U.S. patent application number 12/604460 was filed with the patent office on 2011-04-28 for structure and method for improving film cooling using shallow trench with holes oriented along length of trench.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Ronald Scott Bunker.
Application Number | 20110097188 12/604460 |
Document ID | / |
Family ID | 43796944 |
Filed Date | 2011-04-28 |
United States Patent
Application |
20110097188 |
Kind Code |
A1 |
Bunker; Ronald Scott |
April 28, 2011 |
STRUCTURE AND METHOD FOR IMPROVING FILM COOLING USING SHALLOW
TRENCH WITH HOLES ORIENTED ALONG LENGTH OF TRENCH
Abstract
A turbine airfoil includes a plurality of shallow trenches. Each
trench includes a plurality of film holes disposed within and
located along the lengthwise direction of the trench and angled
through an airfoil substrate in the lengthwise direction of the
trench.
Inventors: |
Bunker; Ronald Scott;
(Niskayuna, NY) |
Assignee: |
GENERAL ELECTRIC COMPANY
SCHENECTADY
NY
|
Family ID: |
43796944 |
Appl. No.: |
12/604460 |
Filed: |
October 23, 2009 |
Current U.S.
Class: |
415/1 ; 415/115;
416/1; 416/97R |
Current CPC
Class: |
F05D 2260/202 20130101;
F01D 5/186 20130101; F01D 25/12 20130101 |
Class at
Publication: |
415/1 ; 416/97.R;
415/115; 416/1 |
International
Class: |
F01D 25/12 20060101
F01D025/12; F01D 5/18 20060101 F01D005/18 |
Claims
1. A turbine airfoil comprising at least one shallow trench, each
trench comprising a plurality of film holes disposed therein as a
single row and located along the lengthwise direction of the
corresponding trench and angled through a corresponding airfoil
substrate substantially in the lengthwise direction of the
corresponding trench.
2. The turbine airfoil according to claim 1, wherein the shallow
trench is disposed within a showerhead region of the turbine
airfoil.
3. The turbine airfoil according to claim 1, wherein an angle
between a central axis of each hole and the bottom surface of its
corresponding trench is between about 15 degrees and about 50
degrees.
4. The turbine airfoil according to claim 1, wherein an angle
between a central axis of each hole and the bottom surface of its
corresponding trench is between about 20 degrees and about 35
degrees.
5. The turbine airfoil according to claim 1, wherein the shallow
trench is disposed on a forward endwall region of the turbine
airfoil.
6. The turbine airfoil according to claim 1, wherein the depth of
the shallow trench is less than the average throat diameter of the
corresponding film cooling holes.
7. The turbine airfoil according to claim 1, wherein each trench
comprises a width substantially equal to the maximum exit width of
a corresponding film hole measured in the direction as that which
defines the trench width.
8. The turbine airfoil according to claim 1, wherein each trench
comprises a width between about 1.0 and about 1.5 times the maximum
exit footprint width of a corresponding film hole.
9. The turbine airfoil according to claim 1, wherein each trench is
substantially rectangular and comprises side walls having an angle
between about 70 degrees and about 90 degrees with respect to the
bottom surface of the trench.
10. The turbine airfoil according to claim 1, wherein each trench
is substantially rectangular comprising at least one rounded or
chamfered top corner and at least one filleted internal corner.
11. A method of film cooling a turbine airfoil, the method
comprising: configuring a turbine airfoil with at least one shallow
trench having a lengthwise direction in a desired location; and
providing a plurality of film cooling holes within each trench
disposed therein as a single row, each film cooling hole having a
central axis oriented substantially in the lengthwise direction of
the corresponding trench such that film jets emanating from the
plurality of film cooling holes issue into the corresponding trench
substantially parallel to the lengthwise direction of the
corresponding trench.
12. The method according to claim 11, wherein at least one shallow
trench is disposed within a showerhead region of the turbine
airfoil.
13. The method according to claim 11, wherein at least one shallow
trench is disposed on a forward endwall region of the turbine
airfoil.
