Blade arrangement

Abstract

A blade arrangement is provided having a blade carrier and a retaining groove arranged therein, which retaining groove has projections extending along side walls thereof forming undercuts and into which a number of blades are inserted forming a blade ring of a turbomachine. Each blade has a blade root which engages into the undercuts, and each blade is pressed against the projections by an element arranged between a blade root underside and a groove base of the retaining groove. It is further provided that each element is of plate-like form and has, in the projection of the blade airfoil in the direction of the groove base, at least one bead, arranged beneath the blade airfoil, for imparting a pressing action, and in the longitudinal direction of the retaining groove, only part of the blade root which the element presses against is covered.

Claims

1. A blade arrangement, comprising: a blade carrier and a holding groove which is arranged in the blade carrier and which has on its side walls longitudinally extending projections for the formation of undercuts, and in which a number of blades for forming a blade ring of a turbomachine are inserted, each blade having an airfoil and a blade root for engaging into the undercuts and being pressed against the projections by a plate-shaped element arranged between a blade root underside and a groove bottom of the holding groove, said plate-shaped element having at least one bead, wherein each element is covered in a longitudinal direction of the holding groove only partially by the blade root pressed by said element and wherein an intermediate piece is inserted in the holding groove between two blades and is pressed against the projections by a part of the element which is not covered by the blade root.

2. The blade arrangement as claimed in claim 1, wherein the element presses the respective intermediate piece against the projections with lower force than it presses the respective blade root against the projections.

3. The blade arrangement as claimed in claim 2, wherein a part of the element which is covered by the blade root is designed to be partially more rigid than the part of the respective element which is not covered by the blade root.

4. The blade arrangement as claimed in claim 1, wherein a part of the element which is not covered by the respective blade root has at least one orifice for demounting.

5. The blade arrangement as claimed in claim 1, wherein a longitudinally extending groove is arranged in the groove bottom of the holding groove or in the blade root underside.

6. The blade arrangement as claimed in claim 1, wherein the element has, in a projection, an outer contour which is substantially rectangular.

7. The blade arrangement as claimed in claim 6, wherein at least one longitudinal edge of the element is angled and bears, prestressed, against the blade roots shaped correspondingly to it.

8. The blade arrangement as claimed in claim 7, wherein at least one longitudinal edge of the element is angled and bears, prestressed, against the blade root shaped correspondingly to it and against the intermediate piece shaped correspondingly to it.

9. The blade arrangement as claimed in claim 6, wherein at least one further bead is provided at at least one margin of the element.

10. The blade arrangement as claimed in claim 1, wherein the element has a wall thickness (s) and the bead has a cross section comprising a bead width (b) and also two convex portions (X) with a radius (R2) and a concave portion (V), arranged between them, with a radius (R1), with a chord length (a), to which the following applies: R1>1.5*s, 3*R2>R1<0.7*R2 and 10*b to 1.7*b>a.

11. The blade arrangement as claimed in claim 1, wherein the bead is configured as a multiple bead.

12. The blade arrangement as claimed in claim 11, wherein the multiple bead comprises an inner bead which is established in at least one outer bead at least partially surrounding the inner bead.

13. An axial compressor for a gas turbine, with a moving blade ring and/or a guide blade ring designed as a blade arrangement as claimed in claim 1.

14. The blade arrangement as claimed in claim 1, wherein the element has a wall thickness (s) and the bead has a cross section comprising a bead width (b) and also two convex portions (X) with a radius (R2) and a concave portion (V), arranged between them, with a radius (R1), with a chord length (a), to which the following applies: R1>5*s, 3*R2<R1 and a<0.9*b.

15. The blade arrangement as claimed in claim 1, wherein a thickness of the element is smaller than a gap between the blade root underside and the groove bottom and wherein the bead is configured such that a height of the element at the bead is beyond the gap so that the blade root is pressed against the projections.

