U.S. patent application number 15/195429 was filed with the patent office on 2016-12-22 for pitch control of contra-rotating airfoil blades.
The applicant listed for this patent is GE Aviation Systems Limited. Invention is credited to Aleksander Krzysztof Szymandera.
Application Number | 20160368592 15/195429 |
Document ID | / |
Family ID | 44838786 |
Filed Date | 2016-12-22 |
United States Patent
Application |
20160368592 |
Kind Code |
A1 |
Szymandera; Aleksander
Krzysztof |
December 22, 2016 |
PITCH CONTROL OF CONTRA-ROTATING AIRFOIL BLADES
Abstract
A pitch control mechanism for an open rotor gas turbine engine
is provided, the engine having a first rotor assembly and a second
rotor assembly, with a plurality of airfoil blades
circumferentially mounted on each rotor assembly and arranged in
contra-rotational relationship to each other. The pitch control
mechanism includes an actuator assembly configured to be secured to
a non-rotating frame of the engine, the actuator assembly having a
first actuator and a second actuator, with the actuator assembly
being rotationally isolatable from and couplable to the first and
second rotor assemblies such that, in use, an actuation signal from
the first or second actuator induces a corresponding desired change
in pitch of the airfoil blades of the respective first or second
rotor assembly independently of the pitch of the airfoil blades of
the second or first rotor assembly.
Inventors: |
Szymandera; Aleksander
Krzysztof; (Warsaw, PL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GE Aviation Systems Limited |
Cheltenham |
|
GB |
|
|
Family ID: |
44838786 |
Appl. No.: |
15/195429 |
Filed: |
June 28, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13588180 |
Aug 17, 2012 |
9376202 |
|
|
15195429 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02T 50/66 20130101;
F01D 1/26 20130101; F05D 2240/30 20130101; F05D 2260/40311
20130101; B64D 27/16 20130101; B64D 2027/005 20130101; F05D
2220/323 20130101; B64C 11/306 20130101; F02C 9/58 20130101; F02K
3/072 20130101; B64C 11/308 20130101; F02K 3/025 20130101; Y02T
50/60 20130101 |
International
Class: |
B64C 11/30 20060101
B64C011/30; B64D 27/16 20060101 B64D027/16; F02K 3/02 20060101
F02K003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 26, 2011 |
GB |
1114795.6 |
Claims
1-11. (canceled)
12. An actuator assembly, comprising: a first actuator coupled to a
first rotor assembly of a turbine engine, wherein the first rotor
assembly includes a first set of airfoil blades mounted
circumferentially on the first rotor assembly; a second actuator
coupled to a second rotor assembly of the turbine engine, wherein
the second rotor assembly includes a second set of airfoil blades
mounted circumferentially on the second rotor assembly, and the
second set of airfoil blades are arranged in contra-rotational
relationship with the first set of airfoil blades; wherein the
actuator assembly is configured to be secured to a non-rotating
frame of the turbine engine, rotationally isolated from the first
and second rotor assemblies, spatially decoupled from a gearbox
configured to transfer rotational drive to at least one of the
first or second rotor assemblies, and an actuation signal from the
first actuator induces a corresponding change in pitch of the first
set of airfoil blades independently of the pitch of the second set
of airfoil blades.
13. The actuator assembly of claim 12, wherein an actuation signal
from the second actuator induces a corresponding change in pitch of
the second set of airfoil blades independently of the pitch of the
first set of airfoil blades.
14. The actuator assembly of claim 13, wherein the first and second
actuators are concentrically mounted.
15. The actuator assembly of claim 12, wherein the actuator
assembly is rotationally isolated from the first and second rotor
assemblies via a set of bearing arrangements.
16. The actuator assembly of claim 15, wherein the first actuator
is coupled to the first rotor assembly via a first bearing
arrangement included in the set of bearing arrangements.
17. The actuator assembly of claim 16, wherein the first bearing
arrangement is configured to transmit a displacement signal of the
first actuator to the first rotor assembly, and is coupled to the
first set of airfoil blades, wherein the displacement signal is
converted to a rotational output signal to adjust the pitch of the
first set of airfoil blades.
