Rotary adjustable exhaust nozzle

An exhaust nozzle includes an exhaust duct with an outlet and a row of radial apertures upstream therefrom. A radial frame surrounds the duct upstream from the apertures. A row of flaps are hinged to the frame to selectively cover and uncover the apertures for controlling exhaust flow discharged therethrough. An arcuate unison bar surrounds the duct adjacent to the frame and includes circumferentially spaced apart cams engaging corresponding cam followers affixed to the flaps. An actuator is joined to the bar for selective rotation thereof between opposite first and second directions to pivot open and closed the flaps atop the apertures.

BACKGROUND OF THE INVENTION

The present invention relates generally to turbofan aircraft engines, and, more specifically, to exhaust nozzles therefor.

A typical turbofan aircraft engine includes a fan powered by a core engine. The core engine includes a surrounding cowl or nacelle, and the fan includes a corresponding cowl or nacelle at the forward end of the core engine which extends aft either in part or fully thereover.

The fan nacelle is spaced radially outwardly from the core nacelle to define an annular bypass duct therebetween. During operation, the core engine powers the fan which pressurizes ambient air to produce propulsion thrust in the fan air bypassing the core engine and discharged from the fan exhaust nozzle.

A portion of the fan air is channeled into the core engine wherein it is pressurized and mixed with fuel for generating hot combustion gases. Energy is extracted from the combustion gases in high and low pressure turbines which in turn power a compressor and the fan. The core exhaust gases are discharged from the core engine through a core exhaust nozzle and provide additional thrust for propelling the aircraft in flight.

In a typical short fan nacelle, the fan nozzle is spaced upstream from the core nozzle, and the fan exhaust is discharged separately from and surrounding the core exhaust. In a long nacelle, the fan nacelle extends aft of the core nozzle to provide a single common nozzle through which both the fan bypass air and core exhaust are discharged from the engine.

The fan nozzle and the core nozzle are typically fixed area nozzles, although they could be configured as variable area nozzles. Variable area nozzles permit adjustment of the aerodynamic performance of the engine which correspondingly increases complexity, weight, and cost of the nozzle.

Furthermore, turbofan aircraft engines typically include thrust reversers for use in providing braking thrust during landing of the aircraft. Various types of thrust reversers are found in the engine nacelle and further increase complexity, weight, and cost of the engine.

In U.S. Pat. No. 6,751,944 entitled “Confluent Variable Exhaust Nozzle,” assigned to the present assignee, and incorporated herein by reference, an improved variable area exhaust nozzle is disclosed for a turbofan aircraft engine. The confluent nozzle includes outer and inner conduits, with a plurality of flaps therebetween. The flaps may be selectively opened to bypass a portion of exhaust flow from the inner conduit through the outer conduit in confluent exhaust streams from concentric main and auxiliary exhaust outlets.

In this way, the auxiliary outlet may be operated during takeoff operation of the aircraft for temporarily increasing exhaust flow area for correspondingly reducing velocity of the exhaust flow. Noise may therefore be reduced during takeoff operation using a relatively simple and compact variable area configuration.

However, the multiple flaps must be opened and closed in unison, and against the substantial pressure forces generated by the exhaust flow during operation. The actuation system for deploying and retracting the flaps must provide sufficient strength for carrying loads during operation, and must be contained within the available space provided in the nacelle without degrading aerodynamic performance or efficiency of the engine.

Accordingly, it is desired to provide an improved actuation system for deploying and retracting the row of flaps in unison during operation.

BRIEF SUMMARY OF THE INVENTION

An exhaust nozzle includes an exhaust duct with an outlet and a row of radial apertures upstream therefrom. A radial frame surrounds the duct upstream from the apertures. A row of flaps are hinged to the frame to selectively cover and uncover the apertures for controlling exhaust flow discharged therethrough. An arcuate unison bar surrounds the duct adjacent to the frame and includes circumferentially spaced apart cams engaging corresponding cam followers affixed to the flaps. An actuator is joined to the bar for selective rotation thereof between opposite first and second directions to pivot open and closed the flaps atop the apertures.

