U.S. patent application number 13/096645 was filed with the patent office on 2012-11-01 for turbine engine and load reduction device thereof.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to David Paul Adam, Weize Kang, Tod Robert Steen.
Application Number | 20120275921 13/096645 |
Document ID | / |
Family ID | 46084812 |
Filed Date | 2012-11-01 |
United States Patent
Application |
20120275921 |
Kind Code |
A1 |
Steen; Tod Robert ; et
al. |
November 1, 2012 |
TURBINE ENGINE AND LOAD REDUCTION DEVICE THEREOF
Abstract
A fan rotor apparatus includes: a rotatable fan disk defining a
central aperture and carrying an array of airfoil-shaped fan blades
around its periphery, the disk having a forward end and an aft end;
and an annular, generally axially-extending forward fan shaft
extending through the aperture and coupled to the fan disk for
rotation therewith, where the forward fan shaft joins the fan disk
at or near the forward end.
Inventors: |
Steen; Tod Robert;
(Cincinnati, OH) ; Kang; Weize; (Cincinnati,
OH) ; Adam; David Paul; (Cincinnati, OH) |
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
46084812 |
Appl. No.: |
13/096645 |
Filed: |
April 28, 2011 |
Current U.S.
Class: |
416/204R |
Current CPC
Class: |
F01D 5/025 20130101;
F01D 21/04 20130101; F01D 21/045 20130101; F01D 25/162
20130101 |
Class at
Publication: |
416/204.R |
International
Class: |
F01D 5/00 20060101
F01D005/00 |
Claims
1. A fan rotor apparatus comprising: a rotatable fan disk defining
a central aperture and carrying an array of airfoil-shaped fan
blades around its periphery, the disk having a forward end and an
aft end; and an annular, generally axially-extending forward fan
shaft extending through the aperture and coupled to the fan disk
for rotation therewith, where the forward fan shaft joins the fan
disk at or near the forward end of the fan disk.
2. The apparatus of claim 1 wherein a forward end of the forward
fan shaft is disposed axially forward of the forward end of the fan
disk.
3. The apparatus of claim 1 wherein the fan disk comprises a disk
arm extending from the forward end which is coupled to the forward
fan shaft.
4. The apparatus of claim 3 wherein the disk arm comprises: a
forward portion having a C-shaped cross-section, and an aft portion
extending axially between the forward portion and the forward fan
shaft.
5. The apparatus of claim 4 wherein a least a part of the forward
portion of the disk arm is disposed axially forward of the forward
end of the fan disk.
6. The apparatus of claim 1 wherein the forward fan shaft is
integrally-formed with the fan disk.
7. The apparatus of claim 1 wherein: the forward fan shaft is
coupled to a rear fan shaft, the two shafts collectively forming an
inner shaft; and the inner shaft is mounted for rotation in a
plurality of rolling-element bearings axially spaced apart along
the inner shaft.
8. The apparatus of claim 7 wherein at least one of the bearings is
mounted a structural support frame by a fuse which is configured to
fail at a predetermined radial load.
9. A turbofan engine, comprising: a turbomachinery core operable to
produce a flow of pressurized combustion gases; a turbine disposed
aft of the core; a rotatable fan disk mounted forward of the core,
the fan disk defining a central aperture and carrying an array of
airfoil-shaped fan blades around its periphery, the disk having a
forward end and an aft end; an annular, generally axially-extending
forward fan shaft mechanically coupled to the turbine, the forward
fan shaft extending through the aperture and coupled to the fan
disk for rotation therewith, where the forward fan shaft joins the
fan disk at or near the forward end of the fan disk.
10. The engine of claim 9 wherein a forward end of the forward
shaft is disposed axially forward of the forward end of the fan
disk.
11. The engine of claim 9 wherein the fan disk comprises a disk arm
extending from the forward end which is coupled to the forward fan
shaft:
12. The engine of claim 11 wherein the disk arm comprises: a
forward portion having a C-shaped cross-section, and an aft portion
extending axially between the forward portion and the forward fan
shaft.
13. The engine of claim 12 wherein a least a part of the forward
portion of the disk arm is disposed axially forward of the forward
end of the fan disk.
14. The engine of claim 9 wherein the forward fan shaft is
integrally-formed with the fan disk.
15. The engine of claim 9 wherein: the forward fan shaft is coupled
to a rear fan shaft, the two shafts collectively forming an inner
shaft which extends between the turbine and the fan disk; and the
inner shaft is mounted for rotation in a plurality of
rolling-element bearings axially spaced apart along the inner
shaft.
16. The engine of claim 15 wherein at least one of the bearings is
mounted a structural support frame by a fuse which is configured to
fail at a predetermined radial load.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to gas turbine engines and
more specifically to bearing assemblies and load reduction devices
for gas turbine engines.
