U.S. patent application number 13/283766 was filed with the patent office on 2013-05-02 for high temperature seal system.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is Bala CORATTIYIL, Eric RUGGIERO, Thomas Lowell STEEN. Invention is credited to Bala CORATTIYIL, Eric RUGGIERO, Thomas Lowell STEEN.
Application Number | 20130106061 13/283766 |
Document ID | / |
Family ID | 46800367 |
Filed Date | 2013-05-02 |
United States Patent
Application |
20130106061 |
Kind Code |
A1 |
RUGGIERO; Eric ; et
al. |
May 2, 2013 |
HIGH TEMPERATURE SEAL SYSTEM
Abstract
A hydrodynamic sealing system for use in an oxidizing
environment includes a rotor and a sealing stator. The stator
includes a solid lubricant or a surface treatment and the rotor is
hardened or the stator is hardened and the rotor includes the solid
lubricant or the surface treatment. The stator is located proximate
to the rotor to provide a seal. The stator and the rotor are robust
at extreme temperatures above 700 degrees Fahrenheit (F) such that
at least one of the stator and the rotor have a wear rate and a
surface roughness sufficient to maintain an operating gap between
the stator and rotor.
Inventors: |
RUGGIERO; Eric; (Rensselaer,
NY) ; CORATTIYIL; Bala; (Cincinnati, OH) ;
STEEN; Thomas Lowell; (Niskayuna, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RUGGIERO; Eric
CORATTIYIL; Bala
STEEN; Thomas Lowell |
Rensselaer
Cincinnati
Niskayuna |
NY
OH
NY |
US
US
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
46800367 |
Appl. No.: |
13/283766 |
Filed: |
October 28, 2011 |
Current U.S.
Class: |
277/411 |
Current CPC
Class: |
F05D 2300/132 20130101;
F05D 2300/2291 20130101; F05D 2230/41 20130101; Y02T 50/60
20130101; Y02T 50/671 20130101; F01D 11/02 20130101; F05D 2300/2282
20130101 |
Class at
Publication: |
277/411 |
International
Class: |
F01D 11/02 20060101
F01D011/02 |
Goverment Interests
GOVERNMENT RIGHTS STATEMENT
[0001] This invention was made with U.S. Government support under
FA8650-09-D-2922 0002 awarded by (AFRL-WPAFB). The U.S. Government
has certain rights in the invention.
Claims
1. A sealing system for use in an oxidizing environment, said
system comprising: a rotor and a sealing stator; one of said stator
comprising a solid lubricant or a surface treatment with said rotor
being hardened and said rotor comprising said solid lubricant or
said surface treatment with said stator being hardened; and said
stator located proximate said rotor to provide a seal, said rotor
and said stator being robust at temperatures above 700 degrees
Fahrenheit such that at least one of said stator and said rotor
have a wear rate and a surface roughness sufficient to maintain an
operating gap between said stator and said rotor.
2. The sealing system wherein the operating gap is about 0.0002
inches.
3. The system of claim 1 wherein said rotor consists of CrC--NiCr
Coated Inconel 718.
4. The system of claim 1 wherein said stator comprises Boronized
Inconel 718.
5. The system of claim 1 wherein said stator comprises hot pressed
Hexagonal boron nitride.
6. The system of claim 1 wherein said stator comprises NASA PS304
Coated Inconel 718.
7. The system of claim 1 wherein said rotor and said stator
comprise a high temperature hydrodynamic lift seal.
8. The system of claim 1 wherein said rotor and said stator
comprise a sump seal for an aircraft engine.
9. The system of claim 1 wherein a roughness of said stator is less
than 12 micro inches Ra when subjected to a load of about 3.5 psi
for about an hour at a temperature of up to about 1200 degrees
Fahrenheit.
10. The system of claim 1 wherein said stator comprises a surface
roughness of less than about 2.0 micro inches Ra.
11. The system of claim 1 wherein said stator is robust at
temperatures up to about 1200 degrees Fahrenheit.
12. The system of claim 1 wherein said stator is robust at
temperatures up to about 1000 degrees Fahrenheit.
13. The system of claim 1 wherein said stator is robust at
temperatures exceeds 1200 degrees Fahrenheit.
