U.S. patent application number 13/553151 was filed with the patent office on 2014-01-23 for cooled turbine blade tip shroud with film/purge holes.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is Anthony Louis Giglio, Michael J. Kline. Invention is credited to Anthony Louis Giglio, Michael J. Kline.
Application Number | 20140023497 13/553151 |
Document ID | / |
Family ID | 49946691 |
Filed Date | 2014-01-23 |
United States Patent
Application |
20140023497 |
Kind Code |
A1 |
Giglio; Anthony Louis ; et
al. |
January 23, 2014 |
COOLED TURBINE BLADE TIP SHROUD WITH FILM/PURGE HOLES
Abstract
A cooled turbine blade shroud with purge holes located proximate
regions of the tip shroud cooling cavity that experience cooling
air flow recirculation or stagnation. The purge holes may be
oriented radially from the cooling cavity to a surface, such as the
outer top surface and/or inner/bottom surface, of the tip shroud,
and may provide improved heat transfer and consequent cooling and
enhanced tip shroud life.
Inventors: |
Giglio; Anthony Louis;
(Simpsonville, SC) ; Kline; Michael J.; (Marietta,
GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Giglio; Anthony Louis
Kline; Michael J. |
Simpsonville
Marietta |
SC
GA |
US
US |
|
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
49946691 |
Appl. No.: |
13/553151 |
Filed: |
July 19, 2012 |
Current U.S.
Class: |
416/1 ;
416/97R |
Current CPC
Class: |
F05D 2260/202 20130101;
F01D 5/225 20130101 |
Class at
Publication: |
416/1 ;
416/97.R |
International
Class: |
F01D 5/18 20060101
F01D005/18 |
Claims
1. A turbine blade comprising: a blade attachment portion; a
radially extended turbine airfoil integral with said blade
attachment portion, said turbine airfoil comprising one or more
internal cooling passages; a tip shroud proximate a top portion of
said turbine airfoil, said tip shroud comprising an internal
cooling cavity in communication with said one or more internal
cooling passages, said internal cooling cavity comprising at least
one high velocity region and at least one low velocity region, said
at least one high velocity region and at least one low velocity
region configured to pass cooling air therethrough; at least one
exit port in communication with said internal cooling cavity
configured to exhaust spent cooling air from said at least one high
velocity region; and at least one purge hole in communication with
said internal cooling cavity configured to exhaust spent cooling
air from said at least one low velocity region.
2. The turbine blade of claim 1 wherein said at least one exit port
exits through a shroud edge of said tip shroud.
3. The turbine blade of claim 1 wherein said at least one purge
hole exits through an outer top surface and/or bottom surface of
said tip shroud.
4. The turbine blade of claim 1 comprising a plurality of said at
least one low velocity regions and at least one of said at least
one purge hole in communication with each said at least one low
velocity region and an outer top surface and/or inner surface of
said tip shroud.
5. The turbine blade of claim 4 comprising a plurality of said at
least one high velocity regions and at least one said at least one
exit port in communication with each said at least one high
velocity region.
6. The turbine blade of claim 5 wherein each said purge hole exits
through an outer top portion and/or bottom portion of said tip
shroud and each said at least one exit port exits through a shroud
edge of said tip shroud.
7. A method comprising: providing a turbine blade comprising a
radially extended turbine airfoil comprising one or more internal
cooling passages; providing a tip shroud affixed to a top portion
of said airfoil, said tip shroud comprising an internal cooling
cavity in communication with said one or more internal cooling
passages, said internal cooling cavity comprising at least one high
velocity region and at least one low velocity region, both said at
least one high velocity region and at least one low velocity region
configured to pass cooling air therethrough; passing cooling air
through said one or more internal cooling passages and said
internal cooling cavity; exhausting spent cooling air through at
least one exit port in communication with said at least one high
velocity region; and exhausting spent cooling air through at least
one purge hole in communication with said at least one low velocity
region.
8. The method of claim 7 wherein exhausting spent cooling air
through said at least one exit port further comprises exhausting
said spent cooling air through an exit of said at least one exit
port on a shroud edge of said tip shroud.
