U.S. patent application number 13/600782 was filed with the patent office on 2014-03-06 for cooling arrangement for platform region of turbine rotor blade.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is Adebukola Oluwaseun Benson, Christopher William Kester, Camilo Andres Sampayo, Xiuzhang James Zhang. Invention is credited to Adebukola Oluwaseun Benson, Christopher William Kester, Camilo Andres Sampayo, Xiuzhang James Zhang.
Application Number | 20140064984 13/600782 |
Document ID | / |
Family ID | 50098556 |
Filed Date | 2014-03-06 |
United States Patent
Application |
20140064984 |
Kind Code |
A1 |
Zhang; Xiuzhang James ; et
al. |
March 6, 2014 |
COOLING ARRANGEMENT FOR PLATFORM REGION OF TURBINE ROTOR BLADE
Abstract
A platform cooling arrangement in a turbine rotor blade having a
platform at an interface between an airfoil and a root. The
platform may include a pressure side slashface and a suction side
slashface. The platform cooling arrangement may include: a cooling
channel formed within the interior of the platform, the cooling
channel extending from a first end toward one of the pressure side
slashface and the suction side slashface. At a second end, the
cooling channel may include a pocket. The pocket may include an
abrupt increase in cross-sectional flow area just before the
cooling channel reaches the slashface.
Inventors: |
Zhang; Xiuzhang James;
(Simpsonville, SC) ; Sampayo; Camilo Andres;
(Greer, SC) ; Benson; Adebukola Oluwaseun;
(Simpsonville, SC) ; Kester; Christopher William;
(Greenville, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zhang; Xiuzhang James
Sampayo; Camilo Andres
Benson; Adebukola Oluwaseun
Kester; Christopher William |
Simpsonville
Greer
Simpsonville
Greenville |
SC
SC
SC
SC |
US
US
US
US |
|
|
Assignee: |
General Electric Company
|
Family ID: |
50098556 |
Appl. No.: |
13/600782 |
Filed: |
August 31, 2012 |
Current U.S.
Class: |
416/97R |
Current CPC
Class: |
F01D 5/18 20130101; F01D
5/187 20130101; Y02T 50/60 20130101; Y02T 50/676 20130101; F05D
2240/81 20130101 |
Class at
Publication: |
416/97.R |
International
Class: |
F01D 5/18 20060101
F01D005/18 |
Claims
1. A platform cooling arrangement in a turbine rotor blade having a
platform at an interface between an airfoil and a root, wherein the
platform comprises a pressure side slashface and a suction side
slashface, the platform cooling arrangement comprising: a cooling
channel formed within the interior of the platform, the cooling
channel extending from a first end toward one of the pressure side
slashface and the suction side slashface; wherein, at a second end,
the cooling channel comprises a pocket, the pocket comprises an
abrupt increase in cross-sectional flow area just before the
cooling channel reaches the one of the pressure side slashface and
the suction side slashface.
2. The platform cooling arrangement according to claim 1, wherein
the first end of the cooling channel connects to a port formed at
an underside of the platform, the port configured to fluidly
communicate with a shank cavity cooling source during
operation.
3. The platform cooling arrangement according to claim 3, wherein
the first end of the cooling channel connects to a plenum formed
within the interior of the platform, the plenum comprising a
cross-sectional flow area greater than a cross-sectional flow area
of the cooling channel.
4. The platform cooling arrangement according to claim 3, wherein
the rotor blade includes an interior cooling passage formed therein
that extends from a connection with a coolant source at the root of
the rotor blade to at least the approximate radial height of the
platform; further comprising a connector that connects the plenum
to the interior cooling passage.
5. The platform cooling arrangement according to claim 3, further
comprising a plurality of cooling channels; wherein each of the
plurality of cooling channels connects to the plenum at the first
end; and wherein, at the second end, each of the plurality of
cooling channels includes the pocket, each of the pockets
comprising an abrupt increase in cross-sectional flow area just
before the cooling channel reaches the one of the pressure side
slashface and the suction side slashface.
6. The platform cooling arrangement according to claim 5, wherein
the plurality of pockets are disposed along the suction side
slashface.
7. The platform cooling arrangement according to claim 5, wherein
the plurality of pockets are disposed at regular intervals along
the pressure side slashface; and wherein the plurality of pockets
comprises between 4 and 8 pockets.
8. The platform cooling arrangement according to claim 5, wherein
the plurality of pockets are dispersed along the pressure side
slashface; and wherein each of the plurality of pockets comprises a
concave depression formed in the pressure side slashface.
9. The platform cooling arrangement according to claim 8, wherein
each of the plurality of pockets includes a mouth coplanar to the
pressure side slashface; wherein, from the mouth, each of the
pockets extends into the platform a short distance and terminates
at an inner wall, the inner wall residing opposite the mouth;
wherein each of the pockets comprises a port through which coolant
traveling through the cooling channel enters the pocket; and
wherein the port is disposed on the inner wall of the pocket.
10. The platform cooling arrangement according to claim 9, wherein
the mouth of each of the plurality of pockets comprises a
rectangular profile.
