Information
-
Patent Grant
-
6217277
-
Patent Number
6,217,277
-
Date Filed
Tuesday, October 5, 199924 years ago
-
Date Issued
Tuesday, April 17, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Look; Edward K.
- Rodriguez; Hermes
Agents
-
CPC
-
US Classifications
Field of Search
US
- 415 1731
- 415 1733
- 415 1734
- 415 1742
- 415 1744
- 415 229
- 416 174
-
International Classifications
-
Abstract
An improved rotary engine, engine lining and engine casing and lining combination are disclosed. The engine is preferable a turbofan engine and includes a fan blade, rotatably mounted within a generally cylindrical casing for rotation about a lengthwise extending central axis. An annular lining is mounted within the casing between a tip of the fan blade and the casing. The lining seals the tip of the fan blade within the casing. The lining includes a brush seal that extends around an inner circumference of the casing, and has a plurality of bristles that extend radially inward from the seal. A retaining membrane extends around the brush seal, preventing the bristles from extending substantially in a radial direction from the brush seal. The retaining membrane is adapted to release the bristles to extend radially inward to occupy a region between the tip of the fan blade and the casing upon a radial excursion of the fan blade. The bristles, once released, at least partially seal the tip of the fan blade and the casing reducing air recirculation at the blade tip.
Description
FIELD OF THE INVENTION
The present invention relates to rotary engines, and more particularly to turbofan engines having a fan blade lining including a hidden brush seal.
BACKGROUND OF THE INVENTION
In most turbofan engines, a lining is mounted between the engine casing and the first compressor stage or fan blade. The lining provides a tight clearance between the tip of the fan blade and the casing. In order to minimize the consequence of inadvertent contact between the rotating fan blade and the lining, the lining is formed from a material that may be abraded by the blade, and is often referred to as an abradable. An example abradable is disclosed in U.S. Pat. No. 5,655,701.
In the event the blade is struck by a foreign object, such as a bird entering the air intake of the engine, the fan blade may make a radial excursion coming into contact with the lining. As a result of the radial excursion, the lining is shorn by the fan blade tip. For a foreign object of significant size, up to 0.3″ (0.8 cm) of the abradable may be shorn. This, in turn, significantly increases the blade tip clearance, and may cause air recirculation at the blade tip. As a result the fan blade may stall at its outer span, causing serious consequences to the engine, such as engine surges.
Often, engine casings include slots extending into the compressor section near the fan blan. These slots increase the clearance margin before the tip of the blade stalls (referred to as stall margin). However, these slots also reduce overall engine performance.
Accordingly, an improved lining, reducing susceptibility of the engine to consequences of radial excursions of a fan blade is desirable.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved rotary engine and an improved fan blade lining for the casing of a rotary engine.
In accordance with an embodiment of the present invention, an engine includes a fan blade, rotatably mounted within a generally cylindrical casing for rotation about a lengthwise extending central axis of the engine. An annular lining is mounted within the casing between a tip of the fan blade and the casing. The lining includes a brush seal that extends around an inner circumference of the casing, and has a plurality of bristles that extend radially inward from the seal. A retaining membrane extends around the brush seal, and prevents the bristles from extending substantially in a radial direction from the brush seal. The retaining membrane is adapted to release the bristles to occupy a radial region between the tip of the fan blade and the casing upon a radial excursion of the fan blade. The bristles, once released, at least partially seal the tip of the fan blade. The invention may be embodied in a rotary engine; and engine lining; or the combination of an engine casing and lining.
Other aspects and features of the present invention will become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
In figures, which illustrate by way of example only, embodiments of the present invention:
FIG. 1
is a partial cross-sectional view of a rotary engine, exemplary of an embodiment of the present invention;
FIG. 2A
is a further enlarged view of a portion of
FIG. 1
;
FIG. 2B
is a front view of a portion the engine of
FIG. 1
, in cross section;
FIG. 3A
illustrates the view of
FIG. 2A
after a radial excursion of a fan of the engine of
FIG. 1
;
FIG. 3B
illustrates the front view of
FIG. 2B
after the radial excursion of a fan blade of the engine of
FIG. 1
;
FIG. 4A
illustrates an enlarged view of a portion of a conventional turbofan engine, similar to the view of
FIG. 2A
;
FIG. 4B
illustrates an enlarged view of a portion of the conventional turbofan engine of
FIG. 4A
, similar to the view of
FIG. 3A
; and
FIG. 5
is an enlarged cut-away view of another engine, exemplary of a second embodiment of the present invention.
