Note: Descriptions are shown in the official language in which they were submitted.
CA 02445934 2003-10-21
JET ENGINE NOZZLE V111TH VARIABLE
THRUST VECTORING AND EXHAUST AREA
The present invention relates to an exhaust nozzle for jet engines. Such a
nozzle may be used on business aircraft and for commercial aircraft for
optimizing
their take-off, climb and cruise performance, as well as i-or increasing
safety in flight
and reducing speed at landing.
Viable area exhaust nozzles are known in the art. For example, U.S. Patent
No. 5,221,048, which issued to the Jean-Pierre Lair on June 22, 1993,
describes a
variable exhaust area nozzle comprising a fixed structure having mounted
thereon
two pivoting half shells that cooperate radiaily and longitudinally with said
fixed
structure. The two shells and the fixed structure on which they are mounted
form
the rear part of the nacelle that encloses the engine. Thus, the two shells
and the
fixed structure form the exhaust nozzle of the engine. Fluid tightness between
the
two half shells and the fixed structure is provided by a sealing arrangement.
Actuators are used to pivot the shells into any position between their fully
opened
position and their fully closed position. The variation of the position of the
shells
provides adjustment of the value of the nozzle exhaust area to that required
to
optimum performance of the engine. Although adjustment of the position of the
two
shells provides control over the nozzle exhaust area, it does so without
modification
of the engine thrust vector angle.
Variable nozzle and thrust vectoring of the exhaust of a jet engine is known.
U.S. Patent No. 4,000,610, which issued to Dudley ~. Nash et al on January 4,
1977, discloses an apparatus using a flap downstream of a series of converging-
diverging flaps to provide flight maneuver (thrust) vectoring as well as
external
1
CA 02445934 2003-10-21
exhaust expansion control. While the series of flaps are internal to the
nozzle, and
are adapted to form a convergent-divergent shape, they cooperate with the one
flap
located downstream of the exhaust nozzle for external expansion control of the
exhaust. Convergent-divergent nozzles such as this are typically used on
supersonic aircraft such as military aircraft.
Thrust vectoring technology has been successfully demonstrated on tactical
military aircraft to provide manoeuvring advantages in very low speed, very
high
angle-of-attack flight regimes. Current research is exploring the benefits of
using
thrust vectoring to decrease cruise trim drag under high altitude and mid to
high
speed conditions. This technology has matured to the extent that it is being
incorporated into military fighter aircraft.
Thrust vectoring technology has been successfully demonstrated on tactical
military aircraft to provide manoeuvring advantages in very iow speed, very
high
angle-of-attack flight regimes. Current research is exploring the benefits of
using
thrust vectoring to decrease cruise trim drag under high altitude and mid to
high
speed conditions. This technology has matured to the extent that it is being
incorporated into military fighter aircraft.
As far as is known, thrust vectoring has not been used on commercial or
business aircraft. Some of the reasons for this are that the technology is
typically
very complex, and involves many moving parts, which is detrimental to the
overall
dispatch reliability and operational cost of a business or commercial
aircraft. Another
reason that thrust vectoring has not been used on commercial or business
aircraft is
that these aircraft usually have little need for manoeuvring agility. Despite
the
foregoing, the potential for improved safety and increased cruise efficiency
that may
2
CA 02445934 2003-10-21
result from the use of thrust vectoring would make it attractive to the
commercial and
business aircraft community if a simple thrust vectoring system having a low
number
of moving parts could be provided.
Thrust vectoring also could provide benefit to commercial and business
aircraft by providing improved longitudinal stability. Longitudinal stability
is needed
due to the fact that aircraft are designed to have an aerodynamic center of
pressure
(CP) located aft of the aircraft center of gravity (CG). As a result of this
arrangement,
cruising aircraft inherently have a nose down pitching moment, caused by the
CP
being aft of the CG. This nose down moment must be oifiset during flight by a
nose
up pitching moment created by the horizontal stabilizer. These opposing forces
help
maintain stability but create drag, which can reduce aircraft efficiency
Thrust vectoring may be used to assist in the provision of aircraft
longitudinal
stability and the reduction of overall drag during cruising by placing the
exhaust
nozzle in a °°nozzle up'° position. When the thrust
vector is directed upwards, the
vertical component of the thrust vector creates a nose up pitching moment for
the
aircraft. The nose up pitching moment produced by the thrust vector allows the
horizontal stabilizer to be operated at a lower angle-of-attack which reduces
the
negative lift created by the aircraft horizontal stabilizer and therefore
reduces the
aircraft drag. Furthermore, integration of the thrust vectoring system into
the flight
control system assists in providing aircraft longitudinal stability, thus
allowing highly
efficient reduced-tail designs, which in turn may reduce tail weight and
consequently
the overall aircraft weight.
