METHOD FOR MANUFACTURING AN AIRFOIL

Abstract

A method for manufacturing an airfoil includes casting the airfoil around a core and creating a hole through a surface of the airfoil with a water jet. The method further includes striking at least a portion of the core inside the airfoil with the water jet and removing the core from inside the airfoil.

Description

FIELD OF THE INVENTION

The present invention generally involves a method for manufacturing an airfoil.

BACKGROUND OF THE INVENTION

Turbines are widely used in industrial and commercial operations. A typical commercial steam or gas turbine used to generate electrical power includes alternating stages of stationary and rotating airfoils. For example, stationary vanes may be attached to a stationary component such as a casing that surrounds the turbine, and rotating blades may be attached to a rotor located along an axial centerline of the turbine. A compressed working fluid, such as but not limited to steam, combustion gases, or air, flows through the turbine, and the stationary vanes accelerate and direct the compressed working fluid onto the subsequent stage of rotating blades to impart motion to the rotating blades, thus turning the rotor and performing work.

The efficiency of the turbine generally increases with increased temperatures of the compressed working fluid. However, excessive temperatures within the turbine may reduce the longevity of the airfoils in the turbine and thus increase repairs, maintenance, and outages associated with the turbine. As a result, various designs and methods have been developed to provide cooling to the airfoils. For example, a cooling media may be supplied to a cavity inside the airfoil to convectively and/or conductively remove heat from the airfoil. In particular embodiments, the cooling media may flow out of the cavity through cooling passages in the airfoil to provide film cooling over the outer surface of the airfoil.

As temperatures and/or performance standards continue to increase, the materials used for the airfoil become increasingly thin, making reliable manufacture of the airfoil increasingly difficult. Specifically, the airfoil is typically cast from a high alloy metal, and the cooling passages are often drilled or machined into the high alloy metal at precise locations and in precise geometries after casting to optimize the cooling media flow over the airfoil. For example, a water jet may be used to drill the cooling passages through the high alloy metal at particular locations and angles to enhance the cooling media flow over the outer surface of the airfoil. Although effective at accurately drilling small diameter holes through the high metal alloy, the water jet may also introduce grit byproducts inside the airfoil that may be difficult to completely remove. Alternately or in addition, the water jet may inadvertently strike the interior of the airfoil on the opposite side of the cavity causing damage inside the airfoil. The grit byproducts inside the airfoil and/or damage to the interior of the airfoil may be difficult to detect during the finishing steps. As a result, a method for manufacturing an airfoil that reduces or prevents the introduction of grit byproducts into the airfoil and/or inadvertent damages to the interior of the airfoil would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.

One embodiment of the present invention is a method for manufacturing an airfoil that includes casting the airfoil around a core and creating a hole through a surface of the airfoil with a water jet. The method further includes striking at least a portion of the core inside the airfoil with the water jet and removing the core from inside the airfoil.

Another embodiment of the present invention is a method for manufacturing an airfoil that includes casting a high alloy metal around a core and penetrating a surface of the high alloy metal with a water jet. The method further includes striking at least a portion of the core inside the high alloy metal with the water jet and removing the core from inside the high alloy metal.

Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

FIG. 1 is a perspective view of an exemplary airfoil according to an embodiment of the present invention;

FIG. 2 is a plan view of a core for manufacturing the airfoil shown in FIG. 1; and

FIG. 3 is a cross-section view of the airfoil shown in FIG. 1 and the core shown in FIG. 2 after casting according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. In addition, the terms “upstream” and “downstream” refer to the relative location of components in a fluid pathway. For example, component A is upstream from component B if a fluid flows from component A to component B. Conversely, component B is downstream from component A if component B receives a fluid flow from component A.

Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Various embodiments of the present invention include a method for manufacturing an airfoil. Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures, FIG. 1 provides a perspective view of an exemplary airfoil 10 according to an embodiment of the present invention. As shown in FIG. 1, the airfoil 10 generally includes a pressure side 12 having a concave curvature and a suction side 14 having a convex curvature and opposed to the pressure side 12. The pressure and suction sides 12, 14 are separated from one another to define a cavity 16 inside the airfoil 10 between the pressure and suction sides 12, 14. The cavity 16 may provide a serpentine or tortuous path for a cooling media to flow inside the airfoil 10 to conductively and/or convectively remove heat from the airfoil 10. In addition, the pressure and suction sides 12, 14 further join to form a leading edge 18 at an upstream portion of the airfoil 10 and a trailing edge 20 downstream from the cavity 16 at a downstream portion of the airfoil 10. A plurality of cooling passages 22 in the pressure side 12, suction side 14, leading edge 18, and/or trailing edge 20 may provide fluid communication from the cavity 16 through the airfoil 10 to supply the cooling media over the outer surface of the airfoil 10. As shown in FIG. 1, for example, the cooling passages 22 may be located at the leading and trailing edges 18, 20 and/or along either or both of the pressure and suction sides 12, 14. One of ordinary skill in the art will readily appreciate from the teachings herein that the number and/or location of the cooling passages 22 may vary according to particular embodiments, and the present invention is not limited to any particular number or location of cooling passages 22 unless specifically recited in the claims.

