FIELD OF THE INVENTION

This invention is directed generally to turbine airfoils, and more particularly to cooling systems in hollow turbine airfoils of gas turbine engines.

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. Typically, the leading edge of turbine airfoils includes a plurality of film cooling holes forming a showerhead. While the showerhead of film cooling holes cools the leading edge, conventional showerhead configurations are often inefficient.

SUMMARY OF THE INVENTION

A turbine airfoil usable in a turbine engine and having an internal cooling system with a leading edge showerhead having a plurality of film cooling holes positioned for efficient film cooling is disclosed. The film cooling holes of the showerhead may be aligned in spawnwise extending rows forming the leading edge showerhead. In addition, a middle row of film cooling holes may be positioned along a stagnation line and may be in alternating alignment with pressure and suction side rows forming chordwise extending rows. In particular, a first middle row cooling hole may be aligned with a pressure side row film cooling hole and a second middle row cooling hole may be aligned with a suction side row film cooling hole. The film cooling holes may also have an ejection angle that is nonorthogonal and nonlinear with an axis defining the middle, pressure or suction side rows. The film cooling holes may also be skewed towards a tip of the airfoil. Such configuration eliminates dead spots within the flow pattern of film cooling fluid over the showerhead in the leading edge.

In at least one embodiment, the turbine airfoil may be a turbine blade for use in a gas turbine engine and may be formed from an elongated, hollow airfoil with a leading edge exposed to a high temperature gas flow, a suction side separated from a pressure side, and a trailing edge on an opposite edge of the airfoil from the leading edge. The turbine blade may include an internal cooling system including an impingement cavity positioned within the airfoil along the leading edge of the airfoil and a showerhead arrangement of film cooling holes connected to the impingement cavity. The showerhead may include a middle row of film cooling holes positioned along the stagnation line of the leading edge, a pressure side row of film cooling holes adjacent to the middle row of film cooling holes toward the pressure side, and a suction side of film cooling holes adjacent to the middle row of film cooling holes toward the suction side. The middle row of film cooling holes may be in alternating chordwise alignment with the pressure and suction side rows such that a first middle row cooling hole is aligned with a pressure side row film cooling hole and misaligned with a suction side row film cooling hole forming a first aligned pressure side cooling hole row aligned in a chordwise direction. A second middle row cooling hole may be aligned with a suction side row film cooling hole and misaligned with a pressure side row film cooling hole forming a first aligned suction side cooling hole row aligned in the chordwise direction.

The film cooling holes may be positioned in a variety of angles to best provide film cooling coverage to the leading edge of the elongated, hollow airfoil. The film cooling holes may be positioned at an ejection angle, which is an angle between a spanwise extending axis defining either the middle row, pressure side row or the suction side row and an exhaust axis defining a direction of flow of cooling fluids exhausted from the film cooling holes. In at least one embodiment, an ejection angle of a film cooling hole in the first aligned pressure side cooling hole row may be skewed towards the pressure side of the airfoil. In another embodiment, ejection angles of both film cooling holes forming the chordwise extending first aligned pressure side cooling hole row may be skewed towards the pressure side of the airfoil. The ejection angles of both film cooling holes forming the first aligned pressure side cooling hole row may be aligned with each other towards the pressure side of the airfoil. Similarly, an ejection angle of a film cooling hole in the chordwise extending first aligned suction side cooling hole row may be skewed towards the suction side of the airfoil. In at least one embodiment, the ejection angles of both film cooling holes forming the first aligned suction side cooling hole row may be skewed towards the suction side of the airfoil. Ejection angles of both film cooling holes forming the first aligned suction side cooling hole row may be aligned with each other towards the suction side of the airfoil.

