U.S. patent number 3,768,924 [Application Number 05/204,992] was granted by the patent office on 1973-10-30 for boltless blade and seal retainer.
This patent grant is currently assigned to General Electric Company. Invention is credited to Richard H. Andersen, Robert J. Corsmeier, Joseph W. Savage.
United States Patent |
3,768,924 |
Corsmeier , et al. |
October 30, 1973 |
BOLTLESS BLADE AND SEAL RETAINER
Abstract
A boltless blade retainer which provides a cooling air chamber
around the dovetail slots of a turbomachinery rotor is disclosed to
include a continuous annular ring which has a portion extending
radially outwardly therefrom to radially position the rotor blades
within the dovetail slots and to preclude axial movement of the
rotor blades within the dovetail slots. The blade retainer further
includes a plurality of tabs which fit between fingers which extend
from a face of the rotor disc near the rim thereof. The tabs and
fingers hook together in an interlocking manner which prevents
relative rotation of the blade retainer and the disc. After the
retainer is positioned on the disc, a split retaining ring is
installed under the hook-shaped disc fingers thus securing the
blade retainer to the disc. A rabbet is provided near the rim of
the rotor disc to support the retainer in the radial direction.
Inventors: |
Corsmeier; Robert J.
(Cincinnati, OH), Savage; Joseph W. (Cincinnati, OH),
Andersen; Richard H. (Cincinnati, OH) |
Assignee: |
General Electric Company
(Cincinnati, OH)
|
Family
ID: |
22760335 |
Appl.
No.: |
05/204,992 |
Filed: |
December 6, 1971 |
Current U.S.
Class: |
416/95;
416/220R |
Current CPC
Class: |
F01D
5/3015 (20130101); F01D 5/081 (20130101); Y02T
50/60 (20130101); Y02T 50/676 (20130101) |
Current International
Class: |
F01D
5/08 (20060101); F01D 5/00 (20060101); F01D
5/02 (20060101); F01D 5/30 (20060101); F01d
005/32 () |
Field of
Search: |
;416/219,220,221,92,96,97,95 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Powell, Jr.; Everette A.
Claims
Having thus described the invention, what is claimed as novel and
desired to be secured by Letters Patent of the United States
is:
1. A boltless blade retainer for a turbomachinery rotor which
includes a rotor disc having a plurality of blade dovetail slots
therein and a plurality of rotor blades positioned within the
slots, said blade retainer comprising:
a continuous annular ring,
means for securing said ring to a face of the rotor disc,
a leg extending radially outwardly from said ring, said leg
including means for radially positioning the rotor blades within
the dovetail slots and means for preventing axial movement of the
rotor blades within the slots, and
said leg defining a cooling air chamber around at least a portion
of the dovetail slots of the rotor disc.
2. A boltless blade retainer as recited in claim 1 wherein said
ring securing means include a plurality of tabs which extend
radially inwardly from said ring.
3. A boltless blade retainer as recited in claim 2 wherein said leg
further includes means for passing cooling air to said cooling air
chamber.
4. A boltless blade retainer as recited in claim 3 in combination
with a rotor disc, said rotor disc including a plurality of
hook-shaped fingers formed integrally therewith and extending from
the face of said disc, said fingers being spaced so as to receive
said blade retainer tabs therebetween.
5. The combination recited in claim 4 wherein said hook-shaped
fingers include a first portion extending axially from the face of
said disc and a second portion extending radially inwardly from
said first portion, said combination further including a locking
strip positioned between said tabs and said second portion of said
fingers.
6. The combination recited in claim 5 wherein said rotor disc
includes a rabbet located radially outwardly of said hook-shaped
fingers, and said blade retainer ring is positioned between said
rabbet and said fingers.
7. A combination as recited in claim 6 further including a
plurality of rotor blades positioned within the dovetail slots,
said blades including platforms forming the inner bounds of a gas
flow passage, said blade retainers being further characterized in
that said means for radially positioning said blades comprise an
enlarged head portion at the top of said blade retainer leg, and
said head portion lies beneath and supports said blade
platforms.
