EP2360352A2 - Screw-free intermediate stage seal of a gas turbine - Google Patents

Abstract

The intermediate stage seal arrangement has a radial outer ring (1), which is connected with guide vanes (2), and a radial inner ring (3), which is supported at the outer ring. The inner ring is fixed relative to the outer ring in axial direction by multiple holding elements (7).

Description

The invention relates to an interstage seal arrangement of a gas turbine, and more particularly to a gas turbine having a screwless interstage seal construction.

In turbine stages of gas turbines, it is known to screw the rotor disks together. This takes place during assembly so that the arranged between adjacent rotor disks intermediate stage seal are already pre-assembled. These are to be designed so that the accessibility to the disc flanges of the rotor discs ensures their screwing and on the other hand, the sealing function is met.

The prior art shows constructions in which the interstage seal assembly consists of two rings which are either individually secured to the vanes independently of each other or which are bolted together. Another known embodiment is the division into two half-rings, which must be mounted after screwing the rotor disks.

In the known embodiments with screwed rings, it proves to be disadvantageous that the screw connection of the interstage seal parts is exposed to high temperatures. In case of failure of the screw (breakage of individual screws) results in damage to the rotor discs. Furthermore, the screwing involves the risk that other components may be damaged during the assembly process, for example, a Christmas tree toothing on the disc. Furthermore, the screw creates a turbulence of the air flows between the rotor and stator and thus generates an air resistance, which counteracts the rotation. The turbulence also leads to an increase in the air temperature, which has a negative effect on the disk temperature and the cooling air temperature for the subsequent blade. Another major drawback is that the material choice for the rings of the interstage seal assembly is limited since the relative radial displacement due to differential thermal expansion is minimized must be reduced in order to prevent slippage of the flange and the associated bending load of the screws.

In the known from the prior art solutions with two separate interstage seal rings is a statically indeterminate system, which can occur by component tolerances constraining forces between the front ring and the rear ring (seen in the direction of flow of the gas turbine). In one of the rings is usually the pressure difference of the surrounding air so low that no or only small axial forces act. This can lead to vibrations and increased wear. The production of very costly vane requires increased processing costs. Furthermore, additional sealing strips or sealing elements are required between the vane segments. The ring carrying the interstage seal is also exposed to a high radial temperature gradient in this design.

In split interstage seal rings an increased amount of processing is required. In particular, elaborate milling work is necessary. Such an assembly is matched with respect to their elements, so that individual elements (for example, half-rings) can not be replaced individually. Furthermore, such a system-inherently non-rotationally symmetrical construction is exposed during operation to asymmetrical thermal expansions, so that such components can deform from a circular shape into an oval shape. As a result, an increased cold gap may be required and thus result in increased leakage.

The invention has for its object to provide an intermediate stage seal arrangement of a gas turbine of the type mentioned, which avoids the disadvantages of the prior art with a simple structure and simple, cost-effective manufacturability and in particular has good structural properties.

According to the invention the object is achieved by the combination of features of claim 1, the dependent claims show further advantageous embodiments of the invention.

According to the invention, it is thus provided that the interstage seal arrangement has a (radially) outer ring, which is held both axially by guide vanes Also centered and thus stored, and a (radial) inner ring which is mounted on the outer ring comprises. The terms (radially) outer and (radial) inner refer to the axis of rotation or machine axis. With the terms front and rear reference is made to the direction of flow of the gas turbine, front thus means closer to the inlet region, while rear means closer to the outlet.

According to the invention, each of the rings, namely the outer ring and the inner ring, is provided with at least one sealing area to perform the function of an interstage seal arrangement.

Furthermore, the invention provides that the inner ring on the outer ring by at least three radial tongue and groove connections, referred to below Radialnutenzentrierung centered and is secured against rotation in the circumferential direction. The planes of symmetry of all tongue and groove joints must all contain the main axis of rotation of the components involved to prevent deformation or damage. This principle corresponds to the state of the art and is u.a. also used for the centering of the outer ring by the vanes. It allows different thermal expansions of the components involved while ensuring coaxiality.

