U.S. patent number RE38,373 [Application Number 09/900,775] was granted by the patent office on 2003-12-30 for compliant foil fluid film thrust bearing with a tilting pad underspring.
This patent grant is currently assigned to Capstone Turbine Corporation. Invention is credited to Robert W. Bosley.
United States Patent |
RE38,373 |
Bosley |
December 30, 2003 |
**Please see images for:
( Certificate of Correction ) ** |
Compliant foil fluid film thrust bearing with a tilting pad
underspring
Abstract
A compliant foil fluid film thrust bearing including a thrust
disk rotor, fluid foils, spring foils, a thrust plate, and a
housing thrust surface The non-rotating but compliant fluid foils,
mounted on the thrust plate and/or housing thrust surface and
positioned adjacent to the thrust disk, have open faced channels
that induce regenerative vortex flow patterns in the process fluid.
The multiple spring foils together provide a tilting pad support
for the fluid foils but allow them to follow the axial and
overturning motion of the thrust disk. The interaction of the
tilting pad underspring supports and the circumferential fluid
pressure gradients in the process fluid between the fluid foils and
the thrust disk rotor assure that the fluid foils will assume
hydrodynamically efficient convex shapes on the surfaces adjacent
to the rotor regardless of the load applied to the thrust
bearing.
Inventors: |
Bosley; Robert W. (Cerritos,
CA) |
Assignee: |
Capstone Turbine Corporation
(Chatsworth, CA)
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Family
ID: |
25464364 |
Appl.
No.: |
09/900,775 |
Filed: |
July 6, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
933695 |
Sep 19, 1997 |
05918985 |
Jul 6, 1999 |
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Current U.S.
Class: |
384/106;
384/105 |
Current CPC
Class: |
F01D
25/168 (20130101); F16C 17/042 (20130101); F16C
27/02 (20130101); F05D 2240/52 (20130101); F05D
2240/53 (20130101); F05D 2220/40 (20130101); F16C
2360/24 (20130101) |
Current International
Class: |
F01D
25/16 (20060101); F16C 17/00 (20060101); F16C
17/12 (20060101); F16C 032/06 () |
Field of
Search: |
;384/103,105,106,122,124 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Foil Air/Gas Bearing Technology--An Overview," Giri Agrawal, The
American Society of Mechanical Engineers, Jun. 1997, pp. 1-11.
.
"Foil Gas Bearings for Turbomachinery," Giri Agrawal, The
Engineering Society for Advancing Mobility Land Sear Air and Space,
SAE Technical Paper Series, Jul. 1990..
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Primary Examiner: Hannon; Thomas R.
Attorney, Agent or Firm: Sterne, Kessler, Goldstein &
Fox
Claims
What I claim is:
1. A method of rotatably supporting a thrust disk on a thrust plate
comprising the steps of: providing a compliant foil bearing between
said thrust disk and said thrust plate, said compliant foil bearing
including an annular compliant fluid foil member having a plurality
of converging ramps and diverging joggles to form alternating
converging and diverging wedge channels on the surface of said
annular compliant fluid foil member facing said thrust disk;
mounting a spring foil member between said compliant fluid foil
bearing member and said thrust plate; providing said spring foil
member with a plurality of spring foil elements having a number of
narrow width spring foils and a plurality of spring foil elements
having a number of wide spring pads; and creating a tilting pad
support for said compliant fluid foil bearing member by alternating
individual ones of said plurality of said narrow width spring foil
elements and individual ones of said plurality of wide spring pad
spring foil elements.
2. A compliant foil fluid film thrust bearing comprising: a thrust
disk rotatably supported by a non-rotating thrust bearing surface;
and a compliant foil bearing operably disposed between said
rotatable thrust disk and said non-rotating thrust bearing surface
and mounted on said thrust bearing surface, said compliant foil
bearing including a fluid film member having a plurality of
converging ramps and diverging joggles to form alternating
converging and diverging wedge channels on the surface of said
compliant fluid foil member facing said rotatable thrust disk, and
a spring foil member mounted on said thrust bearing surface and
disposed between said thrust bearing surface and said fluid foil
member, said spring foil member including means to form a tilting
pad support for said fluid foil member.
3. The compliant foil fluid film bearing of claim 2 wherein said
means to form a tilting pad support for said fluid foil member has
circumferentially closer spacing between support/pivot lines moving
up the individual converging ramps of said fluid foil member to the
trailing edge of the individual converging ramps of said fluid foil
member.
4. The compliant foil fluid film bearing of claim 3 wherein said
support/pivot lines moving up the individual converging ramps of
said fluid foil member to the trailing edge of the individual
converging ramps of said fluid foil member number three.
5. The compliant foil fluid film bearing of claim 3 wherein said
support/pivot lines moving up the individual converging ramps of
said fluid foil member to the trailing edge of the individual
converging ramps of said fluid foil member number four.
6. The compliant foil fluid film bearing of claim 2 wherein said
means to form a tilting pad support for said fluid foil member has
increasing support forces and support spring rates moving up the
individual converging ramps of said fluid foil member to the
trailing edge of the individual converging ramps of said fluid foil
member.
7. The compliant foil fluid film bearing of claim 2 wherein said
means to form a tilting pad support for said fluid foil member
assures retention of a reasonably hydrodynamically optimized scoop
shape for the individual converging ramps of said fluid foil member
over a wide range of bearing operating speeds and bearing thrust
loads.
8. A compliant foil fluid film thrust bearing comprising: a thrust
disk rotatably supported by said thrust bearing surface; and a
compliant foil bearing operably disposed between said rotatable
thrust disk and said thrust bearing surface and mounted on said
thrust bearing surface, said compliant foil bearing including a
fluid foil member having a plurality of converging ramps and
diverging joggles to form alternating converging and diverging
wedge channels on the surface of said compliant fluid foil member
facing said rotatable thrust disk, and a spring foil member mounted
on said thrust bearing surface and disposed between said thrust
bearing surface and said fluid foil member, said spring foil member
including means to provide narrow pivot supports and to provide
flexure and tilting supports for said fluid foil member.
9. The compliant foil fluid film bearing of claim 8 wherein said
narrow pivot supports are radially curved.
10. The compliant foil fluid film bearing of claim 9 wherein said
narrow pivot supports have a generally chevron shape with a
generally blunt nose.
11. The compliant foil fluid film bearing of claim 8 wherein said
narrow pivot supports are radially straight..[.
12. A compliant foil fluid film thrust bearing comprising: a thrust
disk rotatably supported by said thrust bearing surface; and a
compliant foil bearing operably disposed between said rotatable
thrust disk and said thrust bearing surface and mounted on said
thrust bearing surface, said compliant foil bearing including a
fluid foil member having a plurality of converging ramps and
diverging wedge channels on the surface of said compliant fluid
foil member facing said rotatable thrust disk, and a spring foil
member mounted on said thrust bearing surface and disposed between
said thrust bearing surface and said fluid foil member, said spring
foil member including a plurality of narrow width spring foil
elements and at least one wide spring pad element with said wide
spring elements disposed between adjacent narrow width spring foil
elements to form a tilting pad support for said fluid foil
member..].
13. .[.The compliant foil fluid film bearing of claim 12.]. .Iadd.A
compliant foil fluid film thrust bearing comprising: a thrust disk
rotatably supported by said thrust bearing surface; and a compliant
foil bearing operably disposed between said rotatable thrust disk
and said thrust bearing surface and mounted on said thrust bearing
surface, said compliant foil bearing including a fluid film member
having a plurality of converging ramps and diverging joggles to
form alternating converging and diverging wedge channels on the
surface of said compliant fluid foil member facing said rotatable
thrust disk, and a spring foil member mounted on said thrust
bearing surface and disposed between said thrust bearing surface
and said fluid foil member, said spring foil member including a
plurality of narrow width spring foil elements and at least one
wide spring pad element with said wide spring elements disposed
between adjacent narrow width spring foil elements to form a
tilting pad support for said fluid foil member,.Iaddend. wherein
said spring foil member includes three narrow width spring foil
elements and two wide spring pad elements.
