Patent Publication Number: US-8985940-B2

Title: Turbine cooling apparatus

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to gas turbine engine cooling, and more particularly to the cooling of turbine blades in a gas turbine engine (GTE). 
     BACKGROUND 
     GTEs produce power by extracting energy from a flow of hot gas produced by combustion of fuel in a stream of compressed air. In general, turbine engines have an upstream air compressor coupled to a downstream turbine with a combustion chamber (“combustor”) in between. Energy is released when a mixture of compressed air and fuel is burned in the combustor. In a typical turbine engine, one or more fuel injectors direct a liquid or gaseous hydrocarbon fuel into the combustor for combustion. The resulting hot gases are directed over blades of the turbine to spin the turbine and produce mechanical power. 
     High performance GTEs include cooling passages and cooling fluid to improve reliability and cycle life of individual components within the GTE. For example, in cooling the turbine section, cooling passages are provided within the turbine blades to direct a cooling fluid therethrough. Conventionally, a portion of the compressed air is bled from the air compressor to cool components such as the turbine blades. The amount of air bled from the air compressor, however, is limited so that a sufficient amount of compressed air is available for engine combustion to perform useful work. 
     U.S. Pat. No. 7,137,784 to Hall et al. (the &#39;784 patent) describes a thermally loaded component having at least one cooling passage for the flow of a cooling fluid therethrough. According to the &#39;784 patent, a blade or vane of a turbomachine may incorporate diverter blades to divert cooling fluid into cooling passages. The diverter blades include first and second diverter parts spaced at a distance from one another over a height of a cooling passage. 
     SUMMARY 
     In one aspect, a turbine blade for a gas turbine engine is disclosed. The turbine blade can include at least one internal cooling path, and an internal turning vane disposed in the at least one internal cooling path. The internal vane can include a central portion, a first leg extending in a first direction from the central portion, and a second leg extending in a second direction from the central portion. The central portion can have a thickness greater than a thickness of the first leg or a thickness of the second leg. is disclosed. 
     In another aspect, a turbine blade for a gas turbine engine is disclosed. The turbine blade can include at least one internal cooling path, and at least one vane disposed in the at least one internal cooling path. The at least one vane can include a central portion, and a leg extending from the central portion. The central portion can have a thickness greater than a thickness of the leg. 
     In yet another aspect, a turbine blade for a gas turbine engine is disclosed. The turbine blade can include an internal cooling path, a first vane disposed at a first location in the cooling path, and a second vane disposed at a second location in the cooling path downstream from the first location. The first and second vane can each taper from a central thickness to a first thickness, and from the central thickness to a second thickness. The first thickness can be disposed upstream from the central thickness in the cooling path, and the central thickness can be disposed upstream from the second thickness in the cooling path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of a portion of a turbine section of a gas turbine engine; 
         FIG. 2  is an enlarged sectional view of a turbine blade taken along lines  2 - 2  of  FIG. 1 ; 
         FIG. 3  is an enlarged sectional view of the turbine blade of  FIG. 2  taken alone line  3 - 3 ; 
         FIG. 4  is a detailed view of a general vane of the present disclosure; and 
         FIG. 5  is an alternative embodiment of a general vane of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a sectional view of a portion of a GTE, specifically a turbine section  10  of the GTE. The turbine section  10  includes a first stage turbine assembly  12  disposed partially within a first stage shroud assembly  20 . 
     During operation, a cooling fluid, designated by the arrows  14 , flows from the compressor section (not shown) to the turbine section  10 . Furthermore, each of the combustion chambers (not shown) are radially disposed in a spaced apart relationship with respect to each other, and have a space through which the cooling fluid  14  flows to the turbine section  10 . The turbine section  10  further includes a support structure  15  having a fluid flow channel  16  through which the cooling fluid  14  flows. 
