EP1408200B1 - Turbine shroud segment attachment - Google Patents

Description

The invention relates to a Turbinendeckbandsegmentbefestigung with a housing and a plurality of arranged in the housing shroud segments.

From the prior art it is known to seal the gap at a rotor blade tip by means of shroud segments. It is also known that the gap between the tip of the rotor blade and the shroud changes depending on the thermal expansion or contraction of both the rotor blade and the housing. Too large a gap leads to flow losses, while too small a gap can cause mechanical damage.

Usually, the individual shroud segments are loosely supported with a corresponding clearance on the housing, wherein the game in the axial and circumferential direction is dimensioned so that it plays no role in terms of running clearance control at a temperature-induced expansion of the shroud segments. This ensures that the radial bearing in the housing and thus the radial gap to the rotor blade is largely independent of the temperature of the shroud segments.

In order to control the gap between the tip of the rotor blade and the respective shroud segment, different solutions have been proposed. For example, US 4,657,479 shows a mechanical solution with an active system in which the relative position of the shroud segment to the outer housing is changeable. The control takes place by means of a number of bolts, which are arranged between the shroud segments. The bolts are rotated by a control mechanism, forming the shroud segments separate each other. This increases the entire circumferential length of the shroud formed from the individual shroud segments, so that there is a radial movement to the outside relative to the housing. As a result, the gap is increased to the rotor blade tip. A movement in the reverse direction is made by means of spring elements.

This mechanism proves to be very expensive and prone to failure in terms of its structure, its manufacturing costs and its operation. Another disadvantage is that an external control system is needed.

From DE 14 26 857 A1 a gap seal is known in which individual shroud segments engage in one another by means of a labyrinth-like construction on their peripheral sides. As a result, a relatively large space for movement of the shroud segments is created so that they can move in thermal contraction or expansion, without jamming.

DE 38 18 882 C2 describes a gas turbine engine with shroud segments, which are formed chamfered in order to compensate for thermal contraction or expansion in this way.

Another construction is shown in EP 0 381 895 A1. Here, the shroud is mounted with a radial gap, so that it can move in the radial direction and expand or contract under thermal influences.

US 2 634 090 A describes a turbine shroud segment design in which the stator blades are stationary Are associated with rings, which have a distance in the axial direction, which is bridged by shroud segments. These are elastically mounted on their radially outer side and are pressed in the operating state by the gas pressure occurring radially inwardly against the stationary rings and applied against them.

The invention has for its object to provide a Turbinendeckbandsegmentbefestigung, which with a simple structure and simple operation, a reliable control the gap allows, even in extreme operating conditions.

According to the invention the object is achieved by the feature combination of the main claim, the subclaims show further advantageous embodiments of the invention.

According to the invention it is thus provided that the individual shroud segments are mounted with a game in the circumferential direction in the housing, that the game is reduced to zero for a given temperature difference between the housing and the shroud segments and that the shroud segments supported by means of an elastically deformable mounting to the housing are.

The turbine shroud segment attachment according to the invention is characterized by a number of significant advantages.

According to the invention, the shroud segments are arranged such that the radial movement of the shroud segments takes place to match an expansion of the rotor blades in order to be able to control the play on the rotor blade tips in this way.

Particularly advantageous, the present invention proves to be very large temperature differences between the housing (cold housing) and the rotor (high temperature of the rotor disks) are present. While in normal operation, the shroud segments, due to the existing game, are stored so that they can thermally expand and contract accordingly takes place at the described large temperature difference by overcoming the game defined by the invention clamping the individual shroud segments relative to the housing. Thus, the individual shroud segments are jammed into a single ring, which is behaves like a single component in terms of its degree of expansion and thermal expansion behavior. By means of the inventively provided elastically deformable storage, the thus clamped shroud segments can continue to thermally expand accordingly, while overcoming the game, the originally present large temperature difference is taken into account. This is then namely a faster closing of the game to avoid touching the tips of the rotor blades.

