EP2846003B1 - Gas turbine, corresponding assembly and disassembly methods of a rotor of a gas turbine - Google Patents

Description

The present invention relates to a gas turbine, in particular an aircraft engine gas turbine, with a housing, a playpens and a segmented outer sealing ring for sealing this play screen, which is frictionally fastened by a clamping means to the housing, and a method for assembling and / or disassembling the play screen in the case.

From the US 2007/0231132 A1 For example, a gas turbine with a housing, a playpipe and a segmented outer sealing ring for sealing this playpipe is known, which is frictionally secured by a clamping means to the housing.

From the FR 2 891 583 A1 a gas turbine with the features of the preamble of claim 1 is known.

Usually such playpens are introduced during assembly due to the diverging in the flow direction flow channel and its correspondingly increasing diameter against the flow direction or from behind into the flow channel and secured in this. Accordingly, for disassembly of the first in the flow direction

Playpen first all subsequent playpens are dismantled. On the other hand, because of the thermo-mechanical stresses, the first playpens in the direction of flow must be serviced frequently and, for this purpose, dismantled or (re) mounted in the housing.

An object of an embodiment of the present invention is to improve the assembly and / or disassembly of a first, in particular in the flow direction, runway of a gas turbine.

This object is achieved by a gas turbine with the features of claim 1. Claims 7 and 9 provide a method for disassembly or assembly of a running grid of a corresponding gas turbine under protection. Advantageous embodiments of the invention are the subject of the dependent claims.

According to one aspect of the present invention, a gas turbine, in particular an aircraft engine gas turbine, a single- or multi-part housing having a, in particular at least substantially circular, flow channel inlet and a downstream flow channel outlet on. In one embodiment, a flow channel diverges between flow channel inlet and outlet, in particular due to an increasing relaxation of the working medium when flowing through the flow channel. Accordingly, in one embodiment, the flow channel outlet has a larger inner diameter than the flow channel inlet.

In the flow channel at least one playpens, in particular axially fixed, can be arranged, in particular arranged, which is preferably set up for converting flow energy into mechanical work. In one embodiment, a plurality of axially spaced apart playpens, in particular axially fixed, can be arranged, in particular arranged, whose outer diameters preferably increase in the direction of flow in the flow channel. The or the playpens can be releasably or permanently connected to a rotor of the gas turbine.

Radially between the housing and at least one of these playpens, in particular a first or foremost in the flow direction, playpen, which is arranged, in particular axially fixed, arranged in the housing, in particular, an outer sealing ring for sealing this play screen can be arranged, in particular arranged.

The outer sealing ring is frictionally secured by a one-piece or multi-part clamping means to the housing, in particular fastened, and has a plurality of ring segments, in particular it may consist of the plurality of ring segments or be composed. The clamping means in one embodiment has a cross section with a first leg which is supported on the housing, and a second leg, which is supported on the outer sealing ring and biases under elastic deformation of the clamping means radially against the housing and so frictionally secured thereto , In one embodiment, the clamping means on one or more C or U-clips on. In particular, a position of the outer sealing ring, when this is fixed by the clamping means to the housing, is referred to herein as the operating position. In general, an operating position refers in particular to a position of components when the gas turbine is ready for operation, in particular is operated.

According to one aspect of the present invention, the clamping means or the frictional attachment is first released by the clamping means for disassembly of the playpen. If the clamping means is designed in several parts, one or more, in particular all parts, in particular C or U-clips, can be released.

Then, in particular in the case of an axially fixed play rack, the sealing ring segments of the outer sealing ring are carried out of the housing counter to the direction of flow through the flow channel inlet, before the play cage is subsequently guided out of the housing against the direction of flow through the flow channel inlet. According to claim 7, all sealing ring segments of the outer sealing ring are carried out together from the housing, in another embodiment in groups or singly or sequentially.

In this way, according to one aspect of the present invention, a playpens first, in particular in the direction of flow, are advantageously dismantled, in particular without preceding removal of downstream playpens. For this purpose, a maximum outer diameter and / or an outer contour of the running grid is preferably at most as large as a minimum inner diameter or an inner contour of the flow channel inlet.

