EP1223308B1 - Turbomachine component - Google Patents

Description

Technical application

The present invention relates to a component of a turbomachine, in particular a turbine blade, which has a cooling channel through which a cooling medium with at least one deflection formed by the wall of the cooling channel, through which the flow of the cooling medium is deflected from a first channel section into a downstream second channel section , Wherein in the region of the deflection at least one flow guide is arranged in the cooling channel, by which the cooling channel is divided in the deflection in an inner and an outer flow channel.

In the field of turbomachines, in particular gas turbines, increasingly higher turbine inlet temperatures are sought and realized to increase the power. The higher temperatures are achieved on the one hand by advances in materials technology towards higher allowable material temperatures and on the other hand by improved cooling of the components which are exposed to high temperatures. Especially in the field of gas turbines, there is a need to further improve cooling for new generations of gas turbine blades.

One known cooling method for gas turbine blade cooling is internal convective cooling. In this cooling technique, cooling air is introduced through the rotor shaft into the blade root and from there into guided inside the airfoil cooling ducts, in which it receives the heat of the turbine blade. The heated cooling air is finally blown out through suitably arranged holes and slots in the turbine blade.

An exemplary profile of the cooling air ducts in a gas turbine blade (according to Thalin et al., 1982: NASA CR 1656087) is shown in FIG. The cooling air enters the turbine blade via the blade root 1, is guided via a cooling channel 2 to the rear side of the blade and finally blown out via corresponding opening slots 3. In the example shown in FIG. 1, a separate cooling channel 2a is additionally provided, via which a part of the cooling air is guided to the front and tip of the blade in order to exit there via corresponding openings 4. The flow profile of the cooling air within the airfoil is indicated by the arrows.

In a typical course of the cooling air channel 180 ° deflections 5 in the vicinity of the blade tip or the blade root are required, which connect the different sections of the cooling air channel 2 together. In the area of these deflections 5, however, complicated flow patterns develop with dead water areas, which lead to large pressure losses over the length of the cooling air channel 2 and thus require an increased pumping power for the transport of the cooling air. Furthermore arise in these areas Areas of low heat transfer to the turbine blade, which lead to local temperature peaks on the outer skin of the turbine blade.

FIG. 2 schematically shows a section of a cooling air channel 2 with a deflection 5, in which the recirculation areas, i. the areas which generate the high pressure loss are indicated by the reference numeral 6. The flow path of the cooling medium is again shown by the arrows. In addition to the pressure loss, the recirculation areas are only slightly flowed through, so here there are areas of low heat transfer.

State of the art

In the hitherto known technical developments, it has been possible in part to reduce the pressure loss over the length of the cooling channel by means of a suitable arrangement of flow-conducting elements, as can be seen, for example, in FIG.

An arrangement is known from US Pat. No. 5,073,086, in which a flow-guiding element is arranged in the cooling channel in the region of the deflection, by which the cooling channel in the deflection is completely divided into an inner and an outer flow channel. Although the pressure loss caused by the deflection can be reduced by this complete division of the flow, a much more homogeneous dissipation of the heat from the region of the deflection is not achieved. Rather, new areas of low heat transfer in the Area of the formed as Umlenkleitblech flow guide.

Arrangements are also known from US Pat. No. 4,775,296 and US Pat. No. 4,604,031, in which flow guide elements are arranged in the deflection region of a cooling channel of a turbine blade. In US 4,775,296 an arrangement of a plurality in the flow direction successively arranged flow guide can be seen, which narrow the inner flow channel visibly. No. 4,604,031 discloses an arrangement in which the radially inner flow channel of the deflection region separated from the flow guide element tapers in the flow direction.

The object of the present invention is to specify a component of a turbomachine with improved cooling, in which the pressure loss is reduced in the region of the deflections of the cooling channel and a homogeneous heat transfer is achieved.

Presentation of the invention

The object is achieved with the component according to claim 1. Advantageous embodiments of the component are the subject of the dependent claims.