[0002] A gas turbine engine includes a turbomachinery core having a
high pressure compressor, combustor, and high pressure turbine in
serial flow relationship. The core is operable in a known manner to
generate a primary flow of propulsive gas. A typical turbofan
engine adds a low pressure turbine driven by the core exhaust gases
which in turn drives a fan rotor through a shaft to generate a
bypass flow of propulsive gas. In the case of a high bypass engine
this provides the majority of the total engine thrust.
[0003] The fan rotor includes a fan that includes an array of fan
blades extending radially outward from fan disk. The fan shaft
transfers power and rotary motion from the low pressure turbine to
the fan disk and is supported in several rolling-element bearing
assemblies spaced along its length. The bearings are commonly
referred to as no. 1, no. 2, and no. 5 bearings, identifying their
sequential position in the engine.
[0004] During operation of the engine, a fragment of a fan blade
may become separated from the remainder of the blade as a result of
impact with a foreign object. Accordingly, a substantial rotary
unbalance load may be created within the damaged fan and carried by
the bearings, bearing supports, and the fan support frames.
[0005] To minimize the effects of potentially damaging abnormal
imbalance loads, known engines include support components for the
fan rotor support system that are sized to provide additional
strength for the fan support system. However, increasing the
strength of the support components undesirably increases an overall
weight of the engine and decreases an overall efficiency of the
engine when the engine is operated without substantial rotor
imbalances.
[0006] Other known engines include a bearing support that includes
a mechanically weakened section, or primary fuse, that decouples
the fan rotor from the fan support system. During such events, the
fan shaft seeks a new center of rotation that approximates that of
its unbalanced center of gravity. This fuse section, in combination
with a rotor clearance allowance, is referred to as a load
reduction device, or "LRD". The LRD reduces the rotating dynamic
loads to the fan support system.
[0007] For the LRD to operate successfully, it is often desirable
to have a specific ratio of the axial distance from the fan disk to
the #5 bearing, divided by the axial distance from the #2 bearing
to the #5 bearing. However, newer engine designs with long cores
and short forward overhangs do not provide sufficient axial length
for this configuration.
[0008] Accordingly, there is a need for a fan rotor load reduction
device which is effective in a limited axial space.
BRIEF DESCRIPTION OF THE INVENTION
[0009] These and other shortcomings of the prior art are addressed
by the present invention, which provides a forward fan shaft with
increased flexibility in a given space.
[0010] According to one aspect, the invention provides a fan rotor
apparatus including: a rotatable fan disk defining a central
aperture and carrying an array of airfoil-shaped fan blades around
its periphery, the disk having a forward end and an aft end; an
annular, generally axially-extending forward fan shaft extending
through the aperture and coupled to the fan disk for rotation
therewith, where the forward fan shaft joins the fan disk at or
near the forward end.
[0011] According to another aspect of the invention, a turbofan
engine includes: a turbomachinery core operable to produce a flow
of pressurized combustion gases; a turbine disposed aft of the
core; a rotatable fan disk mounted forward of the core, the fan
disk defining a central aperture and carrying an array of
airfoil-shaped fan blades around its periphery, the disk having a
forward end and an aft end; and an annular, generally
axially-extending forward fan shaft mechanically coupled to the
turbine, the forward fan shaft extending through the aperture and
coupled to the fan disk for rotation therewith, where the forward
fan shaft joins the fan disk at or near the forward end.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention may be best understood by reference to the
following description taken in conjunction with the accompanying
drawing figures in which:
[0013] FIG. 1 is a schematic cross-sectional view of a prior art
gas turbine engine;
[0014] FIG. 2 is an enlarged view of a portion of a gas turbine
engine incorporating a load reduction device constructed according
to an aspect of the present invention of ; and
[0015] FIG. 3 is a cross-sectional view of a portion of a gas
turbine engine showing an alternative load reduction device.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Referring to the drawings wherein identical reference
numerals denote the same elements throughout the various views,
FIG. 1 schematically depicts a prior art gas turbine engine 10. The
engine 10 has a longitudinal axis 11 and includes a fan 12, a low
pressure compressor or "booster" 14 and a low pressure turbine
("LPT") 16 collectively referred to as a "low pressure system". The
LPT 16 drives the fan 12 and booster 14 through an inner shaft 18,
also referred to as an "LP shaft". The engine 10 also includes a
high pressure compressor ("HPC") 20, a combustor 22, and a high
pressure turbine ("HPT") 24, collectively referred to as a "gas
generator" or "core". Together, the high and low pressure systems
are operable in a known manner to generate a primary or core flow
as well as a fan flow or bypass flow. While the illustrated engine
10 is a high-bypass turbofan engine, the principles described
herein are equally applicable to other types of turbine
engines.
