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 support systems for hollow airfoils usable in a gas turbine engine and having an outer diameter support structure.

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. Turbine engines typically include a plurality of rows of stationary turbine vanes extending radially inward from a shell and include plurality of rows of rotatable turbine blades attached to a rotor assembly for turning the rotor.

Row one turbine vanes may be axially supported at the outer diameter (OD) end of the vanes with a simple support. Row two turbine vanes are often supported by a vane hook and rail forming a cantilevered support, as shown in Figures 1 -3. The cantilevered support often drives stress into the leading edge of the vane because of the shroud curling effect due to the hotside to coldside temperature differential and due to the aerodynamic pressure loading on the airfoil and pressure differential on the interstage seal housing. Another major difference between a vane one and vane two is the position of the shroud due to the increase in hot gas path flow area, as depicted by the angled shrouds for the vane two. The angle of the shroud with the airfoil creates an acute angle at the leading edge, which complicates the joint design. Such angle of the airfoil and the shroud creates a high stress concentration with a bicast vane.

SUMMARY OF THE INVENTION

A support system for a bicast turbine vane of a gas turbine engine is disclosed. The support system may be formed from an outer attachment system that includes upstream and downstream radially extended axial hooks with an airfoil support positioned between the upstream and downstream radially extended axial hooks. The upstream radially extended axial hook may be configured to reduce stress therein. An airfoil support may be curved and formed from a pressure side curved support and a suction side curved support. A downstream portion of the airfoil support may be linear and generally aligned with a centerline of the gas turbine engine to accommodate the curved joint formed by the pressure side and suction side curved supports, thereby reducing stress within the upstream radially extended axial hook.

In at least one embodiment, the support system may include a generally elongated hollow airfoil vane formed from an outer wall, and having a leading edge, a trailing edge, a pressure side, a suction side, an inner attachment system at a first end of the airfoil and an outer attachment system at a second end opposite to the first end and the inner attachment system. The outer attachment system may include upstream and downstream radially extended axial hooks with an airfoil support positioned between the upstream and downstream radially extended axial hooks. At least a portion of the airfoil support at the upstream radially extended axial hook may be curved and formed from a pressure side curved support and a suction side curved support. The pressure side curved support may be curved radially outward away from a radially outer surface of an outer shroud at the second end, which may, in at least one embodiment, be the outer diameter location of the airfoil. The suction side curved support may be curved radially outward away from a radially outer surface of an outer platform at the second end. The generally elongated hollow airfoil vane may have a leading edge at the second end that extends at least into the upstream radially extended axial hook.

The airfoil support may have a downstream portion that is generally aligned with a centerline of the gas turbine engine. The downstream portion may be generally linear. The airfoil support may extend continuously between the upstream and downstream radially extended axial hooks. The downstream portion may extend linearly from the pressure side curved support to the downstream radially extended axial hook and from the suction side curved support to the downstream radially extended axial hook. The downstream portion may be formed from a downstream suction side and a downstream pressure side. The downstream pressure side of the outer attachment system may be positioned downstream from the pressure side curved support and upstream from the downstream radially extended axial hook. The downstream suction side of the outer attachment system may be positioned downstream from the suction side curved support and upstream from the

downstream radially extended axial hook.

The generally elongated hollow airfoil vane may have a leading edge with a radially outer surface at the second end that extends to be flush with an outer surface of the upstream radially extended axial hook. Alternatively, the leading edge with a radially outer surface at the second end may stop short of the outer surface of the upstream radially extended axial hook. The pressure side curved support may have an upstream end that is flush with an outer surface of the upstream radially extended axial hook. The suction side curved support may have an upstream end that is flush with an outer surface of the upstream radially extended axial hook. The pressure side curved support may be flush with an outer surface of the generally elongated hollow airfoil vane. The suction side curved support may be flush with an outer surface of the generally elongated hollow airfoil vane.

During use, aero loads are applied to a pressure side of the turbine vane. With the turbine vane secured at the upstream radially extended axial hook having a curved airfoil support extending between the upstream and downstream radially extended axial hooks and a portion generally parallel to a gas path of the outer platform, both the upstream radially extended axial hook and the downstream radially extended axial hook remain axially seated with reduced stress

concentrations when compared with conventional systems with a cantilevered OD connection system paired with an acute angle between a leading edge of the vane airfoil and the platform.