11. The platform cooling arrangement according to claim 9, wherein
each of the pockets comprises: a depth that defines a
circumferential distance between the mouth and the inner wall; a
height that defines a radial height of the pocket; a width that is
an axial width of the pocket; wherein the pocket is configured such
that the depth comprises 0.1 and 0.6 times a circumferential depth
of the platform; wherein the height of the pocket is between 0.1
and 0.9 times a radial height of the platform; wherein the width of
the pocket is between 0.1 and 0.4 times an axial width of the
platform; and wherein the port comprises a cross-sectional flow
area that is between 0.1 and 0.6 times a cross-sectional flow area
of the mouth.
12. The platform cooling arrangement according to claim 9, wherein
each of the pockets comprises: a depth that defines a
circumferential distance between the mouth and the inner wall; a
height that defines a radial height of the pocket; a width that is
an axial width of the pocket; wherein the pocket is configured such
that the depth comprises 0.2 and 0.3 times a circumferential depth
of the platform; wherein the height of the pocket is between 0.4
and 0.8 times a radial height of the platform; and wherein the
width of the pocket is between 0.2 and 0.3 times an axial width of
the platform; and wherein the port comprises a cross-sectional flow
area that is between 0.2 and 0.4 times a cross-sectional flow area
of the mouth.
13. The platform cooling arrangement according to claim 8, wherein
the mouth comprises a greater cross-sectional flow area than both
the port and the cooling channel.
14. The platform cooling arrangement according to claim 8, further
comprising a pocket-to-pocket channel, the pocket-to-pocket channel
comprising an interior channel that connects one of the plurality
of pockets to a neighboring pocket.
15. The platform cooling arrangement according to claim 14, wherein
the pocket-to-pocket channel is parallel to the pressure side
slashface and configured to allow fluid communication between the
one pocket and the neighboring pocket.
16. The platform cooling arrangement according to claim 14, wherein
the pocket-to-pocket channel comprises a cross-sectional flow area
that is less than the cross-sectional flow area of the mouth of
each of the one pocket and the neighboring pocket.
17. The platform cooling arrangement according to claim 8, further
comprising a pocket-to-topside channel, the pocket-to-topside
channel comprising an interior channel that connects one of the
plurality of pockets to a topside of the platform.
18. The platform cooling arrangement according to claim 17, wherein
the pocket-to-topside channel is configured to allow fluid
communication between a port located on an outboard inner surface
of the pocket and a topside port formed on the topside of the
platform.
19. The platform cooling arrangement according to claim 17, wherein
the pocket-to-topside channel comprises a cross-sectional flow area
that is less than the cross-sectional flow area of the mouth of the
pocket; and wherein the pocket-to-topside channel is canted in a
downstream direction.
20. The platform cooling arrangement according to claim 5, wherein
the plenum comprises a hollow passageway, the plenum extending from
an interior position to a position near one of the pressure side
slashface and the suction side slashface; wherein the plenum
includes an plenum outlet that connects to another pocket formed on
the one of the pressure side slashface and the suction side
slashface; and wherein the plenum outlet comprises a
cross-sectional flow area that is less than the cross-sectional
flow area of the plenum.
21. The platform cooling arrangement according to claim 20, wherein
the cross-sectional flow area of the plenum outlet is configured
such that a desired metering characteristic is achieved.
22. The platform cooling arrangement according to claim 21, further
comprising a non-integral plug positioned between the plenum and
the pocket, the non-integral plug configured to reduce the
cross-sectional flow area of the plenum so to form the plenum
outlet.
23. The platform cooling arrangement according to claim 5, wherein
the plenum comprises a supply chamber from which the plurality of
cooling channels branch; and each of the plurality of cooling
channels comprises a linear passageway that extends between the
plenum and one of the pockets.
24. The platform cooling arrangement according to claim 23, further
comprising a plurality of plenums, each of which includes a
plurality of cooling channels branching therefrom.
25. A platform cooling arrangement in a turbine rotor blade having
a platform at an interface between an airfoil and a root, wherein
the rotor blade includes an interior cooling passage formed therein
that extends from a connection with a coolant source at the root to
at least the approximate radial height of the platform, wherein,
along a side that coincides with a pressure side of the airfoil, a
pressure side of the platform comprises a topside extending
circumferentially from the airfoil to a pressure side slashface,
and along a side that coincides with a suction side of the airfoil,
a suction side of the platform comprises a topside extending
circumferentially from the airfoil to a suction side slashface, the
platform cooling arrangement comprising: a plenum residing just
inboard of the planar topside and extending from an interior
position to a position near one of the pressure side slashface and
the suction side slashface of the platform, the plenum having a
longitudinal axis that is approximately parallel to the planar
topside; a connector that is configured to fluidly connect the
plenum and the interior cooling passage; and a plurality of cooling
channels, each of which includes, at a first end, a connection with
the plenum and, at a second end, a pocket formed at the one of the
pressure side slashface and the suction side slashface; wherein
each of the pockets includes an abrupt increase in cross-sectional
flow area of the cooling channel, the abrupt increase in
cross-sectional flow area extending from a port formed along an
inner wall of the pocket to a mouth coplanar to the one of the
pressure side slashface and the suction side slashface over.