8. A turbomachinery rotor which includes at least one rotor disc
having a plurality of blade dovetail slots located in the rim
thereof, a rotor blade positioned within each of said blade
dovetail slots, and a boltless blade retainer, said blade retainer
comprising:
a continuous annular ring,
means for securing said ring to a face of said rotor disc,
a leg extending radially outwardly from said ring, said leg
including means for radially positioning said rotor blades within
said dovetail slots and means for preventing axial movement of said
rotor blades within said slots, and
said leg defining a cooling air chamber around at least a portion
of said dovetail slots of said rotor disc.
9. A turbomachinery rotor as recited in claim 8 wherein said blade
retainer is further characterized in that said means for securing
said blade retainer ring to a face of said rotor disc includes a
plurality of tabs which extend radially inwardly from said blade
retainer ring.
10. A turbomachinery rotor as recited in claim 9 wherein said blade
retainer leg further includes means for passing cooling air to said
cooling air chamber.
11. A turbomachinery rotor as recited in claim 10 wherein said
rotor disc includes a plurality of hook-shaped fingers formed
integrally therewith and extending from a face thereof, said
fingers being spaced so as to receive said blade retainer tabs
therebetween.
12. A turbomachinery rotor as recited in claim 11 including a
second blade retainer, said first blade retainer being secured to a
first face of said rotor disc and said second blade retainer being
secured to the opposite face of said rotor disc.
13. A turbomachinery rotor as recited in claim 12 wherein said
second blade retainer comprises:
a continuous annular ring,
means for securing said ring to a face of the rotor disc,
a leg extending radially outwardly from said ring, said leg
including means for radially positioning the rotor blades within
the dovetail slots and means for preventing axial movement of the
rotor blades within the slots, and
said leg defining a cooling air chamber around at least a portion
of the dovetail slots of the rotor disc.
14. A turbomachinery rotor as recited in claim 12 including a first
locking strip positioned between said blade retainer tabs and said
hooked-shaped fingers of said first face, and a second locking
strip positioned between said blade retainer tabs of said second
blade retainer and hook-shaped fingers formed integrally with and
extending from said opposite face of said rotor disc.
Description
Background of the Invention
This invention relates generally to turbomachinery rotor
construction and, more particularly, to improved structure for
retaining and positioning rotor blades on a turbomachinery rotor
disc.
The invention herein described was made in the course of or under a
contract, or a subcontract thereunder, with the United States
Department of the Air Force.
In high performance gas turbine engines, the temperature of the hot
gas stream, which is generated within a combustion section, exceeds
the operating temperature capabilities of any practical material
from which the turbine vanes and blades could be fabricated. In
order to reduce the metal temperatures to a point where sufficient
strength is maintained, it has become an accepted practice to duct
lower temperature, pressurized air from the engine's compressor to
the turbine components which operate in the hot gas stream
environment.
The cooling air thus derived is employed in various ways to reduce
the metal temperatures of such components. As a general rule, this
cooling air is introduced into hollow blades or vanes and then
discharged into the hot gas stream. This cooling air reduces the
component metal temperatures through various heat transfer
mechanisms, such as convective, impingement, or film cooling
action. To enhance the cooling, the interior of rotating blades and
stationary vanes may be equipped with inserts having a large number
of small holes provided therein through which air is impinged on
the interior surfaces of the blades or vanes.
The provision of such inserts for impingement cooling of static
vanes is relatively straightforward from an assembly standpoint.
However, in rotating components, and particularly in the blades of
turbine rotors, great difficulties may be encountered in attempting
to provide such inserts. The problem is further complicated when
one considers that the cooling air must be delivered to the
interiors of the rotor blades while these blades are rotating at
extremely high speeds. To overcome these problems, a number of
designs have evolved in recent years. One such design which has
proven successful is shown and claimed in U.S. Pat. No. 3,715,170,
issued Feb. 6, 1973 in the name of J. W. Savage et al., and
assigned to the same assignee as the present invention.
