FR3102205A1 - Flyweight turbomachine rotor - Google Patents

Abstract

The invention relates to a rotor including a one-piece bladed disc provided with at least one balancing weight (170). The upstream part of the disc platform has a flange (72). The flange (72) extends annularly around said axis (X) and defines, with a radially inner surface (66c) of the platform, at least one said housing (73). The balancing weight (170) is fixed to the flange, cantilevered. Figure to be published with the abstract: Figure 4

Description

Flyweight turbomachine rotor

Technical field of the invention

The present invention relates to a gas turbine engine rotor for an aircraft.

Is specifically concerned with the balancing of such a rotor by the addition of so-called "weights", these weights being mounted on a flange of the rotor.

On certain aircraft turbine engines, certain rotors individually include:
- at least one one-piece bladed disc mounted to rotate around an axis of rotation and having blades each having a leading edge connected, in a one-piece and radially internal manner, to an upstream part of a platform of the one-piece bladed disc, which being itself connected, in a one-piece and radially internal manner, to a rim of the one-piece bladed disc, and
- at least one balancing weight of this one-piece bladed disc rotor.

For the record, a one-piece blisk (DAM; in English: “blisk”; portmanteau combining blade and disk) is a one-piece turbojet element (compressor or turbine part) made up of the blades and the blade disk. A one-piece blisk is typically produced by machining a homogeneous block of metal. Thus, the blades are connected, in a single piece and radially inside (therefore at the root), to a platform of the disc.

In particular on such DAM, the dynamic balancing of a rotor can significantly condition the proper functioning of this rotor.

Also, among the problems that the invention seeks to address, the following is particularly targeted here:
- imagine a solution avoiding/limiting the constraints of the rotor at least at the root of the blade, in the inner section (where the primary air passes, in a turbofan engine), while substantially keeping the mass of the balancing, without therefore significantly increase this mass;
- facilitate assembly/disassembly of (each) weight on the rotor;
- secure the fixing of the (each) flyweight;
- avoid/limit vibrations of (each) counterweight once mounted;
- avoid stressing the connections at the blade roots, on the rotor in question, and therefore avoid limiting its service life,
- to propose a solution which is applicable on any type of disc as long as a conventional arrangement makes it possible to receive the flyweight.

In EP1564372, it is proposed to use a device for balancing a rotor disk of the one-piece bladed disk type, the disk having the characteristics mentioned above and the balancing device comprising, in the radially inner part of the plate -shape, at least one housing where at least one said balancing weight is arranged.

However, the above problems are not resolved.

It is under these conditions that it is first proposed, on a device for balancing a rotor disc of the one-piece bladed disc type:
- that the disc therefore comprises blades connected, in a one-piece and radially internal manner, to an upstream part of a platform of the one-piece bladed disc, itself connected, in a one-piece and radially internal manner, to a rim of the one-piece bladed disc, this disc being mounted to rotate around an axis (X) of rotation and axially having an upstream side, towards which the blades each have a leading edge, and a downstream side, - and that the balancing device comprises, in radially inner part of the platform, at least one housing where at least one balancing weight is arranged,
- with other particularities:
-- that the upstream part of the platform has a flange:
--- extending annularly around said axis (X), upstream of the rim, and,
--- defining, with a radially inner surface of the platform, at least one said housing, and,
-- that the balancing weight is fixed to the flange, cantilevered.

This solution makes it possible in particular to avoid stressing the connections at the blade roots. It is applicable when a layout is planned to receive at least one said weight.

In this text:
- axial has the direction along the X axis or (substantially) parallel to the X axis, which is the axis around which the rotor part rotates (therefore in particular the blades),
- internal and external have respectively (substantially) radially internal and radially external directions with respect to the aforementioned X axis of rotation of the (each) rotor considered here, and
the expressions upstream (AM) and downstream (AV) are to be considered with reference to the general direction of air circulation in the turbomachine, the air concerned here arriving from upstream, passing through at least one compressor, then supplying a combustion chamber where it is mixed with fuel, the gases resulting from the combustion exiting downstream to then pass through at least one turbine adapted to drive the compressor.