9. The method of claim 7 wherein exhausting spent cooling air
through said at least one purge hole further comprises exhausting
said spent cooling air through an exit of said at least one purge
hole on an outer top surface and/or inner surface of said tip
shroud.
10. The method of claim 7 further comprising providing a plurality
of said at least one low velocity regions and further providing at
least one said purge hole in communication with each said at least
one low velocity region and an outer top surface and/or inner
surface of said tip shroud.
11. The method of claim 10 further comprising providing a plurality
of said at least one high velocity regions and at least one of said
at least one exit port in communication with each said at least one
high velocity region.
12. The method of claim 11 further comprising exhausting spent
cooling air from an exit of each said at least one purge hole
through a top portion and/or bottom portion of said tip shroud and
exhausting said cooling air from an exit of each said at least one
exit port through a shroud edge of said tip shroud.
13. A tip shroud configured for being disposed at a tip portion of
an airfoil, comprising an internal cooling cavity, said internal
cooling cavity comprising a plurality of high flow velocity regions
and a plurality of low flow velocity regions, each of said
plurality of low flow velocity regions configured to pass cooling
air therethrough; at least one exit port in communication with each
said at least one of the plurality of high flow velocity regions
configured to exhaust spent cooling air therefrom to a side edge of
said tip shroud; and at least one purge hole in communication with
each said at least one low flow velocity region configured to
exhaust spent cooling air therefrom to an outer top surface and/or
bottom surface of said tip shroud.
14. The tip shroud of claim 13 wherein at least one of said
plurality of low flow velocity regions is substantially elongated,
and comprises a plurality of said at least one purge hole disposed
therealong.
15. The tip shroud of claim 14 wherein said at least one purge hole
are disposed substantially linearly along said plurality of low
flow velocity regions.
16. The tip shroud of claim 15 wherein said at least one purge hole
is disposed substantially along a line substantially bisecting a
width of said plurality of low flow velocity regions.
17. The tip shroud of claim 13 wherein at least one of said
plurality of low flow velocity regions comprises a narrow end
transitioning to a wider opposing end.
18. The tip shroud of claim 17 comprising a plurality of said at
least one purge hole wherein said at least one purge hole increase
in size from said narrow end to said wider opposing end.
19. The tip shroud of claim 17 wherein said at least one purge hole
decreases in relative spacing from said narrow end to said wider
opposing end.
20. The tip shroud of claim 13 wherein at least one of said
plurality of low flow velocity regions includes a plurality of said
at least one purge hole disposed in a matrix configuration.
Description
TECHNICAL FIELD
[0001] The subject matter disclosed herein relates generally to gas
turbine engines, and, more specifically, to a gas turbine engine
rotor blade having improved tip cooling, and more specifically to a
turbine blade having a cooled tip shroud.
BACKGROUND OF THE INVENTION
[0002] A gas turbine engine includes one or more turbine blade
rows, or stages, each row or stage having buckets or blades which
project radially outwardly into the hot combustion gas path of the
turbine, and disposed downstream of the combustor, which stages
extract energy from the combustion gases generated by the
combustor. Disposed radially outwardly of the rotor blade tips may
be a stator shroud which is spaced from the blade tips to provide a
relatively small clearance between the blade tips and shroud for
reducing leakage of the combustion gases over the blade tips during
operation. Each of the rotor blades includes conventionally known
pressure and suction sides which are preferentially aerodynamically
contoured for extracting as much energy as possible from the
combustion gases flowing over the rotor blades. The pressure and
suction sides extend to the blade tip and are disposed as close as
possible to the stator shroud for maximizing the amount of energy
extracted from the combustion gases. The clearance gap, however,
between the blade tips and the stator shroud must nevertheless be
adequate to minimize the occurrence of blade tip rubs during
operation, which may damage the blade tips.
[0003] The efficiency of the turbine assembly is limited in part by
"spillover:" the escape of hot combustion gases through the
clearance gap between the turbine blade and the wall of the turbine
assembly, which is commonly referred to as the turbine shroud. To
reduce spillover, it is a common practice in the art to provide a
tip shroud on the end of the airfoil opposite the end attached to
the rotating shaft. The tip shroud includes a shelf and,
optionally, one or more blade teeth that reduces spillover by
decreasing the size of the clearance gap and interrupting the hot
gas path around the end of the turbine blade.
