Abstract:
A variable vane actuator assembly for a gas turbine engine according to an exemplary aspect of the present disclosure includes, among other things, a plurality of vanes. A synchronization rings surrounds and is mechanically linked to drive the vanes to pivot for varying an angle of the vanes. A crank shaft is mechanically linked to the synchronization ring for rotating the synchronization ring. A fluid actuated rotary motor is located at an end of the crank shaft for selectively rotating the crank shaft.

Description:
BACKGROUND 
       [0001]    This application relates to a system for pivoting a plurality of variable stator vanes, such as in a gas turbine engine for example. 
         [0002]    A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. 
         [0003]    In general, the compressor and turbine section include circumferentially spaced vanes forming vane stages that are axially separated from adjacent vane stages by rotor blades. Some gas turbine engines include variable vanes that pivot about an axis to vary an angle of the vane to optimize engine performance. The variable vanes are mechanically connected to a synchronization ring by a vane arm to drive the variable vane to pivot as the synchronization ring is rotated. The synchronization ring is rotated by crank shaft that is mechanically connected to the synchronization ring. As the synchronization ring is rotated in a circumferential direction around the engine, the relative angle of variable vanes at each stage is varied in order to modify the amount of airflow through the engine. 
         [0004]    Linear actuators are known in the art to rotate the crank shaft but generally require several additional moving parts to convert linear motion to rotary motion, with each of the moving parts contributing to vane position error. Engine stability and fuel consumption is related to the accuracy of positioning the angle of the vanes. 
       SUMMARY 
       [0005]    A variable vane actuator assembly according to an exemplary aspect of the present disclosure includes, among other things, a plurality of vanes. A synchronization ring is mechanically linked to drive the vanes to pivot for varying an angle of the vanes. A crank shaft is mechanically linked to the synchronization ring. A fluid actuated rotary motor is located at an end of the crank shaft for selectively rotating the crank shaft. 
         [0006]    In a further non-limiting embodiment of the foregoing variable vane actuator assembly, the rotary motor includes a first engagement feature and the crank shaft includes a second engagement feature connected to the first engagement feature. 
         [0007]    In a further non-limiting embodiment of either of the foregoing variable vane actuator assemblies, the first engagement feature and the second engagement feature are splines. 
         [0008]    In a further non-limiting embodiment of any of the foregoing variable vane actuator assemblies, the first engagement feature and the second engagement feature are fastened to each other. 
         [0009]    In a further non-limiting embodiment of any of the foregoing variable vane actuator assemblies, the crank shaft includes a generally tubular configuration. 
         [0010]    In a further non-limiting embodiment of any of the foregoing variable vane actuator assemblies, a ratio of an outer radius to an inner radius of the crank shaft is less than 2:1. 
         [0011]    In a further non-limiting embodiment of any of the foregoing variable vane actuator assemblies, the variable vane actuator assembly includes a rotary position sensor for measuring an angular orientation of the rotary motor. 
         [0012]    In a further non-limiting embodiment of any of the foregoing variable vane actuator assemblies, the rotary motor is in fluid communication with a fuel source. 
         [0013]    In a further non-limiting embodiment of any of the foregoing variable vane actuator assemblies, the rotary motor includes an actuator vane for selectively rotating the crank shaft when an amount of fluid pressure is applied to the actuator vane. 
         [0014]    A gas turbine engine according to another exemplary aspect of the present disclosure includes, among other things, a compressor section including a rotor section and a variable vane section adjacent to the rotor section. The variable vane section includes a plurality of vanes mounted to be capable of pivoting. A synchronization ring surrounds and is mechanically linked to drive the vanes to pivot for varying an angle of the vanes. A crank shaft is mechanically linked to the synchronization ring. A fluid actuated rotary motor is located at an end of the crank shaft for selectively rotating the crank shaft. 
         [0015]    In a further non-limiting embodiment of the foregoing gas turbine engine, the crank shaft and the rotary motor are arranged about a first axis defined by the crank shaft, the first axis being parallel to a longitudinal axis defined by the engine. 
         [0016]    In a further non-limiting embodiment of either of the foregoing gas turbine engines, the rotary motor includes a first engagement feature and the crank shaft includes a second engagement feature connected to the first engagement feature. 
         [0017]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the first engagement feature and the second engagement feature are splines. 
         [0018]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the first engagement feature and the second engagement feature are fastened to each other. 
         [0019]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the crank shaft includes a generally tubular configuration. 
         [0020]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, a ratio of an outer radius to an inner radius of the crank shaft is less than 2:1. 
         [0021]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the gas turbine engine includes a rotary position sensor for measuring an angular orientation of the rotary motor. 
         [0022]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the rotary motor is in fluid communication with a fuel source. 
         [0023]    In a further non-limiting embodiment of any of the foregoing gas turbine engines, the rotary motor includes an actuator vane for selectively rotating the crank shaft when an amount of fluid pressure is applied to the actuator vane. 
         [0024]    Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples. 
         [0025]    These and other features disclosed herein can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a schematic view of an example gas turbine engine. 
           [0027]      FIG. 2  is a perspective view of a variable vane actuator assembly. 
           [0028]      FIG. 3  is a perspective view of a portion of the variable vane actuator assembly of  FIG. 2 . 
           [0029]      FIG. 4  is a perspective view of a portion of the variable vane actuator assembly of  FIG. 2 . 
           [0030]      FIG. 5  is an exploded view of a rotary actuator. 
           [0031]      FIG. 6  is a schematic view of a portion of the variable vane actuator assembly of  FIG. 5  in communication with a fuel source. 
           [0032]      FIG. 7  is a perspective view of a crank shaft. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]      FIG. 1  schematically illustrates an example gas turbine engine  20  that includes a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmenter section (not shown) among other systems or features. The fan section  22  drives air along a bypass flow path B while the compressor section  24  draws air in along a core flow path C where air is compressed and communicated to a combustor section  26 . In the combustor section  26 , air is mixed with fuel and ignited to generate a high pressure exhaust gas stream that expands through the turbine section  28  where energy is extracted and utilized to drive the fan section  22  and the compressor section  24 . 
         [0034]    Although the disclosed non-limiting embodiment depicts a turbofan gas turbine engine, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines; for example a turbine engine including a three-spool architecture in which three spools concentrically rotate about a common axis and where a low spool enables a low pressure turbine to drive a fan via a gearbox, an intermediate spool that enables an intermediate pressure turbine to drive a first compressor of the compressor section, and a high spool that enables a high pressure turbine to drive a high pressure compressor of the compressor section. 
         [0035]    The example engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
         [0036]    The low speed spool  30  generally includes an inner shaft  40  that connects a fan  42  and a low pressure (or first) compressor section  44  to a low pressure (or first) turbine section  46 . The inner shaft  40  drives the fan  42  through a speed change device, such as a geared architecture  48 , to drive the fan  42  at a lower speed than the low speed spool  30 . The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure (or second) compressor section  52  and a high pressure (or second) turbine section  54 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via the bearing systems  38  about the engine central longitudinal axis A. 
         [0037]    A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . In one example, the high pressure turbine  54  includes at least two stages to provide a double stage high pressure turbine  54 . In another example, the high pressure turbine  54  includes only a single stage. As used herein, a “high pressure” compressor or turbine experiences a higher pressure than a corresponding “low pressure” compressor or turbine. 
         [0038]    The example low pressure turbine  46  has a pressure ratio that is greater than about 5. The pressure ratio of the example low pressure turbine  46  is measured prior to an inlet of the low pressure turbine  46  as related to the pressure measured at the outlet of the low pressure turbine  46  prior to an exhaust nozzle. 
         [0039]    A mid-turbine frame  58  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The mid-turbine frame  58  further supports bearing systems  38  in the turbine section  28  as well as setting airflow entering the low pressure turbine  46 . 
