Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1998-07-31
2001-01-30
Heckler, Thomas M. (Department: 2787)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S098000
Reexamination Certificate
active
06181978
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to blending an airfoil surface to a platform surface and more particularly to generating a smooth blending fillet surface between an airfoil shape and a restricted platform surface upon which the airfoil is mounted.
Typically, a turbine blade designer uses a computer-aided design (CAD) system or a computer-aided manufacture (CAM) system to generate a fillet surface for blending an airfoil surface to a platform surface. The process of creating a fillet blend on a CAD system requires identifying the adjacent non-tangent faces of a computational solid model of a bucket blade, then executing a system function that adds a tangent blend between the adjacent faces. The subject faces are that of the vane surface at its root (or base) and the dovetail platform to which it is attached.
One problem with using either the CAD system or the CAM system to generate the fillet surface for blending the airfoil surface to the platform is that the solution provided by these systems typically assumes a single fixed radius blend and an unrestricted platform size. Assuming a single fixed radius blend and an unrestricted platform size results in a fillet surface that is undesirable. In the application of long bucket blades it is undesirable to have a fillet blend of constant (single fixed) radius. Compound (multiple radii) blends are required in order to separate centrifugal and tangential vane stresses at the root. Also, assuming an unrestricted platform size results in a fillet surface that is truncated and disrupts smooth steam flow at the root of the steam path. Since the fillet surface is undesirable, a skilled artisan has to usually finish the surface to meet the design requirements. Associated with adding a compound (multiple radii) blend is the preparation of the vane surface. The vane surface must be largely free of inflections, voids and reversing curvatures that will interfere or perhaps prevent the computation of a tool path by subsequent CAM software. CAD systems require a labor intensive process of analysis and editing, to identify and remedy the aforementioned surface anomalies. Therefore, there is a need for a system and method that can generate a fillet surface for blending the airfoil surface to a restricted platform with multiple varying radii.
BRIEF SUMMARY OF THE INVENTION
This invention is able to generate a fillet surface for blending the airfoil surface to a restricted platform with multiple varying radii by acquiring descriptions of an airfoil shape (e.g., the pressure side, the leading edge, the suction side and the trailing edge), a platform surface, a platform footprint, and filleting curves for the pressure and suction sides of the airfoil. The invention uses these descriptions to produce a smooth mesh of points which capture both the blending fillet surface and the airfoil. The invention uses the smooth mesh of points to render slope-continuous blended fillet surfaces. A CAD system or a CAM system receives the slope-continuous blended fillet surfaces in digital form. A manufacturing process such as a numerically controlled (NC) machining operation then machines the blended fillet surfaces according to the digital expression provided by the CAD or CAM system.
In accordance with this invention, there is provided a system, a method and an article of manufacture for generating a blending fillet surface between a platform and an airfoil mounted thereto. In this invention, a memory stores a user-specified airfoil shape for the airfoil comprising a plurality of section curves substantially parallel to each other and each having a leading edge, a trailing edge, a pressure side, and a suction side, a platform surface, and a platform footprint for the platform. A processor coupled to the memory, generates the blending fillet surface. The processor comprises means for extracting the plurality of section curves, the platform surface, and the platform footprint from the memory. A generating means generates a plurality of vertically oriented curves crossing through each of the plurality section curves. A specifying means specifies a first multi-segment fillet profile curve for blending the pressure sides of the plurality of section curves to the platform and a second multi-segment fillet profile curve for blending the suction sides of the plurality of section curves to the platform. A determining means determines a position for placing both the first and the second multi-segment fillet profile curves about each of the plurality of vertically oriented curves. A placing means places the first and the second multi-segment fillet profile curves about the pressure sides and the suction sides of each of the plurality of section curves. A generating means generates a plurality of blending curves about the leading edges and the trailing edges of each of the plurality of section curves. A rendering means renders the blending fillet surface from the first and the second multi-segment fillet profile curves and the plurality of blending curves.
REFERENCES:
patent: 5345546 (1994-09-01), Haranda et al.
patent: 5774359 (1998-06-01), Taneja
patent: 5793373 (1998-08-01), Sekine et al.
Caruso David Alan
Hinds John Knox
Nelson Garth M
Breedlove Jill M.
General Electric Company
Goldman David C.
Heckler Thomas M.
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