Abstract:
An example method of assembling a turbomachine airfoil array includes, among other things, securing a partial airfoil array within a fixture, the partial airfoil array having at least one existing airfoil extending radially between an inner and an outer fairing and an open area where at least one existing airfoil has been removed. The method includes mounting a positioning saddle relative to a base of the fixture, the positioning saddle aligned with the open area, holding a replacement airfoil using the positioning saddle, applying a curable material at an interface between the replacement airfoil and the inner and outer fairing, and curing the curable material while maintaining a relative position between the replacement airfoil and the inner and outer fairing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 13/626,929, which was filed on 26 Sep. 2012 and is incorporated herein by reference. 
    
    
     BACKGROUND 
     This disclosure relates generally to a method of airfoil array assembly and, more particularly, to a fixture that locates selected airfoils during assembly. 
     Turbomachines, such as a gas turbine engines, typically include a fan section, and a core engine section including 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. The compressor section typically includes low and high-pressure compressors, and the turbine section includes low and high-pressure turbines. 
     The high-pressure turbine drives the high-pressure compressor through an outer shaft to form a high spool, and the low pressure turbine drives the low-pressure compressor through an inner shaft to form a low spool. A direct drive gas turbine engine includes a fan section driven by the low spool such that the low-pressure compressor, low-pressure turbine, and fan section rotate at a common speed in a common direction. A speed reduction device such as an epicyclical gear assembly may be utilized to drive the fan section such that the fan section may rotate at a speed different than the turbine section so as to increase the overall propulsive efficiency of the engine. 
     Some front architectures support the stator vanes relative to inner and outer fairings using rubber potting. Because there are no fixed features or fasteners used to secure vanes within the fairings, assembly can be difficult and time consuming. Replacing potted vanes in an existing assembly during repair, for example, is also difficult and complex. Alignment features in the existing assembly may make loading a partial airfoil array difficult. 
     SUMMARY 
     A method of assembling a turbomachine airfoil array according to an exemplary aspect of the present disclosure includes, among other things, securing a partial airfoil array within a fixture, the partial airfoil array having at least one existing airfoil extending radially between an inner and an outer fairing and an open area where at least one existing airfoil has been removed. The method includes mounting a positioning saddle relative to a base of the fixture, the positioning saddle aligned with the open area, holding a replacement airfoil using the positioning saddle, applying a curable material at an interface between the replacement airfoil and the inner and outer fairing, and curing the curable material while maintaining a relative position between the replacement airfoil and the inner and outer fairing. 
     In a further non-limiting embodiment of the foregoing method of assembling, the replacement airfoil may be a stator vane. 
     In a further non-limiting embodiment of either of the foregoing methods of assembling, the method may include positioning the replacement airfoil vanes by defining a first plane with at least two contact points on the positioning saddle, defining a second plane with at least two contact points on the positioning saddle, and defining at least a portion of a third plane with at least one contact point on the positioning saddle. 
     In a further non-limiting embodiment of any of the foregoing methods of assembling, the positioning saddle may include a first portion and a separate, second portion, the first portion having the contact points defining the first and second planes, and the second portion having the at least one contact point defining the third plane. 
     In a further non-limiting embodiment of any of the foregoing methods of assembling, the positioning saddle may be selected from a group of positioning saddles, at least some of the positioning saddles within the group having contact points defining different first planes and different second planes. 
     In a further non-limiting embodiment of any of the foregoing methods of assembling, the fixture does not include positioning saddles associated with the at least one existing airfoil. 
     In a further non-limiting embodiment of any of the foregoing methods of assembling, the at least one existing airfoil may be held within the fixture during curing of the curable material. 
     In a further non-limiting embodiment of any of the foregoing methods of assembling, the positioning saddle may be configured to be selectively positioned at one of a plurality of circumferential positions. 
     In a further non-limiting embodiment of any of the foregoing methods of assembling, the fixture may provide unobstructed areas that accommodate the existing airfoils when the partial airfoil array is secured within the fixture, the unobstructed area lacking contact points defining planes for aligning airfoil vanes. 
     In a further non-limiting embodiment of any of the foregoing methods of assembling, the mounting may be before the securing. 
     A fixture for assembling a turbomachine airfoil array according to an exemplary aspect of the present disclosure includes, among other things, a base and a positioning saddle that is selectively mounted to the base, the positioning saddle configured to hold a replacement airfoil to maintain a relative position between the replacement airfoil and an inner and outer fairing when a curable material at an interface between the replacement airfoil and the inner and outer fairing is curing. 