Description
BACKGROUND OF THE INVENTION
[0001] The present application relates generally to combustion
turbine engines, which, as used herein and unless specifically
stated otherwise, includes all types of combustion turbine engines,
such as those used in power generation and aircraft engines. More
specifically, but not by way of limitation, the present application
relates to apparatus, systems and/or methods for cooling the
platform region of turbine rotor blades.
[0002] A gas turbine engine typically includes a compressor, a
combustor, and a turbine. The compressor and turbine generally
include rows of airfoils or blades that are axially stacked in
stages. Each stage typically includes a row of circumferentially
spaced stator blades, which are fixed, and a set of
circumferentially spaced rotor blades, which rotate about a central
axis or shaft. In operation, the rotor blades in the compressor are
rotated about the shaft to compress a flow of air. The compressed
air is then used within the combustor to combust a supply of fuel.
The resulting flow of hot gases from the combustion process is
expanded through the turbine, which causes the rotor blades to
rotate the shaft to which they are attached. In this manner, energy
contained in the fuel is converted into the mechanical energy of
the rotating shaft, which then, for example, may be used to rotate
the coils of a generator to generate electricity.
[0003] Referring to FIGS. 1 and 2, turbine rotor blades 100
generally include an airfoil portion or airfoil 102 and a root
portion or root 104. The airfoil 102 may be described as having a
convex suction face 105 and a concave pressure face 106. The
airfoil 102 further may be described as having a leading edge 107,
which is the forward edge, and a trailing edge 108, which is the
aft edge. The root 104 may be described as having structure (which,
as shown, typically includes a dovetail 109) for affixing the blade
100 to the rotor shaft, a platform 110 from which the airfoil 102
extends, and a shank 112, which includes the structure between the
dovetail 109 and the platform 110.
[0004] As illustrated, the platform 110 may be substantially
planar. More specifically, the platform 110 may have a planar
topside 113, which, as shown in FIG. 1, may include an axially and
circumferentially extending flat surface. As shown in FIG. 2, the
platform 110 may have a planar underside 114, which may also
include an axially and circumferentially extending flat surface.
The topside 113 and the bottom side 114 of the platform 110 may be
formed such that each is substantially parallel to the other. As
depicted, it will be appreciated that the platform 110 typically
has a thin radial profile, i.e., there is a relatively short radial
distance between the topside 113 and the bottom side 114 of the
platform 110.
[0005] In general, the platform 110 is employed on turbine rotor
blades 100 to form the inner flow path boundary of the hot gas path
section of the gas turbine. The platform 110 further provides
structural support for the airfoil 102. In operation, the
rotational velocity of the turbine induces mechanical loading that
creates highly stressed regions along the platform 110 that, when
coupled with high temperatures, ultimately cause the formation of
operational defects, such as oxidation, creep, low-cycle fatigue
cracking, and others. These defects, of course, negatively impact
the useful life of the rotor blade 100. It will be appreciated that
these harsh operating conditions, i.e., exposure to extreme
temperatures of the hot gas path and mechanical loading associated
with the rotating blades, create considerable challenges in
designing durable, long-lasting rotor blade platforms 110 that both
perform well and are cost-effective to manufacture.
[0006] One common solution to make the platform region 110 more
durable is to cool it with a flow of compressed air or other
coolant during operation, and a variety of these type of platform
designs are known. However, as one of ordinary skill in the art
will appreciate, the platform region 110 presents certain design
challenges that make it difficult to cool in this manner. In
significant part, this is due to the awkward geometry of this
region, in that, as described, the platform 110 is a periphery
component that resides away from the central core of the rotor
blade and typically is designed to have a structurally sound, but
thin radial thickness.
[0007] To circulate coolant, rotor blades 100 typically include one
or more hollow cooling passages 116 (see FIGS. 3, 4, 5, and 9)
that, at minimum, extend radially through the core of the blade
100, including through the root 104 and the airfoil 102. As
described in more detail below, to increase the exchange of heat,
such cooling passages 116 may be formed having a serpentine path
that winds through the central regions of the blade 100, though
other configurations are possible. In operation, a coolant may
enter the central cooling passages via one or more inlets 117
formed in the inboard portion of the root 104. The coolant may
circulate through the blade 100 and exit through outlets (not
shown) formed on the airfoil and/or via one or more outlets (not
shown) formed in the root 104. The coolant may be pressurized, and,
for example, may include pressurized air, pressurized air mixed
with water, steam, and the like. In many cases, the coolant is
compressed air that is diverted from the compressor of the engine,
though other sources are possible. As discussed in more detail
below, these cooling passages typically include a high-pressure
coolant region and a low-pressure coolant region. The high-pressure
coolant region typically corresponds to an upstream portion of the
cooling passage that has a higher coolant pressure, whereas the
low-pressure coolant region corresponds to a downstream portion
having a relatively lower coolant pressure.
