Abstract:
A turbine airfoil usable in a turbine engine and having at least one cooling system is disclosed. At least a portion of the cooling system may include one or more cooling channels having a plurality of turbulators protruding from an inner surface and positioned generally nonorthogonal and nonparallel to a longitudinal axis of the airfoil cooling channel. The configuration of turbulators may create a higher internal convective cooling potential for the blade cooling passage, thereby generating a high rate of internal convective heat transfer and attendant improvement in overall cooling performance. This translates into a reduction in cooling fluid demand and better turbine performance.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Development of this invention was supported in part by the United States Department of Energy, Advanced Turbine Development Program, 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 hollow turbine airfoils having cooling channels for passing fluids, such as air, to cool the 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 vane and blade assemblies to these high temperatures. As a result, turbine vanes and blades must be made of materials capable of withstanding such high temperatures. In addition, turbine vanes and blades often contain cooling systems for prolonging the life of the vanes and blades and reducing the likelihood of failure as a result of excessive temperatures. 
     Typically, turbine blades are formed from an elongated portion forming a blade having one end configured to be coupled to a turbine blade carrier and an opposite end configured to form a blade tip. The blade is ordinarily composed of a leading edge, a trailing edge, a suction side, and a pressure side. The inner aspects of most turbine blades typically contain an intricate maze of cooling circuits forming a cooling system. The cooling circuits in the blades receive air from the compressor of the turbine engine and pass the air through the ends of the blade adapted to be coupled to the blade carrier. The cooling circuits often include multiple flow paths that are designed to maintain all aspects of the turbine blade at a relatively uniform temperature. At least some of the air passing through these cooling circuits is exhausted through orifices in the leading edge, trailing edge, suction side, and pressure side of the blade. While advances have been made in the cooling systems in turbine blades, a need still exists for a turbine blade having increased cooling efficiency for dissipating heat and passing a sufficient amount of cooling air through the blade. 
     SUMMARY OF THE INVENTION 
     A turbine airfoil cooling system configured to cool internal and external aspects of a turbine airfoil usable in a turbine engine is disclosed. In at least one embodiment, the turbine airfoil cooling system may be configured to be included within a turbine blade. While the description below focuses on a cooling system in a turbine blade, the cooling system may also be adapted to be used in a stationary turbine vane. The turbine airfoil cooling system may be formed from a cooling system having one or more cooling channels having any appropriate configuration. The cooling channels may include a plurality of turbulators for creating vortices within the cooling channels to increase the internal convective cooling potential of the cooling system, thereby increasing the overall performance of the cooling system. 
     A turbine airfoil may be formed from a generally elongated hollow airfoil formed from an outer wall, and having a leading edge, a trailing edge, a pressure side, a suction side, a root at a first end of the airfoil and a tip at a second end opposite to the first end, and a cooling system positioned within interior aspects of the generally elongated hollow airfoil. The turbine airfoil may include at least one cooling channel of the cooling system in the generally elongated hollow airfoil formed from an inner surface. The turbine airfoil may also include a plurality of center turbulators extending from the inner surface into the cooling channel and may form a set of center turbulators that are positioned nonorthogonally and nonparallel relative to a longitudinal axis of the cooling channel. The turbine airfoil may also include one or more outer turbulators extending from the inner surface into the at least one cooling channel and may be positioned nonorthogonally and nonparallel relative to a longitudinal axis of the cooling channel. In at least one embodiment, there may exist a plurality of outer turbulators in the cooling channel. The outer turbulator may have a leading edge that is positioned radially outward from the longitudinal axis and a trailing edge that is positioned radially outward further from the longitudinal axis than a trailing edge of the center turbulators. The outer turbulator may be offset in a downstream direction from at least one of the center turbulators. 