14. A compliant foil fluid film thrust bearing comprising: a thrust
disk rotatably supported by said thrust bearing surface; and a
compliant foil bearing operably disposed between said rotatable
thrust disk and said thrust bearing surface and mounted on said
thrust bearing surface, said compliant foil bearing including a
fluid foil member having a plurality of converging ramps and
diverging joggles to form alternating converging and diverging
wedge channels on the surface of said compliant fluid foil member
facing said rotatable thrust disk, and a spring foil member mounted
on said thrust bearing surface and disposed between said thrust
bearing surface and said fluid foil member, said spring foil member
including means to provide single narrow pivot supports and single
flexure and tilting supports for said fluid foil member, pairs of
pivot supports and pairs of flexure and titling supports, and trios
of narrow pivot supports, said single narrow pivot supports, single
flexure and tilting supports, pairs of pivot supports, pairs of
flexure and titling supports, and trios of narrow pivot supports
sequentially arranged together to form a tilting pad support for
said fluid foil member.
15. A compliant foil fluid film thrust bearing comprising: a
bearing housing having a thrust bearing surface and a generally
opposed thrust bearing plate; a shaft rotatably supported within
said bearing housing and including a thrust disk radially extending
between said thrust bearing surface and said opposed thrust bearing
plate; a pair of annular compliant fluid foil members with one of
said pair of members disposed on either side of said thrust disk
and each of said pair of annular compliant fluid foil members
including a plurality of converging ramps and diverging joggles to
form alternating converging and diverging wedge channels on the
surface facing said thrust disk; a pair of annular spring foil
members with one of said pair of members disposed between an
annular compliant fluid foil member and said thrust bearing surface
and the other of said pair of annular spring foil members disposed
between said other of said pair of annular compliant fluid foil
members and said thrust bearing plate and each of said annular
spring foil members including means to form a tilting pad support
for said fluid foil member.
16. The compliant foil fluid film bearing of claim 15 wherein the
periphery of each of said pair of annular compliant fluid foil
members includes a self-shimming peripheral ring and the periphery
of each of said pair of annular spring foil members includes a
self-shimming peripheral ring: in addition a bearing spacer
disposed between said pair of annular compliant fluid foil members
at the outer periphery of said thrust disk and said bearing spacer
having an axial thickness slightly greater than the axial thickness
of said thrust disk such that the thickness of said pair of annular
compliant fluid foil member peripheral rings, the thickness of said
pair of annular spring foil member peripheral rings and the
thickness of said bearing spacer together establishing a clearance
between the annular compliant fluid foil elements and said rotating
thrust disk; and wherein each of said pair of annular compliant
fluid foil members and each of said pair of annular spring foil
members include a plurality of peripheral tabs having indexing
openings therein and, in addition, said bearing includes a like
plurality of pins with individual pins extending from said bearing
housing through said annular compliant fluid foil members, said
annular spring foil members, said bearing spacer and into said
thrust bearing plate.
17. The compliant foil fluid film thrust bearing of claim 15
wherein said pair of annular spring foil members includes spring
foil elements which have arcuate dams at the radially outward and
radially inward periphery of said tilting pad supports.
18. The compliant foil fluid film thrust bearing of claim 15
wherein said converging wedge channels are generally scoop shaped
chevrons.
19. The compliant foil fluid film thrust bearing of claim 18
wherein said spring foil members includes a plurality of narrow
width spring foil elements and at least one wide spring pad element
with said wide spring elements disposed between adjacent narrow
width spring foil elements to form a tilting pad support for said
fluid foil member.
20. The compliant foil fluid film thrust bearing of claim 18
wherein said spring foil members include means to provide single
narrow pivot supports and single flexure and tilting supports for
said fluid foil member, pairs of pivot supports and pairs of
flexure and titling supports, and trios of narrow pivot supports,
said single narrow pivot supports, single flexure and tilting
supports, pairs of pivot supports, pairs of flexure and titling
supports, and trios of narrow pivot supports sequentially arranged
together to form a tilting pad support for said fluid foil
member.
21. The compliant foil fluid film thrust bearing of claim 18
wherein said spring foil members include: a plurality of first
narrow pivot supports; a plurality of first wide flexure and
tilting support pads having a trailing edge and a leading edge,
with a first narrow pivot support pivotably supporting a first wide
support pad intermediate the trailing edge and the leading edge of
said first wide flexure and tilting support pad; a plurality of
pairs of second narrow pivot supports, with the trailing of a pair
of second narrow pivot supports disposed on the trailing edge of a
first wide flexure and tilting support pad and the leading of said
pair of second narrow pivot supports disposed on the leading edge
of a first wide flexure and tilting support pad; a plurality of
pairs of second wide flexure and tilting support pads each having a
trailing edge and a leading edge, with the trailing of a pair of
second narrow pivot supports pivotably supporting the trailing of a
pair of second wide flexure and tilting support pads intermediate
the trailing edge and the leading edge of said second wide flexure
and tilting support pad and the leading of said pair of second
narrow pivot supports pivotably supporting the leading of said pair
of second wide flexure and tilting support pads intermediate the
trailing edge and the leading edge of said second wide flexure and
tilting support pad; and a plurality of trios of third narrow pivot
supports, with one of a trio of third narrow pivot supports
disposed on the trailing edge of the trailing of said pair of
second wide flexure and tilting support pads, one of said trio of
third narrow pivot supports disposed on the leading edge of by
trailing of said pair of second wide flexure and tilting support
pads, and one of said trio of third narrow pivot supports disposed
on the trailing edge of the leading of said pair of second wide
flexure and tilting support pads, each of said generally scoop
shaped chevrons supported by a trio of third narrow pivot supports
and the leading edge of the leading of said pair of second wide
flexure and tilting support pads.
22. The compliant foil fluid film thrust bearing of claim 21
wherein said first narrow pivot support pivotably supports said
first wide flexure and tilting support pad closer to the trailing
edge of said first wide flexure and tilting support pad than to the
leading edge of said first wide flexure and tilting support pad,
the trailing of a pair of second narrow pivot supports pivotably
supports the trailing of a pair of second wide flexure and tilting
support pads closer to trailing edge of said second wide flexure
and tilting support pad than to the leading edge of said second
wide flexure and tilting support pad, and the leading of said pair
of second narrow pivot supports pivotably supports the leading of
said pair of second wide flexure and tilting support pads closer to
trailing edge of said second wide flexure and tilting support pad
than to the leading edge of said second wide flexure and tilting
support pad.
23. The compliant foil fluid film thrust bearing of claim 21
wherein said first narrow pivot support pivotably supports said
first wide flexure and tilting support pad closer to the trailing
edge of said first wide flexure and tilting support pad than to the
leading edge of said first wide flexure and tilting support pad,
the trailing of a pair of second narrow pivot supports pivotably
supports the trailing of a pair of second wide flexure and tilting
support pads closer to trailing edge of said second wide flexure
and tilting support pad than to the center said second wide flexure
and tilting support pad, and the leading of said pair of second
narrow pivot supports pivotably supports the leading of said pair
of second wide flexure and tilting support pads closer to trailing
edge of said second wide flexure and tilting support pad than to
the center of said second wide flexure and tilting support pad.
24. The compliant foil fluid film thrust bearing of claim 15
wherein said converging wedge channels are generally annular
segments having a radial leading edge and a radial trailing
edge.
