Note: Descriptions are shown in the official language in which they were submitted.
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INFRARED SUPPRESSING TWO DIMENSIONAL'VECTORABLE SINGLE
EXPANSION RAMP NOZZLE
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to aircraft gas turbine engine two dimensional vectoring
nozzles
and, particularly, for such nozzles designed to block line of sight through
the nozzle's
exit.
High performance military aircraft typically include a turbofan gas turbine
engine
having an afterburner or augmenter for providing additional thrust when
desired and
some are being developed with two dimensional vectorable nozzles. The turbofan
engine includes in downstream serial flow communication, a multistage fan, a
multistage compressor, a combustor, a high pressure turbime powering the
compressor,
a low pressure turbine powering the fan, and the nozzle. During operation, air
is
compressed in turn through the fan and compressor and mixed with fuel in the
combustor and ignited for generating hot combustion gases which flow
downstream
through the turbine stages which extract energy therefrom. The hot core gases
are
then discharged into an exhaust section of the engine which includes an
augmenter
from which they are discharged from the engine through the nozzle which is
also
typically variable area exhaust nozzle.
One type of two dimensional nozzle is a single expansion ramp nozzle referred
to as a
SERN nozzle. SERN was developed as a variable area n.on-axisymmetric nozzle
with
a unique installed performance characteristic of low weight and frictional
drag
because there is no or a smaller lower cowl. Low observable (LO) exhaust
nozzle
technology is being developed for current and future fighter/attack aircraft.
LO
nozzles should be integrated cleanly with the aircraft airframe and not
degrade the
aircraft's performance due to weight and drag penalties. Exhaust systems for
combat
aircraft should possess characteristics to enhance aircraft: survivability,
including high
internal performance, reduced radar cross section (RCS),, low infrared (IR)
signatures,
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low installed weight, low installation drag and, in same cases, thrust-
vectoring
capabilities.
Two dimensional nozzles have been developed for thf; purpose of accomplishing
thrust vectoring. Two dimensional vectorable exhaust nozzles incorporate upper
and
lower flaps that are angled simultaneously for the purpose of deflecting
exhaust gas in
an upward or downward direction. Increasing the angle of the flaps increases
the
amount of turning that is imparted to the exhaust gas flow.
The augmenter includes an exhaust casing and liner therein which defines a
combustion zone. Fuel spraybars and flameholders are mounted between the
turbines
and the exhaust nozzle for injecting additional fuel when desired during
reheat
operation for burning in the augmenter for producing additional thrust. In a
bypass
turbofan engine, an annular bypass duct extends from the fan to the augmenter
for
bypassing a portion of the fan air around the core engine to the augmenter.
The
bypass air is used in part for cooling the exhaust liner and also is mixed
with the core
gases prior to discharge through the exhaust nozzle. Turbojets, engines
without
bypass ducts may also use augmenters and variable area two dimensional
nozzles.
Various types of flameholders are known and typically include radial and
circumferential V-shaped gutters which provide local low velocity
recirculation and
stagnation regions therebehind, in otherwise high velocity core gas flow, for
sustaining combustion during reheat operation. Since the core gases are the
product
of combustion in the core engine, they are initially hot when they leave the
turbine,
and are further heated when burned with the bypass air and additional fuel
during
reheat operation.
The hot parts of the engine visible along lines of sight: through the exhaust
nozzle
produce an infrared signal or signature. The rotating turbine has a radar
detectable
signature or radar cross section (RCS). This invention relates to apparatus
for
reducing the engine°s radar cross-section and suppressing and masking
infrared (IR)
emissions through engine exhaust ducts particularly those due to turbine and
augmenter parts. Successful operation of combat aircraft is dependent, in
part, upon
the ability of the aircraft to remain undetected by ini~rared sensors and
radars of
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missiles during flight. The high temperatures of the engine's exhaust gases
and the
hot metal turbine parts and the hot metal walls directly in contact with the
hot gases
cause the engine to emit high levels of infrared energy. Military aircraft
engaged in
combat are vulnerable to anti-aircraft missiles employing highly sophisticated
infrared
sensors and radar.