An advantage of the support system is that the curved airfoil support extending between the upstream and downstream radially extended axial hooks and a downstream portion generally parallel to a gas path of the outer platform transfers the loading on the airfoil to the outer platform, which results in reduced stress concentrations.

Another advantage of the support system is that the joint between the generally elongated hollow airfoil vane and the airfoil support may be positioned generally parallel with the turbine engine centerline, which allows radial forces to be more evenly distributed across the joint.

Yet another advantage of the support system is that the pressure and suction curved supports of the airfoil support forming the joint between the airfoil support and the generally elongated hollow airfoil vane are curved radially outward, which increase the distance between the joint and the area of high stress for a cantilevered support vane.

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 side view of a conventional row two turbine vane supported in a conventional manner from the upstream and downstream hooks at the OD platform.

Figure 2 is a detailed, side view of the connection of the turbine airfoil with the platform shown in Figure 1 .

Figure 3 is a detailed, perspective view of the connection of the turbine airfoil with the platform shown in Figure 1 .

Figure 4 is a cross-sectional view of a gas turbine engine. Figure 5 is a perspective view of an elongated hollow airfoil vane attached to a support system displaying aspects of this invention.

Figure 6 is a side view of the support system of Figure 4.

Figure 7 is a top view of the outer platform of the support system.

DETAILED DESCRIPTION OF THE INVENTION

As shown in Figures 4-7, a support system 10 for a bicast turbine vane 12 of a gas turbine engine 14 is disclosed. The support system 10 may be formed from an outer attachment system 16 that includes upstream and downstream radially extended axial hooks 18, 20 with an airfoil support 22 positioned between the upstream and downstream radially extended axial hooks 18, 20. An airfoil support 22 may be curved and formed from a pressure side curved support 24 and a suction side curved support 26. A downstream portion 28 of the airfoil support 22 may be linear and generally aligned with a centerline 30 of the gas turbine engine 14 to accommodate the curved joint formed by the pressure side and suction side curved supports 24, 26, thereby reducing stress within the upstream radially extended axial hook 18. The curved airfoil support 22 extending between the upstream and downstream radially extended axial hooks 18, 20 and a downstream portion 28 generally parallel to a gas path of the outer platform 52 transfers the loading on the airfoil 12 to the outer platform 52, which results in reduced stress concentrations.

The support system 10, as shown in Figures 5-7, may include a generally elongated hollow airfoil vane 32 formed from an outer wall 34, and having a leading edge 36, a trailing edge 38, a pressure side 40, a suction side 42, an inner attachment system 44 at a first end 46 of the airfoil 32 and an outer attachment system 16 at a second end 48 opposite to the first end 46 and the inner attachment system 44. The outer attachment system 16 may include upstream and downstream radially extended axial hooks 18, 20 with an airfoil support 22 positioned between the upstream and downstream radially extended axial hooks 18, 20. The upstream and downstream radially extended axial hooks 18, 20 may extend for an entire width of the outer platform 52 or only for a portion of a width of the outer platform 52.

At least a portion of the airfoil support 22 at the upstream radially extended axial hook 18 may be curved and formed from a pressure side curved support 24 and a suction side curved support 26. The pressure side curved support 24 may be curved radially outward away from a radially outer surface 50 of an outer platform 52 at the second end 48. The suction side curved support 26 may be curved radially outward away from a radially outer surface 50 of an outer platform 52 at the second end 48. The generally elongated hollow airfoil vane 32 may have a leading edge 36 at the second end 48 that extends at least into the upstream radially extended axial hook 18.

As shown in Figure 4, the airfoil support 22 may have a downstream portion 28 that is generally aligned with a centerline 30 of the gas turbine engine 14. The downstream portion 28 may be generally linear. The airfoil support 22 may extend continuously between the upstream and downstream radially extended axial hooks 18, 20. The downstream portion 28 may extend linearly from the pressure side curved support 24 to the downstream radially extended axial hook 20 and from the suction side curved support 26 to the downstream radially extended axial hook 20. The downstream portion 28 may be formed from a downstream suction side 54 and a downstream pressure side 56. The downstream pressure side 56 of the outer attachment system 16 may be positioned downstream from the pressure side curved support 24 and upstream from the downstream radially extended axial hook 20. The downstream suction side 54 of the outer attachment system 16 may be positioned downstream from the suction side curved support 26 and upstream from the downstream radially extended axial hook 20.

