U.S. patent application number 09/747873 was filed with the patent office on 2002-06-27 for bolted joint for rotor disks and method of reducing thermal gradients therein.
Invention is credited to Dix, Brian Edward, Hooper, Tyler Frederick, Pepi, Jason Francis.
Application Number | 20020081192 09/747873 |
Document ID | / |
Family ID | 25007019 |
Filed Date | 2002-06-27 |
United States Patent
Application |
20020081192 |
Kind Code |
A1 |
Pepi, Jason Francis ; et
al. |
June 27, 2002 |
BOLTED JOINT FOR ROTOR DISKS AND METHOD OF REDUCING THERMAL
GRADIENTS THEREIN
Abstract
Bolt hole stress in rotor disks having bolted joints is reduced
by passing relatively hot secondary flow path air (such as
compressor discharge air) through each bolt hole to heat the disk
from inside the bolt hole. In doing so, the temperature
distribution in the area of the bolt hole is made more uniform and
the stress is dramatically reduced. The bolted joint includes a
bolt hole formed in a first rotor disk and a bolt disposed in the
bolt hole such that a channel is defined between the bolt and the
bolt hole. A first nut or abutment is attached to a first end of
the bolt, and a second nut or abutment is attached to a second end
of the bolt. A first passage associated with the first abutment
provides fluid communication with the channel, and a second passage
associated with the second abutment provides fluid communication
with the channel, thereby allowing the relatively hot fluid to pass
through the channel during engine operation.
Inventors: |
Pepi, Jason Francis;
(Tewksbury, MA) ; Dix, Brian Edward; (Ipswich,
MA) ; Hooper, Tyler Frederick; (Haverhill,
MA) |
Correspondence
Address: |
PATRICK R. SCANLON
PIERCE ATWOOD
ONE MONUMENT SQUARE
PORTLAND
ME
04101
US
|
Family ID: |
25007019 |
Appl. No.: |
09/747873 |
Filed: |
December 22, 2000 |
Current U.S.
Class: |
415/115 ;
416/96R; 416/97R |
Current CPC
Class: |
F16B 5/0275 20130101;
F16B 35/041 20130101; F16B 39/01 20130101 |
Class at
Publication: |
415/115 ;
416/96.00R; 416/97.00R |
International
Class: |
F01D 005/08 |
Claims
What is claimed is:
1. A bolted joint for connecting first and second components, said
bolted joint comprising: a bolt hole formed in said first
component; a bolt disposed in said bolt hole, wherein a channel is
defined between said bolt and said bolt hole; a first abutment
attached to a first end of said bolt, said first abutment defining
a first passage in fluid communication with said channel; and a
second abutment attached to a second end of said bolt, said second
abutment defining a second passage in fluid communication with said
channel.
2. The bolted joint of claim 1 wherein said first abutment
comprises a first nut threadingly received on said first end of
said bolt, said first passage being formed in said first nut, and
said second abutment comprises a second nut threadingly received on
said second end of said bolt, said second passage being formed in
said second nut.
3. The bolted joint of claim 1 wherein said first abutment
comprises a head integrally formed on said first end of said bolt
and a first spacer disposed on said bolt adjacent to said head,
said first passage being formed in said first spacer, and said
second abutment comprises a nut threadingly received on said second
end of said bolt and a second spacer disposed on said bolt adjacent
to said nut, said second passage being formed in said second
spacer.
4. The bolted joint of claim 1 wherein said first abutment
comprises a first nut threadingly received on said first end of
said bolt and a first spacer disposed on said bolt adjacent to said
first nut, said first passage being formed in said first spacer,
and said second abutment comprises a second nut threadingly
received on said second end of said bolt and a second spacer
disposed on said bolt adjacent to said second nut, said second
passage being formed in said second spacer.
5. The bolted joint of claim 1 wherein said first passage comprises
a first groove formed in bolted structure adjacent to said first
abutment and said second passage comprises a second groove formed
in bolted structure adjacent to said second abutment.
