EP1046784A1 - Cooled structure - Google Patents

Abstract

For the cooling of a gas turbine component, subject to high temps., the material of the component (141) has an alternating a of blower openings (22) for a coolant (9) and pins (23) with a high thermal conductivity, of metal or diamond, extending out of component on the cooling side (12). The projecting pins are cooled while heat is applied to the zones where the pins are embedde Through the alternating layout with the blower openings, the air flow (7) is ensured around the pins

Description

Technical field

The present invention relates to a coolable component 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 the entire 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. In addition 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 where 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. Here 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 from direct contact with the hot medium. You misplace yourself with modern gas turbines completely on film cooling, the Coolant consumption, however, by mass.

The development has therefore increasingly moved 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. Problems 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 of 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 trailing edge blowing, 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 do without 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.

Presentation of the invention

This is where the invention comes into play. For a coolable component consisting of a Base material, which component is in operation on a hot gas side with a first flowing medium and on a cold gas side with a second flowing medium is in contact, the temperature of the first medium is higher than that of the second medium, such that the component of the the first medium is heated and cooled by the second medium, and wherein the base material of the component encloses pins, which pins from the Cold gas side protrude into the flow of the second medium, and which pins are made of a material whose thermal conductivity is greater is that of the base material used to manufacture the component, such that the pins operate as heat sinks in the base material heat transfer should improve from the pins to the cooling medium become.

According to the invention, this is achieved in that the component Has blow-out openings, through which at least part during operation said second medium flows from the cold gas side to the hot gas side, in such a way that the blow-out openings also act as heat sinks, and that along at least one line on the cold gas side each at least one pin and at least one opening are arranged. At a corresponding pressure drop between the two flow media results from the additional introduction of blow-out openings even in a narrow Split a forced convection flow, the coolant around the pins leads around.

The essence of the invention is, on the one hand, the heat instead of through the Coolant flowing through blow-out openings through thermal to lead highly conductive pins out of the material, so that the Limit coolant consumption. The limitation of Coolant consumption has a very positive effect on the Efficiency when compressor air is used for cooling purposes. The pins are expediently running along the cold gas side Alignments arranged, analogous to the arrangement of the blow-out openings in the Film cooling. On the other hand, the fluid mechanical constraints prevent in a closed cooling system within a component a good one, for example, when cooling a trailing edge of a blade convective heat transfer from the pins to the coolant, but what a The condition for the function of the cooling device is. Therefore, between Blow-out openings are introduced into the heat conducting pins, which in turn are part the cooling, but on the other hand for a good flow around the Pins and ensure that the convectively heated coolant is removed. Here the cooling effect is even beyond the measure of each individual considered cooling method increased because the pins are in their longitudinal direction as well as radially intensive flow. The effect can be improved become, if arranged on the cold gas side control devices to the Discharge the coolant flowing through the 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 blowing, which means 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 more uneven.

The arrangement of blow-out openings and heat conducting pins can be according to different criteria, and in individual cases will of course be one detailed calculation of the temperature distributions in the Require machine component. For the geometric arrangement of the pens and openings relative to each other, it will prove appropriate to use one Number of alternately arranged pins and openings in one flight to be arranged, analogous to the arrangement of the blow-out openings in rows. For a minimized coolant consumption will probably be the alternating one Arrangement of two pins and one blow-out opening prove suitable, the opening is expediently arranged centrally between two pins. In order to achieve the most homogeneous possible temperature distribution, on the other hand, the alternating arrangement of one pin and one opening each prefer to be. An equidistant arrangement of pins and openings will in most cases also contribute to the Temperature differences within the component at a given To minimize the overall blow-out cross-section. It becomes in the sense of a even temperature distribution in the one to be cooled as described Section of the component be when the distance between two heat sinks is not more than eight hydraulic diameters of a blow-out opening. In the same context, the pins with their longitudinal axes should more or be arranged less 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, as high as possible, and at least have three times the value of the base material. The melting point too the material must of course be sufficiently high. Materials that are suitable for the production of the thermal pins, for example Tungsten, silver, or especially diamond. The pens have to be one have the best possible heat transfer to the base material, which is what realizes that they are cast in the components. Here However, should you under no circumstances remove the complete material thickness of the component from the Penetrate the cold gas side to the hot gas side to avoid any disadvantage To create thermal bridges. Advantageously, the pens are so deep in that Base material introduced, as it corresponds to 30% to 80% of the material thickness. On the one hand, this ensures a large heat exchange surface, on the other hand the formation of thermal bridges is avoided. Furthermore, the Thermal pins of course by a certain axial dimension in the Protect the coolant.

