U.S. patent application number 09/773369 was filed with the patent office on 2001-10-04 for cooling supply system for stage 3 bucket of a gas turbine.
This patent application is currently assigned to General Electric Company. Invention is credited to Burns, James Lee, Drlik, Gary Joseph, Eldrid, Sacheverel Quentin, Gibler, Edward Eugene, Leone, Sal Albert, Palmer, Gene David.
Application Number | 20010025476 09/773369 |
Document ID | / |
Family ID | 23124703 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010025476 |
Kind Code |
A1 |
Eldrid, Sacheverel Quentin ;
et al. |
October 4, 2001 |
Cooling supply system for stage 3 bucket of a gas turbine
Abstract
In a land based gas turbine including a compressor, a combustor
and turbine section including at least three stages, an improvement
comprising an inlet into a third stage nozzle from the compressor
for feeding cooling air from the compressor to the third stage
nozzle; at least one passageway running substantially radially
through each airfoil of the third stage nozzle and an associated
diaphragm, into an annular space between the rotor and the
diaphragm; and passageways communicating between the annular space
and individual buckets of the third stage.
Inventors: |
Eldrid, Sacheverel Quentin;
(Saratoga Springs, NY) ; Burns, James Lee;
(Schenectady, NY) ; Palmer, Gene David; (Clifton
Park, NY) ; Leone, Sal Albert; (Scotia, NY) ;
Drlik, Gary Joseph; (Fairfield, OH) ; Gibler, Edward
Eugene; (Cincinnati, OH) |
Correspondence
Address: |
Nixon & Vanderhye P.C.
8th Floor
1100 N. Glebe Rd.
Arlington
VA
22201
US
|
Assignee: |
General Electric Company
|
Family ID: |
23124703 |
Appl. No.: |
09/773369 |
Filed: |
February 1, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09773369 |
Feb 1, 2001 |
|
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|
09292445 |
Apr 15, 1999 |
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Current U.S.
Class: |
60/772 |
Current CPC
Class: |
Y02T 50/60 20130101;
F01D 5/088 20130101; F01D 9/065 20130101; Y02T 50/676 20130101;
Y02T 50/673 20130101 |
Class at
Publication: |
60/39.02 ;
60/39.75 |
International
Class: |
F02C 007/12 |
Claims
What is claimed is:
1. In a land based gas turbine comprising a compressor, a combustor
and turbine section including at least three stages, a cooling
circuit comprising: an inlet into a third stage nozzle from the
compressor for feeding cooling air from the compressor to the third
stage nozzle; at least one passageway running substantially
radially through each airfoil of said third stage nozzle and an
associated diaphragm, into an annular space between the rotor and
the diaphragm; and passageways communicating between said annular
space and individual buckets of said third stage.
2. The gas turbine of claim 1 wherein said at least one passageway
includes a portion in said diaphragm configured to feed said
cooling air into said annular space substantially tangent to the
rotor.
3. The gas turbine of claim 2 wherein said portion of said at least
one passageway contracts in the flow direction to accelerate the
cooling air as it enters said annular space.
4. The gas turbine of claim 2 wherein said portion of at least one
passageway in said diaphragm is provided in a part annular
labyrinth seal segment secured to said diaphragm and cooperating
with a corresponding seal on a rotor spacer wheel located radially
inwardly of said third stage nozzle.
5. The gas turbine of claim 4 wherein means are provided to
accommodate relative motion or mismatch between said portion of
said at least one passageway in said seal segment and said
diaphragm.
6. The gas turbine of claim 1 wherein said inlet to said third
stage nozzle includes a manifold external to a casing of said gas
turbine.
7. The gas turbine of claim 4 wherein said passageways
communicating between said annular space and said individual
buckets include plural sets of axial passages through said spacer
wheel.
8. The gas turbine of claim 1 wherein said third stage nozzle
includes a plurality of part annular segments, each segment having
two nozzle airfoils, and wherein said inlet includes a pipe feeding
cooling air to each segment, said pipe supplying cooling air to
each of said two nozzle airfoils.
9. The gas turbine of claim 1 wherein stages 1 and 2 are primarily
steam cooled.
10. The gas turbine of claim 4 including an annular seal between
said spacer wheel and said third stage buckets to prevent leakage
of cooling air passing into said third stage buckets.
