Patent Publication Number: US-11035238-B2

Title: Airfoil including adhesively bonded shroud

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This disclosure is a continuation-in-part of U.S. patent application Ser. No. 13/527,036 filed Jun. 19, 2012. 
    
    
     BACKGROUND 
     This disclosure relates to improvements in shrouded airfoils. 
     Airfoils, such as airfoils in gas turbine engines, may include a shroud at an inner diameter, outer diameter or both. The airfoils are circumferentially arranged such that inner diameter shrouds bound an inner diameter of a gas path and outer diameter shrouds bound an outer diameter of the gas path. 
     The airfoils are secured to static structures, such as cases, using fittings at the inner and outer diameters. The fittings and shrouds are integrally formed in a forging process from a suitable metallic alloy or are integrally formed by machining from a single monolithic piece of a suitable metallic alloy. 
     SUMMARY 
     An airfoil according to an example of the present disclosure includes an airfoil body that extends between a leading edge and a trailing edge, a suction side and a pressure side, and a first end and a second end. A fitting is located at one of the first end or the second end. The fitting includes a body portion, a fillet portion, and a neck portion joining the body portion and the neck portion. The neck portion includes a shelf, and here is a fastener through the airfoil body. A shroud has a complementary shape to the shelf such that the shroud nests in the shelf. 
     In a further embodiment of any of the foregoing embodiments, the shroud comprises a polymeric material. 
     In a further embodiment of any of the foregoing embodiments, the fitting is metallic and the shroud is polymeric. 
     The airfoil as recited in claim  1 , further comprising a seal member at a perimeter edge of the shroud. 
     In a further embodiment of any of the foregoing embodiments, the perimeter edge includes a groove that is complementary in shape to the seal member. 
     In a further embodiment of any of the foregoing embodiments, the groove has a cross-sectional profile of a partial circle. 
     A gas turbine engine according to an example of the present disclosure includes an airfoil as in of any of the foregoing embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various features and advantages of the present disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
         FIG. 1  shows an example gas turbine engine. 
         FIG. 2  shows a perspective view of an airfoil of the gas turbine engine of  FIG. 1 . 
         FIG. 3  shows an isolated view of a first, outer diameter fitting of the airfoil of  FIG. 2 . 
         FIG. 4  shows an isolated view of a second, inner diameter fitting of the airfoil of  FIG. 2 . 
         FIG. 5  shows an isolated view of the first, outer diameter fitting and shroud of the airfoil of  FIG. 2 . 
         FIG. 6  shows an isolated view of the second, inner diameter fitting and shroud of the airfoil of  FIG. 2 . 
         FIG. 7  shows a cross-section of a shroud adhesively bonded to a fitting. 
         FIG. 8  shows an isolated view of a shroud of the airfoil of  FIG. 2 . 
         FIG. 9  shows another example shroud having a separate and distinct shroud pieces. 
         FIG. 10  shows a sectioned, perspective view of a fitting and a shroud that includes a seal member. 
         FIG. 11  shows a perspective view of a second, inner diameter fitting, shroud and seal member. 
         FIG. 12  shows a perspective view of a first fitting, shroud and seal member. 
         FIG. 13  shows a portion of a shroud having a slot receiving a seal member. 
         FIG. 14  illustrates another example fitting and shroud. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  disclosed herein is a two-spool turbofan that generally includes a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28  that are arranged along a central axis A. Although the illustrated example is a turbofan gas turbine engine and the examples herein are described with reference to an airfoil in the engine  20 , it is to be understood that this disclosure is not limited to gas turbine engines or turbine engine airfoils. The teachings herein can be applied to other types of shrouded airfoils and turbine engines, including single- or three-spool architectures. 
     The fan section  22  of the gas turbine engine  20  includes a plurality of rotatable blades  30  and a plurality of static, structural exit guide vanes  32 . As known, the vanes  32  are circumferentially arranged around the central axis A between an outer structure  34  and an inner structure  36 , such as cases. 
       FIG. 2  shows an example of one of the vanes  32 , which is considered to be an airfoil. The vane  32  includes an airfoil body  40  that extends between a leading edge  42  and the trailing edge  44 , a suction side  46  and a pressure side  48 , and a first end  50  and a second end  52 . Relative to the central axis A, the first end  50  is an outer diameter end of the vane  32  and the second end  52  is an inner diameter end of the vane  32 . 
     The vane  32  further includes a first fitting  54   a  located at the first end  50  and a second fitting  54   b  located at the second end  52 . Each of the fittings  54   a / 54   b  is or includes a metallic material and includes one or more mounting lugs  56  for securing the vane  32  to the respective structures  34 / 36  in a known manner, such as by using fasteners. 