DETAILED DESCRIPTION OF THE INVENTION

Illustrated inFIG. 1is a turbofan aircraft gas turbine engine10suitably mounted to the wing12of an aircraft by a supporting pylon14. Alternatively, the engine could be mounted to the fuselage of the aircraft if desired.

The engine includes an annular fan nacelle16surrounding a fan18which is powered by a core engine surrounded by a core nacelle or cowl20. The core engine includes in serial flow communication a multistage axial compressor22, an annular combustor24, a high pressure turbine26, and a low pressure turbine28which are axisymmetrical about a longitudinal or axial centerline axis30.

During operation, ambient air32enters the fan nacelle and flows past the fan blades into the compressor22for pressurization. The compressed air is mixed with fuel in the combustor24for generating hot combustion gases34which are discharged through the high and low pressure turbine26,28in turn. The turbines extract energy from the combustion gases and power the compressor22and fan18, respectively.

A majority of air is pressurized by the driven fan18and bypasses the core engine through a substantially annular bypass duct36which terminates in a fan exhaust nozzle38for producing a substantial portion of the propulsion thrust which powers the aircraft in flight. The combustion gases34are exhausted from the aft outlet of the core engine for providing additional thrust.

The fan nacelle includes radially outer and inner cowlings or skins40,42which extend axially from a leading edge of the nacelle defining an annular inlet44to an opposite trailing edge defining an annular outlet46. The fan nacelle may have any conventional configuration, and is typically formed in two generally C-shaped halves which are pivotally joined to the supporting pylon14for being opened during maintenance operation.

The exemplary fan nacelle illustrated inFIG. 1is a short nacelle terminating near the middle of the core engine for discharging the pressurized fan airflow separately from and surrounding the exhaust flow34discharged from the aft outlet of the core engine. In alternate embodiments, the fan nacelle could be long and extend downstream of the core engine for providing a single, common outlet for both the fan air and the core exhaust.

In the exemplary embodiment illustrated inFIG. 1, the core engine is mounted concentrically inside the fan nacelle by a row of supporting struts in a conventional manner. The core cowl20is spaced radially inwardly from the inner skin42of the fan nacelle to define the bypass duct36therebetween which bypasses the major portion of the fan air around the core engine during operation. The fan bypass duct terminates in the annular, or partly annular fan nozzle38at the nacelle trailing edge or outlet46.

The fan nozzle38illustrated inFIG. 1is configured for variable area performance for reducing exhaust noise during aircraft takeoff operation. The variable fan nozzle38is illustrated in more detail inFIGS. 2–4and includes the aft portion of the bypass duct36which defines an inner duct within the fan nacelle having the main outlet46at the aft end thereof. Spaced upstream from the main outlet46is a row of circumferentially spaced apart, radial inlet apertures48.

An annular outer duct50is disposed at the aft end of the fan nacelle coextensive with the outer skin40for maintaining an aerodynamically smooth outer mold line (OML) or outer surface of the nacelle having minimal aerodynamic drag. An auxiliary outlet52is disposed at the aft end of the outer duct concentric about the fan bypass duct36. As shown inFIGS. 3 and 4, the outer duct50is spaced radially outwardly from and surrounds the inner duct36over the row of apertures48to form a bypass channel54which begins at the apertures48and terminates at the outlet52.

A plurality of doors or flaps56are hinged at upstream ends thereof to selectively cover and uncover corresponding ones of the apertures48and selectively bypass a portion of the exhaust flow32from the inner duct36through the outer duct50in confluent streams from both the main and auxiliary outlets46,52.

In this way, the auxiliary outlet52provides a temporary increase in the overall discharge flow area for the fan bypass air32specifically during takeoff operation of the aircraft. The increased flow area of the main and auxiliary outlets temporarily reduces the velocity of the fan exhaust and therefore reduces the associated noise therefrom.