18. The actuator assembly of claim 17, further comprising a pin and
roller arrangement for coupling the first bearing arrangement with
the first set of airfoil blades.
19. The actuator assembly of claim 18, wherein the first bearing
arrangement includes a bearing mounted relative to the first
actuator such that the displacement signal of the first actuator
acts upon an axial end face of the bearing to transmit a
corresponding axial load to an axially slideable annular yoke
rotatable with the respective first rotor assembly, the airfoil
blades of the first rotor assembly being mounted to a plurality of
radially extending shafts circumferentially disposed about the
yoke, the pin and roller arrangement includes: a combination of a
pin and a roller associated with at least one of the radially
extending shafts, wherein the roller is located in an annular
groove provided on a surface of the yoke, the roller is configured
to slide about the annular groove of the yoke under the action of
the transmitted axial load, and the roller is offset from a
longitudinal axis of the associated at least one radially extending
shafts, and wherein the pin connects each roller to the associated
at least one radially extending shafts such that sliding of the
roller about the annular groove of the yoke acts upon the pin to
twist the associated at least one radially extending shafts and
thereby adjust the pitch of the first set of airfoil blades.
20. The actuator assembly of claim 19, wherein each shaft of the
plurality of radially extending shafts is associated to a
respective combination of pin and roller.
21. The actuator assembly of claim 20, wherein the actuator
assembly is mounted along or parallel to a longitudinal axis of the
turbine engine.
22. The actuator assembly of claim 12, wherein the gearbox is an
epicyclic gearbox for transferring rotational drive to both of the
first and second rotor assemblies, the first and second rotor
assemblies being driven in opposing directions.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/588180, filed on Aug. 17, 2012, which is incorporated herein
by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] Embodiments of the subject matter disclosed herein relate to
a mechanism for enabling independent pitch control of airfoil
blades of contra-rotating rotor assemblies. The application is of
particular benefit when applied to "open rotor" gas turbine
engines.
[0003] Gas turbine engines employing an "open rotor" design
architecture are known. The open rotor design is essentially a
hybrid of conventional turbofan and turboprop gas turbine engines,
but providing enhanced fuel efficiency over both conventional
engine designs. A turbofan engine operates on the principle that a
central gas turbine core drives a bypass fan, the fan being located
at a radial location between a nacelle of the engine and the engine
core. An open rotor engine instead operates on the principle of
having the bypass fan located outside of the engine nacelle. This
permits the use of larger fan blades able to act upon a larger
volume of air than for a turbofan engine, and thereby helps to
generate more thrust than for conventional engine designs. Optimum
performance has been found with an open rotor design having a fan
provided by two contra-rotating rotor assemblies, each rotor
assembly carrying an array of airfoil blades located outside the
engine nacelle. In appearance, the fan blades of an open rotor
engine resemble the propeller blades of a conventional turboprop
engine.
[0004] The use of contra-rotating rotor assemblies provides
technical challenges in transmitting power from the turbine core to
drive the airfoil blades of the respective two rotor assemblies in
opposing directions.
[0005] EP1881176A2 (Rolls-Royce plc, 23 Jan. 2008) discloses an
engine conforming to an open rotor design architecture, the engine
having a mechanism for enabling independent pitch control of
respective airfoil blades of a first rotor assembly and a second
rotor assembly, where the first and second rotor assemblies are
driven in a contra-rotating manner about a longitudinal axis of the
engine.
[0006] Embodiments of the present invention seek to provide an
improved alternative to the engine arrangement disclosed in
EP1881176A2, and to provide improvements in efficiency over known
designs.
BRIEF DESCRIPTION OF THE INVENTION
[0007] According to an embodiment of the present invention, a pitch
control mechanism for an open rotor gas turbine engine is provided.
