U.S. patent application number 09/863899 was filed with the patent office on 2002-01-10 for retention system and method for the blades of a rotary machine.
This patent application is currently assigned to General Electric Company. Invention is credited to Glynn, Christopher C., Pedersen, Poul D., Walker, Roger C..
Application Number | 20020004010 09/863899 |
Document ID | / |
Family ID | 23853514 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020004010 |
Kind Code |
A1 |
Pedersen, Poul D. ; et
al. |
January 10, 2002 |
Retention system and method for the blades of a rotary machine
Abstract
A retention system and method for the blades of a rotary machine
for preventing forward or aft axial movement of the rotor blades
includes a circumferential hub slot formed about a circumference of
the machine hub. The rotor blades have machined therein a blade
retention slot which is aligned with the circumferential hub slot
when the blades are received in correspondingly shaped openings in
the hub. At least one ring segment is secured in the blade
retention slots and the circumferential hub slot to retain the
blades from axial movement. A key assembly is used to secure the
ring segments in the aligned slots via a hook portion receiving the
ring segments and a threaded portion that is driven radially
outwardly by a nut. A cap may be provided to provide a redundant
back-up load path for the centrifugal loads on the key.
Alternatively, the key assembly may be formed in the blade
dovetail.
Inventors: |
Pedersen, Poul D.;
(Cincinnati, OH) ; Glynn, Christopher C.;
(Hamilton, OH) ; Walker, Roger C.; (Piedmont,
SC) |
Correspondence
Address: |
Nixon & Vanderhye P.C.
8th Floor
1100 N. Glebe Road
Arlington
VA
22201
US
|
Assignee: |
General Electric Company
|
Family ID: |
23853514 |
Appl. No.: |
09/863899 |
Filed: |
May 24, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09863899 |
May 24, 2001 |
|
|
|
09466900 |
Dec 20, 1999 |
|
|
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Current U.S.
Class: |
416/220R ;
29/889.21; 416/204A; 416/221 |
Current CPC
Class: |
Y10T 29/49321 20150115;
F01D 5/326 20130101 |
Class at
Publication: |
416/220.00R ;
416/204.00A; 416/221; 29/889.21 |
International
Class: |
B63H 001/20; F01D
005/32 |
Claims
What is claimed is:
1. A blade retention system for a rotating machine comprising: a
hub having a plurality of shaped, generally axially extending
openings at circumferentially spaced positions about the hub; a
plurality of blades having complimentary-shaped base portions
received in the openings, each of the blades having a blade
retention slot therein; a circumferential hub slot formed about a
circumference of the hub, wherein the blade retention slots are
substantially aligned with the circumferential hub slot when the
blades are received in the openings; and at least one ring segment
secured in the blade retention slots and the circumferential hub
slot.
2. A blade retention system according to claim 1, wherein the
circumferential hub slot is substantially U-shaped such that an
open end of the circumferential hub slot faces a center of the hub,
and wherein the blade retention slots are substantially U-shaped
such that open ends thereof face the center of the hub.
3. A blade retention system according to claim 1, wherein the at
least one ring segment extends 20-360.degree..
4. A blade retention system according to claim 3, wherein the at
least one ring segment extends 24.degree..
5. A blade retention system according to claim 3, wherein the at
least one ring segment extends 180.degree..
6. A blade retention system according to claim 1, further
comprising a key securing the ring segment in the blade retention
slots and the circumferential hub slot, the key comprising a hook
portion at one end of the key engageable with the ring segment and
a threaded portion at an opposite end of the key, wherein the blade
retention system further comprises a nut that is cooperatively
engageable with the threaded portion of the key.
7. A blade retention system according to claim 6, wherein the key
is disposed in a hole in the hub comprising a key receiving portion
of a first diameter that receives the key and a nut receiving
portion of a second diameter, larger than the first diameter to
thereby define a shoulder, that receives the nut, the nut being
supported by the shoulder to pull the key into locking engagement
with the ring segment.
8. A blade retention system according to claim 7, wherein an inside
diameter of the nut receiving portion is threaded, and wherein the
blade retention system further comprises a cap threaded into
engagement with the hole in the hub.
9. A blade retention system according to claim 6, wherein the key
is disposed in a hole in at least one of the complimentary-shaped
base portions of the blades.