The film cooling holes may be positioned such that an inlet of a cooling hole in the middle row of film cooling holes is positioned on an inner surface of an outer wall forming the airfoil. At least a portion of the inlet may be positioned inward toward the trailing edge from an adjacent cooling hole in the middle row of film cooling holes and may be positioned between an outlet of the cooling hole in the middle row of film cooling holes and an outlet of an adjacent cooling hole forming a chordwise extending cooling hole row. As such, the inlet may be overlapped by portions of adjacent outlets when viewing the cooling holes orthogonal to the showerhead. In at least one embodiment, the film cooling holes may also be angled in the chordwise direction. For instance, one or more film cooling holes forming the middle row of film cooling holes may be nonlinear and nonorthogonal to an outer surface of the airfoil and in a chordwise direction. In particular, one or more film cooling holes forming the middle row of film cooling holes may be positioned less than 26 degrees in the chordwise direction. Similarly, one or more cooling holes forming the pressure side row of film cooling holes and one or more holes forming the suction side row of film cooling holes may be nonlinear and nonorthogonal to an outer surface of the airfoil and in a chordwise direction. In at least one embodiment, each film cooling hole of the middle row of film cooling holes, the pressure side row of film cooling holes and the suction side row of film cooling holes may be nonlinear and

nonorthogonal to an outer surface of the airfoil and in a chordwise direction. Each film cooling hole forming the middle row of film cooling holes, the pressure side row of film cooling holes and the suction side row of film cooling holes may be positioned less than 26 degrees in the chordwise direction.

The film cooling holes may also be positioned such that an ejection angle of at least one film cooling hole of the middle row of film cooling holes may be aligned with an ejection angle of a film cooling hole within the pressure side row of film cooling holes and in an immediately adjacent chordwise row to a chordwise row in which the film cooling hole of the middle row of film cooling holes resides. Similarly, an ejection angle of at least one film cooling hole of the middle row of film cooling holes may be aligned with an ejection angle of a film cooling hole within the suction side row of film cooling holes and in an immediately adjacent chordwise row to a chordwise row in which the film cooling hole of the middle row of film cooling holes resides.

During use, cooling fluids may flow into the cooling system from a cooling fluid supply source. A portion of the cooling fluids may flow into the impingement cavity. The cooling fluids may then flow from the impingement cavity through film cooling holes forming a showerhead in the leading edge. Because of the position of the film cooling holes, the cooling fluids exhausted from the film cooling holes are either emitted in a direction towards the pressure side or the suction side. The cooling holes are positioned so that the cooling fluids flowing from the cooling holes provide efficient coverage over the showerhead without formation of dead spots in the cooling fluid flow.

An advantage of this cooling system is that the cooling flow ejection pattern for the stagnation film row is not the same as the film cooling rows for the blade leading edge pressure and suction side rows. As such, film cooling overlap of conventional systems is eliminated, and the cooling system yields a uniform film layer for the blade leading edge.

Another advantage of this cooling system is that the film cooling for the leading edge stagnation row along the stagnation axis further enhances the convective cooling capability along the stagnation axis.

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 having features according to the invention.

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

Figure 3 is a detailed cross-sectional view of the leading edge showerhead shown in Figure 2 along line 3-3.

Figure 4 is a partial front view of the leading edge showerhead.

Figure 5 is a partial front view of the leading edge showerhead together with film cooling exhaust patterns.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Figures 1 -5, a turbine airfoil 10 usable in a turbine engine 12 and having an internal cooling system 14 with a leading edge showerhead 16 having a plurality of film cooling holes 18 positioned for efficient film cooling is disclosed. The film cooling holes 18 of the showerhead 16, as shown in Figures 4 and 5, may be aligned in spawnwise extending rows 30 and chordwise extending rows 31 forming the leading edge showerhead 16. In addition, a middle row 24 of film cooling holes 18 may be positioned along a stagnation line and may be in alternating alignment with pressure and suction side rows 26, 28 forming chordwise extending rows 31 . In particular, a first middle row cooling hole 32 may be aligned with a pressure side row film cooling hole 34 and a second middle row cooling hole 36 may be aligned with a suction side row film cooling hole 38. The film cooling holes 18 may also have an ejection angle 40 that is nonorthogonal and nonlinear with an axis 42 defining the middle, pressure or suction side rows 24, 26 and 28. The film cooling hoels may be skewed towards a tip of the airfoil. Such configuration eliminates dead spots within the flow pattern of film cooling fluid over the showerhead 16 in the leading edge 46.

