U.S. patent application number 10/308409 was filed with the patent office on 2004-06-03 for device for defining a designated flow path through a dovetail slot in a gas turbine engine disk.
Invention is credited to Brunck, Michael Jay, Geverdt, Gerald Roger, Pan, Paul Yin-Pu.
Application Number | 20040106365 10/308409 |
Document ID | / |
Family ID | 32298089 |
Filed Date | 2004-06-03 |
United States Patent
Application |
20040106365 |
Kind Code |
A1 |
Pan, Paul Yin-Pu ; et
al. |
June 3, 2004 |
DEVICE FOR DEFINING A DESIGNATED FLOW PATH THROUGH A DOVETAIL SLOT
IN A GAS TURBINE ENGINE DISK
Abstract
A device for defining a designated flow path through a dovetail
slot in a gas turbine engine disk, wherein a longitudinal axis
extends through the dovetail slot. The device includes a first
portion having a bottom section contoured to form the flow path in
conjunction with a surface of a bottom portion of the dovetail slot
and a second portion shaped to be removably retained in a pressure
surface portion of the dovetail slot.
Inventors: |
Pan, Paul Yin-Pu;
(Cincinnati, OH) ; Geverdt, Gerald Roger;
(Cincinnati, OH) ; Brunck, Michael Jay;
(Cincinnati, OH) |
Correspondence
Address: |
JAMES P. DAVIDSON
10250 ALLIANCE ROAD
SUITE 120
CINCINNATI
OH
45242
US
|
Family ID: |
32298089 |
Appl. No.: |
10/308409 |
Filed: |
December 3, 2002 |
Current U.S.
Class: |
451/99 |
Current CPC
Class: |
B24C 3/327 20130101 |
Class at
Publication: |
451/099 |
International
Class: |
B24C 007/00 |
Claims
What is claimed is:
1. A device for defining a designated flow path through a dovetail
slot in a gas turbine engine disk, wherein a longitudinal axis
extends through said dovetail slot, comprising: (a) a first portion
having a bottom section contoured to form said flow path in
conjunction with a surface of a bottom portion of said dovetail
slot; and, (b) a second portion shaped to be removably retained in
a pressure face of said dovetail slot.
2. The device of claim 1, wherein a critical gap is maintained
between a surface of said bottom section for said first portion and
said surface of said dovetail slot bottom portion.
3. The device of claim 2, said critical gap being approximately
145-220 mils.
4. The device of claim 2, wherein said critical gap has a
cross-section in said flow path approximately 30-50% of a
cross-section at each end of said flow path.
5. The device of claim 1, wherein a surface of said bottom section
for said first portion is arcuate for at least a portion thereof
along said longitudinal axis through said dovetail slot.
6. The device of claim 5, wherein said arcuate portion of said
bottom section surface of said first portion has a predetermined
radius which is proportional to a minimum axial length of said
dovetail slot bottom portion in a range of approximately
1.0-1.5.
7. The device of claim 5, wherein said bottom section surface
includes a substantially planar portion at each end of said arcuate
portion.
8. The device of claim 1, wherein a surface of said bottom section
for said first portion is substantially symmetrical.
9. The device of claim 1, wherein a surface of said bottom section
for said first portion includes a non-linear, non-symmetrical
portion.
10. The device of claim 1, wherein a surface of said bottom section
for said first portion is arcuate in a direction substantially
perpendicular to said longitudinal axis through said dovetail
slot.
11. The device of claim 10, wherein said bottom section surface has
a designated radius in the circumferential direction which is
proportional to a radius for a surface of said dovetail slot bottom
portion in a range of approximately 1.2-1.8.
12. The device of claim 10, wherein a gap width between a surface
of said bottom section for said first portion and a surface of said
dovetail slot bottom portion at a midpoint in said flow path is
approximately 50-70% of a gap width therebetween at each end of
said flow path.
13. The device of claim 1, wherein a surface of said bottom section
for said first portion is substantially planar adjacent an aft end
thereof.
14. The device of claim 1, wherein a surface of said bottom section
for said first portion is substantially planar adjacent a forward
end thereof.
15. The device of claim 1, wherein sidewalls of said bottom section
of said first portion are tapered so as to avoid contact with side
surfaces of said dovetail slot bottom portion.
