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 engine.
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; and 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 auxiliary outlet itself is no longer utilized following takeoff operation, and may introduce base drag thereat during the remainder of the aircraft flight, including the typically long duration cruise operation.
Accordingly, it is desired to obtain the various benefits of using the confluent variable exhaust nozzle, while further improving the performance thereof, including the reduction of any base drag attributable thereto during operation.
An exhaust nozzle includes an outer duct surrounding an inner duct. The inner duct includes a main outlet, and a row of apertures spaced upstream therefrom. The outer duct includes a row of intakes at a forward end, an auxiliary outlet at an aft end, and surrounds the inner duct over the apertures to form a bypass channel terminating at the auxiliary outlet. A row of flaps are hinged at upstream ends to selectively cover and uncover the apertures for selectively bypassing a portion of exhaust flow from the inner duct through the outer duct in confluent streams from both main and auxiliary outlets. When the flaps cover the apertures, the intakes ventilate the bypass channel and discharge flow through the auxiliary outlet.
The invention, in accordance with preferred and exemplary embodiments, together with further objects and advantages thereof, is more particularly described in the following detailed description taken in conjunction with the accompanying drawings in which:
Illustrated in
The engine includes an annular fan nacelle 16 surrounding a fan 18 which is powered by a core engine surrounded by a core nacelle or cowl 20. The core engine includes in serial flow communication a multistage axial compressor 22, an annular combustor 24, a high pressure turbine 26, and a low pressure turbine 28 which are axisymmetrical about a longitudinal or axial centerline axis 30.
During operation, ambient air 32 enters the fan nacelle and flows past the fan blades into the compressor 22 for pressurization. The compressed air is mixed with fuel in the combustor 24 for generating hot combustion gases 34 which are discharged through the high and low pressure turbine 26,28 in turn. The turbines extract energy from the combustion gases and power the compressor 22 and fan 18, respectively.
A majority of air is pressurized by the driven fan 18 and bypasses the core engine through a substantially annular bypass duct 36 which terminates in a fan exhaust nozzle 38 for producing a substantial portion of the propulsion thrust which powers the aircraft in flight. The combustion gases 34 are exhausted from the aft outlet of the core engine for providing additional thrust.
The fan nacelle includes radially outer and inner cowlings or skins 40,42 which extend axially from a leading edge of the nacelle defining an annular inlet 44 to an opposite trailing edge defining an annular outlet 46. 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 pylon 14 for being opened during maintenance operation.
The exemplary fan nacelle illustrated in
In the exemplary embodiment illustrated in
The fan nozzle 38 illustrated in
An annular outer duct 50 is disposed at the aft end of the fan nacelle coextensive with the outer skin 40 for maintaining an aerodynamically smooth outer mold line (OML) or outer surface of the nacelle having minimal aerodynamic drag. As initial shown in
An auxiliary outlet 54 is disposed at the aft end of the outer duct concentric about the fan bypass duct 36. As shown in
A plurality of doors or flaps 58 are hinged at upstream ends thereof to selectively cover and uncover corresponding ones of the apertures 48 and selectively bypass a portion of the exhaust flow 32 from the inner duct 36 through the outer duct 50 in confluent streams from both the main and auxiliary outlets 46,54.
In this way, the auxiliary outlet 54 provides a temporary increase in the overall discharge flow area for the fan bypass air 32 specifically during takeoff operation of the aircraft. The increased flow area of the main and auxiliary outlets 46,54 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 duct 50 energizes the ambient airflow 32 outside 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 outlet 46, which in turn reduces the differential velocity and shearing between the two confluent streams for further enhancing noise attenuation.
The individual flaps 58 illustrated in
The actuators 58 are preferably passive devices without the need for external power, which is effected by including an internal spring in each actuator which biases the corresponding output rods thereof in their extended positions.
The internal springs in each actuator may be suitably sized for permitting each of the flaps to open and uncover the apertures under differential pressure between the inner and outer ducts 36,50. Since the fan exhaust 32 has a substantial pressure during operation, this pressure is exerted over the inner surfaces of the several flaps 58 which tends to deploy them open.
However, the closing force effected by the actuators may be predetermined to maintain closed the flaps 58 until sufficient pressure is developed in the fan exhaust 32 to overcome the closing spring force and open the flaps during takeoff operation at relatively high power and air pressure. Correspondingly, the pressure of the fan exhaust during cruise operation is relatively lower which will permit the spring actuators to re-close the flaps for cruise operation.
