GB2488864A

GB2488864A - Rotor blade retained by spacer

Info

Publication number: GB2488864A
Application number: GB1201402.3A
Authority: GB
Inventors: Luis Frederico Puerta; Tihomir Stojkovic; Wolfgang Kappis; Erik Peter Boldt
Original assignee: Alstom Technology AG
Current assignee: General Electric Technology GmbH
Priority date: 2011-03-07
Filing date: 2012-01-27
Publication date: 2012-09-12
Anticipated expiration: 2032-01-27
Also published as: AU2012200534A1; CH704617A1; AU2012200534B2; GB201201402D0; GB2488864B

Abstract

A rotor of a turbomachine has a circumferential slot with a fir tree profile. The slot accommodates root sections 4 of rotor blades 5 and also filler pieces or spacers 3 which are arranged between circumferentially adjacent root sections 4. The filler pieces 3 have complementary fir tree profiles in such a way that the filler pieces 3 are fixed in a form-fitting manner in the slot 2 in the radial direction of the rotor 1. The root sections 4 of the rotor blades 5 are connected to the filler pieces 3 by means of shoulders 40 which project from the root sections 4 and are radially supported on an underside of the filler pieces 3. The shoulders 40 may be received in a groove (43, figure 3) allowing the spacer to extend to the base of the slot.

Description

Rotor blade arrangement of a turbomachine

Technical field

The invention relates to a rotor blade arrangement of a turbornachine, such as an axial turbine or axial.

compressor, having -a rotor, which has at least one circumferentially encompassing slot with undercut flanks in the style of a fir tree profile, -a plurality of rotor blades, which have root sections projecting into the encompassing slot, and -filler pieces or spacers, which can be inserted, or are inserted, into the slot between the root sections of circumferentially adjacent rotor blades and have a profile which is basically complementary to the profile of the slot, wherein the filler pieces or spacers, by way of contact surfaces which are turned radially outwardly with regard to the rotor, butt against, or can butt against, undercut faces of the flanks of the slotS

Technological background

For the rotor blades, which are extremely stressed during operation of a turbomachine, various possibilities of anchoring on the rotor are known. On the one hand, axial segments of the rotor can have axial slots distributed uniformly over the circumference, the axial segments having an undercut dovetail profile or the like so that the rotor blades, by way of root sections which are correspondingly arranged or formed on them, can be inserted axially into the slots of an axial segment. The principle disadvantage of such a construction lies in the fact that the number of rotor blades, which are arranged next to each other in the circumferential direction of the rotor segment, is invariable. If a design with a modified number of rotor blades should therefore be desired, significant adjustments are necessary during manufacture.

In the case of welded rotors and also in the case of built up rotors, the possibility exists of the rotor being provided with circumferentially encompassing slots which have a multiply-undercut profile, for example in the style of a fir tree profile. These slots can be used for accommodating correspondingly formed root sections of stator blades and also for accommodating filler pieces or spacers which are arranged in each case between root sections of circumferentially adjacent rotor blades in order to ensure a rotor circumferential surface without cavities between the adjacent rotor blades, or to determine the spacing of the adjacent rotor blades in the circumferential direction of the rotor. By means of a separable filler piece or spacer, the parts which are inserted into the respective circumferential slol can be fixed in the circumferential direction of the rotor.

This known construction is particularly suitable for large and heavy-duty rotor blades as they are typically arranged on the rotor at the inlet-side end of the respective turbomachine.

Also known in principle are similar constructions in which only the filler pieces or spacers are radially fixed inside a rotor-side slot -which extends in the circumferential direction of the rotor and has undercut flanks -by means of a form f it with these flanks, whereas the rotor blades or their roots are mounted on the filler pieces or spacers in a form-fitting mannerS For this purpose, provision is made on the roots of the s rotor blades in each case for shoulders which project in the circumferential direction of the rotor and which fit under a side of the filler pieces or spacers facing the bottom surface of the slot when the filler pieces or spacers occupy their specified position on the rotor. For this purpose, the filler pieces or spacers are formed with comparatively lower thickness in the radial direction of the rotor in such a way that an adequate clearance remains for accommodating the aforesaid shoulders between the bottom surface of the encompassing slot on the rotor and the side of the respective filler piece or spacer facing this bottom surface. Associated with this is the principle disadvantage that the undercut faces -which are provided for the radial fixing of the filler pieces or spacers -on the flanks of the encompassing slot of the rotor must have a comparatively large radial distance from the bottom surface of the slot. This has the result that only comparatively few. undercut faces, which can radially outwardly interact with corresponding contact surfaces of the filler pieces or spacers for their fixing, can be applied to the flanks.