16. The device of claim 1, said bottom section of said first
portion having a designated radial height proportional to a radial
height of said dovetail slot bottom portion in a range of
approximately 0.75-0.90.
17. The device of claim 1, wherein said first portion is made of a
material having a hardness in a range of approximately 25-60 on the
Rockwell scale.
18. The device of claim 1, said first portion further comprising a
middle section extending from a top surface of said bottom
section.
19. The device of claim 18, wherein said middle section is
substantially planar and extends across at least a portion of said
bottom section top surface.
20. The device of claim 19, wherein said middle section includes at
least one opening formed therein.
21. The device of claim 20, said second portion including a
connecting portion which extends through said openings in said
middle section of said first portion.
22. The device of claim 18, said first portion further comprising a
top section oriented substantially perpendicular to said middle
section.
23. The device of claim 22, said top section including a recessed
portion along a top surface thereof.
24. The device of claim 1, wherein said second portion provides a
seal between said bottom portion and said pressure face portion of
said dovetail slot.
25. The device of claim 1, wherein said second portion is made of a
material having a hardness with a durometer reading in a range of
approximately D50-90 on the Shore scale.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to the repair of a
dovetail slot in a gas turbine engine disk and, more particularly,
to a device for defining a designated flow path through such
dovetail slot.
[0002] It has been found that heavily cold worked material and
other characteristics having the capability to reduce low cycle
fatigue in dovetail slots of gas turbine engine disks, and
particularly turbine disks which are rotated, may be caused during
generation of such dovetail slots. In particular, the disturbed
material may be caused by a dull broach tool during formation of
the dovetail slot. Conventional methods of removing such disturbed
material include milling the dovetail slot or to broach it again.
Each of these processes, however, are useful only so long as the
tools employed are sharp. Further, a hand deburr operation is
typically required, which inherently involves a high risk of
creating tool marks in the highly stressed dovetail area.
[0003] It is known in the art to utilize a flow of abrasive
material on surfaces of gas turbine engine components in order to
polish or provide surface finishing thereof. Such operations
involve removing only a minimal amount of material (e.g., on the
order of 0.0005 inch or 0.5 mil). An example of one such method is
disclosed in U.S. Pat. No. 6,183,347 to Shaw, where a stream of
pliant shot in a carrier fluid is discharged at a shallow angle of
incidence against a plug and an adjoining surface for selective
abrasion to provide a step. It will be appreciated therein that the
method described is for the selective surface treating of a
workpiece and does not involve the removal of material on the order
required to remove a disturbed layer of material or shallow
cracks.
[0004] While the aforementioned methods of removing disturbed
material from a gas turbine engine disk are useful for that
particular purpose, it would be desirable for such disturbed
material to be removed by an abrasive flow process which overcomes
the limitations noted above. It would also be desirable for a
device to be developed which defines a flow path through the
dovetail slot in a manner which permits substantially uniform
removal of the material in a surface on a bottom portion thereof
without affecting the pressure surface portion of the dovetail
slot.