     The first stage turbine assembly  12  includes a rotor assembly  18  radially aligned with the shroud assembly  20 . The rotor assembly  18  may be of a conventional design including a plurality of turbine blades  22 . The turbine blades  22  may be made from any appropriate materials, for example metals or ceramics. The rotor assembly  18  further includes a disc  24  having a plurality of circumferentially arranged root retention slots  30 . The plurality of turbine blades  22  are replaceably mounted within the disc  24 . Each of the plurality of blades  22  may include a first end  26  having a root section  28  extending therefrom which engages with one of the corresponding root retention slots  30 . The first end  26  may be spaced away from a bottom of the root retention slot  32  in the rotor assembly  18  to form a cooling fluid inlet opening  34  configured to receive cooling fluid  14 . Each turbine blade  22  may further include a platform section  36  disposed radially outward from a periphery of the disc  24  and the root section  28 . Additionally, an airfoil  38  may extend radially outward from the platform section  36 . Each of the plurality of turbine blades  22  may include a second end  40 , or tip, positioned opposite the first end  26  and adjacent the shroud  20 . 
       FIG. 2  shows an enlarged sectional view of a turbine blade  22  taken along lines  2 - 2  of  FIG. 1 . Each of the plurality of turbine blades  22  includes a leading edge  42 , and a trailing edge  44  positioned opposite the leading edge  42  ( FIGS. 2 and 3 ). Interposed the leading edge  42  and the trailing edge  44  is a suction, or convex, side  96 , and a pressure, or concave, side  98  of the turbine blade  22 . Each of the plurality of turbine blades  22  may have a generally hollow configuration forming a peripheral wall  50 , which, in some embodiments, may have a uniform thickness. 
     As shown in  FIGS. 2 and 3 , an arrangement for internally cooling each of the turbine blades  22  is provided. The arrangement for internal cooling may include a pair of cooling paths  64  and  76  ( FIG. 3 ), positioned within the peripheral wall  50 , and separated from one another. The cooling paths  64  and  76  may have a rectangular cross-sectional shape through which cooling fluid  14  can flow. In other embodiments, however, the cross-sectional shape of the cooling paths  64  and  76  may be, for example, circular or oval. Any number of cooling paths could be used. The cooling paths  64  and  76  may be formed by a plurality of wall members, for example first, second, third, fourth, and fifth wall members  70 ,  80 ,  92 ,  94 , and  110 , respectively, as described in more detail below ( FIG. 3 ). Each of the wall members  70 ,  80 ,  92 ,  94 , and  110  can be connected to, and in some instances formed integrally with, the peripheral wall  50  at both the suction side  96  and the pressure side  98  of the turbine blade  22 . 
     Referring to  FIG. 3 , the first and second cooling paths  64  and  76  positioned within the peripheral wall  50  are interposed the leading edge  42  and the trailing edge  44  of each of the blades  22 . The first cooling path  64  includes a first passage  56  extending between the first end  26  and the second end  40  of the turbine blade  22 . The first passage  56  is interposed the leading edge  42  and a second passage  82  by the second wall member  80 . Included in the second cooling path  76  is the second passage  82 , which extends between the first end  26  and the second end  40  of the turbine blade  22 . The second passage  82  is interposed the first passage  56  and a third passage  86  by the second wall member  80  and the third wall member  92  ( FIG. 3 ). The second cooling path  76  further includes a third passage  86  which extends at least partially between the first end  26  and the second end  40  of the turbine blade  22 . The third passage  86  is interposed the second passage  82  and a second cooling path outlet  90  by the third wall member  92  and the fourth wall member  94 . As shown in  FIG. 3 , the second cooling path  76  can have an “S” or serpentine shape through the interior of the turbine blade  22 . 
     As shown in  FIG. 3 , the first cooling path  64  can include a horizontal passage  68  disposed near the second end  40  of the blade  22 . The second cooling path  76  can include an top turn  84  and a bottom turn  88 . Like the passages  56 ,  82  and  86 , the horizontal passage  68 , the top turn  84 , and the bottom turn  88  can be formed by the second end  40  of the blade  22  and the wall members  70 ,  80 ,  92 , and  94 . As illustrated in  FIG. 3 , a plurality of outlet flow guides  112  can be disposed at the second cooling path outlet opening  90 . The outlet flow guides  112  can have any shape, for example, a rectangular cross-sectional shape as shown in  FIG. 3 . Furthermore, the outlet flow guides  112  in the second cooling path  76  can be evenly spaced along the second cooling path outlet opening  90 . 