         [0040]    The core airflow C is compressed by the low pressure compressor  44  then by the high pressure compressor  52  mixed with fuel and ignited in the combustor  56  to produce high speed exhaust gases that are then expanded through the high pressure turbine  54  and low pressure turbine  46 . The mid-turbine frame  58  includes vanes  60 , which are in the core airflow path and function as an inlet guide vane for the low pressure turbine  46 . Utilizing the vane  60  of the mid-turbine frame  58  as the inlet guide vane for low pressure turbine  46  decreases the length of the low pressure turbine  46  without increasing the axial length of the mid-turbine frame  58 . Reducing or eliminating the number of vanes in the low pressure turbine  46  shortens the axial length of the turbine section  28 . Thus, the compactness of the gas turbine engine  20  is increased and a higher power density may be achieved. 
         [0041]    The disclosed gas turbine engine  20  in one example is a high-bypass geared aircraft engine. In a further example, the gas turbine engine  20  includes a bypass ratio greater than about six (6), with an example embodiment being greater than about ten (10). The example geared architecture  48  is an epicyclical gear train, such as a planetary gear system, star gear system or other known gear system, with a gear reduction ratio of greater than about 2.3. 
         [0042]    In one disclosed embodiment, the gas turbine engine  20  includes a bypass ratio greater than about ten (10:1) and the fan diameter is significantly larger than an outer diameter of the low pressure compressor  44 . It should be understood, however, that the above parameters are only exemplary of one embodiment of a gas turbine engine including a geared architecture and that the present disclosure is applicable to other gas turbine engines. 
         [0043]    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. The flight condition of 0.8 Mach and 35,000 ft., with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (&#39;TSFC&#39;)”—is the industry standard parameter of pound-mass (lbm) of fuel per hour being burned divided by pound-force (lbf) of thrust the engine produces at that minimum point. 
         [0044]    “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.50. In another non-limiting embodiment the low fan pressure ratio is less than about 1.45. 
         [0045]    “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 “Low corrected fan tip speed”, as disclosed herein according to one non-limiting embodiment, is less than about 1150 ft/second. 
         [0046]    The example gas turbine engine includes the fan  42  that comprises in one non-limiting embodiment less than about  26  fan blades. In another non-limiting embodiment, the fan section  22  includes less than about 20 fan blades. Moreover, in one disclosed embodiment the low pressure turbine  46  includes no more than about 6 turbine rotors schematically indicated at  34 . In another non-limiting example embodiment the low pressure turbine  46  includes about 3 turbine rotors. A ratio between the number of fan blades  42  and the number of low pressure turbine rotors is between about 3.3 and about 8.6. The example low pressure turbine  46  provides the driving power to rotate the fan section  22  and therefore the relationship between the number of turbine rotors  34  in the low pressure turbine  46  and the number of blades  42  in the fan section  22  disclose an example gas turbine engine  20  with increased power transfer efficiency. 
         [0047]      FIG. 2  illustrates an example variable vane assembly  62  that includes a rotary actuator  64  and a crank shaft  66 . The rotary actuator  64  rotates about an axis B extending along a length of the crank shaft  66  and parallel to the engine central longitudinal axis A. The rotary actuator  64  is located at an end of the crank shaft  66 . The crank shaft  66  includes a generally tubular configuration. A ratio of the outer radius to the inner radius may be less than 2:1 for minimizing the amount of stress and deflection due to torsional loads. 
         [0048]    The crank shaft  66  is mechanically linked to a plurality of synchronization rings  68  via an actuator linkage  74 , as shown in  FIG. 3 . Each of the synchronization rings  68  engages an outer surface of the high pressure compressor case  72 . A plurality of variable vanes  76  (shown schematically in  FIG. 1 ) are arranged about the engine central longitudinal axis A and are mechanically linked to the synchronization rings  68 . Each of the synchronization rings  68  is connected to either the inlet guide vanes  77  or the stator vanes  79  of the high pressure compressor section  52 . 
