U.S. patent number 10,385,729 [Application Number 14/950,252] was granted by the patent office on 2019-08-20 for cylindrical air guide in a turbine engine.
This patent grant is currently assigned to General Electric Company. The grantee listed for this patent is General Electric Company. Invention is credited to Christopher Mark Bordne, Jeremy Stephen Wigon.
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United States Patent |
10,385,729 |
Bordne , et al. |
August 20, 2019 |
Cylindrical air guide in a turbine engine
Abstract
An air/oil separator for a gas turbine engine includes a drive
shaft having a central axis extending in an axial direction, a free
vortex chamber mounted radially around the drive shaft, a
separation chamber coupled with the free vortex chamber in the
axial direction opposite to the drive shaft, and a rotatable outlet
shaft radially rotatable and having an inlet end coupled with the
separation chamber opposite to the free vortex chamber, an outlet
end, and a hollow interior chamber therebetween. The hollow
interior chamber has an inner circumference extending in the axial
direction a cylindrical air guide extending coaxially therein. The
cylindrical air guide has a nonporous cylindrical main body, an
upstream end fixedly coupled with the inlet end of the rotatable
outlet shaft, and a downstream end coaxially disposed within the
outlet end of the rotatable outlet shaft.
Inventors: |
Bordne; Christopher Mark
(Redlands, CA), Wigon; Jeremy Stephen (Topsfield, MA) |
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Assignee: |
General Electric Company
(Schenectady, NY)
|
Family
ID: |
58720616 |
Appl.
No.: |
14/950,252 |
Filed: |
November 24, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20170145856 A1 |
May 25, 2017 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02C
7/32 (20130101); F01D 25/18 (20130101); F05D
2260/609 (20130101) |
Current International
Class: |
F01D
25/18 (20060101); F02C 7/32 (20060101) |
Field of
Search: |
;55/409,413,416 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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369456 |
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Dec 1991 |
|
EP |
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1993911550 |
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Feb 1993 |
|
EP |
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2010022591 |
|
Mar 2010 |
|
WO |
|
Primary Examiner: Lee, Jr.; Woody A
Assistant Examiner: Htay; Aye S
Attorney, Agent or Firm: General Electric Reed; James
Claims
What is claimed is:
1. An air/oil separator for a gas turbine engine, said air/oil
separator comprising: a drive shaft having a central axis extending
in an axial direction; a free vortex chamber mounted radially
around said drive shaft; a separation chamber coupled with said
free vortex chamber in the axial direction on a side of said free
vortex chamber opposite to said drive shaft; a rotatable outlet
shaft having an inlet end, an outlet end, and a hollow interior
chamber therebetween, said hollow interior chamber having an inner
circumference extending in the axial direction, said inlet end
coupled with said separation chamber on a side of said separation
chamber opposite to said free vortex chamber, and said rotatable
outlet shaft radially rotatable about the central axis; and a
cylindrical air guide comprising; a nonporous cylindrical main body
having a smooth, uninterrupted outer surface and an outer
circumference extending coaxially within the inner circumference of
said hollow interior chamber of said rotatable outlet shaft, said
inner circumference having a diameter greater than a diameter of
the cylindrical air guide; an upstream end fixedly coupled with
said inlet end of said rotatable outlet shaft; and a downstream end
coaxially disposed within said outlet end of said rotatable outlet
shaft.
2. The air/oil separator of claim 1, wherein said rotatable outlet
shaft further comprises a plurality of air discharge slots disposed
radially about said hollow interior chamber at said inlet end.
3. The air/oil separator of claim 2, wherein said plurality of air
discharge slots are configured to allow air communication between
said separation chamber and said hollow interior chamber of said
rotatable outlet shaft.
4. The air/oil separator of claim 3, further comprising an upstream
mount, wherein said upstream end of said cylindrical air guide is
fixedly coupled with said inlet end of said rotatable outlet shaft
by said upstream mount, and wherein said upstream mount is mounted
upstream of said plurality of air discharge slots.