With respect to the axial fixation of the outer ring by engaging in the circumferential groove (outwardly open groove) strips of the guide vanes may be made to the prior art. The inner ring, however, is secured axially to the rear by an annular projection of the outer ring. The engagement of the inner ring on the outer ring is ensured in operation by the pressure differential between the front, first stage and located behind the interstage seal assembly second stage. At a standstill, the inner ring could move forward. However, this is prevented according to the invention by means of a plurality of holding elements. According to the invention, these holding elements can be disassembled even from the outside in order to enable a displacement of the inner ring to the front or of the outer ring to the rear for screwing the rotor disks. According to the invention, the holding elements are themselves secured against falling out by the strips of the guide vanes.

The circumferential groove in the outer ring can be designed for inserting retaining elements. As a result, the circumferential groove is provided either over the entire peripheral region or over part of its circumference with a larger axial width, which makes it possible to introduce additional holding elements in addition to the strip of the guide vane. At the periphery, for example, three such holding elements are provided which are sufficient to secure the inner ring against axial slipping when the engine is at a standstill.

To increase the sealing effect between the outer ring and the inner ring, it may be advantageous if the outer ring and / or the inner ring is provided at the respective contact area with a ring bead-shaped sealing projection.

In an alternative embodiment of the invention, it is also possible to provide inwardly facing retaining elements which are formed on the strip of the vane itself, either as pins which are pressed into radial bores of the strip, or as extensions of portions of the strip in the radial direction ,

According to the invention is further provided in a preferred embodiment of the invention that retaining elements are pressed into radial holes of the outer ring and these pin-like holding elements take over the retention function for the inner ring. The pin-like holding elements can be designed so that they ensure both the centering between guide vanes and outer ring and between the outer and inner ring.

According to the invention, it is thus possible, at the same time, distributed over the circumference, to provide a plurality of the pin-like holding elements (retaining elements) which simultaneously serve as centering elements for both the outer ring and the inner ring and assume an axial securing function. By assuming the centering function by the holding elements provided in the prior art additional Radialnutenzentrierungen can be omitted. This results in a simpler construction, which results in both lower costs and lower weight. Due to the interference fit of the retaining elements with the outer ring, the occurrence of leakage is further reduced or eliminated altogether.

The introduction of the radial bores in the outer ring according to the invention is easily possible, in particular, no further modifications to the guide vanes or the feet of the vanes are required. This also results in a significant cost savings.

According to the invention it is thus possible in a particularly favorable manner, to manufacture the outer ring and the inner ring of different materials, so that the outer ring and the inner ring can be optimized in terms of their thermal stresses.

• Eliminierung des Fehlerfalles "Versagen der Verschraubung";
• Geringere Strömungsverluste durch Wegfall der Verschraubung;
• Werkstoffe können unabhängig für eine optimale Funktion gewählt werden, z.B. optimales Spaltverhalten für den inneren Ring und hochtemperaturbeständiger Werkstoff für den äußeren Ring.

All variants of the solution according to the invention address or eliminate the disadvantages of the constructions known from the prior art, in particular:

• Elimination of the error case "Failure of the screw connection";
• Lower flow losses due to elimination of the screw connection;
• Materials can be independently selected for optimum performance, eg optimal splitting behavior for the inner ring and high temperature resistant material for the outer ring.

Fig. 1

eine axiale Teil-Schnittansicht einer erfindungsgemäßen Zwischenstufendichtungsanordnung gemäß einem ersten Ausführungsbeispiel,

Fig. 2

eine vereinfachte Teil-Ansicht längs der Schnittlinie AA-AA gemäß Fig. 1,

Fig. 3

eine Ansicht eines abgewandelten Ausführungsbeispiels, analog Fig. 1,

Fig. 4

eine Ansicht, analog Fig. 1, eines weiteren Ausführungsbeispiels,

Fig. 5

eine weitere Ausführungsvariante gemäß der Erfindung in vergrößerter Schnittansicht analog den Fig. 1 bis 4, und

Fig. 6

eine Schnittansicht längs der Linie AB gemäß Fig. 5.

In the following the invention will be described by means of embodiments in conjunction with the drawing. Showing:

Fig. 1

FIG. 2 is a partial axial sectional view of an interstage seal assembly according to a first embodiment of the present invention; FIG.

Fig. 2

a simplified partial view along the section line AA-AA according to Fig. 1 .