As described in the Savage et al. application, a turbine blade is
provided having a thin-walled, cambered airfoil portion, and a
single, circular arc dovetail formed integrally therewith.
Impingement inserts extend outwardly from and through radial
passageways formed in the dovetail into the cavity of the airfoil
portion. The inserts are insertable through this passageway and
include a multiplicity of holes directed toward internal surfaces
of the airfoil portion. An inlet opening at the bottom end of the
insert admits cooling air which is discharged from the insert holes
to impinge the airfoil surfaces and cool the same. As further shown
in the Savage et al. application, the impingement inserts are
maintained in place by means of a hollow spacer which fits within
the dovetail slot of the rotor disc beneath the blade dovetail.
This spacer is supplied with cooling air by means of a passageway
formed along the surface of the rotor disc. As also shown in the
application, the turbine rotor blades are prevented from axial
movement within the dovetail slots by means of annular plates
secured to the upstream and downstream sides of the rotor discs by
a plurality of bolts. The upstream plate further helps to form the
flow path for delivery of the cooling air to the spacers beneath
the blade dovetails.
The use of a plurality of bolts to secure the annular plates to the
upstream and downstream sides of the rotor disc presents certain
disadvantages, however, in that any protrusion from the rotating
disc causes windage within the chamber partially formed by the
rotor disc side walls. This windage not only increases the
temperature of the air within the chamber but also adds to the
overall drag on the turbine rotor, both of which reduce engine
performance. The use of bolts causes an additional problem in that
bolt holes located within the rotor disc increase the rim loading
and result in stress concentration areas. To help overcome these
problems, designers normally call for a large number of small bolts
to be equally spaced around the rim of the turbine disc. This large
number of bolts, of course, adds both to the weight of the engine
and to the time required for assembly or disassembly.
The use of the spacers beneath the blade dovetails to radially
position the blades and to provide space for the delivery of
cooling air to the inserts somewhat complicates assembly procedures
and adds to the time required for assembly. The spacers themselves
also add to the overall materials cost of the engine. Therefore, if
the spacers could be eliminated, the cost of the turbine rotor
assembly would decrease.
It is desirable, therefore, to provide a blade retainer design
which includes provisions for not only retaining but also for
radially positioning the rotor blades within the dovetail slots and
further includes provision for delivery of cooling air to the blade
dovetails without the requirement for a number of bolts extending
from either the upstream or downstream sides of the turbine rotor
discs.
Boltless blade retainers per se are not new. For example, it is
known to provide mating grooves in a lip extending from the rim of
a turbine rotor disc and in the blade dovetails. A locking wire is
then positioned within the groove thereby precluding axial movement
of the dovetails within the dovetail slots. An example of this type
of design is shown in U.S. Pat. No. 2,713,991 -- Secord et al.
Designs similar to this, however, are concerned merely with
precluding axial movement of the blades and not with providing
cooling air to the blade nor with connecting a sealing member of
any type to the rotor disc.
It is further known to provide individual cover plates for each
rotor blade, which plates serve not only to retain the blades
within the dovetail slots but also to block off the gas flow
between elongated blade shanks or to serve as gas seals with
adjacent stationary members of the turbine. Such a design is shown
in U.S. Pat. No. 3,137,478 -- Farrell. These designs also are not
concerned with providing cooling flow to the turbine dovetails,
dovertails, and the potential leakage between the individual cover
plates would appear to preclude their use in such a manner.
Furthermore, the problems associated with assembling a design which
requires two separate cover plates for each individual turbine
blade hardly need mentioning.
SUMMARY OF THE INVENTION
It is a primary object of this invention, therefore, to provide a
boltless blade retainer for turbomachinery rotor blades which
includes provisions for the delivery of cooling air to the blade
dovetail area.
It is a further object of this invention to provide such a retainer
which includes provisions for radially positioning the rotor blades
and for connecting ring-type parts such as seals, retainers, etc.
to a rotor disc.