Furthermore, bypassing a portion of the fan exhaust through the outer duct50energizes the ambient airflow32outside the nacelle and reduces the thickness of the associated boundary layer. In this way, the external ambient air is locally accelerated in velocity where it meets the higher velocity fan exhaust discharged from the main outlet46, which in turn reduces the differential velocity and shearing between the two confluent streams for further enhancing noise attenuation.

FIG. 3illustrates the open flaps56for bypassing a portion of the fan exhaust32from the inner duct36through the outer duct50during takeoff operation.FIG. 4illustrates the flaps56closed in their respective apertures48after takeoff operation, with the entirety of the fan exhaust32being discharged through the inner duct36and the main outlet at the aft end thereof.

As illustrated inFIGS. 5 and 6, the fan nozzle preferably includes a radial frame58which extends circumferentially between the outer and inner ducts immediately forward of the row of apertures48. The individual flaps56are suitably hinged at their upstream ends to the radial frame58. A plurality of longitudinal frames60extend axially rearwardly from the radial frame, and are disposed circumferentially between corresponding ones of the apertures48. The longitudinal frames are tapered thinner in the aft direction to match the contour of the outer duct50which converges in the aft direction.

The radial and longitudinal frames cooperate together to provide structural support for introduction of the row of apertures48, while supporting the outer duct50and the row of flaps. The longitudinal frames60are preferably imperforate to prevent crossflow between the circumferentially adjacent apertures48and to confine exhaust flow rearwardly through the corresponding bypass channels54disposed between the row of longitudinal frames60.

As best illustrated inFIG. 6, each of the flaps56is pivotally joined at forward ends thereof to the radial frame58by a pair of circumferentially spaced hinges62. The hinges may have any suitable configuration such as devises fixedly mounted to the radial frame and rotatably joined to flanges extending from the outer surface of the flaps, with hinge pins or bolts therebetween.

Each flap56also includes a generally L-shaped or gooseneck control arm64extending radially outwardly from the outer surface thereof between the two hinges. The control arm64is fixedly joined to or integral with the flap56and extends in part radially outwardly therefrom and in part axially forwardly through a corresponding access aperture in the radial frame.

As initially shown inFIGS. 5 and 6the distal end of the control arm64where it passes through the radial frame58includes a cam follower66affixed thereto. For example, the cam follower66may be in form of a cam roller or wheel rotatably mounted to the distal end of the control arm64by a corresponding pin or bolt suitably joined thereto.

The flaps56extend aft from the aft side of the radial frame as illustrated inFIGS. 5 and 6and may pivot open and closed around their corresponding hinges62. This is effected by a circumferentially arcuate unison or control bar68mounted circumferentially around the inner duct36adjacent to the forward side of the radial frame.

As shown inFIGS. 5 and 7, the control bar includes a plurality of radial cams70spaced circumferentially apart in preferably radial engagement with corresponding ones of the cam followers66affixed to the several flaps56.

Means in the form of a linear actuator72are operatively joined to the control bar68for selectively rotating the bar in a first clockwise direction illustrated inFIG. 7to pivot or deploy open the full row of flaps56in unison about their corresponding hinges. The actuator72may be operated in reverse to rotate the bar in an opposite second or counterclockwise direction also illustrated inFIG. 7to pivot or retract closed the full row of flaps56.

When the flaps56are closed as illustrated inFIG. 4, they cover the respective apertures48and block discharge of the exhaust flow32therethrough. When the flaps56are open as illustrated inFIG. 3, the aperture48are open for permitting bypass of a portion of the exhaust flow32through the respective bypass channels54and out the auxiliary outlet52.

The common unison bar68therefore permits synchronous deployment and retraction of the row of flaps56when desired by the simple circumferential rotation or rotary movement of the control bar68itself. The corresponding cam followers66on each of the control arms64maintain engagement or contact with the common control bar68for coordinating the simultaneous movement of the several flaps.