16. The blade arrangement as claimed in claim 15, wherein the bead has a cross section comprising a bead width (b) and also two convex portions (X) with a radius (R2) and a concave portion (V), arranged between them, with a radius (R1), with a chord length (a).

17. The blade arrangement as claimed in claim 16, to which at least one of the following applies: R1>5*s, 3*R2<R1 and a<0.9*b.

18. The blade arrangement as claimed in claim 1, wherein the elements are arranged centrally below respective blades.

19. The blade arrangement as claimed in claim 18, wherein two adjacent elements include opposite ends positioned below the intermediate piece positioned between the two adjacent elements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail in the following figure description by means of several exemplary embodiments which do not restrict the invention. Further features and further advantages are in this case indicated. In these figures:

(2) FIG. 1 shows a partial longitudinal section through a gas turbine,

(3) FIG. 2 shows a top view of a detail of a blade arrangement according to a first refinement,

(4) FIG. 3 shows a cross section through the blade arrangement according to FIG. 2 along the sectional line III-III,

(5) FIG. 4 shows the longitudinal section through the detail of the blade arrangement according to FIG. 2 along the sectional line IV-IV,

(6) FIG. 5, FIG. 6 show the cross sections through a blade arrangement, similar to the sectional line IV-IV, for a second and a third refinement,

(7) FIG. 7 shows a top view of a portion of a blade arrangement according to a fourth refinement (without intermediate pieces),

(8) FIG. 8, FIG. 9 show two variants of the fourth refinement according to FIG. 7 in cross section along the sectional line III-III,

(9) FIG. 10 shows a top view of a portion of a blade arrangement according to a fifth refinement (without intermediate pieces),

(10) FIG. 11, FIG. 12 show two variants of the fifth refinement according to FIG. 7 in cross section along the sectional line III-III,

(11) FIG. 13 shows a force/elasticity graph,

(12) FIG. 14, FIG. 15 show the cross section through an element having different geometries of beads, and

(13) FIG. 16 shows the cross section through a bead geometry in the form of a double bead.

DETAILED DESCRIPTION OF INVENTION

(14) Identical features are given the same reference symbols in the figures.

(15) FIG. 1 shows a stationary gas turbine 10 in a partial longitudinal section. The gas turbine 10 has inside it a rotor 14 which is rotationally mounted about an axis of rotation 12 and which is also designated as a turbine rotor. An intake casing 16, an axial turbocompressor 18, a toroidal annular combustion chamber 20 with a plurality of burners 22 arranged rotationally symmetrically to one another, a turbine unit 24 and an exhaust gas casing 26 succeed one another along the rotor 14.

(16) The axial turbocompressor 18 comprises an annularly designed compressor duct with compressor stages succeeding one another in cascade in the latter and composed of moving blade and guide blade rings. The moving blades 27 arranged on the rotor 14 lie with their freely ending airfoil tips 29 opposite an outer duct wall 42 of the compressor duct. Guide blades 25 likewise project therein and are secured to the outer duct wall 42 or to a compressor guide blade carrier. The compressor duct issues via a compressor outlet diffuser 36 in a plenum 38. Provided in the latter is the angular combustion chamber 20 with its combustion space 28 which communicates with an annular hot gas duct 30 of the turbine unit 24. Four turbine stages 32 connected in series are arranged in the turbine unit 24. A generator or a working machine (not illustrated in either case) is coupled to the rotor 14.

(17) When the gas turbine 10 is in operation, the axial turbocompressor 18 sucks in through the intake casing 16 ambient air 34 as the medium to be compressed and compresses this ambient air. The compressed air is routed through the compressor outlet diffuser 36 into the plenum 38, from where it flows into the burners 22. Fuel also passes via the burners 22 into the combustion space 28. The fuel is burnt there, with the addition of the compressed air, to form a hot gas M. The hot gas M subsequently flows into the hot gas duct 30 where it expands, so as to perform work, at the turbine blades of the turbine unit 24. The energy meanwhile released is absorbed by the rotor 14 and is utilized, on the one hand, for driving the axial turbocompressor 18 and, on the other hand, for driving a working machine or electric generator.