25. The compliant foil fluid film thrust bearing of claim 24
wherein said spring foil members include means to provide single
narrow pivot supports and single flexure and tilting supports for
said fluid foil member, pairs of pivot supports and pairs of
flexure and titling supports, and trios of narrow pivot supports,
said single narrow pivot supports, single flexure and tilting
supports, pairs of pivot supports, pairs of flexure and titling
supports, and trios of narrow pivot supports sequentially arranged
together to form a tilting pad support for said fluid foil
member.
26. The compliant foil fluid film thrust bearing of claim 24
wherein said spring foil members include: a plurality of first
narrow pivot supports; a plurality of first wide flexure and
tilting support pads having a trailing edge and .Iadd.a
.Iaddend.leading edge, with a first narrow pivot support pivotably
supporting a first wide support pad intermediate the trailing edge
and the leading edge of said first wide flexure and tilting support
pad; a plurality of pairs of second narrow pivot supports, with the
trailing of a pair of second narrow pivot supports disposed on the
trailing edge of a first wide flexure and tilting support pad and
the leading of said pair of second narrow pivot supports disposed
on the leading edge of a first wide flexure and tilting support
pad; a plurality of pairs of second wide flexure and tilting
support pads each having a trailing edge and a leading edge, with
the trailing of a pair of second narrow pivot supports pivotably
supporting the trailing of a pair of second wide flexure and
tilting support pads intermediate the trailing edge and the leading
edge of said second wide flexure and tilting support pad and the
leading of said pair of second narrow pivot supports pivotably
supporting the leading of said pair of second wide flexure and
tilting support pads intermediate the trailing edge and the leading
edge of said second wide flexure and tilting support pad; and a
plurality of trios of third narrow pivot supports, with one of a
trio of third narrow pivot supports disposed on the trailing edge
of the trailing of said pair of second wide flexure and tilting
support pads, one of said trio of third narrow pivot supports
disposed on the leading edge of the trailing of said pair of second
wide flexure and tilting support pads, and one of said trio of
third narrow pivot supports disposed on the trailing edge of the
leading of said pair of second wide flexure and tilting support
pads, each of said radially sided annular segments supported by a
trio of third narrow pivot supports and the leading edge of the
leading of said pair of second wide flexure and tilting support
pads.
27. The compliant foil fluid film thrust bearing of claim 26
wherein said first narrow pivot support pivotably supports said
first wide flexure and tilting support pad closer to the trailing
edge of said first wide flexure and tilting support pad than to the
leading edge of said first wide flexure and tilting support pad,
the trailing of a pair of second narrow pivot supports pivotably
supports the trailing of a pair of second wide flexure and tilting
support pads closer to trailing edge of said second wide flexure
and tilting support pad than to the leading edge of said second
wide flexure and tilting support pad, and the leading of said pair
of second narrow pivot supports pivotably supports the leading of
said pair of second wide flexure and tilting support pads closer to
trailing edge of said second wide flexure and tilting support pad
than to the leading edge of said second wide flexure and tilting
support pad.
28. The compliant foil fluid film thrust bearing of claim 26
wherein said first narrow pivot support pivotably supports said
first wide flexure and tilting support pad closer to the trailing
edge of said first wide flexure and tilting support pad than to the
leading edge of said first wide flexure and tilting support pad,
the trailing of a pair of second narrow pivot supports pivotably
supports the trailing of a pair of second wide flexure and tilting
support pads closer to trailing edge of said second wide flexure
and tilting support pad than to the center said center wide flexure
and tilting support pad, and the leading of said pair of second
narrow pivot supports pivotably supports the leading of said pair
of second wide flexure and tilting support pads closer to trailing
edge of said second wide flexure and tilting support pad than to
the center of said second wide flexure and tilting support pad.
29. The compliant foil fluid film thrust bearing of claim 24
wherein said spring foil members includes a plurality of narrow
width spring foil elements and at least one wide spring pad element
with said wide spring elements disposed between adjacent narrow
width spring foil elements to form a tilting pad support for said
fluid foil member..Iadd.
30. A compliant foil thrust bearing comprising: an aerofoil disk
having a plurality of fluid foils; and a spring assembly providing
flex and tilt support to the plurality of fluid foils comprising at
least one independent flex and tilt support..Iaddend..Iadd.
31. The thrust bearing of claim 30 wherein the aerofoil disk
further comprises: a shim ring having an inner diameter; a
plurality of fluid foils formed on an annular ring concentric with
the shim ring and having a smaller diameter than the shim ring
inner diameter; a plurality of web elements, each web element
connecting the shim ring and the plurality of fluid
foils..Iaddend..Iadd.
32. The thrust bearing of claim 30 wherein the spring assembly
further comprises: means for supporting each of the plurality of
fluid foils; first means for providing flex and tilt support for
the means for supporting each of the plurality of fluid foils;
first means for providing pivotal support for the first means for
providing flex and tilt support; second means for providing flex
and tilt support for the first means for providing pivotal support;
and second means for providing pivotal support for the second means
for providing flex and tilt support..Iaddend..Iadd.
33. The thrust bearing of claim 30 wherein the spring assembly
further comprises: a plurality of spring foils
disks..Iaddend..Iadd.
34. The thrust bearing of claim 33 wherein each of the plurality of
spring foil disks further comprises: a shim ring having an inner
diameter; a plurality of support elements formed concentric with
the shim ring and within the shim ring inner diameter; a plurality
of web elements, each web element connecting the shim ring and one
of the plurality of support elements..Iaddend..Iadd.
35. The thrust bearing of claim 30 wherein the spring assembly
further comprises: a plurality of foil supports; a plurality of
first flex and tilt supports, each first flex and tilt support
supporting one or two of the plurality of foil supports; a
plurality of first pivot supports, each first pivot support
supporting one of the plurality of first flex and tilt supports; a
plurality of second flex and tilt supports, each second flex and
tilt support supporting two of the plurality of first pivot
supports; and a plurality of second pivot supports, each second
pivot support supporting one of the plurality of second flex and
tilt supports..Iaddend..Iadd.
36. The thrust bearing of claim 35 wherein: the plurality of foil
supports are generally radial; the plurality of first pivot
supports are generally radial; and the plurality of second pivot
supports are generally radial..Iaddend..Iadd.
37. The thrust bearing of claim 30 wherein said bearing is
hydrodynamic..Iaddend..Iadd.
38. The thrust bearing of claim 30 wherein said bearing is
hydrostatic..Iaddend..Iadd.
39. A compliant foil thrust bearing comprising: a fluid foil member
having a plurality of fluid foils; a spring assembly providing flex
and tilt support to the plurality of fluid foils comprising at
least one independent flex and tilt support..Iaddend..Iadd.
40. The thrust bearding of claim 39 wherein the fluid foil member
further comprises: a shim ring having an inner diameter; a
plurality of fluid foils formed on an annular ring concentric with
the shim ring and having a smaller diameter than the shim ring
inner diameter; a plurality of web elements, each web element
connecting the shim ring and the plurality of fluid
foils..Iaddend..Iadd.
41. The thrust bearing of claim 39 wherein the spring assembly
further comprises: means for supporting each of the plurality of
fluid foils; first means for providing flex and tilt support for
the means for supporting each of the plurality of fluid foils;
first means for providing pivotal support for the first means for
providing flex and tilt support; second means for providing flex
and tilt support for the first means for providing pivotal support;
and second means for providing pivotal support for the second means
for providing flex and tilt support..Iaddend..Iadd.
42. The thrust bearding of claim 39 wherein the spring assembly
further comprises: a plurality of spring foil
disks..Iaddend..Iadd.
43. The thrust bearding of claim 42 wherein each of the plurality
of spring foil disks further comprises: a shim ring having an inner
diameter; a plurality of support elements formed concentric with
the shim ring and within the shim ring inner diameter; a plurality
of web elements, each web element connecting the shim ring and one
of the plurality of support elements..Iaddend..Iadd.
