EP2313615B2 - Blade arrangement of a gas turbine - Google Patents

Description

Technical area

The present invention relates to the field of thermal fluid machines, in particular gas turbines. It relates to a blade arrangement of a thermal fluid machine according to the preamble of claim 1.

State of the art

For the efficiency of a gas turbine, it is of great importance, especially in the turbine part in which the hot gases from the combustion chamber are expanded, to keep the gaps in the area of the blading that occur between the bladed rotating rotor and the surrounding stator as small as possible.

In the simplest case, like this Fig. 1 is shown based on the blade arrangement 10, no special measures are taken to optimize the gap width: The rotor blades 11, which protrude radially into the hot gas duct 13 of the gas turbine and rotate about the axis 16, end in a blade tip 27 provided with a first covering layer 15, which is provided with a Game 25 is opposite a heat shield 12 forming the outer wall 26 of the hot gas channel 13, which is provided with a second cover layer 14. The cover layers 14 and 15, which can consist of MCrAlY, for example, protect the components 11 and 12 from the harmful effects of the hot gases in the hot gas channel 13, in particular from undesirable oxidation. The blade arrangement 10 of the Fig. 1 is not designed for grinding the blade tips 27 into the heat shield 12. The game 25 between the blade tips 27 and the heat shield 12 takes into account the different thermal expansions and is therefore comparatively large in order to avoid grinding of the components during operation.

In order to be able to reduce the play 25, blade arrangements 20 are according to Fig. 2 been suggested (see e.g. the EP-A2-0 166 676 , EP-A2-1 312 760 or the US-A1-2008166225 ), in which abrasive bodies (grains) 21 (e.g. made of silicon carbide or cubic boron nitride cBN) are embedded in a carrier layer 19 on the blade tip 27 of the rotor blades, with which the blade tip 27 is in operation in a grindable thermal barrier coating 18 (Thermal Barrier Coating TBC ) can grind into the opposite heat shield 12. For example, a layer of metallic MCrAlY can be used as the carrier layer 19 for the grinding wheels 21, as well as as an adhesive layer 17 under the thermal insulation layer 18.

The abrasive layer 19, 21 of such a blade arrangement has a comparatively complex structure due to the embedded abrasive bodies and is therefore complex to produce.

document US-A1-5 883 314 discloses a method for producing abradable coatings on thermally stressed components of gas turbines, which are characterized by good abrasion properties and at the same time high binding effect to the substrate. Areas of application are stator parts of the hot gas channel or blade parts. Layer-like, flexible preforms based on modified MCrAIY alloys are applied to the areas of the turbine component in question, for example the blade tip, and metallurgically bonded to it. The production of the multilayer preforms is comparatively complex.

EP-A2-0 965 730 discloses suitable material combinations of interacting abrasive and abradable surfaces in gas turbines, in particular heat shield and blade tip, based on an abrasive blade tip and an abradable surface of the heat shield. The heat shield has an erosion-resistant surface made of a first ceramic material, which is firmly connected to the substrate by means of an adhesive layer. In a limited area, the contact area with the rotating blade tip, an abradable wear layer made of a second ceramic material is applied. The impacting blade tip is covered with an abrasive coating, preferably according to US-A-4,936,745 , i.e. equipped with grinding wheels made of silicon carbide or cubic boron nitride embedded in a metallic carrier layer. This solution is also characterized by elaborately finished surfaces of the components involved.

The publication US-A1-2003/175116 describes an abradable coating for stator components of a compressor or gas turbine. The blade tip and heat shield have means that enable the blade tip to be specifically ground into the heat shield. The outer layer of the heat shield itself has a porous thermal insulation layer with polygonal depressions (Fig. 6) or grooves running in the circumferential direction, delimited by wall projections (Fig. 7, 8), while the rotor blade tip has a circumferential cutting edge (Fig. 4, 5 ) is equipped to cut into the abradable coating of the heat shield. Equipping the blade tip with circumferential cutting edges increases the manufacturing effort and - at least when used in gas turbines - the effort for blade cooling in this area.

Presentation of the invention

The invention aims to provide a remedy here. It is therefore the object of the invention to provide a blade arrangement which avoids the disadvantages of known blade arrangements and, with a simple structure, produces a comparable grinding behavior without the need for a special abrasive layer on the blade tip must become.

The task is solved by the entirety of the features of claim 1. It is essential for the invention that the heat shield has a porous thermal insulation layer made of a porous ceramic layer as an outer, abradable layer, and that the blade tip is only provided with a homogeneous metallic cover layer made of MCrAIY. The porous thermal insulation layer enables the blade tip covered with the covering layer to grind into the heat shield even without a special grinding wheel or abrasive layer, thus optimally minimizing the play between the blade tip and the opposite heat shield.

Basically, the blade is a rotor blade or a guide blade of a thermal turbomachine, in particular a gas turbine, with a heat shield attached to the rotor opposite the blade tip in the case of a guide blade. According to a preferred embodiment, the blade is a blade rotating about the axis, while the heat shield is mounted in a stationary manner on the stator of the gas turbine.

Another embodiment of the invention is characterized in that the porous ceramic layer consists of YSZ. The porosity of the thermal insulation layer is preferably greater than 20%.

An adhesive layer, in particular made of MCrAIY, is advantageously arranged between the heat shield and the thermal insulation layer.

Another embodiment is characterized in that the rotor blade is part of the first row of rotor blades in the turbine part of the gas turbine.

Brief explanation of the characters

Fig. 1

in einer stark vereinfachten Darstellung eine frühere Schaufelanordnung ohne die Möglichkeit des Einschleifens;

Fig. 2

in einer zu Fig. 1 vergleichbaren Darstellung eine andere frühere Schaufelanordnung mit einer speziellen Schleifschicht auf der Schaufelspitze und

Fig. 3

in einer zu Fig. 1 vergleichbaren Darstellung eine für das Einschleifen vorgesehen Schaufelanordnung mit einer einfachen Abdeckschicht auf der Schaufelspitze gemäss einem Ausführungsbeispiel der Erfindung.

The invention will be explained in more detail below using exemplary embodiments in connection with the drawing. Show it

Fig. 1

In a highly simplified representation, an earlier blade arrangement without the possibility of grinding in;

Fig. 2

in one too Fig. 1 Comparable representation shows another earlier blade arrangement with a special abrasive layer on the blade tip and

Fig. 3

in one too Fig. 1 Comparable illustration of a blade arrangement intended for grinding with a simple covering layer on the blade tip according to an exemplary embodiment of the invention.

Ways of carrying out the invention

In Fig. 3 a preferred exemplary embodiment of a blade arrangement 30 according to the invention is shown. In the example, a rotor blade 11 with the blade tip 27, which can be rotated about the axis 16 of the gas turbine, is again opposed by a heat shield 12 with play 25. The clearance 25 and thus the efficiency of the turbine are optimized by grinding the blade tip 27 into the coating 22, 23 of the heat shield 12 (in Fig. 3 the possible grinding area 28 on the heat shield is indicated by a dashed line).

A thermal insulation layer 23 is provided on the heat shield 12 as the layer to be abraded during grinding, which is connected to the substrate of the heat shield 12 via an adhesive layer 22 located therebetween. A metallic oxidation protection layer made of MCrAlY can be provided in the usual way as the adhesive layer 22.

Experiments have now shown that grinding the blade tip into the thermal insulation layer 23 is possible even without a special abrasive layer on the blade tip 27 and leads to good results if the thermal insulation layer 23 is sufficiently easy to sand - without losing its thermal properties. This can be achieved by using a porous thermal insulation layer 23 made of a porous ceramic layer, which can consist in particular of YSZ (yttrium oxide-stabilized zirconium oxide), the porosity being created, for example, by embedded polymers that are later baked out. It has proven to be advantageous if the porosity of the thermal insulation layer is greater than 20%, for example in the range of 22-24%.

With such a porous thermal insulation layer 23, the abrasion on the blade tip 27 during grinding is comparatively small compared to the depth of the grinding area 28, so that a special grinding layer on the blade tip 27 can be dispensed with. It is therefore sufficient if the blade tip 27 is covered with a homogeneous cover layer 24 (without abrasive media) made of MCrAlY, which is anyway provided as a protective layer against oxidation of the blade material.

In this way, no special precautions need to be taken for grinding on the blade 11, which significantly simplifies the production of the blade 11.

Reference symbol list

10.20.30

Blade arrangement (gas turbine)

11

blade

12

Heat shield

13

Hot gas channel

14,15,24

Cover layer

16

axis

17.22

Adhesive layer

18.23

Thermal insulation layer (TBC)

19

Backing layer

21

Abrasive body

25

Game

26

Wall (hot gas duct)

27

Shovel tip

28

Grinding area

Claims (6)

1. Blade arrangement (30) of a thermal flow machine with at least one blade (11) protruding in the radial direction into a channel (13), through which hot gas flows and which is arranged concentrically to an axis (16), and ending in a blade tip (27) which lies opposite, with a clearance (25), a heat shield (12) delimiting the channel (13), wherein the blade (11) and the heat shield (12) are movable relative to one another in the circumferential direction, and the blade tip (27) and the heat shield (12) are covered with layers (22, 23, 24) which allow the blade tip (27) to grind into the heat shield (12) in a targeted manner, and wherein the heat shield (12) has a porous heat-insulating layer (23) as an outer layer which can be ground away, characterized in that the porous heat-insulating layer (23) is a porous ceramic layer, and the blade tip (27) is provided merely with a homogeneous metallic cover layer (24) of MCrAlY.
2. Blade arrangement according to claim 1, characterized in that the thermal flow machine is a gas turbine, that the blade is a moving blade (11) rotating about the axis (16), and that the heat shield (2) is mounted stationarily on the stator of the gas turbine.
3. Blade arrangement according to claim 1 and/or, characterized in that the porous ceramic layer consists of YSZ (yttrium-oxide-stabilised zirconium oxide).
4. Blade arrangement according to claim 3, characterized in that the porosity of the heat-insulating layer (23) is more than 20%.
5. Blade arrangement according to claim 3 or 4, characterized in that an adhesion layer (22), in particular made of MCrAlY, is arranged between the heat shield (12) and the heat-insulating layer (23).
6. Blade arrangement according to claim 2, characterized in that the moving blade (11) is part of the first row of moving blades in the turbine part of the gas turbine,

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