In one embodiment, the maximum outer diameter and / or circumference of the outer sealing ring frictionally secured to the housing or the maximum outer diameter and / or circumference of the outer sealing ring, when frictionally secured to the housing, is greater than the minimum inner diameter or circumference the flow channel entrance. According to one aspect of the present invention, such an outer sealing ring opposite to the direction of flow through the flow passage from the housing is carried out, preferably in still in an operating position axially fixed playpen or without prior axial displacement of the play grid in the flow direction.

For this purpose, according to one aspect of the present invention, one or more sealing ring segments are displaced radially inward after loosening the clamping means until their maximum outer diameter is at most as large as the minimum inner diameter of the flow channel inlet. As (maximum) outer diameter, in the present case, in particular a (maximum) radial distance of a radially outer contour from a rotational axis of the gas turbine is understood. Accordingly, a displacement of a sealing ring segment radially inward or on the axis of rotation to the (maximum) outer diameter of this sealing ring segment, a displacement of the sealing ring segments of the outer sealing ring radially inward according to the (maximum) outer diameter or circumference of the outer sealing ring.

mit:
n:  Anzahl der Dichtringsegmente des Außendichtrings;
u_i:  Spaltmaß zwischen i. Dichtringsegment und in Umfangsrichtung benachbartem Dichtringsegment in Betriebslage bzw. bei reibschlüssig durch das Klemmmittel an dem Gehäuse befestigtem Außendichtring;
${\displaystyle \sum _{i=1}^n{u}_i}:$

  Spaltmaßsumme bzw. Summe der Spaltmaße der Dichtringsegmente des Außendichtrings;
$\frac{{\displaystyle \sum _{i=1}^n{u}_i}}{\pi }:$

  Quotient der Spaltmaßsumme und der Kreiszahl;
D ₂₀ · π :  maximaler Außendurchmesser des reibschlüssig an dem Gehäuse befestigten Außendichtrings;
d ₁₆ · π :  minimaler Innendurchmesser des Strömungskanaleintritts.In particular, in order to enable such a radial displacement of sealing ring segments or such a radial compression of the outer sealing ring, according to the invention according to claim 1, a quotient of a sum of the gap between the frictionally secured in the operating position on the housing sealing ring segments or a Spaltmaßsumme the frictionally engaged in the Operating position on the housing attached outer sealing ring and the circle number π at least as large as a difference between a maximum outer diameter of the frictionally secured in the operating position on the housing outer sealing ring and a minimum inner diameter of the flow channel inlet: $$\frac{{\displaystyle \underset{i=1}{\overset{n}{\Sigma }}{u}_i}}{\pi }\ge \left(D_{20}-{\mathrm{<figure-callout\; id="16"\; label="d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">d</figure-callout>}}_{16}\right)$$

With:
n: number of sealing ring segments of the outer sealing ring;
u _i : gap between i. Sealing ring segment and circumferentially adjacent sealing ring segment in the operating position or at frictionally secured by the clamping means on the housing outer sealing ring;
${\displaystyle \underset{i=1}{\overset{n}{\Sigma }}{u}_i}:$

Gap total or sum of the gap dimensions of the sealing ring segments of the outer sealing ring;
$\frac{{\displaystyle \underset{i=1}{\overset{n}{\Sigma }}{u}_i}}{\pi }:$

Quotient of the gap and the circle number;
D ₂₀ · π : maximum outer diameter of the outer sealing ring frictionally secured to the housing;
d ₁₆ · π : minimum inner diameter of the flow channel inlet.

In other words, the gaps between the sealing ring segments of the outer sealing ring fastened to the housing in the operating position are at least large enough to allow the sealing ring segments to slide radially together until the radially compressed outer sealing ring has a sufficiently small outside diameter to carry it out of the flow channel entrance.

In particular, in order to provide sufficient radial play for such a radial displacement or compression, preferably without prior axial displacement of the play screen in the flow direction or arranged in the operating position playpen, according to one aspect of the present invention, one or more sealing ring segments after release the clamping means initially moved axially against the flow direction.

In particular, for this purpose, the sealing ring segments on a free axial path length against the flow direction. Under a free axial path length of a sealing ring segment opposite to the direction of flow in the present case in particular that Axialweg understood by which the sealing ring segment can be moved from its operating position after loosening the clamping means purely axially against the flow direction until it contacts the housing form-fitting or this another purely axial Displacement against the flow direction positively prevented. In other words, corresponds to a free axial path length of a sealing ring segment opposite to the flow direction an axial clearance of the sealing ring segment after loosening the clamping means against the flow direction or an axial gap in the operating position between a contact line of the housing and a contact line of the sealing ring segment, along the sealing ring segment and housing contact each other, when the sealing ring segment is moved purely axially against the flow direction after loosening the clamping means from the operating position.

In accordance with one aspect of the present invention, the gas turbine has an anti-rotation locking device between the outer sealing ring and the housing, which is non-conforming to the throughflow direction. In particular, one or more, in particular all sealing ring segments after loosening the clamping means initially, in particular successively, in groups or together, axially against the direction of flow at least be moved until this rotation between outer seal and housing is disengaged or is.

In particular, according to one aspect of the present invention, the free axial path length of one or more, in particular all sealing ring segments opposite to the flow direction at least as large as an axial engagement of the rotation. Under axial engagement a contrary to the flow direction formschlussfreien rotation is understood in the present case in particular that Axialweg understood by the sealing ring segment from its operating position after loosening the clamping means purely axially against the flow direction must be moved until the rotation also comes out of engagement in the circumferential direction or is.

In one embodiment, the anti-rotation comprises a groove arrangement with one or more circumferentially distributed axial grooves in the housing, which are open against the flow direction and in each of which a radial flange of the outer sealing ring in the circumferential direction positively engages when it frictionally secured in the operating position on the housing is. Then preferably the free axial path length of one or more, in particular all sealing ring segments opposite to the flow direction at least as large as a maximum groove length of this groove arrangement. Since the maximum groove length limits the maximum axial engagement, so can advantageously be ensured regardless of an axial cross-section of the radial flanges sufficient free axial path length to bring them out of engagement.

According to one aspect of the present invention, the gas turbine has a radial suspension of the outer sealing ring on or in the housing. In particular, one or more, in particular all sealing ring segments after loosening the clamping means, in particular successively, in groups or together, initially at least axially against the flow direction at least until this radial suspension is disengaged or is.

In one embodiment, the radial suspension on an inner surface of the outer sealing ring, which engages over an outer surface of the housing from radially outside axially when it is frictionally secured in the operating position on the housing. In particular, the outer sealing ring may have an axial flange which engages axially over or radially behind a corresponding radial groove in the housing, in particular a subsequent guide grid, when the outer sealing ring is frictionally secured to the housing in the operating position. The axial length on which the outer sealing ring engages over the housing axially or radially behind, is referred to herein as the axial overhang of the radial suspension. Accordingly, in one embodiment, the free axial path length of one or more, in particular all sealing ring segments opposite to the flow direction at least as large as an axial overhang of the radial suspension of the outer sealing ring. Especially In this way, a sufficient free axial path length can be ensured in order to disengage the radial suspension of the outer sealing ring and thus to radially compress the outer sealing ring.

According to one aspect of the present invention, the playpen has one or more sealing fins or, preferably, ring-like, radial flanges, which protrude radially outwards from an outer cover strip of the playpens and are radially opposite sealing surfaces of the sealing ring segment. In the operating position, such sealing fins can be offset axially relative to a downstream edge of a sealing surface for sealing this sealing fin against the direction of flow. In other words, the sealing fin may be arranged in the operating position upstream of the downstream edge of the sealing surface, so that the sealing fin can prevent radial compression of the outer sealing ring.

In particular, therefore, according to one aspect of the present invention, the free axial path length of one or more, in particular all sealing ring segments opposite to the flow direction at least as large as an axial offset of a sealing fin of the outer sealing ring against the flow direction, in particular its upstream, radially outer edge, opposite a downstream edge a sealing surface of the sealing ring segment for sealing this sealing fin. In one embodiment, the sealing surface merges in the downstream edge in a, preferably at least substantially radial, end face, so that in one embodiment, the free axial path length of one or more, in particular all sealing ring segments against the flow direction at least as large as an axial offset of a sealing fin the outer sealing ring against the direction of flow, in particular its upstream, radially outer edge, opposite a downstream end side, which adjoins a sealing surface for sealing this Dichtfinne and preferably, at least substantially, extends radially.