     Referring again to  FIGS. 2 and 3 , the turbine blade  22  includes vanes  100  and  200  disposed in the second cooling path  76  of the turbine blade  22 . Each vane  100  and  200  may be referred to herein as a turning vane, a non-uniformly shaped vane, a triangle-like element, a delta-wing, a flow directing portion, a flow guide element, or the like. The term “non-uniform” or “non-uniformly shaped” as used herein refers to a vane having a varying thickness, as shown, for example, in  FIG. 4 . The vanes  100  and  200  may be connected to the peripheral wall  50  of the turbine blade  22 . In some instances, as shown in  FIG. 2 , the vanes  100  and  200  may be integral with the peripheral wall  50 .  FIG. 2  shows each of the vanes  100  and  200  extending from the peripheral wall  50  at the suction side  96  of the turbine blade  22  to the peripheral wall  50  at the pressure side  98 . The vanes  100  and  200  may be referred to as solid or unbroken, or extending continuously or in an unbroken manner between the suction side  96  and the pressure side  98 . The vanes  100  and  200  may also be said to connect the suction side  96  and the pressure side  98  of the turbine blade  22 . As shown in  FIG. 2 , and with reference to  FIG. 3 , in some embodiments, each of the vanes  100  and  200  may have a constant or substantially constant width from the suction side  96  to the pressure side  98 . 
     The vanes  100  and  200  are shown in the second cooling path  76  of the turbine blade  22 . The first vane  100  can be disposed at a location adjacent a first corner  104  and an inner side  108  of the first wall member  70 , such that the first vane  100  is positioned between the second passage  82  and the top turn  84 . The first vane  100  can also be referred to as being in a corner of either the second passage  82  or the top turn  84 . Additionally, the first vane  100  can be referred to as being downstream of the second passage  82 , or upstream of the top turn  84 . As shown in  FIG. 3 , the first corner  104  is on an outer side of a turn in the second cooling path  76 . 
     The second vane  200  can be disposed at a location near to or adjacent a second corner  106  and the inner side  108  of the first wall member  70 , such that the second vane  200  is positioned between the top turn  84  and the third passage  86 . The second vane  200  can also be referred to as being in a corner of either the top turn  84  or the third passage  86 . Additionally, the second vane  200  can be referred to as being downstream of the top turn  84  or upstream of the third passage  86 . As shown in  FIG. 3 , the second corner  106  is on an outer side of another turn in the second cooling path  76 . Thus, the first and second vanes  100  and  200 , respectively, can be located closer to an outer side than an inner side of a corresponding turn in the second cooling path  76 . 
     As shown in  FIG. 3 , the first corner  104  is at a location where the second wall member  80  meets the first wall member  70 , and the second corner  106  is at a location where the first wall member  70  meets the fourth wall member  94 . The first vane  100  can be positioned between the first corner  104  and an end  102  of the third wall member  92 , and the second vane  200  can be positioned between the second corner  106  and the end  102 . Each corner  104  and  106  may be configured as a square-shaped corner or a square-shaped turn. 
     Each of the turning vanes  100  and  200  can have a greatest or widest cross-sectional area at the portion of the vane  100  or  200  closest to the corners  104  and  106 , respectively. As shown in  FIG. 3 , each turning vane  100  and  200  has inner and outer curved sides, also described below with respect to  FIG. 4 , where the outer curved side of each of the turning vanes  100  and  200  is contoured to match the nearby or adjacent side or corner of the cooling passage. 
     Each vane  100  and  200  can be sized according to the geometry of the passage in which the vane is disposed. For example, as shown in  FIG. 3 , the third passage  86  is wider than the second passage  82 . Accordingly, the vane  100 , which is disposed in the second passage  82 , can be made smaller than the vane  200 , which is disposed in the third passage  86 . Thus, for a larger, for instance a wider, fluid passage within a turbine blade, a larger vane may be provided, and vice versa. 
       FIG. 4  shows a detailed view of a triangle-like vane  400  of the present disclosure. The vane  400 , which can be referred to herein as a general vane, represents a vane like the vanes  100  and  200  described above. Thus, the following description of vane  400  in  FIG. 4  applies to the vanes  100  and  200  of  FIGS. 2 and 3 . 