5. The air/oil separator of claim 4, wherein said upstream mount is
configured to prevent air flowing upstream of said plurality of air
discharge slots within said hollow interior chamber.
6. The air/oil separator of claim 4, wherein said upstream mount is
disc-shaped.
7. The air/oil separator of claim 4, wherein said upstream mount is
ring-shaped.
8. The air/oil separator of claim 7, wherein said ring-shaped
upstream mount has an inner circumference and an outer
circumference, said inner circumference of said ring-shaped
upstream mount configured to seal said ring-shaped upstream mount
to said outer circumference of said upstream end of said
cylindrical air guide, and said outer circumference of said
ring-shaped upstream mount configured to seal said ring-shaped
upstream mount to said inner circumference of said hollow interior
chamber of said rotatable outlet shaft.
9. The air/oil separator of claim 3, wherein said drive shaft
further comprises a hollow interior shaft opening located upstream
of said plurality of air discharge slots, said hollow interior
shaft opening having an inner dimension configured to allow an
interference fit with said upstream end of said cylindrical air
guide.
10. The air/oil separator of claim 9, wherein the interference fit
of said upstream end of said cylindrical air guide with said hollow
interior shaft opening of said drive shaft is configured to prevent
air flowing upstream of said plurality of air discharge slots
within said hollow interior chamber.
11. The air/oil separator of claim 10, further comprising at least
one mounting connector fixedly attaching said upstream end of said
cylindrical air guide to said driveshaft upstream of said plurality
of air discharge slots.
12. The air/oil separator of claim 1, wherein said downstream end
of said cylindrical air guide is fixedly coupled with said outlet
end of said rotatable outlet shaft by at least one mounting
connector.
13. The air/oil separator of claim 12, wherein said at least one
mounting connector is configured to permit airflow from exiting
said hollow interior chamber of said rotatable outlet shaft at said
outlet end.
14. The air/oil separator of claim 1, wherein said downstream end
of said cylindrical air guide is coaxially coupled with said outlet
end of said rotatable outlet shaft by cantilevered support of said
upstream end fixedly coupled with said inlet end of said rotatable
outlet shaft.
15. The air/oil separator of claim 1, wherein said nonporous
cylindrical main body comprises a cylindrical outer wall, and
wherein said nonporous cylindrical main body is hollow inside of
said cylindrical outer wall.
16. The air/oil separator of claim 1, wherein said hollow interior
chamber of said rotatable shaft comprises a plurality of interior
sections having a progressively smaller interior diameter
approaching the outlet end of said rotatable outlet shaft.
17. A method for discharging exhaust air from air/oil separator of
a gas turbine engine, the air/oil separator having a separation
chamber and a hollow rotatable outlet shaft, said method
comprising: venting exhaust air from the separation chamber into a
first end of the hollow rotatable outlet shaft through air
discharge slots in a direction substantially perpendicular to a
longitudinal central axis of the hollow rotatable outlet shaft, the
air discharge slots providing air communication between the
separation chamber and the rotatable outlet shaft; rotating the
rotatable outlet shaft around the longitudinal central axis; and
guiding airflow of the exhaust air through the hollow rotatable
outlet shaft, from the first end to a second opposing end thereof,
radially around a cylindrical air guide having a smooth,
uninterruptable outer surface and coaxially mounted within the
rotating outlet shaft about the longitudinal central axis, while
preventing airflow from reaching the central longitudinal axis.
18. The method of claim 17, further comprising discharging the
airflow from the second opposing end of the rotating hollow
rotatable outlet shaft through a radial cross-sectional area
between the rotating outlet shaft and the cylindrical air
guide.
