WO2001071166A1

WO2001071166A1 - Turbine rotor blade

Info

Publication number: WO2001071166A1
Application number: PCT/EP2001/002629
Authority: WO
Inventors: Peter Tiemann
Original assignee: Siemens Aktiengesellschaft
Priority date: 2000-03-21
Filing date: 2001-03-08
Publication date: 2001-09-27
Also published as: EP1136654A1

Abstract

The invention relates to a turbine rotor blade assembly comprising several turbine rotor blades (2) which are offset in the peripheral direction of a turbine rotor (1), each having a blade foot (3) that can be inserted longitudinally into a turbine rotor groove (6) and that can be held in a radial position so that it cannot be removed, by longitudinal teeth in the groove (7) which engage with the longitudinal teeth (5) of the foot in a positive-fit. The aim of the invention is to configure said turbine rotor blade assembly in such a way that turbine rotor blades (2) can be inserted at helix angles which are greater than currently achieved. To achieve this, the blade foot (3) has a localised material weakness on its front face (8).

Description

description

TURBINE MOVING BLADE

The invention relates to a turbine blade arrangement with several m circumferential circumferences of a turbine disk, with a blade root which is staggered, each having a blade root, which has two longitudinal sides and end faces, has longitudinal teeth on its longitudinal sides and which in a turbo person is longitudinally slidable and there through groove. slow tooth, which engages behind its longitudinal tooth, is held radially against extraction.

Turbine impeller blades with grooves in a Turbmen disc are severely stressed in their groove areas by the centrifugal forces acting on the turbine blade when the turbine disc rotates. "In order to have a large contact surface, the holding devices of the foot in the groove are designed as slanted longitudinal teeth. The centrifugal forces, which point radially outwards, are introduced through the longitudinal tooth in the longitudinal tooth of the groove. Since the longitudinal teeth are in contact, this introduction deflects some of the centrifugal force. Especially in the front area of the foot, the forces introduced are very stressful for the groove area, since they rise abruptly there. This creates a particularly heavy load in the lower groove area, which can lead to cracks.

In addition, attempts are being made to improve the effectiveness of modern turbine blades by setting up the turbine blades in certain outflow angles relative to the flow of working fluid. Here, the rotor blade roots are inserted at an angle to the turbine disk axis m, the turbine disks, as a result of which the grooves and the blade roots are exposed to strongly inhomogeneous stresses under operating load. This leads to increased age stress with itself, so the inclination is limited to angles up to approx. 15 °.

It is therefore an object of the present invention to provide a turbine blade arrangement which allows turbmer blades to be used in helix angles which are larger than hitherto achieved without endangering the strength of the groove areas.

The object is achieved in that the blade root has local material monitoring on its end face.

The invention has the advantage that fl enicra-induced voltage peaks are caught and are therefore not introduced into the end soapy area into the surrounding longitudinal slot teeth, but rather further inside, in the middle of the blade root. This advantage is achieved in that the material is locally weakened on the front side. A material weakening is present if the surrounding areas have a greater rigidity, for example because the material is thinner at the weakening. Thus, the GESAM ^¬ te is reduced resulting stiffness of this area. Because when a load is applied, the soft, weakened area is deformed first. The material is no longer as rigid. In this way, only a reduced transmission of force to the surrounding groove can take place in this area. The normally very rigid end faces of the blade root are made more resilient to stresses by the proposed arrangement. There is therefore a load redistribution in the direction of the blade center, which reduces local stress increases in the groove end area. The weakening of the material is appropriate locally, because the foot should still have sufficient strength and, despite the weakening, a certain proportion of the centrifugal force carrying the blade should still be transmitted. The proposed arrangement prevents such high voltages from attacking on the end faces of the longitudinal tooth that damage occurs entstenen. In this way, for example, stress peaks due to fit failures, such as occur even with very careful post-machining of the turbine blade root, can be compensated for. As a result of the proposed arrangement, the service life of the turbine blade arrangement is increased and fewer faults occur during operation.

Material monitoring that is easy to calculate and reproducible is provided if the blade root has a recess on its end face. The recess softens the forehead region of the foot against the attacking centrifugal force, so that it can be elastically compressed under the application of force. A smaller proportion of the force is introduced into the end region of the groove, and thus a larger proportion into the region of the center of the foot. By changing the

Shape or the dimensions of the recess can be much more impressive ^¬ influ- the elastic properties of the recess portion. The recess on the end face of the blade root can be made during the casting by inserting a casting core from the outside or subsequently by mechanical processing.