Swept wing, T-tailed aircraft tend to suffer a marked nose up pitching moment
at aerodynamic stall which can allow the low energy turbulent airflow behind
the
3
CA 02445934 2003-10-21
wing to immerse the tail. This can greatly reduce the effectiveness of the
tail in
countering the nose up pitching moment. Vllhen the nose up pitching moment .
created by the wing during stall is greater than the nose down pitching moment
created by the horizontal tail, recovery from the stall may be impossible.
Just as
thrust vectoring may be used to assist the tail in providing a nose up
pitching
moment during cruise, thrust vectoring may be used to assist the tail in
providing a
nose down pitching moment during stall. All that is required is 'that the
nozzle be
placed in a nozzle-down position.
Thrust vectoring may be used further to improve landing performance and
decrease or eliminate the need for thrust reversers. ~anding performance is
predicated on the landing approach being carried out at a generally constant
angle-
of-attack. At a generally constant angle-of-attack, airspeed varies directly
with the
weight supported by the wing i.e., aircraft weight. Required runway length is
a
function of aircraft weight, approach speed, and aircraft braking ability. As
the ability
to increase runway length and decrease aircraft weight is somewhat limited,
control
over aircraft stopping distance is largely exercised through control of
braking ability.
lUlost aircraft, at landing, use thrust reversers for deceleration. However,
these
reversers, which are used at landing for about 30 seconds, can produce
catastrophic
events if an inadvertent deployment occurs during flight. Thrust reversers are
required primarily on a wet or icy runway, because of the high speeds at which
aircraft are required to land. If the landing speed of aircraft could be
reduced, the
need for thrust reversers could potentially be avoided. Tlnus, there is a need
for
aircraft engines that enable the landing speed of an aircraft to be reduced.
4
CA 02445934 2003-10-21
One such method of reducing aircraft landing speed may be to provide an
engine that assists in lift through adjustment of the engine thrust vector. By
placing
the exhaust nozzle in a nozzle-down position, some portion of the aircraft
weight
may be supported directly by the vertical component of the vectored thrust
thus
reducing the weight supported by the wing. This support of the aircraft by a
vertical
component of thrust vectoring could be used to reduce approach speeds, and
thus
reduce landing speeds. Reduced landing speeds could decrease or eliminate the
need for thrust reversers on the aircraft. Induced drag would be decreased and
angle-of attack reduced.
Thrust vectoring may also be used to assist in maneuvering an aircraft. For
fuselage mounted engines in particular, the left engine exhaust nozzle can be
controlled to an asymmetrical vectoring position (nozzle up for example) while
the
exhaust nozzle of the right engine is controlled to the opposite direction
(nozzle
down position), and vice versa. Such thrust vectoring may be used to generate
a
rolling moment to the aircraft. If the thrust vectoring system is integrated
into the
flight control andlor auto-flight systems, then an independent backup flight
control
system is available to the flight crew. Furthermore, if power for the thrust
vectoring
system is different from the flight control system i.e., electric vs.
hydraulic, then an
additional level of redundancy is created, which further increases the overall
safety
of the aircraft. On a multi-engine aircraft, pitch axis thrust vectoring can
create
aircraft movement about the pitch (symmetrical vectoring) and roll
(asymmetrical
vectoring) axes.
The system described and claimed herein, may provide the foregoing
advantages and is an improvement over the systems disclosed in U.S. Pat. Nos.