14. The system of claim 1 wherein said rotor comprises a hard
coating having a hardness of at least HRC 70.
15. A sealing system for use in an oxidizing environment, said
system comprising: a sliding portion a sealing portion; one of said
sealing portion comprising a solid lubricant or a surface treatment
with said sliding portion being hardened, and said sliding portion
comprising said solid lubricant or said surface treatment with said
sealing portion being hardened; and said sealing portion located
proximate said sliding portion to provide a seal, said sealing
portion and said sliding portion being robust at temperatures above
700 degrees Fahrenheit such that at least one of said sealing
portion and said sliding portion have a wear rate and surface
roughness sufficient to maintain an operating gap between said
sealing portion and said sliding portion.
16. The sealing system wherein said operating gap is about 0.0002
inches.
17. The system of claim 15 wherein said sliding portion consists of
CrC--NiCr Coated Inconel 718.
18. The system of claim 15 wherein said sealing portion comprises
Boronized Inconel 718.
19. The system of claim 15 wherein said sealing portion comprises
hot pressed Hexagonal boron nitride.
20. The system of claim 15 wherein said sealing portion comprises
NASA PS304 Coated Inconel 718.
21. The system of claim 15 wherein said sliding portion and said
sealing portion comprise a high temperature hydrodynamic lift
seal.
22. The system of claim 15 wherein said sliding portion and said
sealing portion comprise a sump seal for an aircraft engine.
23. The system of claim 15 wherein a roughness of said sealing
portion is less than 12 micro inches Ra when subjected to a load of
about 3.5 psi for about an hour at a temperature of up to about
1200 degrees Fahrenheit.
24. The system of claim 15 wherein said sealing portion comprises a
surface roughness of less than about 2.0 micro inches Ra.
25. The system of claim 15 wherein said sealing portion is robust
at temperatures up to about 1200 degrees Fahrenheit.
26. The system of claim 15 wherein said sealing portion is robust
at temperatures up to about 1000 degrees Fahrenheit.
27. The system of claim 15 wherein said sealing portion is robust
at temperatures exceeds 1200 degrees Fahrenheit.
28. The system of claim 15 wherein said sliding portion comprises a
hard coating having a hardness of at least HRC 70.
29. The system of claim 15 wherein said sliding portion and sealing
portion remain in contact with one another throughout operation.
Description
BACKGROUND
[0002] This disclosure relates, in general, to materials and
applications for use in extreme temperature environments.
[0003] There are a number of high temperature environments where
elements that employ carbon based elements are unable to sustain
operation. Typical carbon based elements suffer some serious
degradation about and above 700 degrees Fahrenheit (F).
[0004] More specifically, sliding components such as linear or
reciprocating applications including piston and rotor devices with
components that are required are increasingly being required to
operate in extreme environments.
[0005] In one example, hydrodynamic face seals and hydrodynamic
circumferential seals are sealing technologies that minimize
lubrication oil leakage. Hydrodynamic seals offer an attractive
solution since they operate primarily in a non-contacting manner,
thus increasing seal life and reliability in a compact axial space
while maintaining tight seal clearances. Both hydrodynamic face
seals as well as hydrodynamic circumferential seals rely on the
development of a pressure profile between a rotating and static
sealing surface to generate an operating gap as small as possible.
A good surface finish must be maintained on the rotating and static
sealing surfaces in order to preserve the required pressure
profile. Although the hydrodynamic seals are non-contacting during
the bulk of operation, they are subject to sliding contact during
spin-up and shutdown of the rotor. To minimize wear and heat
checking throughout contact operation, and consequently maintain a
highly effective hydrodynamic seal, the seal components are
generally made out of materials that exhibit excellent friction and
wear characteristics.
[0006] Traditional hydrodynamic seals, typically made from carbon,
are not suitable for operation at temperatures such as those
exceeding 700 degrees Fahrenheit (F) due to the onset of severe,
degrading oxidation at such temperatures. One example of such
severe, degrading oxidizing conditions occurs in a gas turbine sump
of a high mach turbo aircraft engine. Once the seals deteriorate
the entire sump can fail.
[0007] In another application, an engine with pistons operating in
a linear fashion employ rings and seals that have the same problems
as noted herein.
