FR3125505A1 - TURBOMACHINE PROPELLER BLADE PITCH CHANGE SYSTEM - Google Patents

Abstract

The invention relates to a system (30) for changing the pitch of a blade of a propeller, for an aircraft turbine engine, characterized in that it comprises a support (40) for the root (25) of the blade comprising a annular wall (42) extending around an axis (A) intended to be a wedging axis of the blade, this annular wall comprising a lower axial end closed by a bottom wall (44) and an open upper axial end and configured to allow the mounting of a blade root, the bottom wall (44) comprising an upper face configured to cooperate by shape complementarity with a free end of the root so that the support is integral in rotation with the foot around said axis (A) and a lower face opposite the upper face comprising a transverse extension (48), the transverse extension having one end fixed integrally to a yoke (49) forming an eccentric (50) configured to cooperate with a mechanism of step change. Figure for abstract: Figure 9

Description

TURBOMACHINE PROPELLER BLADE PITCH CHANGE SYSTEM

The present invention relates to the field of aircraft turbomachines, and in particular the propulsion propellers of these turbomachines which include variable-pitch blades.

Changing the pitch or variable pitch of the blades of a turbomachine propeller is one of the ways to improve the performance and efficiency of turbomachines in different flight conditions.

It is known turbomachines comprising at least one unducted propeller, also called under the English term "open rotor" or "unducted fan", equipped with these pitch change systems. In this category of turbomachine, there are those with two unducted and counter-rotating propellers (known by the acronym UDF for "UnDucted Fan") or those with a single unducted propeller and a stator comprising several variable-pitch stator vanes (known by the USF acronym for "Unducted Single Fan").

An open rotor type turbomachine mainly comprises, inside a fixed cylindrical casing carried by the structure of the aircraft, a coaxial "gas generator" part and a "propulsion" part. The gas generator part can be arranged upstream or downstream of the propulsion part. The terms “upstream” and “downstream” are defined with respect to the circulation of gases in the turbomachine. The propulsion part comprises at least one propeller driven in rotation by a turbine, in particular low pressure, of the gas generator part via a reducer, for example, with planetary gears. In some cases, the propulsion part may comprise two coaxial and counter-rotating propellers, respectively upstream and downstream which are driven, in opposite rotation to one another, by the turbine of the gas generator via the reducer. The propeller or propellers extend substantially radially with respect to the longitudinal axis transmission shaft outside the casing.

There illustrates such an example of a UDF-type turbomachine. The turbomachine 10 comprises a casing 12 in which is arranged a gas generator which comprises, from upstream to downstream, a set of compressors 13, a combustion chamber 14 and a set of turbines 15. A nozzle 18 is arranged downstream of the gas generator.

The set of compressors 13 can comprise one or two compressor(s) depending on the architecture of the single or double stage gas generator(s). The set of turbines 15 can comprise a high pressure turbine and a low pressure turbine, or two turbines (high pressure and intermediate pressure) and a low pressure turbine. The gas generator drives the low pressure turbine around a rotor shaft with longitudinal axis Z.

The turbomachine comprises a pair of contra-rotating propellers with a 16 upstream propeller and a 17 downstream propeller. These two upstream 16 and downstream 17 propellers are driven in rotation in a counter-rotating manner by the low pressure turbine via a mechanical transmission device 19. The upstream 16 and downstream 17 propellers are mounted coaxially to the longitudinal axis Z of the turbomachine 10 and are arranged in parallel radial planes, which are perpendicular to the longitudinal axis Z. In the present example, the propellers 16, 17 are mounted downstream of the gas generator. The mechanical transmission device 19, shown here schematically, can comprise a differential reduction gear or a planetary gear box. It is of course possible to directly drive the upstream 16 and downstream 17 propellers by the low pressure turbine.

According to the configuration described above, the flow of air, denoted F, entering the turbomachine is compressed in the set of compressors 13, then mixed with fuel and burned in the combustion chamber 14. The combustion gases generated then pass through the turbines 15 to drive, via the mechanical transmission device 19, the propellers 16, 17 in reverse rotation which provide most of the thrust. The combustion gases are expelled through the nozzle 18 participating in the thrust of the turbomachine 10. The gases pass through a primary gas flow stream 20 extending substantially axially in the turbomachine between the nacelle 2 and an associated median casing 21 to the gas generator.