5
CA 02445934 2003-10-21
5,221,048 and 4,000,610. As compared with these prior systems, various
embodiments of the present invention require fewer moving parts, are not
complex,
and are relatively inexpensive, while allowing for variation of both the
nozzle exhaust
area and the engine thrust vector angle. This permits both exhaust area and
thrust
vector angle to be adjusted for optimized engine performance during different
flight
conditions.
It is therefore an object of the present invention to provide a jet engine
nozzle
with thrust vectoring capabilities.
It is another object of the present invention to provide a jet engine nozzle
with
variable exhaust area capabilities.
It is yet another object of the present invention to provide a jet engine
nozzle
with both thrust vectoring and variable exhaust area capabilities.
It is still another object of the present invention to provide a jet engine
nozzle
with thrust vectoring and variable exhaust area capabilities that has fewer
moving
parts than previously known nozzles.
It is yet another object of the present invention to provide a jet engine
nozzle
with thrust vectoring and variable exhaust area capabilities that is less
expensive to
make or maintain than previously known nozzles.
It is still yet another object of the present invention to provide a jet
engine
nozzle that improves the longitudinal stability of an aircraft.
It is still yet another object of the present invention to provide a jet
engine
nozzle that reduces the required landing speed of an aircraft.
It is still yet another object of the present invention to provide a jet
engine
nozzle that may be used to pitch and/or roll an aircraft.
6
CA 02445934 2003-10-21
Other objects, characteristics and advantages will become apparent from the
following description in reference to the accompanying drawings.
The invention comprises a variable area exhaust nozzle with variable thrust
vector angle for one or more jet engines having shells pivotally mounted on a
fixed
structure called jet pipe with two extending arms. The jet pipe with its
extending
arms and the pivoting shelBs form the exhaust nozzle of the engine. The shells
are
pivoted and controlled by actuator means which pivot the shells either to a
symmetrical configuration for changing the value of the exhaust area of the
nozzle or
unsymmetricai configuration for changing the value of the angle of the thrust
vector
relative to the engine centerline. The actuator can be hydraulic, electric or
pneumatic
or other extendible actuators to provide controlled pivoting of the shells. In
one
embodiment there is a single actuator per shell, said actuator being connected
to the
jet pipe and the shell to provide controlled pivoting of said shell; in this
embodiment,
said actuator is located substantially in the vicinity of the plane of
symmetry of said
shell. In another embodiment there are dual actuators on each side of the jet
pipe to
provide controlled pivoting of the shells. The invention includes a method for
adapting an exhaust nozzle mounted on the aft portion of a nacelle which wraps
a
turbo-fan engine, by varying the value of the exit area or by changing the
thrust
vector angle of said exhaust nozzle during a flight segment.
The method also includes varying the value of the exhaust area of the nozzle
and the thrust vector angle on opposite side engines, whether said engines are
aircraft wings mounted or fuselage mounted.
ft is to be understood that both the foregoing general description and the
following detailed description are exemplary and explanatory only, and are not
7
CA 02445934 2003-10-21
restrictive of the invention as claimed. The accompanying drawings, which
constitute
a part of this specification, illustrate certain embodiments of the invention,
and
together with the detailed description serve to explain the principles of the
present
invention.
The details of the present invention, both as to its structure and operation,
may be gleaned in part by study of the accompanying drawings, in which like
reference numerals refer to like parts, and in which:
FIG. 1 is a schematic side view of a nozzle in accordance with a first
embodiment of the present invention;
FIG. 2 is a schematic side view of the nozzle shown in FIG. 1 in a Nominal
position;
FIG. 3 is a schematic side view of the nozzle shown in FIG. 1 in a reduced
exhaust area (closed) position;
FIG. 4 is schematic side view of the nozzle shown in FIG. 1 in an increased
exhaust area (opened) position;
FIG. 5 is a schematic side view of the nozzle shown in FIG. 1 in a down thrust
vector position;
FIG. 6 is a schematic side view of the nozzle shown in FIG. 1 in an up thrust
vector position;
FIG. 7 is a schematic perspective view of the actuators that may be used to
pivot the shells comprising the nozzle shown in FIG. 1, the actuators are
shown in a
Nominal position;
FIG. 8 is a schematic perspective view of the actuators shown in FIG. 7 in a
thrust vector down position;
8
CA 02445934 2003-10-21
FIG. 9 is a schematic perspective view of the actuators shown in FIG. 7 in a
thrust vector up position;
FIG. 10 is a schematic side view of a nozzle in accordance with a second
embodiment of the present invention;
FIG. 11 is a schematic side view of the nozzle shown in FIG. 70 in a thrust
vector up position;
FIG. 12 is a schematic side view of the nozzle shown in FIG. 10 in a thrust
vector down position;
FIG. 13 is a schematic side view of the nozzle shown in FIG. 10 in the
increased exhaust area {opened) position;
FIG. 14 is a schematic side view of the nozzle shown in FIG. 10 in the
decreased exhaust area (closed) position;
FIG. 15 is a schematic side view of the nozzles shown in FIGS. 1 and 10
showing the sealing arrangement; and
FIG. 16 is a schematic side view of a nozzle in accordance with an alternative
embodiment of the present invention.