DETAILED DESCRIPTION
FIG. 1
illustrates a turbofan engine
10
, exemplary of an embodiment of the present invention. Engine
10
includes, from front to rear a conventional fan section
12
; conventional core engine section
14
, including at least one axial compressor, combustion section, and at least one turbine; and a conventional exhaust section
16
, all mounted within a generally cylindrical casing
18
. A by-pass duct
20
, extends about core engine section
14
, within casing
18
.
As illustrated, fan section
12
includes a rotatable fan blade
22
, mounted for axial rotation about a main central axis of engine
10
. A lining
24
including a conventional abradable
26
extends circumferentially about the interior of casing
18
, between casing
18
and the tip of fan blade
22
. Abradable
26
is made of a conventional material, such as an epoxy potting compound and may be bonded to the interior of casing
18
. The tip of fan blade
22
extends in close proximity to abradable
26
. Abradable
26
thus seals the tip of fan blade
22
within casing
18
.
FIG. 2A
illustrates an enlarged view of a portion of
FIG. 1
, more particularly illustrating lining
24
. As illustrated, the region of liner
24
occupied by abradable
26
is made up of two portions, a front and aft portion
30
and
32
. Mounted between front and aft abradable portions
30
and
32
is a hidden brush seal
34
, retained between portions
30
and
32
by a retaining membrane
36
. Brush seal
34
includes a plurality bristles
38
, hidden by membrane
36
. These are compressed in a direction generally tangent to the outer circumference of casing
18
by membrane
36
as best illustrated in FIG.
2
B. For reasons that will become apparent, the bristles
38
of brush seal
34
are cocked in a direction, generally tangent to the rotation of fan blade
22
, at a relatively large angle. Preferably brush seal
34
, and in particular bristles
38
may be made of a cobalt based alloy, such as HAYNES-25. Membrane
36
is preferably a ring formed of an easily breakable material, such as plastic, and may be partially embedded in abradable portions
30
and
32
. Lining
24
including brush seal
34
and abradable
26
may be affixed to the casing
18
by bonding, bolting, brazing or in any other suitable manner known to those of ordinary skill in the art.
In normal, steady-state, operation fan blade
22
draws air into a compressor section of core engine section
14
, of engine
10
(FIG.
1
). Similarly, blade
22
draws air through by-pass duct
20
, about the main engine section
14
. Compressed air exits the compressor section and enters the combustion chamber (not shown) where it is admixed with fuel. The fuel and air mixture is combusted, and exits the rear of the combustion chamber to at least one turbine, coupled to cause fan blade
22
to rotate. Exhaust gases are discharged through exhaust section
16
.
In normal operation, abradable
26
seals the tip of fan blade
22
within casing
18
, thereby preventing recirculation of air at its tip.
Now, if fan blade
22
is struck by a foreign object, such as for example a bird, fan blade
22
may undergo a radial excursion. Of course, this will depend on the relative size of the foreign object to fan blade
22
and engine
10
. Two one (1) pound birds, for example, may cause as much as a 0.3″ (0.8 cm) radial excursion for a typical fan blade. This radial excursion causes fan blade
22
to contact abradable
26
and shear or tear abradable
26
, as illustrated in FIG.
3
A. Similarly, membrane
36
is at least partially torn by fan blade
22
, undergoing its radial excursion. Once membrane
36
is torn, some or all of the hidden bristles
38
of brush seal
34
become liberated. Advantageously, membrane
36
and abradable
26
buffer the impact of fan blade
22
, limiting damage caused by fan blade
22
to brush seal
34
. As membrane
36
cocks bristles
38
in the direction of rotation of fan
20
, and bristles
38
are flexible, they are not immediately cut by rotating fan
20
. Instead, the bristles
38
of brush seal
34
extend radially inward gradually, and particularly once fan blade
22
has completed its radial excursion and is again centered about its axis of rotation, as best illustrated in FIG.
3
B. The liberated bristles
38
of brush seal
34
now occupy much of the radial gap formerly occupied by abradable
26
. As will be appreciated, depending on the nature of the radial excursion, not all areas of lining
24
need be contacted by fan blade
22
. Instead only, a portion of lining
24
and membrane
36
may be shorn, and only some of the bristles
38
may be liberated. In any event, as a result of the liberated bristles
38
, recirculation at the fan tip is reduced or eliminated. Similarly, any associated stalling of the fan at its outer span and any resulting engine surge is reduced or eliminated, so that an aircraft can land safely after the foreign object has struck.
As should be appreciated, once membrane
36
is broken, engine
10
should be serviced to replace or repair lining
24
. As will further be appreciated, constant contact between the tip of fan blade
22
and bristles
38
will cause bristles
38
to wear.