In the present example, the upstream propeller 16 comprises a rotating cylindrical casing with respect to the casing 12 of the turbomachine around a rotor shaft of longitudinal axis Z. The casing is also linked to a corresponding part of the device mechanical transmission 19. The casing comprises a polygonal ring 21 in which are formed radial housings 22 and radial passages which are coaxial The blades 25 extend radially outside the nacelle 12. The radial housings 22 here are cylindrical regularly distributed over the periphery of the polygonal ring 21 and receive the feet 24 of the blades 25.

The blades 25 of the upstream and downstream propellers are of the variable-pitch type, that is to say they can be oriented around their pitch axes denoted A, thanks to a system 30 for changing the pitch of the blades, so as to that these occupy an optimal angular position according to the operating conditions of the turbine engine and the flight phases concerned. The pitch axis A is the axis of elongation of the blade around which the angular position of the blade is adjusted. It is generally also a radial axis which therefore extends along a radius relative to the axis of rotation of the propeller equipped with this blade.

An example of the prior art of such a pitch change system is illustrated in Figures 2 to 4 for an open rotor turbomachine of the UDF type.

Generally, each propeller comprises a substantially cylindrical rotating casing 2A carrying an outer polygonal ring hub 4A rotatably received around the longitudinal axis in the fixed casing 6A. The hub comprises radial cylindrical housings 8A distributed over its periphery around the longitudinal axis Z. Shafts with radial axes 10A, perpendicular to the longitudinal axis of the turbomachine Z, integral with the feet 12A of the blades 14A are received in the housings of the polygonal rings and also pass through radial passages of the rotating cylindrical housing.

To allow optimum operation of the turbomachine according to the different flight phases encountered, the blades of the contra-rotating propellers can rotate in the radial housings of the rings. For this, they are driven in rotation around their respective pivot axes, called pitch axis denoted A, by an appropriate system making it possible to vary the pitch of the blades during flight, that is to say the pitch of the blades. propellers.

This system for changing the pitch of the blades of the propellers covers an angular range of rotation comprised between two extreme positions, namely an extreme position called "reverse" for which the blades exceed for example by 30° the plane transverse to the axis of the turbomachine (the direction of advance of the aircraft) to participate in the braking of the aircraft, in the manner of the usual thrust reversers, and an extreme position called "feathering" for which the blades are then erased as best as possible relative to the direction of advance of the aircraft, for example, in the event of an engine failure and thus offer the least resistance (drag) possible. The angular travel of the blades between the flag and reverse positions is for example of the order of approximately 120°.

In general, a system 20A for changing the pitch of the blades of a propeller comprises a control means 22A, of the cylinder actuator type 22A, and a link mechanism 24A connecting the control means to each blade of the propeller to ensure the desired angular pivoting of the blades.

Various solutions have been proposed for changing the pitch of the blades of the propellers on turbomachines of the “open rotor” or other type.

For example, document FR 2 908 451 discloses a turbomachine whose system for changing the orientation of the blades of each propeller advantageously comprises a single annular jack mounted by its cylinder, on the ring hub of the propeller, while that its piston is connected, by a connecting mechanism of the system associated with the jack, to the feet of the various blades. The displacement of the piston as a result of the fluidic control of the annular cylinder ensures the desired angular pivoting of the blades by the link mechanism by varying their pitch.

Document WO 2013/050704 also discloses another pitch change system for a propeller turbine engine for an aircraft comprising a single annular jack arranged on a fixed casing or internal stator with respect to the hub of the propeller and a connection comprising a transfer bearing fixed on one side to the movable part of the cylinder and cooperating, on the other side, with a means for connecting the mechanism to the blades of the rotary hub, in such a way that the transfer bearing of the driven mechanism in rotation transmits the translational movement of the movable part of the fixed actuator, to the connecting means of the rotary mechanism to change the orientation of the blades of the propeller.