As a result, the high centrifugal forces of the filler pieces or spacers and also of the rotor blades mopnted thereupon or of the associated rotor blade roots which occur during operation of the turbomachine can be transferred onto the rotor only over small material areas in respect to volume! The last-described type of construction is therefore not readily suitable for heavy-duty rotor blades or extreme centrifugal forces!

Summary of the invention

This is where the invention comes in. It is the object of the invention to create a rotor blade arrangement which can be used as universally as possible.

This object is achieved according to the invention by the filler pieces or spacers having cross-sectional regions, adjacent to the flanks of the slot, which extend up to flank-side regions of the bottom surface of the slot, and by the root sections of the rotor blades, on their end faces facing the filler pieces or spacers, having projecting shoulders which can be inserted, or engage, in matching recesses on the filler pieces or spacers between the aforesaid cross-sectional regions.

The invention is based on the general idea of adapting the cross section of the filler pieces or spacers to the depth of the associated rotor-side slot in such a way that the flanks of the slot can be in form-fitting engagement with adjoining regions of the filler pieces or spacers over the entire depth of the slot. The fir tree-like profiling of the flanks of the slot and also the profiling -which is adapted thereto -of the sides of the filler pieces or spacers facing the slot flanks can therefore be continued right into the direct vicinity of the bottom surface of the slot. As a result, the possibility is presented in this way of extensively transferring centrifugal forces, which act upon the filler pieces or spacers, onto the rotor over large cross-sectional regions.

According to a preferred embodiment of the invention, it is intended to form the recesses for the shoulders of the rotor blade roots on the side of the filler pieces or spacers facing the bottom surface of the slot in such a way that these recesses are open towards the -5-.

bottom surface and towards the adjacent root sections of the rotor blades. Therefore, the root sections of the rotor blades, in axial view of the rotor, can have an inverted T-profile which extends right into the direct vicinity of the bottom surface of the slot, and by way of shoulders which point in the circumferential direction of the rotor can be inserted into the aforesaid recesses on the filler pieces or spacers.

This type of construction presents, on the one hand, the advantage of comparatively simple producibility, specifically regardless of whether processes involving a forging technique, or metal-removing machining processes, or other methods of production, are to be used for the production of the filler pieces or spacers and/or of the root sections of the rotor blades. The possibility is also presented of arranging conventional fixing wires in the gap between the bottom surface of the slot and the facing side of the root sections in order to Cix the root sections in a frictionally locking manner in the circumferential direction of the rotor.

In other respects, with regard to preferred features of the invention, reference is made to the claims and to the subsequent explanation of the drawing, on the basis of which especially preferred embodiments of the invention are described in more detail.

Protection is claimed not only for disclosed or depicted feature combinations but also for principally any combinations of the disclosed or depicted individual features.

Brief description of the drawing

In the drawing Fig. 1 shows a perspective view of a root section of a rotor blade, Fig. 2 shows a further perspective view of the root section, -Fig. 3 shows a perspective view of a filler piece or spacer, Fig. 4 shows a perspective view of a root section of a rotor blade and also of a filler piece or spacer which is adiacent thereto, and Fig. S shows an axial section in detail of a rotor in the region of an encompassing slot with a filler piece or spacer arranged therein and also with a root section of a rotor blade.

Ways of implementing the invention The invention is subsequently explained in more detail with reference to embodiments and to the figures.

According to Fig. 5, a turbomachine, such as an axial turbine or axial compressor, has a rotor 1 which is built rotationally symmetrically to a longitudinal axis or rotational axis 100 and can be assembled from disk-like segments which are welded together and/or screwed together. The longitudinal axis 100 in this case defines the axial direction of the rotor 1. For arranging rotor-side rotor blades 5, provision is made on the rotor 1 in the circumferential direction for encompassing slots 2 which have a fir tree-like profile in such a way that a plurality of undercut faces 20 are formed on the flanks of the respective slot 2. Filler pieces or spacers 3 are arranged in the slot 2 on one side, and root sections 4 of rotor blades 5 are arranged on the other side. The filler pieces or S spacers 3 are also shown in Figs. 3 and 4. The rotor blades S are also shown in Figs. 1, 2 and 4, at least in the region of the root sections 4. In this case, the filler pieces or spacers 3 have a profile which is basically complementary to the profile of the slot 2 and fit under or fit behind the undercut faces 20 on the flanks of the slot 2 by way of contact surfaces 30.

