Abstract:
Aspects of the disclosure are directed to milling a nose of a first shield of a blade to leave at least one strip of the first shield coupled to a blade body, subsequent to the milling, applying a cryogenic technique to the blade to weaken a bond between the first shield and the blade body, and subsequent to the applying of the cryogenic technique, removing the at least one strip of the first shield from the blade body.

Description:
BACKGROUND 
       [0001]    Gas turbine engines, such as those which power aircraft and industrial equipment, employ a compressor to compress air that is drawn into the engine via a fan and a turbine to capture energy associated with the combustion of a fuel-air mixture. Various components of the engine may be subject to wear over the operational lifetime of the engine. For example, in an aerospace application the engine may ingest stones, hail, animals (e.g., birds), etc., that may degrade the structural integrity of a component of the engine. The degradation may render the component inoperable and/or may impact the performance/efficiency of the engine. 
         [0002]    One of the components of an engine is a fan blade. The fan blade is manufactured to include a sheath/shield at an axial, leading edge of the fan blade. The shield is coupled to a fan blade body/substrate via an epoxy adhesive. The shield helps protect the blade against erosion. The shield also provides strength/resistance to the blade in relation to potential impact with objects, such as the ingested objects described above. However, the shield&#39;s presence at the leading edge of the fan blade also makes the shield particularly susceptible to wear. If the wear is significant enough (e.g., if the wear is in an amount that is greater than a threshold), the shield may need to be removed and replaced. 
         [0003]    Conventional techniques for removing a shield from the blade body include application of an instrument (e.g., a putty knife) to remove the adhesive that couples the shield to the blade body. While effective, the use of the instrument may have a tendency to compromise the integrity of the blade body. Another technique that is used in the removal of the shield is to submerge the blade in a chemical solution bath. The chemical solution compromises/attacks the adhesive, thereby separating the shield from the blade body. However, the chemical solution is only effective where the chemical interfaces with the adhesive; experience suggests that a blade may need to be submerged in the bath on the order of twenty hours before the shield is separable from the blade body. Accordingly, what is needed is a more efficient and effective technique for removing a shield from a blade body. 
       BRIEF SUMMARY 
       [0004]    The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosure. The summary is not an extensive overview of the disclosure. It is neither intended to identify key or critical elements of the disclosure nor to delineate the scope of the disclosure. The following summary merely presents some concepts of the disclosure in a simplified form as a prelude to the description below. 
         [0005]    Aspects of the disclosure are directed to a method comprising: milling a nose of a first shield of a blade to leave at least one strip of the first shield coupled to a blade body, subsequent to the milling, applying a cryogenic technique to the blade to weaken a bond between the first shield and the blade body, and subsequent to the applying of the cryogenic technique, removing the at least one strip of the first shield from the blade body. In some embodiments, the applying of the cryogenic technique includes applying dry ice to the at least one strip. In some embodiments, the applying of the cryogenic technique compromises an adhesive disposed between the first shield and the blade body. In some embodiments, the at least one strip includes at least two strips. In some embodiments, the removing of the at least one strip from the blade body includes prying or cutting the at least one strip using an instrument. In some embodiments, the instrument includes a knife. In some embodiments, the first shield is coupled to the blade body via an adhesive, and the method further comprises: removing residual adhesive from the blade body subsequent to the removal of the at least one strip from the blade body. In some embodiments, the method further comprises preparing the blade body to receive a second shield subsequent to the removal of the at least one strip from the blade body. In some embodiments, the preparing includes applying a solvent to the blade body. In some embodiments, the preparing includes applying a primer to the blade body and curing the primer. In some embodiments, the preparing includes applying an adhesive to the blade body. In some embodiments, the method further comprises coupling a second shield to the blade body subsequent to the removal of the at least one strip from the blade body. In some embodiments, the second shield corresponds to the first shield after the first shield has been subjected to conditioning or repair. In some embodiments, the second shield is different from the first shield. In some embodiments, the method further comprises applying a heat blanket to the second shield and bonding the second shield to the blade body subsequent to the applying of the heat blanket. In some embodiments, the method further comprises applying a vacuum bag to the second shield and bonding the second shield to the blade body subsequent to the applying of the vacuum bag. In some embodiments, the method further comprises installing the blade as part of an engine subsequent to the coupling of the second shield to the blade body. In some embodiments, the blade is installed as part of a fan section of the engine. In some embodiments, the blade is installed as part of a compressor section of the engine. In some embodiments, at least one of the blade body or the shield includes at least one of a composite material, aluminum, or titanium. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The present disclosure is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements. The drawings are not necessarily drawn to scale unless specifically indicated otherwise. 
