Abstract:
A method for producing one or more cooling holes in an airfoil for a gas turbine engine is disclosed. The method includes casting one or more hole starter bosses on a suction side, a pressure side, or both of the airfoil, drilling the one or more cooling holes into the airfoil by way of the one or more hole starter bosses, and removing the one or more hole starter bosses after drilling the one or more cooling holes into the airfoil.

Description:
FIELD 
       [0001]    Embodiments of the disclosure relate generally to gas turbine engines and more particularly relate to systems and methods for producing one or more cooling holes in an airfoil for a gas turbine engine. 
       BACKGROUND 
       [0002]    In some instances, buckets may be cooled with radial holes that exit (or break out) on a surface of the airfoil rather than running the full length of the airfoil and emerging at the tip. Such cooling holes may break out of the airfoil in the shape of a long, narrow, ellipse. It can be very difficult to drill holes into the airfoil at such a shallow angle. 
       BRIEF DESCRIPTION 
       [0003]    Some or all of the above needs and/or problems may be addressed by certain embodiments of the disclosure. According to one embodiment, there is disclosed a method for producing one or more cooling holes in an airfoil for a gas turbine engine. The method may include casting one or more hole starter bosses on a suction side, a pressure side, or both of the airfoil, drilling the one or more cooling holes into the airfoil by way of the one or more hole starter bosses, and removing the one or more hole starter bosses after drilling the one or more cooling holes into the airfoil. 
         [0004]    According to another embodiment, there is disclosed an airfoil for a gas turbine engine. The airfoil may include a suction side, a pressure side opposite the suction side, and one or more hole starter bosses cast on the suction side, the pressure side, or both. 
         [0005]    Further, according to another embodiment, there is disclosed a method for producing one or more cooling holes in an airfoil for a gas turbine engine. The method may include casting one or more hole starter bosses on a suction side, a pressure side, or both of the airfoil, drilling one or more line-of-sight access holes in a shroud of the airfoil to provide access to the one or more hole starter bosses, drilling the one or more cooling holes into the airfoil by way of the one or more hole starter bosses, and grinding the one or more hole starter bosses after drilling the one or more cooling holes into the airfoil. 
         [0006]    Other embodiments, aspects, and features of the disclosure will become apparent to those skilled in the art from the following detailed description, the accompanying drawings, and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale. 
           [0008]      FIG. 1  schematically depicts an example view of a gas turbine engine according to an embodiment of the disclosure. 
           [0009]      FIG. 2  schematically depicts an example airfoil according to an embodiment of the disclosure. 
           [0010]      FIG. 3  schematically depicts an example airfoil according to an embodiment of the disclosure. 
           [0011]      FIG. 4  schematically depicts an example airfoil according to an embodiment of the disclosure. 
           [0012]      FIG. 5  schematically depicts an example airfoil according to an embodiment of the disclosure. 
           [0013]      FIG. 6  schematically depicts an example airfoil according to an embodiment of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Illustrative embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. The disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like numbers refer to like elements throughout. 
         [0015]    Illustrative embodiments of the disclosure are directed to, among other things, systems and methods for producing one or more cooling holes in an airfoil for a gas turbine engine. In some instances, one or more hole starter bosses may be cast on a suction side, a pressure side, or both of the airfoil. Using the hole starter bosses as a guide, the cooling holes may be drilled into the surface of the suction side or the pressure side of the airfoil. The starter bosses may enable a relatively steep drill angle into the surface of the airfoil. After the cooling holes have been drilled into the surface of the airfoil, the hole starter bosses may be removed. For example, the hole starter bosses may be ground off of the surface of the airfoil. 
         [0016]    In some instances, a shroud at the tip of the airfoil may prevent adequate access to the hole starter bosses. For example, the shroud may block the drill angle or the line-of-sight of a drill to the hole starter bosses. In such instances, one or more line-of-sight access holes may be drilled or cast into the shroud of the airfoil to provide access to the hole starter bosses. After the cooling holes have been drilled into the surface of the airfoil, the line-of-sight access holes may be filled in. For example, the line-of-sight access holes may be sealed by brazing, plugging, welding, or covered with a plate that may be brazed or welded in place. The cover could be on either the flowpath side or the seal side of the shroud and could be recessed so as to create a smooth surface. Other means of closing the line-of-sight access holes may also be used. In some instances, the line-of-sight access holes may be left open. 
         [0017]    In addition, one or more holes may be drilled into a shank of the airfoil. In this manner, the cooling holes drilled into the surface of the airfoil may meet with the holes drilled up from the shank so that the cooling holes are in fluid communication with the holes in the shank of the airfoil. Accordingly, cooling air may flow from the holes in the shank of the airfoil, through the cooling holes, and out of the surface of the suction side and/or the pressure side of the airfoil. 
         [0018]    In certain embodiments, the hole starter bosses may include a protrusion projecting from the surface of the suction side and/or the pressure side of the airfoil. In other instances, the hole starter bosses may include an indentation on the surface of the suction side and/or the pressure side of the airfoil. The hole starter bosses may include a single hole or a number of holes. The holes can be round or other producible shapes. The hole starter bosses, whether a protrusion or an indentation, may be cast on the surface the airfoil. If an indentation, the hole starter bosses can also be produced by the removal of material using electrical discharge machining or other means. 