10. A blade retention system for a rotating machine, wherein a
turbomachinery blade has a dovetail portion shaped to fit into a
complimentary-shaped opening in a hub for rotation about a hub
axis, the blade retention system comprising: a securing slot
defined by (1) a blade retention slot in the turbomachinery blade
and (2) a circumferential hub slot formed about a circumference of
the hub and substantially aligned with the blade retention slot
when the dovetail portion is fit into the complimentary-shaped
opening in the hub; and at least one ring segment engageable with
the securing slot to thereby retain the blade from axial
displacement.
11. A blade retention system according to claim 10, further
comprising at least one key engageable with the at least one ring
segment that secures the at least one ring segment in the securing
slot.
12. A blade retention system according to claim 11, wherein the key
comprises a hook portion at one end of the key engageable with the
ring segment and a threaded portion at an opposite end of the key,
and wherein the blade retention system further comprises a nut that
is cooperatively engageable with the threaded portion of the
key.
13. A blade retention system according to claim 12, wherein the key
is disposed in a hole in the hub comprising a key receiving portion
of a first diameter that receives the key and a nut receiving
portion of a second diameter, larger than the first diameter to
thereby define a shoulder, that receives the nut, the nut being
supported by the shoulder to pull the key into locking engagement
with the ring segment.
14. A blade retention system according to claim 13, wherein an
inside diameter of the nut receiving portion is threaded, and
wherein the blade retention system further comprises a cap threaded
into engagement with the hole in the hub.
15. A blade retention system according to claim 11, wherein the key
is disposed in a hole in the dovetail portion of the blade.
16. A method of retaining blades in a rotating machine having a hub
and a plurality of shaped, generally axially extending openings at
circumferentially spaced positions about the hub and a plurality of
blades having complimentary-shaped base portions received in the
openings, the method comprising: (a) machining a blade slot in each
of the plurality of blades; (b) machining a circumferential hub
slot about a circumference of the hub such that the blade retention
slots are substantially aligned with the circumferential hub slot
when the blades are received in the openings; (c) positioning the
blades in the openings; and (d) securing at least one ring segment
in the blade retention slots and the circumferential hub slot.
17. A method according to claim 16, wherein step (d) is practiced
by inserting at least one key having a key opening adjacent the
blade retention slots and the circumferential hub slot, fitting the
at least one ring segment into the key opening, and urging the key
toward the blade retention slots and the circumferential hub
slot.
18. A method according to claim 17, wherein step (d) is further
practiced by forming a hole in one of the hub or base portions of
the blades, and inserting the key into the hole prior to fitting
the at least one ring segment into the key opening.
19. A method according to claim 18, wherein step (d) is further
practiced by forming threads at an inside diameter of the hole and
threading a cap into the hole.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to turbo machinery rotor construction
and, more particularly, to structure for axially retaining the
rotor blades on the rotor disk of a turbo machine.
[0002] Turbo machinery such as high performance gas turbine engines
have a compressor and turbine that each includes one or more
annular banks or rows of axially spaced fixed stator vanes that are
positioned between rows of rotatable rotor blades. Each rotor blade
is formed with a rotor tip, an airfoil and a dovetail-shaped base
or root that mounts within a mating, generally axial slot formed
between adjacent dovetail posts on the web of the rotor disk.
[0003] In order to prevent axial movement of the rotor blades,
i.e., along the longitudinal axis of the rotor disk and engine, one
or more blade retainers are mounted adjacent the axial slots in the
rotor disk. Conventional retention systems, however, have
inadequate retention capabilities for gas turbines with large axial
aerodynamic loads on the blades caused by, for example, compressor
stalls, blade rubs, ingestion of objects, and the like.
BRIEF SUMMARY OF THE INVENTION
[0004] In an exemplary embodiment of the invention, a blade
retention system is provided for a rotating machine having a hub
with a plurality of shaped, generally axially extending openings at
circumferentially spaced positions about the hub. A plurality of
blades having complimentary-shaped base portions are received in
the openings, and each of the blades is provided with a blade
retention slot therein. A circumferential hub slot is formed about
a circumference of the hub, wherein the blade retention slots are
substantially aligned with the circumferential hub slot when the
blades are received in the openings. At least one ring segment is
secured in the blade retention slots and the circumferential hub
slot. The circumferential hub slot is preferably substantially
U-shaped such that an open end of the circumferential hub slot
faces a center of the hub, and the blade retention slots are
similarly substantially U-shaped such that open ends thereof face
the center of the hub. The ring segments preferably extend between
20.degree. and 360.degree. and preferably 24.degree. in one
embodiment and 180.degree. in another embodiment.
