Turbomachine rotor including a cover over the fixing bolts

Abstract

The invention relates to a turbomachine arrangement comprising a rotor rotating about a longitudinal axis of the turbomachine, and a rotating element (11) secured to this rotor by a series of fastening bolts (17) distributed circumferentially around the longitudinal axis, each bolt (17) protruding from a face of the rotating element. According to the invention, the arrangement includes a crown-shaped cover (22) fixed to the face (21) of the rotating element to cover the ends of the bolts (17) protruding from the face (21) of the element. Figure 4

Description

Title of the invention: Turbomachine rotor comprising a cover covering fixing bolts Technical field

[0001] The invention relates to a turbomachine such as an aircraft turbojet comprising a rotor formed of elements fixed to each other by bolts distributed circumferentially and oriented parallel to the axis of rotation of the rotor. STATE OF THE PRIOR ART

[0002] In such a turbojet 1 shown in [Fig.l], the outside air is admitted into an inlet sleeve 2 to pass through a fan 3 comprising a series of rotating blades before splitting into a central primary flow and a secondary flow surrounding the primary flow.

[0003] The primary flow is then compressed in a first and second compression stage 4 and 6 before arriving in a combustion chamber 7, after which it expands by passing through a set of turbines 8 before being evacuated towards the rear, generating thrust. The secondary flow is propelled directly towards the rear by the fan in a vein delimited by the casing 9 to generate additional thrust.

[0004] In practice, such an engine comprises a rotor rotating around the longitudinal axis AX of the engine, and including several discs each carrying at its external periphery a series of blades or vanes, these discs corresponding to the fan, the compressors and the turbines.

[0005] The attachment of a disc to the other rotor elements is ensured by a set of bolts distributed circumferentially around the longitudinal axis, and each having one end protruding from a face of the arrangement.

[0006] In operation, these bolt ends are subjected to an air flow whose circulation is circumferential relative to the rotor, so that they laminate this air which causes a loss of power which is detrimental to the energy efficiency of the engine.

[0007] The aim of the invention is to provide a solution to overcome this drawback. Statement of the invention

[0008] To this end, the invention relates to a turbomachine rotor comprising an element secured to another element by a series of fixing bolts distributed circumferentially around an axis of rotation of the rotor, each bolt extending parallel to the axis of rotation and having one end projecting from an axial delimiting face of the element, characterized in that it comprises an annular cover which is fixed to the face axial delimitation of the element by bolts and which covers the ends of the fixing bolts.

[0009] Thanks to the annular cover, the bolt heads are confined so as not to be subjected to the flow of air circulating in the machine, so that they do not allow the air located in their vicinity to be "churned", which makes it possible to improve the energy efficiency of the turbomachine.

[0010] The invention also relates to a rotor thus defined, in which the cover comprises fixing lugs, each fixing lug being crossed by a fixing bolt which clamps it against the axial delimiting face of the element.

[0011] The invention also relates to a rotor thus defined, in which each leg has a hole through which a fixing bolt passes.

[0012] The invention also relates to a rotor thus defined, in which each tab comprises a notch crossed by a fixing bolt, each notch having a circumferential orientation in the same direction to allow mounting of the cover by rotation around the axis.

[0013] The invention also relates to a rotor thus defined, in which the fixing lugs extend inside the cover, and in which the cover comprises opposite each lug an access hole to the fixing bolt of this lug.

[0014] The invention also relates to a rotor thus defined, in which each access hole is closed by a weld point.

[0015] The invention also relates to a rotor thus defined, in which each access hole is closed by a tubular cap engaged in this hole and crossed by the corresponding bolt, each tubular cap being held and tightened axially by the bolt which passes through it.

[0016] The invention also relates to a rotor thus defined, in which the cover comprises a crown-shaped front wall having an inner edge extended by an inner flank and an outer edge extended by an outer flank, these flanks having a shape of revolution, each flank being terminated by a rim bearing on the axial delimiting face of the element.

[0017] The invention also relates to a rotor thus defined, in which the external flank of the cover is terminated by a rim which is crenellated to axially block the root of each of the blades carried by the element.

