Abstract:
An example turbomachine bushing a bushing having a wear surface configured to interface directly with a variable vane assembly to limit radially inward movement of the variable vane assembly, wherein the variable vane assembly is moveable axially between a first position contacting the wear surface and a second position spaced from the wear surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 61704079, which was filed on 21 Sep. 2012 and is incorporated herein by reference 
     
    
     BACKGROUND 
       [0002]    Turbomachines, such as gas turbine engines, typically include a fan section, a compression section, a combustion section, and a turbine section. Turbomachines may employ a geared architecture connecting portions of the compression section to the fan section. 
         [0003]    Some sections of turbomachines may include variable vanes. During operation, the variable vanes are adjusted to influence flow through the turbomachine. Flow through the turbomachine typically biases the variable vanes radially away from a turbomachine&#39;s rotational axis. 
         [0004]    Thus, variable vanes are typically designed to be biased away from the rotational axis. 
         [0005]    Biasing of the variable vanes toward the rotational axis may undesirably expose some structures of the variable vane that can disrupt flow and negatively affect engine performance. Moving the variable vanes toward the axis may undesirably wear away areas of the turbomachine case. 
       SUMMARY 
       [0006]    An example turbomachine bushing according to an exemplary aspect of the present disclosure includes, among other things, a bushing having a wear surface configured to interface directly with a variable vane assembly to limit radially inward movement of the variable vane assembly. The variable vane assembly is moveable axially between a first position contacting the wear surface and a second position spaced from the wear surface. 
         [0007]    In a non-limiting embodiment of the foregoing turbomachine bushing, the wear surface may face radially away from a rotational axis of a turbomachine. 
         [0008]    In a non-limiting embodiment of either of the foregoing turbomachine bushings, at least a portion of the bushing may be received within a bore that also receives a portion of the variable vane assembly. 
         [0009]    In a non-limiting embodiment of any of the foregoing turbomachine bushings, the bushing may interface directly with a vane arm of the variable vane assembly when the variable vane assembly is in the first position. 
         [0010]    In a non-limiting embodiment of any of the foregoing turbomachine bushings, the vane arm may include at least one radially inward facing surface that interfaces directly with the bushing when the variable vane assembly is in the first position. 
         [0011]    In a non-limiting embodiment of any of the foregoing turbomachine bushings, a vane arm of the variable vane assembly may contact the wear surface when the variable vane assembly is in the first position. 
         [0012]    In a non-limiting embodiment of any of the foregoing turbomachine bushings, the bushing may comprise nickel. 
         [0013]    In a non-limiting embodiment of any of the foregoing turbomachine bushings, the bushing and a portion of the variable vane assembly that may contact the wear surface are made of the same material. 
         [0014]    A turbomachine assembly according to an exemplary aspect of the present disclosure includes, among other things, an annular case, a bushing, a variable vane having a portion received within a bore of the case, and a vane arm configured to rotate the variable vane. The variable vane and vane arm are biased toward a rotational axis of the turbomachine or away from the rotational axis in response to flow. The vane arm contacts the bushing when the variable vane is biased toward the rotational axis. The vane arm is spaced from the bushing when the variable vane is biased away from the rotational axis. 
         [0015]    In a non-limiting embodiment of the foregoing turbomachine assembly, the annular case may be a compressor case. 
         [0016]    In a non-limiting embodiment of either of the foregoing turbomachine assemblies, the bushing may be press-fit within the bore. 
         [0017]    In a non-limiting embodiment of any of the foregoing turbomachine assemblies, the vane arm may provide an aperture that receives a portion of the variable vane. 
         [0018]    In a non-limiting embodiment of any of the foregoing turbomachine assemblies, the portion of the variable vane may comprise a vane stem. 
         [0019]    In a non-limiting embodiment of any of the foregoing turbomachine assemblies, the aperture may be within a claw portion of the variable vane, the claw portion having claw surfaces facing radially inward toward the rotational axis, the claw surfaces contacting the bushing when the variable vane is biased toward the rotational axis. 
         [0020]    A method of limiting wear in a turbomachine according to an exemplary aspect of the present disclosure includes, among other things, providing a bushing wear surface that contacts a variable vane surface when the assembly is biased toward a rotational axis of a turbomachine. 