SUMMARY OF THE INVENTION
A two dimensional gas turbine engine exhaust nozzle includes transversely
spaced
apart upper and lower convergent and divergent flaps extending longitudinally
in a
downstream direction along a nozzle axis and disposed between two widthwise
spaced apart sidewalk. The upper and Iower divergent flaps have inwardly
facing
upper and lower flap surfaces defining together with the sidewalls at least a
part of an
exhaust stream flowpath therebetween. The upper and lower flap surfaces have
respective upper and lower apexes wherein the upper apex is axially spaced
apart and
aft of the lower apex. The upper divergent flap has an expansion ramp
diverging
away from the nozzle axis and includes a ramp section of the upper flap
surface that
extends aftwardly from the upper apex and aftwardly of a trailing edge of the
lower
divergent flap. The exemplary embodiment of the nozzle further includes
transversely spaced apart upper and lower convergent and divergent flap axes
extending widthwise between the sidewalls wherein the upper convergent and
divergent flaps are rotatable about the upper convergent: and divergent flap
axes and
the lower convergent and divergent flaps are rotatable about the lower
convergent and
divergent flap axes, respectively.
In a more particular embodiment of the invention, the upper and lower
divergent flaps
are rotatably attached to downstream ends of the upper and lower convergent
flaps
along the upper and lower divergent flap axes, respectively. The upper and
lower
divergent flaps are operably rotatable to angularly vector an exhaust flow aft
of the
apexes upwardly and downwardly with respect to the nozzle axis. The divergent
flaps
are operably movable to block a line of sight along the nozzle axis through an
exit of
the nozzle during engine operation. The divergent flaps may be positioned to
block a
range of lines of sight through the nozzle exit at acute angles to the nozzle
axis. A
throat extends generally transversely across the exhaust stream flowpath
between a
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first position on the lower apex to a second position on the upper divergent
flap
downstream of the upper flap axis. The upper divergent flap is generally
convex and
the lower divergent flap is generally concave between the upper and lower
apexes,
respectively. The exhaust stream flowpath diverges in the downstream direction
between the lower apex and the upper apex. A more particular embodiment of the
invention includes an air flow injection means for injecting air through air
injection
apertures in at least one of the upper and lover divergent flaps and the
sidewalk. The
air flow injection means includes at least one row of the air injection
apertures in each
of the upper and lower divergent flaps and the sidewall s. The air injection
apertures
may be located in at least one plane normal to a direction of exhaust flow in
the
exhaust stream flowpath along the upper apex.
The exemplary embodiment of the invention further includes, extending
longitudinally in a downstream direction along a nozzle axis and in downstream
serial
flow relationship, a convergent section and a divergent section and a throat
therebetween. The convergent section includes, in downstream serial flow
relationship, transversely spaced apart upper and lower convergent non-
rotatable
walls, rotatable upper and lower reverser doors, and the upper and lower
convergent
flaps extending longitudinally in the downstream directiion along the nozzle
axis and
disposed between the two widthwise spaced apart sidewalk. Transversely spaced
apart upper and lower reverser door axes extend widthwise between the sidewalk
wherein the upper and lower reverser doors are rotatable about the upper and
lower
reverser door axes, respectively. The upper and lower reverser doors rotatably
open to
upper and lower reverse air flow passages angled in an upstream direction from
the
exhaust stream flowpath to outside of the nozzle.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and other features of the invention are explained in the
following description, taken in connection with the accompanying drawings
where:
FIG. 1 is a longitudinal sectional view illustration of exemplary embodiment
of an
aircraft gas turbine engine with a single expansion ramp nozzle having axially
offset
upper and lower apexes of upper and lower nozzle flaps respectively.
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FIG. 2 is an enlarged longitudinal sectional view illustration of the nozzle
in FIG. 1.
FIG. 3 is an enlarged view illustration of fluidic nozzle :injection through 3-
3 in FIG.
2.
FIG. 4 is a longitudinal sectional view illustration of the nozzle in FIG. 1.
configured
for cruise.
FIG. 5 is a longitudinal sectional view illustration of the nozzle in FIG. 1.
configured
wide open.
FIG. 6 is a longitudinal sectional view illustration of the nozzle in FIG. 1.
configured
for thrust reversal.
FIG. 7 is a longitudinal sectional view illustration of the nozzle in FIG. 1.
configured
for thrust vectoring in an upward direction.
FIG. 8 is a longitudinal sectional view illustration of the nozzle in FIG. 1.
configured
for thrust vectoring in a downward direction.
DETAILED DESCRIPTION OF THE INVENTION
Illustrated in FIG. 1 is an exemplary gas turbofan engine 10 having an engine
casing
13, of the fan bypass air type, including an exemplary embodiment of a two
dimensional single expansion ramp exhaust nozzle 50 of the present invention.
Disposed concentrically about a longitudinal centerline axis 12 of the engine
10,
within the engine casing 13 is a core engine 17. The core engine 17 includes,
in serial
flow communication, an inlet 14 for receiving ambient air 16, a fan 18, and a
high
pressure compressor (HPC) 20 disposed within an annular core engine casing 22.
The core engine 17 further includes a diffuser 24 and a combustor 26 disposed
in
downstream serial flow communication with the HPC 20. The core engine 17
further
includes, disposed in downstream serial flow communication with the combustor
26, a
high pressure (HP) turbine nozzle 28 followed by a high pressure turbine (HPT)
30 for
powering the HPC 20 through a HP shaft 32 extending t:herebetween. Downstream
of
the core engine 17 is a low pressure turbine (LPT) 34 that is in flow
communication
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with the HPT 30 for powering the fan 18 througlr~ a LP shaft 36 extending
therebetween.
The core engine casing 22 extends from the HPC 20 to the LPT 34 and is
surrounded
by a conventional bypass duct 38 for channeling a bypass portion of the
ambient air 16
compressed in the fan 18 as bypass air 40. A core portion 27 of the air 16
which is not
bypassed, is channeled into the HPC 20 which generates compressed airflow 42
which
is discharged from the HPC 20 into the diffuser 24. T'he compressed airflow 42
is
mixed with fuel and combusted in the combustor 26 for generating combustion
gases
44 which are channeled through the HPT 30 and the LPT 34 and discharged into
an
afterburner or augmentor 46 located downstream of the LPT 34.
In a dry mode of operation, the augmentor 46 is not used and the combustion
gases 44
are channeled therethrough. In a wet mode of operation, additional fuel is
mixed with
the combustion gases 44 and the bypass air 40 in a fuel injector and
flameholder
assembly 48 and ignited for generating additional thrust from the engine 10.
The
combustion gases 44 are discharged from the engine 10 through the exhaust
nozzle
50. The nozzle 50 is suitably attached to a downstream end 52 of the engine
casing 13
to transfer thrust generated by the nozzle to the engine 10.
FIG. 2 illustrates an exemplary embodiment of the nozzle 50 which is a
convergent
divergent two dimensional gas turbine engine exhaust nozzle. The nozzle SO
includes
transversely spaced apart upper and lower convergent flaps 54 and 56 and
transversely
spaced apart upper and lower divergent flaps 58 and 60, respectively,
extending
longitudinally in a downstream direction 64 along a nozzle axis 68 and
disposed
between two widthwise spaced apart first and second sidewalk 70 and 72
illustrated
in FIG. 3. The nozzle axis 68 in the exemplary embodiment is collinear with
the
longitudinal centerline axis 12 but need not be in other embodiments or
applications
of the invention.
The invention is described in terms of upper and lower elements and upward and
downward directions. This is for purpose of convenience and upper and lower
flaps
and other elements may be reversed. There are embodiments of the invention
wherein
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the nozzle installation is upside down with respect to the embodiments
illustrated in
the FIGS. The choice of upper and lower is one of choice for ease of
description.
The upper and lower divergent flaps 58 and 60 have inwardly facing upper and
lower
flap surfaces 74 and 76, respectively, which together with the sidewalk 70 and
72
define, at least a part, an exhaust stream flowpath 80 therebetween. The upper
and
lower flap surfaces 74 and 76 have respective upper and lower apexes 84 and 86
wherein the upper apex is axially spaced apart and aft of the lower apex. The
upper
divergent flap 58 has an expansion ramp 88 diverging away from the nozzle axis
68
and includes a ramp section 90 of the upper flap surface 74 that extends
aftwardly
from the upper apex 84 and aftwardly of a trailing edge 92 of the lower
divergent flap
60.
The exemplary embodiment of the nozzle 50 further includes transversely spaced
apart upper and lower convergent flap axes 96 and 98 and upper and lower
divergent
flap axes 100 and 102, respectively, extending widthwise between the sidewalls
70
and 72. The upper and lower convergent flaps 54 and 56 are rotatable about the
upper
and lower convergent flap axes 96 and 98, respectively. The upper and lower
divergent flaps 58 and 60 are rotatable about the upper and lower divergent
flap axes
100 and 102, respectively. This provides the nozzle 50 with the ability to
vector the
thrust of the engine by vectoring an exhaust flow 104 out; of the nozzle 50.
In the exemplary embodiment of the invention the upper and lower divergent
flaps 58
and 60 axe rotatably attached to downstream ends 106 of the upper and lower
convergent flaps 54 and 56 along the upper and lower divergent flap axes 100
and
102, respectively. The upper and lower divergent flaps 58 and 60 are operably
rotatable to angularly vector the exhaust flow 104 aft of the upper and lower
apexes
84 and 86 upwardly 130 and downwardly 134 with respect to the nozzle axis 68.
The
upper and lower divergent flaps 58 and 60 are movable to block a line of sight
along
the nozzle axis 68 through a nozzle exit 108 of the nozzle 50 during engine
operation.
