Perimeter-cooled stage 1 bucket core stabilizing device and related method

Abstract

A core for use in casting a gas turbine bucket, the core comprising a solid upper body portion and a pair of legs extending downwardly from the solid upper body portion, the pair of legs separated by an elongated slot, and a pair of pegs projecting axially from opposite sides of the upper body portion, above the elongated slot but spaced from an upper edge of the upper body portion.

Description

BACKGROUND OF INVENTION [0001] This invention relates generally to the casting of perimeter-cooled buckets for a gas turbine and, more specifically, to a stabilization device for an internal core used in the bucket casting process. [0002] In an effort to improve the cooling scheme of a stage 1 gas turbine bucket, a “pants-leg” shaped core has been used in the bucket shank portion of the shell die to form a pair of cooling passages in place of a previous design utilized to form a plurality of radial cooling holes. In the casting process, however, the core tended to drift significantly, resulting in wall thicknesses in the shank portion of the bucket being out of tolerance. [0003] Core stabilizing devices or “printouts” for improving the yield of a bucket casting process have been previously used in stage 2 buckets, but with a different core design and in a different location relative to the so-called angel wings on the exterior of the shank portion of the bucket. Because of the diffe...

AI Technical Summary

Benefits of technology

[0005] It is also a feature of the present invention that the cross sectional shape of the stabilization devices or printouts is of elliptical rather than the oblong or rounded rectangular shape used with the printouts for the casting of stage 2 buckets. By making the printouts elliptical in cross-sectional shape, the flat surfaces of the prior design have been eliminated, and stresses, particularly at the intersection of the printouts and the core, have been reduced.

Problems solved by technology

In the casting process, however, the core tended to drift significantly, resulting in wall thicknesses in the shank portion of the bucket being out of tolerance.

Because of the different design of the stage 1 and stage 2 buckets, it was not possible to simply scale up the stage 2 bucket core for use in the stage 1 bucket casting process.

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