11. A method of cooling one stage of a gas turbine comprising: a)
extracting cooling air from a turbine compressor; b) supplying
cooling air to a stationary nozzle adjacent said one stage of the
gas turbine; c) establishing a path for said cooling air from said
stationary nozzle to a plurality of buckets in said one turbine
stage; and d) flowing said cooling air radially outwardly through
said plurality of buckets and exhausting said cooling air from
radially outer tips of said buckets.
12. The method of claim 11 wherein during step c), said cooling air
is fed tangentially into an annular space surrounding a rotor of
said gas turbine.
13. The method of claim 12 wherein said cooling air is accelerated
into said annular space.
14. The method of claim 11 wherein said one turbine stage is a
third stage.
15. The method of claim 11 wherein said cooling air is supplied to
said stationary nozzle via a path outside said gas turbine.
16. In a land based gas turbine comprising a compressor, a
combustor and turbine section including at least three stages, a
cooling circuit comprising: means for supplying cooling air from a
gas turbine compressor to a stationary nozzle; and means for
establishing a cooling air flow path from said nozzle to individual
buckets of a turbine stage downstream and adjacent said stationary
nozzle.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to turbines,
particularly to land-based gas turbines for power generation,
employing compressor air for cooling the buckets of the third
turbine stage.
BACKGROUND OF THE INVENTION
[0002] Steam cooling of hot gas path components of a gas turbine
(for example, the buckets), has been proposed in the past and found
viable in land-based power generating plants. While gas turbines
are typically air cooled (for example, jet turbines employ
compressor discharge air for cooling the hot gas path components),
steam cooling is more efficient in that the losses associated with
the use of steam as a coolant are not as great as the losses
realized by extracting compressor bleed air for cooling. In land
based gas turbines and especially those in combined cycle systems,
steam cooling is particularly advantageous because the heat energy
imparted to the steam as it cools the gas turbine components is
recovered as useful work in driving the steam turbine in the
combined cycle operation. However, while steam is preferred for
cooling the first and second turbine stages, air is required to
cool this third stage bucket, and (optionally) to purge the aft
portion of the turbine rotor.
BRIEF SUMMARY OF THE INVENTION
[0003] In accordance with this invention, air is extracted from the
twelfth stage of the compressor and is carried through extraction
piping outside the gas turbine, and then supplied through the
turbine shell to the stage 3 nozzle. In order to reduce the cycle
performance penalty of cooling the third stage bucket, relatively
low pressure twelfth stage air is used. The traditional method of
bringing air flow from the machine center line practiced by the
assignor of this invention is not possible as the forward wheel
cavities require high pressure air to drive their purge circuits.
Even with steam cooling of the first two bucket stages, air is
required to bathe the turbine wheels to control their temperature
during transient and start-up operations. In other words, since the
forward rotor cavities are filled with high pressure air, a new
technique had to be devised for supplying low pressure compressor
extraction air for air cooling the third stage. As a result, the
bucket cooling air is supplied radially inwardly through the
adjacent stator structure, i.e., the third stage nozzle, and then
routed to the third stage bucket. In addition, access to relatively
low pressure air also provides an optional air source for purge
flow in the aft portion of the turbine rotor, with reduced cycle
performance penalty. Thus, the invention seeks to introduce low
pressure extraction air to the turbine rotor at a low temperature
relative to the rotor for use in cooling the third stage bucket.
The invention also provides at least an option to make use of the
above mentioned air flow to purge the aft section of the turbine
rotor, but this is not a preferred arrangement.
[0004] In accordance with the invention, a nozzle inducer system
comprises a system of tubes carrying the compressor extraction air
from the turbine shell through the nozzle airfoils and into the
nozzle diaphragm. At the outer end, this tube system penetrates the
turbine shell at twenty-two circumferential locations in the
exemplary embodiment. Once inside the turbine shell, the piping is
split into two conduits, thereby introducing air into forty-four
nozzle vanes or airfoils. At the radially inner end of each nozzle
vane, the air enters a passage in a diaphragm seal segment which
directs the cooling air tangentially into a cavity surrounding the
rotor. This passage is configured to accelerate the air in the
direction of wheel rotation into this circumferential open area so
as to substantially match the tangential velocity of the rotor
spacer wheel located radially inwardly of the nozzle. The air is
then fed into discrete sets of axial pipes which deliver the air to
the shank passages of the stage three buckets. The air then flows
radially outwardly through internal passages in the buckets and
exits at the bucket tips, into the hot combustion gas path.
