EP1113145A1 - Blade for gas turbines with metering section at the trailing edge - Google Patents

Abstract

The blade (30) consists in the trailing-edge region (21) of at least two parallel walls (10, 11), forming inner cooling channels (18, 19) with ribs (16, 17, 20), and is cooled by the coolant flowing through the channels, running parallel to the walls at the trailing edge and passing out of the blade between these walls,

Description

TECHNICAL AREA

The present invention relates to the field of gas turbine engines Guide elements such as guide or turbine blades. It affects one of a hot Air flow around the guide element for a gas turbine, which at least in a rear edge area, in which the air flow breaks off from the guide element at least two substantially parallel, and with ribs together there are walls connected to form inner cooling channels, and which is cooled on the inside with cooling medium flowing through the cooling channels, the cooling medium at the rear edge substantially parallel to the walls between them emerges from the guide element.

STATE OF THE ART

A gas turbine comprises a multitude of elements, which consist of hot working air be flown to. Because the working air has a temperature that for many the materials from which such flow-around components are built, in particular leads to severe signs of wear after a long period of operation it is necessary to cool many of these components. The cooling can be used as internal cooling be designed in which the elements are designed as hollow profiles or simple be provided with internal cooling channels through which a cooling air flow is passed becomes. As an alternative or in addition, it is also possible to use what is known as film cooling to provide, in which the elements are acted upon by an outside cooling air film become.

Modern gas turbine blades usually use a combination of the above methods, i.e. an internal convective cooling system is used, which critical points also has openings for film blowing. To efficiency and to increase the performance of the gas turbine, as well as to reduce emissions reduce, the amount of cooling air used must be minimized. This means, that even for large components only a small cooling air mass flow Available. To the low cooling mass flows at the same time required to realize and control efficient internal heat transfer the flow cross-sections reduced accordingly. Throttle cross sections introduced become.

In many of the known blade designs, the throttling of the cooling mass flow takes place in the area of the cast blade trailing edge, near the Cooling air outlet takes place. In particular for manufacturing reasons, in order To avoid core breaks, the end of the ribs is the pressure and suction side Connect the wall, set back in the axial direction, i.e. the ribs end already inside the shovel and do not reach the rear edge.

Figure 1 shows a section through a guide vane according to the prior art, such as it is often used in gas turbines. It is an axial to Main axis of the turbine and cut perpendicular to the plane of the airfoil through a guide vane, as is typically immediately after the combustion chamber and in front of the first row of the gas turbine for optimal flow against the blades be used. The blade is designed as a hollow profile, which bounded on the suction side by a wall 10 and on the pressure side by a further wall 11 becomes. In the inflow area, the blade is widened, walls 10 and 11 are in a curve connected to each other, and is located between the walls 10 and 11 there is a central, radially extending insert 12 around which the cooling channel leads around. In the rear area, the guide vane 30 is only one of the two axially Direction, broken ribs interconnected walls 10 and 11 limited, cooling channels run in between. Often the central one Insert 12 completely or partially enclosed by approximately axially extending ribs. These ribs converge at the rear end of the insert (16 in Fig. 1) and from there connect the suction and pressure side bucket walls. Between The ribs form approximately axial channels in which the cooling air is guided becomes.

In the further course, the fin bank can be interrupted by one in the radial To produce plenum 18. The following ribbed bench 17 can be arranged "in line" or offset to the previous ribbed. In the area of the rear edge, the pressure and suction walls are very short ribs or so-called pin rows connected together. State of the art is well, leave these internals (ribs, pins, etc.) inside the blade ends. This avoids the need for the core required for casting production has a large jump in the cross-sectional area exactly at the rear edge. This strong discontinuity in the cross-sectional shape of the core leads to the manufacture to a high number of core breaks. However, the above procedure has the considerable Disadvantage that the outlet cross section of the cooling air and thus the cooling air mass flow can only be controlled insufficiently.

The walls also mostly have film cooling holes 13-15, through which Cooling air can flow to the outside.

