Patent Application
20140068939
The present invention generally involves a method for manufacturing an airfoil.
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.
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.
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:
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,
The exemplary airfoil 10 shown in
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, 4th 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.
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.
