Blade comprising a blade root protection insert, fan and associated method.

Abstract

The present invention relates to a turbomachine blade (8) comprising a blade root (9) and a blade (10) extending from the blade root (9), the blade root (9) being intended to be received in a housing (12) made in a rotor disk (11) of the turbomachine and delimited by walls (12a), the blade comprising a protective insert (14) of which an inner surface (14a) at least partially encloses the blade root (9) so as to cover the entire surface of the blade root (9) intended to be in contact with the rotor disk (11) and of which an outer surface (14b) is intended to match the walls (12a) of the housing (12), the protective insert (14) being configured to deform elastically under the effect of forces applied by the rotor disk (11) and / or the blade root (9) during operation of the turbomachine. Figure for abstract: Fig. 2

Description

Title of the invention: Bladed wheel comprising a bladed wheel foot protection insert, blower and associated method. Technical field

[0001] The field of the invention is that of turbomachines and more particularly that of securing a fixed or variable pitch bladed wheel foot in a blower rotor, even if it is applicable to other rotors of the turbomachine.

[0002] The invention more particularly relates to the interface between a composite bladed wheel foot and a metallic rotor disk, especially of a blower. STATE OF THE ART

[0003] On a turbomachine, in particular a bypass turbojet, a fan is arranged upstream of the low-pressure compressor relative to the direction of air flow in the turbomachine. Its role is to ensure the initial compression of the air entering the turbomachine. Such a fan generally comprises a plurality of blades extending radially relative to an extension axis (also referred to as the axis of rotation) of the turbomachine, from a fan rotor disk. More particularly, each of the blades comprises at its base a blade root secured to the rotor of the fan.

[0004] Conventionally, the attachment of the root of a blade to the fan rotor is achieved by the cooperation of the blade root with a housing made in the fan rotor disc. A so-called dovetail assembly can be used, or alternatively a so-called tulip assembly. Alternatively, the root can be manufactured separately from composite material or metal and then bonded to the blade in addition to a so-called finger or wedge connection.

[0005] However, conventionally, the housing is machined with dimensions greater than those of the blade root, in order to be able to easily insert the blade root into said housing, this insertion being particularly carried out by sliding along a longitudinal axis parallel to the extension axis in the case of a dovetail assembly.

[0006] Due to these differences in dimensions, a clearance exists between the blade root and the walls of the housing, so that during individual movements of the blades relative to the disc, overstresses can occur in the contact surfaces, the variable and localized nature of these overstresses being able to lead to degradation, for example by contact fatigue.

[0007] In an attempt to overcome these drawbacks, some engines have integrated so-called "fin" blades which add a stop limiting the unit movement of one of the blades relative to the others.

[0008] It is also known to add accommodation strips (also called "wearstrips") which are conventionally arranged on either side of the blade root (fixed to the blade root or on opposite walls of the housing) and which consist of a coating to protect the interfaces between the blade root and the walls of the housing. A shim can also be arranged under the blade root in the housing.

[0009] However, such accommodation strips are not particularly suitable for variable pitch blades, these being subjected to static and dynamic loads which are fluctuating.

[0010] Furthermore, on the one hand, the rotor disk, and consequently the walls of the housing, are traditionally metallic or made of a metal alloy and thus generally made of homogeneous and isotropic materials. On the other hand, blades made of composite material or whose root is made of composite material are generally non-isotropic and non-homogeneous, in particular when the material used is an organic matrix composite (for example long carbon fiber, whether woven, sleeve, 3D woven laminated or wound) in an epoxy type polymer matrix.

[0011] However, when such metal parts are assembled with such composite material parts, the interface surfaces of the composite and metal parts behave differently, particularly in deformation. Thus, for assemblies (such as that of the blade root in a fan rotor disk housing) which see variable loads and therefore stress concentrations in the variable interfaces and which may locally exceed the accommodation capacities by plastic deformation of one or both parts, slippage and consequently surface degradation or deep fatigue (fatigue butterflies, delamination, contact wear, etc.) may appear. EXPOSED

[0012] An aim of the invention is to remedy the aforementioned drawbacks, by proposing a turbomachine blade which is easily insertable into the housing of the rotor disk and whose blade root is protected, on the one hand, from impacts against the walls of the housing and, on the other hand, from an interface with a part of a material mechanically dissimilar to the material forming the blade root.

