced to flow through annular
channel 816 from inlet port 912 to outlet port 914.
[0087] The stator housing shown in FIGS. 9A and 9B may protect the
wound stator core from potential problems that can result from
operating with high-pressure gas. In this arrangement, high
pressure gas may not be directly applied to the stator core because
stator jacket 910 prevents gas from coming into direct contact with
the stator laminations. Such protection may be necessary in
high-pressure applications to maintain the structural integrity of
the wound stator core. As is known in the art, stator cores are
laminated and wound together. Thus, there may be small air pockets
or channels existing between laminations that could allow air to
pass through. If sufficient air pressure is applied, these channels
or air pockets can expand, resulting in excess leakage and possible
damage to the laminated core and/or windings, thereby adversely
affecting the operating characteristics of the electrical
machine.
[0088] FIG. 10A-C shows several views of another stator housing
1000 that is in accordance with the principles of the present
invention. Stator housing 1000 may be a single piece construction
that may be cast and/or machined. FIG. 10A shows a
three-dimensional view of stator housing 1000. FIG. 10B shows a
cross-sectional view of stator housing 1000 taken along line B-B of
FIG. 10A and FIG. 10C shows a cross-sectional view of stator
housing 1000 taken along line C-C of FIG. 10A. Stator housing 1000
may have multiple annular channels 1020 for routing gas proximal to
the stator core. Axial manifolds 1022 and 1023 connect annular
channels 1020 to the input and output ports 1030 and 1034,
respectively. Thus, by way of example, gas entering inlet 1030 may
pass through manifold 1022, through annular channel 1020, through
manifold 1023, and then out of outlet 1034.
[0089] FIG. 11 shows a cross-sectional view similar to FIG. 10B
except it shows stator housing 1000 with stator winding 1140,
laminated stator core stack 1144, and pressure sleeve 1150
contained within housing 1000 in accordance with the principles of
the present invention. Pressure sleeve 1150 may be constructed to
fit flush against the outer diameter of laminated stator core 1144,
and functions to protect laminations 1144 and stator winding 1140
from high pressure gas being supplied to stator housing 1000. As
discussed above, it may be necessary to provide protection against
high pressures so that the high pressure gas does not leak through
the laminations. Thus, the combination of pressure sleeve 1150 and
housing 1000, with stator winding 1140 and laminated stator core
1144 may provide an airtight assembly. If desired, o-rings (not
shown) may be provided to further enhance the pressure integrity of
the assembly.
[0090] Persons skilled in the art will appreciate that the
illustrations shown in FIGS. 8-11 are not limiting and that
different configurations can be employed to route cool gas to the
electrical machine to draw heat away from the electrical machine.
For example, the annular channel may have spiral ribbing to induce
a spiral movement of gas through the stator housing. The inlet and
outlet ports may be positioned differently than that shown in FIGS.
8-11. For example, the inlet and outlet may be placed at opposite
ends of the housing (e.g., inlet is placed near the thrust-end
bearing side and the inlet is placed near the non thrust-end
bearing side of the turbine-generator combination).
[0091] FIGS. 12, 13, and 14 show simplified cross-sectional views
of other embodiments of stator housing in accordance with the
principals of the present invention. FIGS. 12A and 12B show two
different views of a stator housing 1200 having tubes or pipes 1220
soldered or brazed onto grooves (not shown) of stator jacket 1230.
Several pipes 1220 may be soldered or brazed circumferentially
about stator jacket 1230. An optional jacket housing 1250 may be
constructed to slide over pipes 1220. In this embodiment, tube or
pipe 1220 may extend parallel to the central axis 1260 of stator
housing 1200 for a predetermined distance, beginning at a first end
of housing 1200. At the end of the predetermined distance, tube
1220 returns to the first end of housing 1200. This send and return
path routing structure is apparent in FIG. 12A, where "x" indicates
that gas flows into tubes 1220 and ".circle-solid." indicates that
gas flows out of tubes 1220. This send and return routing structure
is also apparent in FIG. 12B, where the arrows indicate the flow of
gas from a first end to the opposite end and back to the first end
of stator housing 1200.
[0092] FIG. 13 shows a tube or piping structure for routing gas
that is similar to that shown in FIGS. 12A and 12B, but the gas may
be directed to flow from a first end of the stator housing to the
opposite end of stator housing 1300 in accordance with the
principles of the present invention. FIG. 13 shows that pipes 1320
are disposed circumferentially about the central axis (not shown)
of stator jacket 1330. A first end of pipes 1320 is connected to an
inlet manifold 1330 and a second but opposite end of pipe 1320 is
connected to an outlet manifold 1332. As shown, this configuration
routes gas from a first end to an opposite end of stator housing
1300. If desired, an optional jacket housing 1350 may be
constructed to slide over pipes 1320.
[0093] FIGS. 14A and 14B show yet another variation of a stator
housing according to the principles of the present invention.
Stator housing 1400 has axial flow channels 1420 that extend
parallel to the central axis of stator housing 1400. Axial flow
channels 1420 are built into stator jacket 1430. That is, stator
jacket 1430, itself, may be cast or machined to have groves that
form axial flow channels 1420 when jacket housing sleeve 1450 is
slid over stator jacket 1430. The inner diameter of housing sleeve
1450 is such that it fits flush against or proximate to the outer
diameter of stator jacket 1430. O-rings may be used in to increase
pressure capacity.
[0094] Manifolds (not shown) may be coupled to one or both ends of
stator jacket 1410, depending on how gas is being routed through
axial flow channels 1420. For example, only one manifold may be
used if gas is being routed in and out of the same end. Persons
skilled in the art will appreciate that if the single manifold
arrangement is used, a return path for re-routing the gas back to
the manifold is needed. Two manifolds, positioned on opposite ends,
may be used if gas is routed from a first end to a second end of
stator jacket 1410.
[0095] Persons skilled in the art will appreciate that other
arrangements of piping, tubing, and integral cast tubing (FIG. 14)
may be utilized. For example, the arrangements may have the tubing
wind around the stator jacket, as opposed to running lengthwise
along the stator jacket. Such tubing may take on irregular,
non-conventional forms that include patterns and/or random
distribution of tubing.
[0096] Thus it is seen that the same compressed gas being used to
drive a turbine can also be used to cool components and/or
subsystems of an electrical generation system. A person skilled in
the art will appreciate that the present invention can be practiced
by other than the described embodiments, which are presented for
purposes of illustration rather than of limitation, and the present
invention is limited only by the claims which follow.
* * * * *