[0008] Thus, there is a need for systems and methods for operations
which allow for increased temperature operation while maintaining
integrity and performance.
SUMMARY
[0009] The present system provides, in one aspect, a sealing system
for use in an oxidizing environment which includes a rotor and a
sealing stator. The stator includes a solid lubricant or a surface
treatment and the rotor is hardened or the stator is hardened and
the rotor includes the solid lubricant or the surface treatment.
The stator is located proximate to the rotor to provide a seal. The
stator and the rotor are robust at extreme temperatures above 700
degrees Fahrenheit (F) such that at least one of the stator and the
rotor have a wear rate and a surface roughness sufficient to
maintain an operating gap between the stator and rotor.
[0010] The present system provides, in one aspect, a sliding system
for use in an oxidizing environment which includes a sliding
portion and a sealing portion. The sealing portion includes a solid
lubricant or a surface treatment and the sliding portion is
hardened or the sliding portion includes the solid lubricant or the
surface treatment and the sealing portion is hardened. The sealing
portion is located proximate to the sliding portion to provide a
seal. The sealing portion and the sliding portion are robust at
temperatures above 700 degrees Fahrenheit (F) such that at least
one of the sealing portion and the sliding portion have a wear rate
and a surface roughness sufficient to maintain an operating gap
between the sealing portion and the sliding portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] These and other features, aspects, and advantages of the
present system will become better understood when the following
detailed description is read with reference to the accompanying
drawings in which like characters represent like parts throughout
the drawings, wherein:
[0012] FIG. 1 is a side cross-sectional view of a hydrodynamic
sealing system in accordance with an embodiment of the present
system;
[0013] FIG. 2 is an enlarged view of a portion of the system of
FIG. 1;
[0014] FIG. 3 is a schematic of the operation of a hydrodynamic
face seal in accordance with an embodiment;
[0015] FIG. 4 depicts a disc-on-ring test apparatus;
[0016] FIG. 5 is a table listing materials utilized in stators and
rotors for testing according to the apparatus of FIG. 4;
[0017] FIG. 6 is a plot of pre-test and post-test surface roughness
for the rotor and stators of FIG. 5;
[0018] FIG. 7 is a plot of pre-test and post-test weight change for
the rotors and stators of FIG. 5;
[0019] FIG. 8 is a plot of average torque during tests for the
materials in FIG. 5;
[0020] FIG. 9 lists tabular data for the tests according to the
apparatus of FIG. 4 and materials of FIG. 5;
[0021] FIG. 10 is a table of stators and rotors tested under Phase
II testing;
[0022] FIG. 11 is a plot of pre-test and post-test surface
roughness for the rotors and stators of FIG. 10;
[0023] FIG. 12 is a plot of pre-test and post-test weight change
for the rotors and stators of FIG. 10;
[0024] FIG. 13 is a plot of average torque during the tests of the
stators and rotors of FIG. 10;
[0025] FIG. 14 is a table of results of the tests of the stators
and rotors of FIG. 10;
[0026] FIG. 15 is a top view of a piston and cylinder in accordance
with an embodiment of the present system; and
[0027] FIG. 16 is a side cross-sectional view of the system of FIG.
15.
DETAILED DESCRIPTION
[0028] In accordance with the principles of the present systems and
methods for operating in extreme conditions are provided. One
example is a coating or parent material that permits operation in
the extreme environments, particularly for sliding elements.
[0029] In one example the sealing system provides a tight seal and
maintains a small gap with low wear and surface roughness in a high
temperature environment.
[0030] In an exemplary embodiment depicted in FIG. 1, a
hydrodynamic sealing system 10 includes a rotor 20 coated with a
hard coating and a seal 30 composed of a solid lubricant (e.g.,
Boronized Inconel 718) that is robust at temperatures exceeding 700
degrees Fahrenheit. In one example the temperature range goes up to
about 1200 degrees Fahrenheit (F)). "Robust" is defined herein as
having a wear rate and surface roughness sufficient to maintain an
operating gap between the stator and rotor of about 0.0002
inches.
