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 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 airfoils (such as turbine vanes and blades) to high temperatures. As a result, turbine airfoils must be made of materials capable of withstanding such high temperatures, or must include cooling features to enable the component to survive in an environment which exceeds the capability of the material. As an example, typical airfoils may include internal cooling systems for reducing the temperature of the airfoils. Such typical internal cooling systems, however, may be deficient.

SUMMARY OF THE INVENTION

An airfoil for a gas turbine engine in which the airfoil includes an internal cooling system formed in part by an interrupted internal wall that distributes mechanical loads and that enables formation of inactive cavities that increase efficiency of the cooling system is disclosed. The interrupted internal wall may include a plurality of unconnected segments. The cooling system may include a first inactive cavity positioned in-between a first set of two successive unconnected segments. The first inactive cavity may be formed by a first portion of the plurality of ribs. Furthermore, the first portion of the plurality of ribs may include first and second ribs that are each connected to a first unconnected segment of the first set of two successive unconnected segments, and may further include third and fourth ribs that are each connected to a second unconnected segment of the first set of two successive unconnected segments.

In at least one embodiment, a turbine airfoil may include a generally elongated hollow airfoil formed from an outer wall, and may have a leading edge, a trailing edge, a pressure side, and a suction side. The turbine airfoil may further include a cooling system positioned within an interior portion of the generally elongated hollow airfoil. The cooling system may be formed by the outer wall, an interrupted internal wall, and a plurality of ribs positioned in-between the outer wall and the interrupted internal wall. The plurality of ribs may connect the interrupted internal wall to the outer wall. The interrupted internal wall may include a plurality of unconnected segments. The turbine airfoil may be a turbine blade, or a turbine vane.

The cooling system may include a first inactive cavity positioned in-between a first set of two successive unconnected segments of the plurality of unconnected segments, and the first inactive cavity may be isolated from the outer wall. The cooling system may also include a second inactive cavity positioned in-between a second set of two successive unconnected segments of the plurality of unconnected segments. Furthermore, the second inactive cavity may be isolated from the outer wall.

The first inactive cavity may be formed by a first portion of the plurality of ribs. Each rib of the first portion of the plurality of ribs may be connected at an angle to at least one of the unconnected segments of the first set of two successive

unconnected segments, and the angle may be between 95 degrees and 150 degrees. The first portion of the plurality of ribs may include a first rib and a second rib that are each connected to a first unconnected segment of the first set of two successive unconnected segments. Also, the first portion of the plurality of ribs may further include a third rib and a fourth rib that are each connected to a second unconnected segment of the first set of two successive unconnected segments. Additionally, the first rib may be connected to the third rib and the second rib may be connected to the fourth rib.

In one embodiment, a first unconnected segment of the plurality of unconnected segments may be connected to each of a first rib, a second rib, a third rib, and a fourth rib of the plurality of ribs. The first rib and the third rib may connect the first unconnected segment to the suction side of the outer wall, and the second rib and the fourth rib may connect the first unconnected segment to the pressure side of the outer wall.

Cooling fluids may flow through the cooling system. In one embodiment, the cooling system may include an aft flowing serpentine cooling channel and a forward flowing serpentine cooling channel. The aft flowing serpentine cooling channel may be a five-pass aft flowing serpentine cooling channel.

In one embodiment, an advantage of the internal cooling system formed by the interrupted internal wall is that the interrupted internal wall may more easily deform relative to the outer wall. As such, the interrupted internal wall may mitigate thermal/mechanical stresses caused by the outer wall being heated to a higher temperature than inner portions of the airfoil.

A further advantage of the internal cooling system formed by the interrupted internal wall is that the interrupted internal wall may reduce the cross-sectional area of the cooling cavities by providing one or more inactive cavities. As such, the cooling fluids may more efficiently cool the airfoil, even for low flow designs.

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.

Figure 1 is a perspective view of a turbine airfoil according to one

embodiment. Figure 2 is a cross-sectional view of an example of the turbine airfoil shown in Figure 1 taken along section line 2-2.