     In a further non-limiting embodiment of the foregoing fixture, the replacement airfoil may be a stator vane. 
     In a further non-limiting embodiment of either of the foregoing fixtures, the positioning saddle holds the replacement airfoil by defining a first plane with at least two contact points, defining a second plane with at least two contact points, and defining at least a portion of a third plane with at least one contact point. 
     In a further non-limiting embodiment of any of the foregoing fixtures, the positioning saddle may include a first portion and a separate, second portion, the first portion having the contact points defining the first and second planes, and the second portion having the at least one contact point defining the third plane. 
     In a further non-limiting embodiment of any of the foregoing fixtures, the positioning saddle may be selected from a group of positioning saddles, at least some of the positioning saddles within the group having contact points defining different first planes and second planes. 
     In a further non-limiting embodiment of any of the foregoing fixtures, the fixture may provide unobstructed areas that accommodate the existing airfoils when the partial airfoil array is secured within the fixture, the unobstructed area lacking contact points defining planes for aligning airfoil vanes. 
     An airfoil positioner according to an exemplary aspect of the present disclosure includes, among other things, a positioning saddle that is selectively mountable to a base at one of a plurality of circumferential mounting locations. The positioning saddle configured to hold a replacement airfoil to maintain a relative position between the replacement airfoil and an inner and outer fairing when a curable material at an interface between the replacement airfoil and the inner and outer fairing is curing. The positioning saddle defining a first plane with at least two contact points, defining a second plane with at least two contact points, and defining at least a portion of a third plane with at least one contact point. 
     An airfoil positioner according to an exemplary aspect of the present disclosure includes, among other things, a first portion and a separate, second portion, the first portion having the contact points defining the first and second planes, and the second portion having the at least one contact point defining the third plane. 
     A method of assembling a turbomachine airfoil array according to yet another exemplary aspect of the present disclosure includes, among other things, securing a partial airfoil array within a fixture. The partial airfoil array has at least one existing airfoil extending radially between an inner fairing and an outer fairing, and an open area where at least one existing airfoil has been removed. The method further includes holding a replacement airfoil by defining a first plane with at least two contact points, applying a curable material at an interface between the replacement airfoil and the inner fairing and the outer fairing, and curing the curable material while maintaining a relative position between the replacement airfoil and the inner fairing and the outer fairing. 
     In a further non-limiting embodiment of the foregoing method of assembling, the holding comprises holding the replacement airfoil using a positioning saddle. 
     In a further non-limiting embodiment of any of the foregoing methods assembling, the positioning saddle includes a first portion and a separate, second portion, the first portion having the contact points defining the first and second planes, and the second portion having the at least one contact point defining the third plane. 
     In a further non-limiting embodiment of any of the foregoing methods assembling, the positioning saddle is selected from a group of positioning saddles, at least some of the positioning saddles within the group having contact points defining different first planes and different second planes. 
     In a further non-limiting embodiment of any of the foregoing methods assembling, the replacement airfoil is a stator vane. 
     In a further non-limiting embodiment of any of the foregoing methods assembling, the at least one existing airfoil is held within the fixture during curing of the curable material. 
     In a further non-limiting embodiment of any of the foregoing methods assembling, the positioning saddle is configured to be selectively positioned at one of a plurality of circumferential positions. 
     In a further non-limiting embodiment of any of the foregoing methods assembling, the fixture provides unobstructed areas that accommodate the existing airfoils when the partial airfoil array is secured within the fixture, the unobstructed area lacking contact points defining planes for aligning airfoil vanes. 
     In a further non-limiting embodiment of any of the foregoing methods assembling, the mounting is before the securing. 
     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 
         FIG. 1  is a schematic view of an example gas turbine engine. 
         FIG. 2  is a perspective view of an example stator vane assembly. 
         FIG. 3  is a partial schematic view of vanes of the stator vane assembly of  FIG. 2 . 
         FIG. 4  is a perspective view of a top portion of the stator vane assembly of  FIG. 2 . 
         FIG. 5  is a bottom view of the stator vane assembly of  FIG. 2 . 
         FIG. 6  is a perspective view of a portion of the stator vane assembly of  FIG. 2  within an example assembly fixture. 
         FIG. 7  is a perspective view of the assembly fixture of  FIG. 6  with the stator vane assembly removed. 