[0018] The invention also relates to a turbomachine equipped with a rotor thus defined. Brief description of the drawings

[0019] [Fig.l] is a side sectional view of a turbojet engine;

[0020] [Fig.2] is a perspective view of a bladed rotor disc;

[0021] [Fig.3] is a detail view of the bolting of the bladed disc to a member of rotor not shown;

[0022] [Fig.4] is an overall view of a bladed rotor disc according to the invention;

[0023] [Fig.5] is a partial perspective view of a rotor disk cover according to the invention;

[0024] [Fig. 6] is a front view of a bladed rotor disc equipped with a cover according to the invention in a section plane extending between the front face of the cover and the upstream face of the disc;

[0025] [Fig.7] is a detailed view of the attachment of a cover to a disc according to the invention;

[0026] [Fig.8] is a detailed view of the attachment of a cover to a rotor disk according to a variant of the invention;

[0027] [Fig.9] is a partial perspective view of a rotor disk cover according to a second embodiment of the invention;

[0028] [Fig. 10] is a front view of a bladed rotor disc equipped with a cover according to a second embodiment of the invention in a section plane extending between the front face of the cover and the upstream face of the disc;

[0029] [Fig. 11] is a detailed view of the attachment of a cover to a rotor disk according to the second embodiment of the invention.

[0030] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0031] The idea behind the invention is to provide a dedicated cover to cover the ends of bolts so that they no longer form protrusions likely to cause the phenomenon of "barratting".

[0032] In [Fig. 2], a rotating element 11 which is here a turbomachine bladed disc comprises a hub 12 extending around a central axis AX delimited internally by a central opening 13 and externally by a circular external periphery 14 to which are fixed blades 16 regularly distributed around the axis AX. As will be understood, the terms internal and external are understood here relative to a radial direction with respect to the axis AX.

[0033] More generally, the rotor elements are annular, having a generally circular shape centered on the axis AX with possibly a repetitive shape distributed regularly around the axis AX. Such an element is rotationally balanced, or does not have excessive unbalance.

[0034] This bladed disc 11 is coupled to a rotor element (not shown), to which it is axially attached, being secured to the latter by a series of bolts 17 regularly distributed around the axis AX. These bolts extend parallel to the axis AX and pass through as many axial holes of the hub 12 located along a base circle having a diameter substantially smaller than that of the external periphery 14.

[0035] As seen more clearly in [Fig.3], each bolt 17 comprises a screw 18 receiving at its free end a nut 19 tightened on it to be pressed against an upstream axial delimiting face 21 of the hub 12.

[0036] When the disc 11 is rotating around the axis AX, that is to say when the turbine is in operation, the air located in the vicinity of the ends of the bolts 17 which protrude from the upstream face 21 swirls around these ends, forming vortices, which is represented schematically by arrows in [Fig.3].

[0037] These vortices correspond to a phenomenon known as “churning” of the air, which induces energy loss resulting in excess fuel consumption.

[0038] According to the invention, a cover 22 is provided fixed to the upstream face 21, which has a shape suitable for covering the ends of the bolts 17 protruding from this upstream face 21, which makes it possible to make the protuberances formed by these ends disappear.

[0039] As visible in [Fig.4], this cover 22 has a general crown shape presenting in section a shape corresponding to that of the letter U, in order to constitute a circular rail whose nominal diameter corresponds to the diameter of the base circle along which the bolts 17 are arranged, and which delimits with the face 21 an enclosed internal space.

[0040] This cover 22, which is for example made of stamped sheet metal, comprises a flat crown-shaped front wall 23, the inner edge of which is extended by a substantially cylindrical inner flank 24, and the outer edge of which is extended by a substantially cylindrical outer flank 26.

[0041] As visible in Figures 5 and 6, the cover comprises four fixing lugs 27, each lug extending the free edge of the internal flank 24 by extending towards the free edge of the external flank 26, so as to be oriented parallel to the front wall 23. These lugs 27, in the form of rectangular tongues, are here four in number, spaced from each other by 90° around the axis AX, make it possible to fix the cover to the upstream face 21 of the disc.

[0042] Each tab 27 has a central hole 28 engaging around a corresponding screw 18, which makes it possible to clamp this tab between the nut 19 and the upstream face 21. In addition, the front wall 23 of the cover 22 has an access hole 29, opposite each tab 27 in the direction AX, which makes it possible to access each end of this screw 18 passing through a tab 27 to engage the nut 19 thereon.

[0043] Starting from the situation in [Fig. 2], the mounting of the cover 22 on the disc 11 consists of removing four nuts 19 located at 90° to each other around the axis AX, then positioning the cover 22 parallel to the upstream face 21 by pivoting it around the axis AX to place the four tabs 27 opposite the screws 18 from which the nuts have been removed.

[0044] The cache 22 is then brought closer to the face 21 by moving it in the direction AX, to engage the screws 18 in the lugs 27, until the free edges of the sides 24 and 26 are pressed against the upstream face 21. At this stage, the four nuts 19 previously removed can be engaged around each screw 18 passing through a lug 27, by passing these nuts 19 through the corresponding access holes 29 formed in the front wall 23.

[0045] In practice, engaging a nut 19 through an access hole 29 may consist of placing this nut in the end of a pipe wrench, and engaging the end of the wrench in the access hole 29 while rotating it, to successively engage the nut on the end of the screw 18, then tighten it on this screw, which corresponds to the situation in [Fig.7].

[0046] As will be understood, when the four removed nuts have been replaced and tightened on the corresponding screws, they firmly grip the tabs 27, so that the cover 22 is firmly held on the upstream face 21 of the disc 11, of which it masks all the bolts 17.

[0047] Optionally, each access hole 29 is advantageously closed, so as to prevent the circulation of air inside the cover 22, which would be likely to allow “churning”.

[0048] This sealing can be ensured with a tubular cap 32 with a pierced bottom. More particularly, and as visible in [Fig.8], this cap 32 comprises a tubular body 33 extended at one end by a bottom 34 and at its other end by a rim 36.

[0049] The bottom 34 has the shape of a flat disc pierced in its center by a hole whose diameter corresponds to that of the screw 18, and the tubular body 33 has an internal diameter greater than that of the nut 19 and an external diameter corresponding to that of the access hole 29. The rim 36 which extends the tubular body 33 on the side opposite the bottom 34 has the shape of a flat crown whose external diameter is greater than that of the access hole 29.

[0050] From the assembly point of view, the caps 32 are first fitted into the corresponding access holes 29 of the cover 22, and the nuts 19 corresponding to the fixing lugs 27 are removed. At this stage, the cover 22 with the caps it carries is brought against the face 21, by engaging the screws 18 without nuts in the holes of the lugs 27 and the bottoms 34 in order to place it in its final position.

[0051] The nuts 19 are then engaged in the caps, for example using a pipe wrench, and tightened, so that the bottoms 34 and the tabs 27 are clamped between the nuts 19 and the face 21. Under these conditions, the internal space of the cover is closed on the one hand by the face 21, and on the other hand by the caps 32, so that it constitutes an enclosed space.

[0052] In the embodiment of Figures 4 to 7, the legs 27 each comprise a central hole 28 crossed by a fixing bolt. But this central hole can be replaced by a notch, as in the second embodiment of the invention visible in figures 9 and 10.

[0053] In this case, and as visible in [Fig.9], the tabs, marked 27', have notches 38'. More particularly, each tab 27' has the shape of a rectangular tongue delimited by two lateral edges and by an external edge. The notch 38' extends parallel to the circumferential direction, that is to say parallel to the external edge, and it opens into a lateral edge of the tongue.

[0054] These notches 38', which give the legs 27' a hook shape, all have the same orientation in the circumferential direction, that is to say that they all open into the right lateral edge of the leg which carries them when the latter is viewed from the central axis AX.

[0055] These notches 38' make it easier to fit the cover 22: starting from the situation in [Fig.2], it is sufficient first of all to significantly loosen four nuts 19 spaced 90° apart around the axis AX instead of having to remove them entirely.

[0056] After this operation, the cover 22 is presented opposite the bolts 17, positioning it around the axis AX so that each tab 27' is opposite the space circumferentially separating a loosened nut and the tightened nut which is located immediately to the left of this loosened nut when seen from the axis AX. The cover 22 is then brought closer to the disc 11 to press it against the face 21, before pivoting it clockwise, to engage the four notches 38' around the four screws 18 under the nuts 19 which have been loosened.

[0057] Once the cover 22 is in place, all that remains is to tighten the nuts 19 of the bolts 17 passing through each leg 27' to complete the assembly. Just as in the first embodiment, the cover 22 also has access holes 29 opposite each leg 27', in order to allow the passage of a pipe wrench allowing the gripping and tightening of the corresponding nut 19.

[0058] The access holes 29 of the cover can also be closed by making a welding point 37 on each hole 29 to fill it, after mounting the cover, as illustrated schematically in [Fig. 11].

[0059] Furthermore, as can be seen in the figures, the external flank of the cover 26 is advantageously extended by a crenellated rim 38 extending in a plane normal to the axis AX, with crenellation coinciding with the positions of the blades carried by the disk, so as to ensure axial locking of each blade root when the cover 22 is mounted.

[0060] The internal flank 24 is extended by a circular rim 39, the two rims 38 and 39 bearing on the face 21 when the cover 22 is in place and tightened.

[0061] In the examples of the figures, the ends of the bolts hidden by the cover are those corresponding to the ends of screws carrying the nuts, but the invention also applies to the other ends of these bolts, that is to say the ends corresponding to the heads of these screws.

[0062] Furthermore, in the examples of the figures, the cover has four fixing lugs on the front face of the disk, but the number of lugs may be different from this example, as it is conditioned by the environment and the operating conditions.

[0063] With regard to the mounting of the cover on an element fixed to the rotor as described on the basis of the examples of the figures, it is important to note that the cover can also be fixed to a stator element to mask ends of bolts fixing this element to another stator element. In particular, in the case of a rotor element fixed to another by bolts, the air driven in rotation about the longitudinal axis by a rotor is likely to undergo the phenomenon of "churning" by the ends of bolts fixing the stator element, which is why these ends of bolts can be covered by a cover in accordance with the invention.

[0064] The closure of the access holes to the clamping nuts can be ensured, as indicated above, by caps or welding points, or by any other suitable means allowing these access holes to be closed.

[0065] Generally speaking, the invention makes it possible to confine the ends of bolts in an enclosed space where air does not circulate, so as to cancel out losses by "churning", the shape and dimensioning of the cover being adapted according to the operating environment.

[0066] The cover according to the invention also provides thermal insulation of the peripheral region of the disc, which improves the cooling of the blade roots.

Claims

Claims

1. A turbomachine rotor comprising an element (11) secured to another element by a series of fixing bolts (17) distributed circumferentially around an axis of rotation (AX) of the rotor, each bolt (17) extending parallel to the axis of rotation (AX) and having one end projecting from an axial delimiting face (21) of the element (11), characterized in that it comprises an annular cover (22) which is fixed to the axial delimiting face (21) of the element (11) by bolts (17) and which covers the ends of the fixing bolts (17), in which the cover (22) comprises fixing lugs (27; 27'), each fixing lug (27; 27') being crossed by a fixing bolt (17) which clamps it against the axial delimiting face (21) of the element, and in which each leg (27;27') comprises a notch (38') crossed by a fixing bolt (17), each notch (38') having a circumferential orientation in the same direction to allow mounting of the cover (12) by rotation around the axis (AX).;

2. Rotor according to claim 1, in which each tab (27; 27') comprises a hole (28) crossed by a fixing bolt (17).

3. Rotor according to claim 1 or 2, in which the fixing lugs (27; 27') extend inside the cover (22), and in which the cover (22) comprises opposite each lug (27; 27') an access hole (29) to the fixing bolt (17) of this lug (27; 27').

4. A rotor according to claim 3, wherein each access hole (29) is closed by a weld point (37).

5. Rotor according to claim 3, in which each access hole (29) is closed by a tubular cap (32) engaged in this hole (29) and crossed by the corresponding bolt (17), each tubular cap (32) being held and tightened axially by a bolt (17).

6. Rotor according to one of the preceding claims, in which the cover (22) comprises a crown-shaped front wall (23) having an inner edge extended by an inner flank (24) and an outer edge extended by an outer flank (26), these flanks (24, 26) having a shape of revolution, each flank (24, 26) being terminated by a rim (38, 39) bearing on the axial delimiting face (21) of the element (11).

7. Rotor according to claim 6, in which the external flank (26) of the cover (22) is terminated by a rim (38) which is crenellated to axially block the root of each of the blades (16) carried by the element (11).

8. Turbomachine equipped with a rotor according to one of claims 1 to 7.

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