[0013] To this end, according to a first aspect, a turbomachine blade is proposed comprising a blade root and a blade extending from the blade root, the blade root being intended to be received in a housing made in a rotor disk of the turbomachine and delimited by walls, the blade comprising a protective insert, an inner surface of which at least partially encloses the blade root so as to cover the entire surface of the blade root intended to be in contact with the rotor disc and an outer surface of which is intended to fit the walls of the housing, the protective insert being configured to deform elastically under the effect of forces applied by the rotor disc and / or the blade root during operation of the turbomachine.

[0014] Advantageously, the protective insert is fixed to the blade root by gluing.

[0015] Preferably, at least the blade root is made of composite material. Advantageously, the protective insert is made of metal foam.

[0016] Advantageously, the protective insert is made of polymeric foam.

[0017] Advantageously, the protective insert has a thickness of between 1 millimeter and 1 centimeter, the protective insert being configured to fill a gap between the walls of the housing and the blade root.

[0018] Preferably, the protective insert comprises portions of different thicknesses.

[0019] Advantageously, the protective insert comprises parts of different porosities.

[0020] In a preferred embodiment, the protective insert comprises portions having regular porosity and / or portions having stochastic porosity and / or solid portions.

[0021] Advantageously, the protective insert is at least partially made of hyperelastic material, for example of the Nickel Titanium type.

[0022] Advantageously, the protective insert is manufactured by casting or by metal injunction or by additive manufacturing.

[0023] The invention relates, by a second aspect, to a turbomachine fan, comprising a plurality of fan blades as defined previously, a metal fan rotor disk comprising a plurality of housings, each blade of the plurality of blades comprising a blade root received in a housing of the plurality of housings.

[0024] The invention also relates in a third aspect to a method of attaching a blade root in a housing of a rotor disk, comprising the following steps:

[0025] - manufacturing a protective insert configured to at least partially enclose the blade root so as to cover the entire surface of the blade root intended to be in contact with walls of the housing and configured to deform elastically under the effect of forces applied by the rotor disk and / or the blade root;

[0026] - if necessary, fixing the protective insert at the blade root or in the accommodation ;

[0027] - insertion of the blade root into the housing.

[0028] Advantageously, the protective insert is manufactured at least partially in blade root contact or is manufactured separately and then fixed by gluing to the blade root or in the housing. DESCRIPTION OF FIGURES

[0029] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0030] [Fig.l] illustrates a schematic view, in axial and partial section, of an example of a turbomachine according to an embodiment of the invention;

[0031] [Fig.2] illustrates a partial schematic perspective view of a fan rotor and a blade according to a first embodiment of the invention, with a dovetail blade root, before insertion of the blade root into the fan rotor;

[0032] [Fig. 3] is a partial schematic perspective view of the blade of [Fig. 2] inserted into the fan rotor disc; and

[0033] [Fig.4] is a partial schematic perspective view of a variant of [Fig.2], in which the protective insert is fixed to the rotor disc;

[0034] [Fig.5A] illustrates a partial schematic perspective view of a blade according to a second embodiment of the invention, with a tulip-shaped blade root;

[0035] [Fig.5B] illustrates a partial schematic perspective view of a protective insert adapted to protect the blade of [Fig.5A];

[0036] [Fig.6] illustrates the blade of [Fig.4] in partial section inserted into a fan rotor disc with the protective insert of [Fig.5B]; and

[0037] [Fig.7] illustrates a stress-strain curve of a hyperelastic alloy capable of forming the protective insert according to the invention; and

[0038] [Fig.8] schematically illustrates the different stages of the method according to the invention.

[0039] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION

[0040] In [Fig.l], the turbomachine 1 shown is an aircraft turbomachine. The turbomachine 1 comprises a fan 2, a compression section 3, a combustion chamber 4, a turbine section 5 downstream of the combustion chamber 4, and an exhaust casing 50.

[0041] The fan 2 comprises a rotating blading 6. Alternatively, the invention applies to a static blading. The blading 6 may have a fixed or variable pitch. In a preferred embodiment of the invention and as is the case in the example illustrated in [Fig.l], the turbomachine 1 may be a turbojet comprising a shrouded fan 2, that is to say that the turbomachine 1 comprises a casing 7 surrounding the fan 2 and the fan blade 6. In an alternative embodiment, the turbomachine 1 may in particular be a USF type turboprop (acronym for "Unducted Single Fan") comprising an unducted propeller in place of the ducted fan 2, in which case the fan blade is unducted and extends downstream of the propeller.

[0042] The blading 6 comprises by definition a plurality of blades 8. With reference to [Fig.2], each blade 8 comprises a blade root 9 and an aerodynamic blade 10 extending from the blade root 9. The fan 2 further comprises a fan rotor disk 11 having on its periphery a plurality of housings 12 each configured to receive a blade root 9 so as to attach a blade 8 to the fan rotor disk 11. Thus, each blade root 9 of the plurality of blades 8 is received in one of the housings 12 of the plurality of housings 12.

[0043] To facilitate understanding, the description of a housing 12 and of the fixing of a blade root 9 of a blade 8 in the housing 12 will now be made. Nevertheless, said description can apply to one or more, and preferably to all of the other housings 12 receiving a blade root 9 of a blade 8.

[0044] In the present application, upstream and downstream are defined relative to the direction of flow of the gases through the blading 6. The axis X is called the axis of rotation of the blades 8 around the rotor of the fan 2 (respectively, of the propeller). The axis X thus corresponds to the axis of rotation of the fan 2, and can also be called the axis of extension of the fan 2 in its length.

[0045] Unless otherwise specified, the axial direction is thus called the direction corresponding to the X axis and radial direction a direction perpendicular to and passing through that X axis. Furthermore, unless otherwise specified, "internal" and "external" are used with reference to a radial direction such that the internal part or face of an element is closer to the X axis than the external part or face of the same element.

[0046] Figures 2, 3 and 4 illustrate in particular an example of assembly of a blade root 9 of a blade 8 according to the invention inserted in a housing 12 of the fan rotor disk 11 in which said assembly is dovetail (or pinned attachment). Alternatively, and as illustrated in an example in Figures 5A, 5B and 6, the assembly may be tulip-shaped (also called bulbous root). Alternatively again, the assembly may be of any other suitable nature.

[0047] The housing 12 is defined by one or more walls 12a configured to receive the blade root 9 and prevent it from escaping during operation of the turbomachine 1. In particular, the dimensions of the housing 12 are greater than the dimensions of the blade root 9 intended to be inserted into said housing 12, in order to allow easy and rapid insertion of said blade root 9 into said housing 12. dimensions of the blade root 9 and of the housing 12 are similar and conventional to those known from the state of the art.

[0048] In general, the housing 12 comprises a radially external opening 13 of a width less than the width of a portion of the blade root 9, but sufficiently large to allow the aerodynamic blade 10 to extend radially outwards when the blade root 9 is received in the housing 12.

[0049] Advantageously, the blade 8, and more particularly at least the blade root 9 of the blade 8, is made of composite material, for example of organic matrix composite material. For example, the blade 8 is made of long carbon fiber in an epoxy polymer matrix. In addition and advantageously, the walls 12a of the housing 12 are metallic, like the rotor disk 11. For example, the walls 12a and more generally the rotor disk 11 is made of a basic metal alloy Aluminum, Iron, Magnesium, or Titanium. Thus, the materials composing on the one hand the blade root 9 and on the other hand the walls 12a of the housing 12 can be mechanically dissimilar. This is not, however, limiting, and the invention applies to a metal blade inserted in a housing 12 with metal walls 12a.

[0050] Furthermore, the blade root 9 comprises a protective insert 14 intended to form an interface between the blade root 9 and the wall(s) 12a of the housing 12.

[0051] The protective insert 14 comprises an inner surface 14a at least partially covering the blade root 9 and an outer surface 14b intended to at least partially match the walls 12a of the housing 12.

[0052] The inner surface 14a at least partially covers the blade root 9 by gripping it. By "gripping" is meant that the inner surface 14a is threaded onto the blade root 9 and exerts a clamping force on said blade root 9 so as to eliminate any play between the inner surface 14a and the blade root 9.

[0053] More precisely, the inner surface 14a at least partially encloses the blade root 9 so as to cover the entirety of a surface of the blade root 9 intended to be in contact with a wall 12a of the housing 12. More particularly, this surface of the blade root 9 is the surface of the blade root 9 which would be brought into contact with the walls 12a of the housing 12 during normal operation of the turbomachine 1 and when the turbomachine 1 is stopped. The inner surface 14a thus preferably encloses the entirety of the outer surface of the blade root 9 inserted in the housing 12 and arranged opposite the walls 12a of the housing 12.

[0054] Thus, the inner surface 14a matches the shape of the blade root 9.

[0055] Similarly, and as stated previously, the outer surface 14b of the protective insert 14 is intended to fit the walls 12a of the housing 12 opposite the blade root 9 when the blade root 9 is inserted into the housing 12. Preferably, the outer surface 14b thus has a shape similar to that of the housing 12, in order to facilitate the insertion of the blade foot 9 into the housing 12.

[0056] The protective insert 14 therefore prevents direct contact between the blade root 9 and the walls 12a, and thereby protects both from possible degradation due to the mechanical dissimilarity of the materials constituting respectively on the one hand the blade root 9 and on the other hand the walls 12a.

[0057] Advantageously, the protective insert 14 may be elastically deformable. More particularly, the protective insert 14 may be configured to deform elastically under the effects of forces applied thereto by the rotor disk 11 via the walls 12a of the housing 12 or by the blade root 9, in particular during operation of the turbomachine 1. In such a way, a force applied by and / or a displacement of one of the rotor disk 11 and the blade root 9 does not influence the other.

[0058] In other words, when a force is exerted by one of the rotor disk 11 and the blade root 9, the protective insert 12 absorbs said force by deforming (thus improving the distribution of the forces), so that said force does not damage the other of the rotor disk 11 and the blade root 9.

[0059] In this way, the blade root 9, as well as the rotor disk 11, is protected against impacts and damage which may be caused by forces applied by the rotor disk 11 and / or the blade root 9 and / or by a displacement of one of the two due to the operation of the turbomachine.

[0060] Preferably, the protective insert 14 may be made of metal foam, and possibly of metal alloy foam. For example, the metal foam used may be an aluminum foam or a steel foam, in particular depending on the load cases.

[0061] Such a material allows the protective insert 14 to deform to absorb the forces. In addition, metal foams have the advantage of having a very low mass, high resistance to high pressures, temperatures, humidity, wear, as well as good shock absorption.

[0062] In addition, the metal foam of the protective insert 14 may have stochastic or regular porosity. Regular porosity may in particular be preferred to better control the flexibility of the different parts of the protective insert 14, while stochastic porosity is generally simpler to manufacture.

[0063] In particular, the protective insert 14 may comprise parts of different porosities in order to take into account the zones of maximum stresses and deformations. In particular, a reduced porosity makes it possible to increase the friction between the protective insert 14 and a part in contact, so that a displacement of said part can be better absorbed by the protective insert 14. Advantageously, the porosity of the protective insert 14 may be reduced in parts of the insert 14 that are highly sol licited by forces and displacements of the rotor disc 11 or the blade root 9. In particular, to ensure the best possible contact with the rotor disc 11 or the blade root, such parts may be solid or have a lower porosity, while the remainder of the protective insert 14 may have a higher porosity.

[0064] Thus, the protective insert 14 may comprise solid portions and / or portions having regular porosity and / or portions having stochastic porosity. The porosity of the protective insert 14 is thus chosen in order to best perform the function of accommodation and distribution of forces.

[0065] In particular, the protective insert 14, whether made of metal foam or not, may be made partially or completely of a hyperelastic material, to allow a locally very high elastic accommodation capacity (and therefore elasticity), without entering into irreversible damaging deformations. In particular, the protective insert 14 may be at least partially made of a hyperelastic material of the Nickel Titanium (NiTi) or nitinol type, such as Nitinol60. A metal alloy foam of such a hyperelastic material has very high damping capacities as demonstrated by the size of the hysteresis in [Fig.7], which illustrates a typical stress-strain curve of such a hyperelastic alloy.

[0066] When such elasticity is not necessary in view of the operating range of the turbomachine 1 or for lightly loaded applications or those with a limited service life, the protective insert 14 may however be made of polymeric foam.

[0067] The protective insert 14 then has an elastic range that is sufficiently large so as not to be damaged in the operating range of the turbomachine 1.

