Patent Publication Number: US-7223066-B2

Title: Variable vane arrangement for a turbomachine

Description:
FIELD OF THE INVENTION 
   The present invention relates to a variable vane arrangement for a turbomachine, and in particular relates to a variable vane arrangement for a compressor of gas turbine engine. 
   BACKGROUND OF THE INVENTION 
   A variable vane arrangement for a turbomachine, as disclosed in our UK patent application GB2339244A, comprises a plurality of circumferentially arranged vanes, a plurality of operating levers and a control ring. Each vane comprises an upstream portion secured to a casing and a movable downstream portion pivotally mounted to the casing of the turbomachine. Each operating lever is pivotally mounted at a first end to the control ring and each operating lever is mounted at second end to a spindle of the movable downstream portion of a respective one of the vanes. Rotation of the control ring causes the levers to adjust the angular position of the movable downstream portions of the vanes. 
   In this variable vane arrangement the movable downstream portions of the vanes are pivotally mounted about an axis adjacent the upstream ends of the movable downstream portions and downstream of the downstream ends of the fixed upstream portions of the vanes. 
   Current designs of variable vane arrangements use expensive and difficult to produce drive features between the operating levers and the spindles of the vanes. The drive features may comprise highly toleranced flat surfaces, which require intricate removal tooling and which may damage the lever and spindle on removal. If a clearance is provided to enable easier fitting and removal, there is an increase in the possibility of errors in the angular position of the vanes. During build of the variable vane arrangement it is difficult to both load the variable vane and maintain it in position while attempting to fit the highly accurate drive features. 
   SUMMARY OF THE INVENTION 
   Accordingly the present invention seeks to provide a novel variable vane assembly for a turbomachine which reduces, preferably overcomes, the above mentioned problems. 
   Accordingly the present invention provides a variable vane arrangement for a turbomachine comprising a plurality of circumferentially arranged vanes, a plurality of operating levers and a control ring, each vane being pivotally mounted to a casing of the turbomachine, each operating lever being pivotally mounted at a first end to the control ring, each operating lever being mounted at second end to a respective one of the vanes, the second end of each operating lever comprising a multi-sided aperture, each vane having a multi-sided spindle which locates in the multi-sided aperture of the respective operating lever, each operating lever having a drive member located in the multi-sided aperture and around the multi-sided spindle of the respective vane, each drive member engaging the respective multi-sided aperture and the respective multi-sided spindle to transmit drive from the operating lever to the vane. 
   Preferably the sides of each multi-sided aperture taper from a first end adjacent the respective vane to a second end remote from the respective vane such that the cross-sectional area of the aperture increases from the first end to the second end. 
   Preferably the sides of each multi-sided spindle taper from a first end adjacent the respective vane to a second end remote from the respective vane such that the cross-sectional area of the spindle increases from the second end to the first end. 
   Preferably each drive member has multiple sides on an inner surface to engage the respective multi-sided spindle and multiple sides on an outer surface to engage the respective multi-sided aperture. 
   Preferably each drive member tapers from a first end adjacent the respective vane to a second end remote from the respective vane such that the cross-sectional area of the drive member increases from the first end to the second end. 
   Preferably the sides on the inner surface taper from the first end to the second end and the sides on the outer surface taper from the first end to the second end. 
   Preferably each drive member comprises a base portion and a plurality of portions extending into the respective multi-sided aperture. 
   Preferably the base portion of each drive member is secured to the spindle of the respective vane to clamp the respective operating lever. 
   Preferably the base portion of each drive member is secured to the spindle of the respective vane by a screw or a bolt. 
   Preferably each multi-sided aperture comprises three, four, five or six sides, each multi-sided spindle has an equal number of sides to the respective multi-sided aperture. 
   Preferably the drive member comprises a ductile material. Preferably the ductile material comprises titanium or a plastic. 
   Preferably each variable vane comprises an upstream portion fixed to the casing and a movable downstream portion pivotally mounted to the casing. 
   Preferably the turbomachine is a gas turbine engine, preferably a turbojet or turbofan gas turbine engine. 