[0031] Hydrodynamic face seals, usually referred to as Dry Gas
Seals in industries such as the Oil and Gas industry, consist of a
rotating ring, known as a seat or rotor (e.g. rotor 20), and a
stationary ring, known as the face or stator (e.g., seal 30). In
one example the surface finish of each face seal is on the order of
0.1 .mu.m. In a further example the geometry of the rotor includes
radial grooves 200 that extend from the center of the seal face to
the outer diameter as depicted in FIG. 3. The purpose of these
grooves is to cut into the operating fluid (typically a gaseous
hydrocarbon or dry nitrogen) while rotating and consequently build
up hydrodynamic pressure toward a radially inner portion 210 of the
grooves to separate the two seal faces. When in operation,
hydrodynamic seal portions may be separated (e.g., by an operating
gap), and when separated, the seat (e.g. rotor 20) rides on a
cushion of gas over the face (e.g., seal 30) as depicted in FIG. 3.
As indicated above, the seal portions may contact each other during
start-up and shut down of a particular rotor. According to one
example, the grooves of the seat are about 6 .mu.m deep and the
face-seat gap is about 3 .mu.m.
[0032] System 10 is an advanced hydrodynamic seal that is robust in
an oxidizing environment at extreme temperatures, for example
greater than 700 degrees Fahrenheit (F) and in one example up to
about 1200 degrees Fahrenheit (F). Such a sealing system could be
used in sumps (e.g., a sump 40) of a High Mach Turbo Aircraft
Engine as depicted in FIGS. 1-2, for example. Sump 40 may include a
bearing 50, a seal oil slinger 60, seal windback threads 70, and a
seal housing 80. A stationary seal 90 and a rotating labyrinth seal
100 are also depicted. An operating gap 110 is present between seal
30 and rotor 20. Seal 30 may include a surface treatment, such as
Boronized Inconel 718 that is robust over 1000 degrees Fahrenheit
(F) and at temperatures up to at least 1200 degrees Fahrenheit (F).
The suitable operation of a hydrodynamic seal requires a sealing
surface that maintains a low surface roughness throughout
operation. The combination of a hard rotor coating (e.g., having a
hardness Rockwell value of HRC 70 or more) and a seal component
which includes an appropriate surface treatment (e.g., Boronized
Inconel 718) results in a low coefficient of friction, a low wear
rate, and the ability to retain an acceptable surface finish
throughout operation. In another example, the rotor could include a
surface treated material as described while the seal component
could have a hard coating or may be otherwise hardened such that it
has a hardness Rockwell value of HRC 70 or more.
[0033] As described herein, traditional hydrodynamic seals,
typically made from carbon, are not suitable for operation at
temperatures over 700 degrees Fahrenheit (F) due to the onset of
severe, degrading oxidation, which leads to catastrophic failure of
the seal a. Manufacturing the hydrodynamic seal out of a solid
lubricant that is robust at high temperatures rather than carbon
allows the operating temperature to reach at least 1200 degrees
Fahrenheit (F).
[0034] In one example, forward, mid, and aft sumps of a High Mach
Turbo Aircraft Engines reach extreme temperatures of 1000 degrees
Fahrenheit (F) to about 1200 degrees Fahrenheit (F) when
approaching the transition stage to a ramjet at Mach 3. Such
extreme temperatures are well beyond the current design experience
of hydrodynamic seal manufacturers. As described, current seals
fabricated from carbon are subject to accelerated oxidation at
temperatures exceeding 700 degrees F.
[0035] Various substrates and coatings for sump seals (e.g., sumps
for High Mach Turbo Aircraft Engines) were investigated for
operating at 1200.degree. degrees Fahrenheit (F). Parameters for
hydrodynamic seals to be used in this environment include, for
example: wear resistance at 1200 degrees Fahrenheit (F), low
coefficient of friction and low heat generation at sliding
interface. As described herein, severe, degrading oxidation
typically occurs at temperatures exceeding 700 degrees Fahrenheit
(F) in traditional carbon seals. It is desirable that materials
used in such seals survive at ranges of at least 700 degrees
Fahrenheit (F), 1000 degrees Fahrenheit (F) and 1200 degrees
Fahrenheit (F) to provide low leakage and are insensitive to an oil
environment. The simulated testing predicted steady-state leakage
(performance) based on operating regime, predicted thermal
distortion and impact on performance, and characterized the effect
of surface roughness on performance.
