Patent Abstract:
A gas turbine vane to improve vane performance by addressing known failure mechanisms. A cooling circuit to the trailing edge of a vane airfoil is fed from the outer diameter platform, which prevents failure due to an oxidized and eroded airfoil trailing edge. The gas turbine includes an outer diameter platform, a hollow airfoil and an inner diameter platform with a plurality of cooling tubes extending radially through the airfoil. The cooling tubes are open at the outer diameter end and closed with covers at the inner diameter end. The inner diameter platform is also cooled and includes a meterplate for a portion of the cooling passageway and includes an undercut to improve thermal deflections of the inner diameter platform.

Full Description:
TECHNICAL FIELD 
       [0001]    The present invention generally relates to a cooled vane component in a gas turbine engine. More specifically, the gas turbine vane has an improved cooling flow design and lower operating stresses. 
       BACKGROUND OF THE INVENTION 
       [0002]    Gas turbine engines operate to produce mechanical work or thrust. Specifically, land-based gas turbine engines typically have a generator coupled thereto for the purposes of generating electricity. A gas turbine engine comprises an inlet that directs air to a compressor section, which has stages of rotating compressor blades. As the air passes through the compressor, the pressure of the air increases. The compressed air is then directed into one or more combustors where fuel is injected into the compressed air and the mixture is ignited. The hot combustion gases are then directed from the combustion section to a turbine section by a transition duct. The hot combustion gases cause the stages of the turbine to rotate, which in turn, causes the compressor to rotate. 
         [0003]    The air and hot combustion gases are directed through a turbine section by turbine blades and vanes. These blades and vanes are subject to extremely high operating temperatures, often times upwards of 2800 deg. F. These temperatures often exceed the material capability from which the blades and vanes are made. Extreme temps also cause thermal growth in the component, which if not permitted, causes thermal stresses and can lead to cracking. In order to lower the effective operating temperature, the blades and vanes are cooled, often with air or steam. However, the cooling must occur in an effective way so as to use the cooling fluid efficiently. 
       SUMMARY 
       [0004]    In accordance with the present invention, there is provided a novel configuration for a gas turbine vane assembly that provides effective cooling to gas-path surfaces while permitting movement of the platform. The vane assembly includes a plurality of airfoil cooling tubes and directed cooling to a vane platform. 
         [0005]    In an embodiment of the present invention, a gas turbine vane assembly comprises an outer diameter pan coupled to an outer diameter platform, a hollow airfoil extending radially inward from the outer diameter platform, and an inner diameter platform connected to the hollow airfoil opposite the outer diameter platform such that the platforms are generally parallel to each other. The outer diameter platform has a trailing edge face spaced an axial distance from a leading edge face and includes a plurality of openings capable of receiving a plurality of cooling tubes and a tube collar associated with each of the plurality of openings. The plurality of cooling tubes extend radially inward from the outer diameter platform such that the tube collars are connected to each of the plurality of cooling tubes and the corresponding opening at the outer diameter platform. The plurality of cooling tubes extend through passages in the airfoil. The inner diameter platform includes a trailing edge face, a leading edge face, a plurality of corresponding openings for receiving the plurality of cooling tubes. A cover is fixed to each of the plurality of cooling tubes proximate the inner diameter platform and a forward pan is coupled to a forward end of the inner diameter platform while a meterplate is fixed to the inner diameter platform adjacent to the forward pan and is in fluid communication with an aft pan that is connected to an aft end of the inner diameter platform. The meterplate has a plurality of holes located therein capable of restricting a cooling fluid flow to a desired pressure and mass flow for a region of the holes positioned in the inner diameter platform and in fluid communication with the aft cavity. An aft cover is fixed to the aft end of the inner diameter platform to form an aft cavity. The inner diameter platform also includes a plurality of holes that receive a cooling fluid from the aft pan. An undercut is positioned in the inner diameter platform for providing increased flexibility to the inner diameter platform. 