19. A gas turbine engine including a core engine, a compressor, a
high pressure turbine, a low pressure turbine, a combustor
assembly, a fan, and a rotor, said gas turbine engine comprising:
an air/oil separator comprising: a drive shaft having a central
axis extending in an axial direction, said drive shaft coupled with
said gas turbine engine rotor; a free vortex chamber mounted
radially around said drive shaft; a separation chamber coupled with
said free vortex chamber in said axial direction on a side of said
free vortex chamber opposite to said drive shaft; a rotatable
outlet shaft having an inlet end, an outlet end, and a hollow
interior chamber therebetween, said hollow interior chamber having
an inner circumference extending in the axial direction, said inlet
end coupled with said separation chamber on a side of said
separation chamber opposite to said free vortex chamber, and said
rotatable outlet shaft radially rotatable around the axial
direction; and a cylindrical air guide comprising; a nonporous
cylindrical main body having an outer circumference extending
coaxially within said inner circumference of said hollow interior
chamber of said rotatable outlet shaft, said nonporous cylindrical
main body having a cylindrical outer wall with a smooth,
uninterrupted outer surface, and wherein said nonporous cylindrical
main body is hollow inside of said cylindrical outer wall; an
upstream end fixedly coupled with said inlet end of said rotatable
outlet shaft; and a downstream end coaxially disposed within said
outlet end of said rotatable outlet shaft.
20. The gas turbine engine of claim 19, further comprising a
gearbox, wherein said drive shaft is radially coupled with said
gearbox.
Description
BACKGROUND
The field of the disclosure relates generally to gas turbine
engines and, more particularly, to an air guide to control air flow
from an air/oil separator in a gas turbine engine.
Gas turbine engines typically include an air/oil separator (AOS),
also known as deoilers, as part of a vented sump system to separate
air that is intermixed with oil in the bearing compartments and
gearboxes of the gas turbine engine. Separated air exits the AOS
through a vent line in a high-speed free, that is,
unforced-rotational, vortex in a hollow exit shaft. The exiting air
travels at an axial speed downstream a length of the hollow shaft,
while also swirling at a radial, or rotational, flow velocity
around an inner circumference of the exit shaft. In the free
vortex, the rotational flow velocity of the air is inversely
proportional to the distance from the axial center of the hollow
shaft, and thus the rotational velocity of the air traveling down
the central axis of the hollow shaft is significantly higher in the
rotational velocity of the air traveling near the inner
circumference of the hollow shaft. This difference in rotational
velocities in the free vortex creates air friction, which results
in undesirable loss in pressure down the shaft.
At least some conventional AOS venting systems have been known to
place baffles down the central axis of the hollow shaft in a radial
cross configuration, thereby dividing the hollow shaft into four
radial quadrants down its length. This approach, however, creates
miniature vortexes in each of the quadrants, which are subject to
undesirable pressure loss from vortex air friction. Additionally,
the irregular radial shape is another source of air friction that
contributes to pressure loss.
BRIEF DESCRIPTION
In one embodiment, an air/oil separator for a gas turbine engine
includes a drive shaft having a central axis extending in an axial
direction, a free vortex chamber mounted radially around the drive
shaft, a separation chamber coupled with the free vortex chamber in
the axial direction opposite to the drive shaft, and a rotatable
outlet shaft having an inlet end, an outlet end, and a hollow
interior chamber therebetween. The hollow interior chamber has an
inner circumference extending in the axial direction, the inlet end
coupled with the separation chamber opposite to the free vortex
chamber, and the rotatable outlet shaft radially rotatable around
the axial direction. The air/oil separator further includes a
cylindrical air guide having a nonporous cylindrical main body with
an outer circumference extending coaxially within the inner
circumference of the hollow interior chamber of the rotatable
outlet shaft. The cylindrical air guide further includes an
upstream end fixedly coupled with the inlet end of the rotatable
outlet shaft, and a downstream end coaxially disposed within the
outlet end of the rotatable outlet shaft.
In another embodiment, a method for discharging exhaust air from
air/oil separator of a gas turbine engine, the air/oil separator
having a separation chamber and a hollow rotatable outlet shaft,
includes venting exhaust air from the separation chamber into a
first end of the hollow rotatable outlet shaft through air
discharge slots in a direction substantially perpendicular to a
longitudinal central axis of the hollow rotatable outlet shaft. The
air discharge slots provide air communication between the
separation chamber and the rotatable outlet shaft. The method
further includes rotating the rotatable outlet shaft around the
longitudinal central axis, and guiding airflow of the exhaust air
through the hollow rotatable outlet shaft, from a first end of the
shaft to a second opposing end thereof, radially around a
cylindrical air guide coaxially mounted within the rotating outlet
shaft about the longitudinal central axis, while preventing airflow
from reaching the central longitudinal axis.
