FR3076570A1 - MONOBLOC AUBING DISC OF A BLOWER COMPRISING ORIFICES IN THE RIM - Google Patents

Abstract

The invention relates to a monobloc blisk (1) of a stage of a turbomachine, in particular a blower, comprising a hub (2) comprising a rim (3). At least one orifice (10) is formed in the rim (3) of the hub (2) to loosen the rim (3) locally.

Description

FIELD OF THE INVENTION The invention relates generally to gas turbine engines, and more particularly a fan disc of such a turbojet engine type, this disc being of the bladed monobloc type, that is to say that it comprises a hub and vanes forming a single inseparable part.

TECHNOLOGICAL BACKGROUND

A double-flow turbomachine generally comprises, from upstream to downstream in the direction of gas flow, a fan, an annular space for primary flow and an annular space for secondary flow. The mass of air sucked in by the fan is therefore divided into a primary flow and a secondary flow which is concentric with the primary flow.

The primary flow passes through a primary body comprising one or more stages of compressors, for example a low pressure compressor and a high pressure compressor, a combustion chamber, one or more stages of turbines, for example a high pressure turbine and a low pressure turbine , and a gas exhaust nozzle.

In a manner known per se, the blades of the blower are fixed on a disc, called a blower disc, which is driven by the turbine stages by means of a motor shaft. The fan blades can be attached and fixed to the fan disc. As a variant, the fan blades can be formed integrally and in one piece with a hub, forming with it a single and inseparable piece called bladed monobloc disc (or DAM). The hub of this one-piece bladed disc is connected to the fan blades at their foot.

In general, the problems of floating fan blades involve deformation waves and natural mode couplings of the blades as well as contributions from other parts that can lead to the structure breaking. However, the passage from a disc on which the blades are attached to a one-piece bladed disc facilitates the propagation of the waves: the excitations and vibrations generated by aerodynamics are indeed no longer attenuated by friction between parts since the disc becomes monolithic .

In addition, it is generally when the blades deform in phase in the same proper mode that the overall damping (aerodynamic and mechanical) is the most critical and can become negative. The operation of the disc is then conducive to the establishment of floating.

A phase shift or a heterogeneity of modes between the different blades of the same bladed disc breaks this cyclical symmetry and prevents the floating from settling in a durable way. It has therefore been proposed to “tuner” a monobloc bladed disc by producing, for the same disc, vanes with different geometries in order to break this symmetry and find the margin relative to this asynchronous vibrational phenomenon. However, these changes in geometry are harmful to the aerodynamics of the bladed disc since they lead to different channels depending on the neighboring blades. It is therefore difficult to obtain a level of performance similar to a perfectly homogeneous case. This is also harmful for the acoustics of the blower (originating from differences in blade geometries on the same rotor) while switching to the bladed one-piece disc initially improves the acoustics.

SUMMARY OF THE INVENTION

An objective of the invention is therefore to propose a one-piece bladed disc in which the installation of floats is limited, without however penalizing the aerodynamics and / or the acoustics of the blading.

For this, the invention provides a one-piece bladed disc of a stage of a turbomachine, in particular of a fan, comprising: - a hub comprising a rim and a platform, said platform extending radially outside the rim and being configured to define an internal flow stream of a gas in the turbomachine, - a plurality of blades, said blades extending radially from the platform and being formed integrally and in one piece with said platform and - at least one orifice, formed in the rim of the hub in order to locally soften the rim.

Some preferred but non-limiting characteristics of the one-piece bladed disc described above are the following, taken individually or in combination: - the one-piece bladed disc comprises a series of holes formed in the rim, the holes being separated two by two by a distance at least equal to a distance separating two adjacent blades. - At least two of the orifices have different geometry and / or dimensions. - all or part of the orifices are through. - the rim has an upstream face and a downstream face, all or part of the orifices opening into at least one of the faces. - The orifice (s) have a polygonal, circular, oval, elliptical or any shape. - The one-piece bladed disc further comprises at least one plug inserted into the or at least one of the orifices of the rim, said plug being made of an elastomeric material. - all or part of the orifices house a plug. - The one-piece bladed disc comprises N fan blades, and in which at most N orifices are formed in the rim, preferably at most N / 2 orifices.