14. The method according to claim 11, wherein configuring a turbine
airfoil with at least one shallow trench comprises configuring the
depth of each shallow trench to be less than the average throat
diameter of the corresponding film cooling holes.
15. A film-cooled aerodynamic component comprising at least one
shallow trench having a length and a width, each trench comprising
a plurality of film holes disposed therein as a single row along
the lengthwise direction of the trench, each film hole angled
through the aerodynamic component substantially in the lengthwise
direction of the corresponding trench.
16. The film-cooled aerodynamic component according to claim 15,
further comprising: an aerodynamic component substrate; a bond
layer bonded to a surface of the aerodynamic component substrate;
and an overlying thermal barrier coating attached to the opposite
side of the bond layer, wherein the shallow trench penetrates the
bond layer and the overlying thermal barrier coating, and further
wherein each film hole penetrates the aerodynamic component
substrate.
17. The film-cooled aerodynamic component according to claim 15,
wherein the shallow trench further partially penetrates the
substrate.
18. The film-cooled aerodynamic component according to claim 15,
wherein at least one shallow trench is disposed within a showerhead
region of a turbine airfoil.
19. The film-cooled aerodynamic component according to claim 15,
wherein at least one shallow trench is disposed on a forward
endwall region of a turbine airfoil.
20. The film-cooled aerodynamic component according to claim 15,
wherein an angle between a central axis of each hole and the bottom
surface of its corresponding trench is between about 15 degrees and
about 50 degrees.
21. The film-cooled aerodynamic component according to claim 15,
wherein an angle between a central axis of each hole and the bottom
surface of its corresponding trench is between about 20 degrees and
about 35 degrees.
22. The film-cooled aerodynamic component according to claim 15,
wherein the depth of each shallow trench is less than the average
throat diameter of the corresponding film cooling holes.
23. The film-cooled aerodynamic component according to claim 15,
wherein each trench comprises a width substantially equal to the
maximum exit width of a corresponding film hole measured in the
direction as that which defines the trench width.
24. The film-cooled aerodynamic component according to claim 15,
wherein each trench comprises a width between about 1.0 and about
1.5 times the maximum exit footprint width of a corresponding film
hole.
25. The film-cooled aerodynamic component according to claim 15,
wherein each trench is substantially rectangular and comprises side
walls having an angle between about 70 degrees and about 90 degrees
with respect to the bottom surface of the trench.
26. The turbine airfoil according to claim 15, wherein each trench
is substantially rectangular comprising at least one rounded or
chamfered top corner and at least one filleted internal corner.
Description
BACKGROUND
[0001] The invention relates generally to film-cooled parts and
more particularly to a method of film cooling common locations on
virtually all cooled turbine airfoils.
[0002] Gas turbines and other high-temperature equipment use film
cooling extensively for effective protection of the hot gas path
components, such as turbine blades. Film cooling refers to a
technique for cooling a part in which cool air is discharged
through a plurality of small holes in the external walls of the
part to provide a relatively thin, cool layer or barrier along the
external surface of the part and prevent or reduce direct contact
with hot gasses.
[0003] Common locations employed to cool turbine airfoils include,
among others, the airfoil leading edge showerhead film and film
holes on forward endwall regions. One common cooling technique
utilizes rows of axially round holes inside a shallow trench in
which the axis of each hole is oriented substantially transverse to
the lengthwise direction of the trench. The use of a shallow trench
increases spreading of the film cooling, making the film cooling
less susceptible to freestream turbulence effects, and also
tolerant to effects due to deposits on the surface.
[0004] These known turbine airfoil film cooling techniques using
shallow trenches improve film cooling effectiveness over prior film
cooling techniques that employ film holes in the absence of shallow
trenches. It would be advantageous to provide a next generation of
turbine airfoil film cooling that improves film cooling
effectiveness beyond that achievable using known turbine airfoil
film cooling techniques that employ shallow trenches.
BRIEF DESCRIPTION
[0005] Briefly, in accordance with one embodiment, a turbine
airfoil is configured with at least one shallow trench, each trench
comprising a plurality of film holes disposed therein and located
along the lengthwise direction of the corresponding trench and
angled through a corresponding airfoil substrate substantially in
the lengthwise direction of the corresponding trench.