• Da der Querschnitt klein ist, wirken sich selbst kleine Toleranzen bei der Herstellung (Guss) auf den Kühlluftmassendurchsatz der Schaufel aus.
• Da die Drosselstelle im Inneren des Leitelements liegt, lässt sich der wirksame Drosselquerschnitt nur schwer messen und kontrollieren.
• Da die Drosselkante im Inneren des Leitelements liegt, kann der wirksame Drosselquerschnitt nachträglich nur schwer modifiziert werden.
• Die beiden meist recht dünnen Wände sind äusserst anfällig auf Beschädigungen, welche von Fremdkörpern im Heissgas verursacht werden, und welche u.U. sogar zu einer Veränderung der Drosselquerschnitte führen können.
• Durch die stufenweise Expansion der Kühlluft (1) am Ende der Rippen und (2) an der Schaufelhinterkante lässt sich der Kühlluftmassenstrom nur schwer kontrollieren und justieren.

This design of the internal convective cooling system has a number of disadvantages:

• Since the cross-section is small, even small tolerances during manufacture (casting) affect the cooling air mass flow rate of the blade.
• Since the throttle point is inside the guide element, it is difficult to measure and check the effective throttle cross-section.
• Since the throttle edge lies inside the guide element, the effective throttle cross-section can only be modified with difficulty afterwards.
• The two walls, which are usually quite thin, are extremely susceptible to damage caused by foreign bodies in the hot gas and which may even lead to a change in the throttle cross-sections.
• The gradual expansion of the cooling air (1) at the end of the ribs and (2) at the rear edge of the blade makes it difficult to control and adjust the cooling air mass flow.

PRESENTATION OF THE INVENTION

The invention is therefore based on the object of a hot air flow flow around the guide element of a gas turbine, which at least in a rear Edge area, at which the air flow breaks off from the guide element, at least two arranged substantially parallel, and with ribs inside each other Cooling channels forming connecting walls, and which with cooling medium flowing through the cooling channels is cooled on the inside, the Coolant at the trailing edge substantially parallel to the walls between this emerges from the guide element.

This object is achieved in a guide element of the type mentioned at the outset by at least part of the ribs flush with the rear edge are arranged. The essence of the invention is therefore part of the Ribs connecting walls directly at and essentially flush with the Arrange rear edge and the ribs resp. the channels in between thus making it more accessible and the walls in the edge area better closed stabilize. In this way, the walls in the rear edge area are essential less susceptible to damage from foreign bodies carried in the working air flow. In addition, there is also the advantage that the cooling air throughput between through the ribs arranged on the rear edge through the manufacturing process and much easier for maintenance due to the good accessibility can be reworked or adjusted.

A first preferred embodiment of the invention is characterized in that that the throughput of cooling medium through the guide element essentially through the dimensioning of the between the ribs, here so-called throttle ribs Outlet openings is determined. The better one due to the arrangement Accessibility and reworkability is particularly advantageous if the Throttling of the cooling air through the throttling ribs on the rear edge is effected, and the throttling from the outside easily by drilling or the like. can be set or measured.

Another embodiment of the invention is characterized in that the Thickness of the guide element at the rear edge in the range from 0.5 to 5 mm, in particular is preferably in the range of 1.0 to 2.5 mm, and that the slot thickness of the Cooling air ducts between the walls at the outlet in the range of 0.3 to 2 mm, is in particular in the range from 0.8 to 1.5 mm. Among other things, if the guiding element is designed as a guide blade arranged in front of a turbine rotor and if air is used as the cooling medium, the ones according to the invention prove Arrangement and these dimensions as particularly advantageous.

Further embodiments of the guide element result from the dependent ones Claims.

The invention further comprises a method for producing one of one hot air flow around the guide element of a gas turbine, which at least in a rear edge area, in which the air flow breaks off from the guide element at least two substantially parallel, and with ribs together there are walls connected to form inner cooling channels, and which is cooled on the inside with cooling medium flowing through the cooling channels, the cooling medium at the rear edge substantially parallel to the Walls between them emerges from the guide element, which is characterized by that the guiding element is manufactured in a casting process that the rear edge area with the guide element or its walls in Flow direction extending supernatant is poured, and that after the Pour the supernatant so that at least part of the ribs arranged as a throttling ribs with the rear edge essentially flush are. The casting core is shaped so that the rib geometry over the rear edge of the blade is modeled in the cast core. Only after one The rib geometry is about 0.5 to 5, preferably 1 to 3 core thicknesses hidden. This method makes it easy to manufacture one according to the invention Guiding element only possible. With a normal casting process, namely the effective throttle cross-section is not simply placed directly on the trailing edge become. The sudden increase in cross-section at the outlet in the casting core leads to manufacturing to a sharp increase in core breaks. This can be done while leaving a protrusion during the casting process can be avoided.

