Abstract:
An actuator system mounted to a gas turbine engine that communicates mechanical power for positioning variable guide vanes within the gas turbine engine. The actuator system includes a torque box having components for communicating mechanical power to the variable guide vanes for positioning the vanes and an actuator mechanically coupled to provide mechanical power to the components of the torque box used to communication the provided mechanical power to the inlet guide vanes. The actuator is mounted to the torque box via a plurality of bolts.

Description:
BACKGROUND 
       [0001]    The present invention is related to gas turbine engines, and in particular to actuators for positioning inlet guide vanes and/or rotatable guide vanes. 
         [0002]    Gas turbine engines rely on rotating and stationary components to effectively and efficiently control the flow of air through the engine. Rotating components include rotor blades employed in compressor and turbine sections for compressing air and extracting energy from air after combustion. Stationary components include vanes placed in the airflow to aid in directing airflow. By varying the position of the vanes (i.e., rotating them to vary the profile provided to the airflow), airflow characteristics can be optimized for various operating conditions. 
         [0003]    The mechanism for providing precise, controlled, and uniform actuation of the vanes is a linear actuator connected to the plurality of vanes located circumferentially around the engine via a series of linkages. The actuator is typically mounted to the exterior of the engine case, and communicates power to the series of linkages via a bell crank or similar mechanical device mounted on a torque box. Installation and alignment of the actuator relative to the bell crank is critical to achieving a desired positioning of the vanes. However, factors such as thermal growth during various flight conditions can adversely affect the alignment of the actuator with the bell crank, which results in errors in between the desired position of inlet guide vanes and the actual position of the inlet guide vanes. 
       SUMMARY 
       [0004]    An actuation system mounted to a gas turbine engine that communicates mechanical power for positioning inlet guide vanes within the gas turbine engine. The actuation system includes a torque box having components for communicating mechanical power to position the inlet guide vanes and an actuator mechanically coupled to provide mechanical power to the components of the torque box. The actuator is mounted to the torque box via a plurality of bolts. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  is a cross-sectional view of a gas turbine engine according to an embodiment of the present invention. 
           [0006]      FIG. 2  is a top-view of an actuator and torque box positioned above an engine case according to an embodiment of the present invention. 
           [0007]      FIG. 3  is a side view illustrating the attachment of the actuator to the torque box according to an embodiment of the present invention. 
           [0008]      FIG. 4  is an isometric view illustrating the attachment of an actuator to the torque box according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIG. 1  is a cross-sectional view of a compressor section of gas turbine engine  10  according to an embodiment of the present invention, although the principles of the present invention may be applied to a turbine section of gas turbine engine  10  as well. In the cross-sectional view shown in  FIG. 1 , gas turbine engine  10  includes a plurality of stationary variable guide vanes (VGV)  12  and a plurality of rotating blades  14 . With respect to stationary VGVs  12 , each is rotatable about an axis  16  that is substantially perpendicular with engine centerline axis  18 . The performance of gas turbine engine  10  is modified, in part, by adjusting the position of stationary VGVs  12  to selectively vary airflow characteristics of the engine. 
         [0010]    Mechanical force used to change the position of VGVs  12  is provided by actuator  20 , and communicated via torque box  22  and a plurality of arms  24  to stationary VGVs  12 . Actuator  20  and torque box  22  are positioned radially outward of engine case  26 . As discussed in more detail below, torque box  22  is mechanically attached to engine case  26 , while actuator  20  is mechanically coupled to torque box  22 . A benefit of connecting actuator  20  to torque box  22 , rather than directly to engine case  26  is improved alignment between actuator  20  and torque box  22 . In particular, when both the torque box and actuator are attached to the engine case, tolerances associated with attachment of both the torque box and actuator to the engine case, coupled with thermal growth issues can negatively impact the alignment between the two, which results in positioning errors in the stationary VGVs. 
         [0011]      FIG. 2  is a top-view of actuator  20  and torque box  22  positioned above engine case  26  according to an embodiment of the present invention. Actuator  20  is a linear actuator that provides mechanical force in the direction indicated by line  32 . Actuator arm  30  is connected to dog-bone arm  34 , which in turn is connected to bell crank  36 . In the embodiment shown in  FIG. 2 , bell crank  36  includes first end  38 , second end  40 , and third end  42 . First end  38  is mechanically coupled to dog-bone arm  34 . Second end  40  is connected to a first stage synchronizing ring (not shown). Third end  42  is mechanically coupled to arm  24 . Bell crank  36  is supported by and pivotally connected to torque box  22  at pivot point  44 . Mechanical force applied by actuator  20  in the direction indicated by line  32  results in bell crank  36  pivoting about point  44 , resulting in mechanical force being applied by third end  42  to arms  24  in a direction indicated by arrow  45 , in a direction opposite to the direction of first end  38 . Conversely, mechanical force applied by actuator  20  in a direction opposite of line  32  results in mechanical force being applied by third end  42  to arms  24  in a direction opposite that indicated by arrow  45 . 
