Guide blade arrangement for an axial turbo-machine

A guide blade arrangement for an axial turbo-machine is provided. The guide blade arrangement includes at least one annular guide blade carrier and an inner ring arranged concentrically with respect to the guide blade carrier, between which guide blade carrier and inner ring a number of guide blades are arranged in a radial configuration. To obtain a low-wear and particularly durable fastening of the guide blade, which is supported by the guide blade carrier, to the inner ring, it is proposed that the guide blades are fastened resiliently to the inner ring. Here, the fastening is provided by means of a spring element. By means of the spring element, it is possible to ensure a uniform contact pressure of the guide blade head against the inner ring or if appropriate against a further spring element, such that occurring stresses and wear can be reduced.

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Description
CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2009/064427, filed Nov. 2, 2009 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 08021215.2 EP filed Dec. 5, 2008. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention refers to a stator blade arrangement for an axial turbomachine, comprising an annular stator blade carrier and an inner ring which is arranged concentrically to the stator blade carrier, between which a number of stator blades, with a blade airfoil, are arranged in a radial configuration, wherein each stator blade is fastened on the stator blade carrier.

BACKGROUND OF INVENTION

A stator blade arrangement which is referred to in the introduction is sufficiently known from the prior art. This is known for example in the case of compressors of stationary gas turbines, in which stator blades of the compressor are fastened on a stator blade carrier or on a compressor casing. For this purpose, known stator blade carriers, which in particular are mostly formed with a tubular shape, have retaining slots with undercuts which extend on their inner generated surfaces in the circumferential direction and in which stator blades or outer rings are inserted and fastened. The stator blades in this case on the one hand can be formed as free-standing stator blades so that their blade airfoil tips lie opposite an inner boundary wall of the flow path of the compressor, forming a gap. It is also known, for example from US 20007/0177973 A1, that the inner boundary wall of the flow path is part of the stator blades or can be retained by the stator blades themselves. In this case, the known stator blades either have shrouds which are arranged in each case on the tip side, which then form parts of the boundary wall, or the stator blades carry an inner ring on the tip side, the outer generated surface of which then constitutes the inner boundary for the flow path. The fastening of the inner ring on the stator blades of the stator blade arrangement in this case can be carried out via a suitable bolted connection, by means of welding, or else by means of caulking.

In the case of the known types of fastening of the inner ring on the stator blades of the stator blade arrangement, wear or crack emergence on the connection of inner ring and stator blade can occur during operation of the compressor. The wear phenomena occur due to rotation of the inner ring as a result of the aerodynamic blade load and/or due to thermally induced expansions which occur as a result of the heat which is generated during compression in the compressor. Periodic blade load changes or vibrations can also lead to wear phenomena.

In addition, a radially inner sprung fastening of the blade airfoils is known from publications GB 2 400 415 A and U.S. Pat. No. 2,914,300.

The object of the invention is consequently the provision of a stator blade arrangement, which is referred to in the introduction, for an axial turbomachine, which enables a particularly simple, expansion-tolerant, low-wear and reliable fastening of stator blades on an inner ring.

SUMMARY OF INVENTION

The object which forms the basis of the invention is achieved by means of a stator blade arrangement according to the features of the claims.

According to the invention, it is provided that in the case of the stator blade arrangement which is referred to in the introduction the stator blade comprises a stator blade tip with a web and with a tip section which extends transversely to it, the stator blade tip projecting into an encompassing slot of the inner ring, and the slot is closed off in each case by a shroud in the section between two adjacent stator blades, that adjacent shrouds are at a distance from each other, forming recesses which accommodate the webs, and that the stator blade tip of at least one of the stator blades is spring-fastened on the inner ring by means of at least one spring element which is arranged in a side face of the recess which faces the web in question.

The invention is based on the knowledge that a rigid connection of stator blades on the inner ring is disadvantageous. It accordingly proposes a type of connection which to a small extent enables relative movements of stator blades to the inner ring in a wear-free manner, without damage to the connection. Consequently, the invention departs from the previous procedures in which a rigid, fixed connection between stator blades and inner ring was provided.