[0008] In some cases, the coolant may be directed from the cooling
passages 116 into a cavity 119 formed between the shanks 112 and
platforms 110 of adjacent rotor blades 100. From there, the coolant
may be used to cool the platform region 110 of the blade, a
conventional design of which is presented in FIG. 3. This type of
design typically extracts air from one of the cooling passages 116
and uses the air to pressurize the cavity 119 formed between the
shanks 112/platforms 110. Once pressurized, this cavity 119 then
supplies coolant to cooling channels that extend through the
platform 110. After traversing the platform 110, the cooling air
may exit the cavity through film cooling holes formed in the
topside 113 of the platform 110.
[0009] It will be appreciated, however, that this type of
conventional design has several disadvantages. First, the cooling
circuit is not self-contained in one part, as the cooling circuit
is only formed after two neighboring rotor blades 100 are
assembled. This adds a great degree of difficulty and complexity to
installation and pre-installation flow testing. A second
disadvantage is that the integrity of the cavity 119 formed between
adjacent rotor blades 100 is dependent on how well the perimeter of
the cavity 119 is sealed. Inadequate sealing may result in
inadequate platform cooling and/or wasted cooling air. A third
disadvantage is the inherent risk that hot gas path gases may be
ingested into the cavity 119 or the platform itself 110. This may
occur if the cavity 119 is not maintained at a sufficiently high
pressure during operation. If the pressure of the cavity 119 falls
below the pressure within the hot gas path, hot gases will be
ingested into the shank cavity 119 or the platform 110 itself,
which typically damages these components as they were not designed
to endure exposure to the hot gas-path conditions.
[0010] FIGS. 4 and 5 illustrate another type of conventional design
for platform cooling. In this case, the cooling circuit is
contained within the rotor blade 100 and does not involve the shank
cavity 119, as depicted. Cooling air is extracted from one of the
cooling passages 116 that extend through the core of the blade 110
and directed aft through cooling channels 120 formed within the
platform 110 (i.e., "platform cooling channels 120"). As shown by
the several arrows, the cooling air flows through the platform
cooling channels 120 and exits through outlets in the aft edge 121
of the platform 110 or from outlets disposed along the suction side
edge 122. (Note that in describing or referring to the edges or
faces of the rectangular platform 110, each may be delineated based
upon its location in relation to the suction face 105 and pressure
face 106 of the airfoil 102 and/or the forward and aft directions
of the engine once the blade 100 is installed. As such, as one of
ordinary skill in the art will appreciate, the platform may include
an aft edge 121, a suction side edge 122, a forward edge 124, and a
pressure side edge 126, as indicated in FIGS. 3 and 4. In addition,
the suction side edge 122 and the pressure side edge 126 also are
commonly referred to as "slashfaces" and the narrow cavity formed
therebetween once neighboring rotor blades 100 are installed may be
referred to as a "slashface cavity".)
[0011] It will be appreciated that the conventional designs of
FIGS. 4 and 5 have an advantage over the design of FIG. 3 in that
they are not affected by variations in assembly or installation
conditions. However, conventional designs of this nature have
several limitations or drawbacks. First, as illustrated, only a
single circuit is provided on each side of the airfoil 102 and,
thus, there is the disadvantage of having limited control of the
amount of cooling air used at different locations in the platform
110. Second, conventional designs of this type have a coverage area
that is generally limited. While the serpentine path of FIG. 5 is
an improvement in terms of coverage over FIG. 4, there are still
dead areas within the platform 110 that remain uncooled. Third, to
obtain better coverage with intricately formed platform cooling
channels 120, manufacturing costs increase dramatically,
particularly if the cooling channels having shapes that require a
casting process to form. Fourth, these conventional designs
typically dump coolant into the hot gas path after usage and before
the coolant is completely exhausted, which negatively affects the
efficiency of the engine. Fifth, conventional designs of this
nature generally have little flexibility. That is, the channels 120
are formed as an integral part of the platform 110 and provide
little or no opportunity to change their function or configuration
as operating conditions vary. In addition, these types of
conventional designs are difficult to repair or refurbish.
[0012] Another issue relates to the difficulties around cooling the
pressure side and suction side slashfaces 126, 122. Conventional
designs may include ports located on the slashfaces 126, 122 for
the release of coolant. The ports are configured to release an
impinged, high-velocity stream of coolant. However, with these
conventional techniques, the ports lack sophisticated exit
geometry, which results in a steep thermal gradient around each of
the port and, more generally, along the slashfaces of the platform,
as well as, at the target surface of the impingement stream. Such
thermal gradients increase the degradation within this region of
the rotor blade. As a result, conventional platform cooling designs
are lacking in one or more significant criteria. There remains a
need for improved apparatus, systems, and methods that effectively
and efficiently cool the platform region of turbine rotor blades,
while also being cost-effective to construct, flexible in
application, and durable.
BRIEF DESCRIPTION OF THE INVENTION
[0013] The present application thus describes a platform cooling
arrangement in a turbine rotor blade having a platform at an
interface between an airfoil and a root. The platform may include a
pressure side slashface and a suction side slashface. The platform
cooling arrangement may include: a cooling channel formed within
the interior of the platform, the cooling channel extending from a
first end toward one of the pressure side slashface and the suction
side slashface. At a second end, the cooling channel may include a
pocket. The pocket may include an abrupt increase in
cross-sectional flow area just before the cooling channel reaches
the slashface.