(18) FIG. 2 shows a top view of a detail of a blade arrangement 40 in which only two blades 25, 27 with an intermediate piece 44 established between them and two elements 46 arranged beneath them are illustrated diagrammatically. The blades 25, 27 comprise a diagrammatically indicated airfoil 48 and also a blade root 50. The top view is in the radial direction of the gas turbine 10, that is to say from the airfoil in the direction of the blade root 50. The blade carrier and a holding groove arranged in the carrier are not illustrated in FIG. 2. The elements 46 have a rectangular outer contour and are of plate-shaped design. They are also designated colloquially as sheet-like. In the first exemplary embodiment (FIG. 2), the blade roots 50 and the blades 25, 27 of the blade arrangement are arranged obliquely with respect to a longitudinal extent of the holding groove or of a circumferential direction U. This positioning is typical of moving blades.

(19) Each element 46 has two beads 52 and in each case two orifices 54. The elements 46 are as long in the circumferential direction U as the blade root 50 and intermediate piece 44 are together. However, the elements 46 are arranged centrally below the respective blade 25, 27, so that two adjacent elements 46 terminate centrally in each case with their opposite ends below the intermediate pieces 44.

(20) FIG. 3 shows the cross section along the sectional line III-III through the blade root 50 of the blade 25, 27 and a blade carrier 56. The airfoil is not illustrated in FIG. 3 (nor in FIGS. 5, 6, 8, 9, 11 and 12). A holding groove 58, in which the blades 25, 27, in particular the blade roots 50 of the blades 25, 27, are inserted with a form fit, extends in the blade carrier 56. To make the form fits, the side walls 60 of the holding grooves 58 have longitudinally extending projections 62 so as to form undercuts 64. Correspondingly formed hammer-shaped root regions 66 engage into the undercut 64.

(21) The element 46 is braced between a blade root underside 68 and a groove bottom 70 of the holding groove 58. Moreover, a further demounting groove 72 extending along the holding groove 58 is provided in the groove bottom 70. The further groove 72 serves for access for a demounting tool, for example a sliding hammer.

(22) The wall thickness S of the element 46 (FIG. 14) is smaller than the gap dimension between the blade root underside 68 and groove bottom 70. The beads 52 produced in the element 46 by deep-drawing or by pressing in increase the height H of the element 46 beyond the gap dimension, so that the blade root 50 is pressed against the projections 62. This results in an unequivocal defined position of the blades 25, 27 in the holding groove 58.

(23) FIG. 4 shows the longitudinal section through the refinement according to FIG. 2 along the sectional line IV-IV. The embodiment, illustrated in FIGS. 2, 3 and 4, of the blade arrangement 40 is a detail of a moving blade ring of a compressor 12 of the gas turbine 10. The blade carrier 56 is accordingly formed by a rotor disk and the blades 25, 27 are designed as moving blades.

(24) The elements 46 are essentially planar and therefore do not follow the curvature of the holding groove 58. On account of this, the elements 46, with their middle region in which the beads 52 are arranged, press the blade root underside 68 and groove bottom 70 apart from one another with greater force. Those portions of the element 46 which are adjacent to the transverse edges 82, because of the planar configuration of the elements 46 and the curved holding groove 58, then bear with lower force resiliently against the undersides of the intermediate pieces 44. Consequently, the element 46 presses the intermediate pieces 44 and the blades 25, 27 against the projections 62 of the holding groove 58 with forces of different magnitude on account of locally different rigidities.

(25) A second refinement of a blade arrangement 40 is illustrated in FIG. 5. FIG. 5 shows essentially the cross section according to FIG. 3. In this case, features identical in FIG. 5 to FIG. 3 are given identical reference symbols. To describe FIG. 5, reference is made as far as possible to the description of FIG. 3. According to the second refinement, however, the longitudinal edges 74 of the element 46 are bent round toward the groove orifice of the holding groove 58. The bent-round longitudinal edges 74 (cf. FIG. 2) bear, prestressed, against chamfers 76 arranged on the underside of the blade root. Since the intermediate pieces 44 are designed in a similar way to the blade roots 50 of the blades 25, 27, those regions of the longitudinal edges 74 of the element 46 which are established below the intermediate piece 44 also bear, prestressed, against corresponding chamfers. The bent-round longitudinal edges 74 of the element 46 and the prestressed bearing of the elements 46 against the blade roots 50 or intermediate pieces 44 give rise to a nonpositive coupling of the adjacent components, namely the blade root 50 and intermediate piece 44, which improves their orientation and reduces contact wear between the components.

(26) A third refinement of a blade arrangement 40 is illustrated diagrammatically in FIG. 6. FIG. 6, too, shows as far as possible the same cross section as FIG. 3, and therefore features identical in FIG. 6 to FIG. 3 are given the same reference symbols. In contrast to the refinement according to FIG. 3, the third refinement according to FIG. 6 has on the blade root underside 68 a comparatively wide groove 78 which, however, is provided with low depth, and which extends in the longitudinal direction of the holding groove 58. The groove 78 serves for receiving the element 46, and therefore the groove depth of the groove 78 corresponds essentially to the wall thickness S of the element 46. The longitudinal edges 74 of the element 46 (cf. FIG. 2) bear against the inclined side walls of the groove 78. To the same extent as in the case of the blade root 50, according to the third refinement, in the case of the intermediate pieces 44, a groove 78 arranged on their underside is also provided, so that the longitudinal edges 74 of the element 46 also bear against the side walls of the groove 78 arranged on the intermediate piece 44.

(27) By the elements 46 bearing simultaneously against the blade 25, 27 and the intermediate piece 44, coupling of the adjacent blade ring components is brought about, thus reducing wear, in particular contact wear. Both in the second refinement according to FIG. 5 and in the third refinement according to FIG. 6 of the blade arrangement 40 according to the invention, the blades are designed as moving blades 27.

(28) FIGS. 8 and 9 show, in a similar way to the cross section according to FIG. 3, a cross section through a blade arrangement 40 according to a fourth refinement. In contrast to the abovementioned refinements, the arrangements shown in FIGS. 7, 8 and 9 are configured as guide blade rings, not as moving blade rings. The cross-sectional contours of the holding groove 58 and of the blade root 50 differ from one another only slightly as a result. A further difference from the refinements described hitherto is that no intermediate pieces 44 are provided between adjacent guide blades 25. As shown in the illustration according to FIG. 7, therefore, the blades 25 bear one against the other over their area and without any positioning of the blade roots 50. In this case, the elements 46 are arranged in each case by half under a pair of adjacent blades 25. As a result of this, the stiffening beads 52 are also not established in the inner region in the element 46, but instead at two opposite transverse edges 82 of the elements 46. Otherwise, the first variant of the fourth refinement according to FIG. 8 is designed in a similar way to the second refinement according to FIG. 5 with the angled longitudinal edges 74 of the element 46. A second variant of the fourth refinement, shown in FIG. 9, corresponds structurally essentially to the third refinement according to FIG. 6 in which the element 46 is for a large part countersunk into a groove 78 arranged on the blade root underside 68.

(29) A fifth refinement of the blade arrangement 40 is illustrated in a top view according to FIG. 10, of which two variants are shown, a first in cross section in FIG. 11 and a second in cross section in FIG. 12. The fifth refinement illustrated in FIG. 5 is based essentially on the first refinement illustrated in FIG. 2. However, in addition to the beads 52 arranged in the inner region of the element 46, further beads 86 are provided at the transverse edges 82 in a similar way to the fourth refinement shown in FIG. 7. By the further beads 86 being used at the margin, the element 46 can reliably be prevented from bending out of shape or collapsing when it is being driven in between the blade route underside 68 and groove bottom 70. At the same time, the further beads 86 engage either into the demounting groove 72 (FIG. 11) or into a groove 78 (FIG. 12), arranged on the underside of the blade root, for the alignment or guidance of the elements 46.

(30) FIGS. 14 and 15 show in each case a refinement of the element 46 in cross section along the sectional line III-III from FIG. 2. In contrast to the element 46 illustrated in FIG. 2, FIGS. 14, 15 illustrate only one bead 52, not two beads 52. Each bead 52 comprises two convexly curved portions X and a concave portion V arranged between them. The convex portions X have in each case a radius R2 and the concave portions V a radius R1. Moreover, the concave portion V has a chord length a, the bead 52 comprising a bead width b. In order to obtain the bead 52 itself with a region of plastic deformation for a higher load force and a higher spring constant and for a region having elastic deformation with a low spring constant, two embodiments of the element are proposed. The first embodiment is achieved when

(31) R1>1.5*S, 3*R2>R1>0.7*R2 and 10*b to 1.7*b>a.

(32) For example, the parameters may have the following dimensions:

(33) R1=2 mm; R2=2 mm; S=1 mm; a=3.5 mm and b=10 mm.

(34) The second refinement of an element 46 provides for

(35) R1>5*S,

(36) 3*R2<R1 and

(37) a<0.9*b.

(38) For example, the parameters may have the following dimensions:

(39) R1=20 mm; R2=2 mm; S=1 mm; a=6 mm and b=10 mm.

(40) With the aid of the refinement shown, it is possible that the portion V represents the region of plastic deformation with a higher load force and higher spring constant and the portions X represent the regions for elastic deformation with a low spring constant, as also illustrated in FIG. 13.

(41) FIG. 16 shows the cross section through a special bead geometry. The special bead geometry is a multiple bead 55 in which an inner bead 55i is surrounded by one or more beads 55a. The beads 55i, 55a of the multiple bead 55 are arranged, virtually stacked or hierarchically, with a common center M. The multiple bead 55 shown in FIG. 16 is a twofold bead, also called a double bead. Double beads mean in this case that a basically concave portion Va of a first (then outer) bead 55a has established in it a second (then inner) bead 55i. This bead combination has further-increased elasticity, as compared with the abovementioned geometries, which may be designated as single beads, with the result that higher manufacturing tolerances can be permitted for the blade roots 50, if appropriate the intermediate pieces 44 and the holding groove 58. Dimensions for the bead geometry according to FIG. 16 are then, for example:

(42) R20=20 mm; R1.2=2 mm; R2=2 mm; ba=11 mm, aa=bi=7.4 mm, R3=2 mm and ai=3.2 mm.

(43) The invention relates overall to a blade arrangement 40 with a blade carrier 56 and with a holding groove 58 which is arranged therein and which has on its side walls 60 longitudinally extending projections 62 for the formation of undercuts 64, and in which a number of blades 25, 27 for forming a blade ring of a turbomachine are inserted, each blade 25, 27 having in addition to an airfoil 48, for fastening, a hammer-shaped blade root 50 engaging into the undercuts 64 and being pressed against the projections 62 by an element 46 arranged between a blade root underside 68 and a groove bottom 70 of the holding groove 58. In order to specify especially secure, reliable, long-lived and low-wear fastening, which makes especially simple mounting and demounting possible, there is provision whereby each element 46 is of plate-shaped design, has, in the projection of the airfoil 48 in the direction of the groove bottom 70, at least one bead 52, arranged below the airfoil 48, for pressing down and is covered in the longitudinal direction of the holding groove 58 only partially by the blade root 50 pressed down by said element.