Abstract:
Gas turbine engine systems involving gear-driven variable vanes are provided. In this regard, a representative gas turbine engine system includes: a ring gear assembly operative to be mounted within an engine casing; and a vane module having a first vane airfoil and a first gear, the first gear being operative to engage the ring gear assembly such that movement of the ring gear alters a position of the first vane airfoil.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure generally relates to gas turbine engines. 
         [0003]    2. Description of the Related Art 
         [0004]    Many gas turbine engines incorporate variable stator vanes, the angle of attack of which can be adjusted. Conventionally, implementation of variable vanes involves providing an annular array of vanes, with each of the vanes being attached to a spindle. The spindles extend radially outward through holes formed in the engine casing in which the vanes are mounted. Each of the spindles is connected to a lever arm that engages a unison ring located outside the engine casing. In operation, movement of the unison ring pivots the lever arms, thereby rotating the spindles and vanes. 
       SUMMARY 
       [0005]    Gas turbine engine systems involving gear-driven variable vanes are provided. In this regard, an exemplary embodiment of a gas turbine engine system comprises: a ring gear assembly operative to be mounted within an engine casing; and a vane module having a first vane airfoil and a first gear, the first gear being operative to engage the ring gear assembly such that movement of the ring gear alters a position of the first vane airfoil. 
         [0006]    An exemplary embodiment of a gas turbine engine comprises: a compressor; a combustion section operative to receive compressed air from the compressor; a turbine operative to drive the compressor; a casing operative to encase the turbine; and a gear-driven variable vane system having a ring gear assembly and a vane module, the ring gear assembly being mounted within an interior of the casing, the vane module having a first vane airfoil and a first gear, the first gear being operative to engage the ring gear assembly such that movement of the ring gear alters a position of the first vane airfoil. 
         [0007]    An exemplary embodiment of a vane module for a gas turbine engine comprises: an inner platform, an outer platform, a first vane airfoil and a first gear, the first vane airfoil extending between the inner platform and the outer platform, the vane module being operative to rotate the first vane airfoil relative to the inner platform and the outer platform, responsive to rotation of the first gear. 
         [0008]    Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0010]      FIG. 1  is a schematic diagram depicting an exemplary embodiment of a gas turbine engine. 
           [0011]      FIG. 2  is a schematic diagram depicting a portion of the variable vane assembly of the embodiment of  FIG. 1 . 
           [0012]      FIG. 3  is a schematic diagram showing detail of the opposing gear rings of another embodiment. 
           [0013]      FIG. 4  is a partially-exploded, schematic view of an exemplary embodiment of a system involving gear-driven variable vanes. 
           [0014]      FIG. 5  is a schematic diagram depicting an exemplary embodiment of a compression mechanism. 
           [0015]      FIG. 6  is a schematic diagram depicting detail of the compression mechanism of  FIG. 5 . 
           [0016]      FIG. 7  is a schematic diagram depicting another exemplary embodiment of a compression mechanism. 
           [0017]      FIG. 8  is a schematic diagram depicting another exemplary embodiment of a compression mechanism. 
           [0018]      FIG. 9A  is a schematic diagram depicting another embodiment of a compression mechanism. 
           [0019]      FIG. 9B  is a schematic diagram showing the embodiment of  FIG. 9A  responsive to the drive gear being rotated. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Gas turbine engine systems involving gear-driven variable vanes are provided, several exemplary embodiments of which will be described in detail. In some embodiments, the vanes are incorporated into rotatable vane modules. Gears of the vane modules are engaged between opposing gear teeth of annular ring gears that are positioned within the engine casing. 
         [0021]      FIG. 1  is a schematic diagram of a gas turbine engine  100 . Engine  100  incorporates an engine casing  101  that houses a fan  102 , a compressor section  104 , a combustion section  106  and a turbine section  108 . Engine  100  also incorporates a gear-driven variable vane assembly  110 . Although depicted in  FIG. 1  as a turbofan gas turbine engine, there is no intention to limit the concepts described herein to use with turbofans as other types of gas turbine engines can be used. 
         [0022]    As shown in the partially cut-away, schematic diagram of  FIG. 2 , vane assembly  110  includes an annular arrangement of vane modules (e.g., module  120 ) positioned within the engine casing  101  about a longitudinal axis  121 . Each of the vane modules includes one or more vanes (e.g., vane  124 ). Each vane module also includes a module gear (e.g., module gear  126 ) that is used to rotate the vane(s) of the module about the center axis of the gear. By way of example, gear  126  rotates vane  124  about axis  128 . 
