Abstract:
An assembly for pivoting a flap according to an exemplary aspect of the present disclosure includes, among other things, a structure is mounted at least partially around an axis. The structure is attached to a pivotable flap arranged to define a nozzle area. A cable passes through an orifice defined by the flap. An actuator system is operable to mechanically retract the cable therein to lessen the nozzle area and mechanically extend the cable to enable the flow to increase the nozzle area. The actuator system is engaged with the cable. A segment of the cable, opposite the actuator system, is attached to a fixed structure. A method of providing a variable fan exit area is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/441,562, filed Mar. 17, 2009, which is a National Phase Application of PCT Application No. PCT/US06/39049 filed on Oct. 12, 2006. 
     
    
     BACKGROUND 
       [0002]    The present invention relates to a gas turbine engine, and more particularly to a turbofan gas turbine engine having a cable driven fan variable area nozzle structure within the fan nacelle thereof. 
         [0003]    Conventional gas turbine engines include a fan section and a core engine with the fan section having a larger outer diameter than that of the core engine. The fan section and the core engine are disposed sequentially about a longitudinal axis and are enclosed in a nacelle. An annular path of primary airflow passes through the fan section and the core engine to generate primary thrust. 
         [0004]    Combustion gases are discharged from the core engine through a primary airflow path and are exhausted through a core exhaust nozzle. An annular fan flow path, disposed radially outwardly of the primary airflow path, passes through a radial outer portion between a fan nacelle and a core nacelle and is discharged through an annular fan exhaust nozzle defined at least partially by the fan nacelle and the core nacelle to generate fan thrust. A majority of propulsion thrust is provided by the pressurized fan air discharged through the fan exhaust nozzle, the remaining thrust provided from the combustion gases is discharged through the core exhaust nozzle. 
         [0005]    The fan nozzles of conventional gas turbine engines have fixed geometry. The fixed geometry fan nozzles are suitable for take-off and landing conditions as well as for cruise conditions. However, the requirements for take-off and landing conditions are different from requirements for the cruise condition. Optimum performance of the engine may be achieved during different flight conditions of an aircraft by varying the fan exhaust nozzle for the specific flight regimes. 
         [0006]    Some gas turbine engines have implemented fan variable area nozzles. The fan variable area nozzle provides a smaller fan exit nozzle diameter during cruise conditions and a larger fan exit nozzle diameter during take-off and landing conditions. The existing variable area nozzles typically utilize relatively complex mechanisms that increase engine weight to the extent that the increased fuel efficiency benefits gained from fan variable area nozzle are negated. 
         [0007]    Accordingly, it is desirable to provide an effective, lightweight fan variable area nozzle for a gas turbine engine. 
       SUMMARY 
       [0008]    A nacelle assembly for a gas turbine engine according to an example of the present disclosure includes a core nacelle defined about an axis for allowing flow to pass therethrough. A fan nacelle is mounted at least partially around the core nacelle. The fan nacelle has a fan variable area nozzle that defines a fan exit area between the fan nacelle and the core nacelle. The nozzle has a plurality of pivotable flaps pivotable about a pivot defined by each of the flaps. A cable passes through an orifice defined by at least one of the flaps. An actuator system is operable to mechanically retract the cable therein pivoting at least one of the flaps about the pivot to lessen the fan exit area and mechanically extend the cable to enable the flow to pivot at least one of the flaps about the pivot and increase the fan exit area. The actuator system is engaged with the cable. A segment of the cable, opposite the actuator system, is attached to a fixed structure. 
         [0009]    In a further embodiment of any of the foregoing embodiments, there is one actuator system for the plurality of flaps. 
         [0010]    In a further embodiment of any of the foregoing embodiments, the actuator system includes a spool configured to spool and unspool the cable. 
         [0011]    In a further embodiment of any of the foregoing embodiments, spooling of the cable around the spool decreases the fan nozzle exit area. 
         [0012]    In a further embodiment of any of the foregoing embodiments, unspooling of the cable around the spool increases the fan nozzle exit area. 