     The vane  32  further includes a first shroud  58   a  that is adhesively bonded to the first fitting  54   a  and a second shroud  58   b  that is adhesively bonded to the second fitting  54   b . Thus, in this example, the vane  32  is shrouded at both the first end  50  and the second end  52 . It is to be understood, however, that other types of airfoils may be shrouded at only one end, and that the examples herein are also applicable to such airfoils. As can be appreciated, use of the shrouds  58   a / 58   b  that are separate and distinct pieces from the airfoil body  40  and the respective fittings  54   a / 54   b  permits the shrouds  58   a / 58   b  to be made of different material than either the airfoil body  40  or the fittings  54   a / 54   b.    
       FIGS. 3 and 4  show isolated views, respectively, of the first fitting  54   a  and the second fitting  54   b . In this example, each of the fittings  54   a / 54   b  is a separate and distinct piece from the airfoil body  40 . In this regard, each of the fittings  54   a / 54   b  includes a corresponding pocket  60  into which the airfoil body  40  is received. The airfoil body  40  can be adhesively bonded to the respective fittings  54   a / 54   b . In other examples, the fittings  54   a / 54   b  can be integral with the airfoil body  40 . 
       FIGS. 5 and 6  show isolated views, respectively, of the shrouds  58   a / 58   b  adhesively bonded to the fittings  54   a / 54   b .  FIG. 7  shows a cross-section through an interface between the second fitting  54   b  and the second shroud  58   b  adhesively bonded to the second fitting  54   b . It is to be understood that the interface between the first fitting  54   a  and the first shroud  58   a  is similar to the interface shown in  FIG. 7 . As shown, the second shroud  58   a  is adhesively bonded to the second fitting  54   b  by an adhesive  70 . In one example, the adhesive  70  is an epoxy adhesive. In other examples, other types of adhesives can be used that are suitable for the expected operating temperature of the airfoil. 
     The second fitting  54   b  includes a flange F to which the second shroud  58   a  is adhesively bonded. In this example, the flange F includes a rabbet  54   b ′. The rabbet  54   b ′, or ledge, supports the adhesive  70  for bonding the second shroud  58   b  thereto. Thus, the second shroud  58   b  is adhesively bonded to the rabbet  54   b ′. A method of assembling the vane  32  therefore includes providing the vane  32  as described, and adhesively bonding the shrouds  58   a / 58   b  to the fittings  54   a / 54   b.    
       FIG. 8  shows an isolated view of the first shroud  58   a . In this example, the first shroud  58   a  includes a shroud body  72  that extends between first and second broadsides  74   a / 74   b , perimeter edges  76 , which are axially and circumferentially facing surfaces, and interior edges  78  that define an elongated, arcuate opening  80  extending between the first and second broadsides  74   a / 74   b . The opening  80  is generally elongated in a direction parallel to the central axis A of the gas turbine engine  20 . The opening  80  also has the arcuate shape, which corresponds to the arcuate shape of the cross-section of the airfoil body  40 . 
     The first shroud  58  also optionally includes a plurality of additional openings  82  that correspond to the mounting lugs  56  on the first fitting  54   a . Depending on the geometry of the first shroud  58   a  and location of the mounting lugs  56 , other examples may exclude the additional openings  82 . 
     It is to be understood that the second shroud  58   b  has similar features as the first shroud  58   a  with regard to including a shroud body, first and second broadsides, perimeter edges and interior edges that define an elongated, arcuate opening. As can be appreciated, the contouring and size of the second shroud  58   b  may differ and the elongated, arcuate opening of the second shroud  58   b  may have a different geometry that corresponds to the cross-section of the airfoil body  40  at the inner diameter. Also, the additional optional openings may be positioned differently to align with the mounting lugs  56  on the second fitting  54   b.    
     In this example, the first shroud  58   a  is a monolithic piece. That is, the first shroud  58   a  is a single piece of material that is free of joints or seams. Thus, in the assembly of the vane  32 , the airfoil body  40  extends through the elongated, arcuate opening  80  and into the corresponding first fitting  54   a  (or second fitting  54   b  for the elongated arcuate opening of the second shroud  58   b ). 
