Patent Publication Number: US-2017370231-A1

Title: Turbine airfoil cooling system with integrated airfoil and platform cooling system

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Development of this invention was supported in part by the United States Department of Energy, Contract No. DE-FC26-05NT42644. Accordingly, the United States Government may have certain rights in this invention. 
    
    
     FIELD OF THE INVENTION 
     This invention is directed generally to turbine airfoils, and more particularly to cooling systems in hollow turbine airfoils. 
     BACKGROUND 
     Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. Combustors often operate at high temperatures that may exceed 2,500 degrees Fahrenheit. Typical turbine combustor configurations expose turbine blade assemblies to these high temperatures. As a result, turbine blades must be made of materials capable of withstanding such high temperatures. In addition, turbine blades often contain cooling systems for prolonging the life of the blades and reducing the likelihood of failure as a result of excessive temperatures. 
     Typically, turbine blades are formed from a root portion having a platform at one end and an elongated portion forming a blade that extends outwardly from the platform coupled to the root portion. The blade is ordinarily composed of a tip opposite the root section, a leading edge, and a trailing edge. The inner aspects of most turbine blades typically contain an intricate maze of cooling channels forming a cooling system. The cooling channels in a blade receive air from the compressor of the turbine engine and pass the air through the blade. The cooling channels often include multiple flow paths that are designed to maintain all aspects of the turbine blade at a relatively uniform temperature. However, centrifugal forces and air flow at boundary layers often prevent some areas of the turbine blade from being adequately cooled, which results in the formation of localized hot spots. Localized hot spots, depending on their location, can reduce the useful life of a turbine blade and can damage a turbine blade to an extent necessitating replacement of the blade. Blade platforms often include cooling passageways drawing cooling air from the cavity under the platform. These cooling passages are typically interconnected to provide cooling coverage. However, the forward rotor cooling cavity can be subject to hot gas ingestion, which results in much warmer air under the blade platform and negatively impacts the platform cooling. Thus, a need exists for a turbine blade with an improved cooling system that overcomes these shortcomings. 
     SUMMARY OF THE INVENTION 
     A cooling system for a turbine airfoil of a turbine engine having one or more mid-chord cooling channels that extend through both the airfoil and a platform of the airfoil to provide adequate cooling to the platform while cooling the airfoil is disclosed. The mid-chord cooling channel may be formed from an airfoil portion extending generally spanwise within the airfoil and a platform portion extending into a platform of the airfoil with a larger cross-sectional area than a cross-sectional area of the airfoil portion. The mid-chord cooling channel may also extend into the platform of the airfoil a distance laterally outside of a silhouette of the airfoil defined by the leading edge, trailing edge, pressure side and suction side of the airfoil. Thus, the mid-chord cooling channel extends laterally into the platform to provide adequate cooling the platform. 
     In at least one embodiment, the turbine airfoil may include a generally elongated, hollow airfoil having a leading edge, a trailing edge, a pressure side, a suction side, a tip section at a first end, a root coupled to the airfoil at an end generally opposite the first end for supporting the airfoil and for coupling the airfoil to a disc. The turbine airfoil may also include a platform at an intersection between the root and the generally elongated, hollow airfoil and extending generally orthogonal to a longitudinal axis of the generally elongated, hollow airfoil, and a cooling system formed from at least one cavity in the elongated, hollow airfoil. The cooling system may include one or more mid-chord cooling channels having one or more airfoil portions extending generally spanwise within the airfoil and having one or more platform portions extending into the platform of the airfoil with a larger cross-sectional area than a cross-sectional area of the at least one airfoil portion, whereby the cross-sectional areas are taken parallel to each other. The mid-chord cooling channel may be formed from a serpentine cooling channel formed from one or more first outbound legs and one or more second inbound legs coupled to the first outbound leg via a first turn. The first outbound leg may include one or more airfoil portions extending generally spanwise within the airfoil and having one or more platform portions extending into the platform of the airfoil with a larger cross-sectional area than a cross-sectional area of the at least one airfoil portion of the first outbound leg, whereby the cross-sectional areas are taken parallel to each other. 