An exemplary one of the radial cams70is illustrated in more detail inFIG. 7, and is in the preferred form of a radial incline or ramp extending circumferentially along a corresponding portion of the outer perimeter of the control bar68. The several cams70along the outer perimeter of the common control bar are preferably identical to each other, and each similarly varies in radial height from low to high.

The low cam height relative to the axial centerline axis of the bypass duct positions the corresponding cam followers66radially inwardly as further illustrated inFIG. 3to pivot open the row of flaps radially outwardly. In contrast, the high cam height positioning of the cam followers66as additionally illustrated inFIG. 4raises those followers radially outwardly to pivot closed the row of flaps radially inwardly.

The slope of the ramp may be selected to balance actuator stroke and actuator force. Shallow slope may be used to decrease actuator force with increased mechanical advantage, but with an increase in actuator stroke. Steeper slope may be used to decrease actuator stroke, but with increased actuator force due to decreased mechanical advantage.

In this way, the simple rotary movement of the control bar68illustrated inFIG. 5permits simultaneous deployment and retraction of the row of flaps56with relatively few actuation components contained in a small or compact space within the outer and inner skins of the fan nacelle and closely adjacent to the flaps themselves. Furthermore, the radial cams70enjoy substantial mechanical advantage or leverage for retracting closed the row of flaps56even against the substantial pressure forces acting along the inner surfaces thereof by the pressurized exhaust flow being discharged during operation.

Correspondingly, the actuator72requires low actuation forces to turn the actuation control bar38. And, the radial frame58not only locally increases the strength of the fan nacelle around the row of radial apertures48, but also increases the strength of the fan nacelle directly adjacent to the control bar68which carries actuation forces circumferentially therethrough during operation.

In the exemplary embodiment illustrated inFIG. 7, each of the cams70includes a local up-step or low detent74at the base of the cam ramp70itself at the low cam height position. The ramp70increases in radial height smoothly from the low step74at its base to a corresponding down-step or high detent76at the top of the ramp followed by the high cam height portion thereof.

In this way, when the flaps are initially closed for a majority of operation of the engine, the cam follower66is located on the high cam land illustrated in phantom line inFIG. 7and locks closed the corresponding flap associated therewith. In order to open those closed flaps, the control bar68is rotated clockwise inFIG. 7which requires the application of additional closing force on the cam follower66as it rises slightly to overcome the low step76, now acting as an up-step in reverse motion. This additional closing movement of the corresponding flap may be permitted by introducing corresponding resiliency in a flexible seal mounted between the flap and its seat around the radial aperture.

As the control bar68is further rotated clockwise inFIG. 7the cam roller66is then permitted to travel radially inwardly as the height of the ramp70decreases until reaching the base of the ramp at which the local high step74is located. In this position, the cam follower66is located radially inwardly which pivots radially outwardly the corresponding flap to its fully open position.

In order to close the open flaps, the control bar68is pulled counterclockwise inFIG. 7by its actuator72to force the cam follower66radially outwardly as it rides along the increasing height of the cam ramp70. An initial increase in actuation force is required in the actuator72to lift the cam follower66over the initial low step74at the base of the cam to unlock the flaps from their locked open positions.

Accordingly, both the low step74and the high step76provide local locking of the flaps in their closed and opened positions, respectively, and therefore the actuator72need not be energized in these two locked positions. Furthermore, separate locks for locking the flaps in their opposite closed and opened positions are not required, but may be introduced for redundancy.

And, if desired, the control bar68may be positioned by its actuator72at any intermediate circumferential position along the length of the cam ramp70for positioning the flaps at variable pivoted positions between their closed and opened positions for further varying discharge flow area of the fan nozzle.

As illustrated inFIG. 5, the unison bar68is preferably mounted to the perimeter of the inner duct36for rotary movement therearound by a plurality of radially outer and inner rollers or wheels78,80spaced circumferentially apart from each other. The outer wheels78may be suitably rotatably mounted to the radial frame58and suspended radially outwardly above the perimeter of the control bar68between the radial cams. Correspondingly, each of the inner wheels80may be suitably mounted to the external surface of the inner duct36in corresponding brackets or devises fixedly mounted thereto.

