Patent ID: 12241377

DETAILED DESCRIPTION OF THE DISCLOSURE

The disclosure applies to a turbomachine1comprising an unducted propeller2for mounting on an aircraft. Such a turbomachine is a turboprop engine as shown inFIG.1. This turbomachine is known as “open rotor” or “unducted fan” as explained above.

In the present disclosure, and in general, the terms “upstream”, “downstream”, “axial” and “axially” are defined in relation to the flow of the gases in the turbomachine and here along the longitudinal axis X (and even from left to right inFIG.1). Similarly, the terms “radial”, “internal” and “external” are defined with respect to a radial axis Z perpendicular to the longitudinal axis X and with respect to the distance from the longitudinal axis X. Furthermore, the identical or substantially identical elements and/or10with the same functions are represented by the same numerical references.

The turbomachine1comprises a gas turbine or engine3which typically comprises, from upstream to downstream, a low-pressure compressor4, a high-pressure compressor5, a combustion chamber6, a high-pressure turbine7and a low-pressure turbine8. The low-pressure compressor4and the low-pressure turbine8are mechanically connected by a low-pressure shaft9so as to form a low-pressure body. The high-pressure compressor5and the high-pressure turbine7are mechanically connected by a high-pressure shaft so as to form a high-pressure body. The high-pressure shaft extends inside the low-pressure shaft9and are coaxial

In another configuration not shown, the low-pressure body comprises the low-pressure compressor which is connected to an intermediate pressure turbine. A free power turbine is mounted downstream of the intermediate pressure turbine and is connected to the propeller described below via a power transmission shaft to drive it in rotation.

A primary air flow F1circulates in a primary duct10which passes through the gas turbine3. The primary duct10is radially delimited by a radially internal wall11and a radially external wall12. The radially internal wall11is carried by an internal casing13. The radially external wall12is carried by an external casing14. The primary air flow F1enters the gas turbine3through an annular air inlet15and exits through a primary nozzle16which is arranged downstream of the gas turbine3

The turbomachine comprises a rotating casing20centred on the longitudinal axis X and rotating about the longitudinal axis X. The rotating casing20carries a ring gear of movable blades21forming the propeller2. The rotating casing20is mounted so that it can be moved relative to the internal casing13which supports it. In the example shown inFIG.1, the propeller2is mounted upstream of the gas turbine (puller configuration). Alternatively, the propeller is mounted downstream of the gas turbine (pusher configuration). The air flow F entering the turbomachine passes through the propeller blades21to form a secondary air flow F2. This secondary air flow circulates around the external casing14. The air flow F divides into a primary air flow and a secondary air flow at the level of a splitter nose22carried by the external casing14. Each blade21of the propeller2comprises a root23and extends radially outward from the root23. The blades of the propellers are not ducted as shown inFIG.1(the turbomachine shown is of the “USF” type, i.e. as explained above, it comprises a single unducted propeller and a straightener comprising several unducted stator vanes).

The power shaft or low-pressure shaft9(of the free power turbine and of the low-pressure turbine respectively) drives the propeller2by means of a reducer24which compresses the air outside the external casing14and provides most of the thrust. The reducer24can be of the planetary gear train or epicyclic gear train type.

As can be seen inFIG.1, the turbomachine1comprises a straightener25comprising a plurality of stator vanes26(or stationary vanes) known by the acronym “OGV” for Outlet Guide Vane. The stator vanes26are evenly distributed about the longitudinal axis X and extend radially into the secondary air flow. The stator vanes26are carried by a stationary structure secured to the external casing14. In particular, each stator vane26comprises a blade27that extends radially from a root28. We understand that the stator vanes26are unducted.

InFIG.2, ten stator vanes26are mounted on the external casing14. Advantageously, the stator vanes26are variable in pitch so as to optimize the performance of the turbomachine. For this purpose, the turbomachine comprises a first system30for changing the pitch of the blades of the stator vanes. InFIG.2, the first pitch change system30comprises at least one first control means31and at least one first connection mechanism32connecting each stator vane26to the first control means31.

FIG.3shows an axial cross-sectional view of a root28of a stator vane26. Typically, the root28is in the form of a pivot33that is pivotally mounted along an axis A in a housing34. In particular, an annular shroud35centred on the longitudinal axis X comprises a plurality of housings34distributed around its circumference. The annular shroud35is secured to the external casing14. Each housing34is delimited by a cylindrical skirt36extending along the radial axis Z. The pivot33of the root is pivotally mounted by means of at least one guide bearing37. In the present example, two guide bearings37,37′ are superimposed along the radial axis Z. These bearings37are preferably, but not restrictively, rolling bearings.

Each bearing37,37′ comprises an internal ring38that is secured in rotation to the pivot33and an external ring39that surrounds the internal ring38. The rollings are installed between the internal surfaces of the internal and external rings38,39which form tracks. The rollings here comprise balls40.

A cylindrical socket41is installed in each housing34so as to connect the internal ring38of each bearing37,37′ to the root of each stator vane26. The socket41is centred on the pitch axis A of the stator vanes. Each socket41extends between a first end42and a second end43. Each socket41has internal splines44arranged on an internal cylindrical face. The internal splines44are intended to couple with external splines45provided on an external surface of the pivot33of each root of a stator vane26. The second end43of the socket41comprises a collar46that extends radially outwardly from the (cylindrical) body of the socket41relative to the axis A. The collar46forms a radially external surface47on which a hub48of the pivot33rests. The external ring39of each bearing37,37′ is carried by the shroud35, in particular the cylindrical skirt36. Between each bearing extends along the radial axis Z a spacer50intended to maintain a distance (here radial) between the two bearings37,37′. This spacer50is advantageously, but not restrictively, placed between two internal rings38of the bearings37,37′.