[0014] These and other features of the present application will
become apparent upon review of the following detailed description
of the preferred embodiments when taken in conjunction with the
drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] These and other features of this invention will be more
completely understood and appreciated by careful study of the
following more detailed description of exemplary embodiments of the
invention taken in conjunction with the accompanying drawings, in
which:
[0016] FIG. 1 illustrates a perspective view of an exemplary
turbine rotor blade in which embodiments of the present invention
may be employed;
[0017] FIG. 2 illustrates an underside view of a turbine rotor
blade in which embodiments of the present invention may be
used;
[0018] FIG. 3 illustrates a sectional view of neighboring turbine
rotor blades having a cooling system according to conventional
design;
[0019] FIG. 4 illustrates a top view of a turbine rotor blade
having a platform with interior cooling channels according to
conventional design;
[0020] FIG. 5 illustrates a top view of a turbine rotor blade
having a platform with interior cooling channels according to an
alternative conventional design;
[0021] FIG. 6 illustrates a perspective view of a turbine rotor
blade having a platform cooling configuration according to an
exemplary embodiment of the present invention;
[0022] FIG. 7 illustrates a top with partial cross-sectional view
of a platform of a turbine rotor blade having a cooling
configuration according to an exemplary embodiment of the present
invention;
[0023] FIG. 8 illustrates a front view from the vantage point along
8-8 of FIG. 7;
[0024] FIG. 9 illustrates a cross-sectional view along 9-9 of FIG.
7;
[0025] FIG. 10 illustrates a side view of a platform cooling
configuration according to an alternative embodiment of the present
application;
[0026] FIG. 11 illustrates a side view of a platform cooling
configuration according to an alternative embodiment of the present
application; and
[0027] FIG. 12 illustrates a top with partial cross-sectional view
of a turbine rotor blade having a platform cooling configuration
according to an alternative embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] As discussed above, various conventional designs of internal
cooling passages 116 are somewhat effective at cooling certain
regions within a rotor blade 100. However, as one of ordinary skill
in the art will appreciate, the platform region proves more
challenging. This is due, at least in part, to the awkward geometry
of the platform--i.e., its narrow radial height and the manner in
which it juts away from the core or main body of the rotor blade
100. Nevertheless, given its exposures to the extreme temperatures
of hot gas path and high mechanical loading, the cooling
requirements of the platform 110 are considerable. As described
above, conventional platform cooling designs are ineffective
because they fail to address the particular challenges of the
region, are inefficient with their usage of coolant, and/or are
costly to fabricate.
[0029] Several particular descriptive terms may be used to describe
exemplary embodiments of the present application. The meaning for
these terms shall include the following definitions. The terms
"downstream" and "upstream" are terms that indicate a direction
relative to the flow of working fluid through the turbine or, as
the case may be, coolant through a cooling passage. Accordingly,
the term "downstream" means the direction of the flow, and the term
"upstream" means in the opposite direction of the flow. The term
"radial" refers to movement or position perpendicular to an axis.
It is often required to describe parts that are at differing radial
positions with regard to this axis. In these cases, if a first
component resides closer to the axis than a second component, it
may be stated herein that the first component is either "inboard"
or "radially inward" of the second component. If, on the other
hand, the first component resides further from the axis than the
second component, it may be stated herein that the first component
is "outboard" or "radially outward" of the second component. The
term "axial" refers to movement or position parallel to an axis.
And, the term "circumferential" refers to movement or position
around an axis. Unless otherwise stated, when the terms "radial",
"axial", or "circumferential" are used, they are used in reference
to the central axis of the turbine engine.
[0030] It will be appreciated that turbine blades that are cooled
via the internal circulation of a coolant typically include an
interior cooling passage 116 that extends radially outward from the
root, through the platform region, and into the airfoil, as
described above in relation to several conventional cooling
designs. It will be appreciated that certain embodiments of the
present invention may be used in conjunction with conventional
coolant passages to enhance or enable efficient active platform
cooling, and the present invention is discussed in connection with
an exemplary common design: an interior cooling passage 116 having
a winding or serpentine configuration. As depicted in FIGS. 5 and
7, the serpentine path is typically configured to allow a one-way
flow of coolant and includes features that promote the exchange of
heat between the coolant and the surrounding rotor blade 100. In
operation, a pressurized coolant, which typically is compressed air
bled from the compressor (though other types of coolant, such as
steam, also may be used with embodiments of the present invention),
is supplied to the interior cooling passage 116 through a
connection formed through the root 104. The pressure drives the
coolant through the interior cooling passage 116, and the coolant
convects heat from the surrounding walls. It will be appreciated
that the present invention may be used in rotor blades 100 having
internal cooling passages of different configurations and is not
limited to interior cooling passages having a serpentine form.
Accordingly, as used herein, the term "interior cooling passage" or
"cooling passage" is meant to include any passage or hollow channel
through which coolant may be circulated in the rotor blade. As
provided herein, the exemplary interior cooling passage 116 extends
to at least to the approximate radial height of the platform 116.