     The set of center turbulators may be formed from a right side set of center turbulators and a left side set of center turbulators. The right side set of center turbulators may extend nonorthogonally and nonparallel relative to the longitudinal axis and may be a mirror image of the left side set of center turbulators such that leading edges of center turbulators from the right side set are aligned and trailing edges of center turbulators from the left side set and trailing edges of the right side set are positioned downstream from the leading edges and radially outward from the longitudinal axis in generally opposite directions. A center gap may separate the right side set of center turbulators from the left side set of center turbulators. The outer turbulator may be formed from a set of outer turbulators having a first set of outer turbulators offset to a right side of the longitudinal axis and a second set of outer turbulators offset to a left side of the longitudinal axis, wherein an outer gap extending between leading edges of a radially adjacent outer turbulators is larger than the center gap. The right side set of center turbulators may be positioned at a same angle relative to the longitudinal axis as the right side set of outer turbulators, and the left side set of center turbulators may be positioned at a same angle relative to the longitudinal axis as the left side set of outer turbulators. 
     The trailing edge of the outer turbulator may be positioned laterally upstream from a leading edge of the center turbulator positioned immediately downstream. The trailing edge of the outer turbulator may be laterally aligned along the longitudinal axis with a leading edge of the center turbulator. In one embodiment, the set of outer turbulators may be offset to a right side of the longitudinal axis. In another embodiment, the set of outer turbulators may be offset to a left side of the longitudinal axis. In yet another embodiment, the set of outer turbulators may be formed from a first set of outer turbulators offset to a right side of the longitudinal axis and a second set of outer turbulators offset to a left side of the longitudinal axis. The outer turbulator may be positioned at a same angle with respect to the longitudinal axis as the center turbulator. A trailing edge of the center turbulator may terminate at a second longitudinal axis extending longitudinally in the at least one cooling channel and a leading edge of the at least one outer turbulator may extend from the second longitudinal axis, wherein the leading edge of the at least one outer turbulator is offset downstream from the trailing edge of the center turbulator. 
     During use, the cooling fluids may be passed into the cooling channel. The upstream corner of the center turbulator trips the boundary layer and creates turbulence. The turbulent cooling fluids form a vortex downstream of the turbulator that rolls along the length of the turbulator. However, the vortex rolls downstream and away from the turbulator by the incoming cooling fluids flowing over the turbulator. As the vortices propagate along the full length of the downstream side of center turbulators, the boundary layer becomes progressively more disturbed or thickened, but the outer turbulators disrupt such boundary layer formation, thereby preventing boundary layer growth that significantly reduces heat transfer augmentation. The vortex continues to increase in diameter as the vortex rolls away from the turbulator. The vortex may be disrupted by a downstream outer turbulator positioned downstream and radially outward from the center turbulator. The sets of center and outer turbulators effectively dissipate boundary layers of cooling fluids in cooling channels in industrial gas turbine engines. This unique vortex turbulator cooling arrangement formed by the sets of center and outer turbulators creates higher internal convective cooling potential for the turbine blade cooling channel, thus generating a high rate of internal convective heat transfer and efficient overall cooling system performance. This performance equates to a reduction in cooling demand and better turbine engine performance. 
     An advantage of this invention is that the turbine airfoil cooling system is configured to cool cooling channels and because of its configuration is particularly well suited to cool cooling channels in industrial gas turbine engines. 
     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 turbine airfoil having features according to the instant invention. 
         FIG. 2  is a cross-sectional view of the turbine airfoil shown in  FIG. 1  taken along line  2 - 2 . 
         FIG. 3  is a partial detailed view of the cooling system in the turbine airfoil shown in  FIG. 2  taken along line  3 - 3  in  FIG. 2 . 
         FIG. 4  is a partial detailed view of an alternative configuration of the cooling system in the turbine airfoil shown in  FIG. 2  taken along line  3 - 3  in  FIG. 2 . 
