U.S. patent application number 13/538507 was filed with the patent office on 2014-01-09 for sleeve for turbine bearing stack.
This patent application is currently assigned to United Technologies Corporation. The applicant listed for this patent is Marc J. Muldoon. Invention is credited to Marc J. Muldoon.
Application Number | 20140010648 13/538507 |
Document ID | / |
Family ID | 49783790 |
Filed Date | 2014-01-09 |
United States Patent
Application |
20140010648 |
Kind Code |
A1 |
Muldoon; Marc J. |
January 9, 2014 |
SLEEVE FOR TURBINE BEARING STACK
Abstract
A support bearing arrangement comprises a gas turbine rotor
shaft, a bearing stack, a bearing sleeve, and a support bearing.
The bearing stack comprises a fore seal plate, and aft seal plate,
and a bearing mount situated axially between the fore and aft seal
plates. The bearing sleeve surrounds at least a portion of the
rotor shaft, and is configured to form an insulating air gap
between the rotor shaft and the bearing stack. The support bearing
is mounted on the bearing mount to couple the gas turbine rotor
shaft to a stationary structure, thereby centering and retaining
the gas turbine rotor shaft.
Inventors: |
Muldoon; Marc J.;
(Marlborough, CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Muldoon; Marc J. |
Marlborough |
CT |
US |
|
|
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
49783790 |
Appl. No.: |
13/538507 |
Filed: |
June 29, 2012 |
Current U.S.
Class: |
415/230 |
Current CPC
Class: |
F01D 25/16 20130101 |
Class at
Publication: |
415/230 |
International
Class: |
F01D 25/16 20060101
F01D025/16 |
Claims
1. A support bearing arrangement comprising: a gas turbine rotor
shaft; a bearing stack comprised of a fore seal plate, an aft seal
plate, and a bearing mount situated axially between the fore and
aft seal plates; a bearing sleeve surrounding at least a portion of
the rotor shaft, and configured to form an insulating air gap
between the rotor shaft and the bearing stack; and a support
bearing mounted on the bearing mount to couple the gas turbine
rotor shaft to a stationary structure, thereby centering and
retaining the gas turbine rotor shaft.
2. The support bearing arrangement of claim 1, further comprising a
rotor disk affixed to the rotor shaft, wherein the bearing sleeve
and an axially-extending cylindrical portion of the rotor disk
surrounding the rotor shaft define the insulating air gap.
3. The support bearing arrangement of claim 2, further comprising a
blade retention minidisk disposed axially between the rotor disk
and the bearing sleeve, and an axial load nut configured to attach
to the gas turbine rotor shaft and bear axial load from the
minidisk through the bearing sleeve.
4. The support bearing arrangement of claim 1, wherein the fore
seal plate and the aft seal plate mate with adjacent fore and aft
seals, respectively, to form oil seals.
5. The support bearing arrangement of claim 4, wherein the bearing
mount is lubricated with oil collected by an oil scoop situated
axially between the fore and aft seal plates.
6. The support bearing arrangement of claim 1, wherein the bearing
sleeve is formed of a material selected to closely match the
thermal expansion coefficients of surrounding components.
7. The support bearing arrangement of claim 6, wherein the bearing
sleeve is formed of Waspalloy.
8. The support bearing arrangement of claim 1, wherein the
stationary structure is a mid-turbine frame situated between a high
pressure turbine and a low pressure turbine of a two-stage gas
turbine engine.
9. A gas turbine shaft assembly comprising: a gas turbine rotor
disk mounted on a rotatable shaft, the gas turbine rotor disk
having an axially aft-extending cylindrical portion; a bearing
sleeve sheathing the aft-extending cylindrical portion of the rotor
disk so as to define an insulating radial air gap between the
bearing sleeve and the aft-extending cylindrical portion of the
rotor disk; and a bearing stack comprising a bearing mount axially
between fore and aft face seals situated radially atop the bearing
sleeve, and thermally shielded from the gas turbine rotor disk and
the rotatable shaft by the insulating radial air gap.
10. The gas turbine shaft assembly of claim 9, further comprising a
minidisk mounted on the aft-extending cylindrical portion of the
rotor disk to retain blades of the gas turbine rotor disk.
11. The gas turbine shaft assembly of claim 10, further comprising
a first nut configured to axially retain the gas turbine rotor disk
on the rotatable shaft, and a second nut configured to axially
retain the minidisk against the gas turbine rotor disk by means of
axial load transferred through the bearing stack and the bearing
sleeve.