[0068] The protective insert 14 has a thickness which is defined by the distance between the inner 14a and outer 14b surfaces, and which is preferably between 0.1 millimeter and 1 centimeter. This thickness of the protective insert 14 is in particular equal to or slightly greater than the difference in dimensions between the housing 12 and the blade root 9. By "slightly greater", it is meant that the thickness of the protective insert 14 may be greater than the difference in dimensions between the housing 12 and the blade root 9 by one tenth of said difference. In any event, the protective insert 14 is, by its thickness, configured to fill the clearance between the blade root 9 and the walls 12a of the housing 12 (due to the differences in dimensions previously described). In this way, the absorption of forces is improved, and the blade root 9 is wedged in the housing 12 (pressed against the walls 12a), so as to limit shocks.An additional shim is therefore not necessary in housing 12.

[0069] In particular, the protective insert 14 may comprise portions of different thicknesses depending on the local constraints intended to be applied to said portions by the rotor disk 11 and / or the blade root 9. In particular, in a portion of the insert 14 intended to undergo particularly high stresses or deformations due to the geometry of the blade root 9 and / or the housing 12, the thickness of said portion may be increased relative to the rest of the insert 14 in order to better absorb said stresses or deformations. Said stresses may result from constant forces such as centrifugal forces, or from variable forces such as the forces applied by the blade root 9 depending on the incidence of the blade 10 (depending on the defined pitch) or due to the ingestion by the turbomachine 1 of birds.

[0070] Figures 2, 3 and 4 illustrate a dovetail assembly of the blade root 9 and the housing 12. Figures 5A, 5B and 6 illustrate a tulip assembly.

[0071] The protective insert 14 may be manufactured separately from the blade root 9 and then fixed to said blade root 9. The fixing of the protective insert 14 to the blade root 9 may be carried out by gluing. Alternatively, the protective insert 14 may be directly manufactured in contact with the blade root 9, the protective insert 14 being in this case machined so as to be monolithic with at least a portion of the blade root 9, which allows the protective insert 14 to have an inner surface geometry 14a as close as possible to that of the blade root 9.In such an embodiment, the blade 8 may for example be produced by additive manufacturing so as to provide a zone with structured or regular porosity near the zones intended to be in contact with the walls 12a of the housing 12, to integrate this function of localized flexibility, or even be preassembled with the protective insert 14, by the integration of the protective insert 14 in the mold of the composite blade 8 during its polymerization. Alternatively again, the protective insert 14 is an independent part of the blade 8 machined separately, then bonded to the walls 12a defining the housing 12 before the insertion of the blade root 9 into the housing 12, as illustrated in [Fig.4] and in [Fig.5B]. .

[0072] The protective insert 14 makes it possible, in a dovetail assembly such as shown in FIGS. 2 to 4, to prevent tilting of the blade 8 around an axis parallel to the axis X passing through the blade root 9 and which could lead to deformation of the blade root 9 and / or of the rotor disk 11 which would risk causing localized stress concentrations and damaging the parts.

[0073] In Figures 5A, 5B and 6, the protective insert 14 and / or the walls 12a are shown partially in order to gain clarity and make the different elements visible. The portions of the blade root 9 most heavily stressed during operation of the turbomachine 1 in such a tulip assembly are shown in a light color in Figures 5A and 6. As described previously, the protective insert 14 encloses the surface of the blade root 9 inserted in the housing 12 so as to cover a surface of the blade root 9 in contact with the walls 12a of the housing 12. In order to best protect these highly stressed portions, the protective insert 14 may include locally adapted parts through specific porosity and / or thickness.

[0074] In all cases, the protective insert 14 also makes it possible to protect the blade root 9 and the rotor disk 11 when they are made of mechanically dissimilar materials, for example when the blade root 9 is made of composite material and the rotor disk has walls 12a of the metal housing 12. In fact, the protective insert 14 forms a protective coating preventing direct contact between the blade root 9 and the walls 12a.

[0075] The invention also relates to a method for attaching the blade root 9 in the housing 12 of the rotor disk 11, the following description of which is illustrated with the aid of FIGS. 7 and 8.

[0076] In a first step E1, the protective insert 14 is manufactured as described previously. In addition, the protective insert 14 is manufactured so as to exert a clamping force on the blade root 9. Said clamping is adapted specifically according to the destination and the shape of the assembly. Similarly, the porosity and the thickness of the portions of the protective insert 14 are chosen and produced according to the context of the assembly. The protective insert 14 is produced by casting or by metal injection molding (MIM), or by additive manufacturing.