A preferred embodiment of the method is characterized in that no ribs are arranged between the walls in the area of the overhang, and that the throughput of cooling medium through the finished guide element essentially by the dimensioning of the arranged between the throttle ribs Outlet openings is determined. If in the area of the protrusion on any ribs can be dispensed with in the casting process, in particular in the preferred Press casting processes ("investment casting") are largely avoided. It shows furthermore that especially if the length of the supernatant is in the range from 0.5 to 3 times as large, particularly preferably of the same size, as slot thickness of the cooling air duct between the walls, such core breaks can be avoided can do without excessive post-processing after manufacture would.

Further preferred embodiments of the method result from the dependent ones Claims.

BRIEF EXPLANATION OF THE FIGURES

Fig. 1

zeigt einen Querschnitt durch eine Leitschaufel mit interner Kühlung für eine Gasturbine nach dem Stand der Technik; und

Fig. 2

a) zeigt einen Querschnitt durch eine Leitschaufel mit unmittelbar an der Hinterkante der Schaufel angeordneten Drosselrippen, b) eine Detailansicht des Hinterkantenbereichs des Schnittes nach a), und c) einen Schnitt entlang der Linie X-X in Figur 2a), d.h. im wesentlichen parallel zur Ebene der Schaufel durch den internen Kühlkanal.

The invention will be explained in more detail below using exemplary embodiments in conjunction with the drawings.

Fig. 1

shows a cross section through a vane with internal cooling for a gas turbine according to the prior art; and

Fig. 2

a) shows a cross section through a guide vane with throttle ribs arranged directly on the rear edge of the blade, b) a detailed view of the rear edge region of the section according to a), and c) a section along line XX in FIG. 2a), ie essentially parallel to the plane the bucket through the internal cooling channel.

WAYS OF CARRYING OUT THE INVENTION

Figure 2 a) shows a section through a guide vane directly to the rear edge bordering ribs 24 between the walls 10 and 11. It is about a figure 2 corresponding axially to the main axis of the turbine and perpendicular to Blade plane running section through a guide blade. The shovel is again formed as a hollow profile, which is on the suction side of a wall 10, and is delimited on the pressure side by a further wall 11. In the back is the Guide vane with each other only from the two with ribs interrupted in the radial direction connected walls 10 and 11 limited, cooling channels run between them. Figure 2c) shows a section along the line X-X in Figure 2a), i.e. essentially parallel to the leaf plane. Immediately adjacent to the insert 12 first ribs 16. The between the insert 12 and the walls 10 and 11th flowing cooling air flows essentially axially in the channels 27 between the Ribs 16 in the rear area of the guide vane. Behind the first row from Ribs 16 there is a front radial plenum 18 which has a flow and pressure equalization of the cooling air in the radial direction allowed. Then one closes another row of ribs 17, which in this example alternate as continuous Ribs 17b or axially divided ribs 17a are formed. The single ones Ribs of the rows 16 and 17 advantageously have a so-called division ratio, the ratio of the radial width e normal to the plane of the sheet radial spacing f, in the range of 0.25 to 0.75.

Another radial plenum 19 follows, followed by so-called pins 20, i.e. as simple webs formed rows of ribs which are as uniform as possible Allow distribution of the cooling air flow at the rear edge 21. The division ratio (Diameter g to radial spacing h) of the pins 20 lies in the Range from 0.25 to 0.7.

• Der effektive Drosselquerschnitt kann leicht bei der Austrittskante gemessen werden.
• Es entsteht nur eine Drosselstelle genau na der Hinterkante anstatt zweier Drosselstellen am Ende der Rippen und der Hinterkante.
• Gegebenenfalls beim Gussverfahren entstandene Ungenauigkeiten der Drosselregion können leicht nachbearbeitet werden, da die Drosselstellen von aussen zugänglich sind.
• Der Drosselquerschnitt kann bei Bedarf leicht verändert werden.
• Die Anordnung der Rippen ganz am Ende der Schaufel führt zu einer erhöhten Stabilität der Abrisskante, so können Fremdkörper im Arbeitsluftstrom die Hinterkante weniger beschädigen und die Kühlung der Komponente kann durch derartige Deformationen weniger beeinträchtigt werden.