Fig. 3

a view of a modified embodiment, analog Fig. 1 .

Fig. 4

a view, analog Fig. 1 , another embodiment,

Fig. 5

a further embodiment according to the invention in an enlarged sectional view analogous to Fig. 1 to 4 , and

Fig. 6

a sectional view taken along the line AB according to Fig. 5 ,

In the embodiments, the same parts are each provided with the same reference numerals. For clarity, is in the FIGS. 1 to 4 dispensed with the representation of Radialnutenzentrierung.

The Fig. 1 shows a first embodiment in which an outer interstage seal ring 1 and an inner interstage seal ring 3 are provided, which respectively include respective sealing portions 4, 5, 6. With regard to the dimensioning of the construction of the sealing regions 4, 5, 6, reference may be made to the prior art.

The outer ring 1 comprises a circumferentially extending, radially outwardly open groove 12, in which a radially inwardly facing bar 11 of a foot of a guide vane 2 is inserted. The guide vanes 2 are formed according to the prior art and segmented in the circumferential direction, wherein in each case a plurality of guide vanes 2 may have a common foot 16.

The Fig. 1 to 3 further show a disc 17 of a stage 1 of a turbine with rotor blades 19, and a disc 18 of a stage 2, which is located downstream of the intermediate stage seal assembly according to the invention, with rotor blades 20. With respect to the discs 17, 18 and the rotor blades 19, 20 can the state the technique be referenced.

At the in Fig. 1 In the embodiment shown, the outer ring 1 comprises a circumferentially extending, radially outwardly open groove 12 (see above), which is provided in the axial direction with an additional, widening groove 15, which merges into a recess 14 which extends radially inwardly opens. Into the groove 15 is (see also Fig. 2 ) a holding element 7 is inserted, which (see Fig. 2 ) Is T-shaped and the foot 21 passes through the recess 14. The Retaining element 7 is held by the strip 11 after its assembly and thus extends with its foot radially inwards.

Radially inward to the outer ring 1, the inner ring 3 is arranged. This rests against an annular projection 10 of the outer ring 1 and is thus supported in the axial direction. The annular projection 10 thus forms an abutment leg and fixes the inner ring 3, wherein the inner ring 3 is provided on its radial outer side with a space for thermal expansion relative to the outer ring 1. On the opposite side of the annular projection 10, the inner ring 3 is fixed by the holding element 7. Distributed over the circumference, for example, three such retaining elements 7 are provided.

The Fig. 2 shows in simplified representation a view along the line AA-AA of Fig. 1 , As a result, it can be seen that the retaining element 7 is inserted into the groove 15 and is thus fixed radially, so that a reliable condition is ensured during operation of the gas turbine.

The construction according to the invention has the advantage that when mounting the interstage seal arrangement or the gas turbine, the inner ring 3 can be mounted on the outer ring 1 in a simple manner. Subsequently, the holding elements 7 are then inserted and the guide vanes 2 inserted.

The nose 28 on the inner ring 3 can be used in vertical mounting for holding the inner ring 3.

The Fig. 3 shows a modified embodiment in which a holding element 8 is formed as a pin-shaped extension of the strip 11, which passes through the recess 14 and thus directly secures the inner ring 3 against displacement forward when the vane 2 is mounted. From the representation of Fig. 3 Thus, it follows that the several retaining elements 8 uniformly distributed around the circumference are part of the strip 11 (guide blade rail) and thus serve simultaneously as axial retaining elements for both the outer ring and the inner ring.

At the in Fig. 4 the embodiment shown, the respective holding element 9 is formed in the form of a pin which is pressed into a radial bore of the strip 11.

The FIGS. 5 and 6 show by way of example a further modification variant of the solution according to the invention. The same parts are again provided with the same reference numerals.

After screwing the rotor, the inner 3 and outer 1 ring are brought into the illustrated position. At least 3 holding elements 22 are now introduced from the outside into radial bores of the outer ring 1, wherein an inner part 26 of the holding element 22 engages in a groove of the inner ring 3. Now, all holding elements 22 are finally pressed into their stop in the outer ring 1, wherein a central part 25 of the holding member 22 and the corresponding bore in the outer ring 1 are designed as a press fit. Hereby, both rings 1, 3 are secured against each other and centered. An outer part 23 of at least 3 holding elements 22 finally engages in radial grooves 27 of the guide blade 11, whereby the centering of the outer ring 1 and thus the entire assembly is ensured by the guide vanes 2.