[0006] According to another embodiment, a method of film cooling a
turbine airfoil comprises:
[0007] configuring a turbine airfoil with at least one shallow
trench having a lengthwise direction in a desired location; and
[0008] providing a plurality of film cooling holes within each
trench, each film cooling hole having a central axis oriented
substantially in the lengthwise direction of the corresponding
trench such that film jets emanating from the plurality of film
cooling holes issue into the corresponding trench substantially
parallel to the lengthwise direction of the corresponding
trench.
[0009] According to yet another embodiment, a film-cooled
aerodynamic component comprises at least one shallow trench having
a length and a width, each trench comprising a plurality of film
holes disposed therein along the lengthwise direction of the
trench, each film hole angled through the aerodynamic component
substantially in the lengthwise direction of the corresponding
trench.
DRAWINGS
[0010] These and other features, aspects, and advantages of the
present invention will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0011] FIG. 1 is a perspective view illustrating a plurality of
film-cooling holes inside a shallow trench known in the art;
[0012] FIG. 2 illustrates the angular relationship between the
shallow trench walls and the central axis of a film-cooling hole
depicted in FIG. 1 depicting in further detail;
[0013] FIG. 3 is a perspective view illustrating film-cooling flow
due to lateral flow blockage for the film-cooling holes shown in
FIG. 1;
[0014] FIG. 4 is a perspective view illustrating a plurality of
film-cooling holes inside a shallow trench in which each hole
includes a central axis oriented in the lengthwise direction of the
trench according to one embodiment;
[0015] FIG. 5 illustrates a plurality of film-cooling holes inside
corresponding shall trenches applied to a showerhead film cooled
region of a turbine airfoil according to one embodiment;
[0016] FIG. 6 is an end view of the film-cooling holes depicted in
FIG. 4; and
[0017] FIG. 7 is a view transverse to the lengthwise direction of
the shallow trench depicted in FIGS. 4 and 6 showing another view
of the central axis of a film-cooling hole oriented in the
lengthwise direction of the trench.
[0018] While the above-identified drawing figures set forth
alternative embodiments, other embodiments of the present invention
are also contemplated, as noted in the discussion. In all cases,
this disclosure presents illustrated embodiments of the present
invention by way of representation and not limitation. Numerous
other modifications and embodiments can be devised by those skilled
in the art which fall within the scope and spirit of the principles
of this invention.
DETAILED DESCRIPTION
[0019] FIG. 1 is a perspective view of an airfoil part 10
illustrating a plurality of film-cooling holes 12 inside a shallow
trench 14 known in the art. Part 10 is cooled by a fluid coolant
passing through an interior of the part 10. The fluid coolant may
be compressor extraction air or another fluid having known
thermodynamic properties such as nitrogen. Some of the coolant
passes through film-cooling holes 12 to an exterior of part 10.
Part 10 may have several such shallow trenches, though only one is
shown here for purposes of illustration.
[0020] FIG. 2 illustrates an end view of the trench 14 depicted in
FIG. 1 showing the angular relationship between the shallow trench
14 side walls 16 and the central axis 18 of each film-cooling hole
12. Hot gases 30 shown in FIG. 3 flow in a direction transverse to
the lengthwise direction of channel 14. Coolant passes out through
film-cooling holes 12 in a direction substantially parallel to the
flow of the hot gases 30, spreads within the trench 14 prior to
coming out of the trench, and cooling airfoil part 10. Because the
central axis 18 of each film-cooling hole 12 forms an angular
relationship with the shallow trench 14 side walls 16, some of the
coolant exiting the film-cooling holes 12 are blocked or otherwise
restricted to prevent the maximum amount of coolant 32 from mixing
with the hot gases 30 to impede optimization of airfoil part
cooling. FIG. 3 is a perspective view illustrating film-cooling
flow 32 due to lateral flow blockage for the film-cooling holes 12
shown in FIG. 1.