       FIG. 9  shows a modified example of a first shroud  158   a . In this disclosure, like reference numerals designate like elements where appropriate and reference numerals with the addition of one-hundred or multiples thereof designate modified elements that are understood to incorporate the same features and benefits of the corresponding elements. In this example, the first shroud  158   a  includes a plurality of separate and distinct pieces  190   a / 190   b . Each of the pieces  190   a / 190   b  includes a portion of the interior edges  78  such that, when assembled together, the pieces  190   a / 190   b  define the complete perimeter of the elongated, arcuate opening  80 , which circumscribes the first fitting  54   a  similar to as shown in  FIG. 6 . 
     For example, the pieces  190   a / 190   b  are initially separate and are then assembled around the first fitting  54   a  and adhesively bonded thereto to form the complete first shroud  158   a . Thus, the shroud  158   a  can be fitted onto an existing vane as a retrofit, for example. The use of the separate pieces  190   a / 190   b  also facilitates removal of the shroud  158   a  for replacement with a new, similar shroud, should the shroud  158   a  require replacement. 
       FIG. 10  shows a perspective, sectioned view through a portion of the second fitting  54   b . In this example, the second shroud  58   b  further includes a seal member  90  attached at one of the perimeter edges  76  of the second shroud  58   b . The second fitting  54   b , the second shroud  58   b  and the seal member  90  are shown in full view in  FIG. 11 . Similarly, as shown in  FIG. 12 , the first shroud  58   a  can likewise include a seal member  90 . When the vanes  32  are circumferentially arranged in the gas turbine engine  20 , the seal members  90  bear against a neighboring shroud  58   a / 58   b  to provide a gas path seal. 
     In the illustrated example, the seal member  90  is adhesively bonded to the second shroud  58   b  using an adhesive  90   a . Similar to the adhesive  70 , the adhesive  90   a  can be an epoxy adhesive. Alternatively, the adhesive  90   a  can be another type of adhesive that is suitable for the operating temperature of the airfoil. In another alternative, the seal member  90  can be integrally formed with the second shroud  58   b , such as in a co-molding or over-molding operation. 
       FIG. 13  shows a portion of a modified first shroud  258   a . In this example, the first shroud  258   a  includes a slot S extending into one of the perimeter edges  76 . The seal member  90  includes a flange  90 ′ that is received into the slot S to secure the seal member  90  and the first shroud  258   a  together. The slot S can be sized in correspondence with the size of the flange  90 ′ such that there is an interference fit or snap fit between the first shroud  258   a  and the seal member  90 . Alternatively, an adhesive can be used to secure the seal member  90  within the slot S. Similarly, the second shroud  58   b  can also include a slot for attaching the seal member  90 . 
     Using the shrouds disclosed herein that are separate and distinct pieces from the airfoil body  40  and the respective fittings  54   a / 54   b  permits the shrouds to be made of different materials than either the airfoil body  40  or the fittings  54   a / 54   b . In one example, the shrouds are, or include, a polymeric material. In a further example, the polymeric material is a reinforced polymeric material that includes glass fibers, carbon fibers, or other reinforcement additives. In comparison to airfoils that are made entirely of metal alloys, the airfoils disclosed herein provide a weight reduction because of the use of the polymeric material. Furthermore, metallic shrouds that are integrally formed with fittings require significant raw material and machining to attain the final geometric configuration. However, by forming the shrouds disclosed herein from the polymeric material, the shrouds can be formed to the required geometry and tolerances using known polymer forming processes, such as injection molding. 
       FIG. 14  illustrates another example fitting  154   b  and shroud  158   b . In this example, the fitting  154   b  includes a body portion  92  that receives a fastener  93  for securing the airfoil body  40  and the fitting  154   b  together. The fitting  154   b  further includes a neck portion  94  connected to the body portion  92 , and a fillet portion  95  connected to the neck portion  94 . The neck portion  94  includes a shelf  94   a  that extends at the perimeter of the fitting  156   b . In one example, the shelf  94   a  is a continuous ring. The upper surface and corner of the shelf  94   a  is complementary to the bottom inside surface and edge of the shroud  158   b  such that the shroud  158   b  nests into the shelf  94   a . In one example, the shroud  158   b  is also a continuous ring. An adhesive or mechanical fastener may be used to secure the shelf  94   a  and shroud  158   b  together. The fillet portion  95  of the fitting  154   b  may form a smooth, flush surface with the shroud  158   b.    
     At its perimeter on one side, the shroud  158   b  includes a groove  97 . The groove  97  has a curved cross-sectional profile, such as a partial- or semi-circle. A seal member  190  has a complementary profile to the groove  97  and is received into the groove  97 . An adhesive may be used to secure the seal member  190  in the groove  97 . The complementary shapes of the groove  97  and the seal member  190  facilitate proper seating of the seal element  190  in the groove  97 . 
     Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments. 
     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.