U.S. patent application number 09/728796 was filed with the patent office on 2002-06-06 for method and apparatus for supporting rotor assembly bearings.
Invention is credited to Brown, Robert Burton, Ommundson, Peter Carl, Tardanico, Scott Albert.
Application Number | 20020067870 09/728796 |
Document ID | / |
Family ID | 24928310 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020067870 |
Kind Code |
A1 |
Ommundson, Peter Carl ; et
al. |
June 6, 2002 |
METHOD AND APPARATUS FOR SUPPORTING ROTOR ASSEMBLY BEARINGS
Abstract
A rotor assembly for a gas turbine engine including a bearing
assembly and a damper sub-assembly that facilitate reducing dynamic
motion to the rotor assembly is described. The bearing assembly
includes rolling elements positioned between a paired race. The
rotor assembly includes a rotor shaft supported by the bearing
assembly. The damper sub-assembly is radially outward from the
bearing assembly adjacent a sump housing, and includes a damper
insert. A predetermined preload force is applied to the rolling
elements. An outer race of the bearing assembly distorts to
substantially match a distortion pattern of the damper insert.
Inventors: |
Ommundson, Peter Carl;
(North Andover, MA) ; Brown, Robert Burton;
(Medford, MA) ; Tardanico, Scott Albert;
(Littleton, MA) |
Correspondence
Address: |
JOHN S. BEULICK
C/O ARMSTRONG TEASDALE LLP
ONE METROPOLITAN SQUARE
SUITE 2600
ST. LOUIS
MO
63102-2740
US
|
Family ID: |
24928310 |
Appl. No.: |
09/728796 |
Filed: |
December 1, 2000 |
Current U.S.
Class: |
384/99 ;
384/581 |
Current CPC
Class: |
Y10T 29/4932 20150115;
F16C 2360/23 20130101; F16C 27/045 20130101; F01D 25/164 20130101;
F16C 19/26 20130101 |
Class at
Publication: |
384/99 ;
384/581 |
International
Class: |
F16C 027/04 |
Claims
What is claimed is:
1. A method for assembling a gas turbine engine rotor assembly to
facilitate reducing dynamic loading of the rotor assembly, the
rotor assembly including a rotor shaft, a sump housing, a damper
sub-assembly, and a bearing assembly including an inner race, an
outer race, a plurality of rolling elements, a plurality of
springs, the rolling elements between the inner and outer races,
the damper subassembly including an annular damper insert, said
method comprising the steps of: supporting the rotor shaft on the
mounting frame with the bearing assembly; coupling the bearing
assembly outer race to the sump housing with the plurality of
springs; and coupling the damper sub-assembly within the engine
such that the bearing assembly outer race deflects during engine
operation to substantially match a distortion pattern of the damper
insert.
2. A method in accordance with claim 1 wherein the damper
subassembly damper insert includes an inner diameter and an outer
diameter, said step of coupling the damper sub-assembly further
comprises the step of coupling the damper sub-assembly to the
bearing assembly such that the bearing assembly outer race deflects
during engine operation to substantially match a distortion pattern
of the damper insert inner diameter.
3. A method in accordance with claim 2 wherein the sump housing has
a center, the bearing assembly outer race has a center, said step
of coupling the damper sub-assembly further comprising the step of
coupling the bearing assembly outer race to the damper sub-assembly
such that the rolling elements and the bearing assembly outer race
center are offset a radial distance from the sump housing
center.
4. A method in accordance with claim 2 further comprising the step
of providing an annular bearing assembly outer race that includes
at least one surface having a substantially elliptical
cross-sectional profile and at least one surface having a
substantially circular cross-sectional profile.
5. A method in accordance with claim 2 wherein said step of
coupling the bearing assembly outer race to the sump housing
further comprises the step of defining a clearance between the
bearing assembly and the damper insert.