44. The thrust bearing of claim 39 wherein the spring assembly
further comprises: a plurality of foil supports; a plurality of
first flex and tilt supports, each first flex and tilt support
supporting one or two of the plurality of foil supports; a
plurality of first pivot supports, each first pivot support
supporting one of the plurality of first flex and tilt supports; a
plurality of second flex and tilt supports, each second flex and
tilt support supporting two of the plurality of first pivot
supports; and a plurality of second pivot supports, each second
pivot support supporting one of the plurality of second flex and
tilt supports..Iaddend..Iadd.
45. The thrust bearing of claim 44 wherein: the plurality of foil
supports are generally radial; the plurality of first pivot
supports are generally radial; and the plurality of second pivot
supports are generally radial..Iaddend..Iadd.
46. The thrust bearing of claim 39 wherein said bearing is
hydrodynamic..Iaddend..Iadd.
47. The thrust bearing of claim 39 where said bearing is
hydrostatic..Iaddend.
Description
TECHNICAL FIELD
This invention relates to the general field of compliant foil fluid
film bearings and more particularly to an improved thrust bearing
employing fluid foils and multiple spring foils to support,
position, damp and accommodate movements or excursions of the
rotating portion of the bearing.
BACKGROUND OF THE INVENTION
Compliant foil fluid film thrust bearings are currently being
utilized in a variety of high speed rotor applications. These
bearings are generally comprised of a two sided thrust disk
rotating element, non-rotating compliant fluid foil members that
axially enclose the rotating element, non-rotating compliant spring
foil members that axially enclose the fluid foil members and a
non-rotating thrust plate element and a non-rotating housing
element that axially enclose and provide attachments for the foil
members. The space between the rotating element and the thrust
plate element on one side of the bearing and the space between the
rotating element and the thrust surface of the housing element on
the other side of the bearing are filled with fluid (usually air)
which envelops the foils.
The rotary motion of the rotating element applies viscous drag
forces to the fluid and induces circumferential flow of the fluid
between the smooth surface of the rotating element and the fluid
foil. The space between the rotating element and the fluid foil is
subdivided into a plurality of fluid-dynamic wedge channels. These
wedge channels have typically been formed by resistance welding
compliant, convex curved foil pads to an underlying support foil.
The leading ramps of the foil pads relative to the fluid's
circumferential flow and the smooth surface of the rotating element
form the two primary surfaces of the converging wedge channels. The
trailing ramps and the smooth surface of the rotating element form
the primary surfaces of the diverging wedge channels. The fluid
flowing circumferentially along a converging wedge channel
experiences steadily decreasing flow area, increasing
circumferential flow velocity and increasing static fluid pressure.
If the rotating element moves toward the non-rotating element, the
convergence angle of the wedge channel increases causing the fluid
pressure rise along the channel to increase. If the rotating
element moves away, the pressure rise along the wedge channel
decreases. Thus, the fluid in the wedge channels exerts restoring
forces on the rotating element that vary with and stabilize running
clearances and prevent contact between the rotating and
non-rotating elements of the bearing. Flexing and sliding of the
foils causes coulomb damping of any axial or overturning motion of
the rotating element of the bearing.
Owing to preload spring forces or gravity forces, the rotating
element of the bearing is typically in physical contact with the
fluid foil members of the bearing at low rotational speeds. This
physical contact results in bearing wear. It is only when the rotor
speed is above what is termed the lift-off/touch-down speed that
the fluid dynamic forces generated in the wedge channels assure a
running gap between the rotating and non-rotating elements.
Conventional, compliant foil fluid film thrust bearings have fluid
dynamic wedge channel ramps that converge or diverge
circumferentially with no radial component to the ramp slopes. The
converging wedge channel ramps have no side wall or other
constraints to prevent fluid flow out of the channels at their
inner and outer edges. At the trailing edge of the converging wedge
channel, the high fluid pressure and lack of radial flow
constraints induces radial flow leakage out of the channel, which
in turn, results in a reduction in fluid pressure, a loss in
bearing load capacity, and an increase in bearing drag. The radial
flow leakage requires make-up flow at the beginning of the
converging wedge channel.
Conventional, compliant foil fluid film thrust bearings have
primary fluid flow patterns in the converging wedge channels that
are single path recirculating loops. The fluid in the converging
wedge channels adjacent to the rotating disk travels
circumferentially in the same direction as the disk's motion (up
the ramp) owing to viscous drag. The fluid in the converging wedge
channels adjacent to the non-rotating fluid foil
travels-circumferentially in the direction opposite to the disk's
motion (down the ramp) owing to the circumferential pressure
gradient along the channel. Much of the fluid that travels up the
ramp near the disk while gaining static pressure turns back before
reaching the end of the wedge channel and travels down the ramp
near the fluid foil while losing pressure. Almost all of this fluid
turns again before reaching the beginning of the wedge channels and
travels up the ramp while again gaining pressure. The fluid
traveling the single path recirculating loop flow patterns travels
essentially the same path each loop and experiences the same
pressure increases and pressure decreases each loop with no net
pressure gain from one loop to the next. These bearings generate
less fluid dynamic pressure and have less load capacity than
bearings that utilize multi-path vortex flow patterns where the
flow traveling each regenerative loop travels a different path and
where there is a net increase in fluid pressure each loop
Conventional, compliant foil fluid film thrust bearings operate
with extremely small running clearances and moderate as opposed to
low drag and power consumption. The clearances between the
non-rotating fluid foil's converging channel ramp trailing ends and
the rotating thrust disk are typically less than 100 micro-inches
when the bearing is heavily loaded at operating conditions. The
bearing's drag coefficient is typically more than 0.005 at
operating speed as defined by the ratio of the fluid dynamic drag
induced shear forces applied to the disk by the bearing divided by
the thrust load carried by the bearing.
Compliant foil fluid film thrust bearings tend to rely on backing
springs to preload the fluid foils against the relatively moveable
rotating element (thrust disk) so as to control foil
position/nesting and to establish foil dynamic stability. The
bearing starting torque (which should ideally be zero) is directly
proportional to these preload forces. These preload forces also
significantly increase the disk speed at which the hydrodynamic
effects in the wedge channels are strong enough to lift the
rotating element of the bearing out of physical contact with the
non-rotating members of the bearing. These preload forces and the
high lift-off/touch-down speeds result in significant bearing wear
each time the disk is started or stopped.
Many conventional, compliant foil fluid film thrust bearings have
large sway spaces and loose compliance, i.e. they do not tightly
restrict the axial or overturning motion of the bearing thrust
disk, owing to poor control of spring deflection tolerances
inherent in the spring designs.
It has been common for compliant foil fluid film thrust bearings to
utilize a plurality of coated, convex curved, compliant fluid foil
pads that are welded to a support foil to form the fluid foil
member of the bearing. These two piece fluid foil members are
typically thicker and have poorer thickness control than can single
piece fluid foil members. Two piece fluid foil members also
experience process fluid foil turbulence, increased drag at
operating speeds and reduced load capacity owing to the flow
discontinuities between the trailing edges of each foil pad and the
weld attachment edge of the next circumferentially located pad.
Some conventional, compliant foil fluid film thrust bearings
utilize spring foil elements that are formed by milling (chemically
or otherwise) circumferentially offset recesses in opposing sides
of flat foil stock so as to leave circumferentially offset unmilled
ridges on opposing sides of the foil elements. Pressure applied to
the offset ridges induces the spring foil element to deflect in a
spring-like manner. Spring foil elements formed in this manner are
prone to large variations in their spring rates due to small
variations in milling depth. This milling process non-symetrically
relieves any residual surface compressive stresses induced by
previous foil rolling operations and thus induces foil warpage.