12. The gas turbine shaft assembly of claim 9, wherein the gas
turbine rotor shaft is a high pressure shaft of a two-stage gas
turbine engine.
13. The gas turbine shaft assembly of claim 9, wherein the bearing
mount accepts a support bearing configured to transfer radial load
from the gas turbine rotor shaft to a stationary structure, thereby
retaining and centering the gas turbine rotor shaft.
14. The gas turbine shaft assembly of claim 15, wherein the support
bearing is a roller bearing.
15. The gas turbine shaft assembly of claim 15, wherein the
stationary structure is a mid-turbine frame comprising a plurality
of stationary vanes disposed between a high pressure turbine and a
low pressure turbine of a two-stage gas turbine engine.
16. The gas turbine shaft assembly of claim 9, wherein the bearing
mount is lubricated with oil collected by an oil scoop also mounted
axially between the fore and aft seal plates.
Description
BACKGROUND
[0001] The present invention relates generally to turbomachinery,
and specifically to bearing protection structures. In particular,
the invention concerns a thermal protection sleeve for gas turbine
radial support bearings.
[0002] Gas turbine engines are rotary-type combustion engines
comprising a compressor, a combustor, and a turbine. Gas drawn in
at an upstream inlet is compressed by the compressor via a
plurality of alternating airfoil stages of non-rotating compressor
vanes and rotating compressor blades. This compressed gas is fed
into the combustor and mixed with fuel. The resulting fuel-air
mixture is then ignited to generate hot combustion gas. The turbine
extracts energy from the expanding combustion gas via a series of
alternating airfoil stages of non-rotating turbine vanes and
rotating turbine blades in the form of rotation of at least one
axial shaft. Gas is expelled from the turbine at an outlet which
may provide reactive thrust from exhaust. Energy extracted by the
turbine drives the compressor, and may also power gearboxes,
generators, and other external devices.
[0003] Gas turbine engines provide efficient, reliable power for a
wide range of applications, including aviation and industrial power
generation. Many larger gas turbine engines include multiple stages
of compressors and turbines arranged in series. A conventional
two-stage gas turbine engine comprises, in flow-path order from
inlet to outlet: a fan, a low pressure compressor (LPC), a high
pressure compressor (HPC), a combustor, a high pressure turbine
(HPT), and a low pressure turbine (LPT). The fan, LPT, and LPC are
connected by a common low pressure shaft that turns at a first
speed, while the HPC and HPT share a common high pressure shaft
that turns at a second, higher speed. These high pressure and low
pressure shafts are arranged in coaxially nested spools. Some two
stage gas turbine engines include a mid-turbine frame (MTF), an
intermediate non-rotating vane structure situated between the high
pressure turbine and the low pressure turbine.
[0004] High pressure and low pressure shafts of gas turbine engines
are centered and radially supported against stationary casing
structures by means of radial support bearings. These bearings
allow stationary structures such as vane stages, combustors, and
MTFs to radially and axially position and retain the shafts. In
some gas turbine engines, radial support bearings may be situated
on or near a hot shaft. Excessive heat can damage bearings, and
cause coking or congestion of lubricant oil.
SUMMARY
[0005] The present invention is directed toward a support bearing
arrangement having a gas turbine rotor shaft, a bearing stack, a
bearing sleeve, and a support bearing. The bearing stack comprises
a fore seal plate, and aft seal plate, and a bearing mount situated
axially between the fore and aft seal plates. The bearing sleeve
surrounds at least a portion of the rotor shaft, and is configured
to form an insulating air gap between the rotor shaft and the
bearing stack. The support bearing is mounted on the bearing mount
to couple the gas turbine rotor shaft to a stationary structure,
thereby centering and retaining the gas turbine rotor shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic diagram of a gas turbine engine.
[0007] FIG. 2 is a cross-sectional view of a bearing region of the
gas turbine engine of FIG. 1.
DETAILED DESCRIPTION
[0008] FIG. 1 depicts gas turbine engine 10, comprising fan 12,
compressor 14, combustor 16, and turbine 18, and casing 20.