6. Apparatus for a gas turbine engine rotor, said apparatus
comprising: a bearing assembly comprising an inner race, an outer
race, a plurality of rolling elements between said inner and outer
races, and configured to support the rotor, and a plurality of
springs extending from said outer race to secure said bearing
assembly within the gas turbine engine; and a damper sub-assembly
configured to dampen dynamic motion of the engine rotor, said
damper sub-assembly comprising an annular damper insert, said
damper sub-assembly coupled to said bearing assembly outer race
such that said bearing assembly outer race configured to deflect
during engine operation to substantially match a distortion pattern
of said damper insert.
7. Apparatus in accordance with claim 6 wherein said damper insert
comprises an inner diameter and an outer diameter, a portion of
said damper insert inner diameter in contact with said bearing
assembly outer race.
8. Apparatus in accordance with claim 7 further comprising a sump
housing adjacent said damper insert outer diameter, said bearing
assembly outer race further configured to deflect during engine
operation to substantially match a distortion pattern of said
damper insert inner diameter.
9. Apparatus in accordance with claim 8 wherein said outer race
coupled to said sump housing with said plurality of springs, said
sump housing has a center, said bearing assembly outer race has a
center, said rolling elements and said outer race center offset a
radial distance from said sump housing center.
10. Apparatus in accordance with claim 8 wherein at least one of
said bearing assembly inner race and said bearing assembly outer
race defines an elliptical cross-sectional profile.
11. Apparatus in accordance with claim 10 wherein said bearing
assembly inner race defines a substantially circular
cross-sectional profile, said bearing assembly outer race defines
an elliptical cross-sectional profile.
12. Apparatus in accordance with claim 11 wherein said bearing
assembly outer race coupled to said sump housing with said
plurality of springs, said bearing assembly comprising a plurality
of attachment points used to mount a seal and an oil jet.
13. A rotor assembly for a gas turbine engine, said rotor assembly
comprising: a rotor shaft; a bearing assembly configured to support
said rotor shaft on a mounting frame such that dynamic motion of
said rotor assembly is reduced, said bearing assembly comprising an
inner race, an outer race, a plurality of rolling elements, and a
plurality of springs, said rolling elements between said inner and
outer races; and a damper sub-assembly coupled to said bearing
assembly outer race and comprising an annular damper insert, said
bearing assembly outer race configured to deflect during engine
operation to substantially match a distortion pattern of said
damper insert.
14. A rotor assembly in accordance with claim 13 wherein said
bearing assembly comprises a plurality of attachment points used to
mount a seal and an oil jet.
15. A rotor assembly in accordance with claim 13 wherein said
bearing assembly coupled to a sump housing with said plurality of
springs, said damper insert comprises an outer diameter and an
inner diameter, said damper insert inner diameter adjacent said
bearing assembly.
16. A rotor assembly in accordance with claim 13 wherein said
damper insert comprises an inner diameter and an outer diameter,
said damper housing inner diameter adjacent said bearing assembly
bearing outer race, said damper housing outer diameter adjacent a
sump housing, said bearing assembly outer race configured to
deflect during engine operation to substantially match a distortion
pattern of said damper insert inner diameter.
17. A rotor assembly in accordance with claim 16 wherein said sump
housing has a center, said bearing assembly outer race has a
center, said bearing assembly outer race offset a distance from
said sump housing center.
18. A rotor assembly in accordance with claim 16 wherein at least
one of said bearing assembly inner race and said bearing assembly
outer race defines an elliptical cross-sectional profile.
19. A rotor assembly in accordance with claim 18 wherein said
bearing assembly inner race defines a substantially circular
cross-sectional profile, said bearing assembly outer race defines
an elliptical cross-sectional profile.
20. A rotor assembly in accordance with claim 19 wherein a
predetermined amount of preload force is applied to said bearing
assembly rolling elements.
Description
BACKGROUND OF THE INVENTION
[0001] This application relates generally to gas turbine engine
rotor assemblies and, more particularly, to bearing assemblies for
gas turbine engine rotor assemblies.
[0002] Gas turbine engines typically include a fan rotor assembly,
a compressor, and a turbine. The fan rotor assembly includes a fan
that includes an array of fan blades extending radially outward
from a rotor shaft. The rotor shaft transfers power and rotary
motion from the turbine to the compressor and the fan, and is
supported longitudinally with a plurality of bearing assemblies.
