WO2003100220A1

WO2003100220A1 - Axial securing means for impeller blades

Info

Publication number: WO2003100220A1
Application number: PCT/CH2003/000289
Authority: WO
Inventors: Daniel KÄSTLI; Josef Bättig
Original assignee: Abb Turbo Systems Ag
Priority date: 2002-05-24
Filing date: 2003-05-06
Publication date: 2003-12-04
Also published as: EP1507958A1; CN1656303A; CN100335749C; KR20050004188A; AU2003226999A1

Abstract

The invention relates to axial securing means for impeller blades (10) of turbo generators with axial passage. In said generators the impeller blades (10) are secured radially and in a peripheral direction by means of a blade root (12) that is axially inserted into a radial groove (14) of a blade support (16). The axial securing means (20) have a securing body (22) with a first axial end region (26, 26') and a second axial end region (28), which are interconnected by a connection region (30), whereby the first end region (26, 26') engages behind a front face (32) of the blade root (12) and a front face (30) of the blade support (16) on the flow exit side and the second end region (28) engages behind a front face (34) of the blade support (16) on the flow entry side. Said end regions (26, 26', 28) help to secure the blade (10) against axial forces that originate from the flow and act from the flow entry side in the direction of arrow (A). A spring element (38) is configured in the connection region (36), said element when installed exerting a radial force between the blade root (12) and the base (15) of the radial groove. The force is sufficient to secure the impeller blade (10) in its axial position against axial forces exerted in the entry direction (B) of the flow.

Description

Axial lock for blades

DESCRIPTION

Technical field

The invention relates to an axial securing device for rotor blades of turbomachines through which axial flow flows, according to the preamble of patent claim 1.

Due to the rotation, centrifugal forces act on the blades of turbomachines with axial flow. These forces are generally absorbed by a fir tree or dovetail-shaped design of radially arranged, form-fitting tongue and groove connection between the moving blade and the blade carrier. The axial forces occurring due to the axial flow direction of the flow medium, on the other hand, must be absorbed by means of a separate axial securing device.

State of the art

An example of such an axial lock is known from US-A-2,928,651. To secure the rotor blade in the axial direction, a one-piece securing body made of sheet metal is used, the length of which is greater than the axial extension of the dovetail-shaped blade root or the opposite radial groove of the blade carrier. The end regions of the sheet which act as securing elements serve to absorb the axial forces, which protrude axially beyond the end faces of the blade root or the blade carrier and are bent in the radial direction for holding purposes. The first of the two protruding end regions is divided into two along the central longitudinal axis of the sheet. The two tabs thus emerging from the end region are bent in opposite radial directions for holding purposes in such a way that a first tab engages behind an end face of the blade carrier, while the second tab engages behind a first end face of the blade root. The second of the two protruding end regions is of this type in the assembled state bent over so that it engages behind a second end face of the blade carrier which is oriented opposite the first end face. A tongue protruding from the sheet metal plane in the middle of the sheet metal engages in a wedge-shaped recess in the blade root and also serves to absorb forces acting axially on the blade.

The recess in the blade root is very complex and expensive to manufacture, since with the modern high-performance materials, such as nickel-based alloys or titanium alloys, which are used today for the manufacture of the blades, such recesses can only be produced by grinding or eroding. In addition, assembly and disassembly of axial locks with recesses in the blade root or in the radial groove of the blade carrier, into which a protrusion of the locking body then engages, is usually complex and time-consuming. In the example shown in US Pat. No. 2,928,651, for example for the disassembly, the end region protruding radially outwards, marked with 26, first has to be bent open. In addition, the securing body is formed in one piece from a sheet metal and its end regions as well as the spike-like tongue are produced by bending the sheet metal accordingly. The material of the sheet must be selected so that it can be bent into the required shape on the one hand and still absorb the forces that occur on the other. Such a / rather securing body can therefore only be designed to a limited extent for the possible shear and shear forces, with additional bending of the material being introduced by the bending. Under normal conditions, the known materials used may still barely meet the required properties, but at the high temperatures that occur in a high-speed turbomachine, such as in a turbocharger, it is hardly possible to find a material that is still at the high temperatures the necessary axial securing of the blades in the blade carrier is guaranteed. Furthermore, with such a fuse body, the end regions of the fuse bodies must be bent with high precision in order to fix the blades in their axial position exactly. Presentation of the invention

It is therefore an object of the invention to provide an axial lock of the type mentioned, which is simple and inexpensive to manufacture and assemble, and reliably secures the rotor blades in their axial position.

This object is achieved by an axial securing device with the features of claim 1, in which rotor blades of an impeller are secured by means of a securing body belonging to the axial securing device. The securing body has a first, axial end region and a second, axial end region, which are connected to one another via a connecting region. In the assembled state, the connection area is arranged in a gap formed between the blade root end and the radial groove base. The first end region is designed such that it engages behind an end face of the blade root and the blade carrier on the flow outlet side. The second end region is designed such that it engages behind the end face of the blade carrier on the opposite side of the flow inlet. According to the invention, the connection area has a spring element, with the aid of which, in the installed state, a radially acting force is introduced between the blade root and the radial groove base, which is sufficient to secure the rotor blade in its axial position against axial forces in the direction of flow entry. This configuration makes it possible to design the blade root as well as the radial groove without a radial recess, which considerably reduces the manufacturing costs. In addition, with the help of the axial securing device according to the invention, the securing body can simply be inserted into the radial groove and the blade can then be inserted into the radial groove with the blade root. Disassembly is just as easy in reverse order. No further manipulations such as bending or twisting the securing body or an end region of the securing body are necessary. This reduces the time required for assembly and disassembly.

The spring element can be designed very simply in the form of a shaft in the connection area. The wave can be designed as a single solid wave, as a double or multiple wave, or as a half wave up or down. If the spring element is designed in the form of a wave-shaped bend in the connection area, the securing body is particularly easy to produce. But it is also possible to have the wave already when working out the fuse body from a block of material or when casting etc. into the fuse body so that subsequent bending is not necessary.

It is particularly advantageous if the wave-shaped bending corresponds in its axial extent to approximately two to ten times the radial thickness of the connection area, since the best force ratios are achieved in the gap between the radial groove base and the blade root end.

If the blade root is in frictional contact with the connection area of the securing body over at least half of its axial length, the force effect can be further improved.

If the fuse body is made of a high-temperature steel, it can also be used in high-speed turbo machines without any problems. In a particularly preferred embodiment, the fuse body is made of a nickel-based alloy.

It is particularly easy for the manufacture to form the fuse body in one piece.

Solid noses in the first and second end regions of the securing body ensure particularly good hold in the axial direction, since these cannot be bent open. However, it is also conceivable to design the end regions in the form of bendable sheet ends. No matter how the ends of the fuse body are designed, by casting, by eroding, by punching out of a sheet and / or with the aid of a laser, the fuse body can be produced very easily.

Further preferred embodiments are the subject of further dependent claims.

Brief description of the drawings

The subject matter of the invention is explained in more detail below on the basis of preferred exemplary embodiments which are illustrated in the accompanying drawings. It shows purely schematically: Fig. 1 shows a part of a blade attached to a blade carrier and a

Part of the blade carrier with a preferred embodiment of the axial securing device according to the invention in axial section along a radial groove bottom of the blade carrier;

Fig. 2 in a representation analogous to the representation in Fig. 1, a second embodiment of the axial lock according to the invention;

Fig. 3 in a representation analogous to the representations in Fig. 1 and 2, a third

Embodiment of the axial lock according to the invention; and

Fig. 4 in a representation analogous to the representations in Fig. 1 to 3, a further embodiment of the axial lock according to the invention.

The reference symbols used in the drawings and their meaning are summarized in the list of reference symbols. The described embodiments are examples of the subject matter of the invention and have no restrictive effect.

Ways of Carrying Out the Invention

Figures 1 and 2 each show part of a moving blade 10 with a fir tree-shaped blade root 12, which is held in a fir tree-like radial groove 14 of a blade carrier 16. A securing body 22 of the axial securing device 20 according to the invention is arranged in a gap 18 between the end 13 of the blade root 12 and a radial groove bottom 15 of the radial groove 14 and is formed in one piece in the examples shown. The direction of flow of the working medium acting on the blades 10 is identified by an arrow A in each case. Contrary to this flow A, smaller axial forces act in direction B on the blades 10 in relation to the force acting through the flow A. The axial securing device 20 according to the invention ensures a precise hold of the blades 10 in their axial position against both forces A, B.

