Apparatus and methods for cooling slot step elimination

Abstract

An airfoil core die includes a tab for forming a continuous and smooth contour and extension of a first trailing edge slot recessed all to a bottom of the airfoil. The contour is formed on each airfoil core at injection and is maintained through to finish casting of the airfoil.

Description

BACKGROUND OF THE INVENTION[0001]This invention relates generally to turbine engines and, more particularly, to apparatus and methods for reducing stress on turbine blades.[0002]Turbine blades include an airfoil, a platform, and a shank. The airfoil has a leading edge and a trailing edge, with the trailing edge being relatively thin in comparison to the leading edge. Typically turbine blades are subjected to high temperature gases by a combustor located upstream from the turbine blades. The airfoil trailing edge region is exposed to such high temperature gases and is prone to failure due to difficulties associated with providing adequate cooling to the region.[0003]To facilitate preventing airfoil failure, a plurality of slots are located in the airfoil trailing edge and cool air is discharged from the slots to cool the trailing edge. These slots sometimes are referred to herein as trailing edge slots.[0004]Turbine engine airfoils are cast with land areas, or ribs, located between t...

AI Technical Summary

Benefits of technology

[0008]More specifically, the die includes a tab positioned such that a continuous and smooth contour is formed from the first trailing edge slot recessed wall to a juncture of the airfoil and the platform at the filled. Once the tab is cast onto the airfoil core die, the first step, which is typically located near the juncture of the airfoil and an airfoil platform, is partially eliminated. The elimination of at least a portion of the step reduces stress concentration, potential early fatigue and blade failure. The step is sometimes referred to herein as a ledge.

[0009]Utilizing the above described tab with the airfoil core die improves the longevity and performance of the turbine blade by reducing the fatigue of the airfoil at the first trailing edge slot. The tab provides a consistently smooth and continuous contour from the airfoil first trailing edge slot to the junction of the airfoil and the airfoil platform.

Problems solved by technology

The airfoil trailing edge region is exposed to such high temperature gases and is prone to failure due to difficulties associated with providing adequate cooling to the region.

The step in the slot located closest to the platform may cause a large stress concentration with high terminal stresses present.

The high thermal stresses may result in trailing edge axial cracks which can propagate through the airfoil.

Premature failure of the turbine blade may result form the axial cracks.

However, the trailing edge slot located closest to the airfoil platform cannot be eliminated because removal would result in trailing edge overheating.

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