According to the invention it is favorable that the play of the shroud segments is formed in the circumferential direction and in the axial direction in the region of the bearing of the shroud segments. In a game in the circumferential direction, the individual shroud segments close by thermal expansion into a single, continuous ring, which behaves like a single component in the further thermal expansion. Such a continuous ring of the shroud segment elements behaves according to its radial change in diameter according to the thermal expansion behavior of the housing. In a game in the axial direction, the individual shroud segments are each jammed individually against the housing. Again, they form a unit with the housing and can expand or contract on further heating to match the thermal response of the housing; the kinematics acting here is achieved by suitable design of the flexible suspension.

The result is an improved, fully automatic control of the game at the tips of the rotor blades. External controls can be dispensed with altogether.

In axial clamping, the invention provided "soft" storage of the individual shroud segments in a preferred manner by bearing elements, which are formed in a substantially T-shaped. The bearing elements thus have in cross-section lateral arms with a defined inclination and rigidity, with which they are supported against the housing or by means of which they are held on the housing. Due to the elastic deformability of these arms, associated with a corresponding bearing on the housing, the mobility of the shroud segments is possible relative to the housing and in clamping the intended radial movement is effected.

According to the invention the shroud segments are thus relatively freely movable in the cold state, due to the present game, while they are clamped above a defined temperature difference, due to their thermal expansion, with the housing.

Fig. 1

eine schematische Darstellung der Zuordnung einer Rotorschaufel zu einem Deckbandsegment im Gehäuse einer Turbinenstufe,

Fig. 2

eine vergrößerte Detailansicht eines ersten Ausführungsbeispiels der Erfindung mit einer elastisch verformbaren Lagerung,

Fig. 3

eine Ansicht, analog Fig. 2, in einem zweiten Temperatur-Zustand,

Fig. 4

eine axiale Teil-Ansicht einer erfindungsgemäßen Ausgestaltung im stationären Betriebszustand,

Fig. 5

eine Ansicht analog Fig. 4 in einem Übergangs-Betriebszustand, und

Fig. 6

eine Ansicht mit axialem Spiel.

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

Fig. 1

a schematic representation of the assignment of a rotor blade to a shroud segment in the housing of a turbine stage,

Fig. 2

an enlarged detail view of a first embodiment of the invention with an elastically deformable storage,

Fig. 3

a view, analogous to FIG. 2, in a second temperature state,

Fig. 4

an axial partial view of a configuration according to the invention in the stationary operating state,

Fig. 5

a view similar to FIG. 4 in a transitional operating state, and

Fig. 6

a view with axial play.

Fig. 1 shows a portion of a turbine stage with a rotor blade 5, which is fixed to a disc. The tip 6 of the rotor blade is guided over a gap along a plurality of shroud segments 2, which, as can be seen for example from FIG. 4, form a ring. The shroud segments 2 are mounted on a housing 1 in a manner to be described.

2 shows the embodiment of bearing elements 4 for mounting the shroud segments 2 on the housing 1. In one embodiment, the bearing arms 7 are formed substantially elastically deformable. These are held by lugs 8 in grooves 9 of the housing 1. This arrangement allows movement of the shroud segments 2 radially outward.

FIG. 6 shows how the play is formed in the axial direction as an axial gap 12 between the shroud segment 2 and the housing 1. Here, too, heating of the shroud segments 2 after appropriate thermal expansion leads to jamming in the housing 1.

The dashed lines the mobility of the shroud segments 2 is shown at further thermal stress radially outward. By the "soft" storage means The bearing elements 4, the shroud segments can move radially outwardly accordingly to respond to heating of the rotor blades 5 to maintain the corresponding tip game.

4 and 5 show two views in a sectional view perpendicular to the central axis 10 of the gas turbine. In particular, the individual shroud segments 2 are clearly visible, as well as their elastic bearing elements 4. FIG. 4 shows a stationary operating state in which a clearance 3 is present in the circumferential direction between the individual shroud segments. The housing 1 has a predetermined rigidity, the same applies to the bearing elements 4. The shroud segments 2 are provided with a predetermined strength or rigidity. Both the housing 1 and the shroud segments 2 each have a predetermined thermal expansion or contraction behavior, through which the gap 3 (clearance) results.

FIG. 5 shows a transitional operating state in which a radial gap 11 between the tips 6 of the rotor blades 5 is greater than, for example, in the stationary operating state shown in FIG. 4. Due to the thermal expansion of the shroud segments 2 whose distance is closed in the circumferential direction, so that there is no more play. The shroud segments 2 thus form a solid, self-contained ring. A further thermal expansion leads to a radial displacement of this ring, which is possible by the elasticity of the bearing elements 4.