In the course of the invention, a simple spring element is now to be used for fixing the stator blade on the inner ring. By using a spring fastening of stator blades on the inner ring a uniform pressing of the stator blade in question on the inner ring can be carried out, which efficiently minimizes occurring stresses which are created as a result of thermal expansions and/or static and/or dynamic stresses. At the same time, as a result of the spring-fastening the installation tolerances, which are necessary for a simple installation, can be especially simply compensated.

By reducing wear and avoiding cracks, an increase of the plant availability can be altogether enabled since checks and reworking of worn components, which have been necessary up to now, are discontinued when applying the invention. Furthermore, repair costs can be saved and intermediate inspections can possibly be dispensed with. Moreover, the described measure can easily be combined with some of the known solutions from the prior art, which represents an improved repair possibility of existing turbomachines.

Each stator blade in question, on the inner ring side, comprises a stator blade tip, which is recessed in the inner ring, i.e. projects into a slot which is provided for it, and by means of which the stator blade is spring-fastened on the inner ring. So that the stator blade in question can be spring-fastened on the inner ring, it comprises at least one construction element, namely the stator blade tip, which can be connected to the inner ring and is suitable for carrying this.

According to a simple development, the stator blade tip of each stator blade in question comprises a web which is arranged in each case in an outwardly open recess which is arranged on the inner ring and in which a spring element is arranged in at least one of the side faces of the recess which faces the web in question, and which spring element abuts in a pretensioned manner against the inner ring and against the web of the stator blade in question. Therefore, for spring-fastening of the stator blade on the inner ring provision is made for a further constructional component, that is to say the spring element, which on one side is supported on the inner ring and on the other side is supported on the web of the stator blade in question. In this case, the stator blade arrangement is designed so that the spring element is preferably pretensioned and therefore presses the web of the stator blade in question either indirectly or directly onto the inner ring, in detail onto one of the two side faces of the recess.

The stator blade tip is formed in the shape of an inverted T by means of the web and a tip section which extends transversely to it, wherein the web connects the tip section to an aerodynamically curved blade airfoil of the stator blade in question, and wherein the inner ring has an encompassing slot, which is fanned corresponding to the stator blade tip, for accommodating the stator blade tips, which slot is closed off in each case by a shroud in the section between two adjacent stator blades, that is to say towards the blade airfoil. As a result of the faun-fitting connection of the stator blade to the inner ring by means of the inverted T-shaped stator blade tip or stator blade hook which is arranged on the stator blade, and a slot which is provided on the inner ring and which is formed corresponding to the shape of the stator blade tip, a stator blade arrangement can be disclosed in which the inner ring is especially reliably carried by the stator blades. This development is especially advantageous when the stator blade arrangement itself, the inner ring and/or the annular stator blade carrier, is not formed in one piece in each case but are faulted by means of at least two arc-shaped ring segments which during installation and/or removal are separated in each case from the other ring segments in a manageable manner. The shroud on the one hand prevents displacement of the inner ring in relation to the stator blades along the circumference since the shroud is arranged in each case between two stator blades and therefore blocks the displacement path along the slot. On the other hand, the shroud also ensures a stepless boundary surface of the flow passage. Altogether, the components of the arrangement and the arrangement itself can then be easily produced.

Advantageous developments are disclosed in the dependent claims.

According to an advantageous development, two spring elements, which are arranged on side faces of the recess which lie opposite each other, are provided for each stator blade in question. As a result of this, each stator blade which is mounted in such a way indirectly, that is to say via the spring elements, is arranged on the inner ring in a pretensioned state. The spring force of each spring element in this case is expediently oriented in the circumferential direction of the inner ring. If a tension sleeve is used as a spring element, there is only a linear contact between the web of each stator blade in question and the tension sleeve, as a result of which the static loading of the stator blade on the connecting point is lower than in the case of a two-dimensionally fixed stator blade. Since the static loading is carried out primarily as a result of an occurring displacement of the inner ring in the circumferential direction caused by an aerodynamic blade loading, a displacement-tolerant fastening in the form of a spring-mounting in the circumferential direction is necessary in order to avoid wear and crack emergence and crack propagation.

It can be of advantage to a simple production of the stator blade arrangement if the inner ring comprises two ring sections which can be installed after their assembly to form a one-piece inner ring.

