U.S. patent application number 15/345959 was filed with the patent office on 2017-02-23 for gas turbine engine with fan variable area nozzle for low fan pressure ratio.
The applicant listed for this patent is United Technologies Corporation. Invention is credited to Gregory A. Kohlenberg, Frederick M. Schwarz, Sean P. Zamora.
Application Number | 20170051630 15/345959 |
Document ID | / |
Family ID | 48570757 |
Filed Date | 2017-02-23 |
United States Patent
Application |
20170051630 |
Kind Code |
A1 |
Kohlenberg; Gregory A. ; et
al. |
February 23, 2017 |
GAS TURBINE ENGINE WITH FAN VARIABLE AREA NOZZLE FOR LOW FAN
PRESSURE RATIO
Abstract
A gas turbine engine includes a core nacelle defined about an
engine centerline axis. A core engine is at least partially
disposed within the core nacelle. The core engine includes a first
turbine section driving a first compressor section and a second
turbine section driving a second compressor section. A fan section
with a plurality of fan blades. A gear system is driven through a
shaft coupled to the first turbine section. The gear system
provides a speed reduction between the first turbine section and
the fan section of greater than 2.3. A fan nacelle is mounted at
least partially around said fan section and the core nacelle to
define a fan bypass flow path for a fan bypass airflow. The fan
bypass airflow has a fan pressure ratio of the fan bypass airflow
during engine operation less than 1.45. A variable area fan nozzle
is disposed at a trailing edge of the fan nacelle. The variable
area fan nozzle includes a first nacelle section and a second
nacelle section. The second nacelle section is movable relative to
the first nacelle section to vary an exit area at the trailing edge
of the fan nacelle to maintain the fan pressure ratio during engine
operation.
Inventors: |
Kohlenberg; Gregory A.;
(Kensington, CT) ; Zamora; Sean P.; (Coventry,
CT) ; Schwarz; Frederick M.; (Glastonbury,
CT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
United Technologies Corporation |
Farmington |
CT |
US |
|
|
Family ID: |
48570757 |
Appl. No.: |
15/345959 |
Filed: |
November 8, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13340810 |
Dec 30, 2011 |
9494084 |
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15345959 |
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13314365 |
Dec 8, 2011 |
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13340810 |
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|
11843675 |
Aug 23, 2007 |
8074440 |
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13314365 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F05D 2270/3015 20130101;
F02C 7/36 20130101; F04D 29/522 20130101; F01D 25/24 20130101; F02K
3/06 20130101; F01D 5/02 20130101; F05D 2240/128 20130101; F05D
2220/32 20130101; F02C 9/20 20130101; B64D 33/04 20130101; F02C
3/04 20130101; F02K 1/30 20130101; F01D 17/14 20130101; F01D 15/12
20130101; F02C 9/18 20130101; F02K 1/72 20130101 |
International
Class: |
F01D 17/14 20060101
F01D017/14; F02C 3/04 20060101 F02C003/04; F02K 1/72 20060101
F02K001/72; F02C 7/36 20060101 F02C007/36; F04D 29/52 20060101
F04D029/52; F02C 9/18 20060101 F02C009/18; F01D 25/24 20060101
F01D025/24; F02K 3/06 20060101 F02K003/06 |
Claims
1. A gas turbine engine comprising: a core nacelle defined about an
engine centerline axis; a core engine at least partially disposed
within the core nacelle, the core engine including a first turbine
section driving a first compressor section and a second turbine
section driving a second compressor section; a fan section with a
plurality of fan blades; a gear system driven through a shaft
coupled to the first turbine section, the gear system providing a
speed reduction between the first turbine section and the fan
section of greater than 2.3; a fan nacelle mounted at least
partially around said fan section and the core nacelle to define a
fan bypass flow path for a fan bypass airflow, the fan bypass
airflow having a fan pressure ratio of the fan bypass airflow
during engine operation less than 1.45; and a variable area fan
bypass duct opening, the variable area fan bypass duct opening
including a first nacelle section and a second nacelle section, the
second nacelle section movable relative to the first nacelle
section to vary an exit area from the fan stream to selectively
lower the fan pressure ratio during engine operation.