           [0007]      FIG. 1  is a side cutaway illustration of a geared turbine engine. 
           [0008]      FIG. 2A  illustrates a cross-sectional view of a system incorporating a blade in accordance with aspects of this disclosure. 
           [0009]      FIG. 2B  illustrates the system of  FIG. 2A  after a portion of a shield has been removed from the blade. 
           [0010]      FIG. 2C  illustrates the system of  FIG. 2B  after material strips of the shield have been removed from the blade. 
           [0011]      FIG. 3  illustrates a flow chart of a method used to remove and replace a shield of a blade in accordance with aspects of this disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    It is noted that various connections are set forth between elements in the following description and in the drawings (the contents of which are included in this disclosure by way of reference). It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. 
         [0013]    In accordance with aspects of the disclosure, apparatuses, systems, and methods are directed to a blade of an engine, such as for example a fan blade. The blade may include a shield located on a leading edge of a substrate/body of the blade, where the leading edge may be defined relative to a forward, axial reference direction of the engine. The shield may be removed from the body of the blade using one or more techniques. For example, a milling technique and a cryogenic technique may be used in some embodiments to remove the shield from the body. 
         [0014]    Aspects of the disclosure may be applied in connection with a gas turbine engine.  FIG. 1  is a side cutaway illustration of a geared turbine engine  10 . This turbine engine  10  extends along an axial centerline  12  between an upstream airflow inlet  14  and a downstream airflow exhaust  16 . The turbine engine  10  includes a fan section  18 , a compressor section  19 , a combustor section  20  and a turbine section  21 . The compressor section  19  includes a low pressure compressor (LPC) section  19 A and a high pressure compressor (HPC) section  19 B. The turbine section  21  includes a high pressure turbine (HPT) section  21 A and a low pressure turbine (LPT) section  21 B. 
         [0015]    The engine sections  18 - 21  are arranged sequentially along the centerline  12  within an engine housing  22 . Each of the engine sections  18 - 19 B,  21 A and  21 B includes a respective rotor  24 - 28 . Each of these rotors  24 - 28  includes a plurality of rotor blades arranged circumferentially around and connected to one or more respective rotor disks. The rotor blades, for example, may be formed integral with or mechanically fastened, welded, brazed, adhered and/or otherwise attached to the respective rotor disk(s). 
         [0016]    The fan rotor  24  is connected to a gear train  30 , for example, through a fan shaft  32 . The gear train  30  and the LPC rotor  25  are connected to and driven by the LPT rotor  28  through a low speed shaft  33 . The HPC rotor  26  is connected to and driven by the HPT rotor  27  through a high speed shaft  34 . The shafts  32 - 34  are rotatably supported by a plurality of bearings  36 ; e.g., rolling element and/or thrust bearings. Each of these bearings  36  is connected to the engine housing  22  by at least one stationary structure such as, for example, an annular support strut. 
         [0017]    During operation, air enters the turbine engine  10  through the airflow inlet  14 , and is directed through the fan section  18  and into a core gas path  38  and a bypass gas path  40 . The air within the core gas path  38  may be referred to as “core air”. The air within the bypass gas path  40  may be referred to as “bypass air”. The core air is directed through the engine sections  19 - 21 , and exits the turbine engine  10  through the airflow exhaust  16  to provide forward engine thrust. Within the combustor section  20 , fuel is injected into a combustion chamber  42  and mixed with compressed core air. This fuel-core air mixture is ignited to power the turbine engine  10 . The bypass air is directed through the bypass gas path  40  and out of the turbine engine  10  through a bypass nozzle  44  to provide additional forward engine thrust. This additional forward engine thrust may account for a majority (e.g., more than 70 percent) of total engine thrust. Alternatively, at least some of the bypass air may be directed out of the turbine engine  10  through a thrust reverser to provide reverse engine thrust. 
         [0018]      FIG. 1  represents one possible configuration for an engine  10 . Aspects of the disclosure may be applied in connection with other environments, including additional configurations for gas turbine engines. Aspects of the disclosure may be applied in connection with non-geared engines. 
         [0019]    Referring to  FIG. 2A , a system  200  is shown. The system  200  may be used in the conjunction with a replacement of a shield associated with a blade, where the manufacture and use of the shield would be known to one of skill in the art as described above. 
         [0020]    The system  200  is shown as including a blade body  204 . The blade body  204  may be coupled to a shield  208 . The shield  208  may be located at a leading edge of the blade body  204 , where the leading edge may be specified with respect to a forward, axial reference direction associated with an engine (e.g., engine  10  of  FIG. 1 ). The shield  208  may be coupled to the blade body via an adhesive  212 , such as for example an epoxy adhesive. In this respect, the adhesive  212  may be disposed between the blade body  204  and the shield  208 . 
         [0021]    The system  200  may include a cover  222 . The cover  222  may be coupled to (e.g., bonded on) the blade body  204 . The cover  222  may provide protection with respect to one or more cavities that may be incorporated in the blade (e.g., the blade body  204 ); for example, the cover  222  may prevent any unwanted material or debris from entering the cavities. 
         [0022]    The system  200  may include a release film  226 . The release film  226 , illustratively shown in  FIG. 2A  as being disposed between the shield  208  and a first, inner layer breather cloth  234 , may serve as a separator to keep, e.g., the shield  208  and the breather cloth  234  from sticking together. The release film  226  may be sourced from one or more providers, such as for example Northern Composites, Inc. of Hampton, N.H. 
         [0023]    The system  200  may include a breather cloth  234 . The breather cloth  234  may be implemented as one or more layers. For example, a first layer of the breather cloth  234  may be disposed between: (1) the shield  208 /release film  226  and (2) a heat blanket  238 . A second, outer layer of the breather cloth  234  may be disposed between (1) the heat blanket  238  and (2) a vacuum bag  244 . The particular ordering of the layers is illustrative; other arrangements may be used. Furthermore, while two layers of breather cloth  234  are shown in  FIG. 2A , any number of layers of breather cloth  234  may be used in some embodiments. As one skilled in the art would appreciate, a breather cloth  234  is typically a lightweight blanket used in vacuum bag  244  bonding process. The breather cloth  234  may be sourced from one or more providers, such as for example Northern Composites, Inc. of Hampton, N.H. The role of the heat blanket  238  and the vacuum bag  244  in the context of the system  200  is described below in relation to  FIG. 3 . 
         [0024]    Referring to  FIG. 3 , a flow chart of a method  300  is shown. The method  300  may be used to remove a shield from a blade body of a blade. The method  300  is described below in relation to  FIGS. 2A-2C  for illustrative convenience; one skilled in the art would appreciate that the method  300  may be adapted to accommodate other types of systems or components. 
         [0025]    In block  306 , the blade may be positioned in a tooling fixture. The fixture may constrain the blade relative to a mill. Stated somewhat differently, the fixture may ensure that the blade is oriented relative to an orientation of the mill. 