If the recess is a wedge-shaped notch on the end face of the blade root in the area between the longitudinal teeth closest to the axis of the turbine disc and the recess is open at an end of the blade root on the disc axis side, forces can be caused by elastic bending of the side flanks of the wedge-shaped notch be caught softly in this area. A smaller proportion of the force is transferred to the surrounding groove area. The load capacity is thus diverted to an area in the direction of the center of the blade root. This spring-like folding of the wedge-shaped notch is limited by the fact that no permanent plastic deformations may occur. This can be achieved, for example, by maintaining the dimensions and shapes of the recess, in particular a certain width and depth, which, for example, depend on the bucket weight, but also on the opening flap in the groove and the manufacturing tolerances observed.

A very good derivation of the stresses in the blade center areas is given when the recess ver n cross-sectionally direction of a blade platform. The larger the cross section and in particular the width and therefore the greater the distance between the flanks of the recess, the softer the recess and the less resistance it opposes to elastic deformation. Thus, the lowest stresses are introduced into the lowest region of the ends of the grooves, which are most at risk of jamming, whereas higher stresses are introduced against m groove regions, which are a distance from the disk axis in the direction of the blade platform. These groove areas are designed to be more stable and can offer greater resistance to bending stresses.

If the recess has a maximum depth decreasing in the direction of the blade platform, the recess is softest in the end area on the disc side and becomes increasingly hard from there towards the center of the blade root with decreasing width. The maximum notch depth can moreover be easily adapted in this way to a possible helix angle of the blade root by increasing the depth with increasing helix angle.

If the recess has a rounded contour, it is ensured that the contact forces can be derived more smoothly. This prevents crack peaks from forming in the recess, for example in the event of changes in force and changes in the direction of force, which lead to damage to the material.

If each of the two end faces of the blade root has local material monitoring, on both end faces the similar and with symmetrical design of the blade have the same voltage increases, to obtain similar or the same advantageous effects.

Coolant can be penetrated through the blade root and at the same time an efficiency improvement can take place due to an inclined position if the blade root has a cavity which has an access at the end of the blade root on the axis of the blade and the local material monitoring has such a distance from the access that under the operating load of the Turbine rotor blade the required stability is guaranteed. Through the access, coolant can be passed through the blade root and through the blade profile. At the same time, the local centrifugal force distributes the attacking centrifugal force towards the center of the blade root. In addition, the strength of the blade root is also given in the forehead area in that a sufficient wall thickness on the front side of the blade root is ensured in spite of the local material monitoring. All of the advantages of the invention can thus be used and at the same time an internal cooling of the blade profile or a weight reduction can be carried out due to the hollowing out of the blade root.

If the cavity at the end of the disk axis has a plurality of accesses which are arranged offset on a longitudinal axis and the local material monitoring on the end face is also at least partially on the longitudinal axis, a stress distribution is achieved centrally along the longitudinal axis. The voltage is thus diverted symmetrically to the two flanks of the groove. The forces are evenly distributed on both sides of the groove, thereby avoiding any excessive tension in the center area. Several entrances ensure stabilization in the walls between the entrances, thereby evening out the force distribution. In particular, sufficient stability the distance from the local material monitoring to the access closest to the recess.

If the blade root, which starts from the disk axis in a star shape and is rotated through the radial axis through the blade root, is rotated through the turret disk, a strongly asymmetrical power transmission and an associated increase in Soannurgs are observed in the area of the ends of the lowermost slot teeth. In particular, the groove ends, which encompass the forehead areas of the feet, are subjected to a strong asymmetrical load due to the forces transmitted to them. This asymmetrical load in the end area, due to the bending stresses that arise and the associated crack nucleation, is a limit for the improvement of the effective cross-section due to the inclined position of the blade root αar. the local material monitoring according to the invention acts in particular against the recess in that the material of the foot behaves softer in this weakened forehead region. In this way, the main load absorption of the component lying in the circumferential direction of the turbine disk of the contact pressure which arises under centrifugal force loading takes place at the further inner regions of the groove. Bending of the asymmetrically loaded groove is thus prevented even at steep angles of the blade root. In this way, a very large improvement in efficiency can take place by inserting blades which are inclined under large outflow angles without loss of strength, for example due to crack nucleation due to bending stresses in the end regions of the grooves.

The softness of the end face of the foot can be individually adapted to the needs caused by the inclination of the blade root if the width, the depth and the shape of the recess are matched to the angle and the spacing of the turbine blade root. A softening of the entire front side of the blade root is αadurcn that the recess runs from the end of the blade root on the disk side to between the two opposite longitudinal teeth of the platform. In this way, force vertexes with large maxima can be compensated.

An exemplary embodiment of the invention is given in the figures. Show it:

1 is a perspective view of a turbine blade with a recess,

2 shows a longitudinal section through the recess,

3a, b, c cross sections parallel to a platform area through the foot area with recess,

4 shows a schematic view of the turbine blade root in view II-II,

5 shows a schematic plan view of a circumferential area of a turbine disk with turbine blades and

6 shows a side view of the foot with a recess.

Fig.l shows a perspective view of a turbine blade 2. The turbine blade 2 consists of a blade profile 10, which is adjacent to a parallelogrammfor ig beveled blade platform 11, which forms the conclusion of the underlying blade root 3. The blade root 3 likewise has a parallelogram-shaped cross section parallel to the blade platform 11. The platform 11 has a helix angle 24 relative to the vertical 14 on an end face 8 of the blade root 3. The blade root 3 has a fir-tree-shaped cross section parallel to its end face 8, which has projecting longitudinal teeth 5 running parallel to one another along the two parallel longitudinal sides 4 of the blade root 3 and tapering 3 mm narrower towards an end 17 of the base on the disc axis side. The longitudinal teeth 5 are related to a longitudinal axis of the blade 23 undercuts forming radial contact. The blade foot 3 is inserted into a correspondingly negatively shaped turbomachine disc 6 with longitudinal teeth 5 receiving longitudinal cutouts 15 along its longitudinal sides 4 and decogenous elements on the axis of the turbine disk 1 are held radially by means of slot teeth 7 corresponding to the longitudinal teeth 5 , The region 26 of the turbine disk 1 lying parallel to the surface and lying between two blades 2 and parallel to the surface is thus stressed by the two adjacent turbine blades 2 in opposite directions. The forces represented by the force vector arrows 30, n circumferential πchtung the Turmnenscheibe 1 cancel each other in the central region 28 mutually Anna nernd on _^ e indicated in Fig.5. However, this is different in the end regions 29 of the grooves 6. Here, due to the parallelogram shape of the region 26, there are no counterforces in the end region 29 and thus asymmetrical distribution of forces and thus a bending stress. The greater the bevel angle 24, the greater the bending stress.

This is inventively countered by the fact that the blade root 3 has a local material monitoring in the form of a recess 9 on the end face 8. In a region 13 at the end 17 of the foot 3 on the disc axis side, at which the foot 3 tapers narrowly, the recess 9 is located approximately centrally between the longitudinal axis teeth 5 next to the disc axis tapered to the other end face 8 hm, rounded edges 12. The recess 9 is open to the end 17 of the foot 3 hm on the disc axis side. When the blade root 3 is loaded with centrifugal forces directed in the direction of the longitudinal axis 23 of the blade, the longitudinal teeth 5 are pressed against the lower tooth flanks of the longitudinal teeth 7. The forces in this end face area are therefore not so strongly introduced into the surrounding groove areas, rather the force transmission is shifted further into the central region 28 of the region 26.

2 shows a longitudinal section through the area of the blade root with recess 9. The recess 9 has its greatest height 27 directly on the end face 8 and falls rounded off towards the center of the blade root 3.

3a, b, c show cross sections parallel to the blade platform 11 through the foot area with the outer dimension 9 along the section lines III a, b, c from FIG. The cross sections have a maximum depth 18 which is at a distance from the end 17 on the disc axis side and with an approach to the blade platform 11. Likewise, the maximum width 16 of the recess 9 increases at a distance from the end 17 on the disc side. The slope of the flanks 12 of the recesses 9 is adapted to this decrease, but is essentially constant.

Fig. Shows a top view II-II of the disc axis end 17 of the foot 3 from Fig.l. In addition to the recesses 9 arranged on both end faces 8, the foot 3 has four approaches 19 of approximately the same elliptical cross section to an internal cavity, which is not shown. The accesses 19 are separated from one another by central walls 22. Both the accesses 19 and the recesses 9 lie with their longitudinal extensions along a longitudinal axis 21 of the foot, which runs parallel to the longitudinal sides 4 of the foot 3 in the middle between them. The recesses 9 are at a distance 20 from the adjacent accesses 19. Between the recess 9 and the adjacent access 19 there is thus a wall 31 through which the force deflection deflected from the end face 8 into the surrounding groove area takes place. Through the recesses 9, the end faces 8 m are softer the end region 17 on the disc axis side.

Through the accesses 19, the blade profile 10 of the turbine blade 2 can be supplied with coolant. The Middle Iwan de 22 strengthen the disc area on the side of the disc axis and ensure sufficient resistance to the stress caused by the attacking forces of the flies.

5 shows a plan view of a circumference of a turbine disk 1 with grooves 6 of turbine blades 2 inserted, which are at a distance 25 from one another between corresponding longitudinal sides. The platforms 11 and with them the feet have an angle 24 to a perpendicular 14 on the front side of the turbine disk. When the turbine disk 1 rotates, the turbine blades 2 load the areas 26 of the turbine disk lying between the grooves 6. In particular, at the end regions or grooves 6 there are no longer sufficiently compensating forces from two adjacent blades, so that there is an asymmetrical stress in these end regions, which are dashed n in FIG. 5. This is remedied by the recess 9 in the front area 8 of the blade root 3. The recess 9 makes the forehead area 8 softer, i.e. it is no longer possible to exert such strong forces in this area on the surrounding groove areas. As a result, the maxima of the force distributions are increasingly shifted in the direction of the central region 28 of the region 26, where large forces can also be absorbed without damage, even at large angles 24 of more than 15 °.

6 shows a view of the front region 8 of the foot 3. The front region 8 has an elongated recess 9. The recess 9 is open at the disk-side end region 17 of the foot 3 and extends from the sheath-side end region 17 to between the uppermost long teeth 5. As a result, the areas between the middle and the upper, opposite foot longitudinal teeth 5 can also be resiliently loaded. Voltage peaks in the forehead area 8 can be compensated for more effectively.

Claims

claims

I. Turbine blade arrangement with a plurality of circumferential directions of a turbine disc (1) arranged in a turbine blade (2), each with a blade root (3), each having two long sides (4) and end faces (8), longitudinal teeth (5) on its long sides (4) and which can be inserted longitudinally into a turbine disk groove (6) and is held there radially in a pull-out manner by slot teeth (7) which engage behind its bottom teeth [5) in a form-fitting manner, characterized in that the blade root (3) has local material monitoring on its end face (8) having.

2. Turbine rotor blade arrangement according to claim 1, that the blade root (3) has a recess (9) on its end face (8).

3. Turbine blade arrangement according to claim 1 or 2, characterized in that the recess (9) has a wedge-shaped notch on the end face (8) of the blade root (3) in the region (13) between the closest longitudinal teeth (13) between the axis of the turbine disc ( 5), and the recess (9) is open at an end (17) of the blade root (3) on the disc axis side.

4. Turbine rotor blade arrangement according to one of claims 1 to 3, d a d u r c h g e k e n z e i c h n e t that the recess (9) tapers in cross-section in the direction of a blade platform (11).

5. Turbine rotor blade arrangement according to one of claims 1 to 4, characterized in that the recess (9) has a decreasing maximum depth (18) in the direction of the blade platform (11).

6. Touring rotor blade arrangement according to one of claims 2 to 5, d a d u r c h g e k e n z e i c h n e t that the recess (9) has a rounded contour.

7. Turomenschaufelanordnung according to any one of claims 1 to 6, d a d u r c n g e k e n n z e i c h n e t that each of the two end faces (8) of the blade root (3) each has a local Mateπaischüberwachung.

8. Touring rotor blade arrangement according to one of claims 1 to 7, characterized in that the blade root (3) has a cavity which has an access (19) at the disk-axis-side end (17) of the blade root (3) and the local material monitoring such a distance (20th ) to the access (19) that the required stability is guaranteed under the operating load of the turbine blade (2).

9. Turbine rotor blade arrangement according to one of claims 1 to 8, characterized in that the cavity at the disc-axis-side end (17) has a plurality of offset on a longitudinal axis (21) arranged accesses (19) and the local material monitoring on the end face (8) also at least partially the slow axis of the foot (21).

10. Turb enlaufschaufelanordnung according to any one of claims 1 to 9, characterized in that the blade roots (3) about the star axis from the disc axis, through the blade root (3) extending radial axes rotated through an angle (24) m the turbine disc (1) is inserted.

11. Turbine rotor blade arrangement according to one of claims 1 to 10, characterized in that the angle (24) is greater than approximately 15 °.

12. Turbine rotor blade arrangement according to one of claims 1 to 11, characterized in that the width (10), the depth (11) and the shape of the recess (9) on the angle (24) and the distances (25) of the turbine blades (2) are coordinated.

13. Turomenlaufscnaufe_anordnung according to any one of claims 1 to 12, d a d u r c h g e k e n n z e i c h n e t that the Aussennung (9) from the disc-side end (17) of the blade root (3) b s between the two next platform, opposite foot longitudinal teeth (5).