   Preferably the variable vane arrangement is for a compressor or a fan of a gas turbine engine. 
   The present invention also provides a variable vane operating lever comprising a first end and a second end, the first end being adapted to be pivotally mounted to a control ring, the second end having a multi-sided aperture to engage a multi-sided spindle of a variable vane. 
   Preferably the sides of the multi-sided aperture taper from a first end to a second end such that the cross-sectional area of the aperture increases from the first end to the second end. 
   The present invention also provides a variable vane drive member comprising multiple sides on an inner surface adapted to engage a multi-sided spindle of a variable vane and multiple sides on an outer surface adapted to engage a multi-sided aperture of an operating lever. 
   Preferably the drive member tapers from a first end to a second end such that the cross-sectional area of the drive member increases from the first end to the second end. 
   Preferably the sides on the inner surface taper from the first end to the second end and the sides on the outer surface taper from the first end to the second end. 
   Preferably the drive member comprises a base portion and a plurality of portions extending into the multi-sided aperture. 
   Preferably the base portion of each drive member is adapted to be secured to the spindle of the variable vane. 
   Preferably the drive member comprises a ductile material. Preferably the ductile material comprises titanium or a plastic. 
   The present invention also provides a variable vane arrangement for a turbomachine comprising a vane and an operating lever, the vane being pivotally mounted to a casing of the turbomachine, the operating lever being mounted at one end to the vane, the end of the operating lever comprising a multi-sided aperture, the vane having a multi-sided spindle which locates in the multi-sided aperture of the operating lever, the operating lever having a drive member located in the multi-sided aperture and around the multi-sided spindle of the vane, the drive member engaging the multi-sided aperture and the multi-sided spindle to transmit drive from the operating lever to the vane. 

   
     BRIEF DESCRIPTION OF THE DRAWING  
     The present invention will be more fully described by way of example with reference to the accompanying drawings in which: 
       FIG. 1  is a partially cut away view of a turbofan gas turbine engine having a variable vane arrangement according to the present invention. 
       FIG. 2  is an enlarged cross-sectional view of a variable vane arrangement according to the present invention. 
       FIG. 3  is a cross-sectional view through the variable vane arrangement shown in  FIG. 2 . 
       FIG. 4  is an exploded view of a spindle of a vane, an operating lever and a drive member of the variable vane arrangement shown in  FIG. 2 . 
       FIG. 5  is an enlarged cross-sectional view of part fan alternative operating lever and drive member of a variable vane arrangement. 
       FIG. 6  is a perspective view of the alternative operating lever shown in  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A turbofan gas turbine engine  10 , as shown in  FIG. 1 , comprises in axial flow series an intake  12 , a fan section  14 , a compressor section  16 , a combustion section  18 , a turbine section  20  and a core exhaust  22 . The turbine section  20  comprises a low-pressure turbine (not shown) arranged to drive a fan  24  in the fan section  14  and a high-pressure turbine (not shown) arranged to drive a high-pressure compressor  28  in the compressor section  16 . The turbine section  20  may also comprise an intermediate-pressure turbine (not shown) arranged to drive an intermediate-pressure compressor  26  in the compressor section  16 . 
   The intermediate-pressure compressor  26  comprises a casing  30  and a rotor  32  arranged for rotation about an axis X. The rotor  32  carries one or more axially spaced stages of circumferentially arranged radially outwardly extending compressor blades  34 . The intermediate-pressure compressor  26  also comprises a variable vane arrangement  36  for adjusting the angle of the airflow onto the stage of compressor blades  34  immediately downstream thereof. 
   The variable vane arrangement  36 , as shown more clearly in  FIGS. 2 to 4 , comprises a plurality of radially extending circumferentially arranged variable vanes  38 , a plurality of operating levers  64 , a control ring  66  and an actuator (not shown). 