BRIEF SUMMARY OF THE INVENTION
[0005] In an exemplary embodiment of the invention, a device for
defining a designated flow path through a dovetail slot in a gas
turbine engine disk is disclosed, wherein a longitudinal axis
extends through the dovetail slot. The device includes a first
portion having a bottom section contoured to form the flow path in
conjunction with a surface of a bottom portion of the dovetail slot
and a second portion shaped to be removably retained in a pressure
surface portion of the dovetail slot.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a cross-sectional view of a turbine disk
positioned within an abrasive flow fixture so as to remove material
along a bottom portion of the dovetail slots in accordance with the
present invention;
[0007] FIG. 2 is an enlarged, partial cross-sectional view of the
turbine disk positioned within the abrasive flow fixture as
depicted in FIG. 1;
[0008] FIG. 3 is an enlarged, side view of the flow path through a
bottom portion of the dovetail slot depicted in FIGS. 1 and 2;
[0009] FIG. 4 is an enlarged, front view of the flow path through a
bottom portion of the dovetail slot depicted in FIGS. 2 and 3;
[0010] FIG. 5 is a partial front view of a turbine disk having a
contoured pin member positioned within a dovetail slot in
preparation for removal of material along a bottom portion of such
dovetail slot;
[0011] FIG. 6 is a partial aft view of the turbine disk depicted in
FIG. 5;
[0012] FIG. 7 is a side perspective view of the contoured pin
member depicted in FIGS. 5 and 6, where an upper portion has been
deleted for clarity;
[0013] FIG. 8 is a side view of the contoured pin member depicted
in FIG. 7, where an upper portion has been deleted for clarity;
[0014] FIG. 9 is a front view of the contoured pin member depicted
in FIGS. 7 and 8, where an upper portion has been deleted for
clarity;
[0015] FIG. 10 is a side perspective view of the contoured pin
member depicted in FIGS. 7-9 with the upper portion included
thereon;
[0016] FIG. 11 is a side perspective view of a contoured pin having
an alternative configuration, where an upper portion has been
deleted for clarity;
[0017] FIG. 12 is a bottom perspective view of the contoured pin
having an alternative configuration depicted in FIG. 11, where an
upper portion has been deleted for clarity;
[0018] FIG. 13 is a side perspective view of the contoured pin
depicted in FIGS. 11 and 12 with an upper portion included thereon;
and,
[0019] FIG. 14 is a bottom perspective view of the contoured pin
depicted in FIGS. 11-13 with an upper portion included thereon.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Referring now to the drawings in detail, wherein identical
numerals indicate the same elements throughout the figures, FIG. 1
depicts a fixture 10 for applying an abrasive flow process to a
disk 12 of a gas turbine engine. An exemplary fixture is one known
by the name of Spectrum, which is made by Extrudehone Corp. of
Irwin, Pa. It will be understood that the abrasive flow process of
the present invention may be utilized with a disk of a turbine,
compressor or fan of such gas turbine engine, but that disk 12
depicted is a turbine disk. More specifically, disk 12 includes a
plurality of circumferentially spaced dovetail slots 14 formed in a
periphery thereof, each of which are located between adjacent posts
16 and provided to retain a turbine blade (not shown) having a
complementary dovetail section therein (see FIGS. 4-6). Each
dovetail slot 14 preferably has a shape generally like a fir tree
and includes a pressure face portion 18 and a bottom portion
20.
[0021] In order to remove a predetermined amount of material from a
surface 22 of each dovetail slot bottom portion 20, disk 12 is
positioned via a cradle 24 for abrasive flow fixture 10 so that an
abrasive media 26 is forced through each dovetail slot 14 as it
travels through a designated path 28. It will be noted from FIG. 1
that designated path 28 of abrasive flow fixture 10 preferably is
circumferential and includes a plurality of branches 30 which are
in flow communication with each dovetail slot 14 so that they all
may be worked substantially simultaneously. Abrasive media 26
utilized in fixture 10 includes a carrier, such as that identified
as model number 995L or 649S by Extrudehone, with grit included
therein preferably made of boron carbide, silicon carbide, or
industrial diamond. It will be appreciated that abrasive media 26
is forced under a predetermined pressure and flow rate (preferably
approximately 500-600 psi at approximately 3-5 cubic inches per
second, although the pressure may be higher or lower with a
corresponding decrease or increase in flow rate) from a lower
portion 34 of abrasive flow fixture 10 through designated path 28,
branches 30 and dovetail slots 14 into an upper portion 36 thereof
by a first cylinder (not shown). Thereafter, a second cylinder (not
shown) located adjacent upper portion 36 forces abrasive media 26
under the same predetermined pressure and flow rate back through
designated path 28, branches 30 and dovetail slots 14 in the
opposite direction to lower portion 34. It will be understood that
the travel of abrasive media 26 from lower portion 34 to upper
portion 36 and back to lower portion 34 constitutes one cycle as
that term is utilized herein.
[0022] With respect to each dovetail slot 14, a flow path 38 having
a longitudinal axis 40 (see FIG. 3) is defined through dovetail
slot bottom portion 20 which is in flow communication with
designated path 28 (as best seen in FIGS. 2-4). In order to define
flow path 38, a device in the form of a plug or pin member 42
having certain predetermined contours is preferably positioned
within each dovetail slot 14. It will be appreciated that flow path
38 does not generally have a uniform cross-section therethrough.