[0021] FIG. 4 is a perspective view illustrating a plurality of
film-cooling holes 42 inside a shallow trench 14 located on an
airfoil part 40 in which each hole 42 includes a central axis 44
oriented in the lengthwise direction 46 of the trench 14 according
to one embodiment. Part 40 is cooled by a fluid coolant passing
through an interior of the part 40. The fluid coolant may be
compressor extraction air or another fluid having known
thermodynamic properties such as nitrogen. Some of the coolant
passes through film-cooling holes 12 to an exterior of part 40.
Part 40 may have several such shallow trenches, though only one is
shown here for purposes of illustration.
[0022] Hot gases may flow in any direction relative to the
lengthwise direction 46 of shallow trench 14, but the majority of
applications will have hot gases flowing substantially transverse
to the lengthwise direction 46 of shallow trench 14. Coolant passes
out through film-cooling holes 42 in a direction substantially
parallel to the lengthwise direction 46, filling the trench 14
prior to exiting the trench, and cooling airfoil part 40. Because
the central axis 44 of each film-cooling hole 42 is substantially
parallel with the shallow trench 14 side walls 16, substantially
all of the coolant exiting the film-cooling holes 42 is allowed to
fill in the length of the trench 14 and avoid immediate mixing with
the hot gases, thereby also exiting the trench 14 as a more
continuous cooling layer in the lengthwise direction 46 of airfoil
part 10 to maximize optimization of airfoil part 40 cooling.
[0023] FIG. 5 illustrates a plurality of film-cooling holes 42
inside corresponding shallow trenches 14 applied to a showerhead
film cooled region 50 of a turbine airfoil part according to one
embodiment. Each film-cooling hole 42 has a central axis oriented
substantially in the lengthwise direction 46 of the corresponding
shallow trench 14 and substantially parallel to the side walls 16
of the corresponding shallow trench 14.
[0024] FIG. 6 is an end view of the film-cooling holes 42 inside
the shallow trench 14 located on the airfoil part 40. A substrate
60 represents the wall of an airfoil part which requires cooling on
one or more surfaces, e.g., the wall of airfoil part 40 in FIG. 4.
The substrate 60 includes hot surface 62 and cooler surface 64.
Combustion gases enumerated 30 in FIG. 3 are conventionally
channeled over the airfoil part 40, i.e., over coated surface 73.
Coolant air 32 flows upwardly from the cooler surface through film
cooling holes 42. The holes have an average throat diameter 76.
Substrate 60 is partially coated with a bond layer 70 and an
overlying thermal bather coating (TBC) 72. In this embodiment,
shallow trench 14 is formed within the bond layer 70 and TBC 72,
and has a desired depth. Usually (but not always), the side-walls
16 of the shallow trench 14 are substantially perpendicular to
surface 62 of the substrate 60. (Thus, the side-walls 16 are
usually substantially perpendicular to the bottom surface 80 of
trench 14).
[0025] According to one embodiment, the centerline 44 of the film
cooling holes 42 is oriented between about 15 degrees and about 50
degrees relative to the bottom surface 80 of the trench 14
illustrated in FIG. 7. According to another embodiment, the
centerline of the film cooling holes 42 is oriented between about
20 degrees and about 35 degrees relative to the bottom surface 80
of the trench 14. The width of the trench 14 is substantially equal
to the maximum exit width of the film cooling hole 42 according to
one aspect of the invention. If a film cooling hole is perfectly
aligned in the lengthwise direction of its corresponding trench,
then the width is equal to the film cooling hole diameter for a
round hole. If the film cooling hole 42 is aligned somewhat off
angle, such as up to 20 degrees, then the width would be greater.
It shall be understood that the trench width can be greater than
the film hole exit and still work well to achieve the desired
cooling results according to the principles described herein,
whether the film hole is perfectly aligned or not. One embodiment
employs a trench width from about 1.0 to about 1.5 times the
maximum exit footprint width of its corresponding film cooling
holes 42. It shall also be understood that a trench 14 need not
have perfect square-edged features. Any one or more of the top
corners of the trench 14 can be somewhat rounded or chamfered, and
any one or more of the internal corners of the trench 14 can have
small fillets.