In yet another embodiment, a gas turbine engine includes a core
engine, a compressor, a high pressure turbine, a low pressure
turbine, a combustor assembly, a fan, a rotor, and an air/oil
separator. The air/oil separator includes a drive shaft having a
central axis extending in an axial direction. The drive shaft is
coupled with the gas turbine engine rotor. The air/oil separator
further includes a free vortex chamber mounted radially around the
drive shaft, a separation chamber coupled with the free vortex
chamber in the axial direction opposite to the drive shaft, and a
rotatable outlet shaft having an inlet end, an outlet end, and a
hollow interior chamber therebetween. The hollow interior chamber
has an inner circumference extending in the axial direction, the
inlet end coupled with the separation chamber opposite to the free
vortex chamber, and the rotatable outlet shaft radially rotatable
around the axial direction. The air/oil separator further includes
a cylindrical air guide having a nonporous cylindrical main body
with an outer circumference extending coaxially within the inner
circumference of the hollow interior chamber of the rotatable
outlet shaft. The cylindrical air guide further includes an
upstream end fixedly coupled with the inlet end of the rotatable
outlet shaft, and a downstream end fixedly coupled with the outlet
end of the rotatable outlet shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, aspects, and advantages of the present
disclosure 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:
FIGS. 1-4 show example embodiments of the method and system
described herein.
FIG. 1 illustrates a sectional schematic view of a gas turbine
engine.
FIG. 2 illustrates an oblique perspective view of an air/oil
separator.
FIG. 3 illustrates a sectional perspective view of an air/oil
separator for a gas turbine engine, in which an aspect of the
methods and systems described herein may be employed in accordance
with one embodiment of the present disclosure.
FIG. 4 illustrates a sectional schematic view of an exemplary
embodiment of an air/oil separator for a gas turbine engine.
Although specific features of various embodiments may be shown in
some drawings and not in others, this is for convenience only. Any
feature of any drawing may be referenced and/or claimed in
combination with any feature of any other drawing.
Unless otherwise indicated, the drawings provided herein are meant
to illustrate features of embodiments of the disclosure. These
features are believed to be applicable in a wide variety of systems
comprising one or more embodiments of the disclosure. As such, the
drawings are not meant to include all conventional features known
by those of ordinary skill in the art to be required for the
practice of the embodiments disclosed herein.
DETAILED DESCRIPTION
In the following specification and the claims, reference will be
made to a number of terms, which shall be defined to have the
following meanings.
The singular forms "a", "an", and "the" include plural references
unless the context clearly dictates otherwise.
"Optional" or "optionally" means that the subsequently described
event or circumstance may or may not occur, and that the
description includes instances where the event occurs and instances
where it does not.
Approximating language, as used herein throughout the specification
and claims, may be applied to modify any quantitative
representation that could permissibly vary without resulting in a
change in the basic function to which it is related. Accordingly, a
value modified by a term or terms, such as "about",
"approximately", and "substantially", are not to be limited to the
precise value specified. In at least some instances, the
approximating language may correspond to the precision of an
instrument for measuring the value. Here and throughout the
specification and claims, range limitations may be combined and/or
interchanged, such ranges are identified and include all the
sub-ranges contained therein unless context or language indicates
otherwise.
The following detailed description illustrates embodiments of the
disclosure by way of example and not by way of limitation. It is
contemplated that the disclosure has general application to
increasing recovered pressure from airflow into a bleed cavity of a
gas turbine engine.
The following description refers to the accompanying drawings, in
which, in the absence of a contrary representation, the same
numbers in different drawings represent similar elements.
