EP2604797B1 - Rotor blade with a rib assembly with an abrasive coating - Google Patents

Description

The present invention relates to a rotor blade for a compressor or turbine stage of a gas turbine, with a radially outer rib arrangement arranged on a shroud of the rotor blade and having at least two ribs directed radially outwards. The present invention further relates to a turbomachine, in particular a gas turbine, with at least one such blade.

From the EP 1 550 741 A1 It is known to provide blades radially on the outside of the shroud with ribs in order to reduce a leakage gap to a surrounding, in particular honeycomb, sealing surface and thus to increase the efficiency of a gas turbine. The publication proposes to provide the ribs on the face with an abrasive coating that grinds into a sacrificial material on the sealing surface.

From the US 5,794,338 A a method of repairing damaged coatings on ends of turbine blades in turbomachinery used at high temperatures is known. From the JP 2005127276 are known blades with axially spaced ribs on the shroud, the ribs are set at an angle to the circumferential direction. From the EP 2 372 093 is known a blade with a rib-like cutting structure oriented in the direction of rotation with coated cutting edges.

The object of the present invention is to provide an improved turbomachine.

To solve this problem, a rotor blade with the features of claim 1 is proposed, which can be used in a compressor and / or turbine stage of a gas turbine. Claim 6 provides a turbomachine, in particular a gas turbine, with a rotor blade arrangement with such rotor blades under protection. Preferred developments are the subject of the dependent claims.

One aspect of the present invention is based on the idea of not providing a surface or not only a harder surface but (also) a larger surface by means of a rib coating.

For this purpose, a rotor blade has a radially outer rib arrangement arranged on a shroud of the rotor blade. The rib arrangement has at least two radially outwardly directed ribs. The ribs have at least on the two side surfaces a coating on. These coatings are connected to one another via their radially outer end faces of the respective ribs. The thickness of the coating increases, in relation to a cut transverse to the rib, radially outwards on the two radial side surfaces of the rib.

The rotor blade has a rib arrangement with a plurality of ribs arranged one behind the other in the axial direction. In the present case, the axial direction refers in particular to a coordinate direction that is aligned with an axis of rotation of the rotor blade or turbomachine, in particular a gas turbine, a direction that extends perpendicularly from the axis of rotation as a radial direction and a direction that is perpendicular to the axis of rotation as the circumferential direction and extends perpendicular to the radial direction, in particular in the direction of rotation of the rotor blade or turbomachine, in particular gas turbine.

A coating is arranged on at least two or more, in particular adjacent, and preferably on all the ribs of the rib arrangement. This is preferably made of metal, plastic and / or ceramic. In a preferred embodiment, the coating has a greater hardness than the rib itself. A hardness according to Vickers, Rockwell, Brinell or a similar test protocol is referred to in the present case as hardness.

In order to provide a larger surface area by means of this coating (s) and thus in particular to increase the sealing effect and thus the efficiency, several, preferably all, coatings of the rib arrangement each have an outer contour in a meridian section, which contour extends outward in the radial direction, ie expanded with increasing radial distance from the axis of rotation, axially or in the axial direction.

In the present case, a meridian section is understood to mean, in particular, a cross section which contains the axial direction and the radial direction. In a preferred embodiment, an outer contour can expand monotonically, in particular strictly monotonously, in the radial direction to the outside. In the present case, this is understood in particular to mean that a distance in the axial direction between the two outer flanks of the outer contour always remains at least essentially (monotonically) or even always increases (strictly monotonous) with increasing radial distance from the axis of rotation. Equally, however, outer contours are also included, the outer flanks of which approach each other in limited radial areas. General is therefore an outer contour that extends outward in the radial direction, in particular an outer contour with two mutually opposite outer flanks, the distance of which in the axial direction is smaller at a first, smaller distance from the axis of rotation than at a second, larger distance from the axis of rotation,

As a result of such an outer contour increasing radially outwards, the outer flank of the coating approaches an adjacent rib or coating as seen in the axial direction, so that an axial gap between the coating and the adjacent rib or coating is reduced. As a result, a larger surface is made available radially on the outside and leakage into the spaces between adjacent ribs is reduced.

In a preferred embodiment, a gap between mutually facing flanks of adjacent coatings on adjacent ribs of the rib arrangement corresponds at most to an axial width of a radially outer end face of one of the two adjacent ribs. In the present case, the axial width refers in particular to the distance between a front and rear edge in the axial direction of a radially outer end face of a rib. Due to the preferred limitation of the gap to the front axial width of a rib, the leakage in the space between adjacent ribs can be reduced to a level that is not critical for the efficiency.