[0005] A key may be provided for securing the ring segment in the
blade retention slots and the circumferential hub slot. The key
includes a hook portion at one end of the key engageable with the
ring segment and a threaded portion at an opposite end of the key.
In this context, the blade retention system further includes a nut
that is cooperatively engageable with the threaded portion of the
key. The key is preferably disposed in a hole in the hub that
includes a key receiving portion of a first diameter that receives
the key and a nut receiving portion of a second diameter, larger
than the first diameter to thereby define a shoulder, that receives
the nut. The nut is structurally supported by the shoulder to pull
the key into locking engagement with the ring segment. An inside
diameter of the nut receiving portion may be threaded, and the
blade retention system may further include a cap threaded into
engagement with the hole in the hub. In an alternative arrangement,
the key is disposed in a hole in at least one of the
complimentary-shaped base portions of the blades.
[0006] In another exemplary embodiment of the invention, a blade
retention system is provided for a rotating machine including a
turbo machinery blade with a dovetail portion shaped to fit into a
complimentary-shaped opening in a hub for rotation about a hub
axis. The blade retention system includes a securing slot defined
by (1) a blade retention slot in the turbo machinery blade and (2)
a circumferential hub slot formed about a circumference of the hub
and substantially aligned with the blade retention slot when the
dovetail portion is fit into the complimentary-shaped opening in
the hub. The blade retention system also includes at least one ring
segment engageable with the securing slot to thereby retain the
blade from axial displacement.
[0007] In yet another exemplary embodiment of the invention, a
method of retaining blades in a rotating machine includes the steps
of (a) machining a blade slot in each of the plurality of blades,
(b) machining a circumferential hub slot about a circumference of
the hub such that the blade retention slots are substantially
aligned with the circumferential hub slot when the blades are
received in the openings, (c) positioning the blades in the
openings, and (d) securing at least one ring segment in the blade
retention slots and the circumferential hub slot. Step (d) may be
practiced by inserting at least one key having a key opening
adjacent the blade retention slots and the circumferential hub
slot, fitting the at least one ring segment into the key opening,
and urging the key toward the blade retention slots and the
circumferential hub slot. Step (d) may further be practiced by
forming a hole in one of the hub or base portions of the blades,
and inserting the key into the hole prior to fitting the ring
segment into the key opening. Step (d) may be still further
practiced by forming threads at an inside diameter of the hole and
threading the cap to the hole.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is an axial view of the retention system of the
invention;
[0009] FIG. 2 is a cross sectional view along line II-II in FIG.
1;
[0010] FIG. 3 is an axial view of an alternative embodiment
retention system of the invention;
[0011] FIG. 4 is a cross sectional view along line IV-IV in FIG.
3;
[0012] FIG. 5 is an axial view of another alternative embodiment
retention system of the invention; and
[0013] FIG. 6 is a cross sectional view along line VI-VI in FIG.
5.
DETAILED DESCRIPTION OF THE INVENTION
[0014] With reference to FIGS. 1 and 2, a hub 10 of a rotor or
other rotary machine is provided with dovetail or like-shaped
openings 12 for receiving a dovetail or base portion 14 of a turbo
machinery blade. The dovetail 14 and complimentary-shaped opening
12 in the hub 10 serve to retain the turbo machinery blades
radially. As noted, since the dovetails are oriented in an axial
direction, a retention system such as the retention system of the
present invention is required to prevent axial movement of the
blades. Typically, the dovetail axis forms an angle with the engine
centerline that ranges from 0.degree. to about 50.degree., and the
retention system of the invention is useful for the entire range of
dovetail angles.
[0015] The blade retention system of the invention includes a
circumferential groove or slot 16 machined or otherwise formed
about a circumference of the hub in the forward or aft face of the
rotor structure for the stage where axial retention is desired. The
circumferential hub slot 16 is preferably U-shaped such that an
open end thereof faces a center of the hub 10 as shown. A
correspondingly U-shaped blade retention slot 18 is machined or
otherwise formed in the dovetail portions 14 of the turbo machinery
blades. The blade retention slots 18 are similarly oriented such
that open ends thereof face the center of the hub 10. When the
dovetail portions 14 of the turbo machinery blades are fit into the
complimentary-shaped openings 12 in the hub 10, the blade retention
slots 18 are substantially aligned with the circumferential hub
slot 16 to define a securing slot 20 that spans the circumference
of the hub 10.