More specifically, a bottom surface 44 of pin member 42 includes a
substantially arcuate portion 46 for at least part of the axial
length thereof so that a variable cross-section exists for flow
path 38 along longitudinal axis 40. Arcuate portion 46 of bottom
surface 44 preferably has a designated radius 48 which is
proportional to a minimum axial length 50 of dovetail slot bottom
portion 22. A ratio of radius 48 to minimum axial length 50 is
preferably in a range of approximately 1.0-1.5 and more preferably
in a range of approximately 1.2-1.4.
[0023] It will also be seen that bottom surface 44 is preferably
arcuate in a circumferential direction (i.e., substantially
perpendicular to longitudinal axis 40) throughout arcuate portion
46 as best seen in FIG. 4. Accordingly, a circumferential radius 52
exists which is preferably proportional to a circumferential radius
54 for surface 22 of dovetail slot bottom portion 20. A ratio of
radius 52 to radius 54 is preferably in a range of approximately
1.2-1.8 and more preferably in a range of approximately
1.4-1.6.
[0024] Substantially planar portions 56 and 58 preferably exist on
bottom surface 44 at a forward end 60 and an aft end 62,
respectively, in order to mate with corresponding rabbets 64 and 66
formed on disk 12. Accordingly, it will be appreciated that while
planar portions 56 and 58 may not have equivalent axial lengths,
bottom surface 44 is substantially symmetrical thereacross. As seen
in an alternate configuration depicted in FIGS. 11-14, a pin member
142 may be utilized which has a non-linear, non-symmetrical bottom
surface 144 in order to have a desired amount of material removed
from bottom surface 22 of dovetail bottom portion 20.
[0025] A minimum cross-section known herein as a critical gap 68 is
preferably maintained in flow path 38 so as to ensure the proper
flow of abrasive media 26 therethrough. Critical gap 68 may also be
defined as a minimum distance between surface 22 of dovetail slot
bottom portion 20 and bottom surface 44 of pin member 42 or the
difference between a radial height 70 of pin member 42 and a radial
height 72 of dovetail slot bottom portion 20. Critical gap 68 is
generally located approximately at a midpoint 71 of flow path 38
and is approximately 50-70% of a gap width 69 at forward and aft
ends 60 and 62. The corresponding cross-section of flow path 38 at
midpoint 71 is therefore approximately 30-50% of the cross-section
at forward and aft ends 60 and 62.
[0026] Critical gap 68 generally is a function of several
parameters, including the material utilized for abrasive media 26,
the predetermined pressure and flow rate at which abrasive media 26
is forced through flow path 38, and the shape of flow path 38 from
both an axial and circumferential perspective. Nevertheless, it has
been found for the intended process of removing material from
surface 22 of dovetail slot bottom portion 20 that a ratio of
radial height 70 to radial height 72 preferably be in a range of
approximately 0.75-0.90 and more preferably in a range of
approximately 0.80-0.86. Consequently, critical gap 68 will
preferably be in a range of approximately 145-220 mils, more
preferably in a range of approximately 160-210 mils, and optimally
in a range of approximately 170-200 mils.
[0027] With respect to pin member 42, it will be appreciated that
it more specifically includes a first portion 74 which extends into
dovetail slot bottom portion 20 to define flow path 38 and a second
portion 76 which is removably retained in pressure face portion 18
of dovetail slot 14. First portion 74 has a bottom section 78 which
includes bottom surface 44 of pin member 42. A pair of tapered side
walls 80 and 82 are part of bottom section 78 and are configured so
as to avoid contact with side surfaces 84 and 86, respectively, of
dovetail slot bottom portion 20. A middle section 88 extends from a
top surface 90 of bottom section 78, is preferably substantially
planar in configuration, and has an axial length 92. Middle section
88 also preferably includes at least one opening 94 formed therein,
the purpose for which will be explained herein. It will be
understood that middle section 88 may have other configurations,
such as one or more cylinders extending from top surface 90 of
bottom section 78.