In a preferred development, a gap between mutually facing flanks of adjacent coatings of adjacent ribs of the rib arrangement corresponds to at most 75% and preferably at most 50% of such an axial width. In general, smaller gaps between coatings are preferred, with a gap advantageously having a certain minimum dimension, which in particular can be at least 20% of an axial width of a radially outer end face of one of the two adjacent ribs, in order to prevent the coating from flaking off.

The ribs of the rib arrangement are inclined in the circumferential direction by an angle which is not equal to 0 ° and less than 10 ° in amount, in particular less than 5 ° and preferably less than 3 °.

In a preferred embodiment, two or more, in particular all, of the ribs of the rib arrangement have outer end faces in the radial direction which, at least essentially, lie at the same radial height. Starting from these end faces, the ribs extend inward in the radial direction at different depths, i.e. are of different heights in the radial direction. On the one hand, this enables the formation of small gaps between the ribs and, on the other hand, an adaptation to blades with varying radial heights.

Likewise, in the radial direction, outer end faces of two or more, in particular all, of the ribs of the rib arrangement can have a different radial height, in particular — at least essentially — lie on a virtual conical surface. Additionally or alternatively, two or more, in particular all, ribs of the rib arrangement can have different heights in the radial direction.

The rib arrangement is arranged on a cover band of the moving blade. In the present case, a shroud is understood to mean, in particular, a flange which extends in the axial and circumferential directions and, in a preferred development, bears in a form-fitting manner on shrouds in the circumferential direction of adjacent blades. In a preferred development, the cover band can be inclined in the axial direction in order to support the ribs of different heights explained above.

The coating can be carried out by means of a method for coating one or, preferably, in particular in time in parallel or in succession, a plurality of ribs of a radially outer rib arrangement of a rotor blade, which is particularly suitable for coating a rotor blade according to the aspect explained above.

A coating material can be sprayed onto the fin arrangement from at least two opposite spray directions, in particular plasma sprayed, flame sprayed, in particular high speed flame sprayed, detonation sprayed, cold gas sprayed, arc sprayed, and / or laser sprayed. In the present case, plasma spraying is understood in particular to mean that, for example in a plasma torch, an electric arc is generated between the anode (s) and cathode (s) by a voltage, and gas or gas mixture is passed through the electric arc and thereby ionized. The dissociation or subsequent ionization generates a highly heated, electrically conductive gas from positive ions and Electrons. Powdery coating material can be injected into this generated plasma jet, which is melted by the high plasma temperature. The plasma stream entrains the powder particles and hurls them onto the rotor blade to be coated. The plasma coating is preferably carried out in a normal atmosphere, inert atmosphere, in vacuum or under water.

By spraying in an injection direction inclined against the radial direction, in particular the outer contour that widens outward in the radial direction can be represented. Comparable to the wind loads of snow in comb layers, more coating material is applied to the outer edges of the rotor blade front side, the projection of the coating material jet on the flank of the rib resulting from the inclination of the spray direction. In addition, adjacent ribs or coatings can partially shade the coating material jet, so that with decreasing radial distance from the axis of rotation, less coating material is applied.

The spray directions can be inclined in opposite directions, but with the same amount, against the radial direction, preferably by an spray angle which is greater than 20 °, in particular greater than 40 °, and / or less than 70 °, in particular less than 50 °. The coating material can be sprayed on in succession or simultaneously from the two spray directions.

One or more coatings can be reworked, simultaneously or in succession, after the coating material has been sprayed on. In particular, a radially outer end face of the coatings can, for example, be ground, polished or reworked in some other way.

Fig. 1:

das Deckband einer Laufschaufel nach einer Ausführung der vorliegenden Erfindung in einer Draufsicht entgegen einer radialen Richtung;

Fig. 2:

einen vergrößerten Ausschnitt der Fig. 3 bzw. 4;

Fig. 3:

einen Meridianschnitt einer Gasturbinenstufe nach einer Ausführung der vorliegenden Erfindung; und

Fig. 4:

einen Meridianschnitt einer Gasturbinenstufe nach einer weiteren Ausführung der vorliegenden Erfindung.

Further advantages and features result from the subclaims and the exemplary embodiments. Here shows, partly schematically:

Fig. 1:

the cover band of a blade according to an embodiment of the present invention in a plan view against a radial direction;

Fig. 2:

an enlarged section of the Fig. 3 or 4;

Fig. 3:

a meridian section of a gas turbine stage according to an embodiment of the present invention; and

Fig. 4:

a meridian section of a gas turbine stage according to a further embodiment of the present invention.