Another row of ribs 24 is now located directly at the rear edge and flush with it. The row of rear ribs is dimensioned such that the cooling air flow of the entire effective cooling channel cross section is restricted by the channels 25 between the so-called throttle ribs 24 . Because the throttling is effected at the rear edge 21 and with such a row of throttle ribs 24, there are a number of advantages:

• The effective throttle cross section can easily be measured at the trailing edge.
• There is only one throttle point exactly after the trailing edge instead of two throttling points at the end of the ribs and the trailing edge.
• Any inaccuracies in the throttle region that may arise during the casting process can easily be reworked, since the throttle points are accessible from the outside.
• The throttle cross section can be easily changed if necessary.
• The arrangement of the ribs at the very end of the blade leads to increased stability of the tear-off edge, foreign objects in the working air flow can damage the rear edge less and the cooling of the component can be less impaired by such deformations.

Such a blade is usually produced using the casting process, as a rule an investment casting process. This casting process can but when making the effective throttle cross section not just straight to the Trailing edge. The sudden cross-sectional expansion at the outlet in the cast core leads to a sharp increase in core breaks during manufacture. However, this can be avoided if a protrusion is left in the casting process become. The cooling geometry shown in the core is based on the actual one Component limit extended. Figure 2b) shows the edge area of an element extended in this way beyond the rear edge by the length b. in the In the region of the protrusion, there are advantageously no more ribs. The transition from the throttle geometry does not then coincide with the core holder, rather, it first occurs within the extended component Transition from the throttle geometry to a continuous radial channel instead, which can then be used as a core holder without the risk of core breakage can. This transition can be optimal in various ways depending on the procedure to be designed to hold the core, i.e. it is not imperative that the two Walls as shown in Figure 2b) simply extended evenly to the rear e.g. also a gradual protruding expansion or rejuvenation resp. Thickening of the walls in the area of the overhang is conceivable. The protruding geometry is after the casting to the target length of the rear edge post-processed, i.e. removed so that the throttling points coincide with the rear edge. This can e.g. together with those that are usually necessary after the fact Post-processing such as erosion and laser drilling of the film cooling holes 13-15 happen.

In the embodiment shown, the rear edge usually has a thickness d im Range from 0.5 to 5 mm, preferably in the range from 1.0 to 2.5 mm. The slit thickness c of the cooling air duct is usually in the range from 0.3 to 2.0 mm, preferably in Range from 0.8 to 1.5 mm. To effectively avoid core breaks during the casting process to be able to, the protrusion b above the rear edge 0.5 to 5 times, preferably 1 to 3 times, the length a of Throttle ribs 24 amount, it is particularly advantageous if the projection b is the same as the length a of the throttle ribs.

LIST OF DESIGNATIONS

10th

suction side wall

11

pressure side wall

12th

Use or core

13

suction-side film holes

14

Film holes on the front edge

15

pressure-side film holes

16

ribs attached to the insert

17th

Intermediate ribs

18th

anterior radial plenum

19th

posterior radial plenum

20th

Pins

21

Trailing edge of the sheet

22

Exit opening at the rear edge

23

Working air flow

24th

Throttle ribs on the rear edge

25th

Cooling air outlet openings on the rear edge

26

axial channels between ribs 17

27

axial channels between tippers 16

28

inlet-side cooling air flow

29

outlet-side cooling air flow

30th

vane

a

Throttle rib length

b

Length of the protrusion after casting

c

Slit thickness of the cooling air duct at the outlet

d

The thickness of the guide vane at the rear edge

e

Width of the choke ribs

f

Rib division of the throttle ribs

G

Pin width 20

H

Division of pins 20

Claims (11)