         FIG. 8  is another perspective view of the assembly fixture of  FIG. 6  with the stator vane assembly removed. 
         FIG. 9  is a perspective view of the portion of the example stator vane assembly of  FIG. 6  within another example assembly fixture. 
         FIG. 10  is a perspective view of the assembly fixture of  FIG. 9  with the stator vane assembly removed. 
         FIG. 11  is another perspective view of the assembly fixture of  FIG. 9  with the stator vane assembly removed. 
     
    
    
     DETAILED DESCRIPTION 
       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 . 
     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. 
     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 . 
     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. 
     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 . 
     The high-speed spool  32  includes a shaft  50  that interconnects a high-pressure compressor  52  and high-pressure turbine  54 . 
     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 . 
     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 . 
     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). 
     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). 
     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. 
     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. 
     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). 
     Low Corrected Fan Tip Speed is the actual fan tip speed 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). 
     Referring to the  FIG. 2 , the example low-pressure compressor  44  includes at least one a stator vane assembly  60  having an outer fairing  62 , an inner fairing  64 , and a plurality of stator vanes  66  extending radially therebetween. The stator vane assembly  60  is an example airfoil array of the engine  20 . Other arrays may include types of airfoils other than stator vanes, such as blades. 
     Referring to  FIGS. 3, 4, and 5  with continued reference to  FIG. 2 , the stator vanes  66  are supported within openings  68  or slots defined within each of the inner and outer fairings  62  and  64 . Each of the stator vanes  66  includes an inner end  70 , an outer end  72 , a leading edge  74 , and a trailing edge  76 . Each of the stator vanes  66  are supported within the openings  68  by a sealant  78 . The example sealant  78  is a curable material that remains flexible once cured. The stator vanes  66  are mounted within the openings  68  by way of the curable sealant  78 . 
     The sealant  78  provides a bonded joint between the inner and outer fairings  62  and  64 . During assembly the sealant  78  is injected into the openings  68  and within gaps between each of the stator vanes  66  and the corresponding opening  68  to vibrationally isolate the outer and inner fairings  62  and  64  from the stator vanes  66 . 
     It is the sealant  78 , however, that provides the joint that maintains each of the vanes  66  in a desired position relative to the other stator vanes  66  and each of the outer and inner fairings  62  and  64 . Initial assembly of the stator vane assembly  60  requires specific positioning of each of the stator vanes  66  within corresponding openings  68 . Positioning within the openings  68  is provided such that the stator vanes  66  themselves do not engage the outer and inner fairings  62  and  64 . 
     An initial assembly fixture typically includes various locators used to define and maintain a relative position between the plurality of stator vanes  66  and the outer and inner fairings  62  and  64  while the sealant  78  is applied and cured to form the completed stator vane assembly  60 . 
     Since all the stator vanes  66  are sequentially positioned relative to the outer and inner fairings  62  and  64  during initial assembly, there is little drawback to interference between a fixture and stator vanes  66  during initial assembly. 
     Once assembled, the stator vane assembly  60  may be installed and used within the engine  20 . Over time, some of the stator vanes  66  may become damaged and require replacement. It is difficult to reload the stator vane assembly  60  requiring repair into the same fixture used during initial assembly because, for example, the various locators may contact portions of the stator vane assembly  60  during loading. 
     Referring to  FIGS. 6-8 , an example assembly fixture  84  used during a replacement procedure, for example, includes a base  86  that supports the outer fairing  62  and the inner fairing  64 . The example fixture  84  includes positioning saddles  88  that are used to directly hold selected ones the plurality of stator vanes  66  in a desired position for assembly including the application and curing of the sealant  78  ( FIGS. 4 and 5 ). The positioning saddles  88  are only used in association with the stator vanes  66  that are being attached to the outer and inner fairing  62  and  64 . The positioning saddles  88  are absent from the areas of the fixture  84  that will accommodate other stator vanes  66  that are already attached to the outer and inner fairings  62  and  64 . 
     As previously mentioned, some of the stator vanes  66  may become damaged or worn during use within the engine  20 . To repair such a stator vane assembly  60 , the stator vane assembly  60  is first removed from the engine  20 . The damaged stator vanes  66  are then removed from the outer and inner fairings  62  and  64 , which creates an open area  89  within the stator vane assembly  60 . Existing vanes, those vanes that do not require replacement, remain part of the stator vane assembly  60 . The stator vane assembly  60  with the removed vanes may be considered to provide a partial airfoil array. 