[0005] The air delivery system in accordance with the invention has
several advantages. For example, the use of separate tubing for
rotor delivery air minimizes heat transfer to the air from the hot
nozzle airfoils. It also allows the use of lower pressure air to
pressurize the outer side wall cavities and nozzle cooling circuits
which reduces parasitic leakage, improving machine efficiency. In
addition, due to the reduction in relative velocity between the
rotor spacer wheel and the air, and the drop in air static
temperature due to its tangential acceleration, a significantly
lower temperature is available for bucket cooling compared to a
design where air is simply fed radially into the rotor area.
[0006] Accordingly, in its broader aspects, the present invention
relates to a land based gas turbine comprising a compressor, a
combustor and at least three turbine stages fixed to a rotor, and
specifically to an improvement which includes an air cooling
circuit for the third turbine stage comprising an inlet into a
third stage nozzle from a compressor for feeding cooling air from
the compressor to the third stage nozzle; at least one passageway
running substantially radially through each airfoil of the third
stage nozzle and an associated diaphragm, into an annular space
between the rotor and the diaphragm; and passageways communicating
between the annular space and individual buckets of the third
stage.
[0007] The present invention also relates to a method of cooling
one stage of a gas turbine comprising a) extracting cooling air
from a turbine compressor; b) supplying cooling air to a stationary
nozzle adjacent the one stage of the gas turbine; c) establishing a
path for the cooling air from the stationary nozzle to a plurality
of buckets in the one turbine stage; and d) flowing the cooling air
radially outwardly through the plurality of buckets and exhausting
the cooling air from radially outer tips of the buckets.
[0008] Additional features of the subject invention will become
apparent from the detailed description which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a fragmentary longitudinal cross sectional view of
a turbine section of a gas turbine, illustrating the environment of
the present invention;
[0010] FIG. 2 is a simplified enlarged detail illustrating the air
flow inlet to the third stage nozzle and air flow outlet from a
third stage bucket in accordance with this invention;
[0011] FIG. 3 simplified cross section illustrating the cooling air
flow path from the third stage nozzle to the shank portion of a
third stage bucket in accordance with the invention;
[0012] FIG. 4 is a cross section illustrating the axial cooling
passages in the stage 2-3 spacer;
[0013] FIG. 5 is a section taken along the line 5-5 of FIG. 4;
[0014] FIG. 6 is a simplified end view of the third stage nozzle
and diaphragm illustrating the cooling air flow path in a pair of
adjacent nozzle airfoils; and
[0015] FIG. 7 is an enlarged detail of the tangential cooling air
flow passages at the base of the seal segments mounted in the third
stage nozzle diaphragm.
DETAILED DESCRIPTION OF THE INVENTION
[0016] With reference to FIG. 1, the turbine section 10 of a gas
turbine is partially illustrated. At the outset, it should be
appreciated that the gas turbine of this invention is
advantageously utilized in a combined cycle system in which the
exhaust gases exiting the gas turbine enter a heat recovery steam
generator in which water is converted to steam in the manner of a
boiler. Steam thus produced drives one or more steam turbines in
which additional work is extracted to drive an additional load,
such as a second generator, which, in turn, produces additional
electric power.
[0017] The turbine section 10 of the gas turbine is downstream of
the turbine combustor 11 and includes a rotor, generally designated
R, with four successive stages comprising turbine wheels 12, 14, 16
and 18 mounted to and forming part of the rotor shaft assembly for
rotation therewith. Each wheel carries a row of buckets B1, B2, B3
and B4, the blades of which project radially outwardly into the hot
combustion gas path of the turbine. The buckets are arranged
alternately between fixed nozzles N1, N2, N3 and N4. Alternately,
between the turbine wheels from forward to aft are spacers 20, 22
and 24, each located radially inwardly of a respective nozzle. An
aft disk 26 forms an integral part of the aft shaft 28 on the aft
side of the last stage turbine wheel 18. It will be appreciated
that the wheels and spacers are secured to one another by a
plurality of circumferentially spaced axially extending bolts 30
(one shown), as in conventional gas turbine construction.