The divergent flaps may be positioned to block a range of lines of sight
through the
nozzle exit at acute angles to the nozzle axis. A throat 110 extends generally
transversely across the exhaust stream flowpath 80 between a first position
112 on the
lower apex 86 to a second position 114 on the upper divergent flap 58 upstream
of the
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upper apex 84. The upper divergent flap 58 is generally convex and the lower
divergent flap 60 is generally concave between the upper and lower apexes 84
and 86,
respectively. The exhaust stream flowpath 80 diverges in the downstream
direcrion
64 between the lower apex 86 and the upper apex 84.
The nozzle 50 may include an air flow injection means 120 for injecting air
through
air injection apertures 122 in at least one of the upper and lower divergent
flaps 58
and 60 and the sidewalk 70 and 72 as illustrated in FIGS. 1 and 3. This
technique is
also referred to as fluidic nozzle injection and it is known to use a fluidic
nozzle for
both pitch and yaw thrust vectoring. The air flow injection means 120 may
include at
least one mw 124 of the air injection apertures 122 in each of the upper and
lower
divergent flaps 58 and 60 and sidewalk 70 and 72. The air injection apertures
122
may be located in at least one plane 128 normal to the exhaust flow 104 in the
exhaust
stream flowpath 80 along the upper apex 84 as illustrated herein. Other
arrangements
of the air injection apertures 122 may include longitudinally and transversely
spaced
apart arrays of the air injection apertures on one or all of the upper and
lower
divergent flaps 58 and 60 and the sidewalls 70 and 72.
Referring to FIGS. l, 2 and 6, the exemplary embodiment of the nozzle 50
further
includes, extending longitudinally in the downstream direction 64 along the
nozzle
axis 68 and in downstream serial flow relationship, a convergent section 140
and a
divergent section 142 and the throat 110 therebetween. The convergent section
140
includes, in downstream serial flow relationship, transversely spaced apart
upper and
lower convergent non-rotatable walls 146 and 148, respectively, upper and
lower
rotatable reverser doors 150 and 152, respectively;. and the upper and lower
convergent flaps 54 and 56 extending longitudinally in the downstream
direction 64
along the nozzle axis 68 and disposed between the two widthwise spaced apart
sidewalk 70 and 72. Transversely spaced apart upper and lower reverser door
axes
156 and 158, respectively, extend widthwise between the sidewalk 70 and 72 and
the
upper and lower reverser doors 150 and 152 are rotatable about the upper and
lower
reverser door axes, respectively. The upper and lower reverser doors 150 and
152
rotatably open to upper and lower reverse air flaw passages 160 and 162,
respectively,
angled in an upstream direction 164 from the exhaust stream flowpath 80 to
outside of
the nozzle 50. In the exemplary embodiment of the invention, the upper and
lower
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reverser door axes 156 and 158 are collinear with the upper and lower
convergent flap
axes 96 and 98.
FIG. 4 illustrates the nozzle 50 configured for supersonic and subsonic cruise
and the
upper and lower divergent and convergent flaps 54, 56, 58, 60 are positioned
such that
the upper and lower apexes 84 and 86 are positioned on the nozzle axis 68 such
that
the upper and lower divergent flaps 58,60 block the line of sight along the
nozzle axis
68 through the exit 108 of the nozzle 50. FIG. 5 illustrates the nozzle 50
configured
wide open as it may be operated during takeoff or for maximum thrust. FIG. 7
illustrates the nozzle 50 configured for pitch thrust vectoring in the upward
direction
and FIG. 8 illustrates the nozzle 50 configured for piitch thrust vectoring in
the
downward direction.
FIG. 6 illustrates the nozzle 50 configured for reverse thrust. The upper and
lower
reverser doors 150 and 152 are illustrated in a rotated open position and the
upper and
lower reverse air flow passages 160 and 162, respectively, are open. The upper
and
lower convergent flaps 54 and 56 are in a position rotated towards the nozzle
axis 68
so as to close off the exhaust stream flowpath 80 and prevent the exhaust flow
104 to
flow out the nozzle exit 108. This causes substantially all of the exhaust
flow 104 to
flow out the upper and lower reverse air flow passages 1.60 and 162, thus,
providing
reverse thrust for the engine 10.
The present invention has been described in an illustrative manner. It is to
be
understood that the terminology which has been used is intended to be in the
nature of
words of description rather than of limitation. While there have been
described
herein, what are considered to be preferred and exemplary embodiments of the
present
invention, other modifications of the invention shall be apparent to those
skilled in the
art from the teachings herein and, it is, therefore, desired to be secured in
the
appended claims all such modifications as fall within the true spirit and
scope of the
invention.
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