As shown in
The kinematic dimensions and angular positions of the actuator and the sliding link are selected for pulling open each flap 58 as shown in
The actuator 60 may be joined to the corresponding flaps in various manners other than those illustrated in
As illustrated in
The radial and longitudinal frames cooperate together to provide structural support for introduction of the row of apertures 48, while supporting the outer duct 50 and the row of intakes 52 provided therein. The longitudinal frames 66 are preferably imperforate to prevent crossflow between the circumferentially adjacent apertures 48 and to confine exhaust flow rearwardly through the corresponding bypass channels 56 disposed between the row of longitudinal frames 66.
As illustrated in
As illustrated in
Correspondingly, the outer and inner ducts 50,36 converge aft toward the respective outlets thereof to provide concentric and confluent exhaust flow discharge when the flaps are open. The internal bypass channels 56 preferably also converge aft to the auxiliary outlet 54. And, that auxiliary outlet 54 provides a local interruption in the aerodynamic continuity of the outer skin of the fan nacelle between the auxiliary outlet 54 and the main outlet 46.
The auxiliary outlet 54 preferably smoothly blends with the outer skin downstream therefrom for providing an aerodynamically smooth transition for both the fan exhaust 32 channeled through the bypass channels 56 when the flaps are open, and the external freestream airflow 32 channeled through the intakes 52 when the flaps are closed. Both the fan exhaust and the ambient ventilation air are commonly channeled through the bypass channels 56 for discharge from the same auxiliary outlet 54 during operation, but at different times.
As indicated above, fan exhaust discharge through the auxiliary outlet 54 energizes the freestream ambient airflow thereover, while decreasing the relative velocity between ambient freestream and the fan exhaust at the main outlet 46. When the flaps 58 are closed, some of the ambient freestream airflow enters the intakes 52 for ventilating the bypass channels 56 and reducing the base drag in the region downstream of the auxiliary outlet 54.
As shown in
The intakes 52 may have any suitable shape such as the triangular shape illustrated in
Furthermore, the intakes 52 are preferably in the form of channels or troughs inclined inwardly toward the respective bypass channels 56 as illustrated in
As shown in
In the exemplary embodiment illustrated in
By maintaining the continuity of the outer skin 40, local interruptions therein may be minimized for further minimizing associated aerodynamic drag during operation. The intakes 52 have proven NACA-profiles for efficiently ventilating the bypass channels 56 with minimal drag along the outer skin. Correspondingly, the multitude of auxiliary outlet holes 54B formed in the otherwise flat and continuous surface of the outer skin 40 also minimize aerodynamic drag during operation.
The ventilated confluent 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,
As shown in
The exemplary thrust reverser 70 illustrated in
The ventilated confluent exhaust nozzle disclosed above may be suitably incorporated into the aft end of the long duct turbofan engine illustrated in
During takeoff operation of the engine as illustrated in
The various embodiments of the ventilated confluent 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.
In
In the
The flaps in the embodiments 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.
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.
This application claims the benefit of U.S. Provisional Application No. 60/449,082; filed Feb. 21, 2003.
Number | Name | Date | Kind |
---|---|---|---|
3779010 | Chamay et al. | Dec 1973 | A |
3820719 | Clark | Jun 1974 | A |
4291782 | Klees | Sep 1981 | A |
4501393 | Klees et al. | Feb 1985 | A |
4922712 | Matta et al. | May 1990 | A |
4922713 | Barbarin et al. | May 1990 | A |
5181676 | Lair | Jan 1993 | A |
5221048 | Lair | Jun 1993 | A |
5655360 | Butler | Aug 1997 | A |
5694767 | Vdoviak et al. | Dec 1997 | A |
5778659 | Duesier et al. | Jul 1998 | A |
5779192 | Metezeau et al. | Jul 1998 | A |
5819527 | Fournier | Oct 1998 | A |
5826823 | Lymons et al. | Oct 1998 | A |
5853148 | Standish et al. | Dec 1998 | A |
5863014 | Standish | Jan 1999 | A |
5875995 | Moe et al. | Mar 1999 | A |
5908159 | Rudolph | Jun 1999 | A |
5913476 | Gonidec et al. | Jun 1999 | A |
5934613 | Standish et al. | Aug 1999 | A |
6070407 | Newton | Jun 2000 | A |
6101807 | Gonidec et al. | Aug 2000 | A |
6751944 | Lair | Jun 2004 | B1 |
Number | Date | Country | |
---|---|---|---|
20050188676 A1 | Sep 2005 | US |
Number | Date | Country | |
---|---|---|---|
60449082 | Feb 2003 | US |