In at least one embodiment, as shown in Figures 1 and 2, the turbine airfoil 10 may be a rotatable turbine blade or other airfoil. The turbine blade 10 may be formed from an elongated, hollow airfoil 44 with a leading edge 46 exposed to a high temperature gas flow, a suction side 48 separated from a pressure side 50, and a trailing edge 52 on an opposite side edge to the airfoil from the leading edge 46. The turbine blade 10, as shown in Figures 2 and 3, may include the internal cooling system 14 with an impingement cavity 54 positioned within the airfoil 44 along the leading edge 46 of the airfoil 44. The internal cooling system 14 may also include a showerhead 16 arrangement of film cooling holes 18 connected to the impingement cavity 54. As shown in Figures 4 and 5, the showerhead 16 may include a middle row 24 of film cooling holes 18 positioned along a stagnation line 56 of the leading edge 46, a pressure side row 34 of film cooling holes 18 adjacent to the middle row 24 of film cooling holes 18 toward the pressure side 50, and a suction side row 38 of film cooling holes 18 adjacent to the middle row 24 of film cooling holes 18 toward the suction side 48. The middle row 24 of film cooling holes 18, the pressure side row 34 of film cooling holes 18 and the suction side row 38 of film cooling holes 18 may be spanwise extending rows 30. The middle row 24 of film cooling holes 18 may be in an alternating chordwise extending pattern of alternating alignment with the pressure and suction side rows 34, 38 such that a first middle row 32 cooling hole is aligned with a pressure side row film cooling hole 34 and misaligned with a suction side row film cooling hole 38 forming a first aligned pressure side cooling hole row 58 aligned in a chordwise direction 62, and a second middle row cooling hole 36 is aligned with a suction side row film cooling hole 38 and misaligned with a pressure side row film cooling hole 34 forming a first aligned suction side cooling hole row 60 aligned in the chordwise direction 62.

The film cooling holes 18 may be positioned in a variety of angles to best provide film cooling coverage to the leading edge 46 of the elongated, hollow airfoil 44. The film cooling holes 18 may be positioned at angles relative to one or more axes. An ejection angle 40 is an angle between a spanwise extending axis 42 defining either the middle row 24, pressure side row 26 or the suction side row 28 and an exhaust axis 64 defining a direction of flow of cooling fluids exhausted from the film cooling holes 18. In at least one embodiment, an ejection angle 40 of a film cooling hole in the first aligned pressure side cooling hole row 58 may be skewed towards the pressure side 50 of the airfoil 44. In another embodiment, ejection angles 40 of both film cooling holes 18 forming the chordwise extending first aligned pressure side cooling hole row 58 are skewed towards the pressure side 50 of the airfoil 44. The ejection angles 40 of both film cooling holes 18 forming the first aligned pressure side cooling hole row 58 may be aligned with each other towards the pressure side 50 of the airfoil 44. Similarly, ejection angles 40 of a film cooling hole 18 in the first aligned suction side cooling hole row 60 may be skewed towards the suction side 48 of the airfoil 44. In another embodiment, ejection angles 40 of both film cooling holes 18 forming the chordwise extending first aligned suction side cooling hole row 60 may be skewed towards the suction side 48 of the airfoil 44. The ejection angles 40 of both film cooling holes 18 forming the first aligned suction side cooling hole row 58 are aligned with each other towards the suction side 48 of the airfoil 44. The ejection angles 40 of the film cooling holes 18 making up the middle row 24, the pressure side row 26 and the suction side row 28 may be any appropriate size. In at least one embodiment, the ejection angles 40 of the film cooling holes 18 making up the middle row 24, the pressure side row 26 and the suction side row 28 may be less than about 45 degrees. In yet another embodiment, the ejection angles 40 of the film cooling holes 18 making up the middle row 24, the pressure side row 26 and the suction side row 28 may be between about 10 degrees and about 30 degrees. The configuration of the cooling holes 18 may be such that an inlet 66 of a cooling hole 18 in the middle row 24 of film cooling holes 18 is positioned on an inner surface 68 of an outer wall 70 forming the airfoil 44. At least a portion of the inlet 66 may be positioned inward toward the trailing edge 52 from an adjacent cooling hole 18 in the middle row 24 of film cooling holes 18 and is positioned between an outlet 72 of the cooling hole 18 in the middle row 24 of film cooling holes 18 and an outlet 74 of an adjacent cooling hole 18 forming a chordwise extending cooling hole row 31 . As such, the inlet 66 of a cooling hole 18 may be positioned at least in partial alignment, via an axis extending orthogonally into the airfoil 44 from an outer surface 76 forming the leading edge 46, with a chordwise extending rows 31 of adjacent cooling holes 18.