     The stator vane assembly  60  is then loaded into the fixture  84 , and the open area  89  aligned with the positioning saddles  88 . Each of the positioning saddles  88  then receives and holds one replacement stator vane  66   a  during application and curing of the sealant  78 . The positioning saddles  88  are selectively mountable to various circumferential areas of the fixture  84 . The positioning saddles  88 , in this example, are mounted to the circumferential area corresponding to the open area  89  in the partially disassembled stator vane assembly  10 . 
     In this example, no positioning saddles  88  are used other than those that will receive a replacement stator vane  66   a . That is, positioning saddle are not mounted to the base  86  in areas of the fixture  84  that accommodate the existing stator vanes  66 . The fixture  84  thus provides unobstructed areas that accommodate the existing stator vanes  66 . The unobstructed areas lack contact points defining planes for aligning vanes. The fixture  84  can thus receive the stator vane assembly  60  without significant interference between the stator vanes  66  remaining in the stator vane assembly  60  and the portions of the fixture  84 . 
     The example positioning saddles  88  provide the specific datum planes and points required to properly align each of the associated replacement stator vanes  66   a  relative to adjacent vanes and the outer and inner and fairings  62  and  64 . In operation, the example fixture  84  having the positioning saddles  88  is utilized to define the relative position between the outer and inner fairings  62  and  64  prior to application of the sealant  78 . 
     The sealant  78  is applied to secure the replacement stator vane  66   a  within the outer and inner fairings  62  and  64  and also to eliminate vibratory transmission between parts. 
     Although each positioning saddle  88  holds a single replacement stator vane  66   a  in this example, other examples may include positioning saddles configured to hold more than one replacement stator vane  66   a.    
     In this example, the positioning saddles  88  include locator pins  92  that are received within respective apertures  94  of the base  86  to mount and locate the positioning saddle  88  relative to the base  86 . 
     The example positioning saddles  88  have a radially inner hump  96  and a radially outer hump  98  that locate the replacement stator vane  66   a  during application and curing of the sealant. The positioning saddles  88  also include pins  102  that locate the stator vane  66   a  with the outer and inner fairings  62  and  64  in other directions. More specifically, the example positioning saddles  88  define a first plane with at least two contact points on the humps  96  and  98 , define a second plane with at least two contact points on two of the pins  102 , and define at least a portion of a third plane with at least one contact point on another of the pins  102 . 
     In this example, the stator vane assembly  60  includes stator vanes  66  having three distinct orientations. These stator vanes  66  are arranged in groups  104   a ,  104   b , and  104   c . The fixture  84  thus includes three distinct types of positioning saddles  88  having humps  96  and  98  and pins  102  adjusted to hold the replacement stator vanes  66   a  in the desired one of the three orientations. Other examples may include more stator vane orientations and thus more positioning saddle variations. 
     When the stator vane assembly  60  is loaded within the fixture  84 , the base  86  of the example fixture  84  provides an attachment location for clamps  106  that hold the outer fairing  62 . The inner fairing  64  is supported on a radially inner portion of the base  86  and held in place by inner clamps  108 . 
     Referring to  FIGS. 9-11 , another example fixture  84   a  that may be used to hold the stator vane assembly  60  during, for example, a repair or replacement procedure, includes positioning saddles  88   a  having a first portion  110  and a second portion  114 . The first portion includes a radially inner hump  96   a  and a radially outer hump  98   a  that locate the replacement stator vane  66   a  during replacement. The first portion  110  also includes three locator pins  102   a  used to locate the replacement stator vane in some directions. The second portion  114  includes a locator pin  116  that locates the replacement stator vane  66   a  in another direction, which is a radial direction in this example. 
     During a replacement, the replacement stator vane  66   a  is moved radially inward through the opening  68  in the outer fairing  62 , the opening  68  in the inner fairing  64 , until the replacement stator vane  66   a  contacts the locator pin  116 . 
     The fixture  84   a  is utilized for vanes that are loaded, during a replacement procedure, first through the radially outer fairing  62  and then moved radially outward. The fixture assembly  84  is suitable for stator vane assemblies  60  where the vanes are located, in a replacement procedure, first through the opening  68  in the inner fairing  64  and moved radially outward. 
     Although the positioning saddles  88  and  88   a  are described as positioning stator vanes, the positioning saddles  88  and  88   a  are airfoil positioners that may be used to position other types of airfoils, such as blades. 
     Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the scope and content of this disclosure.