Other bearings utilize convolute shaped spring foil elements that
are formed by pressing annealed Inconel 750X foil blanks between
two contoured plates having matching wavy contours with constant
plate to plate spacing and then heat treating the foil blanks at
approximately 1300 degrees Fahrenheit for approximately 20 hours
while they are still pressed between the contoured plates. Spring
foils formed in this manner are prone to have large variations in
undeflected thickness.
In some cases, the fluid foils may be attached to the spring foils
by welding or brazing or various spring foil elements may be welded
or brazed together to form a spring foil member. Those thrust
bearings that utilize welding or brazing to attach one foil element
to another are subject to foil distortions and foil fatigue
failures, particularly at the bond sites.
The sides of the fluid foils that face the rotating element of the
bearing can utilize low rubbing friction coatings to minimize
bearing wear when disk speed is below the lift-off/touch-down
speed. These coatings, however, may have large thickness tolerances
that can adversely affect the foil pack thickness tolerance.
The latest development in compliant foil fluid film thrust
bearings, described in U.S. Pat. No. 5,529,398 issued Jun. 25, 1996
to Robert W. Bosley entitled "Compliant Foil Hydrodynamic Fluid
Film Thrust Bearing" includes a self shimming capability to
compensate for variations in foil pack thickness and three (3)
spring or support foils beneath the fluid foil.
SUMMARY OF THE INVENTION
In the present invention, the compliant foil fluid film thrust
bearing generally comprises a single sided or two sided thrust disk
rotor, fluid foils, spring /s, a thrust plate, a foil retaining
housing and a spacer ring. The non-rotating but compliant fluid
foils are located adjacent to the thrust face or faces of the
rotatable disk. The fluid foils have open faced channels that
induce regenerative vortex flow patterns in the process fluid. The
forces applied by the thrust disk to the fluid foils vary inversely
with fluid foil to disk gap and vary proportionally with disk
deflection.
The spring foils provide a tilting pad support for the fluid foils
but allow them to follow the axial and overturning motion of the
disk. Each of the types of foils, namely fluid foils and spring
foils are attached to the foil retaining housing by a compliant web
structure and pins. The foils are formed as thin, flat, annular
sheets with integral shim rings at their periphery and contoured
cutout patterns that are unique to each type of foil.
As part of the forming process, the fluid foil blank is coated on
one side with a compliant, wear resistant material then stamped
with a forming tool to form the fluid flow channels. The thrust
plate is preloaded towards the thrust surface of the foil retaining
housing by a preload spring and is held away from the housing by
the total thickness of the foil shim rings and the thickness of the
spacer ring. This allows the bearing to essentially self shim
itself to establish a small clearance between the fluid foils and
the disk that is not affected by normal variations in foil or foil
coating thicknesses.
The bearing has no preload force and has zero starting torque when
the rotor's axis of rotation is oriented ninety degrees to the
force of gravity. Owing to the vortex flow pattern of the process
fluid, the bearing running clearances and load capacities are
improved while lift-off speeds are reduced. In addition, good
damping, low running torque and small sway space are achieved. This
is all accomplished at a low manufacturing cost with a low parts
count.
It is, therefore, a principal object of the present invention to
provide an improved compliant foil fluid film thrust bearing.
It is another object of the present invention to provide such a
bearing with enhanced axial and overturning load carrying
capacity.
It is another object of the present invention to provide such a
bearing with both squeeze film and coulomb damping.
It is another object of the present invention to provide such a
bearing with small sway space clearances to tightly restrict
bearing and thrust disk rotor deflections.
It is another object of the present invention to provide such a
bearing with very low operating torque.
It is another object of the present invention to provide such a
bearing with large running clearances between the fluid foil
elements and the thrust disk.
It is another object of the present invention to provide such a
bearing with fluid foil members that are not preloaded by spring
forces against the thrust disk at zero speed.
It is another object of the present invention to provide such a
bearing with zero starting torque when there is no gravity induced
preload forces.
It is another object of the present invention to provide such a
bearing with an extremely low lift-off/touch-down speed which is
consistent with zero preload forces.
It is another object of the present invention to provide such a
bearing with very low starting and stopping wear which is
consistent with zero preload forces and a low lift-off/touch-down
speed.
It is another object of the present invention to provide such a
bearing with converging wedge channel features (formed on the
surface of the fluid foil element) that limit fluid foil losses
from the channel at the radial outer and radial inner edges of
those channels.
It is another object of the present invention to provide such a
bearing with converging wedge channel ramps formed on the surface
of the fluid foil elements that have compound curve profiles with
concave curvatures radially, flat slopes circumferentially at zero
speed and convex curvatures at operating speed when fluid dynamic
and spring forces are applied to the fluid foil elements. The
profiles will form and function as scoops with radially wide fluid
foil inlets, radially narrowing channel widths along the
circumferential fluid foil paths, and rounded circumferentially
trailing edges.
It is another object of the present invention to provide such a
bearing with a fluid foil pattern that reduces fluid pressure
losses when the process fluid travels "down the ramp"(in a
nominally circumferential direction that is opposite to the
rotation of the thrust disk) adjacent to the fluid foil
element.
It is another object of the present invention to provide such a
bearing with a fluid flow pattern that is regenerative with a
different flow path for each regenerative flow loop.
It is another object of the present invention to provide such a
bearing with a vortex flow pattern.
It is another object of the present invention to provide such a
bearing with fluid flow element blanks and spring foil elements
that are fabricated by optically masked chemical etch
techniques.
It is another object of the present invention to provide such a
bearing with foil elements that are extremely flat owing to the
processes used to roll and heat treat the foil metal and the
processes used to form (e.g. etch) the foil blanks and
elements.
It is another object of the present invention to provide such a
bearing with foil elements that have tightly held thickness
tolerances.
It is another object of the present invention to provide such a
bearing with fluid foil members that are single fluid foil
elements, one for each side of the bearing.
It is another object of the present invention to provide such a
bearing with fluid foil elements that are formed from blanks by
pressing steeply sloped joggles to function as diverging wedge
channels which allowing the gradually converging wedge channel
ramps to result without plastic deformation as the straight line
connection between the joggles.
It is another object of the present invention to provide such a
bearing with fluid foil elements that are formed from annealed
blanks of nickel steel, such as Inconel 750X, by pressing at room
temperature.
It is another object of the present invention to provide such a
bearing with a spring foil member that has local spring rates that
vary with radial and circumferential location so as to accommodate
variations in fluid pressure within the converging wedge channel
adjacent to the local areas of the spring foil member.
It is another object of the present invention to provide such a
bearing with a tilting pad spring support system that controls the
relative support forces applied to the underside of the fluid foil
at a multiplicity of locations circumferentially along the
converging wedge channel.
It is another object of the present invention to provide such a
bearing with a tilting pad spring support system having
circumferentially closer spacing between support/pivot lines moving
up the converging ramp from the leading edge of the fluid foil to
the trailing edge of the fluid foil.
It is another object of the present invention to provide such a
bearing with a tilting pad spring support system providing
increasing support forces and support spring rates moving up the
converging ramp from the leading edge of the fluid foil to the
trailing edge of the fluid foil.
It is another object of the present invention to provide such a
bearing with a tilting pad spring support system with radially
curved support/pivot lines.
It is another object of the present invention to provide such a
bearing with a tilting pad spring support system that assures
retention of a reasonably hydrodynamically optimized scoop shape
for the fluid foil converging ramps over a wide range of bearing
operating speeds and bearing thrust loads.
It is another object of the present invention to provide such a
bearing with foil elements that are not welded or brazed to form
foil member assemblies.
It is another object of the present invention to provide such a
bearing with pins (rigidly attached to the bearing housing) which
position and resist rotation of the foil elements.
It is another object of the present invention to provide such a
bearing with self shimming capability utilizing the resilient
mounting and preload characteristics of the thrust disk, the spacer
ring and the foil's self shimming rings to prevent variations in
bearing axial play and sway space due to variations in foil
thickness and foil coating thickness.