The exemplary airfoil 10 shown in FIG. 1 may be manufactured using any investment casting process known in the art. For example, FIG. 2 provides a plan view of a core 30 that may be used to manufacture the airfoil 10 shown in FIG. 1. As shown in FIG. 2, the core 30 may include a serpentine portion 32 with a number of long, thin branches or projections 34 that extend from the serpentine portion 32. The serpentine portion 32 generally corresponds to the size and location for the cavity 16 in the airfoil 10, and the projections 34 generally correspond to the size and location of the larger cooling passages 22 through the trailing edge 20 of the airfoil 10. The core 30 may be manufactured from any material having sufficient strength to withstand the high temperatures associated with the casting material (e.g., a high alloy metal) while maintaining tight positioning required for the core 30 during casting. For example, the core 30 may be cast from ceramic material, ceramic composite material, or other suitable materials. Once cast or otherwise manufactured, a laser, electron discharge machine, drill, water jet, or other suitable device may be used to refine or form the serpentine portion 32 and/or projections 34 shown in FIG. 2. Additional cooling passages 22, for example, through the pressure side 12, suction side 14, and/or leading edge 18, too small to be manufactured by casting may be machined into the airfoil 10 after casting, as will be described later.

The core 30 may then be utilized in a lost wax process or other casting process as is known in the art. For example, the core 30 may be coated with a wax or other suitable material readily shaped to the desired thickness and curvature for the airfoil 10. The wax-covered core 30 may then be repeatedly dipped into a liquid ceramic solution to create a ceramic shell over the wax surface. The wax may then be heated to remove the wax from between the core 30 and the ceramic shell, creating a void between the core 30 and the ceramic shell that serves as a mold for the airfoil 10.

A molten high alloy metal 40 may then be poured into the mold to form the airfoil 10. The high alloy metal 40 may include, for example, nickel, cobalt, and/or iron super alloys such as GTD-111, GED-222, Rene 80, Rene 41, Rene 125, Rene 77, Rene N5, Rene N6, PWA 1484, PWA 1480, 4^th generation single crystal super alloy, MX-4, Hastelloy X, cobalt-based HS-188, and similar alloys. After the high alloy metal 40 cools and solidifies, the ceramic shell may be broken and removed, exposing the high alloy metal 40 that has taken the shape of the void created by the removal of the wax.

FIG. 3 provides a cross-section view of the airfoil 10 and core 30 as shown in FIGS. 1 and 2, respectively, after casting according to an embodiment of the present invention. As shown in FIG. 3, the high alloy metal 40 has been cast around the core 30 to form the airfoil 10 around the core 30. An apparatus 50 may direct a water jet 52 at the airfoil 10 to create one or more holes 54 through a surface 56 of the high alloy metal 40. The holes 54 may be any size or diameter, and the water jet 52 is particularly suitable for forming holes 54 having a size or diameter less than 1 mm which would otherwise be difficult to form by casting. After penetrating through the surface 56 of the airfoil 10, the water jet 52 may then strike at least a portion of the core 30 inside the airfoil 10. In this manner, the core 30 prevents the water jet 52 from travelling across the empty cavity 16 and impacting and possibly damaging the high alloy metal 40 on the other side of the cavity 16.

The water jet 52 may further include an abrasive material that enhances the rapid and precise penetration of the water jet 52 through the surface 56 of the airfoil 10. In particular embodiments, the abrasive material may include one or more garnets, aluminum oxides, or other suitable materials for cutting through the surface 56 of the airfoil 10. After penetrating through the surface 56 of the airfoil 10, the water jet 52 and abrasive material may then strike at least a portion of the core 30 inside the airfoil 10. In this manner, the core 30 prevents the water jet 52 and abrasive material from travelling across the empty cavity 16 and impacting and possibly damaging the high alloy metal 40 on the other side of the cavity 16. In addition, the core 30 may prevent the abrasive material from spreading or dispersing inside the cavity 16 of the airfoil 10, facilitating easier removal of the abrasive material after use of the apparatus 50 is complete.

Once the desired holes 54 have been cut into the airfoil 10 or high alloy metal 40, the core 30 may be removed from inside the airfoil 10 using methods known in the art. For example, the core 30 may be dissolved through a leaching process to remove the core 30 and any abrasive material from inside the airfoil 10, leaving the cavity 16, cooling passages 22, and/or holes 54 in the airfoil 10.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

1. A method for manufacturing an airfoil, comprising:

a. casting the airfoil around a core;

b. creating a hole through a surface of the airfoil with a water jet;

c. striking at least a portion of the core inside the airfoil with the water jet; and

d. removing the core from inside the airfoil.

2. The method as in claim 1, further comprising creating the core from a ceramic material.

3. The method as in claim 1, further comprising striking the surface of the airfoil with an abrasive material in the water jet.

4. The method as in claim 1, further comprising striking the surface of the airfoil with at least one of garnet or aluminum oxide.

5. The method as in claim 1, further comprising striking the portion of the core with at least one of garnet or aluminum oxide.

6. The method as in claim 1, further comprising striking the portion of the core with an abrasive material in the water jet.

7. The method as in claim 6, further removing the abrasive material from inside the airfoil.

8. The method as in claim 1, further comprising removing the core from the airfoil by leaching.

9. A method for manufacturing an airfoil, comprising:

a. casting a high alloy metal around a core;

b. penetrating a surface of the high alloy metal with a water jet;

c. striking at least a portion of the core inside the high alloy metal with the water jet; and

d. removing the core from inside the high alloy metal.

10. The method as in claim 9, further comprising creating the core from a ceramic material.

11. The method as in claim 9, further comprising striking the surface of the high alloy metal with an abrasive material in the water jet.

12. The method as in claim 9, further comprising striking the surface of the high alloy metal with at least one of garnet or aluminum oxide.

13. The method as in claim 9, further comprising striking the portion of the core with at least one of garnet or aluminum oxide.

14. The method as in claim 9, further comprising striking the portion of the core with an abrasive material in the water jet.

15. The method as in claim 14, further removing the abrasive material from inside the high alloy metal.

16. The method as in claim 9, further comprising leaching the core from inside the high alloy metal.