FIG. 1 is a schematic illustration of an exemplary gas turbine
engine 100. Gas turbine engine 100 includes a gas generator or core
engine 102 that includes a high pressure compressor (HPC) 104, a
combustor assembly 106, and a high pressure turbine (HPT) 108 in an
axial serial flow relationship on a core engine rotor 110 rotating
about a core engine shaft 112. Gas turbine engine 100 also includes
a low pressure compressor 114 and a fan 116, and a low pressure
turbine 118 arranged in an axial flow relationship on an engine
rotor 120 by power engine shaft 122.
During operation, air flows along a central axis 124, and
compressed air is supplied to high pressure compressor 104. Highly
compressed air is then delivered to combustor assembly 106. Exhaust
gas flow from combustor assembly 106 drives turbine 108, and
turbine 108 drives engine rotor 120, in addition to low pressure
compressor 114 and fan 116. Gas turbine engine 100 also includes a
containment case 126 for low pressure compressor 114 and fan
116.
Furthermore, additional and/or different elements not shown may be
contained in, or coupled to the elements shown in FIG. 1, and/or
certain illustrated elements may be absent. In some examples, the
functions provided by the illustrated elements could be performed
by less than the illustrated number of components or even by a
single element.
FIG. 2 illustrates an embodiment of an air/oil separator (AOS) 200
for a gas turbine engine (e.g., gas turbine engine 100, FIG. 1). In
an exemplary embodiment, AOS 200 is a rotating free vortex
configuration, and includes a drive shaft 202, a free vortex
chamber 204, a separation chamber 206, and a rotatable outlet shaft
208. Free vortex chamber 204 includes a vent inlet 210 and a
scavenging inlet 212.
Drive shaft 202 extends in an axial direction down central axis 214
and is coupled to a forward portion 216 of free vortex chamber 204.
Separation chamber 206 couples with free vortex chamber 204 along
central axis 214 opposite drive shaft 202. Rotatable outlet shaft
208 couples with separation chamber 206 along central axis 214
opposite free vortex chamber 204. Vent inlet 210 and scavenging
inlet 212 approach free vortex chamber 204 tangentially to an outer
circumference 218 of free vortex chamber 204, and in a direction of
rotation 220 of rotatable outlet shaft 208.
In operation, air-oil mixtures flow into vent inlet 210 from
direction 222, and into scavenging inlet 212 from direction 224,
and the two air-oil mixtures are combined at high rotational speeds
within free vortex chamber 204 around drive shaft 202. The rotating
air-oil mixture proceeds from free vortex chamber 204 into
separation chamber 206 and encounters rotating separator vanes (see
element 330, FIG. 3), which steer encountered oil droplets from the
combined mixture radially toward an outer wall 226 of separation
chamber 206 by centrifugal action of rotating separator vanes. Once
reaching outer wall 226, the radially steered oil can be collected
and fed back into the engine as desired. In an exemplary
embodiment, AOS 200 can be integrated axially or radially with a
gearbox drive shaft, a low pressure turbine shaft or other suitable
rotating components shown in FIG. 1.
FIG. 3 illustrates an exemplary embodiment of an AOS 300 for a gas
turbine engine (e.g., gas turbine engine 100, FIG. 1). AOS 300 is
similar to AOS 200 (FIG. 2) in external construction and overall
function. In an aspect of the embodiment, AOS 300 is also a
rotating free vortex configuration, and similarly includes a drive
shaft 302, a free vortex chamber 304, a separation chamber 306, and
a rotatable outlet shaft 308.
Drive shaft 302 extends in an axial direction down central axis 309
and is coupled to a forward portion 311 of free vortex chamber 304.
Separation chamber 306 couples with free vortex chamber 304 along
central axis 309 on a side of free vortex chamber (not numbered)
opposite drive shaft 302. Rotatable outlet shaft 308 couples with
separation chamber 306 along central axis 309 on a side (not
numbered) of separation chamber 306 opposite free vortex chamber
304. Rotatable outlet shaft 308 includes a cylindrical air guide
310 disposed along central axis 309 within an inner circumference
312 of rotatable outlet shaft 308. Cylindrical air guide 310
includes a nonporous outer wall 314 having an outer diameter 316.