The operation of exemplary engine
10
, and recirculation of air at the tip of its fan blade
22
may be better appreciated with reference to
FIGS. 4A and 4B
illustrating a portion of a conventional turbofan engine
100
, similar to the portion of turbofan engine
10
illustrated in
FIGS. 2A and 3A
. As illustrated, the conventional turbofan includes fan blade
122
, and an abradable
126
mounted within casing
118
. Engine
100
, however, does not include lining including a membrane and hidden brush seal. In normal operation, air is drawn into engine
100
, as illustrated in FIG.
4
A. Upon a radial excursion of blade
122
, as illustrated in
FIG. 4B
, abradable
118
is shorn, causing air to recirculate at the tip of blade
122
. This, recirculating air causes a blockage region near the tip of blade
122
, as illustrated. In this region, air cannot be adequately drawn into the engine
100
, thereby potentially causing the engine to stall. In exemplary engine
10
, on the other hand the extension of brush seal
38
reduces recirculation at the tip of fan blade
22
thereby reducing the size of the blocked region and reducing the likelihood of stall, as illustrated in FIG.
3
A.
In a second embodiment illustrated in
FIG. 5
, several brush seals
34
′ may be combined in a single lining
24
′. As illustrated two or more brush seals mounted
34
′ including bristles
38
′ form part of lining
24
′ and are mounted beside each other, also circumferentially about casing
18
′ at the tip of fan blade
22
′. Abradable
26
′ made of three regions also form part of lining
24
′. The bristles
38
′ of the multiple brush seals
34
′ may all be retained and released by membrane, formed of membrane portions
36
′
a
and
36
′
b
in a manner analogous to bristles
38
of membrane
36
(as illustrated in
FIGS. 2A
,
2
B,
3
A and
3
B).
As will be appreciated lining
24
(or
24
′) and casing
18
may be combined in an article of manufacturer produced by a casing supplier, into which the remainder of engine
10
may be inserted.
The above described embodiments are intended to be illustrative only, and in no way limiting. The embodiments are susceptible to many modifications of form, size, arrangement of parts and details of operation. For example, while retaining membranes
36
and
36
′ have been described as breaking upon radial excursion of fan blade
22
and
22
′, these membranes could be otherwise adapted to release bristles
38
and
38
′. For example, membrane
38
could be retractable.
The invention, rather, is intended to encompass all such modification within its scope as defined by the claims.
Claims
- 1. A rotary engine comprising:a generally cylindrical casing; a fan blade, rotatably mounted within said casing for rotation about a lengthwise extending central axis of said engine; an annular lining mounted within said casing between a tip of said fan blade and said casing, sealing said tip of said fan blade within said casing, said lining comprising: a brush seal, extending around an inner circumference of said casing, comprising a plurality of bristles extending radially inward from said brush seal; a retaining membrane extending around said brush seal, preventing said bristles from extending substantially in a radial direction from said brush seal; whereby said retaining membrane is adapted to release said bristles to extend radially inward and occupy a region between said tip of said fan blade and said casing to at least partially seal said tip of said fan blade within said casing upon a radial excursion of said fan blade.
- 2. The rotary engine of claim 1, wherein said retaining membrane may be broken by a radial excursion of said fan blade.
- 3. The rotary engine of claim 2, wherein said lining further comprises an abradable region, extending around an inner circumference of said casing, adjacent to said brush seal.
- 4. The rotary engine of claim 3, wherein said abradable region extends around said inner circumference of said casing, adjacent to said brush seal, before and aft of said brush seal along a length of said casing.
- 5. The rotary engine of claim 2, wherein said retaining membrane comprises an annular ring.
- 6. The rotary engine of claim 5, wherein said annular ring is formed of plastic.
- 7. The rotary engine of claim 6, wherein said annular ring is at least partially embedded within, and retained by said abradable region, and wherein said abradable region is shorn by said radial excursion.
- 8. The rotary engine of claim 7, wherein said abradable region is formed of epoxy potting compound.
- 9. The rotary engine of claim 2, wherein said retaining membrane retains said bristles generally tangent to said lining, in a direction tangent to a rotation of said fan blade.
- 10. The rotary engine of claim 2, wherein said lining further comprises:a second brush seal, extending around said inner circumference of said lining, and having a plurality of bristles extending radially inward from said second brush seal; and wherein said retaining membrane prevents said bristles of said second brush seal from extending substantially in a radial direction from said second brush seal; whereby said retaining membrane is adapted to release said bristles of said second brush seal to extend radially inward and occupy a second region between said tip of said fan blade and said casing to further seal said tip of said fan blade within said casing.