[0026] In some embodiments, the depth of the shallow trench 14 is
less than the average throat diameter of the film cooling holes 42.
In other embodiments, the depth of the shallow trench 14 is less
than about 50% of the average throat diameter of the film cooling
holes 42. These relative dimensions are in marked contrast to deep
slots often used in the prior art.
[0027] As shown in FIG. 6, trench 14 serves as a "spillway" trench
for coolant 32 exiting cooling holes 42. Side-walls 16 direct the
flow of the coolant 32. As a result, the coolant spreads into the
trench prior to exiting the trench along hot surface 73 (i.e.,
surface 62 as-coated). The coolant thus stays in close contact with
the hot surface, rather than separating from it quickly, as the
increased coolant spreading over the hot surface is now less
susceptible to freestream turbulence effects, and also is more
tolerant to effects due to deposits on the surface. This in turn
results in greater cooling effectiveness for the airfoil part 40 as
stated herein before.
[0028] FIG. 7 is a view transverse to the lengthwise direction 46
of the shallow trench 14 depicted in FIGS. 4 and 6 showing another
view of the central axis 44 of a film-cooling hole 42 oriented in
the lengthwise direction 46 of the trench 14.
[0029] In summary explanation, a structure and method is described
herein for improving film cooling for a variety of turbine airfoil
locations, including without limitation, the showerhead film and
the film holes on the forward endwall regions of a turbine airfoil.
Rows of film holes, or with holes oriented axially along the trench
width inside shallow trenches, are replaced by holes having
corresponding central axis oriented substantially in the lengthwise
direction of the corresponding trenches. The use of the shallow
trench increases spreading of the film cooling, making the film
cooling less susceptible to freestream turbulence effects, and also
more tolerant to effects due to deposits on the surface of the
turbine airfoil. It shall be understood that the embodiments
described herein are in no way restricted to use of round holes and
that many other hole shapes may be employed to provide the
advantages in accordance with the principles described herein.
[0030] The orientation of film holes, generally rows of film holes,
angled through the substrate but along the direction of the trench
rather than transverse to the direction of the trench (i.e.,
oriented along the trench width) cause the film jets to issue into
the trench without hitting the side walls or other obstructions.
The coolant flow more easily fills the trench before issuing onto
the external component aerodynamic surface as a nearly uniform
layer of film cooling. This structure is particularly beneficial
for rows of film holes that are otherwise constrained by
manufacturing to be oriented in fixed directions, such as
showerhead film rows that are radial, and also forward endwall film
rows that are circumferential (azimuthal). Film cooling hole
orientation along the length of the trench also benefits film rows
with greater spacing between the individual holes, since the trench
acts as a buffer region for coolant spreading before the coolant
interacts with the hot mainstream gases.
[0031] The shallow trench(s) can be formed in the protective
coatings of the component according to one embodiment. The shallow
trench(s) can be partially in the substrate according to another
embodiment. These embodiments improve film cooling effectiveness
for common airfoil locations that are constrained in geometry and
manufacturing. Such regions would not otherwise be able to employ
axially oriented film holes or even shaped film hole exits.
Particular embodiments were found to improve regional airfoil film
cooling by about 25% over that achievable with known structures.
The embodiments described herein provide an advantage in ability to
reduce total cooling flow for the turbine and increase efficiency
offered commercially.
[0032] It shall be understood that bond layers, also known as
bondcoats, as well as the TBC topcoats can be comprised of multiple
layers or compositions. The embodiments described herein are not to
be limited to a simple bondcoat and topcoat each of one composition
only. Exemplary products today use at least a two-layer bondcoat
system. Furthermore, the shallow trench might be formed only in the
topcoat, or into the bondcoat, or even into the substrate, since it
depends on the relative thicknesses used.
[0033] While only certain features of the invention have been
illustrated and described herein, many modifications and changes
will occur to those skilled in the art. It is, therefore, to be
understood that the appended claims are intended to cover all such
modifications and changes as fall within the true spirit of the
invention.
* * * * *