Bearing assemblies support the rotor shaft and typically include
rolling elements positioned within an inner race and an outer race.
The outer race is radially inward from a sump housing.
[0003] As the rotor is accelerated, non-synchronous vibration may
develop within the rotor assembly and be induced to the bearing
assemblies. Continued exposure to vibrational forces may result in
premature failure of the bearing assembly. To minimize potential
detrimental effects associated with such vibrations, at least some
known gas turbine engines include a damper assembly adjacent the
bearing assemblies to control rotor motion associated with
non-synchronous vibration. The damper assembly is positioned such
that a radial clearance is defined between the bearing assembly
outer race and the damper assembly to facilitate minimizing
vibrational forces being induced from the bearing assembly into the
mounting frame. Because the clearance is typically pre-set based on
geometric tolerances and thermal growth considerations, partial
part distortions may affect the damper clearance and may result in
rotor motion that is not damped.
BRIEF SUMMARY OF THE INVENTION
[0004] In an exemplary embodiment, a rotor assembly for a gas
turbine engine includes a bearing assembly and a damper
sub-assembly that facilitates reducing dynamic motion of the rotor
assembly. The bearing assembly includes a plurality of rolling
elements positioned between an inner and an outer race, and a
plurality of springs that couple the bearing assembly to a sump
housing. The sump housing extends between a damper insert and a
combustor casing. The rotor assembly includes a rotor shaft
supported by the bearing assembly and rotatably coupled to the
bearing assembly inner race. The damper sub-assembly includes the
damper insert which is coupled within the engine radially outward
from the bearing assembly.
[0005] During operation, as the rotor shaft rotates, the sump
housing distorts causing the damper insert to distort against the
sump housing. The damper subassembly facilitates reducing dynamic
motion of the rotor assembly. Specifically, the outer race deflects
to substantially match a distortion pattern of the damper insert
distorting against the sump housing, such that a variation in a
clearance defined between the bearing assembly and the damper
insert is facilitated to be reduced. More specifically, a portion
of the bearing assembly outer race in contact with the roller
elements deflects to match the distortion pattern of the damper
insert. As a result, the bearing assembly and the damper
sub-assembly facilitate reducing dynamic motion of the rotor
assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is schematic illustration of a gas turbine
engine;
[0007] FIG. 2 is a cross-sectional view of an exemplary embodiment
of a rotor assembly used in the gas turbine engine shown in FIG. 1
and including a bearing assembly;
[0008] FIG. 3 is a partial end view of the bearing assembly shown
in FIG. 2 illustrating an offset within the bearing assembly;
and
[0009] FIG. 4 is an alternative partial end view of the bearing
assembly shown in FIG. 2 illustrating an elliptical profile within
the bearing assembly; and
[0010] FIG. 5 is an enlarged side view of the bearing assembly
shown in FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
[0011] FIG. 1 is a schematic illustration of a gas turbine engine
10 including a low pressure compressor 12, a high pressure
compressor 14, and a combustor assembly 16. Engine 10 also includes
a high pressure turbine 18, and a low pressure turbine 20 arranged
in a serial, axial flow relationship. Compressor 12 and turbine 20
are coupled by a first shaft 24, and compressor 14 and turbine 18
are coupled by a second shaft 26. In one embodiment, engine 10 is a
CF34 engine commercially available from General Electric Company,
Cincinnati, Ohio and Lynn, Mass.
[0012] In operation, air flows through low pressure compressor 12
from an upstream side 32 of engine 10 and compressed air is
supplied from low pressure compressor 12 to high pressure
compressor 14. Compressed air is then delivered to combustor
assembly 16 where it is mixed with fuel and ignited. The combustion
gases are channeled from combustor 16 to drive turbines 18 and
20.
[0013] FIG. 2 is a cross-sectional view of an exemplary embodiment
of a rotor assembly 40 used with gas turbine engine 10 (shown in
FIG. 1). Rotor assembly 40 includes a rotor shaft 42. In one
embodiment, rotor shaft 42 is substantially similar to rotor shaft
26 (shown in FIG. 1). Rotor shaft 42 is rotatably coupled to a sump
housing 44 with a bearing assembly 46 that supports rotor shaft 42.