Briefly stated, the above and similarly related objects are
achieved providing a turbomachinery rotor in which a rotor disc
includes a series of equally spaced, hook-shaped fingers near the
rim thereof. A continuous, annular ring blade retainer is designed
to include a plurality of tabs which fit between the rotor disc
fingers in an interlocking manner which prevents relative rotation
between the blade retainer and the disc. After the retainer is
positioned on the disc, a split retaining ring is installed under
the hook-shaped disc fingers, thus securing the blade retainer to
the disc. A rabbet is provided near the rim of the rotor disc to
support the retainer in the radial direction.
Other preferred features are found in sizing the blade retainer
such that a portion thereof rests beneath the platforms of the
rotor blades and prevents the blades from dropping down into the
dovetail slots when the turbomachinery is stationary. Safety stops
are provided integrally with the blade retainer to preclude bending
of the rotor disc fingers beyond their yield point during
operation. In addition, a lip on the blade retainer tabs is
provided to secure the retaining ring should it break or become
weak and attempt to fall out when the engine is idle. An
installation stop is provided to preclude the blade retainer tabs
from being bent beyond their yield points during assembly or
disassembly thereof. Finally, shoulders are provided on the
retaining ring to enable assembly and disassembly of the overall
structure.
DESCRIPTION OF THE DRAWINGS
While the specification concludes with a series of claims which
distinctly claim and particularly point out the subject matter
which Applicants regard to be their invention, a complete
understanding of the invention will be gained from the following
detailed description, given in connection with the accompanying
drawing, in which:
FIG. 1 is a fragmentary, generally longitudinal section through a
turbine rotor and blade embodying the present invention;
FIG. 2 is an enlarged sectional view showing a portion of FIG. 1;
and
FIG. 3 is a fragmentary, axial section taken in the direction of
line 3--3 of FIG. 2.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to the drawings wherein like numerals correspond to
like elements throughout, reference is directed initially to FIGS.
1 and 3 wherein a turbine rotor disc 10 is illustrated as having
radially projecting turbine blades 12 mounted in a circumferential
row thereon. Each blade comprises a cambered airfoil portion 14
which projects into the hot gas stream of the turbine as is well
known in the art. A platform 16 is provided at the base of each
airfoil portion to compositely define the inner bounds of the hot
gas flow through the blade row. A tang 18 extends inwardly of the
platform 16 to attach the blade to the rotor disc 10.
The tangs 18 are of the single dovetail, circular arc type and are
preferably formed with their opposite sides defined by radii formed
from different centers as taught in U.S. Pat. No. 3,378,230, which
is of common assignment with the present application. The disc 10
has correspondingly shaped dovetail slots 20 formed across its
circumferential face, which slots receive the tangs to mount the
blades 12 to the disc 10.
The slots 20 have a depth greater than the dovetail height of the
tangs 18 to facilitate insertion of the tangs therein and to
facilitate delivery of cooling air to the tangs 18 in a manner to
be discussed. Since the dovetail slots 20 and the dovetail tangs 18
are not respectively formed on radii swung from a common center,
the tangs must be inserted in the lower portion of the slots and
then shifted radially outwardly to lock the blades in place. The
blades 12 are held in this radial position by boltless blade
retainers 22 and 24 located on the upstream and downstream faces of
the turbine rotor disc 10, respectively.
The space between the bottom of the tangs 18 and the bottom of the
dovetail slots 20 is generally designated by the numeral 26 (FIGS.
2 and 3) and is supplied with cooling air by means of a plurality
of holes 28 formed in the upstream blade retainer 22. As shown in
FIG. 1, the cooling air is delivered to the dovetail slots 20 (or
the space 26) from the compressor (not shown) by a passageway 30,
which includes a stationary expander nozzle 32 to further cool the
air as is well known in the art. Air flows through the expander 32
into a chamber 34 formed by the upstream face of the turbine rotor
disc 10, a second rotating disc 36, and the upstream blade retainer
22. The disc 36 is coupled for rotation with the turbine rotor disc
10 by means of a plurality of bolts 38.