         [0023]    Each vane module engages a ring gear assembly  130 . Notably, the ring gear assembly is positioned within the engine casing. A motor assembly  140  also is provided that includes a motor  142  (positioned outside the engine casing), a shaft  144  and a drive gear  146 . In the embodiment of  FIG. 2 , motor  142  is a stepper motor. 
         [0024]    Shaft  144  extends from the motor into the interior of the engine casing via a penetration  148 . A distal end of the shaft is attached to drive gear  146 , which engages the ring gear assembly so that operation of the motor rotates the drive gear, thereby actuating the ring gear assembly. Actuation of the ring gear assembly rotates the module gears, thereby positioning the vanes. 
         [0025]    Another embodiment is depicted schematically in  FIG. 3 . As shown in  FIG. 3 , ring gear assembly  160  incorporates opposing ring gears  162 ,  164 , the teeth of which face inwardly. A vane module gear  166  and drive gear  168  are engaged between the ring gears. Notably, use of this dual-ring configuration applies torque to the center of the axis of rotation of the vane module gear, thereby tending to reduce thrust loads on the spindle  170 . This configuration also tends to accommodate thermal growth by allowing radial motion of the vane module gear with respect to the ring gears. Radial engagement of vane module gears about the circumference of the ring gear assembly also tends to self-center the ring gears regardless of the position of the vane modules. This tends to simplify positioning and tends to avoid radial binding due to thermal growth effects. 
         [0026]      FIG. 4  is an exploded, schematic view of a portion of another embodiment of a gas turbine engine system involving gear-driven variable vanes. As shown in  FIG. 4 , system  200  includes a vane module  202  (only one of which is depicted in  FIG. 4 ), a mounting assembly  204 , and a ring gear assembly  206 . Vane module  202  includes an inner platform  210 , an outer platform  212  and at least one vane airfoil extending between the platforms. In the embodiment of  FIG. 4 , the vane module is configured as a doublet, i.e., two airfoils  214 ,  216  are provided, with the airfoils of the doublet moving relative to the vane module. In other embodiments, various other numbers and configurations of airfoils can be used. 
         [0027]    Vane module  202  also includes a spindle  218  that extends radially outwardly from the outer platform. In this embodiment, the spindle includes a spindle feature  220  (e.g., an annular recess) that mates with a corresponding feature  222  (e.g., a ridge) of the mounting assembly. The spindle supports the first vane module gear  224  that extends into a track  226  of the mounting assembly. 
         [0028]    In this regard, mounting assembly  204  is provided in a split-ring configuration that includes a forward annular member  230  and an aft annular member  232 . The annular members include split apertures that engage about the vane module spindles. For instance, member  230  includes a split aperture  234  and member  232  includes a split aperture  236  that engage each other to form an aperture in which a spindle is received. As another example, spindle  218  is received by split aperture  238  of member  232  and a corresponding split aperture of member  230  (not shown). 
         [0029]    The mounting assembly also includes outwardly extending tabs (e.g., tab  244 ) that facilitate attachment of the mounting assembly to the interior of an engine casing. So mounted, the engine casing, the tabs and respective outer surfaces  246 ,  248  of the annular members  230 ,  232  form track  226  within which the opposing ring gears  250 ,  252  of the ring gear assembly  206  are located. 
         [0030]    Additionally, the vane outer platform  212  has a mating feature  254  that is in close contact with the mating surface  256  on the split ring member  232  to prevent the vane module  202  from rotating relative to the split ring mounting assembly  204 . The mounting assembly  204  is located within the case  101  such that the axial and tangential loads created during the operation of the engine are transmitted from the vane module  202 , through the spindle feature  220 , into the mount assembly  204 . The mount assembly  204  can move radially relative to the case  101  so that thermally induced loads are not transmitted into the case  101 . 
         [0031]    The mounting assembly  204 , supports the vane modules  202  in the radial direction by the restraint of the outer platform  212  through interaction between spindle feature  220  and feature  238 . In this embodiment, the radial growth of the inner platform  210  is not constrained by the mount assembly  204 , thus avoiding adverse loading. The inner platform  210  relative position to the outer platform  212  is maintained by the first vane airfoil  214  and the second vane airfoil  216 . 
         [0032]    Various techniques and/or mechanisms can be used for promoting desired engagement between the opposing ring gears. In this regard, reference is made to the schematic diagrams of  FIGS. 5 and 6 , which depict an embodiment of a compression mechanism  300 . As shown in  FIG. 5 , portions of ring gears  301  and  302  are configured to contact each other. Specifically, ring gear  301  includes a contact member  304  and ring gear  302  includes a contact member  306 . The contact members are located at positions of the ring gears that are not intended to contact vane module gears. Thus, a ring gear assembly can include multiple sets of contact members in a spaced arrangement about the ring gears. 
