U.S. patent application number 16/035340 was filed with the patent office on 2020-01-16 for fan clutch for convertible engine.
This patent application is currently assigned to Bell Helicopter Textron Inc.. The applicant listed for this patent is Bell Helicopter Textron Inc.. Invention is credited to Thomas Dewey Parsons, Troy Cyril Schank, Alan Hisashi Steinert.
Application Number | 20200017229 16/035340 |
Document ID | / |
Family ID | 69139947 |
Filed Date | 2020-01-16 |
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United States Patent
Application |
20200017229 |
Kind Code |
A1 |
Steinert; Alan Hisashi ; et
al. |
January 16, 2020 |
FAN CLUTCH FOR CONVERTIBLE ENGINE
Abstract
Systems and methods include providing an aircraft with a
fuselage and a convertible engine disposed within the fuselage. The
convertible engine is operable as a turbofan engine in a thrust
mode and a turboshaft engine in a shaft power mode. The convertible
engine includes a housing, an engine core having a low pressure
turbine shaft, and a bypass fan system. The bypass fan system
includes a bypass fan having a fan clutch. The fan clutch
selectively couples at least a portion of the bypass fan to the low
pressure turbine shaft when the convertible engine is operated in
the thrust mode and decouples at least a portion of the bypass fan
from the low pressure turbine shaft when the convertible engine is
operated in the shaft power mode.
Inventors: |
Steinert; Alan Hisashi;
(Fort Worth, TX) ; Parsons; Thomas Dewey; (Fort
Worth, TX) ; Schank; Troy Cyril; (Keller,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bell Helicopter Textron Inc. |
Fort Worth |
TX |
US |
|
|
Assignee: |
Bell Helicopter Textron
Inc.
Fort Worth
TX
|
Family ID: |
69139947 |
Appl. No.: |
16/035340 |
Filed: |
July 13, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B64C 29/0033 20130101;
F02K 3/06 20130101; F02C 6/206 20130101; F05D 2220/323 20130101;
F05D 2240/12 20130101; F02C 7/36 20130101; F02K 3/075 20130101;
F04D 25/166 20130101; F05D 2260/407 20130101; B64D 27/20 20130101;
F05D 2260/408 20130101; B64D 35/02 20130101; F05D 2220/325
20130101 |
International
Class: |
B64D 35/02 20060101
B64D035/02; B64D 27/20 20060101 B64D027/20; F02C 7/36 20060101
F02C007/36; F02K 3/06 20060101 F02K003/06; F02K 3/075 20060101
F02K003/075; F04D 25/16 20060101 F04D025/16 |
Claims
1. A convertible engine for an aircraft, comprising: an engine core
comprising a low pressure turbine shaft; and a bypass fan system
comprising: a bypass fan comprising a fan clutch, wherein the fan
clutch is configured to selectively decouple at least a portion of
the bypass fan from the low pressure turbine shaft.
2. The convertible engine of claim 1, wherein the fan clutch is at
least one of an electromechanical clutch and a piezoelectric
clutch.
3. The convertible engine of claim 1, wherein the fan clutch is a
magnetorheological clutch comprising a magnetorheological
fluid.
4. The convertible engine of claim 3, wherein electromagnets are
disposed in at least one non-rotating, fixed reference component of
the convertible engine and in close proximity to the fan clutch,
and wherein the electromagnets are configured to selectively induce
a magnetic field through the magnetorheological fluid in the fan
clutch to couple the at least a portion of the bypass fan to the
low pressure turbine shaft.
5. The convertible engine of claim 1, wherein the bypass fan is
coupled to the low pressure turbine shaft when the convertible
engine is operated in a thrust mode, and wherein the bypass fan is
decoupled from the low pressure turbine shaft when the convertible
engine is operated in a shaft power mode.
6. The convertible engine of claim 5, further comprising: inlet
guide vanes selectively operable to restrict bypass airflow through
the convertible engine when the bypass fan is decoupled from the
low pressure turbine shaft.
7. The convertible engine of claim 1, wherein the bypass fan
comprises an inner fan and an outer fan, wherein the inner fan is
rigidly coupled to the low pressure turbine shaft, and wherein the
fan clutch is disposed between the inner fan and the outer fan and
configured to selectively couple the outer fan to the inner
fan.
8. The convertible engine of claim 7, wherein the outer fan is free
to spin concentrically about the inner fan and does not generate
bypass airflow to produce thrust when the outer fan is decoupled
from the inner fan.
9. The convertible engine of claim 8, further comprising: inlet
guide vanes selectively operable to restrict bypass airflow through
the convertible engine when the outer fan is decoupled from the
inner fan.
10. The convertible engine of claim 9, wherein the outer fan is
coupled to the inner fan via the fan clutch when the convertible
engine is operated in a thrust mode, and wherein the outer fan is
decoupled from the inner fan when the convertible engine is
operated in a shaft power mode.
11. The convertible engine of claim 10, wherein the low pressure
turbine shaft is selectively coupled to a gearbox through a
selectively operable gearbox clutch to cause selective rotation of
a rotor system when the convertible engine is operated in the shaft
power mode.
12. An aircraft, comprising: a fuselage; and a convertible engine
disposed within the fuselage and operable as a turbofan engine in a
thrust mode and a turboshaft engine in a shaft power mode, the
convertible engine comprising: an engine core comprising a low
pressure turbine shaft; and a bypass fan system comprising: a
bypass fan comprising a fan clutch, wherein the fan clutch is
configured to selectively couple at least a portion of the bypass
fan to the low pressure turbine shaft when the convertible engine
is operated in the thrust mode, and wherein the fan clutch is
configured to decouple the at least a portion of the bypass fan
from the low pressure turbine shaft when the convertible engine is
operated in the shaft power mode.
13. The aircraft of claim 12, wherein the fan clutch is at least
one of an electromechanical clutch, a piezoelectric clutch, and a
magnetorheological clutch.
14. The aircraft of claim 12, wherein the bypass fan comprises an
inner fan and an outer fan, wherein the inner fan is rigidly
coupled to the low pressure turbine shaft, and wherein the fan
clutch is disposed between the inner fan and the outer fan and
configured to selectively couple the outer fan to the inner
fan.
15. The aircraft of claim 12, wherein the low pressure turbine
shaft is configured to provide shaft power to at least one aircraft
system when the convertible engine is operated in the shaft power
mode.
16. The aircraft of claim 15, further comprising: at least one
additional mechanical locking component used to form a rigid
mechanical connection between the bypass fan and the low pressure
turbine shaft when the fan clutch selectively couples the at least
a portion of the bypass fan to the low pressure turbine shaft when
the convertible engine is operated in the thrust mode.
17. The aircraft of claim 15, wherein the low pressure turbine
shaft is selectively coupled to a gearbox through a selectively
operable gearbox clutch to cause selective rotation of a rotor
system when the convertible engine is operated in the shaft power
mode.
18. A method of operating an aircraft, comprising: providing an
aircraft engine comprising: an engine core comprising a low
pressure turbine shaft; and a bypass fan system comprising a bypass
fan having a fan clutch; operating the aircraft engine to generate
bypass airflow in order to induce thrust by selectively coupling at
least a portion of the bypass fan to the low pressure turbine
shaft; selectively decoupling at least a portion of the bypass fan
from the low pressure turbine shaft; and operating the aircraft
engine to provide shaft power to an aircraft system via the low
pressure turbine shaft without generating bypass airflow that
induces thrust.
19. The method of claim 18, wherein the selectively coupling at
least a portion of the bypass fan from the low pressure turbine
shaft is accomplished by passing an electrical current through a
plurality of electromagnets to produce a magnetic field proximate
to the fan clutch.
20. The method of claim 19, wherein the selectively decoupling at
least a portion of the bypass fan from the low pressure turbine
shaft is accomplished by interrupting the electrical current
through a plurality of electromagnets.
21. The method of claim 18, wherein the low pressure turbine shaft
is selectively coupled to a rotor system of the aircraft, and
wherein the shaft power from the low pressure turbine shaft is used
to cause rotation of the rotor system.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND
[0003] Convertible engines offer the possibility to provide both
thrust and mechanical shaft power in new, multi-mode aircraft
configurations and in conventional aircraft configurations that
require mechanical shaft power in cruise conditions to power
generators, charge weapons systems, or the like. These convertible
engines are operable as a turbofan engine to produce thrust and a
turboshaft engine to produce mechanical shaft power when thrust is
not required. Such convertible engines utilize a bypass fan
positioned in front of the engine core and rigidly connected to a
power output shaft. During operation as a turbofan engine, the
bypass fan produces a bypass airflow to provide thrust to the
aircraft. During operation as a turboshaft engine, the bypass
airflow produced by the bypass fan is blocked, allowing other
aircraft systems to utilize the power produced by the convertible
engine via the power output shaft. However, the bypass fan always
rotates with operation of the convertible engine, even when bypass
airflow used to produced thrust is not required. This results in
significant parasitic power loss caused by the drag of the rotating
bypass fan. Additional power or performance losses may also result
from the increased size of filtration system components and
increased pressure drop through such filtration components.
Further, bypass airflow increases residual thrust levels which must
be compensated for by other aircraft systems (e.g., main rotor)
which further drives additional power or performance losses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a cross-sectional side view of an aircraft engine
according to this disclosure.
[0005] FIG. 2 is a cross-sectional side view of another embodiment
of an aircraft engine according to this disclosure.
[0006] FIG. 3 is a front view of a bypass fan of the aircraft
engine of FIG. 2.
[0007] FIG. 4 is a simplified diagram of an aircraft according to
this disclosure.
[0008] FIG. 5 is a flowchart of a method of operating an aircraft
according to this disclosure.
DETAILED DESCRIPTION
[0009] In this disclosure, reference may be made to the spatial
relationships between various components and to the spatial
orientation of various aspects of components as the devices are
depicted in the attached drawings. However, as will be recognized
by those skilled in the art after a complete reading of this
disclosure, the devices, members, apparatuses, etc. described
herein may be positioned in any desired orientation. Thus, the use
of terms such as "above," "below," "upper," "lower," or other like
terms to describe a spatial relationship between various components
or to describe the spatial orientation of aspects of such
components should be understood to describe a relative relationship
between the components or a spatial orientation of aspects of such
components, respectively, as the device described herein may be
oriented in any desired direction.
[0010] Referring to FIG. 1, a cross-sectional side view of an
aircraft engine 100 is shown. Aircraft engine 100 generally
comprises a convertible engine that is operable as a turbofan
engine in a thrust mode and a turboshaft engine in a shaft power
mode. Aircraft engine 100 comprises a housing 102, an engine core
104, and a bypass fan 126. The engine core 104 comprises an engine
core housing 106, a compressor 108, a burner 110, a high pressure
turbine 112, a low pressure turbine 114, and a low pressure turbine
shaft 116. The low pressure turbine shaft 116 extends beyond a
front portion of the housing 102 and is generally connected to
another component for transferring power to the component. In the
embodiment shown, the low pressure turbine shaft 116 is selectively
coupled to and decoupled from a gearbox 160 through a selectively
operable gearbox clutch 150 in order to cause selective rotation of
a rotor system 170. The aircraft engine 100 also comprises a
plurality of inlet guide vanes 118 configured to regulate bypass
airflow 120 through the aircraft engine 100. Additionally, the
aircraft engine 100 comprises a core stator 122 through which the
core airflow 124 passes through prior to entering the compressor
108 of the engine core 104. The inlet guide vanes 118 and core
stator 122 are fixed reference components that do not rotate with
respect to the housing 102 of the aircraft engine 100.
[0011] Aircraft engine 100 further comprises a bypass fan system
125 comprising a bypass fan 126 and a plurality of electromagnets
132. Bypass fan 126 is positioned in front of the engine core 104
and behind the fixed reference components of the inlet guide vanes
118 and core stator 122. Bypass fan 126 is also concentric with the
low pressure turbine shaft 116. Bypass fan 126 comprises a
plurality of fan blades 128 and a fan clutch 130 and is configured
to generate the bypass airflow 120 through the aircraft engine 100
in order to produce thrust. The fan clutch 130 is configured to
selectively couple and decouple the bypass fan 126 to and from the
low pressure turbine shaft 116. In the embodiment shown, the fan
clutch 130 comprises a magnetorheological clutch. As such, the fan
clutch 130 carries a magnetorheological fluid 131. Electromagnets
132 are disposed within at least one non-rotating, fixed reference
component and in close proximity to the fan clutch 130.
Electromagnets 132 are configured to selectively induce a magnetic
field through the magnetorheological fluid 131 in the fan clutch
130 to couple and decouple the bypass fan 126 to and from the low
pressure turbine shaft 116. In some embodiments, the electromagnets
132 may be located in front of the bypass fan 126 and disposed
within the core stator 122. However, in other embodiments, the
electromagnets 132 may be located behind the bypass fan 126 and
disposed within a portion of the engine core housing 106 that
houses the compressor 108. While in the embodiment shown, the
bypass fan system 125 comprises a plurality of electromagnets 132,
some embodiments of the bypass fan system 125 may only comprise one
electromagnet 132 disposed within one of the non-rotating, fixed
reference components and in close proximity to the fan clutch 130.
Further, in some embodiments, the fan clutch 130 may comprise a
friction-type electromechanical clutch or a piezoelectric clutch
and may not comprise electromagnets 132.
[0012] In operation, the aircraft engine 100 generally comprises a
convertible engine that is operable as a turbofan engine in a
thrust mode and a turboshaft engine in a shaft power mode. When
thrust is required from the aircraft engine 100, the aircraft
engine 100 may be configured to operate as a turbofan engine in the
thrust mode. In the thrust mode, the bypass fan 126 is coupled to
the rotating low pressure turbine shaft 116 via the fan clutch 130
in order for the bypass fan 126 to rotate with the low pressure
turbine shaft 116 and generate bypass airflow 120 that induces
thrust. Additionally, the gearbox 160 may be selectively decoupled
from the low pressure turbine shaft 116 via the gearbox clutch 150.
To couple the bypass fan 126 to the low pressure turbine shaft 116,
electrical current is passed through the electromagnets 132,
thereby producing a magnetic field proximate to the fan clutch 130.
When the fan clutch 130 is subjected to the magnetic field, the
magnetorheological fluid 131 in the fan clutch 130 increases its
apparent viscosity, to the point of becoming a viscoelastic solid,
thereby rigidly coupling the bypass fan 126 to the low pressure
turbine shaft 116. When the magnetic field is present and the
bypass fan 126 is coupled to the low pressure turbine shaft 116,
additional mechanical locking components or mechanisms (e.g.,
splines) may be used between the bypass fan 226 and the low
pressure turbine shaft 116 to further enhance the rigid mechanical
connection.
[0013] When thrust is not required from the aircraft engine 100,
the aircraft engine 100 may be configured to operate as a
turboshaft engine in a shaft power mode to provide shaft power to a
gearbox 160. In the shaft power mode, the bypass fan 126 is
decoupled from the rotating low pressure turbine shaft 116 via the
fan clutch 130. Additionally, the gearbox 160 may be selectively
coupled to the low pressure turbine shaft 116 via the gearbox
clutch 150 to use the shaft power produced by the aircraft engine
100 in the shaft power mode to cause selective rotation of rotor
system 170. To decouple the bypass fan 126 from the low pressure
turbine shaft 116, the electrical current passing through the
electromagnets 132 is discontinued or interrupted, thereby removing
the magnetic field. When the magnetic field is removed from the fan
clutch 130, the magnetorheological fluid 131 in the fan clutch 130
decreases its apparent viscosity, returning to a viscous liquid,
and thereby decoupling the bypass fan 126 from the low pressure
turbine shaft 116. When the bypass fan 126 is decoupled from the
low pressure turbine shaft 116, the bypass fan 126 is free to spin
about the low pressure turbine shaft 116 and does not absorb power,
provide drag, or generate bypass airflow 120 to induce thrust. As
such, in the shaft power mode, additional shaft power is available
for transfer to the gearbox 160 through the low pressure turbine
shaft 116.
[0014] The amount of bypass fan power that can be converted to
mechanical shaft power is referred to as turn down ratio.
Traditional rigidly fixed bypass fans have turn down ratios between
50% and 75%, rendering 25% to 50% of the engine power unusable.
However, by decoupling bypass fan 126 from the low pressure turbine
shaft 116 in the shaft power mode, aircraft engine 100 can achieve
much a higher turn down ratio. Further, when the fan clutch 130 is
not subjected to the magnetic field, some residual coupling
viscosity in the magnetorheological fluid 131 may tend to heat the
fluid 131. However, the fan clutch 130 may be designed and
positioned such that core airflow 124 through the compressor 108
may cool the fluid 131 in the fan clutch 130 to prevent
temperature-induced degradation of the fluid 131. Still further,
the inlet guide vanes 118 may be closed to restrict bypass airflow
120 through the aircraft engine 100 to further reduce residual
thrust, control turn down ratio, and increase shaft power.
[0015] Referring to FIGS. 2 and 3, a cross-sectional side view of
another embodiment of an aircraft engine 200 and a front view of a
bypass fan 226 of the aircraft engine 200 are shown. Aircraft
engine 200 is substantially similar to and configured to operate in
a substantially similar manner to aircraft engine 100. However,
aircraft engine 200 comprises bypass fan system 225. Bypass fan
system 225 comprises a bypass fan 226 and a plurality of
electromagnets 238. Bypass fan 226 is positioned in front of the
engine core 104 and behind the fixed reference components of the
inlet guide vanes 118 and core stator 122. Bypass fan 226 is also
concentric with the low pressure turbine shaft 116. Bypass fan 226
comprises an inner fan 228 (compression portion) comprising a
plurality of fan blades 230, an outer fan 232 (bypass portion)
comprising a plurality of fan blades 234 and disposed
concentrically about the inner fan 228, and a fan clutch 236
forming a clutch ring disposed between the inner fan 228 and the
outer fan 232. While not shown, a bearing or plurality of bearings
may be disposed between the inner fan 228 and outer fan 232 to
effectuate smooth and/or free rotation of the outer fan 232 with
respect to the inner fan 228.
[0016] The inner fan 228 is rigidly coupled to the low pressure
turbine shaft 116 and rotates with the low pressure turbine shaft
116, while the outer fan 232 may generally rotate freely with
respect to the inner fan 228 and the low pressure turbine shaft
116. However, the fan clutch 236 is configured to selectively
couple and decouple the outer fan 232 to and from the inner fan
228. In the embodiment shown, the fan clutch 236 comprises a
magnetorheological clutch. As such, the fan clutch 236 carries a
magnetorheological fluid 237. Electromagnets 238 are disposed
within at least one non-rotating, fixed reference component and in
close proximity to the fan clutch 236 and configured to selectively
induce a magnetic field through the magnetorheological fluid 237 in
the fan clutch 236 to couple and decouple the outer fan 232 to and
from the inner fan 228 and consequently the low pressure turbine
shaft 116. In some embodiments, the electromagnets 238 may be
located in front of the bypass fan 226 and disposed within the core
stator 122 or an outer ring of the core stator 122. However, in
other embodiments, the electromagnets 238 may be located behind the
bypass fan 226 and disposed within a portion of the engine core
housing 106 that houses the compressor 108. While in the embodiment
shown, the bypass fan system 225 comprises a plurality of
electromagnets 238, some embodiments of the bypass fan system 225
may only comprise one electromagnet 238 disposed within one of the
non-rotating, fixed reference components and in close proximity to
the fan clutch 236. Further, in some embodiments, the fan clutch
236 may comprise a friction-type electromechanical clutch or a
piezoelectric clutch and may not comprise electromagnets 238.
[0017] In operation, the aircraft engine 200 generally comprises a
convertible engine that is operable as a turbofan engine in a
thrust mode and a turboshaft engine in a shaft power mode. When
thrust is required from the aircraft engine 200, the aircraft
engine 200 may be configured to operate as a turbofan engine in the
thrust mode. In the thrust mode, the outer fan 232 is coupled to
the inner fan 228 and consequently the rotating low pressure
turbine shaft 116 via the fan clutch 236 in order for the outer fan
232 to rotate with the low pressure turbine shaft 116 and generate
bypass airflow 120 that induces thrust. Additionally, the gearbox
160 may be selectively decoupled from the low pressure turbine
shaft 116 via the gearbox clutch 150. To couple the outer fan 232
to the inner fan 228 rotating with the low pressure turbine shaft
116, electrical current is passed through the electromagnets 238,
thereby producing a magnetic field proximate to the fan clutch 236.
When the fan clutch 236 is subjected to the magnetic field, the
magnetorheological fluid 237 in the fan clutch 236 increases its
apparent viscosity, to the point of becoming a viscoelastic solid,
thereby rigidly coupling the outer fan 232 to the inner fan 228 and
consequently the low pressure turbine shaft 116. When the magnetic
field is present and the outer fan 232 is coupled to the inner fan
228, additional mechanical locking components or mechanisms (e.g.,
splines) may be used between the inner fan 228 and outer fan 232 to
further enhance the rigid mechanical connection.
[0018] When thrust is not required from the aircraft engine 200,
the aircraft engine 200 may be configured to operate as a
turboshaft engine in a shaft power mode to provide shaft power to a
gearbox 160. In the shaft power mode, the outer fan 232 is
decoupled from the rotating inner fan 228 via the fan clutch 236.
Additionally, the gearbox 160 may be selectively coupled to the low
pressure turbine shaft 116 via the gearbox clutch 150 to use the
shaft power produced by the aircraft engine 200 in the shaft power
mode to cause selective rotation of rotor system 170. To decouple
the outer fan 232 from the inner fan 228, the electrical current
passing through the electromagnets 238 is discontinued or
interrupted, thereby removing the magnetic field. When the magnetic
field is removed from the fan clutch 236, the magnetorheological
fluid 237 in the fan clutch 236 decreases its apparent viscosity,
returning to a viscous liquid, and thereby decoupling the outer fan
232 from the inner fan 228 and consequently the low pressure
turbine shaft 116. When the outer fan 232 is decoupled from the
inner fan 228, the outer fan 232 is free to spin concentrically
about the inner fan 228 and the low pressure turbine shaft 116 and
does not absorb power, provide drag, or generate bypass airflow 120
to induce thrust. However, the inner fan 228 still rotates with the
low pressure turbine shaft 116 in the shaft power mode in order to
turbocharge the engine core 104 by increasing and/or pressurizing
the core airflow 124, thereby increasing the shaft power output. As
such, in the shaft power mode, additional shaft power is available
for transfer to the gearbox 160 through the low pressure turbine
shaft 116.
[0019] The amount of bypass fan power that can be converted to
mechanical shaft power is referred to as turn down ratio.
Traditional rigidly fixed bypass fans have turn down ratios between
50% and 75%, rendering 25% to 50% of the engine power unusable.
However, by decoupling the outer fan 232 of the bypass fan 226 from
the inner fan 228 and the low pressure turbine shaft 116 in the
shaft power mode, aircraft engine 200 can achieve much a higher
turn down ratio that may exceed 95%, thereby rendering only 5% of
the power produced by the aircraft engine 200 unusable. Further,
when the fan clutch 236 is not subjected to the magnetic field,
some residual coupling viscosity in the magnetorheological fluid
237 may tend to heat the fluid 237. However, the fan clutch 236 may
be designed and positioned such that core airflow 124 through the
compressor 108 may cool the fluid 237 in the fan clutch 236 to
prevent temperature-induced degradation of the fluid 237. Still
further, the inlet guide vanes 118 may be closed to restrict bypass
airflow 120 through the aircraft engine 200 to further reduce
residual thrust, control turn down ratio, and increase shaft
power.
[0020] Referring to FIG. 4, a simplified diagram of an aircraft 300
is shown. Aircraft 300 generally comprises a fuselage 302 and at
least one aircraft engine 100, 200. However, in some embodiments,
aircraft 300 may comprise one or more aircraft engines 100, 200.
The at least one aircraft engine 100, 200 may generally be disposed
within the fuselage 302 or attached to the fuselage 302.
Additionally, aircraft 300 may comprise one or more gearboxes 160
having a gearbox clutch 150 and/or one or more rotor systems 170.
Further, multiple aircraft engines 100, 200 may be coupled to a
single gearbox 160. In the embodiment shown, aircraft 300 comprises
a tiltrotor. However, in other embodiments, aircraft engines 100,
200 may be used in any other aircraft (e.g. fixed-wing aircraft,
helicopter, other vertical takeoff and landing (VTOL) aircraft,
etc.). This is applicable to both "manned" and "un-manned"
aircraft. Furthermore, it will be appreciated that bypass fan
systems 125, 225 may be retrofit with existing aircraft engines
and/or aircraft.
[0021] Referring to FIG. 5, a flowchart of a method 400 of
operating an aircraft is shown. Method 400 begins at block 402 by
providing an aircraft engine 100, 200 comprising: an engine core
104 comprising a low pressure turbine shaft 116; and a bypass fan
system 125, 225 comprising a bypass fan 126, 226 having a fan
clutch 130, 236. Method 400 continues at block 404 by operating the
aircraft engine 100, 200 to generate bypass airflow 120 in order to
induce thrust. Thrust may be used to propel an aircraft 300 in
forward flight. In some embodiments, bypass airflow 120 may be
generated by selectively coupling the bypass fan 126 to the low
pressure turbine shaft 116. This may be accomplished by passing an
electrical current through electromagnets 132 to produce a magnetic
field proximate to the fan clutch 130. In other embodiments, bypass
airflow 120 may be generated by selectively coupling an outer fan
232 of the bypass fan 226 to an inner fan 228 of the bypass fan
226. This may be accomplished by passing an electrical current
through electromagnets 238 to produce a magnetic field proximate to
the fan clutch 236. Method 400 continues at block 406 by
selectively disengaging at least a portion of the bypass fan 126,
226 from the low pressure turbine shaft 116. In some embodiments,
this may be accomplished by discontinuing or interrupting the
electrical current through the electromagnets 132 to decouple the
bypass fan 126 from the low pressure turbine shaft 116. In other
embodiments, this may be accomplished by discontinuing or
interrupting the electrical current through the electromagnets 238
to decouple the outer fan 232 from the inner fan 228 and
consequently the low pressure turbine shaft 116. Method 400 may
conclude at block 408 by operating the aircraft engine 100, 200 to
provide shaft power to an aircraft system via the low pressure
turbine shaft 116. In some embodiments, the shaft power from the
low pressure turbine shaft 116 may cause selective rotation of a
rotor system 170 of an aircraft 300. However, in other embodiments,
the aircraft engine 100, 200 may operate as an auxiliary power unit
(APU) to provide power to aircraft systems of an aircraft 300.
[0022] At least one embodiment is disclosed, and variations,
combinations, and/or modifications of the embodiment(s) and/or
features of the embodiment(s) made by a person having ordinary
skill in the art are within the scope of this disclosure.
Alternative embodiments that result from combining, integrating,
and/or omitting features of the embodiment(s) are also within the
scope of this disclosure. Where numerical ranges or limitations are
expressly stated, such express ranges or limitations should be
understood to include iterative ranges or limitations of like
magnitude falling within the expressly stated ranges or limitations
(e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater
than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a
numerical range with a lower limit, R.sub.l, and an upper limit,
R.sub.u, is disclosed, any number falling within the range is
specifically disclosed. In particular, the following numbers within
the range are specifically disclosed:
R=R.sub.l+k*(R.sub.u-R.sub.l), wherein k is a variable ranging from
1 percent to 100 percent with a 1 percent increment, i.e., k is 1
percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . 50
percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 95
percent, 98 percent, 99 percent, or 100 percent. Moreover, any
numerical range defined by two R numbers as defined in the above is
also specifically disclosed.
[0023] Use of the term "optionally" with respect to any element of
a claim means that the element is required, or alternatively, the
element is not required, both alternatives being within the scope
of the claim. Use of broader terms such as comprises, includes, and
having should be understood to provide support for narrower terms
such as consisting of, consisting essentially of, and comprised
substantially of. Accordingly, the scope of protection is not
limited by the description set out above but is defined by the
claims that follow, that scope including all equivalents of the
subject matter of the claims. Each and every claim is incorporated
as further disclosure into the specification and the claims are
embodiment(s) of the present invention. Also, the phrases "at least
one of A, B, and C" and "A and/or B and/or C" should each be
interpreted to include only A, only B, only C, or any combination
of A, B, and C.
* * * * *