According to a second aspect, the invention also proposes a fan of a turbomachine, characterized in that it comprises a one-piece bladed disc as described above.

BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics, objects and advantages of the present invention will appear better on reading the detailed description which follows, and with regard to the single appended figure given by way of nonlimiting examples and on which one shows an embodiment of a sector of a one-piece bladed disc according to the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

A sector of a one-piece bladed disc 1 in accordance with one embodiment has been partially shown in the accompanying figures. Such a one-piece bladed disc 1 can be used in any rotating or fixed part of a turbomachine, and more particularly for the rotating part of a fan.

The disc 1 comprises a hub 2 comprising a rim 3 and a platform 7. The platform 7 extends radially outside the rim 3 and is configured to define an internal stream of the gas flow in the turbomachine. The rim 3 has an upstream face 4 and a downstream face 5, the upstream and downstream being defined in the direction of flow of the gases in the turbomachine.

The disc 1 further comprises a plurality of vanes 7 extending radially from the platform 7. Each vane 7 is formed integrally and in one piece with the platform 7 and comprises a foot 8 connected to the platform 7 and an opposite head at the foot 8. The blades 7 have an identical shape and dimensions two by two.

Here, the disc 1 is shown only on a sector in the single figure while the disc is unitary, being annular over a complete circumference coming from forging and then machining. It is possible to consider that the disc is sectored so that the hub 2 is formed of several sectors fixed together by constituting the disc 1 bladed in one piece.

In order to tune the one-piece bladed disc 1, at least one orifice 10 is formed in the rim 3 of the hub 2, which makes it possible to loosen the rim 3 locally and to limit the installation of the floating on the one-piece bladed disc 1. By softening, it will be understood here that the mechanical characteristic of the stiffness of the disc provided with at least one orifice is lessened. The realization of the orifice 10 leads to a frequency detuning beneficial for friction problems since each sector has vanes 7 of identical shape and size but has a rim 3 whose shape is different in the area adjacent to the orifice 10 than in the rest of the rim 3. This breaking of the cyclic symmetry thus makes it possible to reduce the risks of the appearance of floating. The orifice 10 can be through and open into the upstream face 4 and into the downstream face 5 of the rim 3, open only in one of the faces or open up in none of the faces. These different configurations thus make it possible to play on the depth and the dimensions (between the upstream 4 and downstream 5 faces of the rim 3) of the orifices 10.

In a first embodiment, a single orifice 10 is formed in the rim 3 without opening into the platform 6. The position, the shape and the dimensions of the orifice are then chosen so as not to create an unbalance while acting on the stiffness of the disc 1.

In a second embodiment, at least two orifices 10 are formed in the rim 3. Preferably, the orifices 10 are separated in pairs by a distance at least equal to a distance separating two adjacent vanes 7. For example, for a one-piece bladed disc 1 comprising N blades 7, the rim 3 may comprise between 1 and N orifices 10, preferably between 1 and N / 2 orifices 10.

The shape and dimensions of the orifices 10 are chosen as a function of the frequency and geometric deviations necessary to break the number-to-diameter structure by creating a phase shift and a geometric dispersion making it more difficult to appropriate the spatial appropriation, which limits the installation. floating in the disc 1 bladed monobloc.

Preferably, the shape of the orifices 10 is chosen so as not to have a sharp edge in order to avoid the incipient fractures.

The radial dimension of each orifice 10 can for example be less than half of the radial extent of the rim of the disc forming the hub under platform (the radial extent of the rim being taken upstream, insofar as this is the most restrictive dimension).

The orifices 10 can also be formed in the upstream face 4 and / or in the downstream face 5 of the rim 3. Preferably, the orifices 10 are formed in the downstream face 5 of the rim 3, the available space being more important considering the disc taper 1.