The fuse body 22, which is preferably formed from a nickel-based alloy, such as Nimonic 90, has two end regions 26, 26 'and 28 with which the securing body 22 projects beyond the axial extent of the radial groove 14 of the blade carrier 16 or that of the blade root 12. The first end region 26, 26 'of the securing body 22 is designed in the form of a solid double nose. The radially inner nose 26, in the examples shown here, engages behind a blade carrier end face 30 on the flow exit side, the radially outer nose 26 ′ also engages behind a blade root end side 32 on the flow exit side in a form-fitting manner. At a distance from the first end region 26, 26 'in the axial direction, a second end region 28 is arranged which, in the assembled state, engages radially on the inside on an end face 34 of the blade carrier 12 on the flow inlet side. The two end regions 26, 26 'and 28 are axially connected to one another by a connecting region 36. The connecting region 36 has a rectangular cross section with dimensions that are approximately constant over its entire axial length. This enables a very simple manufacture of the securing body 22 and a simple machining of the blade carrier 16 and the blade root 12. However, all other types of cross sections, such as semicircular, polygonal shapes, etc., are also conceivable.

The connection area 36 in FIG. 1 has a spring element 38 in the form of a simple shaft 40 of the connection area 36 on the flow outlet side. This simple shaft 40 has approximately two and a half times the axial extent (not shown to scale) in relation to the radial thickness of the connecting region 36. The shaft 40 can be produced from a block of material during casting or when punching out, milling out or cutting out with a laser but when using materials that allow bending or deep drawing, by appropriate deformation of the connection area. In the latter two methods, the cross section in the region of the shaft 40 can be somewhat reduced in relation to the otherwise approximately constant cross section of the connecting region 36.

The connecting area 36 of the securing body 22 shown in FIG. 2 also has a shaft as a spring element 38, which is designed as a half shaft 42 and, in contrast to the shaft 40 in FIG. 1, is arranged on the flow inlet side. As in all figures, the gap 18, securing body 22 and spring element 38 are not shown to scale for better visibility. However, the radial expansion of the gap 18 between the blade root end 13 and the radial groove base 15 corresponds approximately to the radial thickness of the connecting region 36. The embodiments in FIGS. 3 and 4 differ from the previous ones in that the blade root 12 'and the radial groove 14' are dovetail-shaped. The spring element 38 is in turn designed as a shaft on the flow exit side, in FIG. 3 it being a one and a half times the shaft 44 and in FIG. 4 it is a double shaft 45. The dovetail shape of the blade root 12 'and the radial groove 14' in FIGS. 3 and 4 are designed differently and show, by way of example, that the axial lock 20 according to the invention can be used in all conceivable blade root and radial groove shapes, as long as the blade root 12 and radial groove 14 have a groove. Form a spring connection in such a way that a securing of the blade 10 in the radial direction and in the circumferential direction is ensured.

The axial lock 20 according to the invention, as shown in FIG. 5, corresponds in principle to that as shown in FIG. 1. However, in this embodiment, the end regions 26, 26 'and 28 are produced in a known manner by bending and instead of a simple shaft or a double shaft, a multiple shaft 48 is arranged approximately axially in the middle of the connecting region 36.

As can be clearly seen in FIGS. 1 and 2, the blade root 12 is in frictional contact with the connecting region 36 of the securing body 22 in the case of the spring elements 38 configured as simple shafts 40, double shaft 45 or multiple shafts 48 on both sides of the shafts 40, 45, 48. This is particularly advantageous since during operation, in addition to the radial force introduced between the blade end 13 and the radial groove base 15 by means of the spring element 38, centrifugal forces act on the securing body 22 and blade 10, which in a configuration of the spring element 38 as a simple shaft 40, 45, 48 increase the frictional force acting on both sides of the spring element. In contrast to this, the design of the spring element 38 as a half-shaft 42 or a half-shaft 44 means that the blade root 12 is in frictional contact with the connecting region 36 of the securing body 22 only on one side of the shaft 42, 44 and, if necessary, with several shaft arches with one or a plurality of wave arches 46, as shown in FIG. Instead of half waves and one and a half times waves, two and a half, three and a half times, etc. waves can be provided. The axial extent of the shaft, irrespective of how it is designed in detail, whether as a half-wave, a simple shaft or a multiple shaft, can be in the range from approximately two to ten times the radial thickness of the connecting region 36. It is advantageous if in total at least half of the axial extent of the blade root 12, this is in frictional contact with the securing body 22, since then the effect of the centrifugal forces can be better exploited. The design of the spring element 38 as a half-wave, simple, wave, etc., its axial extent, as well as its arrangement in relation to the axial extent of the connecting region 36 in the gap 18, is dependent on the acting forces and the geometry of the rotor, the blades 10 and the blade carrier 16th

No matter what the detailed design of the securing device 20 looks like, assembly and disassembly are always the same simply and quickly: for assembly, the securing body 22 is inserted into the radial groove 14 in such a way that the end regions 26 'and 28 engage behind the two end faces 30, 34 of the blade carrier 16. The rotor blade 10 is then inserted radially above the securing body 22 into the radial groove 14, the radially acting force introduced by the spring element 38, which is noticeable as frictional resistance, having to be overcome. The rotor blade is pushed into the radial groove 14 until its end 32 on the flow outlet side is brought into abutment with the radially outer nose 26 'of the first end region 26, 26'. The reverse procedure is followed for disassembly. The large axial forces acting in the flow direction A are absorbed by the end regions 26, 26 'and 28, while the much smaller axial forces acting in the opposite direction B counteract the frictional force which results from the radial tensioning of the blade root 12 in the radial groove 14 which is introduced by means of the spring element 38 results.