The aforementioned solution also makes it possible to avoid limiting the number of holes if such means are provided to fix each flyweight.

Thus it is proposed that the flange has, preferably for each counterweight, an orifice through which a means for fixing the counterweight passes, thus fixing the/each counterweight to this flange.

The flange may in particular be scalloped, which the solution presented here allows, even if the majority of the scallops are drilled for the fixing of the weights.

With fixings by screws/nuts to the flange, assembly/disassembly (possible) of the weights will be easy.

Furthermore, it is also proposed that, the flange extending upstream of the rim, the flyweight then extends between the flange and the rim, with the greater part of its mass located axially closer to the rim than of the flange.

Associated at least with the first characteristics mentioned above, this will reinforce the possibility offered here of limiting the static stress, this making it possible to admit more dynamic stress on the disc, thus modifying for this the axial CDG (center of gravity) of the system, decreasing thus the flexing of the rim, without reducing the mass of the weights, therefore without reducing the overall balancing capacity. As a reminder, the flexing of the rim is proportional to the mass and to the axial position of the center of gravity of the balancing system chosen (including the fixing (bolt + nut typically) and the flyweight.

To further reinforce this aspect, it is also proposed that the/each counterweight has a first part which extends along the flange, on the downstream side, and which is connected to a second part which extends along the surface radially inner of the platform.

With a riser "following" more or less the shape (typically an inverted "L" section) of the flange to then follow that of the "underside" (internal surface) of the platform, we will be able to obtain an axial CDG of the balancing system as far downstream as possible (towards the "neck", the "neck" of a disc being, radially, the radiated part (referenced 68c below) of connection between the platform and a central zone (referenced 68a below) radially more central than the neck. This will have the effect of reducing the bending effect (linked to centrifugal force) and the stress at the level of said blade/platform connections (substantially radiated).

Again to limit the forces exerted statically on the disc, it is also proposed that, in order precisely to urge the flyweight in question towards the radially inner surface of the platform, the/each flyweight has a substantially radial part located opposite said radially inner surface of the platform.

With this substantially radial part, we will therefore promote pressing of the counterweight towards the platform, under centrifugal effect.

And to combine this with a positioning of the axial CDG of the balancing system as far downstream as possible, in order to therefore reduce the bending effect, it is proposed that the balancing weight have, downstream of the first and second parts, a third part more massive than the first and second parts.

This third part may be defined by said substantially radial part.

And, it can also extend the second part downstream, by curving substantially radially towards the axis (X) of rotation.

Thus, we will have individually one-piece flyweights provided with both an upstream fixing, and a backward movement downstream of the CDG (via the second and third parts) and a centrifugal plating effect (with the downstream mass) .

Concerning the upstream fixing, it is in particular proposed that said first part of the flyweight has at least one orifice through which, like the orifice of the flange, the flyweight fixing means passes, in order to thus fix this flyweight to the flange of the platform.

Typically, each flyweight will have a base plate shape, substantially bent in a "C" tilted by 90°, if a shape having said first, second and third parts has been decided upon.

In terms of form, it may be of interest to work on it further, in particular for:
- gain tangential stability (i.e. circumferentially around the X axis), and
- distribute the mass of the weight,
in order, during the rotation of the blades, to further attenuate the local over-stresses at the blade roots, therefore towards their connections to the radially outer surface of the platform.

One solution is to extend the shape of the feeder tangentially.

A recess in the center of the weight allows the mass of the weight to be adjusted.

It is in this context that the following is therefore proposed:
- the first part connects to the second part by widening circumferentially, and/or
- the second part has a hollow which divides it into two lateral portions, and/or
- the blades individually have an angular setting (of the blade root) defining a non-zero angle with respect to a parallel to said axis (X) of rotation, where they are individually connected to the platform, and the second part of the ( each) flyweight substantially follows this angular setting, along the radially inner surface of the platform.