[0036] High temperature material testing was performed on a sliding
wear test rig as depicted in FIG. 4 including a rotor disk 130 and
a stator ring 140 having a gap 150 therebetween. The sliding wear
test rig was designed for ring-on-disc testing, where the rotor is
rotating and the stator (seal) is stationary. This testing mimics
the actual conditions (e.g., the temperature and speed) which
occurs in a high temperature (e.g., up to 1200 degrees F.)
environment, such as a sump seal in a High Mach Turbo Aircraft
Engine, during the start up and shut down of the engine, i.e.,
before or after the hydrodynamic lift occurs.
[0037] The seal in one example (the static stator of test setup)
consisted of the materials listed in FIG. 5. To mimic the material
combination found in traditional hydrodynamic and carbon seals, a
WC--Co coated Inconel 718 disc was tested against M-45
electrographite. To achieve the 1200 degree Fahrenheit (F)
operating temperature, a CrC--NiCr rotor coating (oxidation
resistant up to 1650 degrees Fahrenheit (F)) replaced the presently
used WC--Co coating (oxidation resistant up to 1000 degrees
Fahrenheit (F)). FIG. 5 summarizes the materials tested in Task 3
and Task 4.
[0038] The testing was separated into two phases (Phase 1 and Phase
2). The first phase of testing was used to identify potential seal
material candidates. Phase 2 testing was performed at multiple
isotherms throughout the operating range of the component. Phase 1
testing was run at a linear speed of 275 ft/s (at the outer
diameter of the test sample). The temperature at the sliding
interface was 1000 degrees Fahrenheit (F). Throughout the test, the
contact pressure was held at 3.5 psi, which is the typical contact
pressure as specified by traditional seal vendors. The second phase
of testing was also conducted at 275 ft/s at isotherms of 72
degrees Fahrenheit (F), 400 degrees Fahrenheit (F), 600 degrees
Fahrenheit (F), 800 degrees Fahrenheit (F), 1000 degrees Fahrenheit
(F), and 1200 degrees Fahrenheit (F).
[0039] The characteristics evaluated in identifying successful
material candidates were: 1) low coefficient of friction; 2) good
wear resistance (quantified by surface roughness degradation and
type of wear debris); and 3) low heat generation at the sliding
interface. These characteristics would combine to produce an
appropriate operating gap (e.g., 0.0002 in.) between a rotor and
stator at the indicated temperatures for the lifetime of the seal.
Accordingly, the specific test metrics to compare material
performance were: 1) coefficient of friction data; 2) profilometry,
to evaluate surface finish degradation as caused by wear and
oxidation; 3) temperature levels at the sliding interface; and 4)
mass loss (to evaluate wear).
[0040] Several materials were tested under Phase 1 conditions,
i.e., a chamber temperature at 1000 degrees Fahrenheit (F), a
maximum surface speed at 275 ft/s, a load at the wearing surface at
3.5 psi, and a test duration of 1 hour. FIG. 6 is a plot of the
pre-test and post-test surface roughness (in micro inches R.sub.a)
for Test 1-Test 10 for the rotor and stators. FIG. 7 is a plot of
the pre-test and post-test weight change for the rotor and stators,
and FIG. 8 is a plot of the average torque during each of the
tests. FIG. 9 lists the tabular data from the tests.
[0041] Test 1 is the baseline test of the M-45 Electrographite
stator versus a WC--Co rotor (current state of the art material
combination). While the performance of this material combination
was superior during the 1-hour wear test, the electrographite
stator material oxidizes rapidly and is not suitable for long-term
operation at the desired temperature.
[0042] The Test 2 material combination was not able to survive the
operating conditions. The selected SiC material provides excellent
wear characteristics; however, it did not provide a low coefficient
of friction and the temperature of the stator increased rapidly.
After 2 minutes, the thermal shock caused the brittle SiC stator to
shatter into multiple pieces.