Compressor 14 comprises low pressure compressor (LPC) 22 and high
pressure compressor (HPC) 24, and turbine 18 comprises high
pressure turbine (HPT) 26, mid-turbine frame (MTF) 28, and low
pressure turbine (LPT) 30. LPC 22, HPC 24, HPT 26, and LPT 30 each
comprise a plurality of alternating airfoils stages of non-rotating
vanes and rotating blades. HPT 26, in particular, comprises at
least one HPT rotor disk 32 adjacent MTF 28, and at least one HPT
stator 34 adjacent HPT rotor disk 32. Although FIG. 1 depicts a two
spool engine having a high pressure spool and a low pressure spool,
the present invention may additionally or alternatively be applied
to engines having only one spool, or three or more spools. In
particular, the bearing sleeve that is the subject of the present
invention can be applied embodiments of gas turbine engine 10
having a third, intermediate pressure (IP) spool in addition to low
and high pressure (LP, HP) spools.
[0009] Fan 12, LPC 22, and LPT 30 share a common low pressure shaft
36, while HPC 24 and HPT 26 share a common high pressure shaft 38.
Low pressure shaft 34 and high pressure shaft 36 are rotor shafts
centered and supported by support bearings 40, which carry axial
and radial load from both shafts to casing 20 via non-rotating
structures including MTF 28. MTF 28 is a non-rotating structure
including a plurality of stationary vanes disposed between HPT 26
and LPT 30.
[0010] Gas turbine engine 10 is a two-stage gas turbine engine
wherein fan 12 receives and propels airflow F axially aft. A
portion of airflow F enters and is pressurized by LPC 22 and HPC
24, each of which comprises a plurality of alternating stages of
rotor and stator airfoils. Pressurized gas from HPC 24 is fed into
combustor 16, where it is mixed with combustible fuel. The
resulting fuel-air mixture is ignited to produce a hot working
fluid that drives HPT 26 and LPT 30 before exiting gas turbine
engine 10. HPT 26 and LPT 30 comprise a plurality of alternating
stages of rotor and stator airfoils. The working fluid rotates
turbine rotors such as HPT rotor disk 32, thereby driving high
pressure shaft 38 and low pressure shaft 36. High pressure shaft 38
in turn drives HPC 24, while low pressure shaft 36 drives LPC 22
and fan 12. In some embodiments, high pressure shaft 38 and/or low
pressure shaft 36 may additionally drive a generator (not shown) or
other powered system, either directly or via a gearbox.
[0011] Low pressure shaft 36 and high pressure shaft 38 are
substantially rigid coaxial cylinders. Fan 12, LPC 22, and LPT 30
are mounted on low pressure shaft 36, while HPC 24 and HPT 26 are
mounted on high pressure shaft 38. High pressure shaft 38 and low
pressure shaft 26 are both centered and supported by casing 20.
Casing 20 is a rigid external structure of gas turbine 10 that
retains and positions components of gas turbine engine 10 including
LPC 22, HPC 24, HPT 26, MTF 28, and LPT 30. Low pressure shaft 36
and high pressure shaft 38 ride bearings 40, which form interfaces
between the shafts and non-rotating structures of compressor 14 and
turbine 18, including MTF 28. These non-rotating structures carry
axial and radial loads from high pressure shaft 38 and low pressure
shaft 36 to casing 20, which provides a substantially rigid
foundation to align and retain both shafts. Support bearings 40
may, for instance, be roller bearings arranged in rings about low
pressure shaft 36 and high pressure shaft 38. In some instances,
bearings 40 may be lubricated with oil. Support bearings 40 may be
located between low pressure shaft 36 and stationary portions of
LPC 22 and LPT 30, and between high pressure shaft 38 and MTF
28.
[0012] During operation of gas turbine engine 10, HPT rotor disk 32
and high pressure shaft 38 can reach high temperatures capable of
damaging or degrading support bearings 40, and causing coking and
congestion of lubricant oil. Accordingly, at least some support
bearings 40 located near high pressure shaft 38 are provided with a
protective sleeve that forms a thermal barrier between support
bearings and high pressure shaft 38 and HPT rotor disk 32 (see
sleeve 116 of FIG. 2, described in further detail below).
[0013] FIG. 2. is a cross-sectional view of a region 2 of gas
turbine engine 10 (see FIG. 1). FIG. 2 depicts MTF 28, HPT rotor
disk 32, high pressure shaft 38, support bearings 40, tubular HPT
portion 42, bearing mount 102, oil scoop 104, oil source 106, fore
seal plate 108, aft seal plate 110, fore seal 112, aft seal 114,
bearing sleeve 116, minidisk 118, NPT nut 120, bearing nut 122, and
radial air gap 124.