The orifices 10 can have any geometric shape or a polygonal, circular, oval, elliptical, etc. shape. Preferably, the orifice 10 does not have an angular shape in order to avoid concentrations of stresses at the periphery. If necessary, the outline of the orifices can therefore be rounded at the level of its corners, in particular in the case of orifices of generally polygonal shape.

In one embodiment, two adjacent orifices 10 have a different shape and / or size. For example, all the orifices 10 can have a different shape and / or size. As a variant, several orifices 10 may have the same shape and the same dimension: their distribution in the rim 3 is then non-symmetrical or regular in order to obtain the phase shift and the geometric dispersion making it possible to limit the installation of the floating. By way of nonlimiting example, for example illustrated in FIG. 1 is a one-piece bladed disc sector 1 in which three orifices 10 are formed, said orifices 10 being each positioned between two adjacent vanes 7 and having respectively a circular shape, a square shape with very rounded corners and a square shape with slightly rounded corners.

Advantageously, the orifices are punctual in the disc while being hollow in the mass of the latter, for the benefit of minimizing the impact on its overall mechanical strength. Furthermore, the orifices 10 are not radially open but their pattern is contained in the frontal extent (upstream or downstream) of the rim 3, at a distance from the platform 6.

Optionally, the one-piece bladed disc 1 further comprises at least one plug 9 inserted in one of the orifices 10 of the rim 3 in order to modify the frequencies of the sector treated. The plug 9 is made of an elastomeric material in order to mechanically dampen the vibrations (parameter already very greatly reduced in a one-piece bladed disc 1, in comparison with a disc 1 on which the vanes 7 are attached) and to obtain friction margin . Preferably, the elastomeric material will be chosen to have a sufficient stiffness to withstand the centrifugal forces and, where appropriate, a density sufficient to ensure damping.

Preferably, the plug 9 fills the orifice 10 without projecting from the upstream face 4 or from the downstream face 5 of the rim 3.

It will be noted that all or part of the orifices 10 formed in the rim 3 can accommodate a plug 9.

For example, the disk sector 1 illustrated in FIG. 1 comprises a plug 9, which fills the corresponding orifice 10.

Claims (10)

1. One-piece bladed disc (1) of a stage of a turbomachine, in particular of a fan, comprising: - a hub (2) comprising a rim (3) and a platform (6), said platform (6) s 'extending radially outside the rim (3) and being configured to define an internal flow path of a gas in the turbomachine, - a plurality of blades (7), said blades (7) extending radially from the platform (6) and being formed integrally and in one piece with said platform (6), the one-piece bladed disc (1) being characterized in that at least one orifice (10) is formed in the rim (3 ) of the hub (2) in order to locally soften the rim (3). 2. Disc according to claim 1, comprising a series of orifices (10) formed in the rim (3), the orifices (10) being separated in pairs by a distance at least equal to a distance separating two blades (7) adjacent. 3. Disc according to claim 2, wherein at least two of the orifices (10) have a different geometry and / or dimensions. 4. Disc according to one of claims 1 to 3, wherein all or part of the orifices (10) are through. 5. Discs according to one of claims 1 to 3, wherein the rim (3) has an upstream face (4) and a downstream face (5), all or part of the orifices (10) opening into at least one faces (4, 5). 6. Disc according to one of claims 1 to 5, wherein the orifice (s) (10) have a polygonal, circular, oval, elliptical or any shape. 7. Disc according to one of claims 1 to 6, further comprising at least one plug (9) inserted in the or at least one of the holes (10) of the rim (3), said plug (9) being made of an elastomeric material. 8. Disc according to claim 7, wherein all or part of the orifices (10) house a plug (9). 9. Disc according to one of claims 1 to 8, comprising N blades (7) of fans, and in which at most N orifices (10) are formed in the rim (3), preferably at most N / 2 orifices ( 10). 10. Blower of a turbomachine characterized in that it comprises a one-piece bladed disc (1) according to one of claims 1 to 9.