An example of such a system for changing the blade pitch of a propeller of an open rotor type turbomachine is illustrated in the . In this example, the actuator rod is in its extended position corresponding to the flag position of the blades. The connecting mechanism 24A comprises connecting rods 26A articulated distributed around the annular actuator 28A and connected on one side to the piston 30A and on the other side to the radial shafts 10A integral with the feet of the blades of the propeller, so as to drive, as a result of the translational movement of the connecting rods of the connecting mechanism, the rotation of the radial shafts and the associated blades. Such a connecting mechanism with connecting rods guarantees operational safety and reliability in use without the parts sliding and/or rubbing relative to each other.

More precisely in order to achieve this kinematic connection, each link 26A comprises a link 32A and an eccentric 34A. One end of the link 32A is connected to the piston 30A and the other end is connected to one end of the eccentric 34A by a pivot connection with an axis parallel to the radial pitch axis A of the associated blade while the other end of the eccentric is connected to the radial shafts 10A secured respectively to the roots of the blades of the propeller.

The connection of the rods to the eccentrics makes it possible to transform the translational movement of the cylinder into a rotational movement of the blade. This transformation is carried out by the eccentric allowing by a lever arm effect to transmit the necessary torque to the propeller and thus to drive it in rotation.

This torque is then transmitted to the blade root by a splined connection 36A formed between the external surface of the end portion of the radial shaft 10A and in the internal bore of a splined hub 38A ( ), the splined hub being clutched inside a blade root bearing.

The radial shafts 10A pass through at least one primary air stream 40A in which hot air circulates between the splined connection 36A and the eccentric 34A visible on the .

Consequently, the assembly of such an assembly must be carried out by the interior of the vein (according to the arrow F1) because of the low master torque of the arm 42A present in the primary vein 40A, by not allowing an eccentric to pass as shown on the which represents a view in section AA of the .

On the other hand, the splined connection which makes it possible to transmit the torque has the disadvantage of bringing a pivoting point causing a misalignment in the connection with the rod. This effect is all the more present because of the length of the radial shaft on an open rotor type UDF architecture. However, the balling effect was interesting to accommodate the differential displacements due to the temperature delta between the upper and lower zones of the vein.

In the case of a USF type open rotor turbomachine, as illustrated in the , the hub ratio and fan diameter are smaller. In such a turbomachine 100, the propulsion part comprises a propeller 112 driven in rotation by a turbine and a rectifier 114 comprising several variable-pitch stator vanes 122 . Thus, the air inlet for the primary flow is downstream of the upstream rotor propeller 112 which is provided with vanes 120 with variable pitch. There is no crossing of a vein between the connection at the blade root and the eccentric. Consequently, the height of the radial shaft is much smaller than for a UDF type turbomachine as illustrated in FIGS. 1 to 4. The primary stream inlet is upstream of the rectifier 114 and the pitch change system is in the cold part of the turbomachine, around the compressor. For the stator vane of the stator 114, the radially available space is reduced between the primary flow in the compressor and the exterior where the flow circulates between the vanes 120 and 122.

There schematically illustrates a transposition of the binding mechanism of the to a USF-type turbomachine environment, which the invention proposes to improve.

Here, the blade root for USF is modified by having a shape qualified as “tulip root” or “bulb root”. An implantation radius R of the connecting rod 32A is relatively small to ensure as much volume as possible for the actuator comprising the cylinder 28A.

In addition, the assembly of this pitch change system must also be carried out from the inside of the vein (according to the arrow F2), because the diameter D of the shaft of the hub 44A imposes the maximum dimensions for passing an eccentric such as 'shown in the sectional view depicted in the upper part of the corresponding to the for a USF-type turbomachine environment.

There is a view in the BB section plane of the and a partial exploded view which illustrates this even more restricted radial size due to the low hub ratio. The partial exploded view in the figure is between the foot 12A and the eccentric 34A to simplify as much as possible the . However, it is necessary to have an implantation radius R of the rod 32A as large as possible in order to optimize the lever arm L of the eccentric 34A and to transmit the necessary torque from the cylinder to the blade. The splined connection 36A is therefore penalizing for integrating this optimal eccentric length.