As a result, the filler pieces or spacers 3 are therefore fixed by means of a form fit inside the slot 2 in the radial direction of the rotor 1. The rotor blades S or their root sections 4 are fixed radially in the slot 2 indirectly via the filler pieces or spacers 3. For this purpose, projecting shoulders 40 are arranged on the end faces 46 of the root sections 4 facing the filler pieces or spacers 3 in the circumferential direction and in the installed state of the rotor blades S fit under or fit behind an underside 43 of the filler piece or spacer 3 which faces the rotational axis 100 and in each case is adjacent in the circumferential direction. This underside 43 of the filler piece or spacer 3 in the depicted examples has a recess 31 which is axially delimited by means of ribs 44. The shoulders 40 of the root sections 4 expediently act on the filler pieces or spacers 3 in the region of these recesses 31. These recesses 31 are therefore formed on the side facing a bottom surface 45 of the slot 2, that is to say on the underside 43 of the filler pieces or spacers 3, as can be gathered especially from Fig. 3.

The width of the recess 31, measured in the transverse direction of the slot 2, that is to say in the axial direction, is significantly smaller than the width of the filler piece or spacer 3 in such a way that on the sides of the filler pieces or spacers 3 facing the flanks of the slot 2 cross-sectional regions, specifically the previously mentioned ribs 44, remain and extend up to the bottom surface 45 of the slot 2.

S In this way, with the corresponding design of the fir tree-like profile of the slot 2 on the filler piece or spacer 3, the possibility is presented of also arranging contact surfaces 30 close to the bottom surface 45 of the slot 2, which contact surfaces then interact with undercut faces 20 -which are close to the bottom -on the flanks of the slot 2.

The ribs 44 create a reinforcement or stiffening of the respective root section 4 in the region of the radially further inwardly lying contact surfaces 30, that is to say the contact surfaces which are arranged closer to the bottom surface 45. Alternatively, these ribs 44 can also be dispensed with, however, as a result of which the bottom side 43 can especially be of a completely flat design.

In the examples, the shoulders 40 are arranged or formed in the region of a. radially inner end of the respective root section 4 facing the rotational axis 100. Therefore, the shoulders 40, on an underside 47 of the root section 4 facing the rotational axis 100, project in the circumferential direction and consequently enlarge the flat underside 47.

As especially Fig. 5 shows, the cross section of the root sections 4, measured parallel to the rotational axis 100, widens with increasing distance from the bottom surface of the slot 2 and fits snugly against the flanks of the slot 2 close to the circumferential surface of the rotor 1. Close to the circumferential surface of the rotor I, the cross section of the root sections 4 therefore has a cross-sectional shape which is identical to the cross section of the filler pieces or spacers 3 so that the filler pieces or spacers 3 and the root sections 4 closely interface with the circumferential surface of the rotor in the same way.

In other respects, the root sections 4 can be inserted into the slot 2 in the radial direction of the rotor 1.

As can be gathered especially from Figs. 4 and 5, relief grooves 32 are provided in the transition region between the contact surfaces 30 and the adjoining body of the filler pieces or spacers 3 in order to avoid excessive material stresses in the transition region between the contact surfaces 30 and the body of the filler pieces or spacers 3 if extreme centrifugal forces act upon the filler pieces or spacers 3 during operation of the turbomachine In a corresponding manner, relief grooves 22 are also provided on the flanks of the slot 2 next to the undercut faces 20, cf. especially Fig. 5. Similar relief grooves 42 are provided on the shoulders 40 of the root sections 4. With regard to the optimum shape of these relief grooves 22, 32 and 42, reference can be made to 135 2009/0087316 AL A compression spring, which tries to lift the respective root section 4 in relation to the bottom surface 45 of the slot 2, can be arranged in a cut-out (not shown) -which is open towards the bottom surface of the slot 2 -in the root section 4 of each rotor blade 5. As a result, the root sections 4 are fixed without clearance inside the slot 2 together with the filler pieces or spacers 3 in the installed state. In other respects, the root sections 4 can be fixed in a frictionally locking manner in the slot 2 in a basically known manner by means of fixing wires 6.

These fixing wires 6 can be pulled in between the bottom surface 45 of the slot 2 and facing side of the respective root sections 4, cf Fig. 5.

-10 -The root sections 4 and also the filler pieces or spacers 3 can be produced in basically any manner, for example these parts can be formed as forged parts.

Instead of this, it is also possible and, at least at the present time from the cost point of view, advantageous to produce these parts by means of metal-cutting machining from a solid block.

-11 -List of designations 1 Rotor 2 Slot 3 Filler pieces, spacers 4 Root sections Rotor blades 6 Fixing wires Undercut face 22 Relief groove Contact surface 31 Recess 32 Relief groove Shoulder 42 Relief groove 43 Underside of 3 44 Rib Bottom surface of 2 46 End face of 4 47 Underside of 4 Rotational axis