Figure 3 is a cross-sectional view of another example of the turbine airfoil shown in Figure 1 taken along section line 2-2.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Figures 1-3, an airfoil 12 for a gas turbine engine in which the airfoil 12 includes an internal cooling system 10 formed in part by an interrupted internal wall 54 that distributes mechanical loads and that enables formation of inactive cavities 68 that increase efficiency of the cooling system 10 is disclosed. The interrupted internal wall 54 may include a plurality of unconnected segments 62. The cooling system 10 may include a first inactive cavity 68 positioned in-between a first set of two successive unconnected segments 62. The first inactive cavity 68 may be formed by a first portion of the plurality of ribs 58. Furthermore, the first portion of the plurality of ribs 58 may include first and second ribs 58 that are each connected to a first unconnected segment 62 of the first set of two successive unconnected segments 62, and may further include third and fourth ribs 58 that are each connected to a second unconnected segment 62 of the first set of two successive unconnected segments 62.

Typically, a turbine airfoil (such as a turbine blade or a turbine vane) may be cooled by an internal cooling system that allows cooling fluids to pass through the turbine airfoil, cooling the outer wall of the turbine airfoil. Such internal cooling systems may be typically formed by a continuous internal wall that is parallel to a camber line of the turbine airfoil. However, this typical internal wall may be deficient because it may be subject to high stresses which may cause it to fail. For example, a typical internal wall may have a lower temperature than the outer wall of the airfoil. This temperature difference may cause the outer wall to deform at a different rate than the typical internal wall, which may subject the internal wall to high stress, and possible failure. Contrary to this, airfoil 12 of Figures 1 -3 may include an internal cooling system 10 that provides various advantages. For example, in one embodiment, an advantage of the internal cooling system 10 formed by the interrupted internal wall 54 is that the interrupted internal wall 54 may more easily deform relative to the outer wall 38. As such, the interrupted internal wall 54 may mitigate thermal/mechanical stresses caused by the outer wall 38 being heated to a higher temperature than inner portions of the airfoil 12. As another example, in one embodiment, a further advantage of the internal cooling system 10 formed by the interrupted internal wall 54 is that the interrupted internal wall 54 may reduce the cross-sectional area of the cooling cavities of the cooling system 10 by providing one or more inactive cavities 68. As such, the cooling fluids may more efficiently cool the airfoil, even for low flow designs.

Figure 1 illustrates an turbine airfoil 12 according to one embodiment. The airfoil 12 may be any type of turbine airfoil. For example, the airfoil 12 may be a turbine blade, a turbine vane, or any other turbine airfoil. As illustrated, the airfoil 12 is a turbine blade for a gas turbine engine. The airfoil 12 may include a generally elongated hollow airfoil 32 formed from an outer wall 38 adapted for use, for example, in a first stage of an axial flow turbine engine. The generally elongated hollow airfoil 32 may have a leading edge 46, a trailing edge 48, a generally concave shaped portion forming pressure side 40, and a generally convex shaped portion forming suction side 42. As illustrated, the generally elongated hollow airfoil 32 may be coupled to a root 34 at a platform 36. The root 34 may couple the airfoil 12 (such as a turbine blade) to a disc (not shown) of the turbine engine. In other

embodiments, the airfoil may be a turbine vane with a first end coupled to the inner diameter of the turbine section of the turbine engine and a second end coupled to the outer diameter of the turbine section of the turbine engine.

A cavity 14 (shown in Figure 2) may be positioned in an inner portion of the airfoil 12 for directing one or more gases, which may include air received from a compressor (not shown), through the airfoil 12 and out one or more exhaust orifices 44 in the airfoil 12 to reduce the temperature of the airfoil 12. As shown in Figure 1 , the exhaust orifices 44 may be positioned in the leading edge 46, the trailing edge 48, the tip 50 in close proximity to the leading and trailing edges 46, 48, or any combination thereof, and have various configurations. The leading edge 46 may include a plurality of orifices 44 that collectively form a showerhead for cooling the leading edge 46 of the airfoil 12. Additionally, although Figure 1 illustrates orifices 44 as positioned at particular locations, the orifices 44 may be positioned anywhere along pressure side 40 and/or suction side 42. The cavity 14 may be arranged in various configurations and is not limited to a particular flow path.