If the playpen has a first and a second sealing fin axially spaced from the first sealing fin, the stepped outer sealing ring has a first sealing surface for sealing the first sealing fin and a second sealing surface for sealing the second sealing fin axially and radially spaced from the first sealing surface is, in one embodiment, the free axial path length of one or more, in particular all sealing ring segments opposite to the flow direction at least as large as an axial offset of the first sealing fin, in particular its radial outer upstream edge, opposite a downstream edge of the first sealing surface and / or an adjoining, in particular at least substantially radial end side, and additionally at least as large as an axial offset of the second sealing fin, in particular its radially outer upstream edge opposite a downstream edge of the second Sealing surface and / or an adjoining, in particular at least substantially radial end face.

In particular, thereby one or more, in particular all sealing ring segments after loosening the clamping means, in particular successively, in groups or together, initially at least axially against the flow direction are shifted until the sealing fin (s) downstream or behind the downstream edge of the respective sealing surface is arranged or are radially opposite the sealing fin in the operating position. In this way, sufficient radial clearance for a radial displacement or compression can be made available to perform the radially compressed outer sealing ring with radially inwardly displaced sealing ring segments against the direction of flow from the flow channel inlet.

The above-described axial and radial displacements can, at least in sections, be carried out in succession. In particular, the sealing ring segments of the outer sealing ring can be displaced successively, in groups or all together initially, at least substantially, purely axially against the direction of flow, until in particular an anti-twist device and / or a radial suspension are disengaged and / or sealing fins are arranged downstream behind their sealing surfaces, then, at least substantially, are moved purely radially inward until their maximum outer diameter is at most as large as the minimum inner diameter of the flow channel inlet, and then, at least substantially, purely axially against the direction of flow through this are displaced from the housing.

Similarly, the above-described axial and radial displacements, at least in sections, can be executed in parallel or superimposed. In particular, the sealing ring segments of the outer sealing ring can be displaced in succession, in groups or all together radially inwards and at the same time axially against the direction of flow.

In one embodiment, one or more, in particular all sealing ring segments, at least substantially, tilt-free axially and / or radially displaced and / or executed from the flow channel inlet. This is understood in the present case in particular that in this disassembly an upstream edge of a sealing ring segment, at least substantially, not further moved radially inward or outward than a downstream edge of this sealing ring segment. As a result, the handling can be facilitated in particular.

An assembly of the playpen takes place according to the invention according to claim 9, at least substantially, analogously in the reverse order. First, the playpen can be introduced in the flow direction through the flow channel inlet into the housing and preferably axially fixed in the operating position. Subsequently, the sealing ring segments of the outer sealing ring are all introduced together, in the flow direction through the flow channel inlet into the housing, before subsequently the outer sealing ring is frictionally secured by the clamping means or this on the housing.

In one embodiment, the sealing ring segments of the outer sealing ring, preferably individually, in groups or all together, moved before attaching the clamping means, in particular tilt-free, radially outward to their operating position in which their maximum outer diameter is greater than the minimum inner diameter of the flow channel inlet, and at least in sections parallel thereto or successively axially displaced in the flow direction until the rotation and / or radial suspension is engaged and / or one or more, in particular all sealing fins are offset from the downstream edge of the respective sealing surface against the flow direction.

Fig. 1

einen Teil einer Gasturbine nach einer Ausführung der vorliegenden Erfindung in einem Axialschnitt längs einer Drehachse; und

Fig. 2

einen Teil der Gasturbine der Fig. 1 in einer in Fig. 1 mit II angedeuteten Draufsicht.

Further advantageous developments of the present invention will become apparent from the dependent claims and the following description of preferred embodiments. This shows, partially schematized:

Fig. 1

a portion of a gas turbine according to an embodiment of the present invention in an axial section along an axis of rotation; and

Fig. 2

a part of the gas turbine of Fig. 1 in an in Fig. 1 with II indicated top view.

Fig. 1 shows in Fig. 2 the abovementioned US 2007/0231132 A1 Similarly, a portion of a gas turbine according to an embodiment of the present invention in an axial section along a horizontal axis of rotation. On the US 2007/0231132 A1 reference is additionally made, in particular, mutually corresponding elements are denoted by identical reference numerals, so that in the following, particular attention is given to differences.