Inner circumference 312 of rotatable outlet shaft 308 has a
diameter 318 that is greater than diameter 316 of cylindrical air
guide 310.
Cylindrical air guide 310 further includes an upstream end 320 and
a downstream end 322. Nonporous outer wall 314 of cylindrical air
guide 310 is cylindrically shaped, and runs substantially parallel
to inner circumference 312 of rotatable outlet shaft 308 from
upstream end 320 to downstream end 322. In this exemplary
embodiment, upstream end 320 of cylindrical air guide 310 is
fixedly attached to inner circumference 312 of rotatable outlet
shaft 308, between free vortex chamber 304 and separation chamber
306, by an upstream mount 324. Upstream mount 324 is ring-shaped or
disc-shaped, is nonporous and extends between cylindrical air guide
310 and rotatable outlet shaft 308. Upstream mount 324 prevents
airflow between cylindrical air guide 310 and rotatable outlet
shaft 308 from moving upstream toward drive shaft 302.
In the exemplary embodiment, downstream end 322 of cylindrical air
guide 310 is not fixedly attached to inner circumference 312 of
rotatable outlet shaft 308, and is held coaxially with inner
circumference 312 by the cantilevered attachment of upstream end
320 to inner circumference 312 by upstream mount 324. In an
alternative embodiment, downstream end 322 is fixedly attached to
inner circumference 312 of rotatable shaft 308 by a mounting
fastener 326. In one embodiment, mounting fastener 326 is a single
bolt passing through downstream end 322 and across the entirety of
inner diameter 318. In further alternative embodiments, mounting
fastener 326 includes a plurality of connectors, or a single
mounting spider configuration, fixedly attaching nonporous outer
wall 314 to inner circumference 312. Mounting fastener 326 is
configured to allow airflow between cylindrical air guide 310 and
rotatable outlet shaft 308 while exiting rotatable outlet shaft 308
in an exit direction 328.
In operation, an air-oil mixture is injected into free vortex
chamber 304 through a vent inlet (see element 210, FIG. 2) and a
scavenging inlet (see element 212, FIG. 2), and the combined
air-oil mixture is rotated together at high speeds (e.g. 12,000 rpm
or greater) to create a free vortex phenomenon within free vortex
chamber 304. The free vortex in free vortex chamber 304 allows
relatively large oil particles to be separated from the air/air-oil
mixture and propelled radially outward toward an outer
circumference (e.g., outer circumference 218, FIG. 2) of free
vortex chamber 304 for collection and redistribution. The "large"
oil particles are those having sufficient size such that they can
be moved outwardly by the force of the free vortex alone within
free vortex chamber 304. The free vortexing air-oil mixture then
flows into separation chamber 306 through a passage (not shown)
between free vortex chamber 304 and separation chamber 306, where a
plurality of rotating separator vanes 330 remove smaller oil
particles from the mixture, as described above with respect to FIG.
2. The "small" oil particles are those having sufficient size such
that they can condense on rotating separator vanes 330 and then be
moved outwardly by centrifugal force of the spinning vanes.
Substantially oil-free exhaust air is then forced from separation
chamber 306 through air discharge slots 332 in rotatable outlet
shaft 308 in a radial direction 334. Air discharge slots 332 allow
air communication between rotatable outlet shaft 308 and separation
chamber 306.
In further operation, rotatable outlet shaft 308 and rotating
separator vanes 330 rotate in a rotational direction 336 at a
significant percentage of the rotational speed of the core engine
rotor about the core engine shaft (e.g., elements 110, 112,
respectively, FIG. 1). Air flowing into rotatable outlet shaft 308
from air discharge slots 332 rotates around central axis 309, at a
percentage of the rotational speed of rotatable outlet shaft 308,
due to air friction with rotating inner circumference 312 of
rotatable outlet shaft 308. Upstream mount 324 and mounting
fastener 326 fixedly couple cylindrical air guide 310 to rotatable
outlet shaft 308 such that cylindrical air guide 310 rotates at the
same rotational speed as rotatable outlet shaft 308.
In an exemplary embodiment, an inner diameter 338 of separation
chamber 306 is greater than inner diameter 318 of rotatable outlet
shaft 308, and therefore rotational speed of air entering rotatable
outlet shaft 308 is greater than the rotational speed of the air in
separation chamber 306. The rotation of the swirling air entering
rotatable outlet shaft 308 is faster as the air gets closer to
central axis 309. This relative acceleration of air with respect to
smaller radii is what is known as the free vortexing phenomenon
that airflow exhibits within cylindrical bodies.
In practice, cylindrical airflow through AOS 300 experiences a
"tornado" effect, where the rotational velocity of air near central
axis 309 can be seen to be more than five times greater than the
rotational velocity of air entering rotatable outlet shaft 308 in
direction 334. At the typical rotational speed of AOS 300 utilized
in operation, for example, the rotational velocity of free
vortexing air along central axis 309 within rotatable outlet shaft
308 can reach Mach 1 speeds, and thereby result significant in
undesirable pressure losses.
Cylindrical air guide 310 is thus configured to create a smaller
diameter (i.e., outer diameter 316), coaxial shaft within a larger
shaft (i.e. rotatable outlet shaft 308 having inner diameter 318),
thereby creating an annular flow path 340 through outlet shaft 308
around cylindrical air guide 310. Cylindrical air guide 310
prevents airflow from reaching central axis 309, and therefore also
limits the difference in rotational velocities between airflow near
inner circumference 312 and airflow near nonporous outer wall 314.
By limiting this difference, air friction from the free vortex
phenomenon is significantly reduced, and therefore the loss in
pressure from upstream end 320 to downstream end 322 is also
significantly reduced. In practice, air friction created near
nonporous outer wall 314 of cylindrical air guide 310 is
considerably less than the air friction known to be created at
central axis 309 by the free vortex phenomenon, without the air
guide present.
In an aspect of the embodiment, outer diameter 316 and inner
diameter 318 are sized such that the annular, radial cross
sectional area (not shown) of available airflow between the
diameters is substantially equivalent to the radial cross sectional
area of an outlet shaft of a conventional AOS. Too much of a
decrease in the cross-sectional area of available airflow within
the outlet shaft can also lead to pressure loss from having the
same volume of airflow pass through a smaller opening. By
increasing the inner diameter (i.e., inner diameter 318) of the
outlet shaft (i.e., rotatable outlet shaft 308) to compensate for
the loss of radial sectional area now centrally occupied by
cylindrical air guide 310, a consistent radial cross-sectional area
can be maintained. In an exemplary embodiment, inner diameter 318
of rotatable outlet shaft 308 can be gradually decreased in a first
region 342 and a second region 344, respectively, of inner
circumference 312 near downstream end 322, to further guide the
airflow exiting in direction 328.
In a further aspect of the embodiment, inner circumference 312 of
rotatable outlet shaft 308 and nonporous outer wall 314 of
cylindrical air guide 310 are smooth surfaces, to further minimize
friction from airflow near both respective surfaces. Smooth,
rounded surfaces to both respective circumferences 312, 314 will
also help to reduce pressure loss through AOS 300 by allowing the
airflow to more easily transition the substantially ninety degree
turn from direction 334 at upstream end 320, to direction 328 at
downstream end 322. In an exemplary embodiment, downstream end 322
of cylindrical air guide 310 is aerodynamically shaped to further
encourage a smooth exit to the airflow direction 328.
In a still further aspect of the embodiment, cylindrical air guide
310 has a hollow interior to avoid an unnecessary increase in the
weight of AOS 300. For the same length, a cylindrical air guide
according to the present embodiments weighs less than the
conventional cross-shaped baffle, when the thickness of the
cylinder wall is the same as the thickness of the spokes in the
conventional cross-shaped baffle. Cylindrical air guide 310
therefore uses less material, and the cylindrical shape is easier
to fabricate than the conventional cross-shape.