The proposed component of the turbomachine, usually a turbine blade, has, in a known manner, a cooling channel, through which a cooling medium can flow, with at least one deflection formed by the wall of the cooling channel, through which the Flow of the cooling medium is deflected from a first channel portion in a downstream second channel section. In the region of this deflection, a flow-guiding element, for example in the form of a deflection guide plate, is also arranged in the cooling channel in the present component, by which the cooling channel in the deflection is completely divided into an inner and an outer flow channel. The present component is characterized in that the inner flow channel has a constriction in the flow cross-section. By this constriction, ie a constriction and subsequent re-expansion of the flow cross-section occurs a nozzle effect in the inner flow channel, which increases the heat transfer by the acceleration of the flow in an advantageous manner and simultaneously homogenized. The constriction is preferably formed by a suitable shaping or contouring of the flow-guiding element and / or the wall of the cooling channel in the region of the deflection. In the outer flow channel of the diversion, one or more outlet bores for the cooling medium are additionally formed in the wall of the cooling channel, via which a small part of the cooling medium can escape from the cooling channel into the external flow outside the component. This so-called Kühlluftausblasung - in the case of air as a cooling medium - contributes in conjunction with the features already explained again to a significant improvement in heat transfer, so that a component is obtained in which on the one hand no local temperature peaks in the area of the deflection occur more and on the other hand high average values of the heat transfer to the cooling medium can be achieved. Due to the arrangement of these outlet holes in corner regions of the deflection, in which otherwise dead water areas occur, a significantly improved heat transfer is achieved there. The holes lead to the dissolution of the dead water areas and thus contribute to a homogenization of the heat transfer. Furthermore, these holes can bring about the desired side effect that dust particles in the cooling medium are blown through the holes. To enhance this side effect, the longitudinal axes of the bores are aligned approximately in the direction of the local streamlines of the flow of the cooling medium in the cooling channel.

The proposed solution thus achieves a reduction in the pressure losses in the deflection while simultaneously homogenizing the heat transfer between the cooling medium and the wall material of the component. The present embodiment is independent of the further configuration of the component, in particular independent of the rib configuration in the first and second channel section, hereinafter also referred to as inlet and outlet channel, as well as possible curves at the outer edge regions of the deflection. Such details that occur in a variety of gas turbine blades do not affect the beneficial effect of the present invention.

The required for the best possible function of the present invention constriction of the flow cross-section in the inner flow channel of the deflection, ie in the flow channel having the shorter flow path in the deflection, on the one hand by appropriate design of the flow, for example, by a thickening, and on the other hand by a corresponding Forming of the flow guide in the inner flow channel opposite channel wall can be achieved. Of course the constriction can also be achieved by a corresponding shaping of both elements or the further wall regions surrounding the inner flow channel.

In an advantageous embodiment, in which the first and second channel section extend approximately parallel on both sides of a partition which forms one side of the wall of the cooling channel, the thickness of the partition increases in the region of the deflection in order to achieve the corresponding constriction within the region due to this increase in thickness to cause internal flow channel. The shape of the contour of this partition, which separates the outlet channel from the inlet channel, may be different in order to produce the said effect.

The flow guide, which divides the cooling channel in the deflection in an inner and an outer flow channel is formed as a rule Strömungsleitblech. This flow-guiding element preferably extends over a certain distance into the second channel section or outlet channel. The distance by which the flow-guiding element extends into the second channel section preferably corresponds approximately to the distance between the flow-guiding element and the wall of the cooling channel opposite the inner flow channel at the inlet or outlet of the deflection. By extending the flow guide an extension of the distribution of the cooling channel is achieved in an inner and an outer flow channel. At the outlet of the inner flow channel a slight constriction or widening of the channel cross-section may be provided, so that the wall of the flow-guiding element does not necessarily have to run parallel to the channel wall of the second channel section or outlet channel in this area.

The flow guiding element is preferably designed and arranged within the deflection such that approximately 25 to 45% of the mass flow of the flow entering the deflection from the inlet channel into the region within the flow guiding element, i. enters the inner flow channel, and the remainder outside the baffle, i. in the outer flow channel, flows. The mass flow ratio corresponds to the inlet cross-sectional area ratio of the outer and inner flow channels. The area ratio on the outlet channel should be approximately equal to that of the inlet channel, i. it should not deviate from this ratio by more than 20%. Of course, the deflecting guide plate, which is generally round in shape, may vary in thickness, or may itself be provided with guide devices.

In a further preferred variant of the invention, the flow guide on means which prevent accumulation of dust or dirt in one of the flow channels. This can be achieved, for example, by providing the flow-guiding element with passage openings or otherwise configuring it in a suitable manner.

By the sum of the measures or features cited in the developments, ie by the optimization of the geometry and by the Kühlluftausblasung At critical points, optimized cooling in the area of the deflection element is achieved with minimized pressure loss. The individual measures are independent of the specific geometry of the component and the cooling channel and can be used for example in Kühlkanalumlenkungen whose deflection is not equal to 180 °. Furthermore, the present invention is not limited to turbine blades or gas-cooled components, but can also be used in particular with components with other flowing cooling media.