For disassembly 22 recesses 24 are provided on the holding element, to which a removal tool can be attached.

According to the invention thus results in the advantage that a failure of glands can be excluded because no glands between the outer ring and the inner ring are provided. This also results in lower flow losses, since the surfaces of the outer ring and the inner ring can each be streamlined optimized.

A significant advantage results according to the invention in that the choice of material for the outer ring and for the inner ring can be optimized separately and thus, for example, an optimal splitting behavior for the inner ring, while the outer ring, a high temperature resistant material can be selected.

Another advantage may result in a weight saving as well as a reduction of the components and an associated reduction of the assembly costs.

LIST OF REFERENCE NUMBERS

1

Outer ring

2

Vane-

3

Inner ring

4

sealing area

5

sealing area

6

sealing area

7

retaining element

8th

retaining element

9

retaining element

10

Ring-shaped approach

11

strip

12

Circumferential groove / groove

13

sealing projection

14

recess

15

groove

16

foot

17

Level 1 disk

18

Level 2 disk

19

rotor blade

20

rotor blade

21

foot

22

retaining element

23

outer part

24

recess

25

middle part

26

inner part

27

radial groove

28

nose

Claims (13)

Intermediate gasket arrangement of a gas turbine with a radially outer ring (1) which is mounted in guide vanes, and with a radially inner ring (3) which is mounted directly on the outer ring (1), wherein the inner ring (3) in one axial Direction by a simultaneously serving as a seal annular projection (10) of the outer ring (1) is axially positioned and by means of a plurality of removable, the outer ring (1) penetrating retaining elements (7, 8, 9, 22) relative to the outer ring (1 ) is held in the other axial direction, Intermediate seal assembly according to claim 1, characterized in that the annular projection (10) by means of a Radialnutenzentrierung for positive retention in the circumferential direction with the inner ring (3) is connected. Interstage seal arrangement according to one of claims 1 or 2, characterized in that the guide vanes (2) are each provided with a radially extending, annular ring-like strip (11) which is introduced into a radial groove (12) of the outer ring (1). Interstage seal arrangement according to claim 3, characterized in that in the circumferential groove (12) holding elements (7) are inserted, which fix the inner ring (3) in the axial direction. Interstage seal arrangement according to claim 3 or 4, characterized in that on the strip (11) radially inwardly facing holding elements (8, 9) are arranged, which fix the inner ring (3) in the axial direction. Intermediate seal assembly according to claim 4 or 5, characterized in that the circumferential groove (12) facing radially inward Recesses (14) for carrying out the holding elements (7, 8, 9, 22) is formed. Intermediate seal assembly according to one of claims 2 to 6, characterized in that on the axial annular projection (10) of the outer ring (1) and / or on the contact region of the inner ring (3) is formed a ring bead-shaped sealing projection (13). Interstage seal arrangement according to one of claims 2 to 7, characterized in that the tongue and groove-like compound on one of the rings (1) fixed axial pins which engage in corresponding recesses of the other ring (3). Interstage seal arrangement according to one of claims 1 to 8, characterized in that the holding elements (22) are inserted by means of a press fit into the recesses of the outer ring (1). Intermediate seal assembly according to one of claims 1 to 9, characterized in that the outer ring (1) and the inner ring (3) are made of different materials. Intermediate seal assembly according to one of claims 1 to 10, characterized in that the holding elements (8, 9, 22) are simultaneously part of Radialnutenzentrierung the inner ring (3) and thus center against the outer ring (1) and fix it in the circumferential direction. Interstage seal arrangement according to one of claims 1 to 11, characterized in that the holding elements (22) are simultaneously part of the Radialnutenzentrierung the outer ring (1) and thus the outer ring (1) against the guide vanes (2) and the inner ring (3) Center against the outer ring (1) and fix in the circumferential direction. Intermediate seal assembly according to one of claims 1 to 12, characterized in that a nose (28) on the inner ring (3) allows the holding of the inner ring (3) when mounted vertically.

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