[0077] The protective insert 14 can be made directly in contact with the blade root 9.

[0078] Alternatively, the protective insert 14 can be made separately. In this case, the method comprises a second step E2 during which the protective insert 14 is fixed to the blade root 9, as illustrated in figures 2 and 5, or in the housing 12 on the walls 12a, as illustrated in [Fig.7]. This fixing can for example be carried out by gluing.

[0079] In a third step E3, the blade root 9 is inserted into the housing 12. For example, this insertion is carried out by sliding in the case of a dovetail assembly.

[0080] The protective insert 14 can be compressed to allow the blade root 9 to be housed in the housing 12, and thus presses the blade root 9 against the walls 12a.

[0081] In the foregoing, the invention has been described in the case of a blade 8 and a fan rotor disk 12. This is not, however, limiting, and applies to any other blade of the turbomachine 1. Similarly, the invention has been described in the case of an interface between a part made of composite material and a part made of metal. This is not limiting, and the invention applies in the same way to other assemblies of two parts respectively made of mechanically dissimilar materials, such as for example metal for one and ceramic for the other, metal for one and ceramic matrix composite material for the other, composite material with organic matrix for one and ceramic for the other, or metal for one and glass for the other, etc.

Claims

Claims

1. A blade (8) of a turbomachine (1) comprising a blade root (9) and a blade (10) extending from the blade root (9), the blade root (9) being intended to be received in a housing (12) made in a rotor disk (11) of the turbomachine (1) and delimited by walls (12a), the blade (8) comprising a protective insert (14) of which an inner surface (14a) at least partially encloses the blade root (9) so as to cover the entire surface of the blade root (9) intended to be in contact with the rotor disk (11) and of which an outer surface (14b) is intended to match the walls (12a) of the housing (12), the protective insert (14) being configured to deform elastically under the effect of forces applied by the rotor disk (11) and / or the blade root (9) during operation of the turbomachine (1).

2. Blade (8) according to claim 1, in which the protective insert (14) is fixed to the blade root (9) by gluing.

3. Blade (8) according to one of claims 1 or 2, in which at least the blade root (9) is made of composite material.

4. Blade (8) according to one of claims 1 to 3, in which the protective insert (14) is made of metal foam.

5. Blade (8) according to one of claims 1 to 3, in which the protective insert (14) is made of polymeric foam.

6. Blade (8) according to one of claims 1 to 5, in which the protective insert (14) has a thickness of between 1 millimeter and 1 centimeter, the protective insert (14) being configured to fill a gap between the walls (12a) of the housing (12) and the blade root (9).

7. Blade (8) according to one of claims 1 to 6, in which the protective insert (14) comprises portions of different thicknesses.

8. Blade (8) according to one of claims 1 to 7, in which the protective insert (14) comprises parts of different porosities.

9. Blade (8) according to one of claims 1 to 8, in which the protective insert (14) comprises parts having regular porosity and / or parts having stochastic porosity and / or solid parts.

10. Blade (8) according to one of claims 1 to 9, in which the protective insert (14) is at least partially made of hyper-elastic material, for example of the Nickel Titanium (NiTi) type.

11. Blade (8) according to one of claims 1 to 10, in which the insert of protection (14) is manufactured by casting or by metal injunction (MIM) or by additive manufacturing.

12. Turbomachine fan (2), comprising a plurality of fan blades (8) according to one of claims 1 to 11, a metal fan rotor disc (11) comprising a plurality of housings (12), each blade (8) of the plurality of blades comprising a blade root (9) received in a housing (12) of the plurality of housings.

13. Method for attaching a blade root (9) in a housing (12) of a rotor disk (11), comprising the following steps: - manufacturing (El) a protective insert (14) configured to at least partially enclose the blade root (9) so as to cover the entire surface of the blade root intended to be in contact with walls (12a) of the housing (12) and configured to deform elastically under the effect of forces applied by the rotor disk (11) and / or the blade root (9); - where appropriate, fixing (E2) the protective insert (14) to the blade root (9) or in the housing (12); - inserting (E3) the blade root (9) into the housing (12).

14. Method according to claim 13, in which the protective insert (14) is manufactured at least partially in contact with the blade root (9) or is manufactured separately and then fixed by gluing to the blade root (9) or in the housing (12).

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