   Each variable vane  38  comprises a fixed upstream portion  40  and a movable downstream portion  42 . The fixed upstream portion  40  of each of the variable vanes  38  is secured at its radially outer end to the casing  30  and is secured at its radially inner end to a ring  44 . The movable downstream portion  42  each of the variable vanes  38  is pivotally mounted at its radially outer end in a respective aperture  46  in the casing  30  and is pivotally mounted at its radially inner end in a respective aperture  48  in the ring  44 . The movable downstream portion  42  of each of the variable vanes  38  is pivotally mounted about one of a plurality of circumferentially spaced axes Y arranged substantially in a plane arranged perpendicularly to the axis X of the rotor  32 . The axes Y are arranged adjacent the upstream ends  52  of the movable downstream portions  42  of the variable vanes  38  and adjacent, slightly downstream of, the downstream ends  50  of the fixed upstream portions  40  of the variable vanes  38 . The ring  44  comprises an upstream portion  44 A and a downstream portion  44 B, which are joined together along the radial plane containing the pivot axes Y by axially extending bolts and nuts extending through apertures in flanges on the upstream portion  44 A and downstream portion  44 B. The ring  44  has a plurality of circumferentially spaced apertures  48  defined between the edges of the upstream portion  44 A and the downstream portion  44 B of the ring  44 . The radially inner end of the movable downstream portion  42  of each of the variable vanes  38  is provided with a cylindrical spindle  54  which locates coaxially in a bearing member, or bush,  56  in the respective aperture  48  in the ring  44 . The radially outer end of the movable downstream portion  42  of each of the variable vanes  38  is provided with a cylindrical bearing member  58  and a spindle  60 . The bearing member  58  locates coaxially in an increased diameter portion  62  of the respective aperture  46  in the casing  30 . 
   Each operating lever  64  is pivotally mounted at a first end  68  to the control ring  66  and each operating lever  64  is pivotally mounted at a second end  70  to the movable downstream portion  42  of a respective one of the variable vanes  38 . The second end  70  of each operating lever  64  forms a cylindrical bush for location coaxially in the respective aperture  46  in the casing  30 . The second end  70  of each operating lever  64  comprises a multi-sided aperture  72  and the movable downstream portion  42  of each variable vane  38  has a multi-sided spindle  60  which locates in the multi-sided aperture  72  of the respective operating lever  64 . Each operating lever  64  has a drive member  74  located in the multi-sided aperture  72  and around the multi-sided spindle  60  of the movable downstream portion  42  of the respective variable vane  38 . Each drive member  74  engages the respective multi-sided aperture  72  and the respective multi-sided spindle  60  to transmit drive from the operating lever  64  to the movable downstream portion  42  of the respective variable vane  38 . 
   The sides  76  of each multi-sided aperture  72  taper from a first end  78  adjacent the movable downstream portion  42  of the respective variable vane  38  to a second end  80  remote from the movable downstream portion  42  of the respective variable vane  38 . Thus the cross-sectional area of the aperture  72  increases from the first end  78  to the second end  80 . The sides of each multi-sided spindle  60  taper from a first end  82  adjacent the movable downstream portion  42  of the respective variable vane  38  to a second end  84  remote from the movable downstream portion  42  of the respective variable vane  38 . Thus the cross-sectional area of the spindle  60  increases from the second end  84  to the first end  82 . 
   Each drive member  74  has multiple sides on an inner surface  86  to engage the respective multi-sided spindle  60  and multiple sides on an outer surface  88  to engage the respective multi-sided aperture  72  in the second end  70  of the operating lever  64 . Each drive member  74  tapers from a first end  90  adjacent the movable downstream portion  42  of the respective variable vane  38  to a second end  92  remote from the movable downstream portion  42  of the respective variable vane  38 . Thus the cross-sectional area of the drive member  74  increases from the first end  90  to the second end  92 . The sides on the inner surface  86  taper from the first end  90  to the second end  92  and the sides on the outer surface  88  taper from the first  90  end to the second end  92 . Each drive member  74  comprises a base portion  94  and a plurality of portions  96 ,  98 , corresponding in number to the number of sides of the aperture  72  and the spindle  60 , extending into the respective multi-sided aperture  72 . Each drive member  74  comprises a ductile material, for example the ductile material comprises titanium, a plastic or other suitable material. The drive member  74  is split at the corner positions such that the portions  96 ,  98  are separate from each other so that they act as a collet to maintain drive from the operating lever  64  to the spindle  60  of the variable vane  38 . 