         [0021]    In a non-limiting embodiment of the foregoing method, the method may include moving the variable vane assembly away from the bushing wear surface when the assembly is biased away from the rotational axis of the turbomachine. 
         [0022]    In a non-limiting embodiment of either of the foregoing methods, the bushing wear surface may be configured to contact a vane arm of the variable vane assembly. 
         [0023]    In a non-limiting embodiment of any of the foregoing methods, the variable vane surface may face the rotational axis. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0024]    The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows: 
           [0025]      FIG. 1  shows a section view of an example gas turbine engine. 
           [0026]      FIG. 2  shows a close up view of a compressor section of the engine of  FIG. 1 . 
           [0027]      FIG. 3  shows a perspective view of interface between a portion of a variable vane and a case of the compressor section of  FIG. 2 . 
           [0028]      FIG. 4  shows a perspective view of the case of  FIG. 3 . 
           [0029]      FIG. 5  shows a close-up view of Area  5  in  FIG. 2  with a vane arm and attachment structure removed. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]      FIG. 1  schematically illustrates an example turbomachine, which is a gas turbine engine  20  in this example. The gas turbine engine  20  is a two-spool turbofan gas turbine engine that generally includes a fan section  22 , a compression section  24 , a combustion section  26 , and a turbine section  28 . 
         [0031]    Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans. That is, the teachings may be applied to other types of turbomachines and turbine engines including three-spool architectures. Further, the concepts described herein could be used in environments other than a turbomachine environment and in applications other than aerospace applications. 
         [0032]    In the example engine  20 , flow moves from the fan section  22  to a bypass flowpath. Flow from the bypass flowpath generates forward thrust. The compression section  24  drives air along a core flowpath. Compressed air from the compression section  24  communicates through the combustion section  26 . The products of combustion expand through the turbine section  28 . 
         [0033]    The example engine  20  generally includes a low-speed spool  30  and a high-speed spool  32  mounted for rotation about an engine central axis A. The low-speed spool  30  and the high-speed spool  32  are rotatably supported by several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively, or additionally, be provided. 
         [0034]    The low-speed spool  30  generally includes a shaft  40  that interconnects a fan  42 , a low-pressure compressor  44 , and a low-pressure turbine  46 . The shaft  40  is connected to the fan  42  through a geared architecture  48  to drive the fan  42  at a lower speed than the low-speed spool  30 . 
         [0035]    The high-speed spool  32  includes a shaft  50  that interconnects a high-pressure compressor  52  and high-pressure turbine  54 . 
         [0036]    The shaft  40  and the shaft  50  are concentric and rotate via bearing systems  38  about the engine central longitudinal axis A, which is collinear with the longitudinal axes of the shaft  40  and the shaft  50 . 
         [0037]    The combustion section  26  includes a circumferentially distributed array of combustors  56  generally arranged axially between the high-pressure compressor  52  and the high-pressure turbine  54 . 
         [0038]    In some non-limiting examples, the engine  20  is a high-bypass geared aircraft engine. In a further example, the engine  20  bypass ratio is greater than about six (6 to 1). 
         [0039]    The geared architecture  48  of the example engine  20  includes an epicyclic gear train, such as a planetary gear system or other gear system. The example epicyclic gear train has a gear reduction ratio of greater than about 2.3 (2.3 to 1). 
         [0040]    The low-pressure turbine  46  pressure ratio is pressure measured prior to inlet of low-pressure turbine  46  as related to the pressure at the outlet of the low-pressure turbine  46  prior to an exhaust nozzle of the engine  20 . In one non-limiting embodiment, the bypass ratio of the engine  20  is greater than about ten (10 to 1), the fan diameter is significantly larger than that of the low-pressure compressor  44 , and the low-pressure turbine  46  has a pressure ratio that is greater than about 5 (5 to 1). The geared architecture  48  of this embodiment is an epicyclic gear train with a gear reduction ratio of greater than about 2.5 (2.5 to 1). It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans. 