The gas turbine has a housing 16 with a circular flow channel inlet, whose minimum inner diameter is denoted by d ₁₆ .

In an in Fig. 1, 2 shown operating position is in the flow channel in a flow direction (from left to right in Fig. 1 ) first playpen 18 is arranged. Radial between the housing and playpen an outer sealing ring for sealing this play screen is arranged, which is frictionally secured by a clamping means in the form of several C-clips 80 to the housing and a plurality of ring segments 20 _i , 20 _{i + 1} , ..., which in the circumferential direction by gap dimensions u _i , ... are spaced from each other (see. Fig. 2 ).

The sealing ring segments have opposite the direction of flow on a free axial path length a _f , in Fig. 1 indicated by an arrow. After loosening the C-clip, the sealing ring segments can be moved purely axially against the flow direction by a _f until the housing limits a further purely axial displacement against the direction of flow.

This free axial path length a _f is greater than an axial engagement a _{1 of} an anti-rotation against the flow direction formschlussfreien rotation of the outer sealing ring. The anti-rotation device has a groove arrangement with several counter to the direction of flow (to the left in FIG Fig. 1 ) open axial grooves 12 in the housing, in each of which a radial flange 11 of the frictionally secured to the housing outer sealing ring engages in a form-fitting manner in the circumferential direction. The maximum groove length a _{1 of} the groove arrangement may correspond, at least substantially, to the axial engagement of the anti-twist device.

The free axial path length a _f is at the same time greater than an axial overhang a _{2 of} a radial suspension 23 of the outer sealing ring. The axial overhang a ₂ is defined by the axial length a ₂ , on which an axial flange 22 of the outer sealing ring has a radial groove 21 of the housing in the axial direction (horizontal in FIG Fig. 1 ) overlaps or in the radial direction (vertically in Fig. 1 ) engages behind. The radial groove of the housing is represented by a guide grid, which in Fig. 1 hinted at.

The playpens has a first sealing fin 31 and a second sealing fin 41, which is axially spaced from the first sealing fin. The thus stepped outer sealing ring has a first, kinked sealing surface for sealing the first sealing fin and a second, straight sealing surface for sealing the second sealing fin, which is axially and radially spaced from the first sealing surface.

The free axial path a _f is also greater than an axial offset a _{3 of} the first sealing fin with respect to a downstream edge 32 of the first sealing surface and greater than an axial offset a _{4 of} the second sealing fin opposite a downstream edge 42 of the second sealing surface.

wobei in der Betriebslage der maximale Außendurchmesser des Außendichtrings größer ist als der minimale Innendurchmesser des Strömungskanaleintritts.A quotient of a clearance measure of the outer sealing ring frictionally secured to the housing in the operating position and the circle number π is greater than or equal to a difference between the maximum outer diameter D ₂₀ of the outer sealing ring frictionally secured to the housing in the operating position and the minimum inner diameter d _{16 of} the flow channel entry: $$\frac{{\displaystyle \underset{i=1}{\overset{n}{\Sigma }}{u}_i}}{\pi }\ge \left(D_{20}-{\mathrm{<figure-callout\; id="16"\; label="d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">d</figure-callout>}}_{16}\right)$$

wherein in the operating position, the maximum outer diameter of the outer sealing ring is greater than the minimum inner diameter of the flow channel inlet.

To disassemble the playgrid, one or more, preferably all C-clips 80 are first released.

Subsequently, the sealing ring segments 20 _i , 20 _{i + 1} ,... Of the outer sealing ring are executed individually, in groups or all together against the direction of flow through the flow channel inlet from the housing 16.

For this purpose, the sealing ring segments after release of the clamping means 80 are tilt-free axially displaced against the flow direction until the rotation 10 and the radial suspension 23 are disengaged and the sealing fins 31, 41 downstream of the edges 32 and 42 of the associated sealing surfaces are arranged (right in Fig. 1 ).