The airfoil support 22 formed from the pressure side curved support 24, the pressure side curved support 26, and the downstream portion 28, which is formed from the downstream suction side 54 and the downstream pressure side 56 provides support for the generally elongated hollow airfoil vane 32 where it extends radially outward from an outer surface 50 of the outer platform 52. In at least one

embodiment, the pressure side curved support 24, the pressure side curved support 26, and the downstream portion 28, which is formed from the downstream suction side 54 and the downstream pressure side 56 may each have a width of between about three millimeters and about eight millimeters. In another embodiment, the pressure side curved support 24, the pressure side curved support 26, and the downstream portion 28, which is formed from the downstream suction side 54 and the downstream pressure side 56 may each have a width of between about four millimeters and about five millimeters. Each of the pressure side curved support 24, the pressure side curved support 26, the downstream suction side 54 and the downstream pressure side 56 may have equal widths. In other embodiments, one or more of the pressure side curved support 24, the pressure side curved support 26, the downstream suction side 54 and the downstream pressure side 56 may have different widths.

As shown in Figures 5 and 6, the generally elongated hollow airfoil vane 32 may have a leading edge 36 with a radially outer surface 50 at the second end 48 that extends to be flush with an outer surface 58 of the upstream radially extended axial hook 18. The pressure side curved support 24 may have an upstream end 60 that is flush with an outer surface 58 of the upstream radially extended axial hook 18. The suction side curved support 26 may have an upstream end 62 that is flush with an outer surface 58 of the upstream radially extended axial hook 18. The pressure side curved support 24 may be flush with an outer surface 62 of the generally elongated hollow airfoil vane 32. The suction side curved support 26 may be flush with an outer surface 62 of the generally elongated hollow airfoil vane 32.

As shown in Figure 6, the generally elongated hollow airfoil vane 32 may include one or more first tabs 64 extending from a pressure side 40 of the airfoil support 22. The generally elongated hollow airfoil vane 32 may include one or more second tabs 66 extending from a suction side 42 of the airfoil support 22. The first tab 64 may extend from the pressure side 40 into a tab receiving chamber 68 in the upstream radially extended axial hook 18. In at least one embodiment, the first tab 64 may extend from the pressure side 40 at the leading edge 36. The first tab 64 may extend for all of or a part of a length of the generally elongated hollow airfoil vane 32 within the upstream radially extended axial hook 18. The first tab 64 may have a rectangular shaped cross-section or may have another shaped cross-section. The first tab 64 may extend from the generally elongated hollow airfoil vane 32 a distance generally equal to a width of the first tab 64.

The second tab 66 may extend from the suction side 42 into a tab receiving chamber 70 in the upstream radially extended axial hook 18. In at least one embodiment, the second tab 66 may extend from the suction side 42 at the leading edge 36. The second tab 66 may extend for all of or a part of a length of the generally elongated hollow airfoil vane 32 within the upstream radially extended axial hook 18. The second tab 66 may have a rectangular shaped cross-section or may have another shaped cross-section. The second tab 66 may extend from the generally elongated hollow airfoil vane 32 a distance generally equal to a width of the second tab 66.

The bicast turbine vane 12 and support system 10 may be formed from materials, such as, but not limited to, nickel based alloys, single crystal alloys or directionally solidified (DS) alloys. The bicast turbine vane 12 may be formed by first creating the generally elongated hollow airfoil vane 32. The bicast turbine vane 12 may be formed using a conventional process or a process not yet created. The outer platform 52 may be formed around the radially outer end of the generally elongated hollow airfoil vane 32.

During use, aero loads are applied to a pressure side 40 of the turbine vane 12. With the turbine vane 12 secured at the upstream radially extended axial hook 18, both the upstream radially extended axial hook 18 and the downstream radially extended axial hook 20 remain axially seated with reduced stress concentration when compared with conventional systems with a cantilevered OD connection system paired with an acute angle between a leading edge of the vane airfoil and the platform.

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.