[0043] The Test 3 material combination of ESK Ekastic T Silicon
Nitride and the CrCNiCr coated rotor provided the best test results
from the non-baseline material combinations. The torque (friction)
level for Test 3 is very similar to the Test 1 levels and the
weight loss value for Test 3 is better than the Test 1 value. Phase
1 results from this material combination are very promising and it
was selected to be tested under the Phase 2 operating
conditions.
[0044] The stator materials for Test 4 and Test 5 were partially
composed of hexagonal boron nitride. This material has a low
coefficient of friction (e.g., less than 0.2 above 1000 degrees
Fahrenheit (F) while graphite's coefficient of friction increases
dramatically (e.g., over 0.8) above this temperature. Despite the
promising high temperature friction data for these materials, the
Test 4 and Test 5 material combinations did not perform well under
the Phase 1 test conditions. These materials were not selected for
Phase 2 testing.
[0045] The Test 6 material combination of the Tribaloy T-800
coating and the CrC--NiCr coated rotor provided marginally
successful results regarding surface roughness and weight loss. The
torque (friction) level for Test 6 was higher than the remainder of
the Task 4 coatings tested and was not selected for Phase 2
testing.
[0046] The Test 7 material combination of Boronized Inconel and the
CrC--NiCr coated rotor provided marginally successful results
regarding surface roughness considering the stator roughness
increased more than desired. Despite this, the torque (friction)
level for Test 7 was lower than the baseline torque from Test 1
(carbon graphite). This low torque level from this material
combination is very promising and it was selected for Phase 2
testing.
[0047] The Test 8 material combination of an Alcrona coated stator
and the CrC--NiCr coated rotor provided marginally successful
results regarding surface roughness, weight loss, and torque. This
material combination was not selected for Phase 2 testing.
[0048] The Test 9 material combination of NASA PS304 coated stator
and the CrC--NiCr coated rotor provided excellent results regarding
surface roughness and marginal results for weight loss. The torque
(friction) level for Test 9 was lower than the baseline torque from
Test 1 (carbon graphite). This low torque level and low roughness
change for this material combination was selected for Phase 2
testing.
[0049] The Test 10 material combination of TiAl Alloy coated stator
and the CrC--NiCr coated rotor provided marginally successful
results regarding surface roughness, weight loss, and torque. This
material combination was not selected for Phase 2 testing.
[0050] The material combinations presented in FIG. 10 were tested
under Phase 2 Conditions, i.e., with a chamber temperature varied
up to 1200 degrees Fahrenheit (F), a maximum surface speed at 275
ft/s, a load at the wearing surface at 3.5 psi, and a test duration
of 1 hour. FIG. 11 is a plot of the pre-test and post-test surface
roughness for the rotor and stators, FIG. 12 is a plot of the
pre-test and post test weight change for the rotor and stators, and
FIG. 13 is a plot of the average torque during each of the tests.
FIG. 14 presents the tabular data relative to tests 11, 12, 13 and
11a.
[0051] The Test 11 material combination of Boronized Inconel stator
and the CrC--NiCr coated rotor was able to survive the full test
matrix for Phase 2. The surface roughness and weight change
experienced by the specimens are similar to what was measured
during Phase 1. The average torque measured at the 1000 degrees
Fahrenheit (F) isotherm was 0.57 in-lb which is much higher than
the average torque measured at this same isotherm in Phase 1
testing (0.13 in-lb). This offset may have been due to variations
in the testing rig after a re-build thereof.
[0052] The material combinations tested in Test 12 and Test 13 did
not survive the test past the 72 degrees Fahrenheit (F) isotherm.
Both tests were stopped due to an excessive run out in the test rig
shaft. To ensure these failures were due to material performance
and not due to the re-build of the test rig the Test 11 material
combination was re-tested as Test 11A. The data collected from 11A
compared very well to data from Test 11. This agreement confirms
that the test rig did not contribute to the Test 12 and Test 13
failures.
[0053] Based the Phase 2 test results, Boronized Inconel 718 and
CrC--NiCr coated Inconel 718 are appropriate for the stator or seal
(e.g., seal 30) and rotor (e.g., rotor 20), respectively. In
particular, the average torque was lower than the other materials
in test 11A, while the increase in roughness for Boronized Inconel
718 was the least of the other stators listed in FIG. 14. Thus,
these materials used as discussed provided high temperature
compatibility, good wear characteristics (gradual, as opposed to
catastrophic), and the ability to maintain a good surface finish.