It is another object of the present invention to provide such a
bearing with fluid foil elements, spacer ring element, thrust disk
element and thrust plate element that can be installed in the
thrust bearing quickly and easily.
BRIEF DESCRIPTION OF THE DRAWINGS
Having thus described the present invention in general terms,
reference will now be made to the accompanying drawings in
which:
FIG. 1 is a sectional view of a turbomachine having the compliant
foil fluid film thrust bearing of the present invention;
FIG. 2 is an enlarged partial view of oval 2 of FIG. 1 illustrating
the thrust plate and spacer area of the compliant foil fluid film
thrust bearing of the present invention;
FIG. 3 is a plan view of the fluid foil member of the compliant
foil fluid film thrust bearing of the present invention;
FIG. 4 is an enlarged sectional view of the fluid foil member of
FIG. 4 taken along lines 4--4;
FIG. 5 is another enlarged sectional view of the fluid foil member
of FIG. 4 taken along lines 5--5;
FIG. 6 is a plan view of the outer spring foil element of the
spring foil member of the compliant foil fluid film thrust bearing
of the present invention;
FIG. 7 is a plan view of the intermediate outer spring foil element
of the spring foil member of the compliant foil fluid film thrust
bearing of the present invention;
FIG. 8 is a plan view of the middle spring foil element of the
spring foil member of the compliant foil fluid film thrust bearing
of the present invention;
FIG. 9 is a plan view of the intermediate inner spring foil element
of the spring foil member of the compliant foil fluid film thrust
bearing of the present invention;
FIG. 10 is a plan view of the inner spring foil element of the
spring foil member of the compliant foil fluid film thrust bearing
of the present invention;
FIG. 11 is a plan view, partially cut away foil-by-foil, of the
complaint foil fluid film thrust bearing of the present
invention;
FIG. 12 is a sectional view of the unloaded fluid foil member and
spring foil member of FIG. 11 taken along line 12--12;
FIG. 13 is a sectional view of the loaded fluid foil member and
spring foil member of FIG. 11 taken along line 12--12;
FIG. 14 is a plan view of an alternate compliant foil fluid film
thrust bearing of the present invention;
FIG. 15 is a sectional view of the alternate compliant foil fluid
foil thrust bearing of FIG. 14 taken along line 15--15; and
FIG. 16 is a partial plan view of the fluid foil member of an
another alternate compliant foil fluid film thrust bearing of the
present invention;
FIG. 17 is a partial plan view of the outer spring foil element of
the spring foil member used with the fluid foil member of the
alternate compliant foil fluid film thrust bearing of FIG. 16;
FIG. 18 is a partial plan view of the intermediate outer spring
foil element of the spring foil member used with the fluid foil
member of the alternate compliant foil fluid film thrust bearing of
FIG. 16;
FIG. 19 is a partial plan view of the middle spring foil element of
the spring foil member used with the fluid foil member of the
alternate compliant foil fluid film thrust bearing of FIG. 16;
FIG. 20 is a partial plan view of the intermediate inner spring
foil element of the spring foil member used with the fluid foil
member of the alternate compliant foil fluid film thrust bearing of
FIG. 16; and
FIG. 21 is a partial plan view of the inner spring foil element of
the spring foil member used with the fluid foil member of the
alternate compliant foil fluid film thrust bearing of FIG. 16.
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS A turbomachine utilizing the compliant foil
fluid film thrust bearing of the present invention is illustrated
in FIG. 1. The turbomachine 10 generally includes turbine wheel 12
and compressor wheel 14 at opposite ends of a common shaft or tie
bar 16. The thrust and radial bearing rotor 18 is disposed around
the tie bar 16 between the turbine wheel 12 and the compressor
wheel 14. A journal bearing cartridge 20 in center bearing housing
22 rotatably supports the bearing rotor 18.
The compressor end of the bearing rotor 18 includes a radially
extending thrust disk 24 which extends into a recess 26 in the
compressor end of the center bearing housing 22. A bearing thrust
plate 28 is disposed on the opposite side of the bearing rotor
thrust disk 24. The outer periphery of the compressor end of the
center bearing housing 22 engages the compressor housing 30.
As best illustrated in FIG. 2, a thrust bearing spacer 32 is
positioned radially outward from the thrust disk 24 of the bearing
rotor 18 and is positioned radially by a plurality of
circumferentially spaced pins 34 which are fixed in holes 38 in the
recess 26 of the center bearing housing 22 and extend into holes 38
in the thrust bearing plate 28. A thrust bearing fluid foil member
40 and thrust bearing spring foil member 42 are disposed on either
side of the bearing rotor thrust disk 24 and thrust bearing spacer
32. On one side, the fluid foil member 40 and spring foil member 42
are positioned in the recess 26 of the center bearing housing 22
and on the other side they are adjacent to the bearing thrust plate
28. The fluid foil member 40 and spring foil member 42 are held in
position radially and circumferentially by the pins 34 which extend
from the center bearing housing 22, through holes in one spring
foil element 42, through holes in one fluid foil element 40,
traverse the bore of the thrust bearing spacer 32, through holes in
the opposite side fluid foil element 40, the holes in the opposite
side spring foil member 42 and into holes 38 in the bearing thrust
plate 28. The bearing thrust plate 28 is biased towards the center
bearing housing 22 by a Belleville washer 23 disposed between the
lip 25 on the bearing thrust plate 28 and the compressor housing
30.
The thickness of the thrust bearing spacer 32 is several
thousandths of an inch greater than the thickness of the bearing
rotor thrust disk 24. Variations in the foil or foil coating
thicknesses inherently cause compensating variations in the spacing
between the thrust plate 28 and the housing 22. Thus, variations in
bearing sway space and bearing compliance due to foil thickness
tolerances are prevented.
FIGS. 3-5 illustrate a fluid foil member 40 integrally formed from
a single flat disk termed a foil blank. A plurality of individual
fluid foils 41 are formed from a flat sheet of a nickel steel such
as Inconel 750X by room temperature pressing steeply sloped joggles
to function as diverging wedge channels while allowing the
gradually converging wedge channel ramps to result without plastic
deformation as the straight line connection between the joggles.
The fluid foil members would normally be annealed both during
forming and use and may be coated prior to forming the joggles with
any number of a myriad of low friction or friction reducing coating
materials which can protect the metal from abrasion during starting
and stopping, and inadvertent and occasional high speed
touch-downs. The coating would also provide for some embedment of
contamination particles.
The individual fluid foils 41 (shown as twelve) are generally
chevron shaped and connected to an outer self shimming ring 44 by
support webs 45. Fluid passages or openings 46 are formed between
adjacent support webs 45. Every fourth fluid passage 46 includes an
indexing tab 47. Each aerodynamic foil 41 has a trailing edge 48
with a rounded trailing point or nose 49 and a leading edge 50 a
generally straight ramped contour from the leading edge 50 to the
trailing edge 48. The individual fluid foils 41 have a generally
scoop shape as best illustrated in the two sectional views of FIGS.
4 and 5. One or two rows of openings 51 are provided at the leading
edge 50 of each individual fluid foil 41 to allow fluid to enter
the leading edge of the converging ramp adjacent to the thrust disk
from under the fluid foil in the area of the spring foil members
42.
As illustrated in FIGS. 6-10, the thrust bearing spring foil member
42 generally comprises an outer spring foil element 53 (FIG. 6), an
intermediate outer spring foil element 54 (FIG. 7), a middle spring
foil element 55 (FIG. 8), an intermediate inner spring foil element
56 (FIG. 9), and an inner spring foil element 57 (FIG. 10).