Brief description of the drawings

Fig. 1

einen Schnitt durch eine Turbinenschaufel mit Kühlkanalumlenkungen gemäß dem Stand der Technik;

Fig. 2

eine schematische Darstellung der Ablösegebiete innerhalb einer Kühlkanalumlenkung;

Fig. 3

schematisch ein Ausführungsbeispiel für die erfindungsgemäße Ausgestaltung einer Kühlkanalumlenkung;

Fig. 4

ein Beispiel für eine Anordnung zusätzlicher Auslassbohrungen in der Kühlkanalumlenkung;

Fig. 5

die in Figur 3 dargestellte Konfiguration, mit Massnahmen zur Vermeidung einseitigen von Staub- und Schmutzansammlungen;

Fig. 6

Eine Ausgestaltung des Strömungsleitelementes zur Vermeidung von einseitigen Staub- und Schmutzansammlungen.

The present invention will be briefly explained again below without limiting the general inventive idea using an exemplary embodiment in conjunction with the drawings. Show here

Fig. 1

a section through a turbine blade with Kühlkanalverlenkungen according to the prior art;

Fig. 2

a schematic representation of the detachment areas within a cooling duct deflection;

Fig. 3

schematically an embodiment of the inventive design of a cooling duct deflection;

Fig. 4

an example of an arrangement of additional Outlet holes in the cooling duct deflection;

Fig. 5

the configuration shown in Figure 3, with measures to prevent one-sided dust and dirt accumulation;

Fig. 6

An embodiment of the flow guide to avoid unilateral dust and dirt accumulation.

Ways to carry out the invention

Figures 1 and 2 have already been explained in connection with the description of the prior art in order to show the problems occurring there of the pressure loss and the areas of low heat transfer within the deflection of a cooling channel.

Figure 3 shows a schematic representation of an embodiment of the embodiment of the cooling duct deflection 5 of the component of a turbomachine according to the present invention. The flow direction of the cooling medium is again indicated in this figure by thick arrows. The cooling medium flows via a first channel section 9 into the deflection 5 and from there into a second channel section 10. The two channel sections 9 and 10 are separated from one another in this example by a partition wall 11, which is part of the cooling channel wall 12. Such a cooling channel may be in a conventional gas turbine blade, as shown for example in FIG. 1, be arranged.

Within the deflection 5, a shaped flow or Umlenkleitblech 8 is formed, which divides the cooling channel within the deflection 5 in a radially inner flow channel 13 and a radially outer flow channel 14. Both flow channels are completely separated by the Umlenkleitblech 8. In the present example, the deflecting baffle 8 also extends into the second channel section 10. The distance by which the Umlenkleitblech 8 protrudes into the second channel section 10, approximately corresponds to the width B 'and B "of the distance between the partition wall 11 and the inlet and outlet channel and the baffle. 8

The deflection baffle is designed in this example so that approximately 25 to 45% of the mass flow of the flow entering from the inlet channel 9 into the deflection 5 flows into the region of the inner flow channel 13 and the remainder flows into the region of the outer flow channel 14. The mass flow ratio corresponds to the inlet area ratio A '/ B'. The area ratio at the exhaust duct A "/ B" in this example corresponds to the area ratio at the intake port and should not deviate more than ± 20% from A '/ B'.

In the present example, the partition wall 11 in the region of the deflection 5, that is contoured at its deflection-side end such that it leads to a constriction of the flow cross section in the inner flow channel 13. The contouring is in this example by a thicker thickness of the partition 11 reached. The linear increase in the thickness of the dividing wall 11 shown in FIG. 4 and the deflecting end or edge adapted to the rounded profile of the flow deflector 8 form a nozzle-like constriction at the inlet to the inner flow passage 13 and a correspondingly shaped widening at the outlet into the second passage section 10 reached. By this configuration, a nozzle effect occurs, which increases the heat transfer between the cooling medium and the component in this area by the acceleration of the flow and thus simultaneously homogenized. Without such a constriction areas of low heat transfer within the baffle 8, ie in the inner flow channel 13 would occur. The constriction of the cross-sectional area of the inner flow channel 13 should be about 5 to 20%.