Other appropriate materials for the stator include hexagonal boron
nitride, and NASA PS304 coated Inconel 718. The quality of the NASA
PS304 coating in the phase 2 testing was marginal due to the small
geometry of the test stators which is believed to have contributed
to the marginal result for weight loss in the phase 2 testing. The
data from phase 1 shows this material to be appropriate for use as
a stator (e.g., seal 30). Based on the available high temperature
coefficient of friction data, hexagonal boron nitride appears to
also to be a suitable replacement for carbon graphite for seals
(e.g., seal 30) in high temperature applications. For example, a
seal or stator could be completely made of a binder embedded with a
solid lubricant, such as hexagonal boron nitride. The materials
included in a stator of a hydrodynamic seal should allow the
maintenance of an appropriate operating gap (e.g., up to 0.0002
in.) at an operating temperature of up to 1200 degrees Fahrenheit
(F) (e.g., of a high temperature aircraft engine as described
above). Further, the material choices for the rotors and stators
could be reversed in each particular situation such that the stator
material is used on the rotor and the material from the rotor could
be used on the stator.
[0054] In another example depicted in FIGS. 15 and 16, a sliding
element 100 (e.g., a piston of an engine) may be moveable relative
to a sealing portion 110 (e.g., an inner cylinder wall of an
engine) which are separated by a gap 120. As described above
relative to system 10, these elements may be utilized in extreme
temperature environments such that the sliding and/or sealing
element may be formed of the materials described above and may have
a wear rate and surface roughness sufficient to maintain an
operating gap between the sliding element and sealing element of
about 0.0002 inches. For example, the sliding element may be formed
of, or may be coated with, CrC--NiCr while the sealing element may
include Boronized Inconel 718, hexagonal boron nitride or NASA
PS304 coated Inconel 718, for example. Alternatively, these
material choices of the sealing element versus the sliding element
may be reversed.
[0055] It will be understood by one of ordinary skill in the art
that the materials described as being appropriate for sliding
interfaces (such as linear or rotary) which are to be subjected to
extreme environments, such as temperatures above 700 degrees
Fahrenheit (F), about 1000 degrees Fahrenheit (F), about 1200
degrees Fahrenheit (F) and above 1200 degrees Fahrenheit (F), while
having low leakage, and insensitivity to an oil environment, low
wear resistance, low coefficient of friction and low heat
generation at a sliding interface.
[0056] It is to be understood that the above description is
intended to be illustrative, and not restrictive. For example, the
above-described embodiments (and/or aspects thereof) may be used in
combination with each other. In addition, many modifications may be
made to adapt a particular situation or material to the teachings
of the various embodiments without departing from their scope.
While the dimensions and types of materials described herein are
intended to define the parameters of the various embodiments, they
are by no means limiting and are merely exemplary. Many other
embodiments will be apparent to those of skill in the art upon
reviewing the above description. The scope of the various
embodiments should, therefore, be determined with reference to the
appended claims, along with the full scope of equivalents to which
such claims are entitled. In the appended claims, the terms
"including" and "in which" are used as the plain-English
equivalents of the respective terms "comprising" and "wherein."
Moreover, in the following claims, the terms "first," "second," and
"third," etc. are used merely as labels, and are not intended to
impose numerical requirements on their objects. Further, the
limitations of the following claims are not written in
means-plus-function format and are not intended to be interpreted
based on 35 U.S.C. .sctn.112, sixth paragraph, unless and until
such claim limitations expressly use the phrase "means for"
followed by a statement of function void of further structure. It
is to be understood that not necessarily all such objects or
advantages described above may be achieved in accordance with any
particular embodiment. Thus, for example, those skilled in the art
will recognize that the systems and techniques described herein may
be embodied or carried out in a manner that achieves or optimizes
one advantage or group of advantages as taught herein without
necessarily achieving other objects or advantages as may be taught
or suggested herein.
[0057] While the invention has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the invention is not limited to such
disclosed embodiments. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the invention may
include only some of the described embodiments. Accordingly, the
invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended
claims.
[0058] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
* * * * *