A cooling system 10 may be located in cavity 14, as shown in Figure 2. As such, the cooling system 10 may be positioned within an interior portion of the generally elongated hollow airfoil 32. The cooling system 10 may be formed by a combination of the outer wall 38, an interrupted internal wall 54, and a plurality of ribs 58 positioned in-between the outer wall 38 and the interrupted internal wall 54. The interrupted internal wall 54 may include a plurality of unconnected segments 62. The interrupted internal wall 54 may have any number of unconnected segments 62. For example, the interrupted internal wall 54 may have two unconnected segments 62, three unconnected segments 62, four unconnected segments 62, six unconnected segments 62, eight unconnected segments 62, or any other number of unconnected segments 62. In one embodiment, the interrupted internal wall 54 may only include unconnected segments 62. In a further embodiment, the interrupted internal wall 54 may include unconnected segments 62 and other types of segments.

In one embodiment, an unconnected segment 62 may refer to a segment of the interrupted internal wall 54 that is not directly connected to another segment of the interrupted internal wall 54. For example, according to the embodiment shown in Figure 2, the interrupted internal wall 54 may include three successive unconnected segments 62, and these three successive unconnected segments 62 may not be connected directly to each other. Instead, in one embodiment, each of these three successive unconnected segments 62 may be separated from each other by ribs 58.

In another embodiment, an unconnected segment 62 may refer to a segment of the interrupted internal wall 54 that includes a first end point and a second end point that define the length of the segment, and that is not directly connected to another segment of the interrupted internal wall 54 on at least one of the first end point and the second end point. An unconnected segment 62 may not be directly connected to another segment of the interrupted internal wall 54 on both of the first end point and the second end point of the unconnected segment 62, as is illustrated in Figure 2. In another embodiment, an unconnected segment 62 may not be directly connected to another segment of the interrupted internal wall 54 on only one of first end point and the second end point of the unconnected segment 62. In such an example, the unconnected segment 62 may be directly connected to other segments of the interrupted internal wall 54 (such as directly connected to other unconnected segments 54, or any other type of segment), but such a direct connection may only occur on one of the end points of the unconnected segment 62.

An unconnected segment 62 may have any shape. For example, an unconnected segment 62 may be a straight segment, a curved segment, an irregular segment, any other shaped segment, or any combination of the preceding. An unconnected segment 62 may have any length and/or any width. Furthermore, an unconnected segment 62 may extend uninterrupted to the tip and/or hub (or from the tip to the hub) of the airfoil 12 (or inner diameter and/or outer diameter of the turbine section). As another example, the unconnected segment 62 may end prior to (such as near) the tip and/or hub of the airfoil 12 (or inner diameter and/or outer diameter of the turbine section), allowing cooling fluids to pass to and/or from adjacent cavities. An unconnected segment 62 may be parallel or non-parallel to a camber line 66 halfway between the upper and lower surfaces of the generally elongated hollow airfoil 32. In one embodiment, all of the unconnected segments 62 may be parallel to the camber line 66 of the generally elongated hollow airfoil 32. In another embodiment, all of the unconnected segments 62 may be non-parallel to the camber line 66 of the generally elongated hollow airfoil 32. In a further embodiment, a portion of the unconnected segments 62 may be parallel to the camber line 66 of the generally elongated hollow airfoil 32, and another portion of the unconnected segments 62 may be non-parallel to the camber line 66 of the generally elongated hollow airfoil 32. For example, half of the unconnected segments 62 (or any other portion of the unconnected segments 62) may be parallel to the camber line 66 of the generally elongated hollow airfoil 32, and half of the unconnected segments 62 (or any other remaining portion of the unconnected segments 62) may be non- parallel to the camber line 66 of the generally elongated hollow airfoil 32.

As is discussed above, the cooling system 10 may be formed by a

combination of the outer wall 38, an interrupted internal wall 54, and a plurality of ribs 58 positioned in-between the outer wall 38 and the interrupted internal wall 54. A rib 58 may refer to a segment (or other element) that connects the interrupted internal wall 54 to the outer wall 38, or that is connected to both the pressure side 40 and the suction side 42 of the outer wall 38. For example, as illustrated in Figure 2, the ribs 58 connect the interrupted internal wall 54 to the outer wall 38. The airfoil 12 may include any number of ribs 58. For example, the airfoil 12 may include four ribs 58, five ribs 58, six ribs 58, eight ribs 58, nine ribs 58, ten ribs 58, or any other number of ribs 58. A rib 58 may have any shape. For example, a rib 58 may be a straight segment, a curved segment, an irregular segment, any other shaped segment, or any combination of the preceding. A rib 58 may have any length and/or any width. Furthermore, a rib 58 may be made of the same material as the interrupted internal wall 54.

The ribs 58 may connect the interrupted internal wall 54 to the outer wall 38 in any manner. For example, a rib 58 may connect the interrupted internal wall 54 to both the pressure side 40 of the outer wall 38 and the suction side 42 of the outer wall 38. As another example, a rib 58 may connect the interrupted internal wall 54 to either the pressure side 40 of the outer wall 38 or the suction side 42 of the outer wall 38. In order to connect the interrupted internal wall 54 to the outer wall 38, the ribs 58 may be connected to the unconnected segments 62. The ribs 58 may be connected to any location on the unconnected segments 62. For example, the ribs 58 may be connected to the end points of the unconnected segments 62, as is illustrated in Figure 2. As another example, the ribs 58 may be connected to middle points (or any other points) of the unconnected segments 62. As a further example, the ribs 58 may be connected to inflection points of curved unconnected segments 62. The ribs 58 may be connected to the unconnected segments 62 at an angle 70 (such as angle 70a and angle 70b). The angle 70 (such as angle 70a and angle 70b) may be any angle, such as 30 - 150 degrees. In particular embodiments, when the rib 58 forms an inactive cavity 68 (as is discussed below), the angle 70b may be, for example, 95 - 150 degrees. Furthermore, the ribs 58 may be connected to the outer wall 38 at an angle 71 (such as angle 71 a and angle 71 b). The angle 71 (such as angle 71 a and angle 71 b) may be any angle, such as 30 - 150 degrees. In particular embodiments, when the rib 58 forms an inactive cavity 68 (as is discussed below), the angle 71 b may be, for example, 30 - 85 degrees. Any number of ribs 58 may be connected to an unconnected segment 62 of the interrupted internal wall 54. For example, one rib 58 may be connected to an unconnected segment 62, two ribs 58 may be connected to an unconnected segment 62, three ribs 58 may be connected to an unconnected segment 62, four ribs 58 may be connected to an unconnected segment 62, five ribs 58 may be connected to an unconnected segment 62, six ribs 58 may be connected to an unconnected segment 62, or any other number of ribs 58 may be connected to an unconnected segment 62. The ribs 58 connected to an unconnected segment 62 may connect the unconnected segment 62 to either the pressure side 40 of the outer wall 38 or the suction side 42 of the outer wall 38. In another embodiment, the ribs 58 connected to an unconnected segment 62 may connect the unconnected segment 62 to both the pressure side 40 of the outer wall 38 and the suction side 42 of the outer wall 38. For example, as illustrated in Figure 2, an unconnected segment 62 may be connected to a first rib 58, a second rib 58, a third rib 58, and a fourth rib 58. Furthermore, as illustrated in Figure 2, the first rib 58 and the third rib 58 may connect the unconnected segment 62 to the suction side 42 of the outer wall 38, and the second rib 58 and the fourth rib 58 may connect the unconnected segment 62 to the pressure side 40 of the outer wall 38. Additionally, as illustrated in Figure 2, the first rib 58 and the second rib 58 may be angled from the unconnected segment 62 towards a first direction (e.g., angled towards the left side of Figure 2), while the third rib 58 and the fourth rib 58 may be angled from the unconnected segment 62 towards an opposite direction (e.g., angled towards the right side of Figure 2).

Cooling system 10 may include one or more cooling channels that allow cooling fluids to flow through the cooling system 10 in order to cool the airfoil 12. The cooling channels may allow the cooling fluids to flow in the forward direction (i.e., a direction from the trailing edge 48 towards the leading edge 46), in the aft direction (i.e., a direction from the leading edge 46 towards the trailing edge 48), or both the forward direction and the aft direction. Furthermore, the one or more cooling channels may allow the cooling fluids to flow through all or a portion of the cooling system 10 in order to cool the airfoil 12. As shown in Figure 2, cooling system 10 may include an aft flowing serpentine cooling channel 72 and a forward flowing serpentine cooling channel 74. The aft flowing serpentine cooling channel 72 may extend from a position proximate the root 34 to the tip 50 of an airfoil 12 that is a turbine blade (or, for a turbine vane, from a position proximate the inner diameter to a position proximate the outer diameter of the turbine section). The aft flowing serpentine cooling channel 72 may be formed from at least a two pass serpentine cooling channel, and, in particular embodiments, may be a five-pass serpentine cooling channel or greater. As illustrated, the aft flowing serpentine cooling channel 72 is an aft flowing serpentine cooling channel having aft flowing cavities 82, 84, 86, 88, and 90 in contact with at least one of the pressure side 40 and the suction side 42. Aft flowing cavity 82 may be in communication with a first cooling fluid supply inlet (not shown), and may be configured to pass the cooling fluids through the aft flowing serpentine cooling channel 72 (via aft flowing cavities 84, 86, 88, and 90) to be exhausted from the airfoil through the trailing edge 48, and in at least one embodiment, through a trailing edge exhaust orifice 80.

The forward flowing serpentine cooling channel 74 may extend from a position proximate the root 34 to the tip 50 of an airfoil 12 that is a turbine blade (or, for a turbine vane, from a position proximate the inner diameter to a position proximate the outer diameter of the turbine section). The forward flowing serpentine cooling channel 74 may be formed from at least a two pass serpentine cooling channel, and, in particular embodiments, may be a three-pass serpentine cooling channel or greater. As illustrated, forward flowing serpentine cooling channel 74 is a forward flowing serpentine cooling channel having forward flowing cavities 94, 96, 98, and 100 in contact with at least one of the pressure side 40 and the suction side 42. Forward flowing cavity 94 may be in communication with a second cooling fluid supply inlet (not shown), and may be configured to pass the cooling fluids through the forward flowing cooling channel 74 (via forward flowing cavities 96 and 98) to be exhausted from the airfoil through the leading edge 46, and in at least one embodiment, through leading edge orifices 44. In particular embodiments, cooling fluids flowing through forward flowing cavity 98 may be fed into forward flowing cavity 100 through one or more cross-over holes 102. Furthermore, in particular embodiments, cooling fluids may be used for tip cooling and may be exhausted through the tip 50 of the airfoil 12.

Cooling system 10 may further include one or more inactive cavities 68. An inactive cavity 68 may refer to a cavity that is isolated from the outer wall 38 of the airfoil 12. For example, as is illustrated in Figure 2, the inactive cavity 68 is separated from outer wall 38 by the width of ribs 58. Therefore, although the ribs 58 may be connected to the outer wall 38, the inactive cavity 68 formed by those ribs 58 may not be in contact with the outer wall 38. In particular embodiments, this isolation from the outer wall 38 may prevent any fluids flowing through inactive cavities 68 from contacting the outer wall 38. As such, if any fluids flow through inactive cavities 68, those fluids may not reduce the temperature of the outer wall 38 of the airfoil 12 (or may only reduce the temperature of the outer wall 38 by a negligible amount). In particular embodiments, an inactive cavity 68 may reduce the cross-sectional area of the cooling cavities of the cooling system 10. For example, the inactive cavity 68 may occupy a portion of the spacing in the airfoil 12, thereby reducing the cross- sectional area of the cooling cavities (such as aft flowing cavities 82, 84, 86, 88, and 90 and/or forward flowing cavities 94, 96, and 98). As such, the cooling fluids flowing through the cooling cavities may more efficiently cool the airfoil, even for low flow designs.