         [0006]    In an alternate embodiment, a flow restriction device capable of controlling a cooling fluid to an aft portion of an inner diameter platform of a gas turbine vane comprises an aft cover fixed to the inner diameter platform forming an aft cavity, a meterplate with a plurality of feed holes fixed to the inner diameter platform between a forward pan and the aft cover, a plurality of file cooling holes located in the inner diameter platform and in fluid communication with the aft cavity, and wherein the cooling fluid is capable of passing through the feed holes of the meterplate, into the aft cavity, and through the plurality of film cooling holes. 
         [0007]    In yet another embodiment, an inner diameter platform of a gas turbine vane capable of increased thermal deflection comprise a gas path surface separated from a cold surface by a platform thickness, a forward pan, and an aft cover fixed to the cold surface. The platform thickness having an undercut extending between the gas path surface and cool surface, such that the undercut reduces stiffness of the inner diameter platform adjacent to the aft cover. 
         [0008]    Additional advantages and features of the present invention will be set forth in part in a description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned from practice of the invention. The instant invention will now be described with particular reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0009]    The present invention is described in detail below with reference to the attached drawing figures, wherein: 
           [0010]      FIG. 1  is an exploded view of the a gas turbine vane in accordance with an embodiment of the present invention. 
           [0011]      FIG. 2A  is a perspective view of an embodiment of the present invention including a plurality tube collars. 
           [0012]      FIG. 2B  is an alternate perspective view of an embodiment of the present invention that includes an outer diameter pan over the outer diameter platform. 
           [0013]      FIG. 3  is a cross section view looking at the gas path surface of the outer diameter platform in accordance with an embodiment of the present invention. 
           [0014]      FIG. 4  is a perspective view of a trailing edge cooling tube used in an embodiment of the present invention. 
           [0015]      FIG. 5  is a perspective view of a mid-body cooling tube used in an embodiment of the present invention. 
           [0016]      FIG. 6  is a cross section view looking at the gas path surface of the inner diameter platform in accordance with an embodiment of the present invention. 
           [0017]      FIG. 7  is a perspective view looking at the cool surface of the inner diameter platform without the inner diameter pan in accordance with an embodiment of the present invention. 
           [0018]      FIG. 8A  is a detailed perspective view of a portion of  FIG. 7  in accordance with an embodiment of the present invention. 
           [0019]      FIG. 8B  is a detailed perspective view similar to that of  FIG. 8A  but with the aft pan in place in accordance with an embodiment of the present invention. 
           [0020]      FIG. 9  is a perspective view from the cool surface of the inner diameter platform with the inner diameter pan connected to the aft end of the inner diameter platform in accordance with an embodiment of the present invention. 
           [0021]      FIG. 10  is a detailed perspective view of an inner diameter platform in accordance with an alternate embodiment of the present invention. 
           [0022]      FIG. 11  is a cross section view of the airfoil of the vane assembly in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The subject matter of the present invention is described with specificity herein to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different components, combinations of components, steps, or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. 
         [0024]    Referring to  FIG. 1 , an exploded view of the gas turbine vane  100 , is depicted. An outer diameter pan  102  is affixed to the outer diameter platform  112  and has a plurality of holes  103 . Acceptable means for fixing the outer diameter pan  102  to the outer diameter platform  112  includes welding or brazing. The outer diameter platform  112  has a cool surface  111  and a gas path surface  113 . A plurality of cooling tubes  104 ,  106 , and  108  extend from the outer diameter platform  112 . Specifically, the leading edge cooling tube  104 , mid-body cooling tube  106 , and the trailing edge cooling tube  108  are placed through openings in the outer diameter platform  112 , extending through the hollow airfoil  114  and reaching respective openings in the inner diameter platform  116 . Each opening in the outer diameter platform  112  has a respective tube collar  110  that is affixed to each of the cooling tubes  104 ,  106 , and  108  and the corresponding opening. The outer diameter platform  112  has a leading edge face  112 A and a trailing edge face  112 B. 
         [0025]    The cooling tubes  104 ,  106 ,  108  are capped at the inner diameter platform  116 . This embodiment illustrates three cooling tubes but the quantity of cooling tubes is not limited to exclusively three tubes. Covers  120  are affixed to the openings of the tubes to prevent cooling fluid from flowing from the airfoil  114  into the inner diameter platform  116 . The inner diameter platform  116  has a gas path surface  115  and a cool surface  117  that are separated by a platform thickness. The inner diameter platform  116  has a leading edge face  116 A and a trailing edge face  116 B. 