[0014] Support bearing 40 is one of an annular ring of bearings
that provide an interface between MTF 28 and high pressure shaft 38
to retain, center, and support high pressure shaft 38. Support
bearing 40 may, for instance, be a lubricated roller bearing. MTF
28 is an intermediate vane structure located between HPT 26 and LPT
30, and rigidly attached to casing 20 (see FIG. 1). MTF 28 carries
radial load between support bearing 40 and casing 20 to anchor high
pressure shaft 38. Bearing mount 102 is a rotating structure
configured to receive support bearings 40 and distribute
lubricating oil from oil scoop 104 to support bearings 40. Oil
scoop is a rotating structure configured to draw oil radially
inward from oil source 106 to adjacent a radially outer surface of
bearing sleeve 116. Oil scoop 104 has lubricant channels configured
to allow oil to centripetally flow axially aft and radially outward
to bearing mount 102 to lubricate support bearings 40. Oil scoop
104 receives lubricant oil from oil source 106, a non-rotating tube
or nozzle that drips or sprays oil onto oil scoop 104 at metered
rate. Scallops or angled channels in oil scoop 104 draw oil
radially inward from oil source 106 as oil scoop 104 rotates. Oil
source 106 may, for instance, receive oil from tubing extending
through MTF 28 to casing 20.
[0015] Fore and aft seal plates 108 and 110 are rotating structures
that form a face seal with fore and aft seals 112 and 114. Fore and
aft seals 112 and 114 are non-rotating components such as static
carbon seals. Fore and aft seals 112 and 114 mate with fore and aft
seal plates 108 and 110 to create an oil seal that prevents leakage
of oil from oil source 106 into surrounding regions of gas turbine
engine 10. Fore and aft seals 112 and 114 may be mounted to MTF 28
or to other local non-rotating structures. In some embodiments,
seal plates 108 and 110 may receive lubricating oil from bearing
mount 102 and/or oil scoop 104.
[0016] Bearing sleeve 116 is a rigid cylindrical heat shield formed
of a material such as Waspaloy. Materials for bearing sleeve 116
may further be selected to closely match the thermal expansion
coefficients of surrounding materials (e.g. MTF 28 and HPT rotor
disk 32). Bearing sleeve 116 surrounds tubular HPT portion 42, an
axially aft-extending cylindrical section of HPT rotor disk 32.
Bearing sleeve 116 and tubular HPT portion 42 are constructed to
form radial air gap 124, an open space between bearing sleeve 116
and tubular HPT portion 42 that at least partially thermally
isolates the bearing stack comprising fore seal plate 108, bearing
mount 102, oil scoop 104, and aft seal plate 110 from high pressure
shaft 38. Bearing sleeve 116 is constructed to contact tubular HPT
portion 42 at locations situated remotely from bearing mount 102,
so as to limit thermal impact on bearing fits and bore temperature.
As described above with respect to FIG. 1, high pressure shaft 38
may reach sufficiently high temperatures during operation of gas
turbine engine 10 to cause damage to support bearing 40 and/or fore
and aft seal plates 108 and 110. High temperatures can also cause
coking and congestion of lubricant oil within channels of bearing
mount 102 and oil scoop 104, impeding lubrication of support
bearing 40. Bearing sleeve 116 carries axial load from bearing nut
122 to minidisk 118 while protecting the bearing stack from
excessive heating by separating bearing stack components from HPT
rotor disk 32 and high pressure shaft 38 by radial air gap 124,
which acts as an insulator.
[0017] Minidisk 118 is a substantially disk-shaped cover plate that
abuts HPT rotor disk 32. Minidisk 118 provides axial retention for
blades of HPT rotor disk 32, and in some embodiments may direct
conditioning air along the aft face of HPT rotor disk 32. Minidisk
118 is axially retained against HPT rotor disk 32 by bearing sleeve
116, which fits radially over and axially abuts minidisk 118. HPT
nut 120 and bearing nut 122 are threaded load-bearing nuts that
screw onto a threaded tie shaft region of high pressure shaft 38.