In addition, the engine environment does not require swiveling because the differential displacements mentioned for UDF type turbomachines have much less impact since the assembly is arranged only under the vein.

The aim of the present invention is to remedy these drawbacks and to propose a system for changing the pitch of the blades of the propeller, the design of the eccentric of which makes it possible to maximize the length of the lever arm.

To this end, the invention relates to a system for changing the pitch of a blade of a propeller, for an aircraft turbine engine, characterized in that it comprises a blade root support comprising an annular wall extending around an axis intended to be a blade wedging axis, this annular wall comprising a lower axial end closed by a bottom wall and an open upper axial end configured to allow the mounting of a blade root, the bottom wall comprising an upper face configured to cooperate by form complementarity with a free end of the foot so that the support is integral in rotation with the foot around said axis and a lower face opposite the upper face comprising an extension transverse, the transverse extension having one end fixed integrally to an eccentric yoke configured to cooperate with a pitch change mechanism.

Such a system makes it possible to merge the functions of blade root support and eccentric allowing the length of the lever arm to be reported in order to facilitate its integration in particular.

This configuration maximizes the radius of implantation of the eccentric function allowing to maximize the length of the lever arm. This is thus optimized, because it is decisive for sizing the actuating jack of the kinematics for setting the blades of the propeller.

Thanks to the attached lever arm, mounting of the blade root support assembly is thus possible from the outside of the vein.

In addition, the splined connection or any other type of connection between the radial shaft and the blade root greatly reduces the complexity of the system, increases its reliability and frees up space radially. The implantation radius of the rods can therefore be increased, making it possible to lengthen the lever arm accordingly.

The system according to the invention may comprise one or more of the following characteristics, taken separately from each other, or according to all the technically possible combinations with each other:

- the transverse extension comprises a boss provided at a free end of the extension, presenting a contact surface transverse to the axis and configured to receive one end of the yoke;

- the contact surface of the boss has a substantially elliptical shape and the end of the yoke fixed to the boss has a shape complementary to the contact surface of the boss;

- the transverse extension comprises a facial abutment extending in a plane parallel to the axis and the yoke comprises a shoulder configured to bear against the facial abutment of the transverse extension;

- The yoke is fixed integrally to the boss of the transverse extension by at least one bolted connection, preferably of the screw-nut type;

- the end of the yoke fixed to the boss has at least one through hole and the boss has at least one through hole in the contact surface arranged opposite a through hole of the yoke, each screw of a bolted connection being successively inserted into a through hole in the yoke and a through hole in the boss;

- the yoke comprises an extension extending along the axis and comprising at least one through hole with an axis perpendicular to the axis, and the transverse extension of the foot support comprises a wall extending along the axis in which is formed at least one through hole arranged opposite a through hole in the yoke, and having a bearing surface configured to receive the extension of the yoke, each screw of a bolted connection being inserted successively in a through hole in the yoke and a through hole in the transverse extension of the foot support;

- the yoke comprises two parallel arms connected by a central portion, the central portion comprising at least one through hole with an axis transverse to the axis, and the transverse extension of the foot support comprises at least one through hole arranged opposite a through hole in the yoke, each screw of a bolted connection being inserted successively into a through hole in the yoke and a through hole in the transverse extension of the foot support;

- the lower face opposite the upper face comprises a cylindrical extension extending along the axis between the bottom wall and the transverse extension.

The present invention also relates to an assembly comprising a pitch control system as described above and a variable-pitch propeller blade controlled by said system.

The present invention also relates to a turbine engine, in particular for an aircraft, comprising at least one system or an assembly as described above.

In particular, the turbomachine may be of the open rotor type in which the propeller is unducted.

The turbomachine may also be of the USF type comprising a single unducted propeller and a rectifier comprising several stator vanes.

The present invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the description of a non-limiting example which follows, with reference to the appended drawings in which:

there , already described, schematically represents in axial section an example of an open rotor type turbomachine with a system for changing the pitch of the blades of a propeller to which the invention can be applied;

there , already described, is a partial axial half-section of a turbine engine with an unducted fan of the open rotor type according to an example of the prior art, showing a system for changing the pitch of the blades of a propeller according to an example of the prior art;

there , already described, represents an enlarged view of a link mechanism equipping the pitch change system of the ;

there , already described, is a sectional view of the , according to an AA plan;

there , already described, is a schematic perspective view of a USF-type turbomachine

there , already described, is a schematic axial half-section showing a system for changing the pitch of the blades of a propeller of the USF type turbomachine such as that of the ;

there , already described, is a schematic sectional view of the , along a radial plane BB;

there shows a view in perspective and in partial section of a system for changing the pitch of a blade of a propeller fitted to a USF-type turbomachine according to the invention;

there illustrates an exploded perspective view of a system blade root support ;

there illustrates a cross-sectional view along the pitch axis of the blade root support of the system of the ;

there illustrates a top view of the blade root support of the system of Figures 9 and 10;

there illustrates a comparison of the bulk between a pitch change system according to the invention and that of the prior art;

there illustrates a comparison of the length of the lever arm between a pitch change system according to the invention and that of the prior art;

there shows a sectional view along the pitch axis of an alternative to the blade root support of the system of the ; And

there shows a sectional view along the pitch axis of another alternative to the blade root support of the system of the .

The elements having the same functions in the different implementations have the same references in the figures.

Claims (10)

System (30) for changing the pitch of a blade of a propeller, for an aircraft turbine engine, characterized in that it comprises a support (40) for the root (25) of the blade comprising an annular wall (42) extending around an axis (A) intended to be a wedging axis of the blade, this annular wall comprising a lower axial end closed by a bottom wall (44) and an upper axial end open and configured to allow the mounting of a blade root, the bottom wall (44) comprising an upper face configured to cooperate by form complementarity with a free end of the root so that the support is integral in rotation with the root around said axis ( A) and a lower face opposite the upper face comprising a transverse extension (48), the transverse extension having one end integrally fixed to a yoke (49) forming an eccentric (50) configured to cooperate with a pitch change mechanism. System according to Claim 1, in which the transverse extension (48) comprises a boss (60) formed at a free end of the extension, presenting a contact surface (62) transverse to the axis (A) and configured to receive one end (58) of the yoke (50). A system according to claim 2, wherein the boss contact surface (62) has a substantially elliptical shape and the end of the yoke attached to the boss has a shape complementary to the boss contact surface. System according to Claim 2 or 3, in which the transverse extension (48) comprises a face stop (64) extending in a plane parallel to the axis (A) and the yoke (50) comprises a shoulder (66) configured to bear against the facial abutment of the transverse extension. System according to one of Claims 2 to 4, in which the yoke is firmly fixed to the boss of the transverse extension by at least one bolted connection, preferably of the screw-nut type. System according to the preceding claim, in which the end of the yoke (50) fixed to the boss (60) has at least one through hole and the boss (60) has at least one through hole in the contact surface arranged opposite to a through hole in the yoke, each screw of a bolted connection being inserted successively into a through hole in the yoke and a through hole in the boss. System according to Claim 5, dependent on Claim 4, in which the yoke (160) comprises an extension (170) extending along the axis (A) and comprising at least one through orifice with an axis perpendicular to the axis A, and the transverse extension (148) of the foot support comprises a wall (172) extending along the axis (A) in which is made at least one through hole arranged opposite an orifice passing through the yoke, and having a bearing surface (174) configured to receive the extension of the yoke, each screw of a bolted connection being inserted successively into a through hole of the yoke and a through hole of the transverse extension of the support of foot. System according to Claim 5, in which the yoke comprises two parallel arms connected by a central portion, the central portion comprising at least one through hole with an axis transverse to the axis A, and the transverse extension of the foot support comprises at least a through hole arranged opposite a through hole in the yoke, each screw of a bolted connection being inserted successively into a through hole in the yoke and a through hole in the transverse extension of the foot support. System according to one of the preceding claims, in which the lower face opposite the upper face comprises a cylindrical extension extending along the axis A between the bottom wall and the transverse extension. Turbomachine (10; 100) for aircraft comprising at least one propeller provided with blades and at least one pitch change system according to one of the preceding claims.