The above solutions generally make it possible to
- a (de)timing downstream of the CDG, and
- a centrifugal plating effect.

In addition to the aforementioned rotor, the invention also relates to a gas turbine engine compressor for aircraft comprising said rotor, with all or part of the aforementioned characteristics.

Brief description of figures

is a schematic half-view (to be completed by symmetry) of a longitudinal (vertical) section of a gas turbine engine for aircraft of the prior art;

is again a schematic half-assembly view of a high-pressure compressor of the turbomachine of FIG. 1, along a longitudinal (vertical) section; in particular the shape of the flanges is roughly represented;

schematizes an example of static stress zones on a DAM of the prior art, at the root of the blades, without the solution of the invention;

illustrates an embodiment in accordance with the invention of the area marked IV in Figure 2 and along section IV-IV in Figure 5,

is a view of the upstream part of a DAM capable of receiving the solution of the invention (no flyweight, nor their fastening system, is however shown there),

shows the weight of Figure 4, alone;

is a view of an alternative embodiment of a flyweight according to the invention;

is another view of this alternative embodiment of the flyweight;

is another view of the same alternative embodiment of the flyweight; And

is a view of another alternative, and

is another view of this flyweight alternative mounted under a DAM platform.

detailed description

FIG. 1 represents an example of a gas turbine engine 20 for an aircraft, in this case a turbofan engine comprising a fan 22 downstream of which the incoming air flow F splits between a primary flow F1 which passes into the engine part 20a of the turbomachine and a secondary flow F2 which passes through a secondary stream 20b which axially surrounds the engine part 20a. The turbomachine 20 has a centerline or central longitudinal axis X around which a rotor part of the turbomachine rotates.

From front to rear and therefore from upstream (AM) to downstream (AV), the engine 20a comprises different sections comprising successively a low pressure compressor (LPC) 24, a high pressure compressor (HPC) 26, a combustion turbine 28, a high pressure turbine (HPT) 30 and a low pressure turbine (LPT) 32. Each of these compressors and turbines, LPC, HPC, HPT and LPT, comprises several stages of rotor blades axially interspersed with associated stages of stator vanes.

The LPC blade stages are coupled to the LPT blade stages via an axial shaft 40 intended to be driven by the LPT. Similarly, the HPC blade stages are coupled to the HPT blade stages via an axial shaft 42. The LPT and LPC blade stages and their associated shaft may form a low pressure body. Similarly, the HPC and HPT blade stages and their associated shaft can form a high pressure body. The bodies can be mounted to rotate around the X axis by bearing systems (not shown). The rotating parts of the LPC, HPC, HPT and LPT can form associated rotors.

A high-pressure compressor 26 such as that of FIG. 2 comprises a central rotor 41 driven by a line of shafts 42 and comprises a casing 44 of tapered shape composed of rings 46 juxtaposed and separated axially by one-piece bladed discs (DAM ) 48 integrating radially (Z axis) stages of moving blades 50. The rings 46 and the one-piece bladed discs 48 form a single assembly, and are therefore one-piece.

A stator 52 surrounds the rotor 41 and comprises, in the inner lining of a carcass 54, a support casing 56 and a ferrule 58 supported by the casing 56, facing the rotor 41. The ferrule 58 serves to delimit the annular vein 20c gas flow (known as the primary vein where the primary flow F1 arrives) in which extend the stages of moving blades 50 and stages of stationary blades (in English "vanes") 60 for straightening the flow, which are hooked to the ferrule 58 and alternate with the previously mentioned floors.

Each one-piece bladed disc (DAM) 48 is therefore mounted to rotate around axis X. Its blades 50, which are distributed over its periphery and extend substantially radially around said axis X, each have a connected leading edge 50a, at 66a, in a one-piece and radially inner manner, to an upstream part of a (radially) inner platform of the one-piece bladed disc. This platform, marked 66, is itself connected, in one piece and radially inside, to a rim 68 of the one-piece bladed disc. Typically this rim may present radially inwards, from the platform 66: the neck 68c (therefore adjacent to this platform), then said central zone 68a, which is thinner than a radially even more inner part 68b, more bulging ( sometimes referred to as the balancing leek).