         [0026]    In block  312 , the mill may be programmed to make a cut at an interface (e.g., interface  252 ) between the first shield  208  and the blade body  204  along the length of the first shield  208 . After the cut/mill is made, the forward portion/nose  256  of the first shield  208  may fall off, leaving strips of material  208   a  and  208   b  of the first shield  208  (see  FIG. 2B ). Cutting the nose  256  off facilitates/eases application of a cryogenic technique as described below by converting a three-dimensional bond-line shape to a two-dimensional shape. 
         [0027]    In block  318 , a cryogenic technique may be applied to the blade. For example, dry ice may be applied to the strips  208   a  and  208   b.  The dry ice may, in effect, penetrate the strips  208   a  and  208   b  and compromise the adhesive  212  by imposing stress/strain on an associated bond-line. 
         [0028]    Application of the cryogenic technique may be effective within a couple of minutes (e.g., ten minutes), after which the first shield  208  may be easily removed from the blade body  204 . For example, as part of block  324  an instrument (e.g., a hand tool, such as for example a putty knife) may be applied to pry/cut any remaining portions of the first shield  208  (e.g., the strips  208   a  and  208   b ) away from the blade body  204  (see  FIG. 2C , where the strips  208   a  and  208   b  are removed relative to  FIG. 2B ). One skilled in the art would appreciate that the instrument may include a power tool or an automated device. 
         [0029]    In block  330 , any residual adhesive  212  that may remain on the blade body  204  may be removed. For example, as part of block  330  sandblasting (e.g., aluminum oxide sandblasting) or sandpaper (e.g., aluminum oxide sandpaper) may be applied to the blade body  204 . 
         [0030]    As part of block  336 , one or more techniques may be applied to the blade body  204  in order to prepare the blade body  204  for bonding with a second shield  208 . For example, as part of block  336  one or more solvents may be applied to the blade body  204 . A primer may be applied to the blade body  204 ; the primer may be cured. Adhesive  212  may be (re)applied to the blade body  204 . 
         [0031]    In block  342 , the second shield  208  may be coupled to the blade body  204 . The second shield  208  may correspond to the first shield  208  that was removed as part of block  324  described above, potentially after the first shield  208  has been subjected to conditioning or repair. The second shield  208  may correspond to a new instance of a shield, e.g., the second shield  208  may be different from the first shield  208 . 
         [0032]    In block  348 , the heat blanket  238  and/or a vacuum bag  244  may be coupled to, e.g., the second shield  208 . Heat and pressure may be applied to the second shield  208  in relation to a bonding of the second shield  208  to the blade body  204 . The heat blanket  238  and vacuum bag  244  may help to ensure that a service characteristic/parameter of the adhesive  212  is not exceeded/compromised during the bonding procedure. 
         [0033]    In block  354 , the blade may be removed from the fixture and installed as part of an engine. For example, as part of block  354  the blade may be installed as part of a fan section or a compressor section of the engine. 
         [0034]    In some embodiments, a blade may be made from, or include, one or more materials. For example, a blade may be manufactured from a composite material, aluminum, titanium, etc. 
         [0035]    Technical effects and benefits of this disclosure include an ability to reprocess/refurbish a cast/forged blade by removing a first heat shield from a blade body and coupling a second heat shield (which may be the same as, or different from, the first heat shield) to the blade body. Aspects of the disclosure may preserve the structural integrity of the blade body during a removal and replacement of a shield. Furthermore, aspects of the disclosure may be used to remove and replace a shield within a couple of minutes (e.g., fifteen minutes), thereby facilitating quick turn-around times for reprocessing/refurbishing a blade. 
         [0036]    Aspects of the disclosure have been described in terms of illustrative embodiments thereof. Numerous other embodiments, modifications, and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure. For example, one of ordinary skill in the art will appreciate that the steps described in conjunction with the illustrative figures may be performed in other than the recited order, and that one or more steps illustrated may be optional in accordance with aspects of the disclosure. One or more features described in connection with a first embodiment may be combined with one or more features of one or more additional embodiments.