JPH10196304A - Device to cool wall surrounded with flow on both sides - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a cooling means, perform casting of a pin togetherwith a blade when a wall to be cooled is a cast turbine blade, and provide a means to allow constitution convenient to the efficiency of the rear edge of the blade. SOLUTION: A wall W to be cooled has the outside surrounded with a flow of a heating medium and the inside surrounded with a flow of a cooling medium. In a so formed cooling device, a plurality of thermal bridges in the shape of a pin S having high thermal conductivity and slight solubility is arranged. The pin is thrust in a space E on which a load is exerted by a cooling medium. The pin S is formed favorably of a synthetic diamond formed of isotope and cast togetherwith the wall W.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a device for cooling a wall (W) surrounded by a flow of a hot medium on the outside and a flow of a cooling medium on the inside.

[0002]

2. Description of the Related Art A wall to be cooled of this kind is formed, for example, as an internally cooled blade of a turbomachine, in particular of an axial gas turbine.

[0003] Hollow turbine blades internally cooled by liquid, steam or air as a cooling medium have been known for a long time. Particularly problematic in this case is the cooling of the trailing edge of such a blade, which is passed by a cooling medium in a closed circuit. The wall forming the trailing edge has a narrow gap from which heat can be dissipated. For this, the width of the narrow gap must not be less than a predetermined minimum. To avoid overheating of the trailing edge, there must not be a large accumulation of material. In addition, the wall thickness must not be less than the specified dimensions for strength reasons. In order to meet these conditions, internally cooled blades have a large radius at the trailing edge, which adversely affects blade efficiency.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a device on an internally cooled wall for improving heat dissipation, particularly from narrow gaps.

[0005]

According to the present invention, there is provided, according to the present invention, a method in which a wall surrounded by a flow of a cooling medium is provided with a shape of a hardly soluble pin having high thermal conductivity. The solution is that a plurality of thermal bridges are arranged, the pins protruding into the space loaded by the cooling medium.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention are as described in claim 2 and the following.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention for an internally cooled gas turbine blade will be described with reference to the drawings.

The drawings show only those elements which are important for an understanding of the invention. The direction of flow of the media involved is indicated by arrows.

The cast blade shown in FIG. 1 has three internal chambers a, b, c, which are passed perpendicularly to the plane of the drawing by a cooling medium, for example steam. In that case, the cooling medium flows along the inside of the wall W forming the blade contour (the hot gas flows through the outer periphery of this wall),
Heat is removed from the walls by the cooling medium. In at least the front two chambers a, b, auxiliary means, not shown, such as guide ribs, flow channels, impact cooling inserts and the like, can be provided for improving wall cooling. In the case of the present embodiment, the cooling medium is circulated in a closed circuit, so that the blowing of the cooling medium into the flow passage in the region of the trailing edge as well as the leading edge, the suction side, the discharge side. Not done.

This creates problems with the geometry of the trailing edge. This will be described with reference to FIG.
The narrow gap E formed by the wall must have a minimum size in order to be able to receive sufficient cooling medium for the discharge of the attacking heat. Therefore, the inner radius of the edge is formed to have a diameter d. For reasons of strength, the wall thickness T must not fall below a minimum value.
In order to avoid overheating of the trailing edge, no significant material accumulation should occur at this point. The dimension La therefore generally corresponds to the wall thickness T. From all this, the outer radius of the edge is formed to have a relatively large diameter Da. This is known for trailing edges to be cooled.

The present invention provides a solution starting from here. According to FIG. 3, a plurality of thermal bridges in the form of pins S are arranged for improved heat dissipation in the wall surrounded by the flow of the cooling medium. These pins provide a space to be loaded by the cooling medium, in other words, a narrow gap E
It is provided so as to rush into the inside.

[0012] For manufacturing reasons, the thermal bridge is made of a poorly soluble material. Because such internally cooled vanes are generally manufactured by casting, it is proposed that the pins be pre-arranged in a casting core and cast integrally with the vanes. The advantage of this is that common spacers in the form of quartz or aluminum alloy struts can be omitted in this area.

As can be seen from FIG. 3, if the wall thickness T does not change from the conventional one and the roundness d inside the edge does not change from the conventional one, a relatively large material having the dimension Ln of the trailing edge as compared with the conventional one Integration is possible. This allows the formation of a very sharp trailing edge, which is the outer diameter D of the edge.
This is excellent in that n is relatively small.

To ensure the desired heat dissipation, pins with a high thermal conductivity are selected. Synthetic diamond is recommended as a suitable material for this. Synthetic diamond consisting of isotope C-14 is particularly advantageous with regard to thermal conductivity.

The pin S is formed, for example, in a cylindrical shape. Of course, other geometries with relatively large heat exchange surfaces are also possible, for example pins with a polygonal cross section or toothed pins may be used.

Given conditions, in other words: trailing edge geometry and wall thickness; geometry of the narrow gap to be passed by the cooling medium; heat load on the blade trailing edge; type of cooling medium;
In terms of temperature and flow rate, the thermal conductivity of the selected pin material and the exchange surface which penetrates into the narrow gap through which it flows is a measure of the number of pins to be used over the blade height.

According to FIG. 4, the arrangement of the pins in a stepwise and regular manner in the radial direction over the height of the blades results in a rear chamber c.
Is shown in vertical section. It is of course possible to arrange the pins at a non-uniform pitch depending on the heat load over the blade height, or to arrange the pins with different heat exchange surfaces at the same pitch.

It goes without saying that the invention is not restricted to the embodiment shown. In contrast to the illustrated embodiment, the cooling of the other blade parts in any new way, which is also a problem due to the large material accumulation which must also dissipate heat, for example, the area of the blade base or blade tips, Of course, it is also possible. Furthermore, the invention is not restricted to vanes or narrow gaps, but rather can be applied to all elements that are surrounded by a medium flow and to be cooled.

[0019]

An advantage of the present invention is, in particular, that the means is simple. If the wall to be cooled is a cast turbine blade, the pins can be cast with the blade. This measure also allows an advantageous configuration of the trailing edge of the blade.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a blade.

FIG. 2 is a detailed view of a portion surrounded by an alternate long and short dash line z in FIG. 1 having a trailing edge based on a known technique.

3 shows a trailing edge according to the invention in the same way as in FIG. 2;

FIG. 4 is a longitudinal sectional view of a trailing edge region of a blade according to the present invention.

[Explanation of symbols]

a, b, c Inner chamber of blade, d Roundness inside edge, D
a and the diameter of the outer roundness of the Dn edge, E a narrow gap,
La and Ln dimensions of material accumulation, S pin for cooling, T wall thickness, W wall to be cooled

Claims (6)

[Claims] An apparatus for cooling a wall (W) surrounded by a flow of a hot medium on the outside and a flow of a cooling medium on the inside, wherein the wall surrounded by the flow of the cooling medium has high thermal conductivity. A plurality of thermal bridges in the form of hardly soluble pins (S) are arranged, and these pins protrude into the space (E) loaded by the cooling medium, on both sides. A device for cooling a wall surrounded by a flow. 2. Apparatus according to claim 1, wherein the pin (S) comprises a synthetic diamond comprising the isotope C-14. 3. The device according to claim 1, wherein the pin (S) is cast with the wall (W). 4. The space loaded by the cooling medium is:
2. The device according to claim 1, comprising at least in part a closed narrow gap formed by the wall to be cooled itself. 5. The device according to claim 4, wherein the narrow gap (E) is formed by the trailing edge of the internally cooled vanes of the turbomachine. 6. The method according to claim 5, wherein the narrow gap extends at least approximately over the entire height of the turbomachine blade, and a number of pins are distributed over this height. apparatus.