The outer support foil element 53, shown in FIG. 6, generally
includes an inner connector ring 60 and an outer self shimming ring
61 with a plurality (shown as twelve) of narrow width spring foils
62 extending therebetween. The narrow spring foils 62 consist of an
inner curved foil section 63 extending outward from the inner
connector ring 60 at a forward angle (in the direction of the
thrust disk's rotary motion) and an outer curved foil section 64
extending inward from the self shimming ring 61 at a forward angle.
The inner and outer foil sections 63,64 are nominally oriented
approximately forty degrees from circumferential at all points
along their length and join together to form a generally
nose-shaped foil section 65. The outer foil sections 64 are
individually connected to the outer self shimming ring 61 by a
radially extending connector or supporting web 66.
The narrow spring foil 53 is narrowest at the connection to the
inner connector ring 60 and gradually increases in width to the
point or tip of the nose 65 and continues to gradually increase in
width in the outer foil section 64 to the connector web 66. The
connector web 66 is of an even greater, generally radially
increasing, width. A plurality of indexing tabs 67 (shown as four)
extend inward from the outer self shimming ring 61 in order to
enable precise alignment of the outer support foil element 53 with
the other elements of the thrust bearing spring foil member 42 and
with the fluid foil member 40.
The intermediate outer support foil element 54, shown in FIG. 7,
generally includes an inner connector ring 73 and an outer self
shimming ring 72 with a plurality (shown as twelve) of wide spring
pads or foils 71 extending therebetween. The wide spring foils 71
consist of an inner curved foil section 75 extending outward from
the inner connector ring 73 at a forward angle and an outer curved
foil section 76 extending inward from the self shimming ring 72 at
a forward angle. The inner and outer foil sections 75, 76 join
together to form a generally nose-shaped foil section 77. Each of
the outer foil sections 76 are individually connected to the outer
self shimming ring 72 by a pair of radially extending connector or
supporting webs 74. A plurality of concentric outer dam rings 78
(shown as three) extend between the adjacent wide spring foils 71
generally where the wide spring foils 71 and the pair of webs 74
connect.
The wide spring foil 71 is narrowest at the connection to the inner
connector ring 73 and gradually increases in width to the point or
tip of the nose 77 and continues to gradually increase in width in
the outer foil section 76 to the connector webs 74. A plurality of
indexing tabs 79 (shown as four) extend inward from the outer self
shimming ring 72 in order to enable precise alignment of the outer
support foil element 54 with the other elements of the thrust
bearing spring foil member 42 and with the fluid foil member
40.
The middle spring foil element 55 is illustrated in FIG. 8 and
includes an outer self shimming ring 81 and indexing tabs 82
identical to and aligned with the corresponding elements in the
outer spring foil element 53, intermediate outer spring foil
element 54 and fluid foil member 40. A plurality of pairs (shown as
twelve) of generally nose-shaped narrow spring foils 83 extend
between the inner connector ring 84 and the outer self shimming
ring 81. Each of the pair of narrow spring foils 83 generally
straddle the narrow spring foils 62 of the outer spring foil
element 53 and are aligned at the leading and trailing edges of the
wide spring foil 71.
A connector web 87 joins each of the narrow spring foils 83 to the
outer self shimming ring 81. A plurality of concentric outer dam
rings 85 (shown as two) extend between adjacent pairs of narrow
spring foils 83 where they connect to webs 87. A plurality of
concentric inner dam rings 86 (shown as three) extend between
adjacent pairs of narrow spring foils 83 near the inner connector
ring 84.
FIG. 9 illustrates the intermediate inner spring foil element 56
which has an outer self shimming ring 89 and indexing tabs 91 which
are common to the spring foil member 42. The plurality of pairs of
intermediate width spring foil elements 92 (shown as twelve) are
disposed between the outer self shimming ring 89 and an inner
connector ring 90. Each of said pair of intermediate width spring
foil elements are connected to the outer self shimming ring by a
pair of webs 94. By intermediate width is meant a width between the
width of the narrow width outer and inner foils 62, 83 and the
width of the wide intermediate outer foil 71.
Each of the pairs of webs 94 for the intermediate width foils are
joined by a circumferential stiffening ring 93. In addition, a
single outer dam ring 96 (which could alternately be a plurality of
dam rings) and a plurality (shown as two) of concentric inner dam
rings 95 extend between adjacent pairs of intermediate width foils
92, at the connection to the webs 94 and adjacent to the inner
connector ring 90, respectively. Each of the pair of intermediate
width foils 92 generally are positioned over one of said pair of
narrow width spring foils 83 of the middle spring foil member
55.
The inner spring foil element 57 is illustrated in FIG. 10 and
includes an outer self shimming ring 100 and indexing tabs 101
identical to and aligned with the corresponding elements in the
other spring foil elements 53, 54, 55, and 56 and fluid foil member
40. A plurality of trios (shown as twelve) of generally nose-shaped
narrow spring foils 102 extend between the inner connector ring 103
and the outer self shimming ring 100. Each of the trio of narrow
spring foils 102 have widths that are generally the same as the
narrow spring foils 62 of the outer spring foil element 53 and the
pairs of narrow spring foils 83 of the middle spring foil element
55. Of the trio of narrow spring foils 102, two are aligned at the
leading and trailing edges of one of the pair of intermediate width
spring foils 92 and the third of the trio of narrow spring foils
are aligned with the trailing edge of the other of the pair of
intermediate width spring foils 92.
A connector web 105 joins each of the trio of narrow spring foils
102 to the outer self shimming ring 100. These webs 105 of each
trio of narrow spring foils 102 are joined together by a
circumferential stiffening ring 106.
The precise relationship of the fluid foil member 40 and spring
foil member 42, including the five spring foil elements 53, 54, 55,
56 & 57, is best illustrated in FIGS. 11-13. FIG. 11 is a plan
view of the assembled fluid foil member 40 and spring foil member
42 with the individual spring foil elements overlain and positioned
by their respective indexing tabs. Proceeding in a counterclockwise
rotation, the individual spring foil elements are individually cut
away in a foil-by-foil manner to show their relationship with each
other.
The outer spring foil 62 is shown in the arc identified as "A". Arc
"B" illustrates the outer intermediate foil 71 aligned over the
outer spring foil 62. A pair of middle spring foils 83 are laid
over the outer spring foil 62 and intermediate spring foil 71 in
arc "C". Arc "D" then includes the pair of intermediate inner foils
92 and finally the trio of inner foils 102 are shown over the pair
of intermediate inner foils 92 in arc "E". The fluid foils 41 are
then laid over the assembled spring foils in arc "F".
An even more precise relationship of the various foils is
illustrated in FIGS. 12 and 13. FIG. 12 illustrates an unloaded
fluid foil member and spring foil member while a loaded fluid foil
member and spring foil member are shown in FIG. 11. It should be
noted that the foil 62 is located nearer to the trailing edge of
foil 71 than to the leading edge of foil 71. Foils 83 are located
nearer the trailing edge of foils 92 than to the leading edge of
foils 92. This assures that the tilting pad spring support will
deliver more force to the underside of the fluid foil 40 near its
trailing edge 48 than its leading edge 50.
The fluid foil blank, as well as the individual elements of the
thrust bearing spring foil member 42, can be formed from flat metal
sheets by optically masked chemical etch techniques. Nickel steels,
such as Inconel 750X for the fluid foil and Inconel 718 for the
spring foil elements can be used. Typically, foil thicknesses are
between 0.004 inches and 0.007 inches. The nickel steel metal
sheets from which the foil elements are formed normally are heat
treated to full hardness in a vacuum oven (1300 degrees Fahrenheit
for about twenty hours for Inconel 750X). The five individual
elements of the thrust bearing spring foil member 42 can be
assembled by stacking the spring foil elements without bonding. The
relative micro movement of these foils in use provides coulomb
damping.
The shape of the fluid foils 41, namely an open-faced channel
having a converging width and sloping "walls", induces regenerative
vortex flow patterns in the process fluid across the fluid foil.