     As shown in  FIG. 4 , a vane  400  includes a first leg  416  having a first thickness  401  and a second leg  418  having a second thickness  402 , where the first and second thicknesses  401  and  402  can be equal. The vane  400  includes a central portion  420  having a third or central thickness  403  that is greater than the first and second thicknesses  401  and  402 , respectively. As shown in  FIGS. 3 and 4 , the central portion can be disposed adjacent the first corner  104  or the second corner  106  of the second cooling path  76 . The vane  400  has a geometry that tapers or curves from the third thickness  403  down to the first thickness  401  and the second thickness  402 , such that the cross-sectional shape of the vane  400  is non-uniform. It can also be said that the vane  400  has a geometry that tapers or curves down from the third or central thickness  403  to the first thickness  401  and/or the second thickness  402 . In some instances, the vane  400  can be symmetric about a line through the third thickness  403 . In other instances, the vane  400  could be asymmetric. The location of the third thickness  403  is the thickest portion of the vane  400  in the cross-sectional direction of the vane  400  shown in  FIG. 4 . The vane  400  also includes a first width  404  and a second width  406 , where the first and second widths  404  and  406  can be equal. Additionally, the vane  400  has an outer curved side  408  and an inner curved side  412  opposite the outer curved side  408 , where the outer curved side  408  forms an outer side of the central portion  420 . The outer curved side  408  may be referred to as a convex portion having a radius of curvature, and the inner curved side  412  may be referred to as a concave portion having another radius of curvature. As shown in  FIG. 4 , the radius of curvature of the outer curved side  408  may be smaller than the radius of curvature of the inner curved side  412 . The vane also includes planar portions  409  and  411  extending from the outer curved side  408 . The planar portion  409  forms an outer side of the first leg  416 , and the planar portion  411  forms an outer side of the second leg  418 . The inner curved side  412  forms an inner side of the first leg  416 , the central portion  420 , and the second leg  418 . The vane  400  also includes a first tip  414  and a second tip  410 , where the first and second tips  414  and  410  may have the same shape, for example, a rounded end shape. In some instances, a vane having only one leg could be provided, where the single leg could be similar to leg  416  or  418  of vane  400 . 
     As mentioned above, because the size of the vane  400  increases with an increase in size of the fluid passage in which the vane is disposed, each of the dimensions, that is, the thicknesses  401 ,  402 , and  403 , and the widths  404  and  406 , can also increase with an increase in size of the fluid passage. In other embodiments, however, the first thickness  401  and the second thickness  402 , for example, may be held at a constant dimension regardless of the size of the fluid passage in which the vane  400  is disposed. 
     Although the vanes  100  and  200  of  FIG. 3  exhibit the shape of the general vane  400  shown in  FIG. 4 , the vanes  100  and  200  may be connected. As shown in the alternative embodiment in  FIG. 5 , for example, the vanes  100  and  200  may be connected, through the top turn  84  for instance ( FIG. 3 ), to form a single vane  500 . The single vane  500  may be referred to herein as a “full delta-shaped turning vane.” 
     INDUSTRIAL APPLICABILITY 
     The above-mentioned apparatus, while being described as an apparatus for cooling a turbine blade, can be applied to any other blade or airfoil requiring temperature regulation. For example, turbine nozzles in a GTE could incorporate the cooling apparatus described above. Moreover, the disclosed cooling apparatus is not limited to GTE industry application. The above-described principal, that is, using non-uniformly shaped vanes for directing flow of a cooling fluid, could be applied to other applications and industries requiring temperature regulation of a working component. 
     The following operation will be directed to the first stage turbine assembly  12 ; however, the cooling operation of other airfoils and stages (turbine blades or nozzles) could be similar. 
     A portion of the compressed fluid from the compressor section of the GTE is bled from the compressor section and forms the cooling fluid  14  used to cool the first stage turbine blades  22 . The compressed fluid exits the compressor section, flows through an internal passage of a combustor discharge plenum, and enters into a portion of the fluid flow channel  16  as cooling fluid  14 . The flow of cooling fluid  14  is used to cool and prevent ingestion of hot gases into the internal components of the GTE. For example, the air bled from the compressor section flows into a compressor discharge plenum, through spaces between a plurality of combustion chambers, and into the fluid flow channel  16  in the support structure  15  ( FIG. 1 ). After passing through the fluid flow channel  16  shown in  FIG. 1 , the cooling fluid enters the cooling fluid inlet opening  34  between the first end  26  of the turbine blade  22  and the bottom  32  of the root retention slot  30  in the disc  24 . The cooling fluid inlet opening  34  is fluidly connected to the first and second cooling paths  64  and  76 , respectively, in the interior of the turbine blade  22  ( FIG. 3 ). 
