Aft frame with oval-shaped cooling slots and related method

Abstract

An aft frame adapted to interface between a combustor transition piece and a first stage turbine nozzle includes: a closed-periphery frame comprised of a top, bottom and pair of side walls. A plurality of cooling holes or apertures having elliptical or oval cross-sectional shapes are provided in one or more of the top, bottom and pair of side walls, extending axially through the closed-periphery frame. The cooling holes have major and minor axes arranged such that the major axes are substantially parallel with the top and bottom walls.

Description

This invention relates to turbine cooling technology and, more specifically, to the cooling of an aft frame component interfacing between the combustor transition piece and a stage 1 turbine nozzle.

BACKGROUND OF THE INVENTION

A “transition piece” as understood in the context of a can-annular combustor for a power generating gas turbine, is a duct that connects the combustor liner with the first stage nozzle of the turbine. The aft frame is a component which is located at the exit end of the transition piece and thus acts as an interface between the transition piece and the stage 1 nozzle. It is exposed to hot gases flowing into the stage 1 nozzle and therefore, cooling of the aft frame component is of concern.

More specifically, hot gases flowing through the transition piece recirculate in a groove between the aft frame and the stage 1 nozzle, causing high thermal gradients. Accordingly, effective cooling needs to be provided on the trailing face of the aft frame, i.e., that side of the frame facing the stage 1 nozzle. Currently, typical aft frame configurations incorporate cooling holes with circular cross sections in order to divert a portion of flow through an impingement sleeve (which surrounds the transition piece) into these holes to cool the aft frame.

There remains a need, however, for more effective cooling of the aft frame of the transition piece.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with an exemplary but non-limiting embodiment of this invention, oval or elliptical-shaped cooling holes are provided about the periphery of the aft frame. Because oval or elliptical-shaped holes provide more surface area for effective convection cooling for a given cross-sectional area, cooling of the aft frame is improved.

Accordingly, in one aspect, the invention relates to an aft frame adapted to interface between a combustor transition piece and a first stage turbine nozzle comprising: a closed-periphery frame comprised of a top, bottom and pair of side walls; and a plurality of cooling apertures extending through one or more of the top, bottom and pair of side walls, the cooling apertures having an elliptical or oval cross-sectional shape.

In another aspect, the invention relates to an aft frame adapted to interface between a combustor transition piece and a first stage turbine nozzle comprising: a closed-periphery frame comprised of a top, bottom and pair of side walls; and a plurality of cooling apertures having an elliptical or oval cross-sectional shape provided in each of the top, bottom and pair of side walls, extending axially through the frame; and wherein the cooling apertures have major and minor axes, arranged such that the major axes are substantially parallel with the top and bottom walls.

In still another aspect, the invention relates to a method of forming a turbine aft frame adapted to interface between a combustor transition piece and a first stage turbine nozzle comprising: a) providing a closed periphery aft frame having top and bottom and a pair of side walls; and b) forming elliptical-shaped cooling holes in at least one of said top, bottom and pair of side walls, extending axially through the aft frame.

The invention will now be described in more detail in connection with the figures identified below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a typical transition piece aft frame of known construction;

FIG. 2 is an enlarged detail showing known circular cooling holes or slots formed in the aft frame; and

FIG. 3 is an enlarged detail illustrating the oval or elliptical shape of the cooling holes to be employed in an aft frame of, for example, the type shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, an aft frame 10 that serves as an interface between a conventional transition piece (not shown) and a first stage turbine nozzle (also not shown) includes top and bottom walls 12, 14, respectively and a pair of side walls 16, 18 that complete the closed-periphery frame. Mounting hardware, such as brackets 20 and 22, facilitate connection of the aft frame to the first stage turbine nozzle. The exact manner of attachment is not part of this invention, however, and in any event, any suitable attachment technique may be employed. It will be appreciated that a conventional transition piece is attached to the opposite side of the aft frame, extending between the first stage nozzle and the combustor liner. Examples of this type of arrangement may be found in U.S. Pat. Nos. 6,412,268 and 6,547,257.

With reference now to FIG. 2, circular cooling holes 24 are typically spaced about the periphery of the aft frame, allowing cooling air to flow axially into the holes and through the aft frame, thereby cooling the frame.

FIG. 3 illustrates a modified cooling hole shape that provides better and more efficient cooling of the aft frame. Specifically, some or all of the axially extending cooling holes or apertures 26 have an elliptical or oval cross-sectional shape, thus increasing the surface area for more effective convection cooling for a given cross-sectional area. Elliptical cooling holes or apertures 26 may be used exclusively or in combination with circular cooling holes (e.g., holes 24) as determined by specific cooling requirements. Dimensions for the elliptical holes may also vary in accordance with cooling requirements. The elliptical cooling holes 26 may be provided in any one or more (or all) of the top, bottom and side walls 12, 14, 16 and 18, respectively, of the aft frame. Preferably, the major axes of the cooling apertures are substantially parallel to the top and bottom walls of the aft frame.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. An aft frame adapted to interface between a combustor transition piece and a first stage turbine nozzle comprising:

a closed-periphery frame comprised of a top, bottom and pair of side walls; and a plurality of cooling apertures extending through one or more of said top, bottom and pair of side walls, said plurality of cooling apertures having an elliptical or oval cross-sectional shape.

2. The aft frame of claim 1 wherein one or more of said plurality of cooling apertures are provided in each of said top, bottom and pair of side walls.

3. The aft frame of claim 1 wherein said plurality of cooling apertures extend in an axial direction through said closed-periphery frame.

4. The aft frame of claim 2 wherein said plurality of cooling apertures extend in an axial direction through said closed-periphery frame.

5. The aft frame of claim 1 wherein said plurality of cooling apertures have major and minor axes, arranged with said major axes substantially parallel with said top and bottom walls.

6. The aft frame of claim 4 wherein said plurality of cooling apertures have major and minor axes, arranged with said major axes substantially parallel with said top and bottom walls.

7. An aft frame adapted to interface between a combustor transition piece and a first stage turbine nozzle comprising:

a closed-periphery frame comprised of a top, bottom and pair of side walls; and a plurality of cooling apertures having elliptical or oval cross-sectional shapes provided in each of said top, bottom and pair of side walls, extending axially through said closed-periphery frame; and

wherein said plurality of cooling apertures have major and minor axes, arranged such that said major axes are substantially parallel with said top and bottom walls.

8. A method of forming a turbine aft frame adapted to interface between a combustor transition piece and a first stage turbine nozzle comprising:

a) providing a closed periphery aft frame having top and bottom walls and a pair of side walls, and

b) forming elliptically-shaped cooling holes in at least one of said top, bottom and pair of side walls, extending axially through the aft frame.

9. The method of claim 8 including providing said elliptically-shaped cooling holes in all of said top, bottom and pair of side walls.

10. The method of claim 8 wherein said elliptically-shaped cooling holes have major and minor axes, and wherein step b) includes arranging said elliptically-shaped cooling holes with said major axes substantially parallel to said top and bottom walls.