[0004] Tip shrouds are subject to creep damage due to the
combination of high temperature and centrifugally induced bending
stresses. The creep is usually manifested by the formation of "dog
ears" along unsupported edges of the shelf formed by the tip
shroud. "Dog ears" as used herein, means the folding or degrading
of the metal edges of the shelf formed by the tip shroud. Because
it has been generally found that reinforcing the shelf simply
transfers the stress from tip shroud to the root of the airfoil,
the approach to reducing creep in this region of the turbine blade
has been to "scallop" i.e., remove unsupported portions of the
shelf. Scalloping, however, leads to increased hot gas path leakage
past the turbine blade. If the tip shroud and shelf could be
adequately cooled, the need to scallop the shelf could be
substantially reduced. Consequently spillover would also be reduced
and turbine efficiency could be improved.
[0005] One approach to cooling the tip shroud involves providing in
the shroud tip an internal cooling cavity defining primary cooling
flow passages through which cooling air flows and exits proximate
the tip shroud edges (i.e. slashface). Inherent in such internal
cooling cavities, however, are regions which are susceptible to
flow recirculation or stagnation, which can cause localized hot
spots in that region of the tip shroud.
BRIEF DESCRIPTION OF THE INVENTION
[0006] These and other features of the present disclosure will
become apparent to one of ordinary skill in the art upon review of
the following detailed description when taken in conjunction with
the drawings and the appended claims.
[0007] According to one embodiment of the disclosure, there is
provided a turbine blade comprising a blade attachment portion; a
radially extended turbine airfoil integral with the blade
attachment portion, the turbine airfoil comprising one or more
internal cooling passages; a tip shroud affixed to a top portion of
the airfoil, the tip shroud comprising an internal cooling cavity
in communication with the one or more internal cooling passages,
the internal cooling cavity comprising at least one high velocity
region and at least one low velocity region, the regions configured
to pass cooling air therethrough; at least one exit port in
communication with the internal cooling cavity configured to
exhaust spent cooling air from the at least one high velocity
region; and at least one purge hole in communication with the
internal cooling cavity configured to exhaust spent cooling air
from the at least one low velocity region.
[0008] According to another embodiment of the disclosure, there is
provided a method of cooling a turbine blade shroud tip comprising
providing a turbine blade comprising a radially extended turbine
airfoil comprising one or more internal cooling passages; providing
a tip shroud affixed to a top portion of the airfoil, the tip
shroud comprising an internal cooling cavity in communication with
the one or more internal cooling passages, the internal cooling
cavity comprising at least one high velocity region and at least
one low velocity region; passing cooling air through the one or
more internal cooling passages and the internal cooling cavity;
exhausting spent cooling air through at least one exit port in
communication with the at least one high velocity region; and
exhausting spent cooling air through at least one purge hole in
communication with the at least one low velocity region.
[0009] According to another embodiment of the invention, there is
provided a tip shroud configured for being disposed at the tip
portion of an airfoil, comprising an internal cooling cavity, the
internal cooling cavity comprising a plurality of high flow
velocity regions and a plurality of low flow velocity regions, the
regions configured to pass cooling air therethrough; at least one
exit port in communication with each high flow velocity region
configured to exhaust spent cooling air therefrom to a side edge of
the tip shroud; and at least one purge hole in communication with
each low flow velocity region configured to exhaust spent cooling
air therefrom to a top or bottom surface of the tip shroud.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an isometric view of an embodiment of the
disclosure.
[0011] FIG. 2 is an isometric plan view of a portion of a tip
shroud of the disclosure.
[0012] FIG. 3 is an isometric plan view of a portion of a tip
shroud of the disclosure.