     The platform portion may extend into the platform of the airfoil a distance laterally outside of a silhouette of the airfoil defined by the leading edge, trailing edge, pressure side and suction side of the airfoil. The serpentine cooling channel may be formed from one or more third outbound legs coupled to the second inbound leg via a second turn. The second turn may extend into the platform of the airfoil with a larger cross-sectional area than a cross-sectional area of the second inbound leg within the airfoil, whereby the cross-sectional areas are taken parallel to each other. The second turn may extend into the platform of the airfoil a distance laterally outside of a silhouette of the airfoil defined by the leading edge, trailing edge, pressure side and suction side of the airfoil. The serpentine cooling channel may be formed from one or more fourth inbound legs coupled to the third outbound leg via a third turn. One or more fifth outbound legs may be coupled to the fourth inbound leg via a fourth turn. The fourth turn may extend into the platform of the airfoil with a larger cross-sectional area than a cross-sectional area of the fourth inbound leg within the airfoil, wherein the cross-sectional areas are taken parallel to each other. The fourth turn may extend into the platform of the airfoil a distance laterally outside of a silhouette of the airfoil defined by the leading edge, trailing edge, pressure side and suction side of the airfoil. The fourth turn may extend into the platform of the airfoil a distance laterally outside of a silhouette of the airfoil on the pressure side and may extend a distance laterally outside of a silhouette of the airfoil on the suction side of the airfoil. 
     A plurality of film cooling holes may extend from the trailing edge cooling channel in the platform to a radially outer surface of the platform. The plurality of film cooling holes may include at least one film cooling hole extending from a portion of the trailing edge cooling channel outside of the silhouette of the airfoil on the pressure side and at least one film cooling hole extending from a portion of the trailing edge cooling channel outside of the silhouette of the airfoil on the suction side. 
     During use, cooling fluids may be received into the cooling system from a cooling fluid supply through the root. The cooling system integrates platform and airfoil cooling through the serpentine cooling channel, previously described. The flow circulation of cooling fluid inside the airfoil also circulates into the platform to form an efficient cooling system without adding additional air for the platform. The aft cooling circuit may first receive cooling fluids from the root and cool the platform before entering into the first outbound leg. The cooling fluids flow through the first turn into the second inbound leg, into the second turn and the third outbound leg, into the third turn and fourth inbound leg, and into the fourth turn and the fifth outbound leg. The fifth outbound leg exhausts the cooling fluid into a trailing edge cooling channel. The cooling fluid may pass zigzag features configured to enhance trailing edge cooling. At the inner end of the trailing edge cooling channel, the cooling system is extended into the pressure and suction sides of the platform to enhance cooling. The cooling fluid also passes into the film cooling holes to further enhance cooling. 
     These and other embodiments are described in more detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention. 
         FIG. 1  is a perspective view of a suction side of a turbine airfoil with the cooling system. 
         FIG. 2  is a perspective view of a pressure side of the turbine airfoil of  FIG. 1  with the cooling system. 
         FIG. 3  is a filleted cross-sectional view of the turbine airfoil shown in  FIG. 1  taken along line  3 - 3 . 
         FIG. 4  is a cross-sectional view of the platform of the turbine airfoil shown in  FIG. 3  taken along line  4 - 4 . 
         FIG. 5  is a cross-sectional view of the turbine airfoil shown in  FIG. 3  taken along line  5 - 5 . 
         FIG. 6  is a perspective view of the turbine airfoil shown in  FIG. 3  in which the cooling system is shown and the airfoil is shown in phantom, dashed lines. 
         FIG. 7  is a detail view of the cooling system of the turbine airfoil shown in  FIG. 6 . 
         FIG. 8  is a side view of the turbine airfoil shown in  FIG. 3  in which the cooling system is shown and the airfoil is shown in phantom, dashed lines. 
         FIG. 9  is a detail view of the cooling system in the platform of the turbine airfoil shown in  FIG. 8 . 
         FIG. 10  is a pressure side view of the turbine airfoil shown in  FIG. 3  in which the cooling system is shown and the airfoil is shown in phantom, dashed lines. 
         FIG. 11  is a forward looking aft view of the turbine airfoil shown in  FIG. 3  in which the cooling system is shown and the airfoil is shown in phantom, dashed lines. 
         FIG. 12  is a suction side view of the turbine airfoil shown in  FIG. 3  in which the cooling system is shown and the airfoil is shown in phantom, dashed lines. 