HPT nut 120 retains HPT rotor disk 32, while bearing nut 122
retains the bearing stack (comprising bearing mount 102, oil scoop
104, and fore and aft seal plates 108 and 110) against bearing
sleeve 116, thereby securing minidisk 118 against HPT rotor disk
32. In some embodiments, minidisk 118 may meet HPT rotor disk 32 in
a bayonet or anti-rotation crenellation at the inner diameter of
minidisk 118. In these embodiments, bearing sleeve 116 may secure
minidisk 118 against the bayonet or anti-rotation crenellation,
thereby preventing minidisk 118 from moving relative to HPT rotor
disk 32.
[0018] Although the preceding description has focused on
embodiments wherein support bearing 40 and bearing sleeve 116 are
situated at an aft end of high pressure shaft 38 near MTF 28, the
present invention may also be applied to shield support bearings
and carry axial loads at other locations on high pressure shaft 38
or low pressure shaft 36. Support bearings 40 located close to high
pressure shaft 36 are particularly likely to be exposed to high
temperatures that can result in oil coking, and are therefore in
particular need of the thermal protection provided by bearing
sleeve 116. Some configurations of gas turbine engine 10 may also
expose support bearings 40 to oil coking temperatures at locations
radially or axially further from high pressure shaft 38, however,
necessitating similar protection.
[0019] While the invention has been described with reference to an
exemplary embodiment(s), it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
[0020] In one embodiment of the present invention, a support
bearing arrangement includes a gas turbine rotor shaft, a bearing
stack, a bearing sleeve, and a support bearing. The bearing stack
comprises a fore seal plate, and aft seal plate, and a bearing
mount situated axially between the fore and aft seal plates. The
bearing sleeve surrounds at least a portion of the rotor shaft, and
is configured to form an insulating air gap between the rotor shaft
and the bearing stack. The support bearing is mounted on the
bearing mount to couple the gas turbine rotor shaft to a stationary
structure, thereby centering and retaining the gas turbine rotor
shaft.
[0021] Additional and/or alternative embodiments include a rotor
disk affixed to the rotor shaft, such that the bearing sleeve and
an axially-extending cylindrical portion of the rotor disk
surrounding the rotor shaft define the insulating air gap. Some
such embodiments include a blade retention minidisk disposed
between the rotor disk and the bearing sleeve, and an axial nut
configured to attach to the gas turbine rotor shaft and bear axial
load from the minidisk through the bearing sleeve. Further
embodiments include fore and aft seal plates that mate to form air
seals with adjacent respective fore and aft seals; an oil scoop
situated between the fore and aft seal plates that provides oil to
lubricate the bearing mount; and forming the bearing sleeve of a
material such as Waspalloy selected to closely match the thermal
expansion coefficients of surrounding components.
[0022] In another embodiment of the invention, a gas turbine engine
comprises a gas turbine rotor disk mounted on a rotatable shaft, a
bearing sleeve, and a bearing stack. The gas turbine rotor disk has
an axially aft-extending cylindrical portion. The bearing sleeve
sheaths the aft extending cylindrical portion of the rotor disk so
as to define an insulating radial air gap between the bearing
sleeve and the aft-extending cylindrical portion of the rotor disk.
The bearing stack comprises a bearing mount axially between fore
and aft face seals situated radially atop the bearing sleeve, and
thermally shielded from the gas turbine rotor disk and the
rotatable shaft by the insulating radial air gap.
[0023] Additional and/or alternative embodiments include a minidisk
mounted on the aft-extending cylindrical portion of the rotor disk
to retain blades of the gas turbine rotor disk; a first nut
configured to axially retain the gas turbine rotor disk on the
rotatable shaft; and/or a second nut configured to axially retain
the minidisk against the gas turbine rotor disk by means of axial
load transferred through the bearing stack and the bearing sleeve.
In some embodiments, the gas turbine rotor shaft may be a high
pressure shaft of a two-stage gas turbine engine; the bearing mount
may accept a support bearing configured to transfer radial load
from the gas turbine rotor shaft to a stationary structure, thereby
retaining and centering the gas turbine rotor shaft; the support
bearing may be a roller bearing; the stationary structure may be a
mid-turbine frame comprising a plurality of stationary vanes
disposed between a high pressure turbine and a low pressure turbine
of a two-stage gas turbine engine; and/or the bearing mount may be
lubricated with oil collected by an oil scoop also mounted axially
between the fore and aft seal plates
* * * * *