Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
1999-10-22
2001-07-10
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
With heating, cooling or thermal insulation means
Changing state mass within or fluid flow through working...
Reexamination Certificate
active
06257831
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to manufacturing of airfoil structures suited for gas turbine engines and, more particularly, to a new cast hollow airfoil structure with openings which do not require plugging.
2. Description of the Prior Art
Gas turbine engine airfoils, such as gas turbine blades and vanes, may be provided with an internal cavity defining cooling passageways through which cooling air can be circulated. By cooling these airfoils, they can be used in an engine environment which is hotter than the melting point of the airfoil metal.
Typically, the internal passages are created by casting with a solid, ceramic core which is later removed by well known techniques, such as dissolving techniques.
The core forms the inner surface and tip cavity of the hollow airfoil, while a mold shell forms the outer surface of the airfoil. During the casting process, molten metal fills the space between the core and the shell mold. After this molten metal solidifies, the mold shell and the core are removed, leaving a hollow metal structure.
The region of the core which later forms the tip cavity is connected to the main body of the core by tip supports. These tip supports later form the tip openings in the metal airfoil.
The casting core must be accurately positioned and supported with the mold shell in order to ensure dimensional precision of the cast product. The core is held within the shell mold by the regions of the core which later form the passage through the fixing, the trailing edge exit slots, and the tip cavity. The core is rigidly held at these extremities. During the casting process in which molten metal is poured around the core, a significant force is exerted on the core which may break the tip supports.
In order to minimize the manufacturing cost of each airfoil, the tip supports should be sufficiently large to avoid breakage during the casting process. It is also necessary to minimize the quantity of coolant air which exits the airfoil tip openings, in order to preserve the overall gas turbine engine performance.
It is possible to cast large tip openings, then plug these openings using a welding, brazing or similar process, however there would be an extra cost associated with this additional process.
Accordingly, there is a need for a new internal structure for gas turbine engine airfoils which allows for improved strength of the core during the casting process, without requiring plugging of tip openings.
SUMMARY OF THE INVENTION
It is therefore an aim of the present invention to improve the strength of a casting core used in the manufacturing of an airfoil suited for a gas turbine engine.
It is also an aim of the present invention to facilitate the manufacturing of an airfoil for a gas turbine engine.
It is also an aim of the present invention to provide a new and improved casting core for an airfoil.
It is still a further aim of the present invention to provide a cast airfoil having a new internal design allowing for relatively large core support members to be used during the casting process, while restricting the quality of cooling fluid which passes through the resulting opening when the cast airfoil is assembled in a gas turbine engine.
Therefore, in accordance with the present invention, there is provided a cooled airfoil for a gas turbine engine, comprising a body defining an internal cooling passage for passing a cooling fluid therethrough to convectively cool the airfoil, at least one opening left by a support member of a casting core used during casting of the airfoil. The opening extends through the body and is in flow communication with the internal cooling passage. At least one flow deflector is provided within the body for deflecting a desired quantity of cooling fluid away from the opening.
According to a further general aspect of the present invention, there is provided a casting core for use in the manufacturing of a hollow gas turbine engine airfoil, comprising a main portion adapted to be used for forming the internal geometry of an airfoil having at least one internal cooling passage through which a cooling fluid can be circulated to convectively cool the airfoil, at least one point of support on the main portion, the point of support resulting in an opening through the airfoil, and wherein the main airfoil portion is provided with flow deflector casting means to provide a flow deflector arrangement within the internal cooling passage to direct a selected quantity of the cooling flow away from the opening while the airfoil is being used.
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Abdel-Messeh William
Papple Michael
Tibbott Ian
Astle Jeffrey W.
Look Edward K.
Nguyen Ninh
Pratt & Whitney Canada Corp.
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