         FIG. 5  is a partial detailed view of another alternative configuration of the cooling system in the turbine airfoil shown in  FIG. 2  taken along line  3 - 3  in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIGS. 1-5 , this invention is directed to a turbine airfoil cooling system  10  configured to cool internal and external aspects of a turbine airfoil  12  usable in a turbine engine. In at least one embodiment, the turbine airfoil cooling system  10  may be configured to be included within a turbine blade, as shown in  FIGS. 1-5 . While the description below focuses on a cooling system  10  in a turbine blade  12 , the cooling system  10  may also be adapted to be used in a stationary turbine vane. The turbine airfoil cooling system  10  may be formed from a cooling system  10  having one or more cooling channels  16  having any appropriate configuration, as shown in  FIGS. 2-5 . The cooling channels  16  may include a plurality of turbulators  18  for creating vortices within the cooling channels  16  to increase the internal convective cooling potential of the cooling system, thereby increasing the overall performance of the cooling system  10 . 
     The turbine airfoil  12  has a generally elongated hollow airfoil  20  formed from an outer wall  22 . The generally elongated hollow airfoil  20  may have a leading edge  24 , a trailing edge  26 , a pressure side  28 , a suction side  30 , a root  32  at a first end  34  of the airfoil  20  and a tip  36  at a second end  38  opposite to the first end  34 . The generally elongated hollow airfoil  20  may have any appropriate configuration and may be formed from any appropriate material. The cooling system  10  may be positioned within interior aspects of the generally elongated hollow airfoil. One or more cooling channels  16  of the cooling system  10  may be positioned in the generally elongated hollow airfoil  20  and formed from an inner surface  40 . The inner surface  40  may define the cooling channel  16 . The cooling channel  16  may have any appropriate cross-sectional shape. The cooling channel  16  may be positioned at the leading edge  24 , the mid-chord section  42 , or the trailing edge  26 . 
     One or more center turbulators  44  may extend from the inner surface  40  into the cooling channel  16  to dissipate any film layer of cooling fluids. In at least one embodiment, there may exist a plurality of center turbulators  44  forming a set of center turbulators  44  that are positioned nonorthogonally and nonparallel relative to a longitudinal axis  46  of the cooling channel  16 . The set of center turbulators may be aligned along a longitudinal axis. One or more outer turbulators  48  may extend from the inner surface  40  into the cooling channel  16  and may be positioned nonorthogonally and nonparallel relative to the longitudinal axis  46  of the cooling channel  16 . 
     One or more of the turbulators  18  may have a height from the inner surface  40  of the cooling channel  16  that may be about one quarter or less of a distance between the pressure side  28  and the suction side  30 . In other embodiments, the height of the turbulators  18 , including the center and outer turbulators,  44 ,  48 , may be less than one sixteenth of the height of the distance between the pressure side  28  and the suction side  30 . The center turbulators  44  may be spaced from adjacent center turbulators  44  equally, in a repetitive pattern or randomly. The outer turbulators  48  may be spaced from adjacent outer turbulators  48  equally, in a repetitive pattern or randomly. 
     In embodiments shown in  FIGS. 3-5 , the set of center turbulators  44  may be formed from a right side set  50  of center turbulators  44  and a left side set  52  of center turbulators  44 . The right side set  50  of center turbulators  44  may extend nonorthogonally and nonparallel relative to the longitudinal axis  46  and may be a mirror image of the left side set  52  of center turbulators  44  such that leading edges  54  of center turbulators  44  from the right side set  50  and the left side set  52  are aligned and trailing edges  56  of center turbulators  44  from the left side set  52  and trailing edges  56  of the right side set  50  are positioned downstream from the leading edges  54  and radially outward from the longitudinal axis  46  in generally opposite directions. The right side set  50  of center turbulators  44  may be positioned nonorthogonally and nonparallel relative to the left side set  52  of center turbulators  44 . In another embodiment, the right side set  50  of center turbulators  44  may be positioned orthogonally relative to the left side set  52  of center turbulators  44 . A center gap  58  may separate the right side set  50  of center turbulators  44  from the left side set  52  of center turbulators  44 . The center gap  58  between adjacent center turbulators  44  may be the same distance or may vary. The center gap  58  may have a distance less than one quarter of a length of a center turbulator  44 . 