FIG. 4 illustrates an alternative exemplary embodiment of an AOS
400 for a gas turbine engine (e.g., gas turbine engine 100, FIG.
1). AOS 400 is similar to AOS 300 (FIG. 3) in construction and
overall function, and differs primarily from AOS 300 with respect
to how upstream end 320 of cylindrical air guide 310 couples with
drive shaft 302. Similar to AOS 300, in an aspect of this
alternative embodiment, AOS 400 is also a rotating free vortex
configuration.
AOS 400 includes a drive shaft 402, a rotatable outlet shaft 404,
and a cylindrical air guide 406. Cylindrical air guide 406 includes
an upstream end 408 and a downstream end 410. Downstream end 410
fixedly attaches to rotatable outlet shaft 404 by a plurality of
mounting connectors 412, similar to the attachment of downstream
end 322 with rotatable outlet shaft 308 by mounting connector 326
in FIG. 3. Driveshaft 402, rotatable outlet shaft 404, and
cylindrical air guide 406 extend in an axial direction along
central axis 414, and cylindrical air guide 406 is coaxially
mounted within an interior circumference 416 of rotatable outlet
shaft 404.
Driveshaft 402 includes a hollow inner portion 418. Hollow inner
portion 418 includes an interior circumference 420 sized to provide
an interference fit with an outer diameter 422 of cylindrical air
guide 406. In an aspect of the embodiment, outer diameter 422 of
upstream end 408 securely fits within a region 424 of hollow inner
portion 418 such that airflow into rotatable outlet shaft 404, from
an air discharge slot in a direction 429, is prevented from
traveling upstream into hollow inner portion 418. In an optional
configuration, upstream end 408 of cylindrical air guide 406 is
alternatively, or additionally, fixedly secured to driveshaft 402
by one or more mounting connectors 428.
In an alternative embodiment, downstream end 410 does not fixedly
attach to rotatable outlet shaft 404, and is instead cantilevered
by the fixed attachment of outer diameter 422 to interior
circumference 420 of hollow inner portion 418. In this
configuration, downstream end is disposed within, and maintains a
coaxial coupling with, interior circumference 420 without requiring
a direct mounting connection to interior circumference 420. In an
optional configuration of the alternative embodiment, downstream
end is aerodynamically inwardly toward central axis 414 and in the
direction of airflow exiting rotatable outlet shaft 404.
The foregoing detailed description illustrates embodiments of the
disclosure by way of example and not by way of limitation. It is
contemplated that the disclosure has general application to air/oil
separators and sump venting for various purposes. It is further
contemplated that the methods and systems described herein may be
incorporated into existing aircraft engine designs and
structures.
It will be appreciated that the above embodiments that have been
described in particular detail are merely example or possible
embodiments, and that there are many other combinations, additions,
or alternatives that may be included. The apparatus illustrated is
not limited to the specific embodiments described herein, but
rather, components of each may be utilized independently and
separately from other components described herein. Each system
component can also be used in combination with other system
components.
Approximating language, as used herein throughout the specification
and claims, may be applied to modify any quantitative
representation that could permissibly vary without resulting in a
change in the basic function to which it is related. Accordingly, a
value modified by a term or terms, such as "about" and
"substantially", are not to be limited to the precise value
specified. In at least some instances, the approximating language
may correspond to the precision of an instrument for measuring the
value. Here and throughout the specification and claims, range
limitations may be combined and/or interchanged, such ranges are
identified and include all the sub-ranges contained therein unless
context or language indicates otherwise.
While the disclosure has been described in terms of various
specific embodiments, it will be recognized that the disclosure can
be practiced with modification within the spirit and scope of the
claims.
This written description uses examples to describe the disclosure,
including the best mode, and also to enable any person skilled in
the art to practice the disclosure, including making and using any
devices or systems and performing any incorporated methods. The
patentable scope of the disclosure 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
languages of the claims.
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