A hot air flow (23) has a guide element (30) around a gas turbine which, at least in a rear edge region (21), in which the air flow (23) breaks off from the guide element (30), consists of at least two substantially parallel ones and with ribs (16, 17, 20) walls (10, 11) connected to one another to form internal cooling channels (18, 19, 25, 26, 27), and which is connected to the cooling channels (18, 19, 25, 26, 27) flowing cooling medium (28, 29) is cooled on the inside, the cooling medium emerging from the guide element (30) at the rear edge (21) essentially parallel to the walls (10, 11) between them,
characterized in that
at least some of the ribs (24) are arranged so that they are flush with the rear edge (21). Guide element (30) according to claim 1, characterized in that the Throughput of cooling medium (28, 29) through the guide element (30) essentially by dimensioning the between the throttle ribs (24) arranged outlet openings (25) is determined. Guide element (30) according to claim 2, characterized in that the throttle ribs (24) parallel to the rear edge (21) have a width (e) and are spaced apart by a respective rib pitch (f)
and that the ratio of width (e) to rib pitch (f) is in the range of 0.25 to 0.75. Guide element (30) according to one of the preceding claims, characterized characterized in that the thickness (d) of the guide element (30) at the rear edge (21) in the range from 0.5 to 5 mm, particularly preferably in Range is from 1.0 to 2.5 mm, and that the slot thickness (c) of Cooling air channels (25) between the walls (10, 11) at the outlet (21) in Range from 0.3 to 2 mm, especially in the range from 0.8 to 1.5 mm is. Guide element (30) according to one of Claims 1 to 4, characterized in that that it is arranged as a guide vane in front of a turbine rotor (30) and that air is used as the cooling medium. Guide vane (30) according to claim 5, characterized in that the Guide vane is widened in its inflow area and in Inflow area the cooling air around an inner, central, radially extending Insert (12) in suction and pressure side cooling channels flows and that the cooling air between the insert (12) Ribs (16), then between intermediate ribs (17), then between Pins (20) flow between the walls (10, 11) before they through outlet openings (25) at the rear edge of the guide vane (30) emerges. Method for producing a guide element (30) of a gas turbine around which a hot air flow (23) flows and which is arranged at least in a rear edge region (21), in which the air flow (23) breaks off from the guide element (30), from at least two arranged essentially in parallel , and with ribs (16, 17, 20) connected to one another to form inner cooling channels (18, 19, 25, 26, 27) walls (10, 11), and which with through the cooling channels (18, 19, 25, 26, 27) flowing cooling medium (28, 29) is cooled on the inside, the cooling medium emerging at the rear edge (21) essentially parallel to the walls (10, 11) between the guide element (30),
characterized in that
the guide element (30) is produced in a casting process in such a way that the rear edge region (21) is cast with an overhang which extends the guide element (30) or its walls (10, 11) in the flow direction, and that the excess is removed in such a way after the casting is that at least a part of the ribs as throttling ribs (24) with the rear edge (21) are arranged essentially flush. A method according to claim 7, characterized in that the throughput of cooling medium (28, 29) through the finished guide element (30) essentially by dimensioning the between the throttle ribs (24) arranged outlet openings (25) is determined. Method according to one of the preceding claims, characterized in that that the casting process is a press casting process the protrusion is a length (b) behind the rear edge (21) has that the walls (10,11) at the outlet (21) around a slot thickness (c) of the cooling air channels (25) are spaced apart, and that in particular the length (b) of the supernatant in the range of 0.5 is up to 5 times as large, particularly preferably 1 to 3 times as large like slot thickness (c). Method according to one of the preceding claims, characterized in that that the throttle ribs (24) parallel to the rear edge (21) have a width (e) and spaced apart by a respective rib pitch (f) are arranged that the ratio of width (e) to rib pitch (f) is in the range of 0.25 to 0.75 that the thickness (d) of the Guide element (30) on the rear edge (21) in the range from 0.5 to 5 mm, is particularly preferably in the range from 1.0 to 2.5 mm, and that the slot thickness (c) of the cooling air ducts (25) between the walls (10,11) at the outlet (21) in the range from 0.3 to 2 mm, in particular is in the range of 0.8 to 1.5 mm. Method according to one of the preceding claims, characterized in that that the guide element is one in front of a turbine rotor arranged guide vane (30), and that as a cooling medium Air is used.

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