     One or more outer turbulators  48  may extend from the inner surface  40  into the cooling channel  16  and may be positioned nonorthogonally and nonparallel relative to the longitudinal axis  46  of the cooling channel  16 . In one embodiment, a plurality of outer turbulators  48  may be positioned in the cooling channel  16 . The outer turbulator  48  may have a leading edge  60  that is positioned radially outward from the longitudinal axis  46  and a trailing edge  62  that is positioned radially outward further from the longitudinal axis  46  than a trailing edge  56  of the center turbulators  44 . The outer turbulator  48  may be offset in a downstream direction from at least one of the center turbulators  44 . The trailing edge  62  of the outer turbulator  48  may be positioned laterally upstream from a leading edge  54  of the center turbulator  44  positioned immediately downstream. The trailing edge  62  of the outer turbulator  48  may be laterally aligned along the longitudinal axis  46  with a leading edge  54  of the center turbulator  44 . 
     As shown in  FIG. 4 , the plurality of outer turbulators  48  may form a set of outer turbulators  48  offset to a right side of the longitudinal axis  46  when viewed downstream along the longitudinal axis  46 . In another embodiment, as shown in  FIG. 5 , the plurality of outer turbulators  48  may form a set of outer turbulators  48  offset to a left side of the longitudinal axis  46  when viewed downstream along the longitudinal axis  46 . In yet another embodiment, as shown in  FIG. 3 , the set of outer turbulators  48  may be formed from a first set  64 , referred to as a right side set, of outer turbulators  48  offset to a right side of the longitudinal axis  46  and a second set  66 , referred to as a left side set, of outer turbulators  48  offset to a left side of the longitudinal axis  46 . The outer turbulator  48  may be positioned at a same angle with respect to the longitudinal axis  46  as the center turbulator  44 . A trailing edge of the center turbulator  44  may terminate at a second longitudinal axis  68  extending longitudinally in the cooling channel  16  and a leading edge  60  of the outer turbulator  48  may extend from the second longitudinal axis  68 . The leading edge  60  of the outer turbulator  48  may be offset downstream from the trailing edge  56  of the center turbulator  44 . 
     As shown in  FIG. 3 , an outer gap  70  extending between leading edges  60  of a radially adjacent outer turbulators  48  may be larger than the center gap  58 . As such, the outer turbulators  48  are positioned in a radial direction further in a radial direction from the longitudinal axis than the center turbulators  44 . The right side set  50  of center turbulators  44  may be positioned at a same angle relative to the longitudinal axis  46  as the right side set  64  of outer turbulators  48 . The left side set  52  of center turbulators  44  may be positioned at a same angle relative to the longitudinal axis  46  as the left side set  66  of outer turbulators  48 . 
     During use, the cooling fluids may be passed into the cooling channel  16 . The upstream corner  72  of the leading edge  54  of the center turbulator  44  trips the boundary layer and creates turbulence. The turbulent cooling fluids form a vortex downstream of the turbulator  44  that rolls along the length of the turbulator  44 . However, the vortex rolls downstream and away from the turbulator  44  by the incoming cooling fluids flowing over the turbulator  18 . As the vortices propagate along the full length of the downstream side of center turbulators  44 , the boundary layer becomes progressively more disturbed or thickened, but the outer turbulators  48  disrupt such boundary layer formation, thereby preventing boundary layer growth that significantly reduces heat transfer augmentation. The vortex continues to increase in diameter as the vortex rolls away from the turbulator  44 . The vortex may be disrupted by a downstream outer turbulator  48  positioned downstream and radially outward from the center turbulator  44 . The sets of center and outer turbulators  44 ,  48  effectively dissipate convective cooling layers in cooling channels  16  in industrial gas turbine engines. This unique vortex turbulator cooling arrangement formed by the sets of center and outer turbulators,  44 ,  48  creates higher internal convective cooling potential for the turbine blade cooling channel  16 , thus generating a high rate of internal convective heat transfer and efficient overall cooling system performance. This performance equates to a reduction in cooling demand and better turbine engine performance. 
     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.