         [0033]    In  FIG. 5 , the contact members extend toward each other. As shown in greater detail in  FIG. 6 , contact member  304  is a non-geared portion of ring gear  301  that incorporates a protrusion  314 , whereas contact member  306  is a non-geared portion of ring gear  302  that incorporates a recess  316 . In this embodiment, both the protrusion and recess are generally rectangular and are secured in a mated position by a fastener  320  ( FIG. 5 ) that is received within a bore  322 . When secured in the mated position in which the protrusion is seated within the recess ( FIG. 5 ), the gear teeth of the ring gears are compressed into contact with the gear teeth of the module gears in a vicinity of the compression mechanism  300 . 
         [0034]    Notably, in this embodiment, slot  316  is longer in the circumferential direction than the protrusion  314  to allow the ring  304  to move concentrically with ring  306  about axis  121 . However, slot  316  is not substantially larger in radial thickness than the protrusion  314  to prevent relative motion of the center of ring  304  and the center of ring  306 . The relative difference in length between slot  316  and the protrusion  314  may be used to restrict the overall rotation of ring  304  relative to ring  306 , about axis  121 . 
         [0035]    The fastener  320  is held in position by bore  322 , and uses a spring feature  324  ( FIG. 5 ), acting upon ring  302 , to pull ring  301  and ring  302  together while still allowing the relative motion between the rings. 
         [0036]      FIG. 7  is a schematic diagram depicting another embodiment of a compression mechanism. As shown in  FIG. 7 , the compression mechanism  330  includes a biasing member  332  that extends between ring gear  334  and ring gear  336 . Specifically, the biasing member (e.g., a spring) biases the ring gears toward each other in a vicinity of a vane module gear (e.g., gear  338 ). 
         [0037]    The spring  332  is mounted to rings  334  and  336  such that the rings are free to rotate relative to each other about axis  121 . The spring  332  rotates as needed, within rings  334  and  336 , and applies an increasing load, pulling the rings  334  and  336  together as the relative distance between the end points of spring  332  increase, i.e., the spring is always pulling the two rings  334  and  336  together. 
         [0038]      FIG. 8  is a schematic diagram depicting another embodiment of a compression mechanism. As shown in  FIG. 8 , the compression mechanism  350  includes a biasing member  352  that is configured as a leaf spring. The leaf spring biases the ring gears  354  and  356  toward each other in a vicinity of vane module gear  358 . Compression mechanism  350  may be complimented with a similar compression member on the opposite side of the ring assembly, ensuring equal loading, or constraining the ring  354  and  356  to a limited range of motion in the direction of axis  121 . Compression member  350  may also be installed on the inside or outside surfaces of rings  354  and/or  356  to prevent, or limit, motion of the center of rings  354  and/or  356  from the axis  121 . 
         [0039]    In contrast to the embodiments of  FIGS. 5 through 8 , compression mechanism  370  of  FIGS. 9A and 9B  incorporates a biasing member  372  that biases ring gears  374 ,  376  to a neutral position in addition to compressing the ring gears against a vane module gear  378 . Specifically, as shown in  FIG. 9A , ring gear  374  includes a socket  380  in which a ball joint  382  is received. A connector  384  extends from the ball joint, through an aperture  386  formed in the socket. The connector extends through an aperture  388  of corresponding socket  390  of ring gear  376  and terminates in an opposing ball joint  392 . 
         [0040]    The connector  384  extends through ball joint  392 , and can move relative to the ball joint  392  about an axis defined by the longitudinal axis of the connector  384 . A spring assembly  394 , attached to the end of connector  384 , applies a load to the ball joint  392 . The spring pulls upon connector  384 , which also applies a load on socket  380 . Thus, opposing forces created by spring preload act upon socket  380  and ball joint  392 , through connector  384 , such that rings  374  and  376  are pulled together. 
         [0041]    The relative rotation of rings  374  and  376 , about axis  121 , causes the connector  384  to rotate in the ball joint  382  in socket  380  and ball joint  392  in socket  390 . The increase in distance between the center of ball joints  382  and  392  results in the compression of the spring mounted to connector  384 , and a corresponding increase in the load pulling rings  374  and  376  together. Selection of the spring strength (spring rate) and the length of connector  384  will allow rotation motion of the rings  374  and  376  to occur as desired, without causing binding, or excessive loads in connector  384 . 
         [0042]    In some embodiments, the shape of the contact surface between ball joints  380 ,  382 ,  390  and  392  may be spherical, cylindrical, or a combination of the two, as desired to control the relative motion of rings  374  and  376 . 
         [0043]    It should be emphasized that the above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.