Though not shown, it will be appreciated that the present invention
may also be employed using a shank fed coolant source, such as the
one illustrated in FIG. 3.
[0031] Referring now to FIGS. 6 through 12, several views of
exemplary embodiments of the present invention are provided. The
present application describes depressive geometrical features or
pockets formed along the slash faces of the platform of turbine
rotor blades. These features include a set of pockets that connect
to interior coolant channels formed through the platform, which may
be supplied with coolant from interior channels in the root of the
rotor blade or from the shank cavity that is formed between two
adjacent rotor blades. It will be appreciated that, as described in
detail below, the depressive geometrical features of the present
application may be employed to defuse and slow the coolant just
before the coolant is expelled from the platform, which may results
in the beneficial reduction of thermal gradients at the slashface
of rotor blades.
[0032] FIGS. 6 through 12 illustrate a turbine rotor blade 100
having a platform cooling configuration 130 according to preferred
embodiments of the present invention. As shown, the rotor blade 100
includes a platform 110 residing at the interface between an
airfoil 102 and a root 104. In the exemplary embodiment shown, the
rotor blade 100 includes an interior cooling passage 116 that
extends from the root 104 to the radial height of the platform 110,
and, in this case, into the airfoil 102. At the side of the
platform 110 that corresponds with a pressure face 106 of the
airfoil 102, it will be appreciated that the platform 110 may have
a planar topside 113 that extends from the airfoil 102 to a
pressure side slashface 126. (Note that "planar," as used herein,
means approximately or substantially in the shape of a plane. For
example, one of ordinary skill in the art will appreciate that
platforms may be configured to have an outboard surface that is
slight curved and convex, with the curvature corresponding to the
circumference of the turbine at the radial location of the rotor
blades. As used herein, this type of platform shape is deemed
planar, as the radius of curvature is sufficiently great to give
the platform a flat appearance.)
[0033] Configured within the interior of the platform 110, an
exemplary embodiment of the present invention includes different
types of hollow passageways that are configured to distribute
coolant through regions of the platform 110. Though other
configurations are possible, in a preferred embodiment, these
hollow coolant passageways include one or more plenums 132; one or
more connectors 134 (which connects the plenum 132 to the interior
cooling passage 116); a plurality of cooling channels 136, each of
which branches from one of the plenum 132 at one end and includes,
at the other end, a pockets 144 positioned along the pressure side
slashface 126 (or, in alternative embodiments, the suction side
slashface 122). The pocket 144 may include a port 146 through which
coolant flowing through the cooling channel enters the pocket
144.
[0034] In certain embodiments, a plurality of pockets 144 is
dispersed along the pressure side slashface 126. As illustrated,
each pocket 144, in general, is a concave depression or bowl-like
feature formed in the pressure side slashface 126. Each pocket 144
includes a mouth 148 residing coplanar to the plane of the
slashface 126. As shown in FIG. 8, the profile of the mouth 148 may
be rectangular as shown, though other shapes are possible. From the
mouth 148, the pocket 144 extends into the platform 110 a
relatively short distance to an inner wall 149, which is opposite
the mouth 148. The port 146 may be formed in the inner wall 149 of
the pocket 144. The pocket 144 may be described as having a depth,
which describes a circumferential depth of the pocket 144 or, put
another way, the distance between the mouth 148 and the inner wall
149. The pocket 144 further may be described as having a height,
which describes the radial height of the pocket 144. The pocket 144
further may be described as having a width, which describes the
axial width of the pocket 144. In certain preferred embodiments,
the size of the pocket 144 (i.e., the depth, height, and width of
the pocket 144) may be described by how each relates the
corresponding dimension of the platform 110 (i.e., the
circumferential depth, radial height, and axial width of the
platform 110, respectively). For example, in certain preferred
embodiments, the depth of the pocket 144 may be between 0.1 and 0.6
times the circumferential depth of the platform 110. The height of
the pocket 144 may be between 0.1 and 0.9 times the radial height
of the platform 110. And, the width of the pocket 144 may be
between 0.1 and 0.4 times the axial width of the platform 110. In
certain other preferred embodiments, the depth of the pocket 144
may be between 0.2 and 0.3 times the circumferential depth of the
platform 110. The height of the pocket 144 may be between 0.4 and
0.8 times the radial height of the platform 110. And, the width of
the pocket 144 may be between 0.2 and 0.3 times the axial width of
the platform 110.
[0035] As stated, the port 146 may have a significantly smaller
cross-sectional flow area than cross-sectional flow area through
the pocket 144 and the mouth 148. In certain preferred embodiments,
the port 146 has a cross-sectional flow area that is between 0.1
and 0.6 times a cross-sectional flow area of the mouth 148. In
certain other preferred embodiments, the port 146 has a
cross-sectional flow area that is between 0.2 and 0.4 times a
cross-sectional flow area of the mouth 148. It will be appreciated
that this type of increase in cross-sectional flow area will slow
the flow of coolant as it moves from the port 146 to the mouth 148
of the pocket 144.
[0036] The pocket 144, as stated, may include a port 146 formed in
the inner wall 149. The port 149, via the cooling channel 136,
fluidly links the pocket 144 to a supply of coolant. In a preferred
embodiment, the port 146, via the cooling channel 136, connects to
the plenum 132. It will be appreciated that the present invention
may function with different types of coolant sources. For example,
the port 146 could be connected to a channel that derives coolant
from a shank cavity source, as discussed below in relation to FIG.
10. As illustrated, the port 146 may be disposed on the inner wall
149 of the pocket 144. The mouth 148, it will be appreciated, has a
greater cross-sectional flow area than the port 146/cooling channel
136 that supply the pocket 144 with coolant. Another manner by
which the pocket 144 may be described is that the pocket 144
includes a configuration that abruptly increases the
cross-sectional flow area of the cooling channel 136 just before
the cooling channel 136 reaches one of the slashfaces 122, 126.
[0037] In some embodiments, as illustrated in FIG. 10, neighboring
pockets 144 may be connected via a pocket-to-pocket channel 151.
The pocket-to-pocket channel 151 is configured to allow fluid
communication between pockets 144. The pocket-to-pocket channel 151
may direct coolant to areas of greater need. FIG. 10 further
includes an embodiment in which the cooling channel 136 links the
pocket 144 to the shank cavity 119. In this case, a cooling channel
136 extends from the port 146 formed on the inner wall 149 of the
pocket 144 to an underside port 155 positioned on the underside 114
of the platform 110. As illustrated, the pockets 144 may be axially
concentrated along the pressure side slashface 126 between the
leading edge 107 and the trailing edge 108 of the airfoil 102. In
certain preferred embodiments, there may be between 4 and 8 pockets
formed along the pressure side slashface 126. Additionally, in the
same manner as described above, pockets 144 may be formed at a
plenum outlet 133.
[0038] In some embodiments, as illustrated in FIG. 11, pockets 144
may include a discharge channel that connects the pocket 144 to the
topside 113 of the platform 110, which will be referred to herein
as a pocket-to-topside channel 161. Specifically, the
pocket-to-topside channel 161 is configured to allow fluid
communication between a port located on a ceiling or outboard inner
surface of the pocket 144 and a topside sport 163 formed on the
topside 113 of the platform 110. It will be appreciated that the
pocket-to-topside channel 161 may allow a portion of the coolant
flowing through the pocket 144 to be diverted to the topside 113 of
the platform 110 for film cooling purposes. Though the
pocket-to-topside channel 161 may be aligned otherwise, in a
preferred embodiment, the pocket-to-topside channel 161 may be
canted in the downstream direction, as illustrated. It will be
appreciated that this directional alignment reduces coolant in a
manner that reduces mixing losses as well as promoting greater film
cooling efficiency.
[0039] In regard to the plenum 132, embodiments of the present
invention may include a single or multiple plenums 132, as
illustrated in FIG. 7. Each plenum 132 may be formed just inboard
of the planar topside 113. As shown, in certain preferred
embodiments, the plurality of plenums 132 may be provided within
the pressure side of the platform 110. It will be appreciated that
the features described herein also may be located on the suction
side of the platform 110 and function similarly. In such a case,
the pockets 144 will be disposed along the suction side slashface
122. An example of this type of embodiment is illustrated in FIG.
12. In one preferred embodiment, there may be a plenum 132 located
in a forward area of the blade 100 and another located in the
rearward area of the blade 100.
[0040] As provided in FIG. 7, one of the formed plenums 132 may be
disposed in more of a forward position than the other. In a
preferred embodiment, the plenum or plenums 132 may be aligned
approximately parallel to the aft edge 121 and forward edge 124 of
the platform 110, and may be configured as long and relatively
narrow and hollow passageways. The plenum or plenums 132 may have a
longitudinal axis that is parallel to the planar topside 126 of the
platform 110. In certain embodiments, each of the plenums 132
extends from an interior position to a position on the pressure
side slashface 126. In general, the plenums 132 may be configured
to form a supply chamber from which smaller interior coolant
passageways (i.e., the cooling channels 136) branch. A plurality of
the cooling channels 136 may branch from each plenum 132. The
cooling channels 136 may be linear and configured to extend away
from the plenum 132. The cooling channels 136 may include a pocket
144 formed on one of the slashfaces. It will be appreciated that
this arrangement may be used to effectively distribute coolant
within the various regions of the platform 110, as discussed in
more detail below.