The process fluid generally enters the leading surface of the foil
41 from the trailing edge 48 of the preceding foil. Any make-up
process fluid is provided from the inner and outer diameter of the
leading edge or from openings 51. There is some fluid leakage flow
from the inner diameter and outer diameter, respectively, near the
trailing edge 48.
The compliant fluid foil members 40 are located adjacent to the two
thrust faces of the thrust disk 24. The spring foil members 42
provide support for the fluid foil members 40 but allow them to
follow the axial and overturning motion of the disk 24. The forces
applied by the fluid foil members to the thrust disk through the
process fluid vary inversely with foil to disk gap and vary
proportionally with disk deflection.
The thrust plate 28 is held away from the center bearing housing 22
by the total thickness of the outer self shimming rings of the
fluid foil members 40 and spring foil members 42 and the thickness
of the thrust bearing spacer 32. The thrust bearing spacer 32 is
slightly thicker than the thrust disk 24 so that there is a small
clearance between the fluid foil member 40 and the thrust disk 24
that is not affected by normal variations in foil or foil coating
thickness. The bearing has no preload force and has zero starting
torque when the disk's axis of rotation is oriented ninety degrees
to the force of gravity. With the regenerative vortex flow pattern
established by the contour of the fluid foil elements, the bearing
running clearances are significantly improved (increased) and
lift-off speeds are significantly less than previously
possible.
The converging wedge channel ramps formed in the surface of the
fluid foil members have compound curve profiles with concave
curvatures radially, flat slopes circumferentially at zero speed
and convex curvatures at operating speed when fluid dynamic and
spring forces are applied to the foil elements. The tilting pad
support for the fluid foil elements assures a near optimum convex
curvature circumferentially over a wide range of bearing thrust
loads. The profiles will form and function as scoops with radially
wide fluid flow inlets, a radially narrowing channel width along
the circumferential fluid foil paths, and rounded circumferentially
trailing edges. This multi-path regenerative vortex fluid foil
pattern reduces fluid pressure losses when the process fluid
travels "down the ramp" in a nominally circumferential direction
that is opposite to the rotation of the thrust disk adjacent to the
fluid foil member.
The particular tilting pad bearing of the present invention has
five spring foils and a fluid foil. The five spring foil elements
have four support lines for each fluid foil ramp. The relative
force exerted at each of these support lines is proportionally
controlled by the circumferential spacing between several curved
spring foil lines that generally match the curved shape of the
formed fluid foil.
The outer spring foil element 53 has twelve individual narrow width
spring foils 62 adjacent to either the thrust disk on one side of
the thrust bearing or to the thrust surface of the housing on the
other side of the thrust disk. Each of these narrow spring foils 62
provides a curved, generally nose shaped support line.
The wide intermediate outer spring foils 71 are supported by the
individual narrow spring foils 62 and can articulate both by
flexing and by tilting on the single support line of the narrow
spring foils 62 to either a nose up or nose down position as
required by the rest of the thrust bearing.
Above the wide spring foils 71 are the pair of narrow width spring
foils 83 which provide two support lines per ramp and can give
support at the nose and the leading edge of the wide spring foils
71. The two foil support lines of narrow spring foils 83 push
underneath and near the peripheral center of each of the two pairs
of intermediate width foils 92 so that these intermediate width
foils 92 can tilt nose up or nose down as required. Lastly, narrow
width spring foils 102 have three support lines, one at the
trailing edge of the leading spring foil 92, one at the leading
edge of the trailing spring foil 92 and one at the trailing edge of
the trailing spring foil 92.
Effectively, intermediate width foil 92 provide a line of support
pushing on the underside of the fluid foil relatively close to the
start of the converging ramp, and then the next three support lines
moving up the ramp are provided to the fluid foil through spring
foil 102. This makes the entire spring structure behave like the
articulated supports of tank treads, where as you go over uneven
ground the tank treads themselves can articulate because you have a
support structure that articulates. The circumferential spacing
between these various support lines, now referring to the support
lines of spring foil elements 53, 55, 56, and 57, control the
percentage of the total force coming through the spring foil
elements which is delivered to each circumferential location on the
fluid foil above the spring foil element 57.
The highest spring force will be at the nose of the formed fluid
foil where the fluid compressed pressure is highest. The support
forces and the spring rates produced are lower when moving away
from the spring foil nose. While these foil elements are primarily
tilting members to allow compliance to the fluid foil, they also
have spring properties in their own right.
The concentric dam rings of spring foil elements 54, 55, and 56
effectively serve as dams to limit leakage out of the thrust
bearing particularly when the bearing is operated hydrostatically.
The thrust bearing of the present invention is particularly useful
in a hydrostatically augmented thrust bearing such as described in
U.S. patent application Ser. No. 08/622,250 filed Jun. 14, 1996 by
Robert W. Bosley and Ronald F. Miller entitled "Hydrostatic
Augmentation of a Compliant Foil Hydrodynamic Fluid Film Thrust
Bearing", incorporated herein by reference. The openings 51 at the
leading edge of the fluid foil 41 are specifically provided for
this hydrostatic augmentation. The thrust bearing will, however,
function as a hydrodynamic thrust bearing with or without openings
51.
The tilting pad thrust bearing operates with its fluid foil flexed
circumferentially in a convex fluid dynamically optimized shape on
the surface adjacent to the thrust disk without relying upon air
pressure in the spring area. Air pressure will, however, provide
additional convex shaping and load capacity and provide good
adaptability.
While the nose shape of the individual spring foils has been shown
to be relatively identical for the five spring foils and the fluid
foil, the shape of the spring foil nose can be varied to control
the spring rate. As illustrated in FIGS. 14 and 15, the nose of the
trailing edge of middle spring foil 83' can be sharper, that is
have a smaller radius than the noses of the trailing edge of inner
spring foil 102 and intermediate inner spring foil 92. This will
stiffen up the spring rate at the end of the converging ramp so
that there will be less fluid flow leakage and provide greater
support for the fluid foil nose.
The generally scoop-shaped converging wedge channels formed on the
surface of the fluid foil members induce vortex fluid foil patterns
and limit process fluid foil losses from the channels at the radial
inner and outer edges of the foils. This, together with the self
shimming construction and other features of the present invention,
provides a thrust bearing having a high load carrying capacity,
good damping, small sway clearances, low running torque, high
running foil to disk clearances, zero preload force, low starting
torque, low lift-off/touch-down speeds, and low wear. In addition,
all of this is achieved with a low parts count, low manufacturing
cost, and ease of assembly.
Further, the fluid foil members and spring foil elements can have a
straight radial shape as shown in FIGS. 16-21. Except for having a
straight radial shape rather than the nose shape previously
described, the fluid foil member 40' having straight radial foils
141 and spring or support foil members 53', 54', 55', 56', and 57'
would function generally the same and have the same relative
spacing and relative positioning with respect to each other. The
outer support foil element 53' of FIG. 17 includes narrow width
radial spring foils 162, intermediate outer support foil element
54' of FIG. 18 includes wide radial pads or foils 171, middle
support foil element 55' of FIG. 19 includes pairs of narrow width
radial spring foils 183, intermediate inner support foil element
56' of FIG. 20 includes pairs of wide radial spring pads or foils
192, while inner support foil element 57' of FIG. 21 includes trios
of narrow width radial spring foils 202. The generally flat
(radially) fluid foil surfaces, and underlying spring foils which
maintain generally flat (radially) fluid foil surfaces of FIGS.
16-21, are not intended to establish a scoop shaped converging ramp
and therefor do not generate vortex regenerative process fluid
flows.
While specific embodiments of the invention have been illustrated
and described, it is to be understood that these are provided by
way of example only and that the invention is not to be construed
as being limited thereto but only by the proper scope of the
following claims.
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