At least partly radially inner, it is via a succession of platforms (called inner) identified generally 69a, 69b (downstream of the DAM of the first floor, called DAM1) and which are provided respectively in part Inner (radially) the moving vanes 50 and the stationary/fixed vanes ("vanes") 60 that the stream 20c is defined, substantially axially.

Connection 66a is typically concave and substantially radiated.

It can be seen roughly in Figure 2 that the inner platform 66 is provided on its circumference (Y direction) with at least one weight 70 for balancing the rotation of the disc and more generally of the rotor.

As detail IV of this figure 2 indicates, among the one-piece bladed discs 48, that of the DAM1 in the example is shown schematically in part in figure 4. In this figure, however, it is an embodiment in accordance with invention and therefore different from the local representation of figure 2.

As for figure 3, it makes it possible to deduce that, without any particular precaution:
- the life of the DAM may be limited, because the area of the DAM1 illustrated here is mechanically loaded (increasing static load from A to D). The first stages of the compressor are therefore loaded with stress at the root of the blade 50, since the ratio between the volume of the blade and that of the disc can be high in comparison with those of the last stages of the compressor;
- the level of static stress in the area (of the radius) of the blade/platform connection is decisive for the service life of the part and the vibration margin. If the static stress is high, less dynamic stress will be admitted. In addition, gaining vibration margin is important, especially for the certification of the turbomachine.

It should be noted that the (radius of) connection 66a of the blade, for the first bending mode of DAM1, is an important zone considered here, because it is loaded with stresses, in both static and dynamic situations. This is where most of the loads are exerted, when the turbomachine is rotating (direction of rotation S around the X axis; figure 3).

These problems of excessive mechanical loads/stresses therefore linked to the presence of unbalance or counterweight(s) have thus led here, as illustrated in figures 4.5:
- that the upstream part of the platform 66 has (integrates) a flange 72 extending annularly, around said axis X, upstream of the rim 68 and defining, with a radially inner (on) face 66c of the platform form, at least one housing 73,
- And that the balancing weight 170 is fixed to the flange 72, cantilevered.

Flange 72 here is an "upstream flange" that extends upstream of rim 68.

Thus, during the rotation of the rotor, the flyweight 170 will centrifugal on the side of the face 66c of the DAM platform and will then concentrate the mechanical stresses there, downstream of the flange, therefore closer to the neck of the disc (zone 68c in FIG. 4) only with a flyweight assembly on the upstream face of the flange, thus limiting the stresses at the location of the connection 66a of the blade root. If there are such radial supports under pressure from the flyweights, they will operate only when the rotor and therefore the discs 48 rotate around the X axis.

Moreover, to urge, by centrifugal effect, the flyweight 170 considered towards the radially inner surface 66c of the platform, it is proposed that, in the recessed housing 73 where it is located, the flyweight has a part 81 substantially radially opposite said radially inner surface of the platform; see figure 4.

For said radial supports, and at least to promote an offset towards the downstream of the CDG, each counterweight 170 will favorably present a (first) upstream part 170a extending along the flange 72, on the downstream side, and which will be connected to a (second) part 170b, downstream, extending along the radially inner surface 66c of the platform 66; see also in particular Figure 4.

It is easy to provide said substantially radial part 81 on this second part 170b, by forming it projecting, on the side facing the axis X, therefore opposite the radially inner surface 66c of the platform.

As illustrated in Figures 4.5, the flange 72, rather than having a uniformly constant height H radially over 360°, can be scalloped, thus with depressions 72a alternating circumferentially with projections 72b extending radially towards the X axis.

The flange 72 extends radially towards the X axis in the preferred example illustrated (L-section shape).