[0017] The inner shaft 18 comprises a forward fan shaft 28 and a
rear fan shaft 30 coupled together and mounted for rotation in
several rolling-element bearings. The forward fan shaft 28 is
carried by a first bearing 32 (commonly referred to as a "no. 1
bearing") and a second bearing 34 (commonly referred to as a "no. 2
bearing"). The rear fan shaft 30 is carried by a bearing 36
(commonly referred to as a "#5 bearing").
[0018] The fan 12 of the engine 10 shown in FIG. 1 is coupled to
the forward fan shaft 28 in accordance with prior art principles.
In contrast, FIG. 2 illustrates a fan 112 and surrounding structure
which are constructed according to an aspect of the present
invention, and which may be incorporated in the engine 10. The fan
112 comprises a fan disk 138 with a central aperture 139. The fan
disk 138 has an annular array of airfoil-shaped fan blades 140
mounted around its periphery. The fan disk 138 has a forward end
142 and an aft end 144. An annular disk arm 150 extends at an angle
axially forward and radially inward from the forward end 142 of the
disk 138. A forward fan shaft 128 extends between the fan disk 138
and a rear fan shaft 130, and is coupled to the rear fan shaft 130
for rotation therewith, for example by a bolted joint or a splined
connection. The forward fan shaft 128 comprises part of a load
reduction device.
[0019] A no. 1 bearing 132 is mounted to a surrounding structural
support frame 146 by an annular, generally axially-extending fuse
148. In accordance with known principles, the size, material, and
mechanical design of the fuse 148 is selected to fail at a
predetermined radial load, such as a load that might occur after
separation of a fan blade 140. Failure of the fuse 148 allows the
fan disk 138 to rotate about a new axis of rotation without
imposing excessive radial loads on the surrounding structure. Other
types of fuse structures are known, such as bolted joints or fuse
pins designed to fail in tension or in shear, or collapsible
member(s) in a frame designed to crush at designated loads. The
specific type of fuse structure is not critical to the present
invention.
[0020] In contrast with prior art designs, the forward fan shaft
128 extends axially forward past the aft end 144 of the fan disk
138, traversing the longitudinal extent of the fan disk 138, and is
coupled to the fan disk 138 at a point at or near the forward end
142 of the fan disk 138. As used herein, the term "coupled to the
fan disk at or near the forward end" means that torque is
transferred from the forward fan shaft 128 to the fan disk 138
through a load path passing at or through the disk's forward end.
It does not necessarily imply any specific type of mechanical
connection between the forward fan shaft 128 and the fan disk 138,
or require any specific location of a mechanical joint between the
two components. In the example shown in FIG. 2, the forward fan
shaft 128 includes a tapered aft portion 152, a generally
cylindrical axial portion 154, and a flange 156 which extends
radially outward from the forward end of the axial portion 154. The
flange 156 is coupled to the disk arm 150 for rotation therewith,
for example using a bolted or splined connection. As a result, the
forward fan shaft 128 is substantially less stiff in bending than
the prior art design shown in FIG. 1).
[0021] The disk arm 150 shown in FIG. 2 could extend axially
forward or aft of the forward end 142 of the fan disk 138. The
angle and cross-sectional shape of the disk arm 150 may be varied
to provide a bending stiffness suitable for each particular
application. Also, while the forward fan shaft 128 is shown as
being a single integral component, it could be built up from two or
more sections joined together, for example using bolted joints.
[0022] FIG. 3 illustrates an alternative fan 212 and surrounding
structure, including a frame 246, fuse 248, and bearing 232. A
forward fan shaft 228 has a tapered aft portion 252 coupled to a
rear fan shaft 230 and a generally cylindrical axial portion 254.
An annular fan disk 238 carries fan blades 240 and has a forward
end 242 and aft end 244. An annular disk arm 250 extends generally
axially forward and radially inward from the forward end 242 of the
disk 238. The disk arm 250 has a forward portion 256 which extends
forward, then curves backward in a "C"-shape, and an aft portion
258 which extends generally axially aft. The aft portion 258 is
coupled to the forward fan shaft 228 for rotation therewith, for
example with a bolted or splined joint. The additional arc length
of the curved portion of the disk arm 250 provides an opportunity
to further increase and tune the flexibility of the forward fan
shaft 228. Alternatively, the additional curve and arc length could
be incorporated into the forward fan shaft 228 instead of the disk
arm 250. Furthermore, any of the fan shafts described herein could
me made all or partially integral with the fan disk.
[0023] In operation, the forward fan shaft design described herein
permits the fan rotor to safely windmill after a blade release
event while limiting the bending loads applied to the core. This
can be achieved without the need for any specific engine length or
bearing position requirements.
[0024] The foregoing has described load reduction device for a gas
turbine engine. 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. Accordingly,
the foregoing description of the preferred embodiment of the
invention and the best mode for practicing the invention are
provided for the purpose of illustration only and not for the
purpose of limitation, the invention being defined by the
claims.
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