[0041] In certain embodiments, a plenum 132 extends toward one of
the slashfaces and, near the slashface, includes a plenum outlet
133 that connects to another pocket 144 formed at the pressure side
slashface 126, as shown in FIG. 7, or the suction side slashface,
as shown in FIG. 12. In the preferred embodiment of FIG. 7, the
rearward plenum 132 includes a plenum outlet or outlet 133 at an
aft position on the pressure side slashface 126, and the forward
plenum 132 also may include a plenum outlet 133 at a forward
position on the pressure side slashface 126. As illustrated, the
plenum outlet 133 may be configured such that it has a
cross-sectional flow area that is less than the cross-sectional
flow area of the plenum 132. The cross-sectional flow area of the
plenum outlets 133 may be reduced in this manner because of the
need to evenly distribute coolant throughout the interior of the
platform 110. That is, the plenum 132 may be designed to distribute
coolant to the several cooling channels 136 with little pressure
loss. To accomplish this, the cross-sectional flow area of the
plenum 132 typically is significantly larger than the
cross-sectional flow area of the cooling channels 136. It will be
appreciated that if the plenum outlets 133 were not reduced in size
compared to the size of the plenum 132, an inordinate amount of
coolant would exit the platform 110 through the plenum outlet 133
and the supply of coolant available to the cooling channels 136
would be likely insufficient. The plenum outlets 133, thus, may be
sized to have a cross-sectional flow area that corresponds to a
desired metering characteristic. A "desired metering
characteristic," as used herein, refers to a flow area through the
coolant passageway that corresponds or results in a desired
distribution of coolant or expected distribution of coolant through
the several coolant passageways and/or the outlets that are formed
along the pressure side slashface 126.
[0042] In some embodiments, a plug 138 may be used to reduce the
cross-sectional flow area of the plenum 132 such that the plenum
outlet 133 is formed, as illustrated. The plug 138 may be formed
such that, upon installation, it reduces the cross-sectional flow
area through the cooling passage in which it resides. In this case,
the plug 138 is configured to allow a desired level of coolant flow
through the plenum outlet 133, with the remainder forced through
alternative outlets. Specifically, the plug 138 may be configured
to be inserted into the plenum 132 and reduce its cross-sectional
flow area by blocking a portion of the flow area therethrough,
thereby forming the plenum outlet 133. The plug 138 may be designed
so that it reduces the flow area to a desired or predetermined
cross-sectional flow area that relates to metering the coolant
through the cooling configuration. In certain embodiments, as
shown, the plug 138 may be formed with a central channel such that
it forms an approximate "doughnut" shape. The plug 138 may be made
of conventional materials and installed using conventional methods
(i.e., welding, brazing, etc.). Once installed, an outer face of
the plug 138 may reside flush in relation to the inner wall 149 of
the pocket 144.
[0043] The connector 134, as shown, may extend in an approximate
circumferential direction between the plenum 132 and the interior
cooling passage 116. It will be appreciated that the connector 134
provides a passageway for an amount of coolant to flow from the
interior cooling passage 116 to the plenum 132. In one embodiment,
the connector 134 may be approximately parallel to the forward edge
124 and the aft edge 121 of the platform 110.
[0044] As stated, the cooling channels 136 may be configured such
that each extends from the pressure side slashface 126 to a
connection with the plenum 132. As shown, the cooling channels 136
may be linear. The longitudinal axis of the cooling channels 136
may be canted with respect to the longitudinal axis of the plenum
132. The cooling channels 136 have smaller cross-sectional flow
areas than the plenum 132 and/or the connector 134. It will be
appreciated that the cooling channels 136 may be configured such
that, during operation, each cooling channel 136 flows coolant
through a pocket 144 formed on the slashface.
[0045] As mentioned above, the pockets 144 and the related interior
coolant passageways (i.e., the connector 134, the plenum 132, and
the cooling channels 136) may be located on the suction side of the
platform 110. As shown in FIG. 12, in such a case, the pockets 144
will be disposed along the suction side slashface 122.
[0046] In operation, it will be appreciated that the plenum 132,
the connector 134, and the cooling channels 136 may be configured
to direct a supply of coolant from the interior cooling passage 116
to a plurality of pockets 144 formed along the pressure side
slashface 126 or the suction side slashface 122. More particularly,
the platform cooling arrangement of the present invention extracts
a portion of the coolant from the interior cooling passage 116 or
shank cavity 119, uses the coolant to remove heat from the platform
110, and then expels the coolant by way of the pocket 144 formed
within the slashface. Released in this manner, the coolant cools
the area of the platform 110 that surrounds the pocket 144 without
creating the steep thermal gradients associated with conventional
impinged release techniques. As stated, this region is typically
difficult to cool and, given the mechanical loads of the area, is a
location that receives high distress, particularly as engine firing
temperatures are further increased. The present application
describes a manner by which the cooling requirements may be
satisfied, while also discouraging the formation of undesirable
thermal gradients within the slashfaces of the platform. As those
of ordinary skill in the art will appreciate, this will extend the
life of a rotor blade by reducing low cycle fatigue in the platform
region.
[0047] As one of ordinary skill in the art will appreciate, the
many varying features and configurations described above in
relation to the several exemplary embodiments may be further
selectively applied to form the other possible embodiments of the
present invention. For the sake of brevity and taking into account
the abilities of one of ordinary skill in the art, all of the
possible iterations is not provided or discussed in detail, though
all combinations and possible embodiments embraced by the several
claims below or otherwise are intended to be part of the instant
application. In addition, from the above description of several
exemplary embodiments of the invention, those skilled in the art
will perceive improvements, changes, and modifications. Such
improvements, changes, and modifications within the skill of the
art are also intended to be covered by the appended claims.
Further, it should be apparent that the foregoing relates only to
the described embodiments of the present application and that
numerous changes and modifications may be made herein without
departing from the spirit and scope of the application as defined
by the following claims and the equivalents thereof.
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