In particular embodiments, an inactive cavity 68 may not have any fluids flowing through the inactive cavity 68. For example, the inactive cavity 68 may be a dead space that does not include any active flow of fluids. In further embodiments, an inactive cavity 68 may have fluids flowing through the inactive cavity 68. For example, an inactive cavity 68 may operate as a routing channel that may allow fluids to be routed through the airfoil 12 (such as a turbine vane) in order to supply the fluids from, for example, the outer diameter of the turbine section to the inner diameter of the turbine section, or vice versa. In such an example, the inactive cavity 68 may route the fluids without the fluids being exposed to the high

temperature of the outer wall 38. As another example, a portion of the cooling fluids that are cooling airfoil 12 may flow into the inactive cavity 68 from the cooling channels (such as from aft flowing serpentine cooling channel 72 and forward flowing serpentine cooling channel 74). In such an example, one or more cross-over holes may connect the inactive cavity 68 to one or more of the cooling channels (such as aft flowing cavity 84 of the aft flowing serpentine cooling channel 72 and/or forward flowing cavity 94 of the forward flowing serpentine cooling channel 74), allowing cooling fluid to enter the inactive cavity 68. In particular embodiments, the cross-over holes and/or core ties may provide structural support to the inactive cavities 68 during manufacturing. Furthermore (or alternatively), the inactive cavity 68 may be a portion of the aft flowing serpentine cooling channel 72 and/or forward flowing serpentine cooling channel 74. In such an example, the inactive cavity 68 may form one or more passes (or cavities) of the aft flowing serpentine cooling channel 72 and/or forward flowing serpentine cooling channel 74, allowing the inactive cavity 68 to receive cooling fluids from an adjacent cavity of the cooling channel (via a tip or platform turn) and pass the cooling fluids to another adjacent cavity of the cooling channel (via a tip or platform turn).

The cooling system 10 may include any number of inactive cavities 68. For example, the cooling system 10 may include one inactive cavity 68, two inactive cavities 68, three inactive cavities 68, four inactive cavities 68, or any other number of inactive cavities 68. An inactive cavity 68 may be positioned at any location in cooling system 10. For example, an inactive cavity 68 may be positioned in-between two successive unconnected segments 62. As such, the inactive cavity 68 may separate the two successive unconnected segments 62. As illustrated, the cooling system 10 includes two inactive cavities 68, with the first inactive cavity 68 being positioned in-between a first set of two successive unconnected segments 62 and the second inactive cavity 68 being positioned in-between a second set of two successive unconnected segments 62.

An inactive cavity 68 may be formed by ribs 58. The inactive cavity 68 may be formed by any number of ribs 58. For example, the inactive cavity 68 may be formed by two ribs 58, three ribs 58, four ribs 58, five ribs 58, six ribs 58, or any other number of ribs 58. As shown in Figure 2, the inactive cavity 68 may be formed by four ribs 58: a first rib 58, a second rib 58, a third rib 58, and a fourth rib 58.

Furthermore, as shown in Figure 2, the first rib 58 may be connected to a first unconnected segment 62 and the suction side 42 of the outer wall 38, the second rib 58 may be connected to the first unconnected segment 62 and the pressure side 40 of the outer wall 38, the third rib 58 may be connected to a second unconnected segment 62 and the suction side 42 of the outer wall 38, and the fourth rib 58 may be connected to the second unconnected segment 62 and the pressure side 40 of the outer wall 38, Also, as shown in Figure 2, the first rib 58 may be connected to the third rib 58 (at the suction side 42) and the second rib 58 may be connected to the fourth rib 58 (at the pressure side 40), forming the inactive cavity 68. In another embodiment, although the first rib 58 may be connected to the third rib 58 and the second rib 58 may be connected to the fourth rib 58 (forming the inactive cavity 68), these four ribs 58 may not be directly connected to the outer wall 38. For example, as is illustrated in Figure 3, a fifth rib 59a may extend (at any angle) from the connection of the first and third ribs 58 to connect the first and third ribs 58 indirectly to the suction side 42 of the outer wall 38. As another example, as is also illustrated in Figure 3, a sixth rib 59b may extend (at any angle) from the connection of the second and fourth ribs 58 to connect the second and fourth ribs 58 indirectly to the pressure side 40 of the outer wall 38.