         [0041]    In this embodiment of the example engine  20 , a significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section  22  of the engine  20  is designed for a particular flight condition -- typically cruise at about 0.8 Mach and about 35,000 feet. This flight condition, with the engine  20  at its best fuel consumption, is also known as “Bucket Cruise” Thrust Specific Fuel Consumption (TSFC). TSFC is an industry standard parameter of fuel consumption per unit of thrust. 
         [0042]    Fan Pressure Ratio is the pressure ratio across a blade of the fan section  22  without the use of a Fan Exit Guide Vane system. The low Fan Pressure Ratio according to one non-limiting embodiment of the example engine  20  is less than 1.45 (1.45 to 1). 
         [0043]    “Low Corrected Fan Tip Speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram ° R)/(518.7° R)]̂0.5. The Temperature represents the ambient temperature in degrees Rankine. The Low Corrected Fan Tip Speed according to one non-limiting embodiment of the example engine  20  is less than about 1150 fps (351 m/s).The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims. 
         [0044]    Referring to  FIG. 2 , the high-pressure compressor section  52  of the engine  20  includes arrays  60   a - 60   c  of variable vanes  64 . Each of the arrays  60   a - 60   c  include individual variable vanes  64  extending radially away from the axis A. The variable vanes  64  have a radially inner end  68  mounted to a core  72  of the engine  20 , and a radially outer end  76  mounted to a case structure  80  of the engine  20 . 
         [0045]    During operation, the variable vane  64  may be rotated back and forth about a respective radial axis R extending from the axis A. Rotating the variable vane  64  influences flow through the high-pressure compressor  52  of the engine  20  by permitting more or less flow through the respective stage of the compressor section  52 . 
         [0046]    In this example, each variable vane  64  includes an airfoil portion  82 , a button portion  86 , and a stem  90 . The button portion  86  and the stem  90  are received within a bore  88  of the case structure  80 . A portion of the stem  90  extends radially outside the bore  88 . 
         [0047]    A vane arm  92  couples the variable vane  64  to an actuator assembly  94 . In this example, the vane arm  92  and the variable vane  64  provide a variable vane assembly. 
         [0048]    The example vane arm  92  includes a claw portion  96  that fits over the stem  90  of the variable vane  64 . A threaded fastener  98  and a lock nut  100  are used, in this example, to hold the claw portion  96  in position over the stem  90 . The claw portion  96  includes surfaces  102  directed radially inward toward the axis A. The vane arm  92  is moved by the actuator assembly  94  to rotate the variable vane  64 . 
         [0049]    A bushing  104  provides a contact surface  108  facing radially outward away from the axis A. When flow through the engine  20  biases the variable vane  64  away from the axis A, the contact surface  108  is spaced from the surfaces  102  of the claw portion  96 . When flow through the engine  20  causes the variable vane  64  to be biased toward the axis A, the variable vane assembly moves such that the contact surface  108  contacts the surfaces  102  of the claw portion  96 . 
         [0050]    The bushing  104 , in this example, is a nickel material such as an Inconel 718. The material of the bushing  104  provides a suitable interface for withstanding contact with the vane arm  92 , which is also nickel in this example. 
         [0051]    The bushing  104  is press-fit into a bore  112  established within the case structure  80 , which is made of a titanium or composite material in this example. Once press-fit, interference between the bushing  104  and the case structure  80  holds the position of the bushing  104 . A flange  114  limits movement of the bushing  104  into the bore  112  during the press-fitting. The flange  144  includes the contact surface  108  in this example. The flange  114  extends outward from other portions of the bushing  104 . 
         [0052]    The bushing  104  protects the case structure  80  from damage associated with contact with the claw portion  96 , which is part of the variable vane assembly. That is, without the bushing  104 , the surfaces  102  of the claw portion  96  could contact and damage the case structure  80 . 
         [0053]    Contact between the surfaces  102  of the claw portion  96  and the bushing  104  also limits movement of the variable vane  64  toward the axis A. The movement may be limited such that the button portion  86  does not protrude into a flow path of the engine  20  when the variable vane  64  is biased toward the rotational axis A. 
         [0054]    Features of these disclosed examples include limiting or preventing movement of a variable vane to a radially inward position where damaging contact between the variable vanes and associated vane arms with a case structure could occur. Another feature includes providing a specialized wear surface when the variable vanes are biased radially inward. 
         [0055]    The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.