If the stator blade arrangement is used especially in stationary turbomachines, it is advantageous if the stator blade arrangement itself comprises two or more ring segments, that is to say that the inner ring and/or the annular stator blade carrier are formed as arc-shaped ring segments. Since the stator blade arrangement and its components are part of the rotationally fixed component parts of a turbomachine, which, if used in the stationary region, have a parting plane, as a result of which the rotationally fixed component parts are split for an upper and a lower half, a stator blade arrangement which is split into two ring segments, each of 180°, is particularly suitable for stationary turbomachines. A simple installation of the individual components, forming an altogether annular stator blade arrangement, is then possible. The stator blade arrangement is preferably used in a turbomachine which can be formed especially as an axial compressor or axial turbine. Moreover, the stator blade carrier can be arranged inside a separate casing or even itself can be formed as a casing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained with reference to a drawing. Further advantages and further features result in this case from the figure description.

In the drawing:

FIG. 1 shows a segment 10 of a stator blade arrangement 12 of an axial turbomachine in a perspective view;

FIG. 2 shows an exploded view of FIG. 1;

FIG. 3 shows a longitudinal section through a connection according to the invention of stator blade and inner ring;

FIG. 4 shows a detail of the inner ring without stator blade;

FIG. 5 shows a side view according to the section V-V, and

FIGS. 6, 7 schematically show the twist of the stator blade as a result of load reaction and support reaction for a stator blade which is fastened according to the prior art and for a stator blade which is fastened according to the invention.

 DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a segment 10 of a stator blade arrangement 12 of an axial turbomachine in a perspective view. The segment 10 is formed in the shape of an arc and spans an arc of 180°. Two of the segments 10 which are shown in FIG. 1 can be assembled to form a stator blade arrangement 12 according to the invention, which is then formed in an annular configuration. Slots 18 which extend in the axial direction and are for accommodating stator blades 20 are provided on an inner face 16 of the stator blade carrier 14. In FIG. 2, the stator blades 20 which are to be inserted in the slots 18 are shown displaced to the stator blade carrier 14 on account of the exploded type of view. The radially outer part of the stator blade 20 in this case is referred to as a stator blade root in each case and the radially inner part of the stator blade 20 is referred to as a stator blade tip. Between stator blade root and stator blade tip the stator blade 20 has an aerodynamically curved blade airfoil. An inner ring 22, of which only a 180° segment is shown in FIG. 2, is arranged on the stator blades 20 on the tip side. The inner ring 22 or its segments are assembled in this case from two ring sections 36, 38 or ring section segments.

The stator blade arrangement 12 which is to be assembled from two segments 10 therefore comprises a ring of stator blades 20 which is also known as a stator blade ring and can be part of a compressor stage or turbine stage.

The stator blade carrier 14 is fastened on a casing, which is not additionally shown, of the axial turbomachine, for example of a compressor, or itself is formed as a casing. The stator blade carrier 14 carries the stator blades 20 which are fastened on it on the inside and which in their turn carry the inner ring 22 inside on the tip side. The outer generated surface of the inner ring 22 and the inner surface 16 of the stator blade carrier 14 in this case form the radial inner and outer boundary for a medium which flows through the axial turbomachine. If the axial turbomachine is formed as a compressor, the medium is compressed air, or air which is to be compressed.

FIG. 3 shows a longitudinal section (in the sense of the axial turbomachine) through a connection according to the invention of the stator blade 20 to the inner ring 22. The blade airfoil 28 which is part of the stator blade 20 is only partially shown. A stator blade tip 30, which has a web 32 and also a tip section 34 which extends transversely to it, is provided on the blade airfoil 28 on the tip-side section of the stator blade 20. By means of the web 32 and the tip section 34, the stator blade tip 30 altogether has an inverted T-shape, as seen in cross section.

The inner ring 22 is provided with an outwardly open slot 44, the longitudinal sectional contour of which is formed corresponding to the stator blade tip 30. The inner ring 22 comprises the two ring sections 36, 38 which in their turn according to FIG. 2 are also formed as 180° arc-shaped segments. The ring sections 36, 38 or their segments are interconnected in a fixed manner via a weld joint 40. The ring sections 36, 38 have in each case projections 42, 43 which are oriented towards each other, in each case for forming an undercut by means of which the inverted T-shaped stator blade tip 30 can be radially fixed.