2 and 3 show an embodiment for carrying out the game of the invention 3. The Fig. 2 corresponds to the state of FIG. 4. This results in a distance a between the shroud segments 2 and the housing 1. It is a temperature state in which the following equation holds: $${\mathrm{T}}_{\mathrm{Deckbandsement}}\mathrm{-}{\mathrm{T}}_{\mathrm{casing}}\mathrm{\le }{\mathrm{\Delta T}}_{\mathrm{critical}}$$

FIG. 3 shows an operating state corresponding to FIG. 5. In this case, the shroud segments are each against each other. This results in a gap b between the shroud segments 2 and the housing 1, which is smaller than the gap shown in Fig. 2 a. In Fig. 3, there is a thermal state which can be expressed as follows: $${\mathrm{T}}_{\mathrm{Deckbandsement}}\mathrm{-}{\mathrm{T}}_{\mathrm{casing}}>{\mathrm{\Delta T}}_{\mathrm{critical}}$$

According to the invention it is thus possible to automatically influence the gap between the tips 6 of the rotor blades 5 and the shroud segments 2 in the desired manner, without additional external measures being necessary. The invention is thus based on the operating principle that the shroud segments thermally expand or contract more or less at the same time and with the same rate of expansion as the rotor blades. Due to the thermal expansion, the shroud segments are temporarily raised in the radial direction, so that contact with the tips 6 of the rotor blades 5 is avoided (see, for example, FIG. 5). This temporary lifting of the shroud segments 2 is carried out by appropriate dimensioning of the gap or. Game 3, so that this closes at a given thermal situation.

The width of the game 3 thus changes with the temperature difference between the shroud segment 2 and the housing 1 or the bearing ring or bearing area on which the shroud segments 2 are mounted. During the critical transient operating state Thus, the shroud segments jam in the circumferential direction and form a closed ring, which then changes in diameter upon further thermal expansion.

It is understood that, according to the invention, further free spaces or a further clearance 12, for example in the axial direction, may also be present in order to influence the thermal expansion behavior of the shroud segments in further operating states. Furthermore, the individual columns or games can be dimensioned differently in order to realize a different behavior of the individual components. The gaps can thus also have a different orientation, wherein at least one component is present in the circumferential direction and axial direction in order to ensure the jamming of the shroud segments. This means that the game must be present either in the circumferential direction and in the axial direction. It follows that the width of a radial gap 11 between the shroud segments 2 and the tips 6 of rotor blades 5 by the game 3 and / or the elasticity of bearing elements 4, which store the shroud segments 2 on the housing 1 is set.

The invention is not limited to the embodiments shown, but rather arise within the scope of the invention varied modification and modification options.

LIST OF REFERENCE NUMBERS

1

casing

2

Shroud segment

3

Game in the circumferential direction

4

bearing element

5

rotor blade

6

top

7

poor

8th

approach

9

groove

10

central axis

11

radial gap

12

Game in the axial direction

Claims (4)

1. Turbine shroud segment attachment with a casing (1) and several shroud segments (2) arranged in the casing (1), with the shroud segments (2) being retained on the casing (1) by way of an elastically deformable locating arrangement, and with the individual shroud segments (2) being located in the casing (1) with a circumferential clearance (3) between the individual shroud segments (2), characterized in that the clearance (3) is reduced to zero at a given temperature difference between the casing (1) and the shroud segments (2), and in that the locating arrangement consists of locating elements (4) of essentially T-shaped cross-section with specifically inclined and shaped sideward arms.
2. Turbine shroud segment attachment in accordance with Claim 1, characterized in that an axial clearance (12) is provided in the area of location of the shroud segment elements (2).
3. Turbine shroud segment attachment in accordance with Claim 1 or 2, characterized in that the locating elements (4) form one integral part with the shroud segments (2).
4. Turbine shroud segment attachment in accordance with one of the Claims 1 to 3, characterized in that the width of a radial gap (11) between the shroud segments (2) and the tips (6) of the rotor blades (5) is set by the clearance (3) and/or the elasticity of locating elements (4) which retain the shroud segments (2) on the casing (1).

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