The cooling air flows from the expander nozzle 32 into the chamber
34 through a plurality of holes 40 formed within the disc 36. This
cooling air then flows from the chamber 34 through the holes 28 in
the upstream blade retainer 22 and into the space 26 within the
dovetail slots 20. From the slots 20 the air is delivered to the
interior portions of the blades 12 in any known manner. In the
present example, the air is delivered through a plurality of
passages 42 formed within the dovetail tangs 18. As previously
mentioned, the passages 42 may be equipped with impingement inserts
(not shown) to enhance the cooling capabilities. These inserts
could be held in place by a slight interference fit between the
insert and the passage 42; and the spacers shown in the Savage et
al application could be eliminated, thus further simplifying and
reducing the cost of the rotor.
As discussed above, the blades 12 are held in their desired radial
position within the dovetail slots 20 by means of the blade
retainers 22 and 24 (thus permitting removal of the spacers). When
assembled, the blade retainers 22 and 24 not only provide this
function but also preclude axial movement of the blades 12 within
the dovetail slots 20 and, furthermore, provide a sealed cooling
air chamber around the dovetail slots and blade tangs, as will now
be described. (For clarity, the following description will be
limited to that necessary to describe the upstream blade retainer
22 in that the basic structure of the retainer 22 and retainer 24
is similar.)
The blade retainer 22 is comprised basically of a continuous,
annular ring 44 (FIG. 2) having a leg 46 extending radially
outwardly therefrom and a plurality of tabs 48 extending radially
inwardly therefrom, as shown in FIGS. 2 and 3. The tabs 48 fit
between a plurality of equally spaced, hook-shaped fingers 50 which
are formed integrally with and extend from the turbine rotor disc
10. When assembled as shown in FIGS. 2 and 3, the tabs 48 and the
fingers 50 provide an interlock which prevents the retainer 22 from
rotating with respect to the disc 10. As further shown in FIG. 2,
the leg 46 is provided with means for radially positioning the
blades 12 within the dovetail slots 20. For this purpose, the top
of the leg 46 includes an enlarged head portion 52 upon which the
blade platform 16 rests. In this manner, the blades 12 are
prevented from moving radially inwardly when the rotor disc 10 is
stationary.
As previously described, the blade retainer 22 cooperates with the
rotor disc 10 and the disc 36 to form the chamber 34. For this
reason the retainer 22 includes a conical arm 54 which mates with a
rim 56 of the disc 36 as shown in FIGS. 1 and 2. If desirable, a
suitable seal 58 can be provided between the conical arm 54 and the
disc rim 56. Located between the enlarged head portion 52 and the
conical arm 54 of the retainer 22 is a seal tooth 60 which
cooperates with a stationary sealing member 62 to prevent leakage
of the hot gas stream into a chamber 64 (FIG. 1).
As shown most clearly in FIGS. 2 and 3, the radial leg 46 of the
blade retainer 22 includes a plurality of the cooling air holes 28,
previously discussed, which permit the delivery of cooling air from
the chamber 34 to the spaces 26 within the dovetail slots 20. If
desirable, a second row of cooling air holes 66 can be positioned
radially outwardly from the cooling air holes 28 as shown in FIG. 2
to deliver cooling air from the chamber 64 to the rim of the
turbine rotor disc 10. In an alternative design, the cooling air
holes 66 can be eliminated and any necessary cooling air for the
turbine rotor disc rim can be allowed to leak between a projection
68 (FIG. 2), which abuts the face of the turbine rotor blade
shanks, and the turbine rotor disc rim. If necessary, radial slots
(not shown) could be formed in the projection 68 to meter a proper
amount of cooling air to the rim area. In either case, the
projection 68 provides the basic function of preventing axial
movement of the blades 12 within the dovetail slots 20 when the
rotor assembly is complete.