         FIG. 13  is an aft looking aft view of the turbine airfoil shown in  FIG. 3  in which the cooling system is shown and the airfoil is shown in phantom, dashed lines. 
         FIG. 14  is a pressure side view of the cooling system of the turbine airfoil shown in  FIG. 10 . 
         FIG. 15  is a forward looking aft view of the cooling system of the turbine airfoil shown in  FIG. 11 . 
         FIG. 16  is a suction side view of the cooling system of the turbine airfoil shown in  FIG. 12 . 
         FIG. 17  is an aft looking aft view of the cooling system of the turbine airfoil shown in  FIG. 13 . 
         FIG. 18  is a perspective view of the turbine airfoil shown in  FIG. 3  in which the cooling system having film cooling holes is shown and the airfoil is shown in phantom, dashed lines. 
         FIG. 19  is a detail view of the cooling system having film cooling holes shown in  FIG. 18 . 
         FIG. 20  is a side view of the turbine airfoil shown in  FIG. 3  in which the cooling system with film cooling holes is shown and the airfoil is shown in phantom, dashed lines. 
         FIG. 21  is a detail view of the cooling system film cooling holes in the platform of the turbine airfoil shown in  FIG. 20 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIGS. 1-21 , a cooling system  10  for a turbine airfoil  12  of a turbine engine having one or more mid-chord cooling channels  16  that extend through both the airfoil  12  and a platform  18  of the airfoil  12  to provide adequate cooling to the platform  18  while cooling the airfoil  12  is disclosed. The mid-chord cooling channel  16  may be formed from an airfoil portion  20  extending generally spanwise within the airfoil  12  and a platform portion  22 , as shown in  FIG. 3 , extending into the platform  18  of the airfoil  12  with a larger cross-sectional area than a cross-sectional area of the airfoil portion  20 . The mid-chord cooling channel  16  may also extend into the platform  18  of the airfoil  12  a distance laterally outside of a silhouette  60  of the airfoil  12  defined by the leading edge  24 , trailing edge  26 , pressure side  28  and suction side  30  of the airfoil  12 . Thus, the mid-chord cooling channel  16  may extend laterally into the platform  18  to provide adequate cooling the platform  18 . 
     In at least embodiment, the turbine airfoil  12  may be formed from a generally elongated, hollow airfoil  32  having a leading edge  24 , a trailing edge  26 , a pressure side  28 , a suction side  30 , a tip section  34  at a first end  36 , a root  38  coupled to the airfoil  12  at an end  40  generally opposite the first end  36  for supporting the airfoil  12  and for coupling the airfoil  12  to a disc. The airfoil  12  may include a platform  18  at an intersection  42  between the root  38  and the generally elongated, hollow airfoil  32  and extending generally orthogonal to a longitudinal axis  44  of the generally elongated, hollow airfoil  32 , and a cooling system  10  formed from at least one cavity  46  in the elongated, hollow airfoil  32 . The cooling system  10  may include an aft cooling circuit  78  that may include one or more mid-chord cooling channels  16  having at least one airfoil portion  20  extending generally spanwise within the airfoil  12  and having at least one platform portion  22  extending into the platform  18  of the airfoil  12  with a larger cross-sectional area than a cross-sectional area of the airfoil portion  20 , whereby the cross-sectional areas are taken parallel to each other. The mid-chord cooling channel  16  may be formed from a serpentine cooling channel  54  formed from one or more first outbound legs  48  and one or more second inbound legs  50  coupled to the first outbound leg  48  via a first turn  52 . The first outbound leg  48  may include one or more airfoil portions  20  extending generally spanwise within the airfoil  12  and having at least one platform portion  22  extending into the platform  18  of the airfoil  12  with a larger cross-sectional area than a cross-sectional area of the airfoil portion  20  of the first outbound leg  48 , whereby the cross-sectional areas are taken parallel to each other. The platform portion  22  may extend into the platform  18  of the airfoil  12  a distance laterally outside of a silhouette  60  of the airfoil  12  defined by the leading edge  24 , trailing edge  26 , pressure side  28  and suction side  30  of the airfoil  12 . 