The exhaust system of the invention is described more fully as follows.
With reference to FIG. 1, in a first embodiment of the present invention, a
thrust vectoring and variable exhaust area nozzle 10 for a jet engine such as
a
turbo-fan is provided by a fixed structure 11, first and second pivoting shell
12 and
13, a sealing system (shown in FIG. 15), and first and second actuators 15 and
16.
The fixed structure 11, also called a jet pipe, is the structure that provides
the
9
CA 02445934 2003-10-21
support for the two pivoting shells 12 and 13, and for the actuators 15 and
16. The
fixed structure 11 cooperates radiaiiy and longitudinally with the two
pivoting shells
15 and 16 through a sealing arrangement that ensures fluid tightness between
the
respective elements.
With continued reference to FIG. 1, the rear (aft) end of the jet engine
generally designated 10, includes a jet pipe 11 in which 'two radial cutouts
25 and 26
are provided. The radial cutouts 25 and 26 are defined by the jet pipe
extensions 11'
(only one of which is shown as a result of the side view of the nozzle). The
first and
second pivoting shells 12 and 13 close the jet pipe cutouts 25 and 26, and are
pivotally mounted on said jet pipe 11 via shell hinge arms 14 and 14'. The
pivoting
shells 12 and 13 are shown in FIG. 1 to pivot about the same point. It is
appreciated,
however, that in an alternative embodiment, the pivoting shells 12 and 13 may
each
pivot about their own dedicated pivot points. The two pivoting shells 12 and
13, and
the jet pipe 11 form the exhaust nozzle of the engine.
Each of the pivoting shells 12 and 13 includes an external profile and an
internal profile. In FIG. 1, the external profile of the shells is shown to be
convergent
in the direction approaching the exhaust exit of the nozzle. The internal
profile of the
shells is also convergent, but to a lesser degree than the external profile.
The longitudinal axis of the engine 10 is indicated by the centerline 24. With
respect to this longitudinal axis, each of the shells 12 and 13 includes a
leading
edge that is contained in a plane substantially perpendicular to the engine
longitudinal axis and a longitudinal edge that is contained in a plane
substantially
parallel to a horizontal plane containing the engine longitudinal axis.
CA 02445934 2003-10-21
First and second independently operated actuators 15 and 16 connect the jet
pipe 11 to the first and second shells 12 and 13, respectively. In the
embodiment
shown in FIG. 1, the actuators 15 and 16 are connected to the shells 12 and 13
at a
point that is along the longitudinal edge of the shells. The actuators provide
the
motion necessary to pivot of the shells about the pivot points at which they
are
connected to the jet pipe. The pivoting of the shells may be symmetrical (as
shown
in FIGS. 3 and 4) to provide variation of the exhaust area, or asymmetrical
(as
shown in FIGS. 5 and 6) to provide thrust vectoring.
As also shown in FIG. 1, each shell 12 and 13 is connected to its own
actuator through an arm arrangement 17 and 18. One end 19 of the upper arm 17
is
pivotally connected to the first shell 12 while the other end of the arm 17 is
pivotally
connected to the cross head 20 of the first actuator 15 of the first shell.
One end 19'
of the lower arm 18 is pivotally connected to the second shell 13 while the
other end
of the arm 18 is pivotally connected to the cross head 20' of the second
actuator 16
of the second shell. The jet pipe 11 may be equipped with guiding rails 21 and
21'.
Each of the guiding rails engages its respective actuator cross head 20 and
20'. This
arrangement prevents any side loads in the piston rods 22 and 22' of the
actuators.
In this embodiment, each actuator 15 and 16 directly controls the position of
one
end of its respective arm 17 and 18, since the cross heads 20 and 20' are
respectively attached to the piston rods 22 and 22° of their respective
actuators 15
and 16.
With reference to FIGS. 2, 3, 4 and 7, the actuators 15 and 16, which control
the value of the area of the exhaust nozzle, are activated symmetrically to
provide
one method of operation. This causes the actuators to provide a symmetrical
11
CA 02445934 2003-10-21
rotation to the shells 12 and 13, so that the value of the exhaust area of the
nozzle
can be decreased as shown in FIG. 3 or increased as shown in FIG. 4. In these
cases, the thrust vector 23 remains aligned parallel with the engine
centerline 24.
With reference to FIG. 7 the mechanism which controls the pivoting of the
shells 12
and 13, as shown in FIGS. 2, 3 and 4, is composed of two identical independent
pairs of actuators 15, 115 and 16, 116. Each actuator is connected to its
respective
cross heads 20, 120, 20' and 120'. The cross heads 20, 120, 20' and 120' have
corresponding grooves 30, 30°, 130 and 130° that sfidably engage
guiding rails 21
and 21' (shown in FIG. 1) attached to the jet pipe 11. It is appreciated that
if the
structural rigidity of each of the shells 12 and 13 is great enough, the
actuators 115
and 116 may be eliminated and replaced by two arms and slats like the ones
shown
in F1G. 10. In such a case, the actuators would comprise the combination of
two
actuators 15, 16 as shown in FIG. 7, and the two arms 221, 223 guided by their
respective slots 226, 229 as shown in FIG. 10.
With reference to FIGS. 5 and 8, the actuators 15 and 16 may be activated
non-symmetrically to pivot the shells 12 and 13 clockwise to produce a down
thrust
vector, as shown. With reference to FIGS. 6 and 9, the actuators 15 and 16,
may be
activated non-symmetrically to pivot the shells 12 and 13 counter-clockwise to
produce an up thrust vector, as shown. It is apparent from FIGS. 7, 8 and 9
that the
same actuators (15, 115 and 16, 116) are capable of two different functions to
provide two methods of operation. One is to increase or decrease the value of
the
exhaust area of the exhaust nozzle without modification of the thrust vector
angle
(FIG. ?). The other one is to modify the angular position of the exhaust
nozzle, i.e,
12
CA 02445934 2003-10-21
providing it with a nozzle down position (FIGS. 5, 8) or a nozzle up position
(FIGS. 6,
9).
With reference to FIG. 10, a second embodiment of the invention is shown in
which like reference numerals refer to like elements. The difference between
the
embodiments shown in FIGS. 1 and 10 is that in the later embodiment the
actuators
215 and 216 are connected to the shells 212 and 213 at points along the
leading
edge of the shells, and the later embodiment shows a nozzle with an internal
convergent-divergent profile. The independent actuators 215 and 216 are
connected
to the jet pipe 11 through pivot connections 217 and 2'i9, respectively. The
actuators
215 and 216 are also connected to the shells 212 and 213 through pivot
connections 218 and 220. As with the embodiment shown in F1G. 1, pivoting may
be
symmetrical to provide variable exit nozzle areas as shown in FIGS. 13 and 14.
Alternatively, pivoting may be asymmetrical to vary the thrust vector angle as
shown
in FIGS. 11 and 12.
As also shown in FIG. 10, a first control arm 221 is pivotally connected to
the
first shell 212 through a pivot pin 222. A second control arm 223 is pivotally
connected to the second shell 213 through a pivot pin 224. Guide roller 225 is
pivotally connected to the end of the first control arm 221 and slidably
positioned in
the slot 226 in the guide bracket 227. The guide bracket 227 is connected to
the
extension arm 11' and its opposite (not shown) of fixed structure 11. The
guide roller
228 is pivotally connected to the end of second control arm 223 and slidably
positioned in the slot 229 in the guide bracket 227. The control arms 221 and
223
close the hoop loop between the two shells 212, 213, ensuring structural
integrity of
the assembly. The slots 226 and 229 define the pivoting iimits of the shells
212 and
13
CA 02445934 2003-10-21
213. In this embodiment, each shell 212, 213 directly controls the position of
its
respective arm 221, 223. The shells 212 and 213 are connected via the hinge
arms
214 and 214', respectively, to the same pivot point 214".