For its fast, reliable, safe and practical fixing in order to reach the aforementioned axial (downstream offset) and radial (for support) positions, it is recommended:
- that the (each) flyweight 170 considered therefore has a said upstream part 170a (called the first part, provided that there is at least said second part 170b) which is substantially parallel to the flange 72 (or to the projection 72b considered) ,
- and that this upstream part 170a is crossed by an orifice 171, for fixing (which may be removable) of the counterweight 170 considered at the flange 72.

The flange itself has an axial orifice 74 .

Thus a means for fixing the weight 170 can be engaged through the then aligned holes 74,171, thus fixing the / each balancing weight to the flange, as shown in Figure 4.

The means 75 for individual fixing of the flyweights 170 may comprise screws 77 and nuts 79 arranged and tightened together axially (parallel to the axis X). This will allow easy and safe assembly/disassembly.

Arranged downstream of the upstream flange 72, each balancing weight 170 will therefore extend between this flange and the rim 68, preferably with the largest part of its mass – zone(s) 810 in FIGS. 6-11 – which may be located axially closer to the rim than to the flange, shifting the CDG even further downstream and thus further limiting the risk of the flange flexing, under the centrifugal effect, and therefore the risk of deflection of the platform, or even of the rim.

This or these zone(s) 810 may coincide with the substantially radial part 81 mentioned above. In particular, it can be provided that downstream (AV) of the first and second parts 170a, 170b, each flyweight has a third part 170c which is more massive than the first and second parts.

For ease of manufacture and certain efficiency, the third part 170c can extend the second part 170b downstream, by curving substantially radially towards the axis X of rotation, as shown in the figures, and marked in particular in Figures 6 and 9.

Preferably, each flyweight 170 will be in one piece, so in one piece. Despite its various aforementioned parts, and a section which can be substantially C-shaped, the flyweight will only be crossed by the fixing means selected (the screw 77 in the example) at the location of its upstream part 170a, in order to achieve the desired overhang.

In the embodiment of Figures 4.6, the flyweight 170 is presented as a plate of width l (in the circumferential direction, once the mass mounted as Figure 4) constant from upstream to downstream.

The width l could, however, widen from upstream to downstream and/or, as can be seen clearly in these two figures, the weight could thicken (in the radial direction, once the mass has been mounted; thickness e) in the downstream direction, so that the mass is greater on the downstream side of the flyweight than on the upstream side.

In the embodiment of Figures 7-11, the first part 170a of the flyweight 170 is also connected to the second part 170b by widening, circumferentially. But this can, as here, be provided also or above all to gain circumferential stability and distribute the mass of the flyweight in order to attenuate the local over-stress at the root of the blade substantially under which the flyweight in question will be mounted.

In this regard, Figure 11 shows the relative positions, in particular in the circumferential direction, that the blades and the mounted flyweights may occupy; here two successive vanes 50 and a flyweight 170. It is noted that the solution provided for extending the shape of the flyweight circumferentially. A recess or hollow 83 towards the center of the weight can allow the mass of the weight to be adjusted.

In the solution retained and illustrated, the flyweight 170 is such that its second part 170b has a hollow 83 which divides it into two lateral portions 173, 175.

These lateral portions 173, 175 can extend parallel to the axis X, on either side of the hollow 83.

In the solution shown schematically in Figure 11, however, we note:
- that, with respect to two axes X1, X2 parallel to the axis X and passing through the respective connections of these blades to the platform 66, the blades 50 individually have an angular pitch at the blade root defining an angle α not zero (the setting may vary according to the height of the blade and in this case, it is the setting at the foot that is of interest), and
- that said second part 170b of the flyweight 170 substantially follows this angular setting at the blade root (thus along the radially inner surface of the platform), via its two wings or lateral portions 173, 175 which are respectively radially located substantially in the elevation planes of the blade 50 considered: see substantially radial plane P1 in FIG. 4 which passes through the connection of the blade to the platform and through a radial section of the flyweight 170 shown.

Thus, the weight of the solution shown schematically in figure 10.11 is twisted laterally, from upstream to downstream, therefore following the circumference once the weight is mounted.

The aim is for the flyweight to "push" radially substantially below the blade connection radii (in the rigid zone therefore). One expects from such a solution a notable reduction in the stresses at the root of the blade, in comparison with figure 3, in particular towards zone 66a.

Tests indicate a reduction of more than 10%. This allows a gain in static stress at the blade connection radius.

In the preferred and illustrated embodiments, the splitting into two side portions 173, 175 of the second part 170b results in that of the third part 170c, which therefore itself has two side portions 810a, 810b (FIG. 8) separated by the opening 830 downstream of the hollow 83, following the circumference once the flyweight is mounted.

Once mounted, the weight is in contact with the disc 48 which is a critical part, to spare. To limit the risk of alteration, each flyweight 170 can be coated with a layer 85 of varnish so as not to wear out the (sur)face 66c and “slip” on contact with it. The risk of scratching is thus limited.

Claims (13)

Device for balancing a rotor disk (48) of the one-piece bladed disk type, the disk comprising blades (50) connected, in a one-piece and radially internal manner, to a platform (66) of the one-piece bladed disk, itself connected, in a one-piece and radially internal manner, to a rim (68) of the one-piece bladed disc, the disc (48) being mounted to rotate around an axis (X) of rotation and axially having an upstream side, towards which the blades ( 50) each have a leading edge (50a), and a downstream side, the balancing device comprising, in the radially inner part of the platform (66), at least one housing (73) where at least a balancing weight (170), characterized in that:
- the upstream part of the (or each) platform (66) (or at least some of these platforms) has a flange (72):
-- extending annularly around said axis (X), and,
-- defining, with a radially inner surface (66c) of the platform, at least one said housing (73), and,
- the balancing weight (170) is fixed to the flange, cantilevered. Balancing device according to Claim 1, in which the flange has an orifice (74) through which a means for attaching the balancing weight (170) passes, fixing the/each balancing weight (170) to the flange ( 72). A balancing device according to claim 1 or 2, wherein the flange (72) extends upstream of the rim (68), and the balancing weight (170) extends between the flange and the rim (68 ), with most of its mass located axially closer to the rim than to the flange. Balancing device according to any one of the preceding claims, in which the balancing weight (170) has a first part (170a) which extends along the flange (72), on the downstream side, and which connects to a second part (170b) which extends along the radially inner surface of the platform. Balancing device according to any one of the preceding claims, in which, in order to urge, by centrifugal effect, the flyweight in question towards the radially inner surface of the platform, the/each flyweight has a substantially radial part (81) located at opposite said radially inner surface (66c) of the platform Balancing device according to Claims 3 and 4, in which the balancing weight (170) has, downstream of the first and second parts, a third part (170c) more massive than the first and second parts. Balancing device according to claim 6, in which the third part (170c) extends the second part downstream, curving substantially radially towards the axis (X) of rotation. Balancing device according to Claims 2 and 4, alone or in combination with at least one of Claims 5 to 7, in which the first part has at least one orifice (171) passed through, such as the orifice (74) of the flange, by the balancing weight (170) fixing means, to fix the balancing weight (170) to the flange (72). Balancing device according to Claim 4, alone or in combination with at least one of Claims 5 to 8, in which the first part (170a) is joined to the second part (170b) by widening circumferentially. Balancing device according to Claim 4, alone or in combination with at least one of Claims 5 to 9, in which the second part (170c) has a hollow (83) which divides it into two lateral portions. Balancing device according to Claim 4, alone or in combination with at least one of Claims 5 to 10, in which:
- the blades (50) individually have an angular blade root setting defining a non-zero angle with respect to a parallel to said axis (X) of rotation, where they are individually connected to the platform (66), and
- the second part of the balancing weight (170) substantially follows this angular setting of the blade root, along the radially inner surface of the platform. Rotor (10) of a gas turbine engine for aircraft, characterized in that it comprises at least one balancing device according to any one of the preceding claims. An aircraft gas turbine engine compressor comprising the rotor of claim 12.