Fig. 3 shows a meridian section of a gas turbine stage according to an embodiment of the present invention with a moving blade 5, on the inclined cover band 1 of which a rib arrangement with five ribs 2 arranged one behind the other in the axial direction is arranged. A honeycomb-like sealing surface 4 is arranged radially opposite the rib arrangement 2. In the otherwise identical execution of the Fig. 4 instead of the honeycomb-like sealing surface 4 'with one or two (dashed) counter rib (s) is provided.

Fig. 2 shows an enlarged detail of the shroud 1 with the rib arrangement. As can be seen in particular here, a coating 3 is arranged on the radially outer end faces of the ribs 2, which are at the same radial height, so that the ribs have different heights due to the oblique shroud 1.

This coating 3 is applied by sequential plasma spraying first in a first spray direction S ₁ , and then in an opposite or mirror-symmetrical second spray direction S ₂ , as in FIG Fig. 2 indicated by arrows, applied. The two spray directions are inclined by an angle β ₁ = -β ₂ = 45 ° against the radial direction R in which the ribs 2 extend.

This results in 2 coatings 3 on the ribs, which in the meridian section of the Fig. 2 have an outer contour that widens outward in the radial direction. In other words, grows with increasing radial distance from an axis of rotation of the gas turbine (from bottom to top in Fig. 2 ) the axial distance (horizontal in Fig. 2 ) between outer flanks 3.1 of the outer contour of a coating 3, the coating widens radially outward in the axial direction. Correspondingly, a gap s between the outer flanks of adjacent coatings is reduced and is only about 75% of the radially outside Axial width b of the radially outer end face of the wider of the two adjacent ribs 2 (left in Fig. 2 ).

Due to the opposing superposition of the two spray directions S ₁ , S ₂ , an essentially flat end face of the coatings 3 can be represented. The coating, in particular its radially outer end face (top in Fig. 2 ) post-processed, in particular ground, after spraying.

One recognizes in particular in the Fig. 2 that a largely, particularly fluidically, sealed sealing surface is made available by the coatings 3 widening in the radial direction outwards or with increasing radial distance from the axis of rotation, the weight of the rib arrangement advantageously remaining low due to the spaces between the ribs.

As in Fig. 1 recognizable, the ribs 2 are inclined against the circumferential direction U by an angle α, which is 2 ° in the exemplary embodiment. For clarification, the circumferential direction U and a radial direction R are indicated in the figures, wherein 2 to 4 one section horizontally to the plane of the drawing Fig. 1 can represent, so an axial direction in all figures runs horizontally from left to right. The spray layer is not shown.

LIST OF REFERENCE NUMBERS

1

shroud

2

Rib (nanordnung)

3

coating

3.1

Outer flank of the coating / coating outer contour

4; 4 '

sealing surface

5

blade

Claims (6)

1. Rotor blade (5) for a compressor stage or turbine stage of a gas turbine, comprising a radially outer rib arrangement which is arranged on a shroud (1) of the rotor blade (5) and has at least two radially outwardly directed ribs (2), wherein the ribs (2) are arranged one behind the other in the axial direction and are inclined in the circumferential direction (U) by an angle (α) not equal to 0° which is smaller than 10° in absolute value, wherein the ribs (2) have a coating (3) on the respective two axially opposite side surfaces and on the radially outer end face of the ribs (2), via which the side surfaces are connected, wherein the thickness of the coating (3) in a section transverse with respect to the rib (2) on the two radial side surfaces of the rib (2) increases with increasing radial distance from the axis of rotation of the gas turbine.
2. Rotor blade (5) according to claim 1, characterized in that a coating (3) is arranged in each case on at least two adjacent ribs (2), and a gap (s) between mutually facing flanks (3.1) of the adjacent coatings (3) corresponding at most to an axial width (b) of a radially outer end face of one of the two adjacent ribs (2).
3. Rotor blade (5) according to either of the preceding claims, characterized in that at least two ribs (2) of the rib arrangement have an end face which is outside in the radial direction (R) and which, at least substantially, is at the same radial height, and, starting from the end face, are inwardly different in height in the radial direction.
4. Rotor blade (5) according to any of claims 1 to 3, characterized in that at least two ribs (2) of the rib assembly have end faces which are outside in the radial direction (R) and are at different radial heights, the ribs (2) being different in height in the radial direction.
5. Rotor blade (5) according to any of the preceding claims, characterized in that a coating (3) has a greater hardness than the rib (2) on which it is arranged.
6. Turbomachine comprising a rotor blade assembly having at least one rotor blade (5) according to any of the preceding claims.

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