     As shown in  FIG. 3 , a first portion of the cooling fluid  14 , after having passed through the cooling fluid inlet opening  34  ( FIG. 1 ), enters the first cooling path  64 . The cooling fluid  14  enters the first cooling path inlet opening  66  from the cooling fluid inlet opening  34 , and travels radially along the first passage  56 , absorbing heat from the peripheral wall  50  and the second wall member  80 . The cooling fluid flows from the first passage  56  to the horizontal passage  68  and out of the turbine blade  22  through the first cooling path outlet  74 . 
     A second portion of the cooling fluid  14 , after having passed through the cooling fluid inlet opening  34  ( FIG. 1 ), enters the second cooling path  76 . For example, cooling fluid  14  enters the second cooling path inlet opening  78  from the cooling fluid inlet opening  34 , and travels radially along the second passage  82 , absorbing heat from the second wall member  80  and the third wall member  92  before entering the top turn  84 . 
     As the cooling fluid  14  flows from the second passage  82  to the top turn  84 , the fluid  14  flows around the first vane  100  disposed in the flow path. As shown in  FIG. 3 , the cooling fluid  14  flows on both sides of the first vane  100 , and in close proximity to the first corner  104  and the end  102  of the third wall member  92 . With the first vane  100  disposed in the fluid flow path, the cooling fluid  14  fills the space of the second cooling path  76  as the fluid  14  flows from the second passage  82  to the top turn  84 . 
     After passing by the first vane  100 , the cooling fluid  14  then flows around the second vane  200  downstream of the first vane  100 . As shown in  FIG. 3 , the cooling fluid  14  flows on both sides of the second vane  200 , and in close proximity to the second corner  106  and the end  102  of the third wall member  92 . With the second vane  200  disposed in the fluid flow path, the cooling fluid  14  fills the space of the second cooling path  76  as the fluid  14  flows from the top turn  84  to the third passage  86 . 
     As the cooling fluid  14  flows over each vane  100  and  200 , the cooling fluid  14  flows from the first leg  416  to the second leg  418 , passing by the central portion  410  disposed between the first and second legs  416  and  418 . Therefore, the first leg  416  can be said to be disposed upstream of the central portion  420  and the second leg  418 , and the central portion  420  can be said to be disposed upstream of the second leg  418 . Thus, the first thickness  401  is disposed upstream from the central thickness  403 , and the central thickness  403  is disposed upstream from the second thickness  402 . The first leg  416  or the first thickness  401  may be referred to as the most upstream portion of either vane  100  or  200 , and the second leg  418  or the second thickness  402  may be referred to as the most downstream portion of either vane  100  or  200 . 
     After passing over the first and second vanes  100  and  200 , respectively, the cooling fluid  14  enters the third passage  86 , where additional heat can be absorbed from the third wall member  92  and the fourth wall member  94  before entering the bottom turn  88 . After passing through the bottom turn  88 , the cooling fluid exits the second cooling path  76  through the second cooling path outlet opening  90  along the trailing edge  44  to be mixed with the combustion gases. 
     In some instances, the turbine blade  22  may be manufactured by a known casting process, for example investment casting. During investment casting, the blade  22  can be formed having a partially vacant internal area including the cooling paths  64  and  76  described above to allow for the flow of cooling fluid. Investment casting the turbine blade  22  forms the vanes  100  and  200  at the time of casting. Because the vanes  100  and  200  are cast with the blade  22 , the vanes  100  and  200  are integral to the peripheral wall  50  of the turbine blade  22 . As described above with respect to  FIG. 2 , the vanes  100  and  200  can be formed integrally with the peripheral wall  50  of the suction side  96  and the pressure side  98  of the turbine blade  22 . In some instances, the casting material for the blade  22 , and therefore also for the vanes  100  and  200 , may be metal. In some cases, the turbine blade may be cast as a single crystal, or monocrystalline solid, and may be made of a superalloy. 