         [0013]    In a further embodiment of any of the foregoing embodiments, the cable is strung through one of the plurality of flaps intermediate a first fixed structure of the fan nacelle and a second fixed structure of the fan nacelle. 
         [0014]    In a further embodiment of any of the foregoing embodiments, the first fixed structure of the fan nacelle and the second fixed structure of the fan nacelle include a rib of the fan nacelle. 
         [0015]    In a further embodiment of any of the foregoing embodiments, the fan variable area nozzle includes a multiple of flap sets. Each of the flap sets is separately driven by a respective cable and actuator of the actuator system to adjust the fan variable area nozzle. 
         [0016]    In a further embodiment of any of the foregoing embodiments, each flap set corresponds to a circumferential sector of the fan variable area nozzle. 
         [0017]    In a further embodiment of any of the foregoing embodiments, there are four circumferential sectors. 
         [0018]    In a further embodiment of any of the foregoing embodiments, a gear system is driven by a core engine. A fan is driven by the gear system about the axis. 
         [0019]    In a further embodiment of any of the foregoing embodiments, the actuator system includes an electromechanical actuator. 
         [0020]    In a further embodiment of any of the foregoing embodiments, the actuator system comprises a rotary hydraulic actuator. 
         [0021]    An assembly for pivoting a flap, the assembly disposed about an axis along which a flow passes from an upstream direction to a downstream direction, the assembly including a structure mounted at least partially around the axis. The structure is attached to a pivotable flap arranged to define a nozzle area. The pivotable flap is pivotable about a pivot at the structure. A cable is engaged with a first fixed engagement point of the structure, the cable passing through an orifice defined by the flap. An actuator system is operable to mechanically retract the cable therein to lessen the nozzle area and mechanically extend the cable to enable the flow to urge the flap to increase the nozzle area. The actuator system is engaged with the cable. A segment of the cable, opposite the actuator system, is attached to a fixed structure. 
         [0022]    In a further embodiment of any of the foregoing embodiments, the actuator system includes a spool engaged with the cable. 
         [0023]    In a further embodiment of any of the foregoing embodiments, the cable is strung through the orifice intermediate the first fixed engagement point and a second fixed engagement point of the structure. 
         [0024]    A method of providing a variable fan exit area of a high-bypass gas turbine engine includes the steps of locating a fan variable area nozzle to define a fan nozzle exit area between a fan nacelle and a core nacelle, and disposing a cable through at least one nacelle engagement point of the fan nacelle and through at least one flap engagement point of the fan variable area nozzle. The method includes the steps of providing an actuator system that engages with the cable, and activating or deactivating the cable engaged with the fan variable area nozzle to vary the fan nozzle exit area to adjust fan bypass airflow. Deactivating the cable extends the cable to enable the flow to urge the flaps to increase the area. 
         [0025]    In a further embodiment of any of the foregoing embodiments, the step of disposing a cable includes activating the cable to converge the fan nozzle exit area during cruise flight condition. 
         [0026]    In a further embodiment of any of the foregoing embodiments, the step of disposing a cable includes engaging a first end of the cable at a spool and a second end of the cable at the fixed attachment point. The cable between the first and second ends is received in an orifice defined at the flap engagement point. 
         [0027]    In a further embodiment of any of the foregoing embodiments, the actuator system is a rotary hydraulic actuator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
           [0029]      FIG. 1A  is a general perspective view an exemplary turbo fan engine embodiment for use with the present invention; 
           [0030]      FIG. 1B  is a perspective partial fragmentary view of the engine; 
           [0031]      FIG. 1C  is a rear view of the engine; 
           [0032]      FIG. 2A  is a perspective partial phantom view of a section of the FVAN; and 
           [0033]      FIG. 2B  is an expanded view of one flap assembly of the FVAN. 
           [0034]      FIG. 2C  is a partial phantom view of a section of the FVAN. 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      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. 
         [0036]    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  connected to the low spool  14  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. 
