Abstract:
A variable inlet guide vane assembly for a gas turbine engine, where the guide vanes are pivotably connected to a sync ring that is contained within an annular groove within the casing so that leakage through holes in the casing is minimized. The guide vanes include a slider mechanism on one of the ends that will allow for both an axial and a rotational movement of the guide vane pin when the guide vanes pivot about a fixed pin on an opposite end of the guide vanes. a round rotary vane actuator with a height much less than a diameter is mounted outside of the casing and connects to the sync ring through a driving linkage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit to an earlier filed Provisional Application 61/098,322 filed Sep. 19, 2008 and entitled VARIABLE INLET GUIDE VANE WITH ACTUATOR. 
    
    
     FEDERAL RESEARCH STATEMENT 
     None. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a gas turbine engine, and more specifically to a variable inlet guide vane and an actuator for the variable inlet guide vane. 
     2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
     A gas turbine engine includes a compressor with multiple rows of rotor blades spaced between multiple rows of stator vanes to gradually compress air for delivery to a combustor. Many gas turbine engines include a first stage of inlet guide vanes that are variable in order to change the angle of each guide vane. 
     In many engines with variable inlet guide vanes, each vane is pivotably connected to an actuator in which a radial extending pin passes through a hole formed within the casing that is attached to an actuator or to a linkage that is attached to an actuator. Each guide vane includes a pin that extends through a separate hole formed in the casing so that each guide vane can be moved together. Because each guide vane requires a hole in the casing, leakage of the air flow passing through the guide vanes is high. 
     In the variable inlet guide vanes of the prior art in which each guide vane includes a linkage to connect it to the driving motor, the linkage is complex with several linkages that create a complex assembly, and that will involve large tolerances especially when wear occurs between the links. 
     Another issue with the prior art variable inlet guide vanes is that the actuator used to drive the guide vanes is a rather large piston cylinder that is both heavy and takes up a lot of space. In an aero engine of the type used to power an aircraft, both weight and size are important matters related to the engine efficiency. Space is limited for the engine and its components. The prior art actuators are large linear piston actuators that drive the linkage connecting the guide vanes. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide for a variable inlet guide vane assembly with a reduced number of openings in the casing to connect the guide vanes to the driving motor that results in high leakage. 
     It is another object of the present invention to provide for a variable inlet guide vane assembly with linkages between the actuator motor and the guide vanes that is less complex than is the prior art linkages. 
     It is another object of the present invention to provide for a variable inlet guide vane assembly with a less complex assembly of links. 
     It is another object of the present invention to provide for a variable inlet guide vane assembly with a lightweight and compact actuator to drive the guide vanes over that found in the prior art guide vane actuators. 
     The above objectives and more are achieved in the variable inlet guide vane assembly of the present invention in which each variable guide vane is connected to a linkage that is fully contained within the casing. an inner facing circumferential groove is formed within the casing in which an annular sync ring moves in a circumferential direction. Each guide vane is connected to the sync ring within the casing. The sync ring is connected to a driving motor through a hole in the casing so that a minimal number of holes are used to reduce leakage. Circumferential movement of the sync ring pivots each guide vane to change the angle. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  shows an isometric view of the variable inlet guide vane of the present invention from the leading edge side. 
         FIG. 2  shows an isometric view of the variable inlet guide vane of  FIG. 1  from the trailing edge end and without the outer casing. 
         FIG. 3  shows an enlarged view of the Detail A in  FIG. 2 . 
         FIG. 4  shows an isometric view of the actuator of the present invention. 
         FIG. 5  shows an exploded view of the parts in the actuator of  FIG. 4 . 
         FIG. 6  shows an isometric view of the back half of the actuator of the present invention. 
         FIG. 7  shows an isometric view of the three vane piston used in the actuator of the present invention. 
         FIG. 8  shows an isometric view of a linkage for a vane tip clearance control device of the present invention. 
         FIG. 9  shows a side view of the linkage of  FIG. 8 . 
         FIG. 10  shows an isometric view of the vane tip clearance control apparatus of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows the inlet guide vane assembly with a vane  11  having a leading edge  12  with pivot pins  13  on the inner and outer ends to allow for the vane to pivot within the flow path. The pivot pins  13  fit within holes formed in the outer shroud  14  and an inner shroud  15  that also form the flow path through the inlet guide vane assembly. 
     A sync ring  16  is used to move the vanes within the shroud assembly. The sync ring  16  is a full 360 degree annular piece that slides within an inner facing annular groove  17  arranged within the outer shroud  14  member as seen in  FIG. 1 . As the sync ring  16  is moved circumferentially within the annular groove  17 , the guide vanes  11  are pivoted to the different positions.  FIG. 2  shows the guide vane assembly from the trailing edge side  18  of the vanes  11  with the leading edge side pivot pins  13  shown. The sync ring  16  is connected to the vanes  11  near the trailing edge side. A driving linkage  19  connects the sync ring  16  to an actuator that is used to move the sync ring and thus position the guide vanes  11 . 
     In one embodiment, the sync ring  16  includes a radial pin that slides within a slot formed within the casing to connect the sync ring  16  to the actuator outside of the casing. In this embodiment, the driving linkage  19  would be connected to the actuator outside of the casing. In another embodiment, the driving linkage would be contained within the casing and another connection would be used to connect the actuator to the driving linkage through a hole or slot within the casing. 
     The leading edge side pins  13  are pivotable within a slider  21  that is formed as a loader slot bearing to allow for both circumferential movement and axial movement of the pins  13  when the guide vanes are moved. The slider linkage  21  includes a spherical piece that slides within a spherical hole formed within the outer shroud, and a cylindrical hole formed within the spherical piece in which the pin  13  rotates. Because the trailing edge side pins connected to the sync ring  16  only follows a circumferential motion, the leading edge side pins  13  must be allowed to move in both the circumferential direction and the axial direction (the axis of the engine) when the vanes are pivoted.  FIG. 3  shows a detailed view of the slider with the pin  13  extending through the central hole formed within the spherical piece. 
       FIG. 4  shows a “pancake” (round actuator with a height much less than the diameter) actuator  30  used to move the sync ring  16  for positioning the guide vanes  11 . The pancake actuator  30  is a three vane actuator with a relatively short height to minimize the space required for the actuators around the engine casing and to minimize the weight of the actuators. The prior art guide vane actuators are larger linear actuators that require at least twice the overall length for the same movement of the output mechanism that is used to move the sync ring  16 .  FIG. 5  shows an exploded view of the parts that make up the pancake actuator  30  and includes a stator with three vanes  32  offset at 120 degrees, a rotor  33  that forms the pressure chambers  34  for each of the vanes  32 , an actuator arm  35  extending from the rotor  33  that connects to the driving linkage  19  of the sync ring  16 , and an outer bearing ring  36  that is bolted onto an outer surface of the stator and rotatably secures the rotor  33  to the stator  31 .  FIG. 4  shows the arrangement with the outer bearing ring  33  securing the rotor  33  to the stator  31  with roller bearings  37  formed around the inner side of the outer bearing ring  33  and the outer side of the rotor  33  to allow for relative rotation.  FIG. 4  shows the actuator arm  35  in the two extreme positions. A number of bolts  38  secure the outer bearing ring  36  to the stator  31 . 
       FIG. 6  shows a cut-away view of the actuator  30  with an inner bearing ring  39  rotatably secured to an inner surface of the stator  31 , the inner bearing ring  39  being secured to the rotor  33 .  FIG. 7  shows the rotor  31  with the outer bearing  37  and the three vanes  32  extending up from the base of the disc of the rotor  31 . The inner bearings  41  are shown in the central opening of the rotor  31 . One of the benefits of the pancake actuator is that the power output of the actuator can be increased by using vanes  32  with taller heights so that the same input driving pressure can produce a larger output force to drive the sync ring  16 . 
       FIGS. 8-10  show a segmented guide vane assembly with tip clearance control.  FIG. 10  shows a plurality of shroud segments  51  each having a plurality of vanes  52  extending inward into a flow path. An annular sync ring  53  is positioned outside of the shroud segments  51  and is connected to the segments  51  by a linkage that produces a radial movement of the segments  51  to control the vane tip clearance with the inner shrouds of the engine.  FIG. 8  shows an isometric view of one of the linkages between the shroud segment  51  and the sync ring  53 . Each shroud segment  51  includes two raised portions  54  near the ends and on both the forward side and the aft side where each raised portion  54  includes a hole in which an eccentric cam pivots. The eccentric cam  55  includes a hole to allow for a pivot arm  56  to slide. The pivot arm  56  includes a radial extending piece that fits within a slider (loader slot bearing)  57  fitted within a spherical hole in the sync ring  53 . The slider  57  allows for the circumferential movement of the sync ring  53  to produce a pivoting of the shaft of the pivot arm  56  and thus a rotation of the shaft that rotates within the eccentric cam  55  fitted within the raised portions  54  of the shroud segments  51 .  FIG. 9  shows a side view of the pivot arm linkage between the raised portion  55  of the shroud segment  51  and the sync ring  53 . 
     The sync ring  53  can be connected to the pancake actuator described above for actuating the sync ring  53 . When the sync ring  53  is moved in the circumferential direction, the pivot arms  56  are rotated so that the shroud segments  51  are moved in the radial direction of the engine to control the guide vane tip clearance. If the two position pancake actuator  30  is used, then the vane tip clearance control has two positions: a first position with the vane tips moved the further inward and a second position with the vane tips moved furthest outward. 
     The pancake actuator of the present invention can be supplied with a differential pressure that is bled off from the compressor using one of the stages that has a pressure level high enough to drive the actuator and move the sync ring. Since the actuator is of the type with a high pressure side and a low pressure side, connecting the low pressure chamber to the ambient while connecting the high pressure side to the compressor stage will provide enough differential pressure to drive the actuator. Since a differential pressure is being used as the motive power source, very little fluid flow is used so that the compressed air from the compressor is not wasted. Also, more than one pancake actuator can be placed around the outer shroud and connected to the sync ring in order to produce enough driving force to rotate the sync ring. In one embodiment, four pancake actuators can be evenly spaced at around 90 degrees from each other around the outer shroud casing and all connected to the sync ring by a separate actuator arm. If more power is needed or the use of less that four pancake actuators is required, the actuator vanes can be easily replaced with larger or taller vanes and the rotor can be replaced with one that accommodates the taller vanes in order to produce more power from the same differential pressure source.