FIG. 4 shows a perspective view of a section of the inner ring 22, in which the ring sections 36, 38 for reasons of clarity are not shown in their final constructional position but apart. In their final constructional position the two projections 42, 43, as far as possible, abut against each other without a gap. In the projection 43 of the ring section 36, a recess 46, of which two are shown in FIG. 4, is provided for each stator blade 20. The recesses 46 serve for accommodating the web 32 of the stator blade tip 30 of the stator blade 20. The projection 43 therefore forms a shroud 47 between the recesses which closes off the slot 44 between two stator blades 20 in order to provide a misalignment-free flow path. Between two adjacent shrouds 47, therefore, a recess 46 is provided in each case in which the web 32 is accommodated (FIG. 3). For overview reasons, the stator blade 20 which is shown in FIG. 3 is not shown in FIG. 4. Each recess 46 has two side faces 48 which lie opposite each other. In at least one of the two side faces 48 of each recess 46 a further pocket 50 is provided in which a spring element 52, which is formed as a tension ring, is provided for spring-fastening of the stator blade 20 on the inner ring 22. In FIG. 4, a spring element 52 is schematically shown only in the recess 46 which is shown there further to the left. FIG. 5 shows a side view of the portion of the ring section 36 which in FIG. 4 is shown further to the right. This recess 46 is delimited by two side faces 48 in which a pocket 50 is provided in each case. The pocket 50 is formed essentially in the shape of a circle segment and extends over the entire axial length of the recess 46. The pocket 50 in this case for example may have been produced by drilling or eroding before introducing the recess 46. The pocket 50 in this case is arranged so that the diameter of the pocket 50, which lies in the radial plane of the axial turbomachine, is arranged in the projection 43 or in the shroud 47 so that only a comparatively small section of the hole circle is covered by the recess 46. The tension sleeve then has a diameter which is only slightly smaller than the diameter of the pocket 50. As a result of the selected position of the pocket 50, the spring element 52 which is formed as a tension sleeve can still project by such a distance into the recess 46 that the web 32 located there, which is not shown in FIG. 5, is seated with spring effect on the inner ring 22 via the spring element 52. On account of the selected arrangement of the recess 46, the pockets 50 and the spring elements 52, the force direction of the last-mentioned acts in the circumferential direction.

Falling out of the spring element 52 from the pocket 50 into the recess 46 can be avoided on account of the position of the pocket 50. This facilitates the assembly of the stator blade arrangement 12.

Naturally, the spring element 52 could also be mounted in pockets which are arranged on the web 32 and not on the side faces 48 of the recess 46.

FIG. 6 and FIG. 7 schematically show the twist of the stator blade 20 as a result of load reaction and support reaction for a stator blade which is fastened according to the prior art (FIG. 6) and for a stator blade which is fastened according to the invention (FIG. 7).

Since a stator blade 20 which is fastened on the tip side according to the prior art is twisted to a particularly high degree, high loads and wear, which depending upon load can lead to crack emergence and crack propagation, could especially occur at their weakest point, namely on the stator blade tip 32 or else on the inner ring. With the invention, a spring-fastening of the stator blade tip 30, and therefore a fastening which is to be referred to as a flexible bearing, is now proposed which leads to significantly lower twist of the stator blade 20 as a result of load reaction and support reaction. As a result of this, the loading on the stator blade tip 32 can be reduced which delays or prevents the emergence of cracks and wear. In particular, the displacement of the inner ring in the circumferential direction which occurs as a result of aerodynamic blade loading creates a static loading of the blade which can be better compensated by means of the connection according to the invention than stator blades which are fastened according to the prior art.

In total, the invention refers to a stator blade arrangement 12 for an axial turbomachine and comprises at least one annular stator blade carrier 14 and an inner ring 22 which is arranged concentrically to the stator blade carrier 14, between which a number of stator blades 20 are arranged in a radial configuration. In order to disclose a low-wear and particularly durable fastening of the stator blade 20, which is carried by the stator blade carrier 14, on the inner ring 22, it is proposed that the stator blades 20 be spring-fastened on the inner ring 22. The fastening is carried out in this case by means of a spring element 52. By means of the spring element 52, a uniform pressing of the stator blade tip 30 onto the inner ring 22, or possibly onto a further spring element 52, can be ensured so that stresses and also wear which occur can be reduced.