- 11. A lining, mountable within a generally cylindrical casing of a rotary engine between a tip of a fan blade of said engine and said casing, said lining comprising:a brush seal comprising a plurality of bristles, said brush seal extending around an inner circumference of said casing and said bristles extending radially inward from said brush seal, when said lining is mounted within said casing; a retaining membrane extending around said brush seal, preventing said bristles from extending substantially in a radial direction from said brush seal, when said lining is mounted within said casing; whereby said retaining membrane is adapted to release said bristles to extend radially inward and occupy a region between said tip of said fan blade and said casing to at least partially seal said tip of said fan blade within said casing upon a radial excursion of said fan blade.
- 12. The lining of claim 11, wherein said retaining membrane may be broken by a radial excursion of said fan blade.
- 13. The lining of claim 12, further comprising an abradable region, extending adjacent to said brush seal around an inner circumference of said casing, when said lining is mounted within said casing.
- 14. The lining of claim 13, wherein said abradable region extends around said inner circumference of said casing, adjacent to said brush seal, before and aft of said brush seal along a length of said casing when said lining is mounted within said casing.
- 15. The lining of claim 13, wherein said membrane is embedded and retained by said abradable region.
- 16. The lining of claim 15, wherein said abradable region is formed of epoxy potting compound.
- 17. The lining of claim 12, wherein said retaining membrane is formed of plastic.
- 18. The lining of claim 12, wherein said retaining membrane retains said bristles generally tangent to said lining, in a direction tangent to a rotation of said fan blade, when said lining is mounted within said casing.
- 19. The lining of claim 12, further comprising:a second brush seal, extending around said inner circumference of said lining, and having a plurality of bristles extending radially inward from said second brush seal, when said lining is mounted within said casing; and wherein said retaining membrane prevents said bristles of said second brush seal from extending substantially in a radial direction from said second brush seal; whereby said retaining membrane is adapted to release said bristles of said second brush seal to extend radially inward and occupy a second region between said tip of said fan blade and said casing to further seal said tip of said fan blade within said casing.
- 20. A rotary engine comprising:a generally cylindrical casing; a fan blade, rotatably mounted within said casing for rotation about a lengthwise extending central axis of said engine; an annular lining mounted within said casing between a tip of said fan blade and said casing, said lining comprising: a brush seal, extending around an inner circumference of said casing, comprising a plurality of bristles extending radially inward from said brush seal; means for preventing said bristles from extending substantially in a radial direction from said brush seal, and releasing said bristles to extend radially inward between said tip of said fan blade and said casing upon a radial excursion of said fan blade, to at least partially seal said tip of said fan blade within said casing.
- 21. An article of manufacture, comprising:a generally cylindrical casing for a rotary engine; and an annular lining mounted within said casing to rest between a tip of a fan blade of said rotary engine and said casing, sealing said tip of said fan blade within said casing, said lining comprising: a brush seal, extending around an inner circumference of said casing, comprising a plurality of bristles extending radially inward from said brush seal; a retaining membrane extending around said brush seal, preventing said bristles from extending substantially in a radial direction from said brush seal; whereby said retaining membrane is adapted to release said bristles to extend radially inward and occupy a region between said tip of said fan blade and said casing to at least partially seal said tip of said fan blade within said casing upon a radial excursion of said fan blade.
- 22. The article of manufacture of claim 21, wherein said retaining membrane may be broken by a radial excursion of said fan blade.
- 23. The article of manufacture of claim 22, wherein said liner further comprises an abradable region, extending adjacent to said brush seal around an inner circumference of said casing.
- 24. The article of manufacture of claim 23, wherein said abradable region extends around said inner circumference of said casing, adjacent to said brush seal, before and aft of said brush seal along a length of said casing.
- 25. The article of manufacture of claim 22, wherein said membrane is embedded and retained by said abradable region.
- 26. The article of manufacture of claim 22, wherein said abradable region is formed of epoxy potting compound.
- 27. The article of manufacture of claim 22, wherein said retaining membrane is formed of plastic.
- 28. The article of manufacture of claim 22, wherein said retaining membrane retains said bristles generally tangent to said lining, in a direction tangent to a rotation of said fan blade.
- 29. The article of manufacture of claim 22, further comprising:a second brush seal, extending around said inner circumference of said lining, and having a plurality of bristles extending radially inward from said second brush seal, when said lining is mounted within said casing; and wherein said retaining membrane prevents said bristles of said second brush seal from extending substantially in a radial direction from said second brush seal; whereby said retaining membrane is adapted to release said bristles of said second brush seal to extend radially inward and occupy a second region between said tip of said fan blade and said casing to further seal said tip of said fan blade within said casing.
US Referenced Citations (6)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0 947 746 |
Oct 1999 |
EP |
2333137 |
Jul 1999 |
GB |