One or more of the film cooling holes 18 may also be positioned at another angle relative to the outer surface 76 forming the airfoil 44. For example, in at least one embodiment, one or more film cooling holes 18 forming the middle row 24 of film cooling holes 18 may be nonlinear and nonorthogonal to the outer surface 76 of the airfoil 44 and in a chordwise direction. In at least one embodiment, one or more film cooling holes 18 forming the middle row 24 of film cooling holes 18 may be positioned less than 26 degrees in the chordwise direction. Similarly, one or more cooling holes 18 forming the pressure side row 26 of film cooling holes 18 or one more cooling holes 18 forming the suction side row 28 of film cooling holes 18 are nonlinear and nonorthogonal to an outer surface 76 of the airfoil 44 and in a chordwise direction, or both. In at least one embodiment, each film cooling hole 18 of the middle row 24 of film cooling holes 18, the pressure side row 26 of film cooling holes 18 and the suction side row 28 of film cooling holes 18 may be nonlinear and nonorthogonal to the outer surface 76 of the airfoil 44 and in a chordwise direction. In at least one embodiment, each film cooling hole 18 forming the middle row 24 of film cooling holes 18, the pressure side row 26 of film cooling holes 18 and the suction side row 28 of film cooling holes 18 may be positioned less than 26 degrees in the chordwise direction. The film cooling holes 18 may be angled toward a tip 78 of the airfoil 44 or towards a root 80 of the airfoil 10.

As shown in Figure 4, the film cooling holes 18 may also be aligned in position within the showerhead 16 such that a middle row cooling hole 18 in a first row 84 is aligned with a cooling hole in a same chordwise extending first row 84. In particular, an ejection angle 40 of one or more film cooling holes 18 of the middle row 24 of film cooling holes 18 may be aligned with an ejection angle 40 of a film cooling hole 18 within the pressure side row 26 of film cooling holes 18 and in the same chordwise row. Similarly, an ejection angle 40 of one or more film cooling holes 18 of the middle row 24 of film cooling holes 18 may be aligned with an ejection angle 40 of a film cooling hole 18 within the suction side row 28 of film cooling holes 18 and in the same chordwise row.

During use, cooling fluids may flow into the cooling system 14 from a cooling fluid supply source. A portion of the cooling fluids may flow into the impingement cavity 54. The cooling fluids may then flow from the impingement cavity 54 through film cooling holes 18 forming a showerhead in the leading edge 36. Because of the position of the film cooling holes 18, the cooling fluids exhausted from the film cooling holes 18 are either emitted in a direction towards the pressure side 50 or the suction side 48. The cooling holes 18 are positioned so that the cooling fluids flowing from the cooling holes 18 provide efficient coverage over the showerhead 16 without formation of dead spots in the cooling fluid flow.

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.