[0013] FIG. 4 is a cross sectional view of the embodiment of FIG. 1
taken along lines E-E.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0014] Referring now to FIGS. 1 and 4, there is illustrated a
turbine blade or airfoil, 10, with an associated radially outer tip
shroud 12. The airfoil 10 may have an inboard, or pressure side
face 11, and an outboard, or suction side face 13. The airfoil 10
may further include a first set of internal, radially extending
cooling channels generally designated as 14 along and proximate the
leading edge 16 of the airfoil 10. Similarly, a second set of
internal radially extending cooling channels generally designated
18 may be arranged along and proximate the airfoil trailing edge
20. Both sets of cooling channels 14, 18 may extend radially
outwardly into the tip shroud 12 and, specifically, pass cooling
air represented by the arrows D to a common, relatively large but
shallow chamber, plenum, or internal tip shroud cavity 22, which
may serve as an internal cooling chamber for the tip shroud 12.
[0015] As illustrated in FIGS. 1, 2 and 4, the internal tip shroud
cavity 22 may comprise a central plenum 23 flowably connected to a
number of interconnected primary cooling cavities 24 by a number of
connecting passages 26. As illustrated, the interconnected primary
cooling cavities 24 may comprise a substantially serpentine
configuration, and may comprise one set of interconnected primary
cooling cavities 24 disposed outwardly relative to the inboard face
11 of the airfoil 10, and another set of interconnected primary
cooling cavities 24 disposed outwardly relative to the outboard
face 13 of the airfoil 10.
[0016] The internal tip shroud cavity 22 may be of conventional
design, for example, as illustrated and described in Brittingham,
et al., U.S. Publication No. US2008/0170946A1. The internal tip
shroud cavity 22 may extend across the tip shroud 12 substantially
from front to back and side to side, within the plane of the tip
shroud 12. As illustrated in FIG. 2, the tip shroud cavity 22 may
be supported in the spaces 17 by one or more ribs (not shown),
represented by the bold boundary line 19. These ribs may be of
conventional design, and may, in addition to defining the
interconnected primary cooling cavities 24, assist in supporting
the bottom and top sides of the tip shroud 12. Such structural
support may be critical to tip shroud life, as the tip shroud 12
may be heavily stressed due to rotational forces and thermal
stresses.
[0017] The internal tip shroud cavity 22 may be created in the tip
shroud 12 by a ceramic core and formed during the investment
casting process. This core may be held in place by one or more tabs
extending out the edges 28 of the tip shroud 12. Spent cooling air
may exit into the hot gas path from the interconnected primary
cooling cavities through exit channels 30 that lead to exit holes
32 in the tip shroud edges or slash face 28.
[0018] As further illustrated in FIG. 2, the internal tip shroud
cavity 22 may include high flow velocity regions 25, the boundaries
of which, in exemplary fashion, are represented by the dotted
boundary line 27. The internal tip shroud cavity 22 may further
include low flow velocity regions 34, the boundaries of which, in
exemplary fashion, are represented by the dotted boundary line 35
in FIGS. 2 and 4. As illustrated In FIG. 2, the low flow velocity
regions 34 may be elongated and/or may include a narrower end
region 42 that may transition to a relatively wider opposing end
region 44, although other configurations for both the high flow
velocity regions 25 and low flow velocity regions 34 are possible
depending upon tip shroud cavity geometry.
[0019] It is believed that cooling air flows through the internal
tip shroud cavity 22 at a higher velocity in high flow velocity
regions 25, than through low flow velocity regions 34, in part
because such high flow velocity regions 25 may exhaust spent
cooling air along primary flow paths through the relatively large
exit holes 32 in the shroud edges 28, as represented by the arrows
A. Indeed, it is believed that the low flow velocity regions 34,
because of the tortuous and/or constricted flow path and/or lack of
proximal exit holes, experience cooling air flow recirculation
and/or stagnation, which may lead to hot spots and premature tip
shroud failure. The relatively low air flow through the low flow
velocity regions 34 may further be the result of flow moving past
what is sometimes referred to as a "bluff" body, for example, the
supporting ribs previously described, which may separate the moving
air and create a wake recirculation zone, similar to what occurs
when air moves over a large blunt obstruction like a vehicle and
then separates behind the rear face of the object.
[0020] According to the present disclosure, there may be provided
one or more purge holes 36 positioned in the low flow velocity
regions 34 of the tip shroud 12. The purge holes 36 may be
circular, and may be drilled from the outer top surface 38 and/or
interior or bottom surface 41 of the tip shroud 12. As illustrated
in FIG. 3, the purge holes 36 may include side walls 39 that may be
cylindrical, and oriented radially from the internal tip shroud
cavity 22 outwardly, as illustrated by the directional arrows B.