6. The bolted joint of claim 1 wherein said bolt has at least one
raised shoulder formed thereon for engaging said bolt hole, said
raised shoulder having at least one flat formed thereon for
allowing fluid passage through said channel.
7. The bolted joint of claim 1 further comprising a retention lip
formed on said bolt and abutting said second component.
8. In a gas turbine engine comprising a first rotor disk, a second
rotor disk, a first cavity adjacent to said first rotor disk, and a
second cavity adjacent to said second rotor disk, a bolted joint
for connecting said first and second rotor disks, said bolted joint
comprising: a bolt hole formed in said first rotor disk; a bolt
disposed in said bolt hole, wherein a channel is defined between
said bolt and said bolt hole; a first abutment attached to a first
end of said bolt; a second abutment attached to a second end of
said bolt; a first passage providing fluid communication between
said first cavity and said channel; and a second passage providing
fluid communication between said second cavity and said
channel.
9. The bolted joint of claim 8 wherein said first abutment
comprises a first nut threadingly received on said first end of
said bolt, said first passage being formed in said first nut, and
said second abutment comprises a second nut threadingly received on
said second end of said bolt, said second passage being formed in
said second nut.
10. The bolted joint of claim 8 wherein said first abutment
comprises a head integrally formed on said first end of said bolt
and a first spacer disposed on said bolt adjacent to said head,
said first passage being formed in said first spacer, and said
second abutment comprises a nut threadingly received on said second
end of said bolt and a second spacer disposed on said bolt adjacent
to said nut, said second passage being formed in said second
spacer.
11. The bolted joint of claim 8 wherein said first abutment
comprises a first nut threadingly received on said first end of
said bolt and a first spacer disposed on said bolt adjacent to said
first nut, said first passage being formed in said first spacer,
and said second abutment comprises a second nut threadingly
received on said second end of said bolt and a second spacer
disposed on said bolt adjacent to said second nut, said second
passage being formed in said second spacer.
12. The bolted joint of claim 8 wherein said first passage
comprises a first groove formed in bolted structure adjacent to
said first abutment and said second passage comprises a second
groove formed in bolted structure adjacent to said second
abutment.
13. The bolted joint of claim 8 wherein said bolt has at least one
raised shoulder formed thereon for engaging said bolt hole, said
raised shoulder having at least one flat formed thereon for
allowing fluid passage through said channel.
14. The bolted joint of claim 8 further comprising a retention lip
formed on said bolt and abutting said second rotor disk.
15. In a gas turbine engine having a bolted joint for connecting a
first rotor disk and a second rotor disk wherein said bolted joint
includes a bolt disposed in a bolt hole formed in said first rotor
disk, a method of reducing thermal gradients in said first rotor
disk comprising: providing a channel between said bolt and said
bolt hole; and causing a relatively hot fluid to pass through said
channel.
16. The method of claim 15 wherein said relatively hot fluid is
compressor discharge air.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to gas turbine engines and
more particularly to bolted joints for joining adjacent rotor disks
in such engines.
[0002] A gas turbine engine includes a compressor that provides
pressurized air to a combustor wherein the air is mixed with fuel
and the mixture is ignited for generating hot combustion gases.
These gases flow downstream to one or more turbines that extract
energy therefrom to drive the compressor and provide useful work
such as powering an aircraft in flight. The compressor and turbine
sections each include a plurality of rotor disks that are joined
together for rotation about the engine's centerline axis. Each
rotor disk comprises a central bore region, a disk rim from which a
plurality of radially extending blades are supported, and a web
joining the bore and rim. The bore and web are typically much more
massive than the, disk rim to accommodate the stresses to which the
disk is subjected.
[0003] Rotating disks, particularly those in the high pressure
turbine section of an engine, develop high radial thermal gradients
during transient operation because of exposure of the disk rim to
hot gases. In this case, the rim of the disk has a quick thermal
response (i.e., temperature increase) while the web and bore react
more slowly due to their high relative mass and their lower
temperature environment. The thermal gradient creates large
tangential and radial stresses in the web and bore of the disk that
are magnified by any stress concentrations such as holes, fillets
and the like.
