U.S. patent application number 09/768220 was filed with the patent office on 2001-09-06 for gas turbine bucket with impingement cooled platform.
This patent application is currently assigned to General Electric Company. Invention is credited to Jones, Raphael Durand.
Application Number | 20010019696 09/768220 |
Document ID | / |
Family ID | 23600216 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019696 |
Kind Code |
A1 |
Jones, Raphael Durand |
September 6, 2001 |
Gas turbine bucket with impingement cooled platform
Abstract
In a turbine bucket having an airfoil portion and a root
portion, with a substantially planar platform at an interface
between the airfoil portion and root portion, a platform cooling
arrangement including at least one bore in the root portion and at
least one impingement cooling tube seated in the bore, the tube
extending beyond the bore with an outlet in close proximity to a
targeted area on an underside of the platform.
Inventors: |
Jones, Raphael Durand;
(Guilderland, NY) |
Correspondence
Address: |
Nixon & Vanderhye P.C.
1100 N. Glebe Rd., 8th Floor
Arlington
VA
22201
US
|
Assignee: |
General Electric Company
|
Family ID: |
23600216 |
Appl. No.: |
09/768220 |
Filed: |
January 24, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09768220 |
Jan 24, 2001 |
|
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09404589 |
Sep 24, 1999 |
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Current U.S.
Class: |
416/1 ; 416/193A;
416/241R; 416/97R |
Current CPC
Class: |
F05D 2240/81 20130101;
F01D 5/08 20130101; Y02T 50/60 20130101; F01D 5/187 20130101; F01D
25/12 20130101 |
Class at
Publication: |
416/1 ;
416/97.00R; 416/193.00A; 416/241.00R |
International
Class: |
F01D 005/18 |
Claims
What is claimed is:
1. In a turbine bucket having an airfoil portion and a root
portion, with a substantially planar platform at an interface
between the airfoil portion and root portion, a platform cooling
arrangement comprising: at least one bore in said root portion and
at least one impingement cooling tube seated in said at least one
bore, said tube extending beyond said bore with an outlet in close
proximity to a targeted area on an underside of said platform.
2. The bucket of claim 1 wherein said targeted area lies within a
recess under said platform, and proximate a leading edge fillet of
said airfoil portion.
3. The bucket of claim 2 wherein said platform is provided with a
plurality of film cooling holes communicating with said recess.
4. The bucket of claim 3 wherein said plurality of film cooling
holes are located closer to a trailing edge of said airfoil portion
than to the leading edge of said airfoil portion.
5. The bucket of claim 1 wherein the underside of said platform is
coated with a rough coat material.
6. The bucket of claim 4 wherein said impingement cooling tube and
said plurality of film cooling holes are located on a pressure side
of said airfoil portion.
7. The bucket of claim 3 wherein said film cooling holes are
directionally oriented to cause cooling air to flow in a path
generally toward said trailing edge of said airfoil portion.
8. The bucket of claim 1 wherein said impingement cooling tube is
flared at its rearward end to limit forward insertion into said
bore.
9. The bucket of claim 1 wherein said impingement cooling tube is
secured within said bore so as to prevent movement in a direction
away from said platform.
10. In a turbine bucket having an airfoil portion and a root
portion, with a substantially planar platform at an interface
between the airfoil portion and root portion, a platform cooling
arrangement comprising: means for impingement cooling a targeted
area on an underside of said platform.
11. A method of cooling a leading edge fillet region of a turbine
bucket having an airfoil portion and a root portion, said airfoil
portion joined to a platform extending over said root portion,
comprising: a) providing a through bore in a leading side of a
cover plate in said root portion, said bore communicating with a
recess in said root portion underlying said airfoil portion; b)
inserting a tube in said bore, with a tip of the tube extending
beyond said bore and in close proximity to a targeted area on an
underside of said platform; c) supplying cooling air to said recess
via said tube such that said targeted area is impingement cooled by
said cooling air passing through said tube.
12. The method of claim 11 wherein said targeted area is an area in
said recess substantially directly beneath the leading edge fillet
of said airfoil portion.
13. The method of claim 11 including providing film cooling holes
to allow said cooling air to escape from said recess.
14. The method of claim 11 wherein said film cooling holes are
located in said platform.
15. The method of claim 14 wherein said impingement cooling tube
and said film cooling holes are on a pressure side of said airfoil
portion.
16. The method of claim 15 wherein said film cooling holes are
directionally oriented to cause cooling air to flow in a path
generally toward said trailing edge of said airfoil portion.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to the cooling of turbine buckets
and, specifically, to the cooling of the platform region of the
bucket, at the base of the airfoil.
BRIEF SUMMARY OF THE INVENTION
[0002] Stage one and stage two buckets in gas turbines experience
high temperatures and stress, creating low cycle fatigue life
concerns, particularly at the leading edge fillet where the airfoil
joins the platform at the forward portion of the pressure side of
the airfoil.
[0003] In aircraft engines, the bucket platforms are cooled by air
entering the cavity below the platform, but this arrangement is not
completely satisfactory, particularly in connection with the
leading edge fillet.
[0004] This invention provides a unique solution to the above
problem by directing cooling air through a tube, the forward end of
which is located closely adjacent the underside of the platform,
below the forward portion of the pressure side of the airfoil, so
as to effectively impingement cool the platform in the localized
region below the leading edge fillet.
[0005] In addition, film cooling holes are formed in the platform
itself so that air introduced into the cavity by the impingement
cooling tube can escape the cavity and flow along the upper surface
of the platform along the contour of the pressure side of the
airfoil, in a direction toward the trailing edge of the
airfoil.
[0006] In its broader aspects, the invention relates to a turbine
bucket having an airfoil portion and a root portion, with a
substantially planar platform at an interface between the airfoil
portion and root portion, a platform cooling arrangement comprising
at least one bore in the root portion and at least one impingement
cooling tube seated in the bore, the tube extending beyond the bore
with an outlet in close proximity to a targeted area on an
underside of the platform.
[0007] In another aspect, the invention relates to a method of
cooling a leading edge fillet region of a turbine bucket having an
airfoil portion and a root portion, the airfoil portion joined to a
platform extending over the root portion, comprising: a) providing
a through bore in a leading side of a cover plate in the root
portion, the bore communicating with a recess in the root portion
underlying the airfoil portion; b) inserting a tube in the bore,
with a tip of the tube extending beyond the bore and in close
proximity to a targeted area on an underside of the platform; c)
supplying cooling air to the recess via the tube such that the
targeted area is impingement cooled by the cooling air passing
through the tube.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a partial side cross section of a bucket in
accordance with the invention;
[0009] FIG. 2 is a partial end view of a lower dovetail portion (of
the leading side edge) of the bucket not entirely shown in FIG. 1;
and
[0010] FIG. 3 is a top plan view of the bucket in accordance with
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0011] With reference to FIGS. 1-3, a turbine bucket 10 includes an
airfoil portion 12 extending vertically upwardly from a horizontal,
substantially planar platform 14. The airfoil portion has a leading
edge 15 and a trailing edge 17. Below the platform 14, there are
two pair of so-called "angel wings" 16, 18 extending in opposite
directions from the leading and trailing sides 20, 22 of the cover
plate 24 in the root portion of the bucket. The platform 14 is
joined with the cover plate 24. Below the root portion, there is a
dovetail 26 by which the bucket is secured to a turbine wheel (in a
preferred embodiment, the stage 1 or stage 2 wheels of a gas
turbine).
[0012] Cooling passages (not shown) extend in radially outward and
inward directions in a serpentine path through the airfoil portion,
the path having passages in the root portion communicating with
supply and return passages 28, 30 in the dovetail. The internal
airfoil cooling circuit forms no part of the invention, however,
and is therefore not shown in detail. Of significance here is the
substantially hollow space or recess 32 in the root portion, above
the dovetail 26 but below the platform 14, defined further by the
sides 20, 22 of the cover plate. This recess is generally on the
pressure side 34 of the airfoil, and it will be appreciated from
FIG. 3 that a relatively large portion of the platform 14 on the
pressure side 34 of the airfoil overlies the hollow space or recess
32.
[0013] An angled hole 36 is drilled through the leading side 20 of
the cover plate 24 from the lower end of the root portion, on the
external side thereof, extending upwardly (i.e., substantially
radially) and opening into the recess 32. Due to the angled
orientation, the hole 36 has an exit profile on the interior of the
root wall 38 which is elliptical in shape as shown in FIG. 2. An
impingement cooling tube 40 is pressed into the hole 36 from under
the root portion, so that an outlet at the upper end or tip 42 of
the tube is located close to the underside of the platform, and
close to a targeted area along the leading edge fillet 44 where the
airfoil joins the platform.
[0014] The lower end of the tube 40 is flared at 46 to limit the
extent of insertion, and the tube may be fixed in place by a spot
weld at 47 to prevent the tube from sliding back through the hole
in a direction opposite the assembly direction. Preferably, the
tube end 42 is within about 0.5" from the underside of the
platform.
[0015] Since the lower edge of the cover plate 24 will seat on the
wheel surface, thus blocking the hole 36, a second hole 48 is
drilled from the leading side 20 of the cover plate 24 so as to
intersect with the hole 36, just below the lower end of the tube
40. In this way, rotor or wheel space purge air can enter the tube
40 via hole 36.
[0016] In addition, an array of film cooling holes 50 extend
through the platform 14 from the recess 32 to a location on the
external side of the platform.
[0017] With the above arrangement, purge air from wheel space below
the bucket will enter the hole 48 and flow through the tube 40 so
as to impinge directly on the underside of the platform 14, below
but proximate the leading edge fillet 44. The underside of the
platform 14 is thus impingement cooled in the leading edge fillet
area to reduce stress and improve low cycle fatigue margins. Of
course, the enhancement of heat transfer in this specific region
continues along the platform and at least partially under the
airfoil itself.
[0018] Another feature of the invention lies in the combination of
the above described impingement cooling with film cooling along the
upper surface of the platform. This is achieved by utilizing the
array of film cooling holes 50 in the platform, allowing the
cooling air in the hollow space 32 to exit along the top surface of
the platform. The film cooling holes 50 are directionally oriented
so that the cooling air merges with the gas path air and flows
along the pressure side of the airfoil toward the trailing edge 17.
The flowpath of the film cooling air is such that it can carry over
to the suction side of the platform of the adjacent bucket,
increasing the overall effectiveness of the system.
[0019] To further enhance heat transfer, the underside of the
platform 14 can be provided with any suitable rough coat, thus
increasing the surface area available for heat transfer. In
addition, one or more additional impingement cooling tubes may be
used in conjunction with the tube 40 to enhance heat transfer at
targeted locations along the underside of the platform.
[0020] 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.
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