         [0026]    An undercut  118  is located along within the inner platform thickness of the inner diameter platform  116 . The undercut  118  extends between the gas path surface  115  and the cool surface  117 . The undercut  118  can also be located adjacent to a joint between the aft cover  126  and the inner diameter platform  116 . The undercut  118  provides for increased flexibility of the inner diameter platform  116 , which helps to decrease the stress in the joint between the aft cover  126  and the inner platform  116 . Extending along the inner platform is a rail  119  that provides structural rigidity to the inner diameter platform  116 . 
         [0027]    A meterplate  122  is affixed to the inner diameter platform  106  adjacent to a forward pan  124 . The meterplate  122  is oriented generally perpendicular to the inner diameter platform  116  so as to close an opening in the aft cavity while permitting a flow of the cooling fluid to enter the aft cavity generally parallel to the inner diameter platform  116 . The meterplate  122  restricts a supply of fluid flow to a desired pressure and mass flow for a region of film holes between a forward plenum and an aft plenum formed adjacent to the inner diameter platform  116 . 
         [0028]    A forward pan  124  is affixed to the forward end of the inner diameter platform  116  and has a plurality of cooling holes  148 . An aft pan  126  is affixed to the aft end of the inner diameter platform  116  and does not have any cooling holes located therein. The aft pan  126  forms an aft cavity and has a generally flat portion and three sidewalls. Acceptable means for fixing the aft pan and the forward pan includes welding or brazing. In the gas turbine vane assembly  100 , the outer diameter platform  112 , the airfoil  114 , and the inner diameter platform  116  can be one single part, a welded assembly of parts, or any combination in between. 
         [0029]    Referring to  FIG. 2A , a view of the cool surface  111  of the outer diameter platform  112  without the outer diameter pan  102 , is depicted. The outer diameter platform has a trailing edge face and a leading edge face, where the outer diameter platform trailing edge face is spaced an axial distance from the outer diameter platform leading edge face. The openings for each of the cooling tubes is shown and fixed to the openings are the tube collars  110  for the corresponding cooling tubes. Referring to  FIG. 2B , a view of the cool surface  111  of the outer diameter platform  112  with the outer diameter pan  102 , is depicted. The figure illustrates how the outer diameter pan  102  is affixed to the outer diameter platform  112 . The plurality of cooling holes  103  located on the outer diameter pan  102  are oriented at a surface angle relative to the outer diameter platform  112 . 
         [0030]    Referring to  FIG. 3 , a cross section view looking at the gas path surface  113  of the outer diameter platform  112 , is depicted. A plurality of cooling holes  121  are illustrated. Also, there are the openings for each of the cooling tubes. The cooling holes  103  located on the outer diameter pan  102  supply cooling fluid to pass through the cooling holes  121  to cool the gas path  113  surface of the outer diameter platform  112 . 
         [0031]    Referring to  FIG. 4 , an illustration of a trailing edge cooling tube  108 , is depicted. The trailing edge (TE) cooling tube  108  has an opening  128 , an opposing end  130  and a plurality of cooling holes  132 . The opening  128  receives cooling fluid from the outer diameter platform  102  with the cooling fluid passing through the tube  108 . The end  130  of the TE cooling tube  108  is closed by a cover  120  which prevents the cooling fluid from flowing into the inner diameter platform  116 . Since the cooling fluid is trapped in the body of the TE cooling tube  108 , the cooling fluid is forced out through the plurality of holes  132 . The cooling fluid exits the cooling tube and is directed towards an inner wall of the airfoil  114  and thus, cooling the airfoil  114 . The cooling fluid can be air or stream or a comparable cooling fluid. The TE cooling tube  108  also has raised surfaces  134  along the tube  108 . These raised surfaces  134  touch the inside of the airfoil and helps to hold the tube in place. 