[0004] A significant challenge in disk design is to connect
multiple disks together without developing high stresses. One
method of connection is through the use of bolted joints connecting
adjacent disks. Often, at least one of the disks must be bolted
through the disk web because of space limitations. In such
instances, the bolt holes are located in regions of high thermal
gradient and produce high concentrated stresses. This limits the
allowable time of operation of the rotor hardware.
[0005] One approach to reducing bolt hole stress is to balance the
radial and tangential stresses by modifying the hole pattern
design, i.e., the number of holes, hole spacing, hole diameter and
hole length. Generally, a bolted joint having more holes will
produce lower mechanical stresses in the tangential direction but
will result in higher radial stress. For every hole pattern design,
there exists a certain quantity of holes that will balance the
tangential stress at the top or bottom of the hole with the radial
stress at the sides of the hole. However, modifying the hole
pattern design to balance the radial and tangential stresses
typically results in increased disk weight and even slower
transient thermal response of the disk web and bore. Accordingly,
there is a need for an improved method of reducing bolt hole
stresses.
BRIEF SUMMARY OF THE INVENTION
[0006] The above-mentioned need is met by the present invention,
which provides a bolted joint for connecting first and second rotor
disks in a gas turbine engine. The bolted joint includes a bolt
hole formed in the first rotor disk and a bolt disposed in the bolt
hole such that a channel is defined between the bolt and the bolt
hole. A first abutment is attached to a first end of the bolt, and
a second abutment is attached to a second end of the bolt. A first
passage associated with the first abutment provides fluid
communication with the channel, and a second passage associated
with the second abutment provides fluid communication with the
channel. Hot fluid passing through the channel reduces thermal
gradients in the first rotor disk.
[0007] The present invention and its advantages over the prior art
will become apparent upon reading the following detailed
description and the appended claims with reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The subject matter that is regarded as the invention is
particularly pointed out and distinctly claimed in the concluding
part of the specification. The invention, however, may be best
understood by reference to the following description taken in
conjunction with the accompanying drawing figures in which:
[0009] FIG. 1 is a partial cross-sectional view of a gas turbine
engine having the bolted joint of the present invention.
[0010] FIG. 2 is an enlarged cross-sectional view of the bolted
joint of FIG. 1.
[0011] FIG. 3 is a perspective view of the bolt from the bolted
joint of FIG. 1.
[0012] FIG. 4 is an enlarged cross-sectional view of a second
embodiment of a bolted joint.
[0013] FIG. 5 is an enlarged cross-sectional view of a third
embodiment of a bolted joint.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Referring to the drawings wherein identical reference
numerals denote the same elements throughout the various views,
FIG. 1 shows a portion of a gas turbine engine 10 having, among
other structures, a combustor 12 and a turbine section 14 located
downstream of the combustor 12. The turbine section 14 includes a
first stage nozzle assembly 16, a first stage turbine rotor 18, a
second stage nozzle assembly 20 and a second stage turbine rotor 22
arrange sequentially along the engine centerline axis. The
combustor 12 includes a generally annular hollow body having an
outer liner 24 and an inner liner 26 defining a combustion chamber
28 therein. A compressor (not shown) provides compressed air that
passes primarily into the combustor 12 to support combustion and
partially around the combustor 12 where it is used to cool both the
combustor liners 24, 26 and turbomachinery further downstream. Fuel
is introduced into the forward end of the combustor 12 and is mixed
with the air in a conventional fashion. The resulting fuel-air
mixture flows into the combustion chamber 28 where it is ignited
for generating hot combustion gases. The hot combustion gases are
discharged to the turbine section 14 where they are expanded so
that energy is extracted.
[0015] The first stage nozzle assembly 16 includes an inner nozzle
support 30 to which a plurality of circumferentially adjoining
nozzle segments 32 is mounted. The nozzle segments 32 collectively
form a complete 360.degree. assembly. Each segment 32 has two or
more circumferentially spaced vanes 34 (one shown in FIG. 1) over
which the combustion gases flow. The vanes 34 are configured so as
to optimally direct the combustion gases to the first stage turbine
rotor 18. The inner nozzle support 30 is a stationary member
suitably supported in the engine 10.
[0016] The first stage turbine rotor 18 is located aft of the first
stage nozzle assembly 16 and is spaced axially therefrom so as to
define a first wheel cavity 36. The first stage turbine rotor 18
includes a plurality of turbine blades 38 (one shown in FIG. 1)
suitably mounted to a first rotor disk 40 and radially extending
into the turbine flow path. The second stage nozzle assembly 20 is
located aft of the first stage turbine rotor 18, and the second
stage turbine rotor 22 is located aft of the second stage nozzle
assembly 20 so as to define second and third wheel cavities 42 and
44, respectively. The second stage turbine rotor 22 includes a
plurality of turbine blades 46 (one shown in FIG. 1) suitably
mounted to a second rotor disk 48 and radially extending into the
turbine flow path. The second rotor disk 48 has a forward extending
flange 50 that is joined to the aft side of the first rotor disk 40
at a bolted joint 52. Thus, the first and second rotor disks 40, 48
are arranged to rotate together about the engine centerline
axis.
[0017] An annular rotating seal member 54 is fixed to the forward
side of the first rotor disk 40 for rotation therewith by the
bolted joint 52. The rotating seal member 54 contacts the inner
nozzle support 30 to form one or more forward seals 56 for sealing
the compressor discharge air that is bled off for cooling purposes
from the hot gases in the turbine flow path. In one preferred
embodiment, the forward seals 56 are rotating labyrinth seals, each
including a plurality of thin, tooth-like projections extending
radially outward from the stationary seal member 56. The outer
circumference of each projection rotates within a small tolerance
of the inner circumference of a corresponding annular stationary
seal member 58 mounted on the inner nozzle support 30, thereby
effecting sealing between the cooling air and the hot gases in the
turbine flow path.
[0018] The nozzle assembly 16 also includes an accelerator 60
disposed radially between the two forward seals 56. The accelerator
60 is an annular member that defines an internal air plenum. High
pressure compressor discharge air is fed to the accelerator 60 via
air holes 62 formed in the inner nozzle support 30. The high
pressure air passes axially through the accelerator 60 and is
discharged therefrom through a plurality of aft nozzles into a
chamber or cavity 63 located forward of the first rotor disk 40. A
portion of this air passes through passages 64 formed in the first
rotor disk 40 for cooling turbomachinery further downstream. As
will be described in more detail below, some of this high pressure
air is directed through the bolted joint 52 for reducing the
thermal gradient in the first rotor disk 40 and thereby reducing
disk transient stresses.
[0019] Referring now to FIGS. 2 and 3, the bolted joint 52 is
described in more detail. The bolted joint 52 comprises a bolt 66
extending axially through a first opening 68 in the rotating seal
member 54, a bolt hole 70 in the first rotor disk 40, and a second
opening 72 in the second rotor disk flange 50. Both ends of the
bolt 66 are threaded so that a first nut 74 is threadingly received
on the forward end of the bolt 66 and a second nut 76 is
threadingly received on the aft end of the bolt 66. The first nut
74 is a fixed abutment against the rotating seal member 54, and the
second nut 76 is a fixed abutment against the second rotor disk
flange 50. Thus, when the nuts 74, 76 are suitably tightened, the
first rotor disk 40, the second rotor disk 48 and the rotating seal
member 54 are joined together for rotation about the engine
centerline axis.
[0020] The bolt 66 includes first and second raised shoulders 78
and 80, respectively, that are located intermediate the threaded
ends thereof. The raised shoulders 78, 80 are sized to fit within
the bolt hole 70 and the second opening 72 with a tight tolerance
such that the bolted joint 52 provides a body-bound function. That
is, the bolted joint 52 will radially locate and maintain the
second rotor disk 48 with respect to the first rotor disk 40. The
second, or aft, raised shoulder 80 has an axial retention lip 82
formed on the outer circumference thereof. The axial retention lip
82 abuts a recess formed in the forward face of the second rotor
disk flange 50, thereby axially locating the bolt 66 with respect
to the first and second rotor disks 40, 48. This facilitates
assembly of the bolted joint 52, which is normally a blind
assembly.
[0021] The bolt 66 is sized so as to have an annular, axially
extending channel 84 formed thereabout. Specifically, except for
the raised shoulders 78, 80, the bolt 66 has a lesser diameter than
its surrounding structure; i.e., the bore of the first nut 74, the
first opening 68, the bolt hole 70, the second opening 72 and the
bore of the second nut 76. Accordingly, the channel 84 is defined
by the gap between the bolt 66 and its surrounding structure.
[0022] One or more radial inlet passages 86 are formed in the first
nut 74 for providing fluid communication between the forward cavity
63 and the channel 84. Similarly, one or more radial outlet
passages 88 are formed in the second nut 76 for providing fluid
communication between the second and third wheel cavities 42, 44
and the channel 84. As best seen in FIG. 3, each of the raised
shoulders 78, 80 has a plurality of axially extending flats 90
formed thereon. The flats 90 allow air to flow down the entire
length of the channel 84, while the rest of the raised shoulders
78, 80 engage the inner surfaces of the bolt hole 70 and the second
opening 72 to perform the body-bound function.
[0023] In operation, compressor discharge air delivered to the
forward cavity 63 from the accelerator 60 flows through the inlet
passages 86 in the first nut 74 into the forward end of the channel
84. This air passes through the bolt hole portion of the channel 84
due to the pressure differential between the forward cavity 63 and
the second and third wheel cavities 42, 44. The air is then
discharged through the outlet passages 88 to the second and third
wheel cavities 42, 44 where it rejoins the compressor discharge air
that has passed through the passages 64 and contributes to cooling
turbomachinery further downstream. As the compressor discharge air
(which is generally hotter than the web and core of the first rotor
disk 40) flows through the bolt hole portion of the channel 84, it
heats the first rotor disk 40 in the area around the bolt hole 70.
By heating the first rotor disk 40, the compressor discharge air
increases the thermal response of the disk's web and bore, thereby
decreasing the thermal gradient between the web and bore and the
disk's rim. This reduction in thermal gradient will cause a
reduction in unconcentrated thermal operating stresses and result
in increased hardware life. The amount of air delivered to the bolt
hole 70 is determined by the size of the inlet and outlet passages
86, 88 and/or the size of the shoulder flats 90. Thus, the amount
of air needed to produce the desired degree of disk heating for a
given system can be achieved by tightly controlling the sizes of
the inlet and outlet passages 86, 88 and the shoulder flats 90.
[0024] Turning to FIG. 4, a second embodiment of a bolted joint 152
is shown. The bolted joint 152 of the second embodiment comprises a
bolt 166 extending axially through a first opening 68 in the
rotating seal member 54, a bolt hole 70 in the first rotor disk 40,
and a second opening 72 in the second rotor disk flange 50. The
forward end of the bolt 166 has a head 174 integrally formed
thereon, and the aft end of the bolt 166 is threaded so that a nut
176 is threadingly received thereon. A first washer or spacer 92 is
disposed on the bolt 166 between the head 174 and the rotating seal
member 54, and a second washer or spacer 94 is disposed on the bolt
166 between the nut 176 and the second rotor disk flange 50. The
head 174 and first spacer 92 act as a fixed abutment against the
rotating seal member 54, and the nut 176 and second spacer 94 act
as a fixed abutment against the second rotor disk flange 50. Thus,
when the nut 176 is suitably tightened, the first rotor disk 40,
the second rotor disk 48 and the rotating seal member 54 are joined
together for rotation about the engine centerline axis.