The inactive cavity 68 may have any shape. For example, the inactive cavity 68 may be a diamond, a rhomboid, a triangle, a square, a rectangle, an oval, a circle, any other shape, or any combination of the preceding. In particular embodiments, the inactive cavity 68 may be shaped to be generally symmetric about the camber line 66, as is illustrated in Figure 2. The inactive cavity 68 may have any size.

Furthermore, the inactive cavity 68 may have any length. For example, the inactive cavity 68 may extend to the tip and/or hub of the airfoil 12 (or inner diameter and/or outer diameter of the turbine section). As another example, the inactive cavity 68 may end prior to the tip and/or hub of the airfoil 12 (or inner diameter and/or outer diameter of the turbine section).

During use of cooling system 10, cooling fluids may be passed from a cooling fluid supply (not shown), such as but not limited to, a compressor, to the airfoil 12. A first portion of the cooling fluids enter the aft flowing cavity 82 of the aft flowing serpentine cooling channel 72 via a first cooling fluid supply inlet (not shown). The first portion of the cooling fluids pass through the aft flowing serpentine cooling channel 72 in a serpentine manner, absorbing heat from the surfaces of the pressure side 40 and suction side 42 of the outer wall 38. For example, the first portion of cooling fluids may flow up (e.g., out of the page in Figure 2) aft flowing cavity 82 and pass over to aft flowing cavity 84, flow down (e.g. , into the page in Figure 2) aft flowing cavity 84 and pass under inactive cavity 68 to aft flowing cavity 86, flow up aft flowing cavity 86 and pass over to aft flowing cavity 88, flow down aft flowing cavity 88 and pass under to aft flowing cavity 90, and flow up aft flowing cavity 90 before being exhausted from the airfoil 12 through the trailing edge 48.

A second portion of the cooling fluids also enter the forward flowing cavity 94 of the forward flowing serpentine cooling channel 74 via a second cooling fluid supply inlet (not shown). The second portion of the cooling fluids pass through the forward flowing serpentine cooling channel 74 in a serpentine manner, absorbing heat from the surfaces of the pressure side 40 and suction side 42 of the outer wall 38. For example, the second portion of cooling fluids may flow up forward flowing cavity 94 and pass over to forward flowing cavity 96, flow down forward flowing cavity 96 and pass under to forward flowing cavity 98, and flow up forward flowing cavity 98. Furthermore, the cooling fluids flowing through forward flowing cavity 98 may be fed into forward flowing cavity 100 through one or more cross-over holes 102. The second portion of cooling fluids may impinge on a backside surface of the leading edge 46 and may be exhausted through the orifices 44 forming a

showerhead.

In particular embodiments, no fluids may flow through the inactive cavities 68.

For example, one or more of the inactive cavities 68 may be a dead space that does not include any active flow of fluids. In other embodiments, fluids may flow through the inactive cavities 68. For example, one or more of the inactive cavities 68 may operate as a routing channel that may allow fluids to be routed through the airfoil 12 (such as a turbine vane) in order to supply the fluids from, for example, the outer diameter of the turbine section to the inner diameter of the turbine section, or vice versa. As another example, a portion of the cooling fluids that are cooling airfoil 12 may flow into one or more of the inactive cavities 68. In such an example, a portion of the cooling fluids flowing through aft flowing cavity 84 and/or forward flowing cavity 94, for example, may flow into one or more of the inactive cavities 68 through one or more cross-over holes and/or core ties. The cooling system 10 may include one or more additional elements and/or modifications. For example, the cooling system 10 may include one or more impingement orifices, one or more trailing edge pin fins, one or more blade tip holes, one or more turbulators, one or more film or gill holes, one or more refresher feeds, one or more fillets at the connection points between ribs 58 and the outer wall 38 (or between unconnected segments 62 and ribs 58), any other elements for cooling airfoils 12, or any combination of the preceding.

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.