   The base portion  94  of each drive member  74  is secured to the spindle  60  of the movable downstream portion  42  of the respective variable vane  38  by a screw, or a bolt,  100 . Each screw, or bolt,  100  extends though an aperture  102  in the base portion  94  of the drive member  74  and into a threaded aperture  104  in the spindle  60  of the variable vane  38 . Each multi-sided aperture  72  comprises three, four, five, six or more sides, each multi-sided spindle  60  has an equal number of sides to the respective multi-sided aperture  72  in the second end  70  of the operating lever  64 . Similarly the each drive member  74  has an equal number of side to the respective multi-sided aperture  72  and the respective spindle  60 . 
   Each aperture  72  in the second end  70  of the respective operating lever  64  has a increased dimension seating position  112  at the end  80  remote from the movable downstream portion  42  of the variable vane  38 . The seating position  112  has substantially the same dimensions and shape as the base portion  94  of the respective drive member  74 . The base portion  94  of the drive member  74  locates on the seating position  112  in the aperture  72  in the operating lever  64  when the bolt  100  is fully tightened. In this example the seating position  112  and the base portion  94  are circular, but other suitable shapes may be used. 
   The first end  68  of each operating lever  64  is pivotally mounted to the control ring  66  by a respective pin, or bolt,  106 . Each pin, or bolt,  106  passes through an aperture  108  in the first end  68  of the operating lever  64  and the pin, or bolt,  106  is secured, threaded, into apertures  109 ,  110  in the control ring  66 . 
   The control ring  66  is arranged coaxially around the axis X of the rotor  32  of the intermediate-pressure compressor  26  and is rotatably mounted on the casing  30  so as to vary the angles of the variable vanes  38 . An actuator (not shown) is provided to rotate the control ring  66  and the actuator may be a hydraulic, pneumatic or electric actuator. 
   To assemble the variable vane arrangement  36  the movable downstream portion  42  of each variable vane  38  is located in the casing  30  and the spindle  60  is inserted into the inner end of the respective aperture  46  in the casing  30 . The increased clearance provided by the aperture  46  in the casing  30  allows the movable downstream portion  42  of the variable vane  38  to be manoeuvred into position. The second end  70  of the operating lever  64  is then loaded into the radially outer end of the respective aperture  46  in the casing  30  around the spindle  60  on the movable downstream portion  42  of the respective variable vane  38 . The movable downstream portion  42  of the variable vane  38  may be further adjusted and set in position along with any end float. The drive member  74  is then loaded into the aperture  72  in the second end  70  of the operating lever  64 . The bolt  100  is then used to secure the drive member  74  and second end  70  of the operating lever  64  to the spindle  60  of the variable vane  38 . The tightening of the bolt  100  causes the drive member  74  to grip the spindle  60  of the variable vane  38  and to pull the drive member  74  into the seating position  112  around the aperture  72  in the second end  70  of the operating lever  64 . Any variation in geometry and/or tolerance is taken up either by movement of the drive member  74  along the taper or by deformation of the drive member  74 . Once fully assembled substantially zero backlash is achieved in the drive between the operating lever  64  and the spindle  60  of the variable vane  38 , thus eliminating errors in the angle setting of the variable vane  38 . 
   The spindle  54  of the movable downstream portion  42 , and the associated bush  56 , of each variable vane  38  is inserted into the upstream portion of the respective aperture  48  in the upstream portion  44 A of the ring  44  at any time after the spindle  60  of the movable downstream portion  42  of the variable vane  38  has been inserted into the respective aperture  48  in the casing  30 . The downstream portion  44 B of the ring  44  is then secured to the upstream portion  44 A of the ring  44 , to complete the apertures  46  around the spindles  54  of the movable downstream portion  42  of the variable vanes  38 , by fastening the flanges together using the bolts and nuts. 