The outer and inner wheels78,80illustrated inFIG. 5may be in the form of typical pulleys with annular grooves therein which are complementary with the shape of the control bar68for both radially and axially trapping the bar to limit its motion to circumferential rotary or arcuate movement around the inner ducts36. The control bar68may have a radially tall, rectangular configuration for increasing its strength or moment of inertia in the radial direction, with the outer perimeter or edge of the bar being trapped by the outer wheels78, and the inner edge of the bar being trapped by the inner wheels80.

The distal end of the control bar68is illustrated inFIG. 5as being freely supported and unattached without restraint due to the several outer wheels and several inner wheels which collectively support the full circumferential extent of the control bar68around the circumference of the inner duct. As indicated above, the fan nacelle my be formed in two generally C-halves and, therefore two arcuate control bars68would be used for the two sides of the full nacelle, each control bar with its separate actuator72.

In the preferred embodiment illustrated inFIG. 5, a single actuator72is suitably joined to the proximal end of the corresponding control bar68, with the circumferentially opposite distal end of the bar being free, or freely supported or suspended from the outer and inner wheels.

The exemplary linear actuator72illustrated inFIGS. 5 and 7may have any conventional configuration such as hydraulic, pneumatic, or electrical, with an elongate output rod82suitably joined to the proximal end of the control bar68by a typical spherical rod end for example.

The actuator72is suitably configured to extend the output rod82to rotate the control bar in the first or clockwise direction, and then to retract the rod to rotate the bar in the opposite second or counterclockwise direction. Little stroke or range of extension and retraction of the output rod82is required between the closed and open positions of the flaps in view of the kinematic operation of the respective cams70with their followers66mounted on the control arms64.

As best illustrated inFIGS. 3 and 4, the cam rollers66are axially elongate to maintain rolling contact with the unison bar68as the flaps pivot open and closed in response to rotary movement of the unison bar around the bypass duct. The rotary movement of the control bar68circumferentially around the axial centerline axis of the fan nozzle is converted by the radial cams and followers to pivotal movement of the several flaps56around their respective hinges having rotary axes which are orthogonal to the rotary axis of the control bar.

As shown inFIGS. 3 and 7, the cam followers66are unrestrained radially outwardly from the unison bar68, and the flaps56are hinged to the radial frame58to permit pressure force F of the exhaust flow inside the inner duct36to power open the flaps as the unison bar is rotated in the first direction. As initially shown inFIG. 4, the radial cam70is positioned at its maximum radial height to drive or force the cam follower66radially outwardly and correspondingly force the control arm64and its corresponding flap56radially inwardly to the closed position around the hinges62.

In order to open the flaps56as illustrated inFIG. 3, the radial cam70is driven towards its radially inner position of minimal height which then permits the pressure force F acting over the inner surface of the flaps56to drive those flaps radially outwardly, which in turn drives the corresponding cam followers66atop the radial cam70. The substantial pressure forces F, alone, of the exhaust flow32are sufficient to maintain opened the flaps56while also maintaining engagement of the cam followers66on their respective radial cams70.

However, when the engine is powered off on the ground, the fan discharge is terminated and no pressure forces are available for opening the flaps. If the control bar68is driven to its open position, only those flaps which are upside down relative to gravity would then open by the gravitational forces thereon.

Accordingly,FIG. 8illustrates an alternate embodiment in which the control bar68is slightly modified to include a plurality of corresponding retainer tracks84spaced above respective ones of the radial cams to define corresponding slots therewith in which the corresponding cam follower66is additionally trapped or restrained radially inwardly. The track84is an integral part of the control bar68and is generally parallel to the radial cam70between its low and high heights.

In this way, the control bar68operates in the same manner disclosed above to open and close the flaps during operation of the engine. And, the introduction of the retaining track84permits the actuator to drive or power open the flaps irrespective of any pressure forces in the exhaust flow.