     The serpentine cooling channel  54  may be formed from one or more third outbound legs  56  coupled to the second inbound leg  50  via a second turn  58 . The second turn  58  may extend into the platform  18  of the airfoil  12  with a larger cross-sectional area than a cross-sectional area of the second inbound leg  50  within the airfoil  12 , wherein the cross-sectional areas are taken parallel to each other. The second turn  58  may extend into the platform  18  of the airfoil  12  a distance laterally outside of a silhouette  60  of the airfoil  12  defined by the leading edge  24 , trailing edge  26 , pressure side  28  and suction side  30  of the airfoil  12 . The serpentine cooling channel  54  may be formed from one or more fourth inbound legs  62  coupled to the third outbound leg  56  via a third turn  64 . The serpentine cooling channel  54  may be formed from one or more fifth outbound legs  66  coupled to the fourth inbound leg  62  via a fourth turn  68 . The fourth turn  68  may extend into the platform  18  of the airfoil  12  with a larger cross-sectional area than a cross-sectional area of the fourth inbound leg  62  within the airfoil  12 , wherein the cross-sectional areas are taken parallel to each other. The fourth turn  68  may extend into the platform  18  of the airfoil  12  a distance laterally outside of a silhouette  60  of the airfoil  12  defined by the leading edge  24 , trailing edge  26 , pressure side  28  and suction side  30  of the airfoil  12 . The fourth turn  68  may extend into the platform  18  of the airfoil  12  a distance laterally outside of a silhouette  60  of the airfoil  12  on the pressure side  28  and extends a distance laterally outside of a silhouette  60  of the airfoil  12  on the suction side  30  of the airfoil  12 . 
     The cooling system  10  may also include a trailing edge cooling channel  80 . The cooling fluid may pass zigzag features configured to enhance trailing edge cooling. The trailing edge cooling channel  80  may extend into the platform  18  of the airfoil  12  a distance laterally outside of a silhouette  60  of the airfoil  12  defined by the leading edge  24 , trailing edge  26 , pressure side  28  and suction side  30  of the airfoil  12 . The trailing edge cooling channel  80  may extend into the platform  18  of the airfoil  12  a distance laterally outside of a silhouette  60  of the airfoil  12  on the pressure side  28  and may extend a distance laterally outside of a silhouette  60  of the airfoil  12  on the suction side  30  of the airfoil  12 . 
     The cooling system  10  may also include a plurality of film cooling holes  70  extending from the trailing edge cooling channel  80  in the platform  18  to a radially outer surface  70  of the platform  18 . The plurality of film cooling holes  70  may include one or more film cooling holes  70  extending from a portion of the trailing edge cooling channel  80  outside of the silhouette  60  of the airfoil  12  on the pressure side  28  and one or more film cooling holes  70  extending from a portion of the trailing edge cooling channel  80  outside of the silhouette  60  of the airfoil  12  on the suction side  30 . The cooling system  10  may also include one or a plurality of film cooling holes  70  extending from cooling passages in the platform  18 , such as mid-chord cooling channel  16  or fourth turn  68 , to a radially outer surface  70  of the platform  18  on the pressure side  28 . 
     The cooling system  12  may also include a forward cooling circuit  72 , as shown in  FIG. 5 . The forward cooling circuit  72  may include a leading edge impingement channel  74  with helical flow in combination with a blade tip axial cooling passage  76 , as shown in  FIG. 3 . 
     During use, cooling fluids may be received into the cooling system  10  from a cooling fluid supply through the root  38 . The cooling system  10  integrates platform and airfoil cooling through the serpentine cooling channel  54 , previously described. The flow circulation of cooling fluid inside the airfoil  12  also circulates into the platform  18  to form an efficient cooling system  12  without adding additional air for the platform  18 . The aft cooling circuit  78  may first receive cooling fluids from the root  38  and cool the platform  18  before entering into the first outbound leg  48 . The cooling fluids flow through the first turn  52  into the second inbound leg  50 , into the second turn  58  and the third outbound leg  56 , into the third turn  64  and fourth inbound leg  62 , and into the fourth turn  68  and the fifth outbound leg  66 . The fifth outbound leg  66  exhausts the cooling fluid into a trailing edge cooling channel  80 . The cooling fluid may pass zigzag features configured to enhance trailing edge cooling. At the inner end of the trailing edge cooling channel  80 , the cooling system  12  is extended into the pressure and suction sides  28 ,  30  of the platform  18  to enhance cooling. The cooling fluid also passes into the film cooling holes  70  to further enhance cooling. 
     The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.