As shown in the introduction, the invention unfolds Cooling configuration their specific advantages, especially when used in hollow components, inside of which the flow of a cooling medium is provided, in particular where component walls are pointed Collide angles. This configuration can be found in particular the trailing edges of gas turbine blades.

The cooling configuration according to the invention is also used for the cooling of Advantageously to use blade platforms. On the one hand, the pens help Dissipate heat from the very solidly built platforms without the To allow cooling air consumption to rise above the masses. Here, the Cooling configuration according to the invention advantageously also with impingement cooling be combined

Brief description of the drawing

• Fig. 1 eine erste bevorzugte Ausführungsform der Erfindung zur Kühlung der Hinterkante einer Gasturbinenschaufel
• Fig. 2 eine Draufsicht auf die in Fig. 1 dargestellte Gasturbinenschaufel
• Fig. 3 eine weitere bevorzugte Ausführungsform der Erfindung zur Kühlung der Hinterkante einer Gasturbinenschaufel
• Fig. 4 und 5 Beispiele für mögliche Varianten der Gestaltung der Wärmeleitstifte
• Fig. 6 ein weiteres Beispiel für die Anwendung der Erfindung bei der Kühlung einer Plattformkante, und Fig. 7 einen Schnitt entlang der in Fig. 6 eingezeichneten Linie VII - VII.

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

• Fig. 1 shows a first preferred embodiment of the invention for cooling the rear edge of a gas turbine blade
• Fig. 2 is a plan 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
• 4 and 5 examples of possible variants of the design of the heat-conducting pins
• 6 shows a further example of the application of the invention for cooling a platform edge, and FIG. 7 shows a section along the line VII-VII shown in FIG. 6.

The exemplary 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 context it is shown below, delimited, 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 in two views in the Figures 1 and 2 shown. The hollow cast turbine blade is in the Operation flows around from a hot gas flow 8, which has a heat input causes the hot gas side 11 into the material of the blade. At today's gas turbines, the temperature of the hot gas exceeds that of a material temperature allowed given the mechanical load considerably. The function of such a turbine blade can therefore only be achieved by one sufficient cooling can be guaranteed. For this reason, the Blade cooled from its cold gas side 12 by the coolant 9. in the Different internals can be present, such as Baffle cooling plates, or webs for guiding 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 of 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 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 not 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 material accumulation 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 trailing 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 should not exceed a blow-out opening. 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 in. They must have a certain length in the Bucket material can be embedded without penetrating it, however, since it 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 so that their longitudinal axes are more or less parallel to the exhaust openings run. Furthermore, it is favorable 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.

It is actually the case here that the cooling air flow 9 on the cold gas side 12 of the 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 further enhanced by the pins. At a For this reason, the arrangement as proposed by DE 194 54 115 is convective heat transfer between the thermal pins and the coolant rather low, which makes the thermal 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. It shows the close Interdependence of the rear edge blow-out and the heat conducting pins.

A further preferred embodiment is shown in FIG. 3 two blow-out openings, two heat conducting pins. This will the coolant consumption compared to the geometry shown in FIG. 1 reduced again. In Fig. 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 Fig. 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 at least when used on trailing blade edges make sure that the distance between two heat sinks is not greater is selected as eight hydraulic diameters of a rear edge blow-out opening. In this context, the preferred one 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 choose significantly larger than the extension in the other directions. The 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 FIGS. 4 and 5 shown. The design shown in Fig. 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 Thermally conductive 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.

In a further preferred embodiment, FIG. 6, carries a Blade platform 3 a blade 1. The entire configuration is from a hot gas flow 8 flows against. The airfoil is on itself known cooled any way, cooling and coolant supply of the Airfoil are not considered in the figure. In the hollow Blade platform flows in coolant 9, and strikes an impact cooling insert 31. The coolant flows through openings in the impact cooling insert 32. Coolant jets 91 hit the cold gas side 12 of the at high speed Platform where an intensive convection heat exchange takes place. The coolant is subsequently discharged through blowout openings 22. Again, as in the section shown in FIG. 7 along the line VII - VII well recognizable, essentially in an escape along the Platform leading edge heat-conducting pins 23 and blow-out openings 22 arranged alternately so that the blow-out stream 7 is only the Thermal conductors around and finally flows through the blow-out openings. In this top view is for the sake of clarity part of the Openings of the impact cooling insert are not shown.

Of course, the cooling of the invention Platform edge with the features specified above, such as the shape of the Thermal pins or the flow control devices can be combined. It should also be mentioned that in the exemplary embodiment in FIGS. 6 and 7 Impact cooling shown is optional, if it is also appropriate helps to use the coolant particularly efficiently.

In a similar manner, a multitude of Possible applications and special configurations of the Claims characterized invention, not by the Embodiments is limited.

Reference list

1

Airfoil

3rd

Bucket platform

7

Blow-out flow

8th

Hot gas flow

9

Coolant flow

11

Hot gas side

12th

Cold gas side

14

Trailing edge

21

Blow out openings

22

Blow out openings

23

Thermal pin

25th

Flow control device

31

Baffle plate

32

Baffle cooling opening

91

jet

121

Bucket interior

141

Trailing edge base material

231

console

Claims (13)

Coolable component, consisting of a base material, which component in the Operation on a hot gas side (11) with a first flowing medium (8) and on a cold gas side (12) with a second flowing medium (9) is in contact, the temperature of the first medium being higher than that of the second medium, such that the component from the first Medium is heated and cooled by the second medium, and wherein the Base material of the component pins (23) encloses which pins from the Cold gas side (12) out into the flow of the second medium protrude, and which pins are made of a material whose Thermal conductivity is greater than that for manufacturing the component used base material, such that the pins in operation as Heat sinks act in the base material, characterized in that the component has blow-out openings (22) through which in operation at least a part (7) of said second medium from the cold gas side to Hot gas side flows in such a way that the blow-out openings also as Heat sinks act, and that along at least one line on the Cold gas side at least one pin and at least one opening are arranged alternately. Coolable component according to claim 1, characterized in that at least a number of alternately arranged pins and Openings are arranged in alignment. Coolable component according to claim 1, characterized in that the Pins consist of a material whose thermal conductivity is at least has three times the thermal conductivity of the base material. Coolable component according to claim 1, characterized in that the Distance between two heat sinks (22, 23) less than eight times of the hydraulic diameter of a blow-out opening (22). Coolable component according to claim 1, characterized in that Openings (22) and pins (23) are approximately identical distances apart to have. Coolable component according to claim 1, characterized in that the Pins between 30% and 80% of a local material thickness in which Longitudinal direction of the pins measured in the base material of the component protrude into it. Coolable component according to claim 1, characterized in that the The pins protrude at least twice as far into the second medium as it does corresponds to the measure resulting from the root of the cross sectional area of the Pin on the penetration with the cold gas side results. Coolable component according to claim 1, characterized in that on the Cold gas side means (25) are arranged, the medium (7) through the Blow-out openings (22) flows through which pins (23) conduct. Coolable component according to claim 1, characterized in that the Pins run parallel to the blow-out openings. Coolable component according to claim 1, characterized in that the Pins are cast in the component. Coolable component according to claim 1, characterized in that the Component is a hollow body, the hot gas side outside and the Cold gas side is inside. Coolable component according to claim 11, characterized in that the Component is a gas turbine blade, and the pins (23) and Blow-out openings (22) along at least one line on the cold gas side (12) a blade platform (3) belonging to the gas turbine blade are arranged. Coolable component according to claim 11, characterized in that the The component of a gas turbine blade is that the blow-out openings (22) and Pins (23) along a trailing edge (14) belonging to the blade are arranged, and that the pins inside (121) the Project the gas turbine blade.

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