InFIG. 8, as the actuator rod82pushes the control bar68to the right in the clockwise direction, force is transferred from the actuator through the retainer track84to drive radially inwardly the cam follower66, which in turn pivots open the corresponding flap attached to the control arm64.

FIGS. 9 and 10illustrate yet another embodiment of the actuation system which is identical to that illustrated inFIG. 5, for example, but additionally includes a plurality of deployment or tension springs86suitably mounted between respective ones of the cam followers66and the inner duct36to restrain the cam followers radially inwardly irrespective of any pressure forces of the exhaust flow in the inner duct. Each tension spring86is suitably mounted at its outer end by a bracket or hook attached to the common bolt supporting the cam follower66, and at its inner end to another bracket or hook fixedly joined to the outer surface of the inner duct36.

In this way, the tension spring86may be stretch-mounted between the cam follower and the inner duct for biasing open the flaps56when the radial cam70is at its low height position as shown inFIG. 9, and being further stretched in the closed position of the flaps56when the radial cams are at their high positions. Portions of flexible seals96in seats surrounding the apertures are shown which seal closed the flaps, and also permit initial super-closing of the flaps by the high step76shown inFIG. 7as described above.

In the various embodiment illustrated inFIGS. 1–10, the rotary actuation system is introduced in the fan nozzle38in which the outer duct50surrounds the inner exhaust duct36to form the bypass channel54extending aft from the apertures48and terminating at the auxiliary outlet52for providing variable area operation thereof for the benefits disclosed.

The rotary adjustable exhaust nozzle disclosed above may be used in various turbofan engines with a long or short fan nacelles. And, the nozzle may be used in engines with or without thrust reversers.

For example,FIG. 11illustrates another turbofan engine10B in which the fan nacelle16B extends the full length of the engine to a common exhaust outlet88at the aft end thereof. The fan bypass duct36terminates inside the engine upstream from the common outlet88for mixing the fan exhaust with the core exhaust inside the engine and upstream from the common outlet. A thrust reverser90is located upstream from the common outlet and includes a pair of thrust reverser doors92covering corresponding side openings in the engine.

As shown inFIG. 12, a pair of actuators94are disposed on opposite sides of the engine for providing means to selectively open the doors to uncover the side openings for reversing thrust from the combined fan exhaust and core engine exhaust during landing operation.

The exemplary thrust reverser illustrated inFIG. 12may have any conventional configuration, and includes integral forward and aft barrels which define an inner duct integrally joined together by lateral beams defining the two side openings which are covered by the two doors92. The inner duct receives the exhaust from both the core engine and the fan bypass duct.

The rotary adjustable exhaust nozzle disclosed above may be suitably incorporated into the aft end of the long duct turbofan engine illustrated inFIGS. 11 and 12. For example, the outer duct50is introduced as the aft end of the nacelle16B which forms a smooth outer mold line with the forward barrel and doors when stowed closed. The inlet apertures48are formed in the inner duct and are closed by the flaps56located between the inner and outer ducts in the same manner described above in the first embodiment.

During takeoff operation of the engine as illustrated inFIG. 11, the thrust reverser doors are locked closed and flush in the nacelle, and the flaps may be selectively opened for temporarily increasing the total exhaust flow area from the engine by introducing the additional area from the auxiliary outlet52surrounding the common outlet88.

The various embodiments of the exhaust nozzle disclosed above permit a temporary increase in total exhaust flow area during takeoff operation of the engine for reducing the differential velocity between the ambient freestream airflow and the engine exhaust.

InFIG. 1, the introduction of the confluent fan nozzle decreases the differential velocity between the fan air and the ambient freestream airflow for attenuating noise during takeoff operation, while minimizing base drag during cruise operation.

In theFIG. 11embodiment, the confluent exhaust nozzle decreases the differential velocity between the common exhaust flow and the ambient freestream air for also attenuating noise during takeoff operation.

The flaps and the rotary actuation system therefor as disclosed above are fully contained between the outer and inner skins of the nacelle and occupy little space, introduce little additional weight, and are relatively simple to incorporate in the available limited space.