     Typical arrangements for directing fluid through a turbine blade include passages extending through an interior of the blade. While the passages generally include one or more turns or corners through which the fluid is directed, these turns can cause undesired pressure losses. The turns and corners are susceptible to flow separation, that is, dead-zones or vacant space in a flow path without fluid flow. In addition to pressure losses, using larger passages for cooling can also result in flow separation from the increased cross sectional area of the passages. When the fluid flows at a high velocity through the passages, there is often insufficient time for flow expansion or diffusion, which results in flow separation, or chaos, within the turbine blade. When the flow of cooling fluid separates within the passages, the cooling fluid does not fill the space of the passages, and therefore the heat transfer coefficient may decrease. With a decrease in the heat transfer coefficient, there is a risk of overheating and problems related to premature wear of the turbine blades, which can prevent overall efficient operation of the GTE. 
     The above-described apparatus provides more efficient use of the cooling air bled from the compressor section of a GTE in order to facilitate increased component life and efficiency of the GTE. Providing the vanes as described can reduce the pressure drop and flow separation in the cooling paths, thereby increasing the heat transfer coefficient in the turns of the cooling paths and also downstream of the turns. Increasing the heat transfer coefficient in this manner can cause more effective cooling of the turbine blade, which reduces the temperature of the metal of the blade. Reducing the blade temperature reduces stress imparted on the blade, which increases the blade service life. Increasing the blade service life allows the turbine blades to be used for longer periods, thus reducing the frequency of necessary turbine section inspections for a given GTE. 
     The vanes of the disclosed apparatus are particularly suited to improve turbine blade cooling because they exhibit a non-uniform shape. Providing the described vanes reduces the cross-sectional area of the flow passages through which the cooling fluid can flow, which thereby reduces flow separation and chaos, that is, dead-zones are minimized or eliminated. The delta-wing or triangle-like shaped vanes described above facilitate cooling by ensuring that the internal flow passages of the turbine blade are filled with cooling fluid. A larger vane can be provided for a larger cooling passage, and a smaller vane can be provided for a smaller cooling passage, thereby ensuring that there are few or no dead-zones for a passage of a given size. The shape of the vanes helps guide the flow of cooling fluid and push the flow toward the areas usually susceptible to flow separation, that is, the turns and corners of the flow passages. For example, as shown in  FIG. 3 , the vane  100  helps to push the flow of cooling fluid  14  into the first corner  104 , the vane  200  helps to push the flow of cooling fluid  14  into the second corner  106 , and the vanes  100  and  200  both help to push the flow of cooling fluid  14  towards the end  102  of the third wall member  92 . Thus, due to the non-uniform shape of the vanes, pressure losses in the cooling passages are prevented, and cooling fluid flows through the entire space of the flow passages, including the corners and curves where dead-zones typically exist. Therefore, blade cooling efficiency can be increased, resulting in the convenience and cost savings from an increased blade service life. 
     In addition to improving blade cooling efficiency, the integration of the vanes with the peripheral wall of the turbine blade, formed during casting the vanes with the rest of the turbine blade, provides the simplicity of fewer separate parts to the overall turbine blade structure. Because the vanes are integrally formed via investment casting, complexity is reduced, as is any risk of the vanes detaching from the peripheral walls of the turbine blade and hindering GTE performance. Thus, casting the vanes in the manner described facilitates production of durable and reliable turbine blades. 
     The foregoing description relates to an exemplary embodiment of the turbine cooling apparatus. As an alternative, one or both of the vanes  100  and  200  could be disposed in either the first cooling path  64  or the second cooling path  76 , or in any other cooling path formed within the turbine blade  22 . Additionally, although only two vanes  100  and  200  are shown in  FIGS. 2 and 3 , any number of vanes could be provided in the turbine blade  22 . Furthermore, although  FIG. 3  shows turning vanes  100  and  200  disposed in square-shaped turns of cooling passages, a vane can be disposed at a turn in a fluid passage that is not square-shaped. For example, a vane may be provided in a cooling passage having an obtuse or an acute angled turn. In addition to including a vane in a cooling path of the turbine blade  22 , the turbine blade  22  may also include a turbulating element for imparting turbulence into the flow of cooling fluid  14 . A turbulating element may be, for example, a radially disposed strip in a passage of one or both of the first cooling path  64  and the second cooling path  76 . A turbulating element may further enhance the internal heat transfer coefficient for effective blade cooling and prevention of overheating and premature wear. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed turbine cooling system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system and method. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.