[0016] In order to axially retain the blades, at least one ring
segment 22 is secured in the aligned blade retention slots 18 and
circumferential hub slot 16, i.e., the securing slot 20.
Preferably, each ring segment 22 spans between 20.degree. and
360.degree. of the hub circumference. Of course, each blade must be
retained from axial movement such that, for example, with a rotor
incorporating fifteen blades evenly spaced about the circumference
thereof, a minimum of fifteen ring segments 22 would be required,
each spanning about 24.degree.. A typical rotor stage could include
up to 100 blades. In a preferred arrangement, however, the
retention system is provided with two ring segments 22, each
extending 180.degree..
[0017] In order to tighten and secure the ring segments 22 in the
securing slot 20, a key assembly 30 is provided for at least each
of the ring segments 22. (With longer ring segments, more than one
key assembly may be desirable.) The key assembly 30 includes a key
32 having a hook portion 34 at one end of the key, a key opening 36
at an intermediate portion of the key, and a threaded portion 38 at
an opposite end of the key. A hole is drilled in the hub with a
drill or the like of a first diameter to define a key receiving
portion 40. Subsequently, using a drill of a second diameter,
larger than the first diameter, a nut receiving portion 42 of the
hole is formed. Because the nut receiving portion 42 has a larger
diameter than the key receiving portion 40, a shoulder 44 is
defined in the hole.
[0018] In order to secure the ring segments 22 in the securing slot
20, after machining the circumferential hub slot 16 and the blade
retention slots 18 and after drilling the key receiving portion 40
and nut receiving portion 42, the key 32 is inserted into the hole
as far as possible into an extended key receiving area 40a. The
ring segments 22 are then placed over the hook portion 34 into the
key opening 36 of the key 32, partially within the securing slot
20., To facilitate placement of the ring segments 22, each ring
segment or at least each portion of the ring segments configured
for receiving a key assembly 30, is provided with a tab area 46
including a slot 48 to facilitate seating of the ring segments
22.
[0019] With this configuration, a nut 50 having internal threads is
inserted into the nut receiving portion 42 of the hole over the
threaded portion 38 of the key 32. As the nut 50 is rotated, once
supported by the shoulder 44, the key 32 is driven radially outward
(upward in FIG. 2) via the action of the threads, and the ring
segments 22 are brought into secure engagement within the securing
slot 20.
[0020] The ring segments 22 are preferably formed of a strong
material such as steel or nickel-steel, depending on the operating
temperature of the machine. The key 32 carries considerably less
load than the ring segments 22, and a preferred material for the
key 32 is titanium. Of course, those of ordinary skill in the art
will contemplate other materials that may be suitable for a
particular application, and the invention is not meant to be
limited to a specific material.
[0021] FIGS. 3 and 4 illustrate an alternative embodiment of the
present invention. In this embodiment, the threaded portion 38a of
the key 32 is slightly shorter than the threaded portion 38 in the
first embodiment. Additionally, the nut receiving hole 42a is
modified to incorporate internal threads. In this embodiment, in
order to provide a redundant back-up load path for centrifugal
loads on the key 32, a cap 52 is threaded into the nut receiving
hole 42a. Otherwise, the function configuration of the arrangement
in this embodiment is the same as that of the first embodiment, and
further description thereof will be omitted.
[0022] In still another alternative embodiment, referring to FIGS.
5 and 6, the hole previously formed in the rotor structure for the
key assembly is rather formed in the dovetail sections 14 of the
blades. In this embodiment, a modified key 32a is provided without
the threaded portion 38 but includes the key opening 36 and hook
portion 34. A key extension 54 is provided at a radially inward end
of the key 32a to secure the key 32a in the hole 53. That is,
during assembly, after inserting the ring segments 22 into the key
opening 36 of the key 32a, the key 32a is manually driven radially
outward or using a tool designed for this purpose, and the key
extension 54 is bent into the hole extension 40a to secure the key
and ring segments. This configuration provides an integrated
back-up load path for the key.
[0023] With the construction of the present invention, retainer
sections with high axial load capacity can be installed and removed
easily. Each retainer segment and its key assembly can be
configured to provide retention for one-half or fewer of the blades
in a stage. As such, a retainer section can be removed and
reinstalled without requiring access to the entire circumference of
the stage. Moreover, the system requires no machining between
stages in the axial direction, and installation and removal does
not require pin insertion, staking or bolting between stages in the
axial direction.
[0024] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention is not to be
limited to the disclosed embodiments, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *