EP1445423A2 - Cooled turbomachine blade - Google Patents

Abstract

The blade has pins (23) of high thermal conductivity along the trailing edge (14), alternating with blow-out apertures (22) in the trailing edge material (141). The pins project into the trailing edge cooling channel (12), conducting heat from the trailing edge material to improve the cooling of the trailing edge without increasing the number of blow-out apertures.

Description

Technical field

The present invention relates to a coolable turbomachine blade according to the preamble of claim 1.

State of the art

The efficient cooling of the thermally highly stressed components of a gas turbine is an indispensable condition for the operation of modern machines. Accordingly, the cooling methods have developed rapidly.

The simplest form of cooling is convection cooling, in which one Coolant flows over a surface of a component, and this heat deprives while another surface with a heat input is applied. A particular disadvantage of convection cooling is that that all the heat to be dissipated through the component wall must be transported. The area exposed to the heat input is at a much higher temperature than the cooled surface. moreover become significant temperature gradients over component walls and thus Thermal stresses caused.

The film cooling known from US 3,527,543 was therefore used for a long time preferred in which a coolant - preferably air coming from the compressor is removed, or steam - through the component wall from one Cold gas side flows to the hot gas side to which hot gas is applied. there On the one hand, the coolant absorbs heat from the material while it is flows through the blow-out openings. On the other hand, a film lays down relatively cool medium over the hot gas side of the component, and protects it direct contact with the hot medium. You misplace yourself with modern gas turbines completely on film cooling, the rises Coolant consumption, however, by mass. EP 750 957 issues one several material layers objected to by one another Component wall, which has cooling air openings. The single ones Material layers are connected to each other by thermally conductive pins.

The development is therefore increasingly in the direction of the coolant to be used for efficient convection cooling before blowing out. at the impingement cooling, which emerges, for example, from DE 44 30 302, does this Coolant at the highest possible speed on the component to be cooled, whereby the convective heat transfer from the component to the coolant is intensified. The good cooling effect is however comparatively bought high pressure losses on the cooling side.

Furthermore, the impingement cooling cannot be used everywhere without further ado. issues arise especially in the area of the blade trailing edges due to the geometric design. On the other hand, there is good cooling there of the material necessary because the surface exposed to the hot gas in the Large compared to the material thickness and the surface of the cold gas side however, is relatively small. Practice also shows that it is actually very problematic in such a closed structure Gaps as they exist on the cooling side in the area of the rear edge flow through. The inner walls of the hollow component abut in this area at an acute angle to each other, and the flow boundary layers on the cooling side grow together. The flow velocity in the Narrow gap becomes very small, and the coolant flow becomes different displaced the interior of the component. Improving the convective Cooling effect, are therefore due to the displacement effect Flow boundary layers set narrow limits.

The most common and safest way of cooling blade trailing edges at least air-cooled gas turbines, is still the rear edge blowout, which is very much based on film cooling, and often a little inaccurate too is included under this collective term. Coolant flows here through a number of openings in the trailing edge, taking Heat from the material of the blade. Due to the introduction of the Blow out openings in the trailing edge will cause convection through the narrow Forced cooling gap, such that cited above Displacement phenomena do not occur. On the other hand, the Center distance between two cooling openings on the rear edge to be small, and If possible, do not exceed eight hydraulic diameters of the openings. This interpretation guideline ensures that the Use of conventional blade materials to measure the temperature variation along the Blade trailing edge remains within reasonable limits, and local Overheating can be avoided. In the sum of all Blow-out openings give a rear edge blow-out a large one Flow cross-section free, and contributes a significant proportion to consumption of coolant, which is there in the interest of increasing efficiency minimize applies.

This results in the situation that due to special fluid mechanical Conditions inside a turbine blade use convective Cooling methods for rear edge cooling is restricted. The Rear edge blow-out, on the other hand, has negative effects on coolant consumption Effects on the efficiency of the gas turbine cycle.

DE 196 54 115 therefore proposes the cooling of Bucket trailing edges to dispense with the trailing edge blow-out, and instead insert its thermally highly conductive pins into the trailing edge material, which pins protrude into the interior of the blade through which coolant flows. This is intended to transport heat to and from the trailing edge material the cooling air flow are released. The pins work in this case if they are cooled sufficiently well by the coolant as heat sinks in the base material of the shovel. However, this is already the case here discussed problem that in the area of the trailing edge at the acute angle tapering inner walls, the flow boundary layers grow together, and displaces the cooling flow into other areas of the blade interior becomes. The pins increase the blockage of the cooling channel again, and will ultimately, the cooling air does not flow around in the desired amount, that the heat transfer from the pins to the cooling medium is restricted and a sub-optimal heat sink effect of the pins results.

GB 2 117 455 specifies a coolable component in which one on the cold gas side Turbine blade in the area of the blade leading edge thermally highly conductive Protrude pins into a cooling channel. Are on the same cooling channel Blow-out openings arranged, through which cooling fluid to the blade outside can flow out. The pins are along a first in the direction the blade height line, and the blow-out openings are along a second, different from the first, towards the Bucket height extending line arranged. As a result, certain areas of the component purely through the heat dissipation via the pins and other areas purely on the heat absorption of the flowing Coolant to be cooled.

Presentation of the invention

The object of the present invention is to provide a turbomachine blade Specify the type mentioned above, which the disadvantages of the prior art Technology avoids. In particular, it is an object of the present Invention, a turbomachine blade of the type mentioned above indicate that an improved cooling effect on the thermally particularly loaded blade trailing edge is achieved.

According to the invention this is due to the totality of the features of the Claim 1 reached.

The essence of the invention is that the turbomachine blade is thermal has highly conductive pins and blow-out openings, through which in operation at least a part of said second medium from the cold gas side to The hot gas side flows in such a way that both the pins and the Blow out openings act as heat sinks, and that on the cold gas side alternately along at least one pin and at least one opening the blade trailing edge are arranged. With a corresponding Pressure drop between the two flow media results from the additional insertion of blow-out openings even in a narrow gap a forced convection flow, the coolant around the pins round lead. This is part of the heat rather than the heat generated by the Blow-out coolant flowing through the thermal highly conductive pins led out of the material, thus the Coolant consumption restricted. The limitation of Coolant consumption has a very positive effect on the Efficiency when compressor air is used for cooling purposes. The Effect can be improved if arranged on the cold gas side Guides the coolant flowing to the blow-out openings over the Steer heat conducting pins.

When using the cooling configuration according to the invention, fewer are used Openings are required than in the case of pure cooling by means of blow-out, which means that Coolant consumption is reduced. On the other hand, since the thermal pins Extract heat from the material, i.e. the heat sink distribution in the component is kept constant, the temperature distribution in the component is not uneven.

For a minimized coolant consumption, the alternating Arrangement of two pins and one blow-out opening are suitable, the opening is expediently arranged centrally between two pins. In order to achieve a temperature distribution that is as homogeneous as possible the alternating arrangement of a pin and an opening be appropriate. An equidistant arrangement of pins and openings will also help in the vast majority of cases Temperature differences within the trailing edge of a blade to minimize the predetermined total blow-out cross-section. It will be in mind a uniform temperature distribution in the trailing edge of the blade, if the distance between two heat sinks is not more than eight hydraulic diameter of a blow-out opening. In the same The pins should be more or less connected with their longitudinal axes be arranged parallel to the blow-out openings so that the heat flow always runs in the same direction.

To achieve the desired effect, the thermal conductivity of the Material from which the pins are made should be as high as possible, and should be have at least three times the value of the base material. Also the The melting point of the material must of course be sufficiently high. Materials that are suitable for the production of the thermal pins for example tungsten, silver, or very particularly diamond. The pencils must have the best possible heat transfer to the base material, what can be realized by being cast in the components become. But you should not under any circumstances the complete material thickness of the Penetrate the component from the cold gas side to the hot gas side to avoid any to create disadvantageous thermal bridges. The pens are so advantageous deep into the base material as it is 30% to 80% of the material thickness equivalent. On the one hand, this ensures a large heat exchange surface, on the other hand, the formation of thermal bridges is avoided. Farther of course, the thermal pins must have a certain axial dimension in protrude the coolant.

Brief description of the drawing

Figur 1 eine erste bevorzugte Ausführungsform der Erfindung zur Kühlung der Hinterkante einer Gasturbinenschaufel;

Figur 2 eine Draufsicht auf die in Fig. 1 dargestellte Gasturbinenschaufel;

Figur 3 eine weitere bevorzugte Ausführungsform der Erfindung zur Kühlung der Hinterkante einer Gasturbinenschaufel; und

Figur 4 und 5 Beispiele für mögliche Varianten der Gestaltung der Wärmeleitstifte.

The invention will be explained below with reference to exemplary embodiments shown in the drawing. Show in detail

1 shows a first preferred embodiment of the invention for cooling the rear edge of a gas turbine blade;

FIG. 2 shows a top view of the gas turbine blade shown in FIG. 1;

FIG. 3 shows a further preferred embodiment of the invention for cooling the rear edge of a gas turbine blade; and

Figures 4 and 5 examples of possible variants of the design of the heat-conducting pins.

The embodiments shown in the drawing are merely instructive in nature, and are not intended to limit the Serve subject of the invention. The invention is not by represented special embodiments still by the applications in whose connection it is shown below, but on the contrary, the average person skilled in the art by the following Examples of a variety of other applications and Embodiments of the invention characterized in the claims disclosed.

Ways of Carrying Out the Invention

A first preferred embodiment of the invention is shown in FIG. 1. The Hollow cast turbine blade is operated by a hot gas flow 8 flows around, the heat input via the hot gas side 11 in the material the scoop caused in it. In today's gas turbines, this exceeds Hot gas temperature at a given mechanical Material temperature considerably. Therefore, the function such a turbine blade only by sufficient cooling be guaranteed. Because of this, the scoop of yours Cold gas side 12 ago cooled by the coolant 9. Can inside the bucket Different internals are available, such as baffle cooling plates or webs to guide the coolant on the cold gas side.

Regarding the nomenclature, it should be noted that in the present description and the claims for the sake of simplicity to the terms "Cold gas side" and "Hot gas side" is used. However, it must be be understood that this is in fact not a limitation, and Explicitly does not rule out cases in which the component surfaces do not gaseous media are flooded. It's more about simple, to use concise and familiar terms from which he understands that a surface is in contact with a first medium, one second surface is in contact with another medium, which media are at different temperatures, and the expert immediately draws the conclusion where the relatively warmer or colder Medium is located. Nor does the term "hot gas flow" a flow of a non-gaseous medium of high temperature explicitly out. Furthermore, the person skilled in the art takes the context without further the meaning of the relative terms "hot" and "cold".

Rows of blow-out openings 21 are on the surface of the blade lines running substantially normal to the direction of flow of the hot gas to recognize. Coolant that flows through these openings takes on the one hand heat from the material; on the other hand, the cooler goes down Blow-out flow with appropriate arrangement and design of the Blow-out openings 21 as an insulating layer on the hot gas side 11 of the Blade, and partially isolates it from the hot gas flow 8.

Shape and size of the blow-out openings 21, as well as their distance from each other, are not essential to the invention, and the chosen representation should never be understood in a restrictive sense.

The top view of the blade shown in FIG. 2 shows one particularly well Material accumulation 141 in the area of the rear edge 14, and the Interior 121 which narrows sharply near the rear edges Material accumulation is very likely to overheat. On the one hand is the shovel very thin in this area. The surface on the hot gas side 11 is in Trailing edge area much larger than the surface on the cold gas side 12. In addition, such accumulation of material is potentially developing large local temperature differences extremely strong Thermal stress cracks at risk. Because of the special geometric Boundary conditions in the rear edge area must literally remove the heat from the Material accumulation can be transported out. On the one hand, a row of blow-out openings 22 along the rear edge through this flowing coolant 7 takes heat from the Material accumulation 141 and transports it to the outside. So seen, the blow-out openings 22 are heat sinks. Not too much for the temperature differences along the rear edge to allow it to grow and to avoid local overheating A certain maximum distance between the heat sinks exceed. As a rule of thumb for a design criterion, it is stated that the Distance between two blow-out openings 22 eight hydraulic diameters a blow-out opening should not exceed. This initially results in a large number of blow-out openings and thus in a large one Blow-out mass flow at the trailing edge of the blade.

To avoid this, according to the invention between two Blow-out openings 22 at least on the rear edge - in this first Exact example - a pin 23 made of a material with a high Thermal conductivity - this should be at least three times as high as that Thermal conductivity of the blade material - in the material accumulation 141 introduced, which serves as an additional heat sink. Preferably everyone sticks out Thermally conductive pin two to twenty pin diameter in the blade interior and has the best possible contact with the blade material. The latter can be achieved by using the pins when casting the bucket be poured. They must have a certain length in the Bucket material can be embedded, but without penetrating it, because they otherwise a harmful thermal bridge between the hot gas side 11 and the cold gas side 12 of the blade. It will turn out to be cheap prove if the pins are embedded at a depth in the blade material, which corresponds to between 30% and 80% of the total material thickness, whereby the cheapest measure in individual cases through a numerical simulation of the Heat flows will have to be determined.

In the sense of a favorable temperature distribution, the pins are arranged that their longitudinal axes are more or less parallel to the exhaust openings run. Furthermore, it is advantageous if a along the trailing edge of the blade Number of heat conducting pins and blow-out openings approximately in one flight are arranged. This proves to be particularly advantageous with regard to to ensure a good flow of coolant around the pins, which is a necessary condition for the function of the heat conducting pins as heat sinks represents.

Here it is actually the case that the cooling air flow 9 on the cold gas side of the 12 bucket walls builds boundary layers, and that the boundary layers that be built on opposite walls, in the narrow channel in the Converge trailing edge area, and the coolant flow 9 from displacing this area of the blade interior 121. The Displacement is intensified by the pins. At a The arrangement as proposed by DE 194 54 115 is for this reason convective heat transfer between the thermal pins and the coolant rather low, which makes the heat-conducting pins function as heat sinks in the Perform the rear edge of the bucket less than optimally.

In the configuration proposed here, the trailing edge blow-out openings induce 22 forced convection in the narrow cooling gap, and the heat-conducting pins are arranged by the Blow-out streams 7 flow around and cooled. The close one shows up here Interdependence of the rear edge blow-out and the heat conducting pins.

FIG. 3 shows a further preferred embodiment Two blow-out openings arranged two heat-conducting pins. This will the coolant consumption compared to the geometry shown in Figure 1 reduced again. In Figure 3 flow control devices 25 are also in Blade interior introduced that the blow-out air flow 7 on the Guide thermal pins. Such measures can of course also be used for one Figure 1 corresponding configuration may be useful. The pipe of the coolant to the rear edge can also by appropriate turbulators in the main cooling duct respectively.

Regardless of the specific configuration chosen during execution The invention is advantageous to ensure that the distance between two Heat sinks should not be larger than eight hydraulic diameters a rear edge blow-out opening. In this context, the preferred cross-sectional area of the pins called between one and ten Cross-sectional areas of a blow-out opening.

The shape of the heat conducting pins can be varied within wide limits. So is for example, a round cross-section is not mandatory. Is appropriate however, in all circumstances, it extends along a longitudinal axis to be chosen significantly larger than the extension in the other directions. The Shape of the thermal pins is primarily due to the manufacturing method be determined, and a cylindrical pin is cut off by a Wire particularly easy to obtain. However, through the targeted Design, for example, of the part of the protruding into the coolant The flow around the pin as well as the heat exchange surface to be changed. Two examples of possible geometries are in Figures 4 and 5 shown. The design shown in Figure 4 holds the conical shape Flow cross-section between the pin 23 and the cooling side Component walls 12 largely constant. Consoles 231 enlarge the Heat exchange surface between the base material 141 and the Thermal pin 23, and improve the fixation of the pin in the base material. The corrugated design from FIG. 5 also increases the Heat exchange surface, both on the material and coolant side.

LIST OF REFERENCE NUMBERS

7

Ausblaseströmung

8th

Hot gas flow

9

Coolant flow

11

Hot-gas side

12

Cold-gas side

14

trailing edge

21

exhaust openings

22

exhaust openings

23

conducting pin

25

flow guide

121

Blade inner space

141

Bute base material

Claims (10)

Coolable turbine blade (1) with a blade rear edge 14, consisting of a base material, the turbine blade in operation on a hot gas side (11) with a first flowing medium (8) and on a cold gas side (12) in contact with a second flowing medium (9) the temperature of the first medium being higher than that of the second medium such that the turbomachine blade is heated by the first medium and cooled by the second medium, and wherein the base material of the turbomachine blade includes a plurality of pins (23) which Pins protrude from the cold gas side (12) into the flow of the second medium, and which pins consist of a material whose thermal conductivity is greater than that of the base material used to manufacture the turbomachine blade, such that the pins operate as heat sinks in the base material act, and wherein a plurality of blow-out openings are arranged (22), which establish a fluid connection between the second medium and the first medium, characterized in that the pins (23) and the openings (22) are arranged along the course of the rear edge. Coolable turbomachine blade according to claim 1, characterized in that at least one pin is arranged between two openings (22). Coolable turbomachine blade according to claim 2, characterized in that pins (23) and openings (22) are arranged alternately. Coolable turbomachine blade according to one of the preceding claims, characterized in that the pins consist of a material whose thermal conductivity is at least three times the thermal conductivity of the base material. Coolable turbomachine blade according to one of the preceding claims, characterized in that the distance between two heat sinks (22, 23) is less than eight times the hydraulic diameter of a blow-out opening (22). Coolable turbomachine blade according to one of the preceding claims, characterized in that openings (22) and pins (23) have approximately identical distances from one another. Coolable turbomachine blade according to one of the preceding claims, characterized in that the pins protrude between 30% and 80% of a local material thickness, measured in the longitudinal direction of the pins, into the base material of the component. Coolable turbomachine blade according to one of the preceding claims, characterized in that the pins protrude at least twice as far into the second medium as corresponds to the dimension which results from the root of the cross-sectional area of the pin at the point of penetration with the cold gas side. Coolable turbomachine blade according to one of the preceding claims, characterized in that means (25) are arranged on the cold gas side, which guides the medium (7) which flows through the blow-out openings (22) via the pins (23). Coolable turbomachine blade according to one of the preceding claims, characterized in that the pins are cast in the component.

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