In one embodiment, bearing assembly 46 is known as an engine number
four bearing assembly.
[0014] In an exemplary embodiment, bearing assembly 46 includes a
paired race 50, a plurality of rolling elements 52, and a cage 53.
More specifically, paired race 50 includes an outer race 54 and an
inner race 56 radially inward from outer race 54. In one
embodiment, bearing assembly 46 includes thirty rolling elements
52. Each rolling element 52 is between inner race 56 and outer race
54, and in rolling contact with inner and outer races 56 and 54,
respectively. Furthermore, rolling elements 52 are spaced
circumferentially by cage 53.
[0015] Inner race 56 includes an outer diameter 70 and an inner
diameter 72. Inner race outer diameter 70 receives each rolling
element 52 in rollable contact. Inner race 56 is secured adjacent
rotor shaft 42 such that inner race inner diameter 72 is adjacent
rotor shaft 42.
[0016] Bearing outer race 54 is annular and includes an inner
diameter 76 and an outer diameter 78. Bearing outer race inner
diameter 76 includes a recess 80 that receives rolling elements 52
in rollable contact. Bearing assembly 46 is secured in position
relative to engine 10 with a plurality of springs 84 extending
between a mounting flange 86 and bearing outer race 54. In one
embodiment, springs 84 are double-tapered beams that extend
circumferentially in a row around rotor shaft 42. Each spring 84
includes a forward end 88 and an aft end 90. Each spring forward
end 88 extends from bearing outer race 54, and each spring aft end
90 extends from mounting flange 86. More specifically, each spring
forward end 88 extends from a downstream side 92 of bearing outer
race 54.
[0017] A damper sub-assembly 96 is coupled within engine 10
radially outward from bearing outer race 54 to limit radial motion
of bearing assembly 46. Damper subassembly 96 includes an annular
damper insert 98. Damper insert 98 includes an outer diameter 100,
an inner diameter 102 and a body 104 extending therebetween. Damper
insert 98 is coupled within engine 10, such that damper insert
inner diameter 102 is adjacent bearing outer race outer diameter
78, and damper insert outer diameter 100 is adjacent sump housing
44. More specifically, sump housing 44 includes an annular support
flange 110 sized to receive damper insert outer diameter 100.
Damper insert inner diameter 102 has a width 112 that is less than
a width 114 of bearing outer race outer diameter 78. Bearing outer
race 54 also has width 116 at bearing outer race inner diameter
76.
[0018] Damper insert 98 provides a distribution flow path for oil
to enter an annulus formed between damper insert and bearing outer
race 54. The oil functions as a damper within damper sub-assembly
96. More specifically, damper insert inner diameter 102 forms an
outer surface of the damper, and bearing outer race outer diameter
78 forms an inner surface of the damper.
[0019] During assembly of rotor assembly 40, rotor shaft 42 is
supported on sump housing 44 with bearing assembly 46. More
specifically, rotor shaft 42 is rotatably coupled to sump housing
44 with bearing assembly 46. Each bearing assembly inner race 56 is
positioned adjacent rotor shaft 42 and roller elements 52 are
secured between races 54 and 56. More specifically, springs 84
control a radial spring rate of bearing outer race 54 to determine
a level of rotor loads induced through bearing assembly 46. The
controlled spring rate is variable and is selected based on a
plurality of considerations including, but not limited to bearing
loading, bearing life, rotor dynamics, and rotor deflection
considerations.
[0020] During operation of engine 10, as rotor assembly 40 rotates,
sump housing 44 distorts causing damper insert 98 to distort with
sump housing 44. More specifically, damper insert inner diameter
102 distorts with sump housing 44. Specifically, bearing assembly
outer race 54 deflects, as described below, to substantially match
a distortion pattern of damper insert inner diameter 102, such that
a clearance between bearing assembly outer race 54 and damper
insert 98 is facilitated to be uniform. More specifically, bearing
assembly outer race outer diameter 78 deflects to match the
distortion pattern of damper insert inner diameter 102.