         [0012]    A plurality of synchronizing rings (not shown) are positioned circumferentially around engine case  26 , including at least one synchronizing ring located forward of bell crank  36  attached to actuator  20  via second end  40  of bell crank  36 . Each synchronizing ring is associated with the VGVs  12   a,    12   b,  and  12   c,  respectively, shown in  FIG. 1 . Mechanical motion provided via arms  24  in a direction indicated by arrow  45  is communicated to the synchronizing rings, which results in the synchronizing rings moving in a circumferential direction that results in positioning of VGVs  12   a,    12   b,  and  12   c.    
         [0013]    Actuator  20  is mechanically fixed to torque box  22 . In the embodiment shown in  FIG. 2 , three bolts  52   a,    52   b,  and  52   c  attach actuator  20  to torque box  22 . Bolts  52   a  and  52   b  extend radially into torque box  22 , while bolt  52   c  extends tangentially (i.e., at an angle perpendicular to bolts  52   a  and  52   b ) into torque box  22 . Bolt  52   b  is located forward of bolt  52 a, and may be located at a radial height different than that of bolt  52   a.    
         [0014]      FIG. 3  is a cross-sectional view taken along line  3 - 3  shown in  FIG.2 , illustrating the attachment of actuator  20  to torque box  22  according to an embodiment of the present invention. In the embodiment shown in  FIG. 3 , actuator  20  is located adjacent torque box  22 . Bolt  52   c  is visible, and illustrates attachment of actuator  20  to torque box  22 . In addition, the cross-sectional view shown in  FIG. 3  illustrates the placement of helical coil insert  54   c  within torque box  22  to secure bolt  52   c.    
         [0015]    In addition, the embodiment shown in  FIG. 3  illustrate the placement of actuator  20  adjacent to torque box  22 , while maintaining the placement of actuator  20  proximate to engine case  26  (as opposed to locating actuator  20  radially outward of torque box  22 ). This decreases the cross-sectional profile of actuator  20  and torque box  22 , and is beneficial in decreasing the overall size of the engine. 
         [0016]      FIG. 4  is an isometric view illustrating the attachment of actuator  20  to torque box  22  according to another embodiment of the present invention. In the embodiment shown in  FIG. 4 , actuator  60  is mechanically coupled to torque box  62  by three bolts  72   a,    72   b,  and  72   c.  However, in the embodiment shown in  FIG. 4 , bolts  72   a  and  72   b  are directed tangentially through actuator  60  to torque box  62 , while only bolt  72   c  is directed radially through actuator  60  to torque box  62 . In addition, helical coil inserts  74   a,    74   b  and  74   c  and washers  76   a,    76   b,  and  76   c  are shown. Helical coil inserts  74   a - 74   c  are provided in the bolt holes to lock bolts  72 a- 72   c  in place once installed (i.e., prevent loosening rotation of the bolts). Washers  76   a - 76   c  are located adjacent to actuator  60  to prevent damage to the surface of actuator  60 . 
         [0017]    Bolts  72   a  and  72   b  secure actuator  60  to torque box  62  in a direction tangential to a circumference associated with the engine centerline axis  18 . Bolt  72   c  secures actuator  60  to torque box  62  in a radial direction. Bolts  72   a  and  72   b  are generally aligned with one another, but perpendicular to bolt  72   c.  The combination of bolts  72   a,    72   b  and  72   c  secure actuator  20  to torque box  22 . 
         [0018]    In addition, bolt  72   c  is located on a plane radially inward of torque box  62  with bolts  72   a  and  72   b  tangential to the torque box  22 . The location of bolt  72   c  relative to bolts  72   a  and  72   b  prevents axial bending or flexing of actuator  60  relative to torque box  62 , thereby improving alignment between actuator  60  and torque box  62 . In addition, locating sleeve  78   a  is employed in conjunction with bolt  72   a,  to align actuator  60  with torque box  62 . 
         [0019]    While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.