         [0037]    The engine  10  is preferably a high-bypass geared turbofan aircraft engine. Preferably, the engine  10  bypass ratio is greater than ten (10), the fan 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 5. The gear train  22  is preferably an epicyclic gear train such as a planetary gear system or other gear system with a gear reduction ratio of greater than 2.5. It should be understood, however, that the above parameters are only exemplary of a preferred geared turbofan engine and that the present invention is likewise applicable to other gas turbine engines. 
         [0038]    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  where is ignited, and burned. The resultant high pressure combustor products are expanded through the high pressure turbine  28  and low pressure turbine  18 . The turbines  28 ,  18  are rotationally coupled to the compressors  26 ,  16  respectively to drive the compressors  26 ,  16  in response to the expansion of the combustor product. The low pressure turbine  18  also drives the fan section  20  through the gear train  22 . 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 . 
         [0039]    The core nacelle  12  is supported within the fan nacelle  34  by structure  36  often generically referred to as an upper and lower bifurcation. 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 over  80  percent of the airflow entering the fan nacelle  34  becomes bypass flow B. The bypass flow B communicates through the generally annular bypass flow path  40  and is discharged from the engine  10  through a fan variable area nozzle (FVAN)  42  (also illustrated in  FIG. 1B ) which varies an effective fan nozzle exit area  44  between the fan nacelle  34  and the core nacelle  12 . 
         [0040]    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 FVAN  42  changes the physical area and geometry to manipulate the thrust provided by the bypass flow B. However, it should be understood that the fan nozzle exit area  44  may be effectively altered by methods other than structural changes. Furthermore, it should be understood that effectively altering the fan nozzle exit area  44  need not be limited to physical locations approximate the end of the fan nacelle  34 , but rather, may include the alteration of the bypass flow B at other locations. 
         [0041]    The FVAN  42  defines the fan nozzle exit area  44  for discharging axially the fan bypass flow B pressurized by the upstream fan section  20  of the turbofan engine. 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  is preferably designed for a particular flight condition—typically cruise at 0.8 M and 35,000 feet. The fan section  20  includes fan blades which are designed at a particular fixed stagger angle for an efficient cruise condition. The FVAN  42  is operated to 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 are maintained close to design incidence at other flight conditions such as landing and takeoff, thus enabling optimized engine operation over a range of flight condition with respect to performance and other operational parameters such as noise levels. Preferably, the FVAN  42  defines a nominal converged position for the fan nozzle exit area  44  at cruise and climb conditions, but radially opens relative thereto to define a diverged position for other flight conditions. The FVAN  42  preferably provides an approximately 20% (twenty percent) change in the fan nozzle exit area  44 . It should be understood that other arrangements as well as essentially infinite intermediate positions as well as thrust vectored positions in which some circumferential sectors of the FVAN  42  are converged relative to other diverged circumferential sectors are likewise usable with the present invention. 
         [0042]    The FVAN  42  is preferably separated into at least four sectors  42 A- 42 D ( FIG. 1C ) which are each independently adjustable to asymmetrically vary the fan nozzle exit area  44  to generate vectored thrust. It should be understood that although four sectors are illustrated, any number of sectors may alternatively be provided. 
         [0043]    In operation, the FVAN  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 invention. By adjusting the entire periphery of the FVAN  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  42 A- 42 D of the FVAN  42  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. 
         [0044]    Referring to  FIG. 2A , the FVAN  42  generally includes a flap assembly  48  which define the fan nozzle exit area  44 . The flaps  48  are preferably incorporated into the end segment  34 S of the fan nacelle  34  to define a trailing edge  34 T thereof. The flap assembly  48  generally includes a multiple of flaps  50 , each with a respective linkage system  52  and an actuator system  54 . 
         [0045]    Each flap  50  defines a pitch point  56  about which the flap  50  pivots relative the fan nacelle  34  (best illustrated in  FIG. 2B ). Forward of the pitch point  56  relative the trailing edge  34 T, the linkage system  52  preferably engages the flap  50 . It should be understood that other locations may likewise be usable with the present invention. 