         [0019]    Turning now to the drawings,  FIG. 1  shows a schematic view of gas turbine engine  100  as may be used herein. The gas turbine engine  100  may include a compressor  102 . The compressor  102  compresses an incoming flow of air  104 . The compressor  102  delivers the compressed flow of air  104  to a combustor  106 . The combustor  106  mixes the compressed flow of air  104  with a compressed flow of fuel  108  and ignites the mixture to create a flow of combustion gases  110 . Although only a single combustor  106  is shown, the gas turbine engine  100  may include any number of combustors  106 . The flow of combustion gases  110  is in turn delivered to a downstream turbine  112 . The flow of combustion gases  110  drives the turbine  112  to produce mechanical work. The mechanical work produced in the turbine  112  drives the compressor  102  via a shaft  114  and an external load  116 , such as an electrical generator or the like. 
         [0020]    The gas turbine engine  100  may use natural gas, various types of syngas, and/or other types of fuels. The gas turbine engine  100  may be anyone of a number of different gas turbine engines such as those offered by General Electric Company of Schenectady, New York and the like. The gas turbine engine  100  may have different configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together. 
         [0021]      FIG. 2  schematically depicts one example embodiment of an airfoil  200  that may be used in the compressor  102  or the turbine  112  of  FIG. 1 . The airfoil  200  may include a leading edge  202 , a trailing edge  204 , a suction side  206  defined between the leading edge  202  and the trailing edge  204 , and a pressure side  208  defined between the leading edge  202  and the trailing edge  204  opposite the suction side  206 . The airfoil  200  may include a platform  210 , a shank  212 , a dovetail  214 , and a tip shroud  216 . 
         [0022]    As depicted in  FIG. 3 , the airfoil  200  may include a number of cooling holes  218  that exit (or break out) of the airfoil  200  in the shape of a long, narrow, ellipse  220  on the surface of the suction side  206  and/or the pressure side  208 . The cooling holes  218  may be drilled using the Shaped Tube Electrochemical Machining (STEM) process. The angle of the cooling holes  218  relative to the surface of the airfoil  200  can make it very difficult to drill the cooling holes  218  into the airfoil  200  at such a shallow angle. 
         [0023]    As depicted in  FIG. 4 , one or more hole starter bosses  222  may be cast on the suction side  206  and/or the pressure side  208  of the airfoil  200  to enable the production of the radial cooling holes  218  that break through the airfoil surface on the suction side  206  and/or the pressure side  208 . Using the hole starter bosses  222  as a guide, the cooling holes  218  may be drilled into the surface of the airfoil  200 . In this manner, the starter bosses  222  may enable a relatively step drill angle into the surface of the airfoil  200 . After the cooling holes  218  have been drilled into the surface of the airfoil  200 , the hole starter bosses  222  may be removed. For example, the hole starter bosses  222  may be ground off of the surface of the suction side  206  and/or the pressure side  208  of the airfoil  200 . 
         [0024]    In certain embodiments, the hole starter bosses  222  may include a protrusion  224  projecting from the surface of the suction side  206  and/or the pressure side  208  of the airfoil  200 . In other instances, the hole starter bosses  222  may include an indentation on the surface of the suction side  206  and/or the pressure side  208  of the airfoil  200 . The hole starter bosses  222  may include a single hole  226  or a number of holes. The holes  226  may act as drill guides. The holes  226  can be round or other producible shapes. The hole starter bosses  222 , whether a protrusion  224  or an indentation, may be cast on the surface of the suction side  206  and/or the pressure side  208  of the airfoil  200 . If an indentation, the hole starter bosses  222  can also be produced by the removal of material using electrical discharge machining or other means. 
         [0025]    In some instances, the shroud  216  at the tip of the airfoil  200  may prevent adequate access to the hole starter bosses  222 . For example, the shroud  216  may block the drill angle or the line-of-sight of a drill to the hole starter bosses  222 . In such instances, as depicted in  FIG. 5 , one or more line-of-sight access holes  228  may be drilled or cast into the shroud  216  of the airfoil  200  to provide access to the hole starter bosses  222 . After the cooling holes  218  have been drilled into the surface of the airfoil  200 , the line-of-sight access holes  228  may be filled in. For example, the line-of-sight access holes  228  may be sealed by brazing, plugging, welding, or covered with a plate that may be brazed or welded in place. The cover could be on either the flowpath side or the seal side of the shroud  216  and could be recessed so as to create a smooth surface. Other means of closing the line-of-sight access holes  228  may also be used. In some instances, the line-of-sight access holes  228  may be left open. 
         [0026]    In addition, as depicted in  FIG. 6 , one or more holes  230  may be drilled into the shank  212  of the airfoil  200 . In this manner, the cooling holes  218  drilled into the surface of the suction side  206  and/or the pressure side  208  of the airfoil  200  may meet with the holes  230  drilled up from the shank  212  so that the cooling holes  218  are in fluid communication with the holes  230  in the shank  212  of the airfoil  200 . Accordingly, cooling air may flow from the holes  230  in the shank  212  of the airfoil  200 , through the cooling holes  218 , and out of the surface of the suction side  206  and/or the pressure side  208  of the airfoil  200 . 
         [0027]    Although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments.