TURBOMACHINE COMPRISING A FAN CARRYING VARIABLE-PITCH BLADES

Abstract

A turbomachine with a longitudinal axis (X) comprising: - a fan comprising a disk carrying at least one variable-pitch blade about an axis of rotation (Y) of the blade which is substantially perpendicular to the axis (X); - a system (16a) for adjusting the blade pitch which comprises a mechanism (17a) configured to allow the adjustment of the blade pitch about the axis (Y) in a first direction of rotation (S1) and prevent the adjustment of the blade pitch about the axis (Y) in a second direction of rotation (S2) which is opposite to the first direction of rotation (S1), the adjustment system (16a) also comprising a locking device (18a) configured to occupy an active position in which the locking device (18a) locks the rotation of the blade in the first direction of rotation (S1) and a passive position in which the locking device (18a) releases the rotation of the blade in the first direction of rotation (S1). Figure for abstract: 2

Description

Title of the invention: TURBOMACHINE COMPRISING A FAN CARRYING VARIABLE-PITCH BLADES Technical field of the invention

[0001] The present invention relates to a turbomachine comprising a fan carrying variable-pitch blades. Technical background

[0002] A turbomachine may comprise a fan comprising a disk carrying an annular row of variable-pitch blades, i.e. blades whose pitch (and more precisely the pitch angle) is adjustable around an axis of rotation specific to each of the blades.

[0003] As a reminder, the pitch angle of a blade corresponds to the angle, in a plane perpendicular to the axis of rotation of the blade, between the chord of the blade blade and the plane of rotation of the fan.

[0004] The timing of the blades is adjusted via an adjustment system depending in particular on the flight parameters encountered by the turbomachine, so as to optimize its operation, and in particular its fuel consumption and its carbon dioxide emissions.

[0005] The adjustment system is generally specific to each of the blades and can take different forms.

[0006] For example, it is known to clamp the blades between two half-discs. The major drawback of such a solution is the appearance of a step at the interface between the two half-discs, in particular under the effect of centrifugal force. The presence of such a step obviously harms the performance of the turbomachine since it degrades in particular the air flow feeding the primary vein of the turbomachine.

[0007] To overcome the aforementioned drawback, it is also known to use a single-piece (or one-piece) disc and to report the different adjustment systems. The adjustment systems implemented are theoretically simple to use, but their installation in a compact and difficult-to-access environment generally makes the adjustment operations complex and tedious.

[0008] Engine manufacturers are therefore seeking to simplify adjustment systems as much as possible, in particular to reduce the time required to adjust the different blades.

[0009] The objective of the present invention is therefore to provide a simple, effective and economical solution making it possible to respond to the aforementioned problem. Summary of the invention

[0010] The invention thus proposes a turbomachine with longitudinal axis X comprising: - a fan comprising a disk carrying at least one variable-pitch blade around an axis of rotation Y of the blade which is substantially perpendicular to the axis X; - a blade timing adjustment system which comprises a mechanism configured to allow adjustment of the blade timing around the Y axis in a first direction of rotation SI and prevent adjustment of the blade timing around the Y axis in a second direction of rotation S2 which is opposite to the first direction of rotation SI, the adjustment system also comprising a locking device configured to occupy an active position in which the locking device locks the rotation of the blade in the first direction of rotation SI and a passive position in which the locking device releases the rotation of the blade in the first direction of rotation SI.

[0011] Such an adjustment system relies on a simple and reliable mechanism which is notably integrated into the freewheels (for example of a bicycle) to allow the transmission of power in one direction of rotation and the disengagement in the other. The adjustment of a blade is now limited to the control of the locking device between its active position and its passive position, which considerably reduces the manipulations necessary to adjust the timing of a blade, to the benefit in particular of the overall time to adjust all the blades.

[0012] The turbomachine according to the invention may comprise one or more of the characteristics, taken in isolation from one another or in combination with one another: - the blade comprises an aerodynamic blade and a pivot mounted in an opening of the disc so as to guide the blade in rotation around the Y axis, the adjustment system being radially internal with respect to the pivot with reference to the X axis; - the mechanism comprises a ratchet secured to the blade and a crown secured to the disc, the ratchet being engaged with internal teeth of the crown; - the mechanism comprises several pawls secured to the blade and distributed regularly around the Y axis, the pawls each being engaged with the internal teeth of the crown; - the locking device comprises a stop adjustable between the active position in which the stop is engaged with the inner teeth and the passive position in which the stop is spaced from the inner teeth, so as to release the rotation of the blade in the first direction of rotation SI; - the mechanism includes: — a cam attached to the blade which is placed in a drum attached to the disc; — at least one first rolling element placed in a first peripheral notch of the cam so that the first rolling element is located between the cam and the drum; — a first pusher housed at least partly in the cam and bearing against the first rolling element under the action of a first return spring; - the locking device includes: — at least one second rolling element placed in a second peripheral notch of the cam so that the second rolling element is located between the cam and the drum; — a second pusher housed at least partly in the cam and bearing against the second rolling element under the action of a second return spring; - the locking device is configured to move from the active position to the passive position under the action of a tool attached to the system which stresses the second rolling element with a contact force whose direction is opposite to that of the return force of the second spring and the intensity is greater than that of the return force of the second spring, so as to release the rotation of the blade in the first direction of rotation S1; - the locking device is configured to move from the active position to the passive position under the action of a magnet placed near the locking device, the second pusher being made of a ferromagnetic material, the magnet exerting a magnetic force on the second pusher whose direction is opposite to that of the return force of the second spring and the intensity is greater than that of the return force of the second spring, so as to release the rotation of the blade in the first direction of rotation S1; - the fan is located axially at an upstream end of the turbomachine with reference to the X axis.

[0013] The present invention also relates to an aircraft comprising a turbomachine as described previously. Brief description of the figures

[0014] The invention will be better understood and other details, characteristics and advantages of the invention will appear more clearly on reading the following description given by way of non-limiting example and with reference to the appended drawings in which:

[0015] [Fig-1] [Fig.l] is a schematic view in longitudinal half-section of a turbomachine comprising an adjustment system according to a first embodiment of the invention;

[0016] [Fig.2] [Fig.2] is a schematic cross-sectional view of the adjustment system of [Fig.l], the locking device of the adjustment system being in an active position;

[0017] [Fig.3] [Fig.3] is a view similar to that of [Fig.2] in which the device locking is in a passive position;

[0018] [Fig.4] [Fig.4] is a schematic view in longitudinal half-section of a turbomachine comprising an adjustment system according to a second embodiment of the invention;

[0019] [Fig.5] [Fig.5] is a schematic cross-sectional view of the system of adjustment of [Fig.4], the locking device of the adjustment system being in an active position;

[0020] [Fig.6] [Fig.6] is a view similar to that of [Fig.5] in which the device locking is in a passive position. Detailed description of the invention

[0021] In Figures 1 and 4, a turbomachine 1 with a longitudinal axis X is schematically represented. The turbomachine 1 comprises an unducted propulsive fan 2 and an unducted fixed rectifier 3. Such a turbomachine 1 is better known by the English acronym USF for “Unducted Single Fan”.

[0022] As illustrated in Figures 1 and 4, the fan 2 is driven in rotation about the axis X by a motor 4 arranged downstream of the fan 2. Such an arrangement of the turbomachine 1 is better known under the designation “tractor” in French or “puller” in English. In such an arrangement, the rectifier 3 is arranged longitudinally downstream of the fan 2.

[0023] The examples illustrated in Figures 1 and 4 are in no way limiting, the turbomachine 1 could for example comprise an unducted fan arranged downstream of the engine, or a ducted fan arranged upstream or downstream of the engine, or even two counter-rotating fans (ducted or not) arranged upstream or downstream of the engine.

[0024] The turbomachine 1 is defined along the longitudinal axis X which corresponds to the axis of rotation of the fan 2.

[0025] By convention in the present application, the terms “upstream” and “downstream” are defined in relation to the direction of circulation of the gases at the level of the turbomachine 1.

[0026] The engine 4 here comprises a gas generator and at least one power turbine (or low pressure turbine) which is intended to drive the fan 2 in rotation. The gas generator conventionally comprises, from upstream to downstream, at least one compressor, a combustion chamber, at least one expansion turbine (or high pressure turbine) which is coupled in rotation with the compressor. The gas generator is supplied with air by an air inlet which opens between the fan 2 and the rectifier 3.

[0027] As illustrated in Figures 1 and 4, the fan 2 comprises a disk 5 carrying an annular row of variable-pitch blades 6a, 6b. The pitch of each blade 6a, 6b is adjustable about an axis of rotation Y which is specific to the blade 6a, 6b and which is substantially perpendicular to the axis X. The disk 5 of the fan 2 is annular about the axis X and monobloc (or in one piece). The disk 5 is driven by the power turbine via a transmission shaft 7 centered on the axis X and a transmission member 8 coupled in rotation with both the transmission shaft 7 and the disk 5. The fan 2 also comprises a domed inlet cowl 9 which is secured to the disk 5 via an annular row of screws 10 around the axis X.

[0028] As illustrated in Figures 1 and 4, each blade 6a, 6b of the fan 2 comprises an aerodynamic blade 11 delimited by a root 12a, 12b which is mounted in the disk 5. More precisely, the root 12a, 12b of each blade 6a, 6b comprises a pivot 13 mounted directly or indirectly in an opening 14 of the disk 5 so as to guide the blade 6a, 6b in rotation about its axis Y. One or more bearings (smooth bearing or rolling bearing) may be placed between the wall defining the opening 14 and the pivot 13 so as to facilitate its guidance.

[0029] The rectifier 3 comprises an annular row of fixed blades 15. The rectifier 3 has the function of straightening the air flow generated by the fan 2.

[0030] The timing of each blade 6a, 6b is adjusted via an adjustment system 16a, 16b which is specific to each of the blades 6a, 6b. Such adjustment of the timing can be carried out throughout the lifetime of the turbomachine 1, namely for example during assembly of the turbomachine, during tests on the turbomachine, or during maintenance of the turbomachine.

[0031] According to the invention, the adjustment system 16a, 16b comprises a mechanism 17a, 17b configured to allow the adjustment of the setting of the blade 6a, 6b around its axis Y in a first direction of rotation S1 and prevent the adjustment of the setting of the blade 6a, 6b around its axis Y in a second direction of rotation S2 which is opposite to the first direction of rotation SL. The adjustment system 16a, 16b also comprises a locking device 18a, 18b configured to occupy an active position in which the locking device 18a, 18b locks the rotation of the blade 6a, 6b in the first direction of rotation S1 and a passive position in which the locking device 18a, 18b releases the rotation of the blade 6a, 6b in the first direction of rotation SL.

[0032] Such an adjustment system relies on a simple and reliable mechanism which is notably integrated into freewheels (for example of a bicycle) to allow the transmission of power in one direction of rotation and the disengagement in the other. The adjustment of a blade is now limited to the control of the locking device between its active position and its passive position, which considerably reduces the manipulations necessary to adjust the timing of a blade, in particular to the benefit of the overall time to adjust all the blades.

[0033] Advantageously, the adjustment system 16a, 16b is radially internal relative to the pivot 13 of the blade 6a, 6b with reference to the axis X. Such positioning makes it possible to take advantage of the space available inside the disc without impacting the air flow.

[0034] According to the first embodiment illustrated in Figures 1 to 3, the mechanism 17a comprises six pawls 19 secured to the blade 6a and a crown 20 secured to the disc 5, the pawls 19 being engaged with internal teeth 21 of the crown 20. The pawls 19 are distributed regularly around the axis Y. The pawls 19 are mounted on a ring 22 which is itself mounted tightly on an end 23 of the root 12a of the blade 6a. Each pawl 19 is forced to engage with the internal teeth 21 of the crown 20 under the action of a leaf spring 24 associated with it. The pawls 19 ensure the axial retention of the blade 6a relative to the disc 5 with reference to the Y axis. The diameter of the opening 14 is here substantially equal to the external diameter of the ring 22. When mounting the blade 6a, the blade 6a is inserted into the opening 14 from the outside and the pawls 19 are folded inwards to allow their passage through the opening 14.The crown 20 is for example fixed to the disc 5 via an annular row of screws around the Y axis.

[0035] Alternatively, the mechanism 17a could comprise a single pawl 19 or a different number of pawls 19 (for example three or four).

[0036] The ratchet mechanism 17a is here configured to allow the adjustment of the timing of the blade 6a around its axis Y in a first direction of rotation SI (clockwise) and to prevent the adjustment of the timing of the blade 6a around its axis Y in a second direction of rotation S2 (counterclockwise) which is opposite to the first direction of rotation SL.

[0037] The mechanism 17a makes it possible in particular to take up the aerodynamic forces exerted on the blade 11 of the vane 6a.

[0038] In certain configurations (in particular when a blade 6a has a large dimension between its Y axis and its trailing edge (or its leading edge)), it is not possible to turn the blade 6a around its Y axis through 360 degrees because it interferes with the directly adjacent blades 6a. Thus, for these configurations, it is necessary to be able to unlock the pawls 19 to release the rotation of the blade 6a in the second direction of rotation S2.

[0039] To address the aforementioned problem, the pawls 19 can each be provided with a boss, and folded together inwards using a tool which cooperates with the different bosses. The tool can be in the form of a split ring (circlip type) which is deformable via pliers.

[0040] According to the first embodiment illustrated in Figures 1 to 3, the locking device 18a comprises a stop 25 adjustable between the active position ([Fig.2]) in in which the stop 25 is engaged with the internal teeth 21 and the passive position ([Fig.3]) in which the stop 25 is spaced from the internal teeth 21, so as to release the rotation of the blade 6a according to the first direction of rotation SI. The stop 25 is housed partly in an orifice 26 of the ring 22. The stop 25 is constrained under the action of a coil spring 27 placed between the bottom of the orifice 26 and the stop 25.

[0041] The locking device 18a makes it possible in particular to counteract existing vibratory forces and clearances.

[0042] The transition from the passive position ([Fig.3]) to the active position ([Fig.2]) is done by removing a stop member 28 (for example a pin) from its housing 29 which is partly formed in the stop 25 and partly formed in the ring 22.

[0043] The transition from the active position ([Fig.2]) to the passive position ([Fig.3]) is done by placing or replacing the stop member 28 in its housing 29.

[0044] The stop 25 may comprise a grip (for example a handle) so as to facilitate the resetting of the stop 25 when this is carried out manually by an operator.

[0045] Alternatively, the stop 25 can be electrically controlled.

[0046] The adjustment system 16a may comprise several stops 25 which are preferably distributed regularly around the Y axis.

[0047] According to a variant not shown, each notch in which a pawl 19 and a leaf spring 24 are mounted is symmetrical, so as to be able to mount each pawl in two opposite positions.

[0048] This characteristic is particularly advantageous in the case where tests are carried out in different operating modes (in particular “propulsor” mode and “inverter” mode).

[0049] Indeed, depending on the operating modes (in particular “propulsor” mode and “reverser” mode), the forces exerted on the blades differ. Thus, for example, for tests in “propulsor” mode, the pawls are mounted in a first position, and for tests in “reverser” mode the pawls are mounted in a second position (opposite to the first position).

[0050] According to another variant not shown, the adjustment system comprises one or more first pawls mounted in a first position and one or more second pawls mounted in a second position (opposite the first position), the second pawl(s) thus being mounted in opposition to the first pawl(s).

[0051] Such an adjustment system makes it possible in particular to carry out tests in different operating modes (in particular “propulsor” mode and “inverter” mode).

[0052] Advantageously, the adjustment system comprises more ratchets configured to take up the forces exerted on the blade in “propulsor” mode. As for example, when the adjustment system comprises six pawls, four of them can be in the first position to take up the forces in “propulsor” mode, and two of them can be in the second position to take up the forces in “reverser” mode.

[0053] To adjust a blade associated with such an adjustment system, the pawls can each be provided with a boss, and folded together inwards using a tool which cooperates with the different bosses. The tool can be in the form of a split ring (circlip type) which is deformable via pliers.

[0054] According to the second embodiment illustrated in Figures 4 to 6, the mechanism 17b comprises: - a cam 30 secured to the blade 6b which is placed in a drum 31 secured to the disc 5; - a first rolling element 32 placed in a first peripheral notch 33 of the cam 30 so that the first rolling element 32 is located between the cam 30 and the drum 31; - a first pusher 34 housed at least partly in the cam 30 and bearing against the first rolling element 32 under the action of a first return spring 35.

[0055] The cam 30 is coupled in rotation with the blade 6b via complementary grooves 36 formed both in the cam 30 and in a grooved portion 37 of the root 12b of the blade 6b. The mechanism 17b here comprises a single first rolling element 32. The first rolling element 32 may be solid or hollow. The first rolling element 32 may be in the form of a ball or a roller, for example. The first notch 33 is in the form of a ogive. The first notch 33 has a radial dimension RI which increases in the first direction of rotation SI with reference to the Y axis. The axial retention of the blade 6b relative to the disk 5 with reference to the Y axis is obtained by a nut 38 screwed onto a threaded end 39 of the root 12b ([Fig.4]). The drum 31 is for example fixed to the disc 5 via an annular row of screws around the Y axis.

[0056] Alternatively, the mechanism 17b could comprise several first rolling elements 32, each first rolling element 32 being associated with a first notch 33, a first pusher 34 and a first return spring 35.

[0057] The rolling element mechanism 17b is here configured to allow the adjustment of the timing of the blade 6b around its axis Y in a first direction of rotation SI (counterclockwise) and to prevent the adjustment of the timing of the blade 6b around its axis Y in a second direction of rotation S2 (clockwise) which is opposite to the first direction of rotation SL.

[0058] According to the second embodiment illustrated in Figures 4 to 6, the locking device 18b comprises: - at least one second rolling element 40 placed in a second peripheral notch 41 of the cam 30 so that the second rolling element 40 is located between the cam 30 and the drum 31; - a second pusher 42 housed at least partly in the cam 30 and bearing against the second rolling element 40 under the action of a second return spring 43.

[0059] The locking device 18b comprises a single second rolling element 40. The second rolling element 40 may be solid or hollow. The second rolling element 40 may be in the form of a ball or a roller, for example. The second notch 41 is in the form of a ogive. The second notch 41 has a radial dimension R2 which decreases in the first direction of rotation S1 with reference to the Y axis.

[0060] The locking device 18b can be configured to move from the active position ([Fig.5]) to the passive position ([Fig.6]) under the action of a tool attached to the system 16b which stresses the second rolling element 40 with a contact force whose direction is opposite to that of the return force of the second spring 43 and the intensity is greater than that of the return force of the second spring 43, so as to release the rotation of the blade 6b in the first direction of rotation SL When the second rolling element 40 is hollow, the tool can be inserted into the second rolling element 40 in order to apply the aforementioned contact force.

[0061] The locking device 18b can be configured to move from the active position ([Fig.5]) to the passive position ([Fig.6]) under the action of a magnet placed near the locking device 18b, the second pusher 42 being made of a ferromagnetic material, the magnet exerting a magnetic force on the second pusher 42 whose direction is opposite to that of the return force of the second spring 43 and the intensity is greater than that of the return force of the second spring 43, so as to release the rotation of the blade 6b in the first direction of rotation SL A ferromagnetic material is receptive to a magnet and will therefore be attracted by the magnet.

Claims

Claims

1. Turbomachine (1) with longitudinal axis (X) comprising: - a fan (2) comprising a disk (5) carrying at least one variable-pitch blade (6a) around an axis of rotation (Y) of the blade (6a) which is substantially perpendicular to the axis (X);- an adjustment system (16a) for the timing of the blade (6a) which comprises a mechanism (17a) configured to allow the adjustment of the timing of the blade (6a) around the axis (Y) in a first direction of rotation (SI) and prevent the adjustment of the timing of the blade (6a) around the axis (Y) in a second direction of rotation (S2) which is opposite to the first direction of rotation (SI), the adjustment system (16a) also comprising a locking device (18a) configured to occupy an active position in which the locking device (18a) locks the rotation of the blade (6a) in the first direction of rotation (SI) and a passive position in which the locking device (18a) releases the rotation of the blade (6a) in the first direction of rotation (SI), the mechanism (17a) comprising a pawl (19) secured to the blade (6a) and a crown (20) secured to the disc (5), the pawl (19) being engaged with inner teeth (21) of the crown (20).;

2. Turbomachine (1) according to claim 1, characterized in that the blade (6a) comprises an aerodynamic blade (11) and a pivot (13) mounted in an opening (14) of the disc (5) so as to guide the blade (6a) in rotation around the axis (Y), the adjustment system (16a) being radially internal relative to the pivot (13) with reference to the axis (X).

3. Turbomachine (1) according to one of claims 1 or 2, characterized in that the mechanism (17a) comprises several pawls (19) integral with the blade (6a) and distributed regularly around the axis (Y), the pawls (19) each being engaged with the internal teeth (21) of the crown (20).

4. Turbomachine (1) according to one of claims 1 to 3, characterized in that the locking device (18a) comprises a stop (25) adjustable between the active position in which the stop (25) is engaged with the internal teeth (21) and the passive position in which the stop (25) is spaced from the internal teeth (21), 11 way to release the rotation of the blade (6a) according to the first direction of rotation (SI).

5. Turbomachine (1) according to one of the preceding claims, characterized in that the fan (2) is located axially at an upstream end of the turbomachine (1) with reference to the axis (X).

6. Aircraft comprising a turbomachine (1) according to one of the preceding claims.

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