LIST OF REFERENCE NUMBERS

A direction of flow from the

B flow direction from the

5 flow outlet side

10 barrel shovel

12 blade root

13 blade foot end

10 14 radial groove

15 radial groove bottom

16 shovel carriers

18 radial gap

20 axial lock

15 22 Safety body

26, 26 'first end region

28 second end area

30 front side of scoop carrier

Flow outlet side

20 32 Front end of the blade root

Flow outlet side

34 front side of scoop carrier

Strömungseintittsseitig

36 Connection area

25 38 spring element

40 simple wave

42 half wave

44 one and a half times the wave

45 double shaft

30 46 waves

48 multiple wave

Claims

cLAIMS

1. Axial securing for rotor blades (10) of turbomachines with axial flow, in which the rotor blades (10) are secured radially and in the circumferential direction by means of a blade root (12) which is axially inserted into a radial groove (14) of a blade carrier (16), the axial securing means ( 20) comprises a securing body (22), which

Means for securing the securing body (22) with respect to the blade carrier (16) against the flow direction, means for securing the moving blade (10) with respect to the securing body (22) in the flow direction, means for securing the securing body (22) with respect to the blade carrier (16) in Flow direction, as well as means for securing the rotor blade (10) with respect to the securing body (22) against the flow direction, characterized in that at least one of the means for securing from a frictional connection between the securing body (22) and the moving blade (10) or the Fuse body (22) and the blade carrier (16), and that the frictional connection is acted upon by a radially directed spring force.

2. Axial securing device according to claim 1, characterized in that the securing body (22) comprises a first, axial end area (26, 26 ') and a second, axial end area (28) which are connected to one another by means of a connecting area (36), wherein the connecting region (36) in the assembled state of the securing body (22) in a gap formed between the blade root end (12) and the radial groove base (15)

(18) is arranged such that, as a means for securing the securing body (22) with respect to the blade carrier (16) against the direction of flow, the first end region (26, 26 ') engages behind an end face (30) of the blade carrier (16) on the flow outlet side that as a means for securing the rotor blade (10) with respect to the securing body (22) in the flow direction, the first end region (26, 26 ') has an end face (32) of the

Blade root (12) engages on the flow outlet side, that as a means for securing the securing body (22) with respect to the blade carrier (16) in the flow direction, the second end region (28) engages behind an end face (34) of the blade carrier (16) on the flow inlet side, and that as a means for securing the rotor blade (10) with respect to the securing body (22) against the

Flow direction of the fuse body (22) in the connection area (36) a radial Acting spring element (38) which forms the frictional connection with the blade root (12).

3. Axial lock according to claim 2, characterized in that the spring element (38) is designed in the form of a shaft (40, 42, 44, 45, 48) of the connecting region (36).

4. Axials / cherung according to claim 3, characterized in that the shaft (40, 42, 44, 45, 48) corresponds in its axial extent approximately twice to ten times the radial thickness of the connecting region (36).

5. Axial lock according to one of claims 2 to 4, characterized in that the radial extension of the gap (18) between the blade end (13) and

Radial groove base (15) corresponds approximately to the radial thickness of the connecting area (36).

6. Axial lock according to one of claims 2 to 5, characterized in that the blade root (12) is in frictional contact in the installed state over at least half of its axial length with the connecting region (36) of the securing body (22).

7. Axial securing device according to one of claims 2 to 6, characterized in that the material of the securing body (22) is a high-temperature steel and in particular a nickel-based alloy.

8. axial securing device according to one of claims 2 to 7, characterized in that the securing body (22) is integrally formed.

9. Axial lock according to one of claims 2 to 8, characterized in that the first end region (26, 26 ') and the second end region (28) are designed in the form of solid lugs.

10. Axial securing device according to one of claims 2 to 9, characterized in that the securing body (22) is produced by punching out a sheet metal, eroding, milling and / or using a laser.