         [0049]    Referring to  FIG. 4 , a first end of the vane arm  78  extends through the compressor case  72  and is fixedly attached to an end portion of a corresponding variable vane  76 . A second end of the vane arm  78  is rotatably attached to an adjacent synchronization ring  68 . Therefore, as the crank shaft  66  rotates to extend or retract the actuator linkages  74 , the synchronization rings  68  rotate around the compressor case  72  along arc  81  varying the angular position of the variable vanes  76  to adjust the amount of air drawn along the core flow path C. Although a single crank shaft  66  is shown in this example, the synchronization rings  68  may be rotated by more than one crank shaft. The variable vane assembly  62  also includes a pair of mounts  70  fixedly attached to a high pressure compressor case  72  for supporting the rotary actuator  64  and the crank shaft  66 , as best seen in  FIG. 3 . 
         [0050]    As shown in  FIG. 5 , the rotatory actuator  64  includes an example housing  80 . The housing  80  includes a main body  82  and an end portion  84  that cooperate to define a cavity  86 . The main body  82  defines a pair of actuator ports  88  for providing fluid communication between a fluid source and the cavity  86 . In one example, the fluid source is a fuel source such as a fuel pump  89  including a pair of complementary ports  91  connected to the actuator ports  88  by a pair of fuel lines  93  (shown schematically in  FIG. 6 ). Other types of fluid sources may be used such as hydraulic or pneumatic sources. The rotary actuator  64  also includes an actuator vane  90  disposed in the cavity  86  and an inner drive  92  connected to the actuator vane  90  partially disposed in the cavity  86  and extending through the end portion  84 . The actuator vane  90  and the inner drive  92  may be integrally formed. The rotary actuator  64  also includes a rotary position sensor  94  for directly measuring an angular orientation of the crank shaft  66 . In another example, the rotary position sensor  94  is located adjacent the crank shaft  66 . A controller  200 , shown schematically, reads the measurement from the rotary position sensor  94  for controlling the amount of fuel provided to the ports  88  from the fuel pump  89 . Although a single-vane rotary actuator is shown in this example, a dual-vane rotary actuator may be used. The rotary vane style offers the zero backlash benefit. Other types of rotary actuators may also be used such as piston rack and pinion or screw-helical configurations. 
         [0051]    The inner drive  92  includes a first engagement feature  96 . The crank shaft  66  includes a second engagement feature  98 , as shown in  FIG. 7 . In one example, the engagement features  96 ,  98  each define a spline whereby the crank shaft  66  partially receives the inner drive  92 . Accordingly, the direct connection between features  96 ,  98  prevents relative movement between the rotary actuator  64  and the crank shaft  66 , thereby reducing inaccuracy caused by backlash. In another example, the spline is tapered. It should be appreciated that the engagement features  96 ,  98  may be directly connected to each other by other arrangements such as a pair of complementary gears, a notch and a groove, or by at least one fastener. In another example, the engagement features  96 ,  98  are welded to each other. 
         [0052]    During operations, the controller  200  compares the angular orientation of the actuator vane  90  to one or more operating conditions of the aircraft including airspeed, throttle setting and density altitude. The controller sends a signal to the fuel pump  89  to adjust the amount of fuel provided each of the ports  88  of the actuator  64  once the angular orientation exceeds a predetermined range corresponding to adequate air flow along the core flow path C. Engine stability and fuel consumption is related the accuracy of positioning the angle of the vanes. Thus, the usage of a rotary actuator directly connected to the crank shaft reduces the amount of vane position error due to the configuration of the actuator and associated backlash, the number of mechanical connections in the system, and component wear. 
         [0053]    Although the disclosed example is described in reference to a high pressure compressor  52 , it is within the contemplation of this disclosure that it be utilized with another compressor or turbine section. 
         [0054]    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. The scope of legal protection given to this disclosure can only be determined by studying the following claims.