In addition to the flow guide plate 8 and the constriction caused by the partition 11 of the inner flow channel 13, two bores 15 in the corner regions of the deflection 5 can be seen in the present FIG. Through these additional holes 15, a small portion of the cooling air is blown into the external flow outside the component. This advantageously leads to an acceleration of the flow in the region of the detachment or dead water areas at the outer corners, and forces a convective flow through the dead water areas 6 with coolant, so that the dead water areas fill, which contributes to a further homogenization of the heat transfer ,

Preferably, the holes 15 are aligned depending on the location with their bore axes approximately in the direction of the flow lines of the flow of the cooling medium, so that - as an additional side effect - the discharge of small particles or dust in the cooling air through the holes 15 can take place.

FIG. 4 shows a possible arrangement of the holes 15 as well as a favorable orientation of the associated bore axes (indicated by the dot-dashed lines). The illustration corresponds to a section through a gas turbine blade tip perpendicular to the viewing plane of FIG. 3.

FIG. 5 shows a further preferred embodiment of the invention shown in FIG. The flow guide 8 has a number of holes 16, which help to avoid dust and dirt accumulation in the outer 14 or inner 13 flow channel. Figure 6 shows another way to achieve this effect. The flow guide is divided into a plurality of sub-elements, 8a and 8b, between which a gap is formed, which has the same effect as the holes 16 in Figure 5.

LIST OF REFERENCE NUMBERS

1

blade

2,2a

cooling channel

3

Outlet slits, trailing edge blowing

4

outlet openings

5

redirection

6

Dead water or recirculation area, area with high pressure loss

8th

Flow-conducting element, flow or deflection guide plate

8a, 8b

partial elements

9

First, upstream, channel section

10

Second, downstream, channel section

11

partition wall

12

Kühlkanalwandung

13

Inner flow channel

14

Outer flow channel

15

outlet bores

16

Bore, opening:

Claims (11)

1. Component of a turbomachine, in particular a turbine blade, which has a cooling duct (2) through which a cooling medium is capable of flowing, with at least one deflection (5) which is formed by the wall (11, 12) of the cooling duct (2) and by which the flow of the cooling medium is deflected from the first duct portion (9)into a downstream second duct portion (10), at least one flow guide element (8) being arranged in the cooling duct (2) in the region of the deflection (5), the cooling duct (2) being divided in the deflection (5) into an inner (13) and an outer (14) flow duct by means of the said flow guide element, the inner flow duct (13) having a contraction in the flow cross section and at least one outlet bore (15) being formed in the wall (12) of the cooling duct (2) in corner regions of the deflection in the outer flow duct (14), characterized in that the at least one outlet bore (15) is arranged such that, via the latter, a small part of the cooling medium can emerge from the cooling duct (2) into an external flow outside the component.
2. Component according to Claim 1, characterized in that the contraction is brought about the shaping of or contouring of the flow guide element (8) and/or of the wall (11, 12) of the cooling duct (2).
3. Component according to Claim 2, characterized in that the first (9) and the second (10) duct portion run on both sides of a partition (11) as part of the wall (11, 12) of the cooling duct, the thickness of the partition (11) increasing in the region of the deflection (5), in order to bring about the contraction of the flow cross section in the inner flow duct (13).
4. Component according to one of Claims 1 to 3, characterized in that the flow guide element (8) extends into the second duct portion (10).
5. Component according to Claim 4, characterized in that the flow guide element (8) extends into the second duct portion (10) over a distance which corresponds approximately to the distance between the flow guide element (8) and that wall (11) of the cooling duct (2) which lies opposite in the inner flow duct (13) at the transition of the first (9) or second (10) duct portion to the deflection (5).
6. Component according to one of Claims 1 to 5, characterized in that the flow guide element (8) is arranged in the cooling duct (2) in such a way that 25 to 45% of the mass flow of cooling medium entering via the first duct portion (9) flows through the inner flow duct (13).
7. Component according to one of Claims 1 to 6, characterized in that the flow guide element (8) and/or the wall (11, 12) of the cooling duct (2) are/is designed in such a way that they bring about a contraction of the flow cross section in the inner flow duct (13) of 5 - 20%.
8. Component according to one of the preceding claims, characterized in that the outlet bores (15) extend at least approximately in the direction of local flow lines of the flow of the cooling medium.
9. Component according to one of the preceding claims, characterized in that the outlet bores (15) are dimensioned in such a way that they allow a discharge of dust from the cooling medium.
10. Component according to one of the preceding claims, characterized in that the outlet bores (15) are arranged in dead-water zones (6) of the cooling duct which have a low throughflow, and there ensure that a convective cooling-medium throughflow is maintained.
11. Component according to one of the preceding claims, characterized in that the flow guide element (8) has suitable means (16) and/or a suitable configuration for avoiding dust accumulation on one side.

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