Claims

1.-11. (canceled)

12. A stator blade arrangement for an axial turbomachine, comprising:

an annular stator blade carrier;
an inner ring which is arranged concentrically to the stator blade carrier; and
a plurality of stator blades arranged between the annular stator blade carrier and the inner ring and arranged in a radial configuration,
wherein each stator blade comprises a blade airfoil and is fastened on the stator blade carrier,
wherein each stator blade comprises a stator blade tip, with a web and with a tip section which extends transversely to the web, and which projects into an encompassing slot of the inner ring, and the slot is closed off in each case by a shroud in a section between two adjacent stator blades,
wherein adjacent shrouds are at a distance from each other, forming a plurality of recesses which accommodate the plurality of webs, and
wherein the stator blade tip of at least one of the stator blades is spring-fastened on the inner ring by means of a spring element which is arranged in a side face of a respective recess which faces the web.

13. The stator blade arrangement as claimed in claim 12, wherein the spring element abuts in a pretensioned manner against the inner ring and against the web of the respective stator blade.

14. The stator blade arrangement as claimed in claim 12, wherein two spring elements, which are arranged on side faces of the recess which lie opposite each other, are provided for each stator blade.

15. The stator blade arrangement as claimed in claim 12, wherein the spring element is formed as a tension sleeve.

16. The stator blade arrangement as claimed in claim 12, wherein a pocket for accommodating the spring element, from which the spring element partially projects, is provided in the respective side faces.

17. The stator blade arrangement as claimed in claim 12, wherein a spring force is oriented in a circumferential direction of the inner ring.

18. The stator blade arrangement as claimed in claim 12, wherein the inner ring comprises two ring sections.

19. The stator blade arrangement as claimed in claim 12, wherein the inner ring and the annular stator blade carrier comprises at least two ring segments.

20. The stator blade arrangement as claimed in claim 12, wherein the inner ring or the annular stator blade carrier comprises at least two ring segments.

21. The stator blade arrangement as claimed in claim 12, wherein the stator blade carrier is formed as a casing.

22. A turbomachine, comprising:

a stator blade arrangement, comprising: an annular stator blade carrier, an inner ring which is arranged concentrically to the stator blade carrier, and a plurality of stator blades arranged between the annular stator blade carrier and the inner ring and arranged in a radial configuration,
wherein each stator blade comprises a blade airfoil and is fastened on the stator blade carrier,
wherein each stator blade comprises a stator blade tip, with a web and with a tip section which extends transversely to the web, and which projects into an encompassing slot of the inner ring, and the slot is closed off in each case by a shroud in a section between two adjacent stator blades,
wherein adjacent shrouds are at a distance from each other, forming a plurality of recesses which accommodate the plurality of webs, and
wherein the stator blade tip of at least one of the stator blades is spring-fastened on the inner ring by means of a spring element which is arranged in a side face of a respective recess which faces the web.

23. The turbomachine as claimed in claim 22, wherein the turbomachine is formed as an axial compressor or an axial turbine.

24. The turbomachine as claimed in claim 22, wherein the spring element abuts in a pretensioned manner against the inner ring and against the web of the respective stator blade.

25. The turbomachine as claimed in claim 22, wherein two spring elements, which are arranged on side faces of the recess which lie opposite each other, are provided for each stator blade.

26. The turbomachine as claimed in claim 22, wherein the spring element is formed as a tension sleeve.

27. The turbomachine as claimed in claim 22, wherein a pocket for accommodating the spring element, from which the spring element partially projects, is provided in the respective side faces.

28. The turbomachine as claimed in claim 22, wherein a spring force is oriented in a circumferential direction of the inner ring.

29. The turbomachine as claimed in claim 22, wherein the inner ring comprises two ring sections.

30. The turbomachine as claimed in claim 22, wherein the inner ring and/or the annular stator blade carrier comprises at least two ring segments.

31. The turbomachine as claimed in claim 22, wherein the stator blade carrier is formed as a casing.

Patent History
Publication number: 20110286851
Type: Application
Filed: Nov 2, 2009
Publication Date: Nov 24, 2011
Inventors: Francois Benkler (Ratingen), Raoul Costamagna (Mulheim an der Ruhr), Bernward Mertens (Leverkusen), Uwe Sieber (Mulheim an der Ruhr)
Application Number: 13/132,339
Classifications
Current U.S. Class: 416/223.0R
International Classification: F01D 5/14 (20060101);