d.h. der komprimierte Außendurchmesser D'₂₀ ist kleiner als der Innendurchmesser d₁₆ des Strömungskanaleintritts. Somit können die Dichtringsegmente 20_i, 20_i+1,... des Außendichtrings einzeln, gruppenweise oder alle gemeinsam axial weiter entgegen der Durchströmungsrichtung verschoben und so durch den Strömungskanaleintritt aus dem Gehäuse 16 ausgeführt werden.Subsequently, the sealing ring segments 20 _i , 20 _{i + 1} , ... of the outer sealing ring are moved individually, in groups or all together radially inward until their maximum outer diameter is as large as or smaller than the minimum inner diameter d _{16 of} the flow channel inlet. This is possible due to the clearance total. Denotes D _'20 the maximum outer diameter of the radially compressed outer sealing ring with radially inwardly displaced sealing ring segments, so that they abut each other in the circumferential direction or their Spaltmaßsumme is equal to zero, then: $$\begin{array}{l}\left(D_{20}-D{\text{'}}_{20}\right)\cdot \pi ={\displaystyle \underset{i=1}{\overset{n}{\Sigma }}{u}_i}\ge \left(D_{20}-{\mathrm{<figure-callout\; id="16"\; label="d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">d</figure-callout>}}_{16}\right)\cdot \pi \Rightarrow \\ D{\text{'}}_{20}\le {\mathrm{<figure-callout\; id="16"\; label="d"\; filenames="imgf0001.png"\; state="\{\{state\}\}">d</figure-callout>}}_{16}\end{array}$$

ie the compressed outer diameter D _'20 is smaller than the inner diameter d _{16 of} the flow channel inlet. Thus, the sealing ring segments 20 _i , 20 _{i + 1} , ... of the outer sealing ring individually, in groups or all together axially displaced further against the flow direction and are carried out through the flow channel inlet from the housing 16.

Subsequently, the playpen 18 is carried out against the direction of flow through the flow channel inlet from the housing.

The assembly is carried out in an analogous manner in the reverse order: first, the playpen is inserted in the flow direction through the flow channel inlet into the housing and fixed axially in the operating position. Then, the sealing ring segments of the outer sealing ring are introduced in the flow direction through the flow channel inlet into the housing.

For this purpose, the sealing ring segments of the radially compressed outer sealing ring individually, in groups or all together are displaced or introduced axially in the flow direction through the flow channel inlet into the housing 16. Subsequently, the sealing ring segments 20i, 20 _{i + 1} , ... of the outer sealing ring individually, in groups or all moved together radially outward until they rest radially on the housing. Then they are moved further in the direction of flow in the operating position in which the rotation 10 and the radial suspension 23 are engaged and the sealing fins 31, 41 upstream of the edges 32 and 42 of the associated sealing surfaces are arranged. Finally, the clamping means 80 and thereby the outer sealing ring is frictionally secured to the housing.

Although exemplary embodiments have been explained in the foregoing description, it should be understood that a variety of modifications are possible. It should also be noted that the exemplary embodiments are merely examples that are not intended to limit the scope, applications and construction in any way. Rather, the expert is given by the preceding description, a guide for the implementation of at least one exemplary embodiment, with various changes, in particular with regard to the function and arrangement of the components described, can be made without departing from the scope, as it turns out the claims.

LIST OF REFERENCE NUMBERS

10

twist

11

Radial flange (rotation lock)

12

Axial groove (rotation lock)

16

casing

18

pen

20 _i , 20 _{i + 1}

Outer sealing ring segment

21

Radial groove of the housing (radial suspension)

22

Axial flange of outer seal (radial suspension)

23

radial suspension

31/41

first / second sealing fin

32/42

downstream edge of the sealing surface of the first / second sealing fin

80

Clamping means (C-clips)

a _f

free axial path length

a ₁

axial engagement of the anti-rotation device; maximum groove length

a ₂

axial overhang of the radial suspension

a ₃ / a ₄

axial offset of the first / second sealing fin

₁₆

minimum inner diameter of the flow channel inlet

D ₂₀

maximum outer diameter of the outer sealing ring in operating position

u _i

Gap between sealing segments 20 _i , 20 _{i + 1}

Claims (10)

1. Gas turbine, in particular an aircraft engine gas turbine, comprising: a housing (16) having a flow channel inlet; a rotating cascade (18), which is a first rotating cascade in particular in the flow direction, which can be arranged in the housing; and an outer sealing ring for sealing said rotating cascade, which ring can be frictionally fastened to the housing by a clamping means (80) and has a plurality of ring segments (20_i, 20_i+1);
   characterized in that a quotient of a clearance sum $\left({\displaystyle \sum _{i=1}^n{u}_i}\right)$