Alternatively, two threaded nuts could be used (like in the first
embodiment) instead of the integral head and single nut.
[0025] The bolt 166 includes first and second raised shoulders 178
and 180, respectively. As in the first embodiment, the raised
shoulders 178, 180 are sized to fit within the bolt hole 70 and the
second opening 72 with a tight tolerance such that the bolted joint
152 provides a body-bound function and have axially extending flats
formed thereon. Also like the first embodiment, the bolt 166 is
sized so as to have an annular, axially extending channel 184
formed thereabout. Specifically, except for the raised shoulders
178, 180, the bolt 166 has a lesser diameter than its surrounding
structure; i.e., the first spacer 92, the first opening 68, the
bolt hole 70, the second opening 72 and the second spacer 94.
Accordingly, the channel 184 is defined by the gap between the bolt
166 and its surrounding structure.
[0026] One or more radial inlet passages 186 are formed in the
first spacer 92 for providing fluid communication between the
forward cavity 63 and the channel 184. Similarly, one or more
radial outlet passages 188 are formed in the second spacer 94 for
providing fluid communication between the second and third wheel
cavities 42, 44 and the channel 184. Thus, compressor discharge air
will flow into the channel 184 through the inlet passages 186 and
out of the channel 184 through the outlet passages 188. The
compressor discharge air will heat the first rotor disk 40 in the
area around the bolt hole 70 as it flows through the bolt hole
portion of the channel 184.
[0027] Turning to FIG. 5, a third embodiment of a bolted joint 252
is shown. The bolted joint 252 of the third embodiment comprises a
bolt 266 extending axially through a first opening 68 in the
rotating seal member 54, a bolt hole 70 in the first rotor disk 40,
and a second opening 72 in the second rotor disk flange 50.
[0028] Both ends of the bolt 266 are threaded so that a first nut
274 is threadingly received on the forward end of the bolt 266 and
a second nut 276 is threadingly received on the aft end of the bolt
266 for joining the first rotor disk 40, the second rotor disk 48
and the rotating seal member 54. As with the prior embodiments, the
bolt 266 is sized so as to have an annular, axially extending
channel 284 formed thereabout. However, in this embodiment, inlet
and outlet passages for the channel 284 are not formed in nuts or
spacers. Instead, one or more grooves or slots 286 are formed in
the forward surface of the rotating seal member 54, adjacent to the
first nut 274. Thus, the first nut 274 and the slots 286 define
inlet passages that provide fluid communication between the forward
cavity 63 and the channel 284. Similarly, one or more grooves or
slots 288 are formed in the aft surface of the second rotor disk
flange 50, adjacent to the second nut 276. Thus, the second nut 276
and the slots 288 define outlet passages that provide fluid
communication between the second and third wheel cavities 42, 44
and the channel 284. Compressor discharge air will thus flow into
the channel 284 through the inlet slots 286 and out of the channel
284 through the outlet slots 288. The compressor discharge air will
heat the first rotor disk 40 in the area around the bolt hole 70 as
it flows through the bolt hole portion of the channel 284. This
embodiment can be implemented with or without spacers and with a
bolt having an integral head and a single nut as an alternative to
the two threaded nuts 274, 276, as shown. While this third
embodiment will simplify the manufacture of the fasteners and
possibly reduce overall part count, it could also result in
increased stress concentrations in the structural rotor
components.
[0029] The foregoing has described a bolted joint that increases
the thermal response of the disk web and bore through use of a
parallel air delivery system. The increased thermal response
reduces the thermal gradient in the rotor disk, which in turn
reduces disk transient stresses. While specific embodiments of the
present invention have been described, it will be apparent to those
skilled in the art that various modifications thereto can be made
without departing from the spirit and scope of the invention as
defined in the appended claims.
* * * * *