Arrangement for cooling a component in the hot gas path of a gas turbine

Abstract

A cooled wall segment in the hot gas path of a gas turbine. The wall segment includes a first surface, exposed to a medium of relatively high temperature, a second surface, exposed to a medium of relatively low temperature, and side surfaces connecting the first and second surface and defining a height of the wall segment. At least one cooling channel for a flow-through of a fluid cooling medium extends through the wall segment. Each cooling channel is provided with an inlet and an outlet for the cooling medium. The at least one cooling channel includes at least two heat transfer sections, a first heat transfer section extending essentially parallel to the first surface at a first distance from the first surface and a second heat transfer section extending essentially parallel to the first surface at a second distance, whereby the second distance is less than the first distance.

Claims

1. A wall segment for a hot gas path of a gas turbine, comprising a first surface, exposed to a medium of a first temperature, a second surface, exposed to a medium of a second temperature that is lower than the first temperature, and side surfaces connecting said first and said second surface and defining a height of the wall segment, at least one cooling channel for a flow-through of a fluid cooling medium extending through the wall segment, each cooling channel being provided with an inlet for the fluid cooling medium and an outlet for the fluid cooling medium, wherein the at least one cooling channel comprises, a first heat transfer section extending essentially parallel to the first surface at a first distance from the first surface, a second heat transfer section extending essentially parallel to the first surface at a second distance from the first surface, whereby the second distance is less than the first distance, and a transition section in which a distance between a lower surface of the transition section and the first surface varies.

2. The wall segment according to claim 1, wherein the at least one cooling channel comprises, in succession in the direction of flow of the fluid cooling medium, an inlet section for the fluid cooling medium, the first heat transfer section extending essentially parallel to the first surface of the wall segment in the first distance, the transition section with a direction vector towards the first surface, the second heat transfer section extending essentially parallel to the first surface in the second distance and an outlet for the fluid cooling medium.

3. The wall segment according to claim 1, wherein the medium of the second temperature is the fluid cooling medium, preferably cooling air.

4. The wall segment according to claim 1, wherein the inlet is arranged on the second surface, exposed to the medium of the second temperature.

5. The wall segment according to claim 1, wherein the first section of the at least one cooling channel, running in a first distance essentially parallel to the surface, and the second section, running in a second distance essentially parallel to the surface, run parallel to each other.

6. The wall segment according to claim 5, wherein said first section and the second section run parallel to each other with an opposite flow direction of the fluid cooling medium.

7. The wall segment according to claim 2, wherein the transition section comprises two one-quarter bends.

8. The wall segment according to claim 2, wherein the transition section has a component in the vertical direction towards the first surface and has a component in the horizontal direction.

9. The wall segment according to claim 1, wherein the wall segment comprises two or more of cooling channels, whereby at least two cooling channels are arranged laterally reversed to each other.

10. The wall segment according to claim 1, wherein the second surface of the wall segment, exposed to the medium of the second temperature, is configured to follow a structure of the cooling channels inside.

11. The wall segment according to claim 1, wherein the at least one cooling channel has a rectangular cross-section.

12. The wall segment according to claim 1, wherein the at least one cooling channel has a trapezoidal cross-section, whereby the base of the trapezoid is directed to the first surface, exposed to the medium of the first temperature.

13. The wall segment according to claim 1, wherein the cross-sectional shape of at least one cooling channel is changing over the length.

14. The wall segment according to claim 1, wherein the at least one cooling channel is partly or completely equipped with heat transfer enhancing means.

15. The wall segment according to claim 14, wherein the heat transfer enhancing means are ribs.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is now explained more closely by means of different embodiments and with reference to the attached drawings.

(2) FIG. 1 schematically shows in a perspective view the basic features of a wall segment with an integrated cooling channel according to the invention;

(3) FIG. 2 shows in a similar view a wall segment with two cooling channels in laterally reversed arrangement;

(4) FIG. 3 shows in a cross-sectional view an embodiment of the invention;

(5) FIG. 4 shows in a cross-sectional view an embodiment of the invention;

(6) FIG. 5A shows in a cross-sectional view an embodiment of the invention;

(7) FIG. 5B shows in a cross-sectional view an embodiment of the invention;

(8) FIG. 6 shows in an embodiment cooling channels equipped with heat transfer enhancing means;

(9) FIG. 7 shows a stator heat shield equipped with a plurality of laterally reversed arranged cooling channels.

DETAILED DESCRIPTION

(10) FIG. 1 schematically shows a stator heat shield 10 of a gas turbine, with a first inner surface 11 exposed to the hot gases in the hot gas path of the gas turbine, a second outer surface 12 (see FIGS. 3-5) and four side surfaces 13. At least one cooling channel 14 for a cooling medium 15, usually cooling air, is extending inside the heat shield 10. The inlet opening 16 to pass the cooling medium 15 into the cooling channel 14 is positioned on the outer surface 12 of the heat shield 10. FIG. 1 shows in an exemplary manner a fluid inlet 16 orthogonally to the outer surface 12, but of course an inclined orientation of inlet 16 is also possible. The inlet 16 is arranged close to the side face to have a heat transfer section as long as possible. Usually, the distance to the side face may be in the range of 5% to 20% of the length of the wall segment 10. In a defined first distance 19 to the inner surface 11 the inlet section 16 ends in a first heat transfer section 18 with an orientation essentially parallel to the inner surface 11. This section 18 acts as the first heat transfer section of the cooling channel 14. At the end of this section 18 a transition section 20 follows. It is the purpose of this section 20 to transfer the cooling channel 14 onto a second plane closer to the hot gas loaded inner surface 1. Preferably in two one-quarter bends the cooling channel 14 moves into another plane closer to surface 11 and changes its flow direction into the opposite direction. Afterwards a second heat transfer section 22 follows, extending longitudinally through the heat shield 10 and in a constant distance 23 to the hot gas loaded inner surface 11. This section 22 is generally parallel to the longitudinally extending first heat transfer section 18, but extending in a plane closer to the surface 11. This part of the cooling channel 14 is the main contributor to the cooling of the hot gas loaded surface 11. At a side surface 13 the used cooling medium 15 exits the heat shield segment 10 through an outlet 17.

(11) The parallel heat transfer sections 18 and 22 of the cooling channel 14 may be arranged in a vertical line or staggered, as described later in more detail shown in FIGS. 3 and 4.

(12) Usually a stator heat shield is equipped with two or more cooling channels 14. According to a preferred embodiment in each case two cooling channels 14′, 14″ are laterally reversed arranged, as sketched in FIG. 2. Both cooling channels 14′, 14″ comprise an inlet 16 for the cooling medium 15, a first heat transfer section 18 with a first distance 19 to the hot gas loaded surface 11, a transition section 20 with a direction vector towards the surface 11, a second heat transfer section 22, essentially parallel to surface 11 and adjacent outlets 17 for the cooling medium 15 at the side surface 13. The transition sections 20 of the both channels 14′, 14″ have a component in the vertical direction towards the hot gas loaded surface 11 and have a component in the horizontal direction. The horizontal components are directed towards each other. As a consequence, the second heat transfer section 22 of cooling channel 14′ is positioned in a vertical line with the first heat transfer section 18 of cooling channel 14″, and the second heat transfer section 22 of cooling channel 14″ is positioned in a vertical line with the first heat transfer section 18 of cooling channel 14′ (q.v. FIG. 3).

(13) The sketches of FIGS. 4, 5A and 5B show in a cross-sectional view alternative embodiments, whereby in each case the first heat transfer section 18 and the second heat transfer section 22 of the cooling channels 14 are staggered. Preferably the cooling channels 14 are equipped with a rectangular or trapezoidal flow cross-section.

(14) According to an alternative embodiment the cross-sectional shape of the cooling channels 14 may change over the length, e.g. from a trapezoidal cross-section to a rectangular cross-section (FIG. 5A). According to an additional embodiment the second surface 12 of the stator heat shield 10 (this surface 12 is usually exposed to the cooling medium 15) is configured with a structure 24 following the structure of the cooling channels 14 inside. This measure improves the ratio of cold to hot metal volume which in turn is beneficial for the cyclic lifetime of the component 10. In addition, this design reduces the mass of the wall segment 10 and thereby, when produced by an additive manufacturing method, such as selective laser melting (SLM), this design reduces the manufacturing of these parts in price. In a preferred embodiment, as shown in FIG. 6, the cooling channels 14′, 14″ are equipped with heat transfer enhancing means 25, preferably ribs. Especially these heat transfer enhancing means 25 are arranged in the second heat transfer section 22 close to the hot gas loaded surface 11.

(15) FIG. 7 shows an embodiment of a stator heat shield 10 with a plurality of inner cooling channels 14. The cooling channels 14, 14′, 14″ are in each case arranged in pairs, as shown in detail in FIG. 2.