The engine includes a first rotor assembly and a second rotor
assembly, a plurality of airfoil blades circumferentially mounted
on each rotor assembly and arranged in contra-rotational
relationship to each other. The pitch control mechanism comprises
an actuator assembly configured to be secured to a non-rotating
frame of the engine, the actuator assembly comprising a first
actuator and a second actuator, wherein the actuator assembly is
rotationally isolatable from and couplable to the first and second
rotor assemblies such that, in use, an actuation signal from the
first or second actuator induces a corresponding desired change in
pitch of the airfoil blades of the respective first or second rotor
assembly independently of the pitch of the airfoil blades of the
second or first rotor assembly.
[0008] According to another embodiment of the present invention, a
turbine engine comprising a first rotor assembly and a second rotor
assembly is provided. The first and second rotor assemblies each
comprise a plurality of airfoil blades circumferentially mounted on
each rotor assembly and arranged in contra-rotational relationship
to each other, the pitch of the airfoil blades of the first rotor
assembly and of the second rotor assembly being independently
adjustable of each other. The engine further comprises an actuator
assembly secured to a non-rotating frame of the engine. The
actuator assembly comprising a first actuator and a second
actuator, wherein the actuator assembly is rotationally isolated
from and coupled to the first and second rotor assemblies such
that, in use, an actuation signal from the first or second actuator
induces a corresponding desired change in pitch of the airfoil
blades of the respective first or second rotor assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate one or more
embodiments and, together with the description, explain these
embodiments. In the drawings:
[0010] FIG. 1 shows a perspective view of an open rotor gas turbine
engine;
[0011] FIG. 2 shows a cross-sectional view of the engine of FIG. 1
incorporating a pitch control mechanism according to an embodiment
of the invention. This figure shows the general disposition of the
frames of a forward rotor assembly and an aft rotor assembly, and a
non-rotating frame of the engine;
[0012] FIG. 3 shows a detailed sectional view of the engine and
pitch control mechanism shown in FIG. 2;
[0013] FIG. 4 shows a detailed sectional view of the forward rotor
assembly of FIGS. 2 and 3;
[0014] FIG. 5 shows a detailed sectional view of the aft rotor
assembly of FIGS. 2 and 3;
[0015] FIG. 6 shows a detailed perspective view of the aft rotor
assembly shown in FIG. 5; and
[0016] FIG. 7 shows a detailed perspective view of both the forward
and aft rotor assemblies shown in FIGS. 4, 5 and 6.
DETAILED DESCRIPTION OF THE INVENTION
[0017] As used herein, "contra-rotational relationship" means that
the airfoil blades of the first and second rotor assemblies are
arranged to rotate in opposing directions to each other. It is
preferred that the airfoil blades of the first and second rotor
assemblies are arranged to rotate about a common axis in opposing
directions, and are axially spaced apart along that axis. For
example, the respective airfoil blades of the first rotor assembly
and second rotor assembly may be co-axially mounted and spaced
apart, with the blades of the first rotor assembly configured to
rotate clockwise about the axis and the blades of the second rotor
assembly configured to rotate counter-clockwise about the axis (or
vice versa).
[0018] By ensuring that the actuator assembly is adapted to be
secured to a non-rotating frame, embodiments of the present
invention avoid the need for oil transfer bearings that would
otherwise be needed if the actuator assembly were itself able to
rotate relative to the frame. This feature enhances the reliability
and minimizes the complexity of the lubrication system required for
the engine and reducing potential leak pathways for oil, because it
avoids the need for oil transfer bearings between the frame and the
actuator assembly. This feature also enables increased oil
pressures in the actuation assembly of the engine. Oil system
pressures of the order of around 3000 psi are potentially feasible
through applying embodiments of the present invention. This
pressure is much higher than for assemblies that rely upon the use
of oil transfer bearings. Further, this feature also allows for
simple implementation of a blade position sensor. The blade
position sensor can be located on the non-rotating frame (as part
of the actuator assembly) and thereby avoids the need to transfer
electric signals between rotating and non-rotating frames.
[0019] Rotational isolation and coupling of the actuator assembly
to each of the first and second rotor assemblies may be enabled by
use of one or more bearing arrangements. Conveniently, bearings are
chosen which are adapted to enable transfer of axial load. For
example, angular contact bearings are particularly suitable for
enabling efficient transfer of axial load.
[0020] The actuator assembly may be arranged such that the first
and second actuators are concentrically mounted. Such an
arrangement is known as a "double annular actuator". This
arrangement of actuator assembly minimizes the volume required for
the actuator assembly within a gas turbine engine--an environment
where efficient use of space is essential. The actuator assembly
may be a double annular actuator, with the first and second
actuators coaxially mounted along or parallel to the central axis
of the engine. The use of annular actuators reduces the number of
actuators required within the engine and has the potential to
enhance reliability and efficiency of the engine.
[0021] A first bearing arrangement may be associated with both of
the first actuator and first rotor assembly, with a second bearing
arrangement associated with both of the second actuator and second
rotor assembly. The bearing arrangements may be adapted such that a
displacement signal of the first or second actuator is
transmittable via the respective first or second bearing
arrangement to the respective first or second rotor assembly, the
first and second bearing arrangements each being couplable to the
airfoil blades of the respective first and second rotor assemblies
such that, in use, the transmitted displacement signal is converted
to a rotational output signal to thereby adjust the pitch of the
airfoil blades of the respective first or second rotor
assembly.
[0022] Conveniently, a first bearing is mounted relative to the
first actuator such that a displacement signal of the first
actuator acts upon an axial end face of the first bearing to
thereby transmit a corresponding axial load to a first axially
slideable annular yoke rotatable with the first rotor assembly, the
airfoil blades of the first rotor assembly mounted to a plurality
of radially extending shafts circumferentially disposed about the
first yoke. The first bearing may be coupled to the airfoil blades
of the first rotor assembly by means of a pin and roller
arrangement. In one such pin and roller arrangement, a combination
of a pin and a roller is associated with one or more of the
radially extending shafts on which the airfoil blades of the first
rotor assembly are mounted. Explaining further, the roller may be
located in an annular groove provided on a surface of the first
yoke, with the roller adapted to slide about the annular groove of
the first yoke under the action of the transmitted axial load. The
roller is offset from the longitudinal axis(es) of the associated
one or more of the radially extending shafts, with the pin
connecting each roller to the associated one or more of the
radially extending shafts. In use, the transmitted axial load
conveyed through the first bearing acts to induce an axial
displacement of the first yoke relative to the first rotor
assembly, thereby inducing the roller located therein to slide
about the annular groove, the sliding of the roller acting upon the
pin to twist the associated one or more of the radially extending
shafts about their longitudinal axis(es) to thereby produce the
desired change in pitch of the airfoil blades of the first rotor
assembly. Each of the radially extending shafts may be associated
with a respective combination of pin and roller.
[0023] A similar arrangement as outlined in the above paragraph may
also or alternatively be provided for the second rotor
assembly.
[0024] Contra-rotation of the airfoil blades of the first and
second rotor assemblies is enabled by use of an epicyclic gearbox
to transfer rotational drive to both of the first and second rotor
assemblies, the first and second rotor assemblies being driven in
opposing directions, the actuator assembly arranged to be spatially
decoupled from the epicyclic gearbox. Spatially decoupled means
that no part of the actuator assembly passes through the epicyclic
gearbox. The epicyclic gearbox may take the form of a conventional
planetary gearbox. In one embodiment of the invention, the
planetary gearbox comprises a sun gear driven by the engine, planet
gears associated with the first rotor assembly and a ring gear
associated with the second rotor assembly, with the planet gears
and ring gears enabling contra-rotation of the first and second
rotor assemblies. Spatial decoupling of the actuator assembly from
the epicyclic gearbox provides a potentially more reliable design
of actuator assembly/pitch control mechanism/engine than for the
known design described in EP1881176A2. The design of EP1881176A2
depends upon actuator rods of its actuator assembly for at least
one of its two rotor assemblies passing through an epicyclic
gearbox, either "through" or "between" planet gears (as stated in
paragraph 8 of EP1881176A2), and thereby increases both the
complexity of the design for this known design and the number of
potential failure modes.
[0025] FIG. 1 shows a perspective view of a typical open rotor gas
turbine engine 10 for which the pitch control mechanism of
embodiments of the present invention are particularly suitable. As
is seen from FIG. 1, the engine 10 has a forward rotor assembly 20
on which is mounted an array of airfoil blades 21 and an aft rotor
assembly 30 on which is mounted an array of airfoil blades 31. Both
the forward and aft airfoil blades 21, 31 are each mounted for
rotation about a central longitudinal axis 11 of the engine 10 in
contra-rotational directions--indicated by arrows .omega..sub.20
and .omega..sub.30 on FIG. 1.
[0026] The sectional view of FIG. 3 shows that the engine 10 has a
pitch control mechanism 40 having an actuator assembly 50. The
actuator assembly 50 is shown more clearly on FIG. 4 (bounded by a
dotted oval line). The actuator assembly is secured to a static
non-rotating frame 12 of the engine 10. The frame 12 is secured (by
means not shown) to the external casing or nacelle of the engine
10. FIG. 2 shows the general boundaries of the static non-rotating
frame 12, the forward rotor assembly 20 and the aft rotor assembly
30. The respective directions of rotation .omega..sub.20,
.omega..sub.30 are also marked up for the airfoil blades 21, 31 of
the forward and aft rotor assemblies 20, 30.
[0027] A planetary gearbox 60 is incorporated within the engine 10
to transfer rotational drive to both of the forward and aft rotor
assemblies 20, 30 (see FIG. 2). The component parts of the
planetary gearbox 60 are not shown in the figures.
[0028] The actuator assembly 50 is a double annular hydraulic
actuator having a forward actuator 51 and an aft actuator 52
concentrically mounted relative to each other and about the
longitudinal engine axis 11 (as more clearly shown in FIG. 4). The
forward actuator 51 is coupled to the forward rotor assembly 20,
with the aft actuator 52 coupled to the aft rotor assembly 30. The
construction of the forward actuator/rotor assembly and related
parts will be described separately from that of the aft
actuator/rotor assembly and related parts.
[0029] As shown in FIGS. 3 and 4, the forward actuator 51 has a
piston 511 capable of sliding to and fro parallel to engine axis
11. An annular flange 512 extends outwardly from the outer wall of
the piston 511. The flange 512 abuts against the inside race of a
transfer bearing 513, the bearing concentrically mounted about the
forward actuator 51. The outside race of the transfer bearing 513
is connected to a yoke 514, the yoke mounted to and rotatable with
the forward rotor assembly 20. As shown in FIGS. 4 and 7, the yoke
514 has an annular groove 515 provided in its radially outer facing
surface. The forward array of airfoil blades 21 are mounted to the
forward rotor assembly 20 as described in the following
paragraph.
[0030] As shown in FIGS. 4 and 7, a plurality of radially extending
shafts 22 are located about the forward rotor assembly 20, with a
single one of the airfoil blades 21 mounted to each shaft (by means
not shown). The shafts 22 are coupled to the yoke 514 by a pin and
roller arrangement 516 (shown most clearly in FIG. 7). The pin and
roller arrangement 516 has a cylindrical shaped roller 517 located
in the annular groove 515 of the yoke 514, with a pin 518 in turn
connecting the roller 517 to one of the radially extending shafts
22. Each of the shafts 22 is coupled to the yoke 514 by its own
combination of pin and roller.
[0031] In use, an actuation signal from the forward actuator 51 of
the actuator assembly 50 acts to axially displace piston 511
parallel to engine axis 11. In so doing, the annular flange 512 of
the piston 511 acts upon the inside race of the transfer bearing
513 with axial load F.sub.51 (see FIG. 4). By way of example only,
the axial load F.sub.51 may be of the order 75 klbf. The axial load
F.sub.51 is transferred to the yoke 514 via the outside race of the
transfer bearing 513 and thereby urges the yoke to slide parallel
to the engine axis 11. This axial sliding of the yoke 514 causes
each of the rollers 517 to circumferentially slide about the
annular groove 515 of the yoke 514, with the pin 518 in turn acting
to twist its respective radially extending shaft 22 about the
longitudinal axis 23 of the shaft (see FIG. 7), to thereby adjust
the pitch of the airfoil blade 21 mounted thereto.
[0032] In this manner, the forward actuator 51 is coupled to the
forward rotor assembly 20, resulting in the axial displacement and
the induced axial load F.sub.51 of the forward actuator 51 being
converted into a rotational output signal to adjust the pitch of
the blades 21 of the forward rotor assembly.
[0033] As shown in FIGS. 3, 4 and 5, the aft actuator 52 has a
piston 521 capable of sliding to and fro parallel to engine axis
11. An annular end face of the piston 521 abuts against the inside
race of a transfer bearing 522a, the bearing concentrically mounted
about the static non-rotating frame 12. Axially extending transfer
rods 523 extend between the outside race of transfer bearing 522a
and the inside race of a further transfer bearing 522b (see FIGS. 3
and 5). Spherical bearings 524 are incorporated at either end of
the transfer rods 523 at the interface with the transfer bearings
522a,b.
[0034] A yoke 525 is mounted about the outside race of the transfer
bearing 522b, the yoke rotatable with the aft rotor assembly 30. As
more clearly shown in FIG. 5, the yoke 525 has an annular groove
526 provided in its radially outer facing surface. The aft array of
airfoil blades 31 are mounted to the aft rotor assembly 30 as
described in the following paragraph.
[0035] A plurality of radially extending shafts 32 are located
about the aft rotor assembly 30, with a single one of the airfoil
blades 31 mounted to each shaft (by means not shown). The shafts 32
are coupled to the yoke 525 by a pin and roller arrangement 527
(shown most clearly in FIG. 6). The pin and roller arrangement 527
has a cylindrical shaped roller 528 located in the annular groove
526 of the yoke 525, with a pin 529 in turn connecting the roller
528 to one of the radially extending shafts 32. Each of the shafts
32 is coupled to the yoke 525 by its own combination of pin and
roller.
[0036] In use, an actuation signal from the aft actuator 52 of the
actuator assembly 50 acts to axially displace piston 521 along
engine axis 11. In so doing, the annular end face of the piston 521
acts upon the inside race of the transfer bearing 522a with axial
load F.sub.52 (see FIGS. 3 and 5). By way of example only, the
axial load F.sub.52 may be of the order 55 klbf. The axial load
F.sub.52 is transmitted from the outside race of the transfer
bearing 522a, via the axially extending transfer rods 523, to the
outside race of the transfer bearing 522b and thereby to the yoke
525. The axial load F.sub.52 thereby urges the transfer bearing
522b and the yoke 525 to slide parallel to the engine axis 11. This
axial sliding of the yoke 525 causes each of the rollers 528 to
circumferentially slide about the annular groove 526 of the yoke
525, with the pin 529 in turn acting to twist its respective
radially extending shaft 32 about the longitudinal axis 33 of the
shaft (see FIGS. 6 and 7), to thereby adjust the pitch of the
airfoil blade 31 mounted thereto.
[0037] In this manner, the aft actuator 52 is coupled to the aft
rotor assembly 30, resulting in the axial displacement and the
induced axial load F.sub.52 of the aft actuator 52 being converted
into a rotational output signal to adjust the pitch of the blades
31 of the forward rotor assembly.
[0038] The transfer bearings 513 and 522a,b ensure that each of the
first and second actuators 51, 52 are rotationally isolated from
but coupled to the first and second rotor assemblies 20, 30
respectively. In one embodiment, the transfer bearings may be
angular contact bearings because these are particularly good at
transferring axial loads. However, other known bearing types may be
used which are suitable for enabling the transfer of axial
load.
[0039] For the pin and roller arrangement outlined above, the
amount by which the pitch of the airfoil blades 21, 31 is adjusted
will be dependent upon the magnitude of the axial displacement of
the respective actuator 51, 52.
[0040] For the engine 10 shown in the figures and described above,
the actuator assembly 50 is arranged to be spatially decoupled from
the planetary gearbox 60.
[0041] The foregoing description of the embodiments of the
invention is provided for illustrative purposes only and is not
intended to limit the scope of the invention as defined in the
appended claims.
* * * * *