   The present variable vane arrangement has many advantages. The operating lever incorporates a bush at the end mounted onto the spindle of the variable vane to provide an increased surface area of contact with the spindle of the variable vane and thereby reduce stress loads in the spindle of the variable vane. The drive member is provided to take up the remaining space between the spindle of the variable vane and the aperture in the end of the operating lever to provide the required drive. The drive member is provided with a double taper, there is a taper on its inner surface and its outer surface, so that when the bolt is tightened to lock the drive member and operating lever to the spindle of the variable vane, the drive member removes any clearances/spaces between the operating lever and the spindle of the variable vane and hence removes/minimises errors in the setting of the angles of the variable vane. The drive member is split to provide separate portions, which allow the drive member to act as a collet. The drive member is manufactured from a ductile material, which allows the drive member to deform, to limit damage to the operating lever and the spindle of the variable vane. The drive member is a disposable item, which may be replaced during regular maintenance and/or servicing of the variable vane arrangement. The drive member moves along the double taper to take up its own seating position and thus take up manufacturing errors in the spindle and/or the aperture in the operating lever. The variable vane arrangement is easier to build. 
   The variable vane arrangement may be a variable inlet guide vane for the compressor or the variable vane arrangement may be arranged at any other suitable position in the compressor. 
   The embodiment of variable vane arrangement  36 B, as shown in  FIGS. 5 and 6  is substantially the same as that shown in  FIGS. 2 to 4  and like parts are denoted by like numerals. The embodiment in  FIGS. 5 and 6  differs in that the operating lever  64  is provided with a plurality of apertures  114  to reduce the weight of the operating lever. In addition the second end  70  of each operating lever  64  is provided with a radially inwardly extending flange  116  around the aperture  72  and spaced axially from the seating position  112 . The base portion  94  of each drive member  74  is provided with an annular groove  118  which extends radially into the periphery of the base portion  94 . A corresponding ring  120  is provided within the annular groove  118  of each drive member  74  to act as a secondary retention feature for the operating levers  68  if the bolt fails. The outer diameter of the ring  120  is greater than the inner diameter of the flange  116 . The rings  120  may be circlips or split rings to allow installation of the rings  120  and drive members  74  within the second ends  70  of the operating levers  64  while retaining the drive members  74  and operating levers  64  on the spindles  54  of the variable vanes  38 . 
   The integral bush on the operating lever is arranged to aid retention of the operating lever on the spindle of the vane in the event of a failure of the bolt. The integral bush also determines the distance between the second end of the operating lever and a datum face on top of the spindle of the vane. 
   It is preferred that the axes of rotation of the variable vanes are inclined to the plane arranged perpendicularly to the axis of the rotor, for example at an angle of 9°-10° forward of the plane. In the event of a bolt failure the operating lever is maintained in a boss around the aperture in the casing because of the integral bush on the operating lever and because the axes of rotation of the variable vanes are inclined. For the operating lever to become disengaged the pin or bolt securing the first end of the operating lever to the control ring must also fail and the first end of the operating lever must then become disengaged from a pocket within the control ring. A number of other operating levers must be removed to allow the failed operating lever to be completely disengaged. The first end of the operating levers and the pockets in the control ring are designed to prevent an operating lever jamming in the event of failure. 
   Although the present invention has been described with reference to the use of a variable vane arrangement comprising variable vanes with a fixed upstream portion and a movable downstream portion it may be used for a variable vane arrangement where the upstream portion is movable and the downstream portion is fixed or if the whole of the vane is movable. 
   Although the present invention has been described with reference to the use of a variable vane arrangement for a compressor it may be used for a variable vane arrangement for a fan or a turbine. 
   Although the present invention has been described with reference to the use of a variable vane arrangement for an intermediate-pressure compressor it may be used for a high-pressure compressor, a low-pressure compressor or a fan. 
   Although the present invention has been described with reference to a variable vane arrangement for a turbofan gas turbine engine it may be used for a turbojet gas turbine engine, a turboprop gas turbine engine, an industrial gas turbine engine or a marine gas turbine engine. 
   Although the present invention has been described with reference to the use of a variable vane arrangement for a gas turbine engine it may be used for a variable vane arrangement for any other type of turbomachine. 
   Although the present invention has been described with reference to a variable vane arrangement for an axial flow arrangement it may be used for a radial flow arrangement.