[0028] First portion 74 further includes a top section 96 oriented
substantially perpendicular to middle section 88 so that they
together preferably have a substantially T-shaped cross-section. A
recessed portion 98 is preferably formed in a top surface 100 of
top section 96 so that a gate used in the formation process is
provided. In particular, it will be understood that when first
portion 74 is formed, such as by investment casting using lost wax
process, a gate tail is able to be broken off easily without
concern for smoothness since any remaining portion thereof lies
beneath top surface 100. It will be appreciated that the material
utilized for first portion 74 is preferably an air-hardened tool
steel such as A2, D2 or ductile iron which is heat treated to
increase wearability. Other material which may be used for first
portion 74 includes cemented tungsten carbide which is molded and
sintered. In any case, it is preferred that the material of first
portion 74 have a hardness in a range of approximately 25-60 on the
Rockwell scale so that it is able to withstand the abrasion from
abrasive media 26 flowing through flow path 38.
[0029] Second portion 76 of pin member 42 has a substantially
dovetail shape so that it can be easily inserted into pressure face
portion 18 of dovetail slot 14 and pin member 42 retained in
position. Thus, a pair of grooved portions 77 and 79 are preferably
formed on each side thereof, as are a pair flared portions 81 and
83 interposed therewith. Second portion 76 also forms a seal
between pressure face portion 18 and bottom portion 20 of dovetail
slot, whereby abrasive media 26 is kept away from pressure surface
portion 18. Second portion 76 is generally formed via injection
molding and is intended to bond to first portion 74 as shown in
FIG. 10. A connector portion (not shown) may also be provided which
extends through openings 94 of first portion 74. Second portion 76
is preferably made of a softer material than first portion 74, such
as thermal setting plastic, nylon or urethane, providing it has a
hardness with a durometer reading on the Shore scale of
approximately D50-90. Accordingly, second portion 76 is able to
perform its intended retention and sealing functions without
scratching or otherwise marring pressure surface portion 18.
[0030] It will be noted that second portion 76 may include a step
85 located along a forward portion 60 of top surface 87 so as to
conform with a corresponding step 102 in each adjacent post 16 of
disk 12. This may also be utilized to confirm that each pin member
42 is properly inserted within dovetail slots 14 during assembly
into fixture 10.
[0031] It will be appreciated from the foregoing description of
abrasive flow fixture 10, pin member 42, and flow path 38 through
each dovetail slot 14 that a method of removing a predetermined
amount of material from surface 22 of each dovetail slot bottom
portion 20 in disk 12 includes the steps of configuring flow path
38 through each dovetail slot 14 and providing a flow of abrasive
media 26 through each flow path 38 for a designated number of
cycles so that a substantially uniform amount of material is
removed from a targeted area of each dovetail slot bottom portion
20. The method further includes the step of sealing pressure
surface portion 18 of each dovetail slot 14 from bottom portion 20
to prevent abrasive media 26 from flowing thereagainst. Both
functions are accomplished by inserting second portion 76 of pin
member 42 into each dovetail slot 14. By having pin member 42
contoured properly, areas of reduced cross-section are provided and
a minimum or critical gap 42 is maintained in each flow path
38.
[0032] It will be understood that the predetermined amount of
material removed from each surface 22 of dovetail slot bottom
portion 20 is preferably at least approximately 0.002 inches (2.0
mils), more preferably in a range of approximately 0.002-0.006
inches (2.0-6.0 mils), and optimally in a range of approximately
0.0025-0.0035 inches (2.5-3.5 mils). In order to determine the
designated number of cycles required by fixture 10 to remove the
predetermined amount of material from each dovetail slot bottom
portion, a depth of dovetail slot bottom portion 20, herein
referred to as radial height 72, is measured prior to providing
abrasive media 26 through flow path 38. After a given number of
cycles has been performed by fixture 10, the depth (radial height
72) of dovetail slot bottom portion 20 is again measured. This
process is repeated until the predetermined amount of material is
removed and the number of cycles required is recorded. Even after
the designated number of cycles is performed, it is preferred that
confirmation be made that at least the predetermined amount of
material has been removed. Dovetail slot bottom portion 20 for each
dovetail slot 14 may also be shot peened in order to enhance
surface 22 after the process of material removal has occurred.
[0033] Having shown and described the preferred embodiment of the
present invention, further adaptations of the abrasive flow fixture
10, flow path 38 through dovetail slot bottom portion 20, and/or
pin member 42 may be made and still be within the scope of the
invention. Moreover, steps in the method of removing a
predetermined amount of material from dovetail slot bottom portion
20 may be altered and still perform the intended function.
* * * * *