         [0032]    Referring to  FIG. 5 , an illustration of a mid-body cooling tube  106 , is depicted. The mid-body cooling tube  106  has an opening  136 , and an opposing end  138 , and a plurality of cooling holes  140 . Similar to the TE cooling tube  108 , the mid-body cooling tube  106  directs cooling fluid from the outer diameter platform  112  and into the opening  136  of the mid-body cooling tube  106 . The cooling fluid is trapped in the body of the tube  106  because the end  138  is closed off with a cover  120  affixed at the inner diameter platform  116 . This forces the cooling fluid to pass through the plurality of holes  140  and onto the inner wall of the airfoil  114 . 
         [0033]    Referring to  FIG. 6 , a cross section view looking at the gas path surface  115  of the inner diameter platform  116 , is depicted. This view is from the gas path side  115  of the turbine vane. The inner diameter platform  116  can have a plurality of cooling holes  142  for directing a supply of cooling fluid along the gas path surface  115  of the inner diameter platform  116 . The cooling holes  142  could be oriented at a surface angle relative to the inner diameter platform  116 . This allows for improved cooling of the gas path surface  115  of the inner diameter platform  116 . 
         [0034]    Referring to  FIG. 7 , a view looking at the cool surface  117  of the inner diameter platform  116  without the inner diameter pan  124 , is depicted. The covers  120  are affixed to the cooling tubes to prevent cooling fluid from flowing into the cooling tubes  104 ,  106 , and  108  from the inner diameter platform  116 . The meterplate  122  is shown affixed to an inner rail  119  of the inner diameter platform  116 . The undercut  118  in the inner diameter platform  116  is also visible. The exact size and shape of the undercut  118  can vary depending on the vane configuration. However, the shape of the undercut  118  is designed to reduce any stress concentrations and to decrease stiffness in the inner diameter platform  116 . In one embodiment, as shown in  FIG. 7 , the undercut  118  has a general U-shape cross section. 
         [0035]    Referring to  FIG. 8A , a close up view of the sidewall portion of the inner diameter platform  116  of  FIG. 7 , is depicted.  FIG. 8A  illustrates an example of a sheet metal seal slot  146  along one of the side walls of the inner diameter platform  116  and outer diameter platform  112 . There are a plurality of cooling holes  144  extending through the inner diameter platform  116 . Cooling fluid is provided through the cooling holes  148  of the inner diameter pan  124 . The cooling fluid is passed through the plurality of holes  144  on the cool side of the inner diameter platform  116 . The cooling fluid then passes through the cooling holes  142  on the gas path surface  115  of the inner diameter platform  116  to help cool the gas path surface  115  of the turbine vane. The illustrated slot  146  is an example of the orientation and position of a sealing slot. A sheet metal seal fits into the slot  146 . 
         [0036]    Referring to  FIG. 8B , a similar view to  FIG. 8A , but with the aft pan  126  included. The aft pan  126  receives the cooling fluid and directs the cooling fluid into the inner diameter platform  116  and through the plurality of cooling holes  144  located along the inner diameter gas path surface  115 . 
         [0037]    Referring to  FIG. 9 , a view looking at the cool surface  117  of the inner diameter platform  116  with the inner diameter pan  124 , is depicted. The inner diameter pan  124  can have a plurality of cooling holes  148  for receiving a supply of cooling fluid and directing the cooling fluid to holes  142  in the inner diameter platform. In this view of the inner diameter platform  116 , the undercut  118 , the meterplate  122  and the cooling tube covers  120  are visible. 
         [0038]    Referring to  FIG. 10 , a close up, cutaway section of the cool surface  117  of the inner diameter platform  116 , is depicted. In this view of the inner diameter platform  116 , the undercut  118  and the aft pan  126  are visible. 
         [0039]    Referring to  FIG. 11 , a view from the top of the cross section of the airfoil  114 , is depicted. The figure illustrates the three hollow cavities for holding the three cooling tubes  104 ,  106 , and  108 . However, the invention is not limited to three cavities within the airfoil and can be more or less than three. 
         [0040]    The present invention has been described in relation to particular embodiments, which are intended in all respects to be illustrative rather than restrictive. Alternative embodiments will become apparent to those of ordinary skill in the art to which the present invention pertains without departing from its scope. 
         [0041]    From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects set forth above, together with other advantages which are obvious and inherent to the system and method. It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and within the scope of the claims.

Technology Classification (CPC): 5