Other orientations, such as angled or flared purge holes 36 that
may be oriented to direct the spent cooling air in the direction of
flow of the combustion gas stream (i.e. film cooling), are also
possible.
[0021] The number and diameter of the purge holes 36 may depend on
the design requirements and manufacturing process capability. For
example, as illustrated in FIG. 2, the purge holes 36 may be
oriented substantially linearly along the low flow velocity region
34. In the embodiment illustrated, the purge holes 36 may be
substantially the same size and substantially equally spaced along
a line P that may substantially bisect the width of the low flow
velocity region 34. Such an orientation may place the purge holes
36 in the vicinity of the low flow velocity region 34 that is the
greatest distance from the outer boundaries 40 of adjacent high
flow velocity regions 25, where the flow velocity of cooling air
may be lowest and stagnation highest absent such purge holes 36.
Other orientations are possible, including, for example, a matrix
of purge holes, particularly for larger areas of low flow velocity,
and/or purge holes that follow a substantially curvilinear path,
for low flow velocity areas that are substantially curvilinear.
[0022] The purge holes 36 may, as illustrated in FIGS. 1-3 be
substantially the same size and/or substantially equally spaced.
Other configurations are of course possible, including purge holes
that increase in size and/or number, or decrease in relative
spacing, from relatively narrower regions 42 of the low flow
velocity region 34 to the relatively wider region 44 of the low
flow velocity region 34. Although the purge holes 36 are shown as
circular, other configurations, such as elliptical, oval, square,
conical, etc., may be employed.
[0023] Incorporating purge holes 36 in the low flow velocity
regions 34 of the tip shroud 12 may provide for exit of cooling air
from the outer top surface 38 and/or bottom surface 41 of the tip
shroud 12, also represented by solid line arrows B and dotted line
arrows C, respectively, in FIG. 3. This, in turn, may lead to
reducing or eliminating stagnation of cooling air in the low flow
velocity regions 34, and may increase cooling air velocity through
such regions, with resultant increase in the local heat transfer
coefficient due to flow acceleration around the entrance 37 of the
purge holes 36, and therefore increased cooling of the tip shroud
12 proximate such regions. This improved heat transfer, in turn,
may reduce localized metal temperatures of the tip shroud 12,
thereby enhancing part durability.
[0024] Furthermore, the incorporation of purge holes 36 may result
in exiting film flow of spent cooling air, which may in turn, cause
a reduction in external film temperature proximate the outer top
surface 38 and/or bottom surface 41 of the tip shroud, which may
also enhance part durability.
[0025] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. Where the definition of terms departs from the
commonly used meaning of the term, applicant intends to utilize the
definitions provided below, unless specifically indicated. As used
herein, the singular forms "a", "an" and "the" are intended to
include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms
"comprises" and/ or "comprising," when used in this specification,
specify the presence of stated features, integers, steps,
operations, elements, and/ or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof It
will be understood that, although the terms first, second, etc. may
be used herein to describe various elements, these elements should
not be limited by these terms. These terms are only used to
distinguish one element from another. For example, a first element
could be termed a second element, and, similarly, a second element
could be termed a first element, without departing from the scope
of example embodiments. As used herein, the term "and/or" includes
any, and all, combinations of one or more of the associated listed
items. As used herein, the phrases "coupled to" and "coupled with"
as used in the specification and the claims contemplates direct or
indirect coupling.
[0026] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
of ordinary skill in the art to practice the invention, including
making and using any devices or systems and performing any
incorporated methods. The steps recited in the accompanying method
claims need not be taken in the recited order, where other orders
of conducting the steps to achieve the desired result would be
readily apparent to those of ordinary skill in the art. The
patentable scope of the invention is defined by the claims, and may
include other examples that occur to those of ordinary skill in the
art. Such other examples are intended to be within the scope of the
claims if they have structural elements that do not differ from the
literal language of the claims or if they include equivalent
structural elements with insubstantial differences from the literal
languages of the claims.
* * * * *