With reference to FIGS. 11 and 12 the actuators 215 and 216 can be
activated to control the angular position of the exhaust nozzle to rotate the
nozzle to
have a "nozzle up'° or a "nozzle down" position.
With reference to FIG. 15, fluid tightness between the shells and the fixed
structure is ensured by a sealing arrangement (symbolically shown) which is
typically
composed of a radial seal 31 mounted on each shell in the vicinity of their
leading
edge, a longitudinal seal 33 mounted along the edges of the jet pipe two
extending
arms, and a cylindrical seal 32 mounted on the jet pipe and connecting said
longitudinal seals to said radial seals. So long as the function of said seals
is not
impaired, further variation of the sealing arrangement can be made. For
example, all
seals including the radial seals can be installed on the fixed jet pipe, or
all seals can
be installed on the pivoting shells. Although any type of seal shape can be
used, it is
advantageous to minimize their size as well as to use a seal material
characterized
by a low friction capability (Teflon coated, composite or other).
With reference to FIG. 16, it is shown that the position of the actuators 15,
15°, 16, and 16° may be varied without departing from the
intended scope of the
invention. As indicated by showing the actuators as "black boxes," it is also
appreciated that each may be any type of actuator, such as hydraulic,
pneumatic or
electric actuators. While a hydraulic actuator is shown with a piston rod in
FIGS. 1
and 10, a screw type actuator can be used to provide the pivofing motion to
the
14
CA 02445934 2003-10-21
shells. A standard control system including a computer can be used to provide
controlled movement to the actuator systems during flight.
In the various embodiments of the present invention, the two shells 12 and 13
and 212 and 213 are pivotally mounted on two hinge clevises, each of said
clevises
being supported and attached to the fixed jet pipe, and substantially
diametrically
opposed. An independent actuator attached to the jet pipe controls each shell.
The
actuators can either be symmetrically or asymmetrically controlled. When the
actuators are symmetrically operated they provide a symmetrical rotation to
the
shells around their pivots. The two shells rotate away from one another to
cause the
value of the exhaust area of the nozzle to be increased or towards each other
to
cause the value of the exhaust area of the nozzle to be decreased. This
symmetrical
operation of the shells provides the variable nozzle area function of the
apparatus.
When each of the actuation means are operated in asymmetrically, the shells
rotate
around their pivots to provide an off-angle thrusf vector (whether it be up,
down, left,
or right). This asymmetrical operation of the shells provides the thrust
vectoring
function of the apparatus.
The pivoting shells allowing the execution of the nozzle area variation as
well
as the modification of the angle of the thrust vector in an upwards or
downwards
position are mounted on the jet pipe such that their hinge axis is
substantially
diametrical along the 3:00 o'clock-9:00 o'clock direction, It is appreciated,
however,
that the pivoting shells may be mounted side-by-side, such that their hinge
axis is
substantially diametrical along the 6:00 o'clock-12:00 o'clock direction. It
is further
appreciated that the pivoting shells may be mounted at any intervening angle
between the afore-described horizontal and vertical positions.
CA 02445934 2003-10-21
Variations in the type and location of the actuators used may be made without
departing from the scope and spirit of the present invention. For example,
linear,
gear driven, electro-mechanical, hydraulic, or pneumatic actuators may be used
without departing from the scope of the invention. Furthermore, variations in
the
shape and relative dimensions of the shells used may be made without departing
from the intended scope of the invention. For example, although it is expected
that
the preferred shape of the exhaust area of the nozzle will be circular, it is
also
appreciated that non-circular areas may be used in some circumstances without
departing from the scope of the present invention. Thus, this application and
the
appended claims are intended to cover any and all variations, modifications
and
adaptations as may fall within the spirit of the invention.
16