   

   of the outer sealing ring frictionally fastened to the housing and pi (π) is at least as large as a difference between a maximum outer diameter (D₂₀) of the outer sealing ring frictionally fastened to the housing and a minimum inner diameter (d₁₆) of the flow channel inlet of the housing $\left({\displaystyle \sum _{i=1}^n{u}_i\ge \left(D_{20}-d_{16}\right)\cdot \pi }\right).$

   
2. Gas turbine according to claim 1, characterized in that a free axial path length (a_f) of a sealing ring segment counter to the flow direction is at least as large as:

   - an axial engagement (a₁) of an anti-torsion mechanism (10) of the outer sealing ring (a_f ≥ a₁), which mechanism does not have a form-fit counter to the flow direction, and/or

   - an axial overhang (a₂) of a radial mounting (23) of the outer sealing ring (a_f ≥ a₂) and/or

   - an axial offset (a₃, a₄) of a sealing fin (31, 41) of the outer sealing ring counter to the flow direction with respect to a downstream edge (32, 42) of a sealing surface of the sealing ring segment for sealing said sealing fin (a_f ≥ a₃, a₄).
3. Gas turbine according to claim 2, characterized in that the anti-torsion mechanism has a groove arrangement comprising at least one axial groove (12) in the housing, which groove is open counter to the flow direction and into which a radial flange (11) of the outer sealing ring frictionally fastened to the housing form-fittingly engages in the circumferential direction, the free axial path length of the sealing ring segment counter to the flow direction being at least as large as a maximum groove length (a₁) of the groove arrangement (a_f ≥ a₁).
4. Gas turbine according to either claim 2 or claim 3, characterized in that the rotating cascade has a first and a second sealing fin (31, 41) that is axially spaced apart from the first sealing fin, the stepped outer sealing ring having a first sealing surface for sealing the first sealing fin and a second sealing surface for sealing the second sealing fin, which second sealing surface is axially and radially spaced apart from the first sealing surface, and the free axial path length of the sealing ring segment counter to the flow direction is at least as large as an axial offset (a₃) of the first sealing fin with respect to a downstream edge (32) of the first sealing surface and at least as large as an axial offset (a₄) of the second sealing fin with respect to a downstream edge (42) of the second sealing surface.
5. Gas turbine according to any of the preceding claims, characterized in that the maximum outer diameter of the outer sealing ring frictionally fastened to the housing is greater than the minimum inner diameter of the flow channel inlet.
6. Gas turbine according to any of the preceding claims, characterized in that the rotating cascade is designed to convert flow energy into mechanical work and/or a flow channel outlet of the housing has a larger inner diameter than the flow channel inlet of the housing.
7. Method for disassembling the rotating cascade of a gas turbine according to any of the preceding claims, characterized by the following steps:

   releasing the clamping means;

   jointly guiding all of the sealing ring segments of the outer sealing ring counter to the flow direction through the flow channel inlet and out of the housing; and

   guiding the rotating cascade counter to the flow direction through the flow channel inlet and out of the housing.
8. Method according to the preceding claim, characterized in that, after the clamping means is released, sealing ring segments are axially displaced, in particular without tilting and/or jointly, counter to the flow direction until the anti-torsion mechanism and/or radial mounting is disengaged and/or the sealing fin is arranged downstream of the edge; and/or are displaced radially inwards until their maximum outer diameter is at most as large as the minimum inner diameter of the flow channel inlet.
9. Method for assembling the rotating cascade of a gas turbine according to any of the preceding claims, characterized by the following steps:

   inserting the rotating cascade in the flow direction through the flow channel inlet and into the housing;

   jointly inserting all the sealing ring segments of the outer sealing ring in the flow direction through the flow channel inlet and into the housing; and

   fastening the clamping means.
10. Method according to the preceding claim, characterized in that, before the clamping means is fastened, sealing ring segments are axially displaced, in particular without tilting and/or jointly, in the flow direction until the anti-torsion mechanism and/or radial mounting is engaged and/or the sealing fin is offset with respect to the edge counter to the flow direction; and/or are displaced radially outwards until their maximum outer diameter is larger than the minimum inner diameter of the flow channel inlet.

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