         [0046]    The linkage system  52  preferably includes a cable  58  which circumscribes the fan nacelle  34 . The cable  58  engages each flap  50  at a flap engagement point  60  and a multiple of fixed fan nacelle structures  34 R such as fan nacelle ribs or such like at a fixed engagement point  62 . The flap engagement point  60  is preferably located within a flap extension  64  ( FIG. 2B ) which extends forward of the pivot point  56  relative the trailing edge  34 T and is preferably contained within the fan nacelle  34 . It should be understood that various flap extensions  64  and the like may be utilized within the flap linkage  52  to receive the cable  58  and that only a simplified kinematics representation is illustrated in the disclosed embodiment. 
         [0047]    The cable  58  is preferably strung within the fan nacelle  34  to pass through one fixed engagement point  62 , the flap engagement point  60  and a second fixed engagement point  62  ( FIG. 2C ). That is, the flap engagement point  60  is intermediate the fixed engagement points  62 . The fixed engagement point  62  and the flap engagement point  60  are generally eyelets or like which permit the cable to be strung therethrough. The eyelets may include roller, bushing, or bearing structures which minimizes friction applied to the cable  58  at each point  60 ,  62 . Preferably, the cable  58  is strung through a multiple of flaps  50  to define a flap set of each circumferential sectors  42 A- 42 D of the FVAN  42 . That is, a separate cable  58  is utilized within each circumferential sector  42 A- 42 D such that each cable  58  is individually driven by the actuator system  54  to asymmetrically adjust the FVAN  42 . 
         [0048]    Preferably, the actuator system includes a compact high power density electromechanical actuator (EMA)  65  or a rotary hydraulic actuator which rotates a spool  66  connected thereto. Alternatively, a linear actuator may be also utilized to directly pull the cable  58  to change the effective length thereof. That is, the cable  58  is pulled transverse to the length thereof such that the overall length is essentially “spooled” and “unspooled.” It should be understood that a cable-driven system inherently facilitates location of the actuator  65  relatively remotely from the multiple of flaps  50  through various pulley systems and the like. It should be understood that various actuator systems which deploys and retract the cable will be usable with the present invention. 
         [0049]    Referring to  FIG. 2C , the actuator system  54  engages an end segment  58 A of the cable  58  such that the cable  58  may be spooled and unspooled to increase or decrease the length thereof. The cable  58  is wound around a spool  66  at one end segment  58 A while the other end segment  58 B is attached to a fixed attachment such as one of the fixed structure  34 R. By spooling the cable  58  around the spool  66 , the effective circumferential length of the cable  58  is effectively decreased (shown in phantom) such that the fan nozzle exit area  44  is decreased. By unspooling the cable  58  from the spool  66 , the effective circumferential length of the cable  58  is effectively increased (shown solid) such that the fan nozzle exit area  44  is increased. The bypass flow B permits unilateral operation of the FVAN such that the bypass flow B diverges the flaps  50  and the FVAN  42  need only be driven (cable  58  retracted) to overcome the bypass flow B pressure which results in a significant weight savings. This advantage of the present invention allows practical use of the variable area nozzle on the gas turbine engines. 
         [0050]    Whereas the diverged shape is utilized for landing and takeoff flight conditions, should the cable  58  break, the FVAN  42  will failsafe to the diverged shape. It should be understood, however, that positive return mechanisms may alternatively or additionally be utilized. 
         [0051]    Each cable  58  preferably pitches one flap set between the converged position (shown in phantom) and a diverged position. It should be understood that although four sectors are illustrated ( FIG. 1C ), any number of sectors may alternatively or additionally be provided. It should be further understood that any number of flaps  50  may be controlled by a single cable  58  such that, for example only, the single cable may be strung around the entire circumference of the fan nacelle  34 , however, a sector arrangement is preferred to provide asymmetric capability to the FVAN  42 . 
         [0052]    The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention 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 invention.