[0018] While not per se part of the present invention, a bore tube
assembly 32 forms part of the rotor R and rotates with the rotor
about the rotor axis A. The bore tube assembly includes outer and
inner tubes 34 and 36 defining annular steam cooling supply passage
38 and spent stream return passage 40. These passages communicate
steam to and from the outer rim of the rotor through sets of radial
conduits 42, 44 and axially extending conduits (one shown at 46)
circumferentially spaced about the rotor rim for supplying cooling
steam to the first and second stage buckets B1 and B2. Return or
spent cooling steam flows through similar axially and radially
extending conduits, respectively, for flow coaxially from the rotor
bore via return passage 40. The steam cooling circuit per se,
however, forms no part of this invention.
[0019] In the exemplary embodiment of this invention, the third
stage nozzle N3 includes twenty-two part annular segments 48 (see
FIG. 6), each having two stationary vanes or airfoils 50, 52. An
air manifold 54 outside the turbine shell is designed to supply air
from compressor 55 to twenty-two individual pipes (one shown at 56)
which penetrate the turbine shell and which are connected to the
twenty-two respective segments. For simplicity, the compressor 55
and manifold 54 are shown schematically in FIG. 2. Inside the
shell, the pipe 56 feeds two supply pipes 58, 58a, etc. for each of
the forty-four vanes or airfoils (see FIG. 6). Pipes 58, 58a are
connected by flexible connector couplings shown at 59. For
convenience, only one flow circuit need be described in detail.
[0020] With specific reference to FIGS. 2, 3 and 6, a passage or
conduit 60 is shown extending radially within the vane or airfoil
50, with a generally radially extending, flexible coupling or
connector 62 (incorporating a carbon bushing, not shown) carrying
the air within the diaphragm 64. At its radially inner end, the
connector is operatively connected to a diaphragm insert 66 by
means of a spoolie device 68. The latter, having generally
spherically shaped opposite ends, in combination with the flexible
coupling 62, accommodate any relative movement between the insert
66 and the diaphragm 64. As is well known, the diaphragm inserts 66
comprise a plurality of part annular segments extending
circumferentially about the rotor, with labyrinth seals 70 engaged
with cooperating seals 72 on the rotor spacer wheel 22 to prevent
leakage of air along the rotor.
[0021] Within the insert 66, the air passage changes direction via
elbow passage 70 and substantially straight passage 72 to direct
the air tangentially (at an angle .alpha. of about 22-23.degree.)
into an annular rotor cavity 74, as best seen in FIGS. 6 and 7.
Passage 70 tapers in the flow direction through an elbow portion to
a smaller diameter at passage 72, thereby causing acceleration of
the cooling air as it is fed into the annular cavity 74. As a
result of this inducer arrangement, the air as supplied to cavity
74 is relatively "still" vis-a-vis the rotor. In other words, the
air is fed tangentially at a speed substantially the same as the
rotational speed of the rotor. This results in cooler air being
available for the third stage buckets, due to the reduction in
relative velocity between the rotor spacer wheel and the air, and
the drop in air static temperature due to its tangential
acceleration.
[0022] From the annular rotor cavity 74, the cooling air moves
axially through multiple sets of three passages 76 each (see FIGS.
3, 4 and especially 5), with access to the passages permitted by
forming the spacer wheel 22 with scalloped areas 78 about its
periphery as best seen in FIG. 5.
[0023] Note in this regard that the individual sets of passages 76
are located circumferentially between axial steam supply and return
passages 46 and radially outwardly of bores 80 (one shown) for
bolts 30.
[0024] The air then moves radially outwardly at the interface of
spacer 22 and the third stage wheel 16, to an axial supply passage
82 between the wheel rim and the bucket shank. From here, the air
travels radially outwardly in one or more radial passages 86, and
then vents into the hot gas path at the bucket tips (see the flow
arrows in FIGS. 1 and 2). In order to prevent leakage of cooling
air between the spacer 22 and wheel 16, an annular wire seal 86 is
located within a groove formed in the radially outermost edge of
spacer 22. Since the wheel 16 and spacer 22 are rotating together
with the rotor, there is no relative frictional movement between
the seal 86 and the wheel 16.
[0025] While the invention as described relates to air cooling in
land based turbines, it can be applied to aircraft turbines as
well.
[0026] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiment, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *