ROTOR WHEEL FOR AN AIRCRAFT TURBOMACHINE

Abstract

A rotor wheel (10) for an aircraft turbomachine, this wheel comprising: - a disk (12) having a main axis (A) and having recesses (14) on its outer periphery, the recesses extending along said axis and each comprising a bottom (14a) and two lateral sides (14b), - blades (22) mounted in the recesses (14) of the disk (12), each of these blades comprising a blade (24) connected by a platform (26) to a foot (28) which is mounted in one of the recesses (14), characterized in that the foot (28) of each of the blades (22) comprises a projecting bulb (42) which is oriented radially inwards and configured to bear radially in a sealed manner against the bottom (14a) of the corresponding recess (14). Figure for the abbreviation: Figure 8

Description

Title of the invention: ROTOR WHEEL FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The present invention relates to a rotor wheel for an aircraft turbomachine. Technical background

[0002] The technical background includes in particular documents FR-A1-2 951 224 and FR-A1-3 049 643.

[0003] A rotor wheel 10, such as that partially illustrated in [Fig. 1], comprises a disk 12 which has a main axis A representing the axis of rotation of the wheel, and which includes pits 14 at its outer periphery.

[0004] The cavities 14 extend along axis A and may be parallel to this axis or inclined with respect to axis A. They are separated from each other by teeth 16 of the disc, these teeth also being called "interblades". The cavities 14 are generally formed by broaching or electrical discharge machining and have a general dovetail or pine tree shape (with one or more lobes). Their axes along axis A are called broaching axes. Each of the cavities 14 has a bottom located between two lateral sides.

[0005] The rotor wheel 10 also includes blades 22 which are mounted in the recesses 14 of the disk 12. Each blade 22 has a blade 24 connected by a platform 26 to a foot 28 which is configured to be mounted by complementary shapes in one of the recesses 14. Each of the teeth 16 of the disk has at its radially external end a vertex 18 covered by the platforms 26 of two adjacent blades 22.

[0006] The foot 28 of each blade 22 has at its radially internal end a lobe 30 of which a first axial end includes a circumferential notch 32 and of which a second axial end, opposite to the first axial end, includes a cleat 33 or hook oriented radially inwards (cf. [Fig.2]).

[0007] The rotor wheel 10 further includes a split annular ring 34 engaged in the notches 32 of the blades and axially pressed against the disc 12.

[0008] Figures 3 to 7 are detailed views of a rotor wheel 10 of the prior art.

[0009] These figures show that, when the rod 34 is engaged in the notches 32 of the blades, these blades 22 are designed to bear against the disk 12 by means of their lugs 33. The rod 34 bears axially against a face 12a of the disk 12, and the The cleats 33 bear axially on the opposite face 12b of the disc. In theory, this axial support is ensured by the mounting of the ring 34.

[0010] Each of the blades 22 is mounted on the outer periphery of the disk 12 by means of a sliding joint. Once mounted, the blades 22 must be held axially on the disk 12, and the retaining ring 34 ensures this immobilization. It is also important to ensure that this joint is sealed, in particular to prevent gases from the rotor stream from flowing through it.

[0011] In the assembly described above, the axial support of the cleats 33 of the blades 22 on the Disc 12 ensures a seal in this area between the blades 22 and the cells 14 of the disc. This seal is axial in that it is ensured by support in the axial direction, that is to say parallel to the axis A of the wheel or to the spindle axes of the cells.

[0012] However, in practice, due to assembly clearances and thermomechanical and vibratory stresses during operation, the blades 22 can move axially (on the order of a few tenths of a millimeter) and their stops 33 may no longer be in axial support on the disk 12, even if this support is favored by the flow of gases in the vein.

[0013] Axial sealing in the region of the lug 33 of each blade 22 is thus no longer ensured. This phenomenon is accentuated by the connections 38 of the sides 14b to the bottom 14a of the cells 14, and by the connections 40 of the lug 33 to the sides of the foot, which are designed to ensure good axial support of the lug 33 against the disc 12.

[0014] Figures 6 and 7 illustrate the leaks in the slide joint in this area. These leaks introduce a bias in the initial air system model, and they induce a decrease in rotor efficiency and a temperature difference at the top of the disk.

[0015] The present invention proposes a solution to this problem, which is simple, effective and economical. Summary of the invention

[0016] The present invention relates to a rotor wheel for an aircraft turbomachine, this wheel comprising:

[0017] - a disc having a main axis and having alveoli on its outer periphery, the cells extending along said axis and each comprising a base and two lateral sides,

[0018] - blades mounted in the recesses of the disk, each of these blades comprising a blade connected by a platform to a foot which is configured to be mounted by complementary shapes in one of the cells, the foot of each of the blades having at its radially internal end a lobe whose first axial end includes a circumferential notch and whose second axial end, opposite the first end, includes a cleat oriented radially inwards and configured to bear axially against a first face of the disk, and

[0019] - a split annular ring engaged in the notches of the blades and axially pressed against a second face of the disk, the second face being opposite the first face,

[0020] characterized in that the lobe of the foot of each of the blades comprises, between said first and second ends, a projecting bulb which is oriented radially inwards and configured to be in radial surface support on the bottom of the corresponding cavity.

[0021] According to the invention, although the lug on each blade can provide a seal in this area by axial support on the disc, the additional bulb at the base of each blade is also configured to bear radially on the bottom of the base's receiving recess in order to provide a seal in this area by this radial support. In operation, regardless of the axial position of the blade relative to the disc, and even if the lug is not bearing axially on the disc, the bulb remains in radial contact with the bottom of the recess, which maintains and guarantees the seal in this area.

[0022] In this application, "radial support" means that two elements are radially supported on each other or that these two elements are fitted to each other in the radial direction. "Fitted" or "fit" means the absence of play in the radial direction between these elements. During operation, centrifugal forces apply radial outward stress to the blades, which may no longer be radially supported on the bottoms of the cells but be fitted to them.

[0023] In the present application, "surface support" or "watertight support" means the fact that an element or surface is supported on another element or surface with at least three points of contact, this support being capable of providing a seal between these elements or surfaces.

[0024] The wheel according to the invention may also have one or more of the following characteristics, taken alone or in combination with each other:

[0025] - said bulb has in cross-section a shape complementary to a cross-section transverse of a part of the alveolus in which it is located.

[0026] - said bulb has an axial position Pbuibesur said lobe, measured along the axis and from the face of the disc on which said paddle stop rests, such as:

[0027] [Math.l] (P / L) J < bulb < (P / L) 2

[0028] with

[0029] (p / L) greater than or equal to 0.1, and

[0030] (p / L)2 less than or equal to 0.9, and preferably less than or equal to 0.3,

[0031] - said bulb has an axial position Pbuibe such that it is closer to said first end, that of the said second end,

[0032] - said bulb has an axial length Lbuibe such that:

[0033] [Math.2] 0.1 X Lgroch disk < LBuibe< 0.9 X LBroch disk

[0034] with

[0035] LBroch disk the spindle length of the disk which is equal to the maximum length of a pit,

[0036] - said bulb has a cross-sectional area SBuibe such that:

[0037] [Math.3] 0.01 X (Total S Disc' foot) < ^Bulbe^ 9'9 (Total S Disc' ^PaleFoot)

[0038] with

[0039] Stotaie_Disc = Total area of ​​a cross-section of a cell of the disc, and

[0040] Foot spacing = Cutting a cross-section of the foot outside the bulb without passing through the bulb,

[0041] - said bulb comprises two radial faces, respectively upstream and downstream, which are connected to each other by a convex curved face complementary to the bottom of the alveolus,

[0042] - the downstream radial face of the bulb is connected by an inclined face to said notch, and

[0043] — the blade of each blade includes a heel.

[0044] The present invention also relates to a turbomachine, in particular for aircraft, comprising at least one rotor wheel as described above. Brief description of the figures

[0045] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings in which:

[0046] [Fig-1] [Fig. 1] is a partial schematic perspective view of a rotor wheel of an aircraft turbomachine;

[0047] [Fig.la] [Fig.la] is a larger scale view of part of [Fig.l];

[0048] [Fig.2] [Fig.2] is a partial schematic perspective view of a turbine blade rotor;

[0049] [Fig.3] [Fig.3] is a partial schematic perspective and axial section view of a rotor wheel, the cut passing through the foot of a blade;

[0050] [Fig.4] [Fig.4] is a partial schematic perspective view of a wheel rotor, seen from one side upstream here;

[0051] [Fig. 5] [Fig. 5] is a partial schematic perspective view of a wheel rotor, seen from a downstream side here;

[0052] [Fig.6] [Fig.6] is a partial schematic perspective and cross-sectional view of a rotor wheel, and shows the passage sections around the bottom of a cavity in the disc;

[0053] [Fig.7] [Fig.7] is a partial schematic perspective view of the section of passage between a cleat on the foot of a paddle and the disc;

[0054] [Fig.8] [Fig.8] is a schematic perspective view of a blade for a rotor wheel according to the invention;

[0055] [Fig.9] [Fig.9] is a schematic perspective and axial section view of the rotor wheel including the blade of the [Fig.8];

[0056] [Fig. 10] [Fig. 10] is a larger scale view of part of [Fig. 9];

[0057] [Fig. 11] [Fig. 11] is a partial schematic perspective view of a disk and shows the area of ​​a cross-section of one of its alveoli;

[0058] [Fig. 12] [Fig. 12] is a partial schematic perspective view of a disk and shows the cross-sectional areas of the foot of a blade housed in one of the alveoli of the disc; and

[0059] [Fig. 13] [Fig. 13] is a partial schematic perspective view of a rotor wheel and shows a vanishing line between the root of a blade and a recess in the disc. Detailed description of the invention

[0060] Figures 1 to 7 have been described above and illustrate the context of the invention, one embodiment of which is illustrated in Figures 8 to 13.

[0061] The invention relates to a rotor wheel 10 which is partially represented in Figures 11 and 13. This wheel 10 comprises a disk 12 which, as in [Fig. 1], has a main axis A (not visible) representing the axis of rotation of the wheel.

[0062] The disc 12 comprises sockets 14 on its outer periphery. The sockets 14 extend along axis A and are separated from each other by teeth 16. The sockets 14 are generally formed by broaching or electrical discharge machining (EDM) and have a general dovetail or pine tree shape (with one or more lobes). Each of the sockets 14 has a bottom 14a situated between two lateral sides 14b.

[0063] Each of the teeth 16 of the disc has at its radially external end a vertex 18.

[0064] The rotor wheel 10 also includes blades 22 which are mounted in the recesses 14 of the disc 12. Each blade 22 has a blade 24 connected by a platform 26 to a foot 28 which is configured to be mounted by complementary shapes in one of the recesses 14. Each blade 22 may further include a heel.

[0065] The foot 28 of each blade 22 has at its radially internal end a lobe 30, the first axial end of which, here downstream, includes a notch 32 circumferential and of which a second axial end, here upstream, includes a cleat 33 or hook oriented radially inwards (cf. [Fig.8]).

[0066] The rotor wheel 10 further includes a split annular ring 34 engaged in the notches 32 of the blades and axially pressed against the disk 12, and in particular against a downstream face 12a of the disk 12.

[0067] When the ring 34 is engaged in the notches 32 of the blades, these blades 22 are designed to bear by means of their own lugs 33 against an upstream face 12b of the disk 12. The ring 34 bears axially against a face 12a of the disk 12, and the lugs 33 bear axially against the opposite face 12b of the disk. In theory, this axial support is ensured by the mounting of the ring 34.

[0068] Each of the blades 22 is mounted on the outer periphery of the disk 12 by means of a sliding joint. Once mounted, the blades 22 must be held axially on the disk 12, and the retaining ring 34 ensures this immobilization. It is also important to ensure that this joint is sealed, in particular to prevent gases from the rotor stream from flowing through it.

[0069] According to the invention, this sealing is ensured even if the blade 22 moves axially during operation depending on the mounting clearances, that is, regardless of the axial position of the blade 22 in the corresponding cavity 14. This is made possible by the fact that the lobe 30 of the foot 28 of each of the blades 22 includes, between the notch 32 and the lug 33, a projecting bulb 42 which is oriented radially inwards and configured to be in radially sealed support or adjusted in a radial direction on the bottom 14a of the corresponding cavity 14.

[0070] As can be seen in particular in figures 8 and 9, the bulb 42 preferably has in cross-section a shape complementary to a cross-section of a part of the alveolus 14 in which it is located.

[0071] In the example shown, the bulb 42 comprises an upstream radial face 42a and a downstream radial face 42b. These faces 42a, 42b are connected to each other by a concave curved surface 42c complementary to the bottom 14a of the cavity 14 and radially supported or fitted to this bottom 14.

[0072] The downstream face 42b is connected to the notch 32 by a face 42d which is inclined here in the example shown.

[0073] Figure 10 illustrates the axial position of the bulb 42 on the foot 26 or the lobe 30, measured along axis A and from face 12b of the disk 12 on which the lug 33 or blade hook rests. The axial position Pbuibe is such that:

[0074] [Math.l] (P / L) J < bulb < (P / L) 2

[0075] with

[0076] (p / L) greater than or equal to 0.1, and

[0077] (pÆ)2 less than or equal to 0.9, and preferably less than or equal to 0.3.

[0078] In the example shown, the bulb 42 has an axial position Pbuibe such that it is closer to said first end of the foot having the notch 32, than to said second end of the foot having the cleat 33 or hook.

[0079] The bulb 42 has an axial length Lbuibe such that:

[0080] [Math.2] 0.1 Lsroch disk LBuibe< 0.9 X Lgroch disk

[0081] with

[0082] LBroch disk the spindle length of the disk which is equal to the maximum length of a pit 14.

[0083] Figures 11 and 12 show that the bulb 42 has a cross-sectional area SBuibe such that:

[0084] [Math.3] 0.01 X (Sfofa;e Disc" ^PalePied) < Bulb < 0.9 X (S totalDisk" ^PalePied)

[0085] with

[0086] Stotaie_Disque = the total area of ​​a cross-section of a cavity of the disk ([Fig. 11]), and

[0087] Foot_area = the area of ​​a cross-section of the foot outside the bulb without passing through the bulb ([Fig. 12]).

[0088] The resulting seal is called radial because it is no longer achieved by a flat contact between the lug or hook and the disc. The manufacture of a blade as described above can be carried out as follows: • The machining of the blade's base is carried out by conventional grinding, • The bulb is made using a conventional grinding method, but compared to the rest of the foot, with a grinding wheel of a different shape and a different toolpath due to the interference of shapes in the broaching axis. • The machining of the disc's pits is achieved by broaching or by EDM wire cutting.

Claims

Demands

1. A rotor wheel (10) for an aircraft turbomachine, said wheel comprising: - a disk (12) having a main axis (A) and having recesses (14) on its outer periphery, the recesses extending along said axis and each comprising a bottom (14a) and two lateral sides (14b), - blades (22) mounted in the recesses (14) of the disk (12), each of these blades comprising a blade (24) connected by a platform (26) to a foot (28) which is configured to be mounted by complementary shapes in one of the recesses (14), the foot (28) of each of the blades (22) having at its radially internal end a lobe (30) having a first axial end comprising a circumferential notch (32) and having a second axial end, opposite to the first end, comprising a lug (33) oriented radially inwards and configured to bear axially on a first face (12b) of the disk (12),and - a split annular ring (34) engaged in the notches (32) of the blades (22) and axially pressed against a second face (12a) of the disk, the second face (12a) being opposite the first face (12b), characterized in that the lobe (30) of the foot (28) of each of the blades (22) comprises, between said first and second ends, a projecting bulb (42) which is oriented radially inwards and configured to bear radially on the surface of the bottom (14a) of the corresponding cavity (14), in which said bulb (42) comprises two radial faces, respectively upstream (42a) and downstream (42b), which are connected to each other by a curved convex face (42c) complementary to the bottom (14a) of the cavity (14), and in which the downstream radial face (42b) of the bulb (42) is connected by an inclined face (42d) to said notch (32).

2. Wheel (10) according to claim 1, wherein said bulb (42) has in cross section a shape complementary to a cross section of a part of the cavity (14) in which it is located.

3. Wheel (10) according to claim 1 or 2, wherein said bulb (42) has an axial position Pbuibesur said lobe (30), measured along the axis (A) and from the face (12b) of the disc (12) on which said stop (33) of the blade (22) is supported, such that: [Math.l] ( P / L ) i < bulb ( P / l) 2 with (p / L)i greater than or equal to 0.1, and (p / Dh less than or equal to 0.9, and preferably less than or equal to 0.

3.

4. Wheel (10) according to claim 3, wherein said bulb (42) has an axial position Pbuibe such that it is closer to said first end than to said second end.

5. Wheel (10) according to any one of claims 1 to 4, wherein said bulb (42) has an axial length Lbuibe such that: [Math.2] 0.1 X Lfaoch diSqUe< LBuibe <G,ÿ X LBrocb (]iSqUe avec LBroch-disque la longueur de brochage du disque (12) qui est égale à la longueur maximale d’une alvéole (14)

6. Wheel (10) according to any one of claims 1 to 5, wherein said bulb (42) has in cross-section an area SBuibe such that: [Math.3] 0.01 X { _üisque~ SpalePied ) < ^Bulbe < 0.9 [^totals Disc- ^PalePied) with Stotaie_Disque= Total area of ​​a cross-section of a socket (14) of the disc (12), and Spaie_pied = the area of ​​a cross-section of the foot (28) outside the bulb (42) without passing through the bulb.

7. Turbomachine for an aircraft, wherein it comprises at least one wheel (10) according to any one of the preceding claims.

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