2. The engine as recited in claim 1, further comprising a
controller operable to reduce said fan nozzle exit area at a cruise
flight condition.
3. The engine as recited in claim 2, wherein said controller is
operable to control said fan nozzle exit area to reduce a fan
instability.
4. The engine as recited in claim 2, wherein said second nacelle
section is movable axially substantially parallel to the engine
centerline axis.
5. The engine as recited in claim 1, wherein said fan section
operates during engine operation at a corrected fan tip speed less
than about 1150 ft/second.
6. The engine as recited in claim 5, wherein said first turbine
section operates at a pressure ratio that is greater than about
five (5).
7. The engine as recited in claim 6, wherein said gear system
defines a gear reduction ratio of greater than or equal to about
2.5.
8. The engine as recited in claim 7, wherein said fan bypass
airflow defines a bypass ratio greater than about six (6).
9. The engine as recited in claim 8, wherein said fan bypass
airflow defines a bypass ratio greater than about ten (10).
10. The engine as recited in claim 9, wherein the plurality of fan
blades comprises twenty (20) or less fan blades.
11. The engine as recited in claim 1, including an auxiliary port
defined between the second nacelle section and the first nacelle
section when the second nacelle section is moved axially aft, the
auxiliary port defining a flow area for increasing bypass flow.
12. The engine as recited in claim 11, including an entrance angle
into the auxiliary port of less than twenty (20) degrees.
13. The engine as recited in claim 11, wherein a flow area of the
bypass flow path upstream of the auxiliary port is greater than a
flow area through the auxiliary port.
14. The engine as recited in claim 13, wherein the auxiliary port
includes a forward most edge on in interior surface of the fan
nacelle, wherein the forward most edge is spaced axially forward of
a maximum radial distance between an inner surface of the second
nacelle section and the engine centerline.
15. The engine as recited in claim 14, wherein a duct
cross-sectional area forward of the auxiliary port is greater than
the port opening cross-sectional area.
16. The engine as recited in claim 15, wherein said first turbine
section operates at a pressure ratio that is greater than about
five (5).
17. The engine as recited in claim 16, wherein the second nacelle
section is supported on a track faring for movement axially
relative to the first nacelle section.
18. The engine as recited in claim 17, wherein a cross-sectional
area forward of the auxiliary port is greater than a
cross-sectional area of the auxiliary port.
19. The engine as recited in claim 1, including a plurality of fan
exit guide vanes extending radially between the core nacelle and
the fan nacelle aft of the fan section.
20. The engine as recited in claim 1, wherein the second nacelle
section comprises at least two sectors, with each of the two
sectors movable independently.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present disclosure is a continuation of U.S. patent
application Ser. No. 13/340,810, filed Dec. 30, 2011, which is a
continuation in part of U.S. patent application Ser. No. 13/314365,
filed Dec. 8, 2011, which is a continuation in part of U.S. patent
application Ser. No. 11/843,675 filed Aug. 23, 2007, now U.S. Pat.
No. 8,074,440 granted on Dec. 13, 2011.
BACKGROUND
[0002] The present disclosure relates to a gas turbine engine, and
more particularly to a turbofan engine having a fan variable area
nozzle (VAFN) which moves axially to change a bypass flow path area
thereof.
[0003] Conventional gas turbine engines generally include a fan
section and a core engine with the fan section having a larger
diameter than that of the core engine. The fan section and the core
engine are disposed about a longitudinal axis and are enclosed
within an engine nacelle assembly.
[0004] Combustion gases are discharged from the core engine through
a core exhaust nozzle while an annular fan flow, disposed radially
outward of the primary airflow path, is discharged through an
annular fan exhaust nozzle defined between a fan nacelle and a core
nacelle. A majority of thrust is produced by the pressurized fan
air discharged through the fan exhaust nozzle, the remaining thrust
being provided from the combustion gases discharged through the
core exhaust nozzle.
[0005] The fan nozzles of conventional gas turbine engines have a
fixed geometry. The fixed geometry fan nozzles are a compromise
suitable for take-off and landing conditions as well as for cruise
conditions. Some gas turbine engines have implemented fan variable
area nozzles. The fan variable area nozzle provide a smaller fan
exit nozzle diameter during cruise conditions and a larger fan exit
nozzle diameter during take-off and landing conditions. Existing
fan variable area nozzles typically utilize relatively complex
mechanisms that increase overall engine weight to the extent that
the increased fuel efficiency therefrom may be negated.
SUMMARY
[0006] In a featured embodiment, a gas turbine engine includes a
core nacelle defined about an engine centerline axis. A core engine
is at least partially disposed within the core nacelle. The core
engine includes a first turbine section driving a first compressor
section and a second turbine section driving a second compressor
section. A fan section with a plurality of fan blades. A gear
system is driven through a shaft coupled to the first turbine
section. The gear system provides a speed reduction between the
first turbine section and the fan section of greater than 2.3. A
fan nacelle is mounted at least partially around the fan section
and the core nacelle to define a fan bypass flow path for a fan
bypass airflow. The fan bypass airflow has a fan pressure ratio of
the fan bypass airflow during engine operation less than 1.45. The
variable area fan bypass duct opening includes a first nacelle
section and a second nacelle section. The second nacelle section is
movable relative to the first nacelle section to vary an exit area
from the fan stream to selectively lower the fan pressure ratio
during engine operation.
[0007] In another embodiment according to the previous embodiment,
further includes a controller operable to reduce said fan nozzle
exit area at a cruise flight condition.
[0008] In another embodiment according to any of the previous
embodiments, the controller is operable to control the fan nozzle
exit area to reduce a fan instability.
[0009] In another embodiment according to any of the previous
embodiments, the second nacelle section is movable axially
substantially parallel to the engine centerline axis.
[0010] In another embodiment according to any of the previous
embodiments, the fan section operates during engine operation at a
corrected fan tip speed less than about 1150 ft/second.
[0011] In another embodiment according to any of the previous
embodiments, the first turbine section operates at a pressure ratio
that is greater than about five (5).
[0012] In another embodiment according to any of the previous
embodiments, the gear system defines a gear reduction ratio of
greater than or equal to about 2.5.
[0013] In another embodiment according to any of the previous
embodiments, the fan bypass airflow defines a bypass ratio greater
than about six (6).
[0014] In another embodiment according to any of the previous
embodiments, the fan bypass airflow defines a bypass ratio greater
than about ten (10).
[0015] In another embodiment according to any of the previous
embodiments, the plurality of fan blades includes twenty (20) or
less fan blades.
[0016] In another embodiment according to any of the previous
embodiments, includes an auxiliary port defined between the second
nacelle section and the first nacelle section when the second
nacelle section is moved axially aft. The auxiliary port defines a
flow area for increasing bypass flow.
[0017] In another embodiment according to any of the previous
embodiments, includes an entrance angle into the auxiliary port of
less than twenty (20) degrees.
[0018] In another embodiment according to any of the previous
embodiments, a flow area of the bypass flow path upstream of the
auxiliary port is greater than a flow area through the auxiliary
port.
[0019] In another embodiment according to any of the previous
embodiments, the auxiliary port includes a forward most edge on in
interior surface of the fan nacelle. The forward most edge is
spaced axially forward of a maximum radial distance between an
inner surface of the second nacelle section and the engine
centerline.
[0020] In another embodiment according to any of the previous
embodiments, a duct cross-sectional area forward of the auxiliary
port is greater than the port opening cross-sectional area.
[0021] In another embodiment according to any of the previous
embodiments, the first turbine section operates at a pressure ratio
that is greater than about five (5).
[0022] In another embodiment according to any of the previous
embodiments, the second nacelle section is supported on a track
faring for movement axially relative to the first nacelle
section.
[0023] In another embodiment according to any of the previous
embodiments, a cross-sectional area forward of the auxiliary port
is greater than a cross-sectional area of the auxiliary port.
[0024] In another embodiment according to any of the previous
embodiments, includes a plurality of fan exit guide vanes extending
radially between the core nacelle and the fan nacelle aft of the
fan section.
[0025] In another embodiment according to any of the previous
embodiments, the second nacelle section includes at least two
sectors, with each of the two sectors movable independently.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The various features and advantages of this disclosure will
become apparent to those skilled in the art from the following
detailed description of an embodiment. The drawings that accompany
the detailed description can be briefly described as follows:
[0027] FIG. 1A is a general schematic partial fragmentary view of
an exemplary gas turbine engine embodiment for use with the present
disclosure;
[0028] FIG. 1B is a rear view of the engine;
[0029] FIG. 1C is a side view of the engine integrated with a
pylon;
[0030] FIG. 1D is a perspective view of the engine integrated with
a pylon;
[0031] FIG. 2A is a sectional side view of the VAFN in a closed
position;
[0032] FIG. 2B is a sectional side view of the VAFN in an open
position; and
[0033] FIG. 3 is a graph of a bypass duct normalized
cross-sectional area distribution.
[0034] FIG. 4 is a graph of a Effective Area Increase vs. Nozzle
Translation;
[0035] FIG. 5 is a graph of a duct area distribution;
[0036] FIG. 6A is schematic geometric view of the auxiliary port
location;
[0037] FIG. 6B is schematic geometric view of the auxiliary port
entrance angle; and
[0038] FIG. 6C is schematic geometric view of a VAFN outer surface
curvature.
DETAILED DESCRIPTION
[0039] FIG. 1A illustrates a general partial fragmentary schematic
view of a gas turbofan engine 10 suspended from an engine pylon P
within an engine nacelle assembly N as is typical of an aircraft
designed for subsonic operation.
[0040] The turbofan engine 10 includes a core engine within a core
nacelle 12 that houses a low spool 14 and high spool 24. The low
spool 14 includes a low pressure compressor 16 and low pressure
turbine 18. The low spool 14 drives a fan section 20 through a gear
train 22. The high spool 24 includes a high pressure compressor 26
and high pressure turbine 28. A combustor 30 is arranged between
the high pressure compressor 26 and high pressure turbine 28. The
low and high spools 14, 24 rotate about an engine axis of rotation
A.
[0041] The engine 10 is preferably a high-bypass geared aircraft
engine. In one disclosed, non-limiting embodiment, the engine 10
bypass ratio is greater than about six (6), with an example
embodiment being greater than about ten (10), the gear train 22 is
an epicyclic gear train such as a planetary gear system or other
gear system with a gear reduction ratio of greater than about 2.3
and the low pressure turbine 18 has a pressure ratio that is
greater than about 5. In one disclosed embodiment, the engine 10
bypass ratio is greater than about ten (10:1), the turbofan
diameter is significantly larger than that of the low pressure
compressor 16, and the low pressure turbine 18 has a pressure ratio
that is greater than about 5:1. Low pressure turbine 18 pressure
ratio is pressure measured prior to inlet of low pressure turbine
18 as related to the pressure at the outlet of the low pressure
turbine 18 prior to exhaust nozzle. The gear train 22 may be an
epicycle gear train such as a planetary gear system or other gear
system with a gear reduction ratio of greater than about 2.5:1. It
should be understood, however, that the above parameters are only
exemplary of one embodiment of a geared architecture engine and
that the present disclosure is applicable to other gas turbine
engines including direct drive turbofans.
[0042] Airflow enters a fan nacelle 34, which at least partially
surrounds the core nacelle 12. The fan section 20 communicates
airflow into the core nacelle 12 to power the low pressure
compressor 16 and the high pressure compressor 26. Core airflow
compressed by the low pressure compressor 16 and the high pressure
compressor 26 is mixed with the fuel in the combustor 30 and
expanded over the high pressure turbine 28 and low pressure turbine
18. The turbines 28, 18 are coupled for rotation with, respective,
spools 24, 14 to rotationally drive the compressors 26, 16 and
through the gear train 22, the fan section 20 in response to the
expansion. A core engine exhaust E exits the core nacelle 12
through a core nozzle 43 defined between the core nacelle 12 and a
tail cone 32.
[0043] The core nacelle 12 is supported within the fan nacelle 34
by structure 36 often generically referred to as Fan Exit Guide
Vanes (FEGVs). A bypass flow path 40 is defined between the core
nacelle 12 and the fan nacelle 34. The engine 10 generates a high
bypass flow arrangement with a bypass ratio in which approximately
80 percent of the airflow entering the fan nacelle 34 becomes
bypass flow B. The bypass flow B communicates through the generally
annular fan bypass flow path 40 and is discharged from the engine
10 through a fan variable area nozzle (VAFN) 42 which defines a fan
nozzle exit area 44 between the fan nacelle 34 and the core nacelle
12 at a fan nacelle end segment 34S of the fan nacelle 34
downstream of the fan section 20.
[0044] Thrust is a function of density, velocity, and area. One or
more of these parameters can be manipulated to vary the amount and
direction of thrust provided by the bypass flow B. The Variable
Area Fan Nozzle ("VAFN") 42 operates to effectively vary the area
of the fan nozzle exit area 44 to selectively adjust the pressure
ratio of the bypass flow B in response to a controller C. Low
pressure ratio turbofans are desirable for their high propulsive
efficiency. However, low pressure ratio fans may be inherently
susceptible to fan stability/flutter problems at low power and low
flight speeds. The VAFN 42 allows the engine to change to a more
favorable fan operating line at low power, avoiding the instability
region, and still provide the relatively smaller nozzle area
necessary to obtain a high-efficiency fan operating line at
cruise.
[0045] A significant amount of thrust is provided by the bypass
flow B due to the high bypass ratio. The fan section 20 of the
engine 10 may include twenty (20) or less fan blades 20B which is
designed for a particular flight condition--typically cruise at
about 0.8 Mach and about 35,000 feet. The flight condition of 0.8
Mach and 35,000 ft, with the engine at its best fuel
consumption--also known as "bucket cruise Thrust Specific Fuel
Consumption (`TSFC`)"--is the industry standard parameter of lbm of
fuel being burned divided by lbf of thrust the engine produces at
that minimum point. "Low fan pressure ratio" is the pressure ratio
across the fan blade alone, without the Fan Exit Guide Vane
("FEGV") system 36. The low fan pressure ratio as disclosed herein
according to one non-limiting embodiment is less than about 1.45.
"Low corrected fan tip speed" is the actual fan tip speed in ft/sec
divided by an industry standard temperature correction of [(T
ambient deg R)/518.7) 0.5]. The "Low corrected fan tip speed" as
disclosed herein according to one non-limiting embodiment is less
than about 1150 ft/second.
[0046] As the fan blades 20B within the fan section 20 are
efficiently designed at a particular fixed stagger angle for an
efficient cruise condition, the VAFN 42 is operated to effectively
vary the fan nozzle exit area 44 to adjust fan bypass air flow such
that the angle of attack or incidence on the fan blades is
maintained close to the design incidence for efficient engine
operation at other flight conditions, such as landing and takeoff
to thus provide optimized engine operation over a range of flight
conditions with respect to performance and other operational
parameters such as noise levels.
[0047] The VAFN 42 is separated into at least two sectors 42A-42B
(FIG. 1B) defined between the pylon P and a lower Bi-Fi splitter L
which typically interconnects a larger diameter fan duct reverser
cowl and a smaller diameter core cowl (FIGS. 1C and 1D). Each of
the at least two sectors 42A-42B are independently adjustable to
asymmetrically vary the fan nozzle exit area 44 to generate
vectored thrust. It should be understood that although two segments
are illustrated, any number of segments may alternatively or
additionally be provided.
[0048] In operation, the VAFN 42 communicates with a controller C
or the like to adjust the fan nozzle exit area 44 in a symmetrical
and asymmetrical manner. Other control systems including an engine
controller or aircraft flight control system may also be usable
with the present disclosure. By adjusting the entire periphery of
the VAFN 42 symmetrically in which all sectors are moved uniformly,
thrust efficiency and fuel economy are maximized during each flight
condition. By separately adjusting the circumferential sectors
42A-42B of the VAFN 42 to provide an asymmetrical fan nozzle exit
area 44, engine bypass flow is selectively vectored to provide, for
example only, trim balance or thrust controlled maneuvering
enhanced ground operations or short field performance.
[0049] The VAFN 42 generally includes an auxiliary port assembly 50
having a first fan nacelle section 52 and a second fan nacelle
section 54 movably mounted relative the first fan nacelle section
52. The second fan nacelle section 54 axially slides along the
engine axis A relative the fixed first fan nacelle section 52 to
change the effective area of the fan nozzle exit area 44. The
second fan nacelle section 54 slides aftward upon a track fairing
56A, 56B (illustrated schematically in FIGS. 1C and 1D) in response
to an actuator 58 (illustrated schematically). The track fairing
56A, 56B extend from the first fan nacelle section 52 adjacent the
respective pylon P and the lower Bi-Fi splitter L (FIG. 1D).
[0050] The VAFN 42 changes the physical area and geometry of the
bypass flow path 40 during particular flight conditions. The bypass
flow B is effectively altered by sliding of the second fan nacelle
section 54 relative the first fan nacelle section 52 between a
closed position (FIGS. 2A) and an open position (FIGS. 2B). The
auxiliary port assembly 50 is closed by positioning the second fan
nacelle section 54 in-line with the first fan nacelle section 52 to
define the fan nozzle exit area 44 as exit area FO (FIG. 2A).
[0051] The VAFN 42 is opened by moving the second fan nacelle
section 54 aftward along the track fairing 56A, 56B away from the
first fan nacelle section 52 to open an auxiliary port 60 which
extends between the open second fan nacelle section 54 relative the
first fan nacelle section 52 to essentially provide an increased
fan nozzle exit area 44 exit area F1. That is, the exit area F1
with the port 60 is greater than exit area F0 (FIG. 2B).
[0052] In one disclosed embodiment, the auxiliary port 60 is
incorporated into the exhaust system of a high bypass ratio
commercial turbofan engine within the bypass duct aft of the Fan
Exit Guide Vanes (FEGVs; FIGS. 2A, 2B). The auxiliary port 60 is
located in the aft section of the bypass duct outer wall.
[0053] Referring to FIG. 3, the bypass duct area distribution, the
effective area increase vs. translation (FIG. 4), area distribution
(FIG. 5), and auxiliary port 60 location (FIG. 6A) and wall
curvatures (FIG. 6B-6C) are tailored to provide a proper flow-field
that allows the auxiliary port 60 to obtain the required additional
effective exit area. The auxiliary port 60 will essentially double
the effective area gain due to translation. The auxiliary port 60
provides a relatively low weight method of providing increased exit
area to control the fan operating line without causing high system
losses or unacceptable aircraft installation issues. By tailoring
the bypass duct area distribution and outer wall curvature, the
desired maximum effective area increase is achieved before the
stroke of the auxiliary port 60 reaches its effective area increase
limit.
[0054] The auxiliary port exit plane 44B (defined as the plane
between the stationary section's trailing edge and the moving
sections leading edge) initially has an opening in which the exit
plane normal vector is near-axial, but as the stroke increases, the
normal vector becomes more inclined and approaches a near-radial
vector. Once the exit plane normal has become near-radial, the
maximum auxiliary port effectiveness has been reached. Once this
point is reached, the rate of the effective area vs. translation
changes from steep slope of the "well designed port" the shallow
rate of the "main nozzle only", since additional area will be
provided through the main nozzle 44A due to the inward slope of the
core nacelle 12. A well designed auxiliary port nozzle will achieve
approximately +25% effective area before the port effectiveness
limit is reached. That is, there is a limited range of stroke in
which the auxiliary port doubles the rate of additional
effectiveness. Outside of this range, the rate of additional
effectiveness may be equivalent to a translating nozzle that has no
auxiliary port. Or put another way, the auxiliary port reduces the
stroke necessary for a pure translating nozzle to achieve a desired
effective area.
[0055] Referring to FIG. 5, the cross-sectional area at the
auxiliary port 60 is greater than the maximum required effective
area of the VAFN 42 and the bypass duct area distribution is
tailored to ensure the duct cross-sectional area forward of the
auxiliary port 60 is greater than the port opening cross-sectional
area. This avoids a situation where an upstream internal
cross-section becomes the controlling flow area (i.e. is smaller
than the exit area), which can lead to operational limits and
structural issues.
[0056] Referring to FIG. 6A, the auxiliary port 60 in the disclosed
embodiment, is located no more forward than 0.1 DEL_X/L_DUCT
defined from a point D at the largest radius Rmax of the annular
fan bypass flow path 40 defined by the second fan nacelle section
54. Rmax is defined through point D and perpendicular to the engine
axis A. Point D in the disclosed non limiting embodiment is located
on an inner wall surface 541 of the second fan nacelle section 54
when the second fan nacelle section 54 is in a closed position.
DEL_X is the axial distance to the forward most point of the
auxiliary port 60 from Rmax. L_DUCT is the overall axial length of
the annular fan bypass flow path 40. The angle between the mean
port line and the fan duct outer wall is relatively low to provide
well-behaved, low loss exit flow. In the disclosed embodiment, the
auxiliary port 60 entrance angle (Theta in) relative to the fan
bypass duct OD wall, is less than 20 degrees (FIG. 6B) while the
outer VAFN surface has an R_ARC/CHORD >0.7 where R_ARC is a
radial distance from the engine axis A to a radial outer wall
surface 540 of the second fan nacelle section 54 and CHORD is the
chord length of the second fan nacelle section 54. (FIG. 6C). The
curvature of the outer wall surface 540 near the auxiliary port 60
promotes flow through the auxiliary port 60. In one disclosed
embodiment, the stroke of the second fan nacelle section 54
necessary to obtain an additional 20% effective exit area is
approximately 8.4 inches.
[0057] In operation, the VAFN 42 communicates with the controller C
to move the second fan nacelle section 54 relative the first fan
nacelle section 52 of the auxiliary port assembly 50 to effectively
vary the area defined by the fan nozzle exit area 44. Various
control systems including an engine controller or an aircraft
flight control system may also be usable with the present
disclosure. By adjusting the axial position of the entire periphery
of the second fan nacelle section 54 in which all sectors are moved
simultaneously, engine thrust and fuel economy are maximized during
each flight regime by varying the fan nozzle exit area. By
separately adjusting the sectors of the second fan nacelle section
54 to provide an asymmetrical fan nozzle exit area 44, engine
bypass flow is selectively vectored to provide, for example only,
trim balance, thrust controlled maneuvering, enhanced ground
operations and short field performance.
[0058] The foregoing description is exemplary rather than defined
by the limitations within. Many modifications and variations of the
present disclosure are possible in light of the above teachings.
The preferred embodiments of this disclosure have been disclosed,
however, one of ordinary skill in the art would recognize that
certain modifications would come within the scope of this
disclosure. It is, therefore, to be understood that within the
scope of the appended claims, the disclosure may be practiced
otherwise than as specifically described. For that reason the
following claims should be studied to determine the true scope and
content of this disclosure.
* * * * *