Accordingly, clearance variation between damper sub-assembly 96 and
bearing assembly 46 is reduced.
[0021] FIG. 3 is a partial end view of bearing assembly 46
illustrating an offset preset within bearing assembly 46. Sump
housing 44 is annular and includes a first axis of symmetry 120 and
a second plane of symmetry 122 that is substantially perpendicular
to first axis of symmetry 120. First axis of symmetry 120 extends
radially through engine 10 (shown in FIG. 1), and second plane of
symmetry 122 extends axially through engine 10. A center 124 of
sump housing 44 is defined at an intersection of axis of symmetry
120 and plane of symmetry 122. A center of engine 10 (shown in FIG.
1) is substantially concentric with center 124.
[0022] As seen in FIG. 3, bearing assembly outer race 54 defines a
substantially circular profile and has a center 130. Each rolling
element 52 has a substantially circular cross sectional profile,
and when assembled, rolling elements 52 define a substantially
circular cross-sectional profile. Bearing assembly center 130 is
defined similarly to sump housing center 124, and is located on an
axis of symmetry 132 of bearing outer race 54.
[0023] During assembly of rotor assembly 40, to facilitate bearing
outer race 54 developing desired deflection, bearing outer race 54
is offset from sump housing 44. More specifically, bearing outer
race 54 is mounted such that bearing outer race is offset a radial
distance 134 outward from sump housing center 124. In one
embodiment, bearing outer race center 130 is offset from sump
housing center 124 a distance 134 that is approximately equal 0.001
inches.
[0024] Accordingly, during assembly, a weight of rotor 40 (shown in
FIG. 2) causes bearing assembly 46 to be centered within damper
sub-assembly 96. More specifically, the weight of rotor assembly 40
also forces bearing assembly 46 to be centered within damper insert
98, such that a center (not shown) of damper insert 98 is
substantially concentric with bearing assembly center 130.
[0025] FIG. 4 is an alternative partial end view of an alternative
embodiment of a bearing assembly 46 illustrating an elliptical
profile within bearing assembly 46. More specifically, bearing
assembly outer race inner diameter 76 has a substantially
elliptical cross-sectional profile. In one embodiment, bearing
outer race inner diameter 76 is machined to define the elliptical
profile. More specifically, the elliptical pattern defined includes
a major axis 206 that is phased to match a distortion pattern of
damper insert inner diameter 102 (shown in FIG. 2).
[0026] Accordingly, because bearing assembly outer race inner
diameter 76 defines a substantially round cross-sectional profile,
as rotor assembly 40 (shown in FIGS. 2 and 3) increases rotational
speed, an operating temperature of bearing assembly 46 also
increases. As a result, an amount of desired deflection of outer
race outer diameter 78 is obtained, thus facilitating reducing
damper clearance variations and improving effectiveness of the
damper.
[0027] FIG. 5 is an enlarged side view of bearing assembly 46
including springs 84. Bearing assembly 46 also includes a plurality
of attachment points 220. More specifically, a first attachment
point 222 extends forward from bearing mounting flange 86 and
permits an oil nozzle or oil jet (not shown) to be coupled to
bearing assembly 46. A plurality of second attachment points 226
extend aftward from mounting flange 86 to permit a carbon seal to
be coupled to bearing assembly 46.
[0028] The above-described rotor assembly is cost-effective and
highly reliable. The rotor assembly includes a bearing assembly and
a damper sub-assembly. The bearing assembly is secured to the sump
housing with the plurality of double-tapered springs. The damper
sub-assembly facilitates reducing rotor dynamic motion induced to
the bearing assembly. Specifically, because the bearing assembly
outer race deflects to substantially match a distortion pattern of
the damper sub-assembly damper insert, a clearance between the
bearing assembly and the damper insert is uniform. Accordingly,
damper clearance variation between the bearing assembly and the
damper insert is reduced. As a result, the bearing assembly
facilitates reducing rotor assembly dynamic motion in a
cost-effective and reliable manner.
[0029] While the invention has been described in terms of various
specific embodiments, those skilled in the art will recognize that
the invention can be practiced with modification within the spirit
and scope of the claims.
* * * * *