As further shown in the drawings, the ring portion 44 of the blade
retainer 22 fits between the hook-shaped fingers 50 of the turbine
rotor disc 10 and a continuous, annular rabbet 70 formed integrally
with the rotor disc 10. The rabbet 70 is provided to support the
retainer 22 radial load. After the retainer 22 is positioned on the
disc 10, a split retaining ring 72 is installed between the
hook-shaped fingers 50 and the tabs 48. In this manner, the
retainer 22 is completely secured to the disc 10. The ring 72 is
split in at least one location, as shown at 74 (FIG. 3) to permit
assembly thereof. When assembled as shown in FIGS. 2 and 3, the
ring 72 is captured between the hook-shaped fingers 50 and a
projecting lip 76 formed integrally with the tabs 48. In this
manner, the ring 72 is secured should it break or become weak and
attempt to fall out when the engine is stationary.
An overspeed safety stop is incorporated in the design to prevent
the hook-shaped fingers 50 from being bent beyond their yield
points during operation of the rotor disc 10. This overspeed safety
stop is provided by holding a close clearance between the inner
diameter of the ring portion 44 of the retainer 22 and the outer
diameter of the fingers 50 at location 80 (FIG. 2). Critical loads
which would otherwise occur in the fingers 50 are thus transferred
directly to the rabbets 70 of the disc 10.
In assembling the turbine rotor as shown in the drawings, the
retainer tabs 48 are indexed between the disc fingers 50. The
retainers are pushed axially onto the disc until projection 68
contacts the disc 10. A simple installation tool is then used to
push the tabs 48 toward the rotor disc 10. The split ring 72 is
then positioned between the fingers 50 and the tabs 48, and the
tabs 48 are permitted to return to their normal position thus
securing the ring 72 as described above. A shoulder 84 is formed
integrally with the tabs 48 to preclude the tabs 48 from being bent
beyond their yield points during assembly. Once assembly of the
blade retainer 22 is completed, the rotor blades 12 are positioned
within the dovetail slot 20 and the blade retainer 24 is then
assembled on the opposite side of the rotor disc 10 in a manner
similar to that described above for the blade retainer 22.
Disassembly of the rotor is accomplished by merely reversing the
above-described steps. Shoulders 82 and 83 are provided for pulling
the retainers off the disc.
When assembled as described above, the blade retainers 22 and 24
secure the blades 12 in their desired radial positions and preclude
axial movement of the blades 12 within the dovetail slots 20. In
addition, the blade retainers 22 and 24 provide a sealed chamber
around the bottom of the dovetail slots for the delivery of cooling
air thereto in the manner described above. This sealed chamber is
provided by the close fit between the projecting portions 68 of the
retainers and the rim of the rotor disc 10 and, furthermore, by the
continuous seal between the ring portion 44 and the rabbets 70.
The construction shown in the drawings and described above provides
a number of advantages over previously used retainer systems. For
example, the large number of bolts normally associated with
attaching blade retainers to the upstream and downstream sides of
the turbine rotor disc have been eliminated. This significantly
reduces the number of parts involved, and thus the time associated
with assembly of the turbine rotor. The elimination of the bolts
also provides for a much lighter weight rotor not only because of
the elimination of the bolts and nuts but also because the rim of
the rotor disc 10 need not be as thick due to elimination of
possible stress concentration areas associated with bolt holes.
Finally, the elimination of the bolts reduces windage losses which
could occur on both sides of the turbine rotor disc. These windage
losses not only increase the temperature of the cooling air but
also cause added work to be done by the turbine rotor, thereby
decreasing the overall efficiency of the engine.
From the preceding discussion it will be apparent that deviations
from the preferred embodiments described will occur to those
skilled in the art. For example, the disclosed structure could
easily be modified to provide for the attachment of any ring type
part, such as a seal or cover plate, to a comparable mating part
such as a rotor disc or rotor shaft or even to a stationary member
such as a frame within a gas turbine engine. The spirit and scope
of the present invention are therefore to be derived fully from the
appended claims.
* * * * *