The shroud35also comprises an annular bottom wall51secured to the cylindrical skirt36. The bottom wall comprises holes53that pass through it on either side along the radial axis and allow the free end54of the pivot33to pass through.

Sealing elements are arranged in each housing34so as to prevent lubricant leakage from the bearings to the outside of the housing. In particular, a first annular seal55is arranged between an internal surface56of the cylindrical skirt36and a peripheral border48aof the hub48. A second seal57is provided between an internal border58of a hole53and an external surface41aof the socket41.

Finally, in order to avoid any displacement of the pivot33along the radial axis, a holding element59allows the free end54of the pivot to be attached to the bottom wall51of the shroud35. The holding element59comprises a nut. Other analogous threaded elements allowing to attach the pivot to the shroud are of course possible.

With reference toFIGS.3and4, the first connection mechanism32comprises a connection annulus60that is centred on the longitudinal axis X. The connection annulus60comprises a first annular segment61and a second annular segment62that are concentric and coaxial. The first and second segments61,62are radially spaced apart and are connected to each other by bridges63that form through openings64along the longitudinal axis X. The connection annulus60is connected to the roots of each stator vane.

For this purpose, the first connection mechanism32comprises at least one arm65connected on the one hand to the connection annulus60and on the other hand to the root28of a vane26. The arm65extends between a first end66and a second end67. The first end66is provided with a ball joint68(seeFIG.3) which is passed through by a hinge axis69carried by the connection annulus60. The hinge axis69is mounted between the first segment61and the second segment62and is parallel to the radial axis Z. The second end67is connected to the root28of a stator vane26in an embedded connection. As can be seen inFIG.3, the second end67comprises an orifice70that passes through it on either side along the radial axis. The free end54of each pivot is mounted in each orifice70. Advantageously, but not restrictively, the pivot33comprises a radial bore71that opens at the level of the free end54thereof. An attachment member72such as a screw is received in the radial bore71to attach the arm65to the root of the stator vane26. In the example shown, there are as many arms as there are stator vanes. And each arm is connected to a vane root and to the connection annulus60.

With reference toFIGS.4and5, the first connection mechanism32also comprises at least one lever73which is connected, on the one hand, to the connection annulus60and, on the other hand, to the first control means31.

In this example, there are two first control means31and two levers73that cooperate with each other. The first two control means31allow to transmit the forces to the connection annulus60and the pitch change of the blades of the stator vanes26. The first connecting means are diametrically opposed with respect to the axis of the connection annulus60.

Each first control means31comprises a first stationary body75and a first body76movable relative to the first stationary body. Each first stationary body75is connected to a stationary shroud77(seeFIG.5) of the turbomachine so as to be immovable in translation and in rotation. In particular, the stationary shroud77is mounted on the external casing14. Each first movable body76displaces in translation axially with respect to the respective first stationary body75along the longitudinal axis X. Each first movable body76comprises an axial rod78whose free end79is connected to a lever73.

Each lever73is L-shaped with a first branch80and a second branch81connected to each other. InFIG.5, the first branch80comprises at a first distal end82(seeFIG.4) a clevis83. The latter comprises, according toFIG.5, a first ear84and a second ear85superimposed and spaced along the radial axis. The first and second ears84,85extend in planes substantially parallel to each other. A hinge shaft86extends along an axis parallel to the radial axis between the first and second ears. The free end79of the axial rod78comprises an eyelet through which the hinge shaft86passes so as to make a pivot connection.

InFIG.6, the second branch81comprises a ball joint87through which a second hinge axis carried by the connection annulus60passes. The second hinge axis is mounted between the first segment61and the second segment62and is parallel to the radial axis Z.

With reference toFIG.6, the lever73is mounted on a support90that is secured to the stationary structure of the turbomachine. The stationary structure is secured to the external casing14. The support90allows the lever73to be held relative to the external casing14. In particular, at the level of the junction between the first branch80and the second branch81, the lever73is connected to the support90by a pivot connection. As can be seen inFIG.4, the support comprises a base plate91that is connected to a main body92. The main body is attached to the stationary structure93secured to the external casing of the turbomachine. The attachment is done by means of attachment members such as screws and nuts. The base plate91extends in a plane that is perpendicular to the radial axis and parallel to the plane in which the main body is defined. The base plate91forms a C or a U shape with the main body92. The space between the base plate91and the main body92receives a summit94of the lever73defined by the junction of the first and second branches. The summit94is passed through by an orifice95along a radial axis. A pivot member96carried by the main body and the base plate91extends through the orifice of the lever and along a radial axis Z. An upper cushion97and a lower cushion98are arranged in the orifice95. The pivot member passes through the cushions97,98.

Each lever73then has three axes of rotation.

Advantageously, the first control means are each a hydraulic cylinder comprising the stationary body and the movable body. Each first control means is connected to a fluidic supply source for supplying pressurized oil to chambers (not shown) of the stationary body. The movable body extends inside the stationary body.

Advantageously, the pitch change system is arranged in an annular space29defined in the external casing14. Each first control means is arranged at the level of the splitter nose22as shown inFIG.1. In particular, each first control means is arranged upstream of the roots28of the stator vanes and also upstream of the connection annulus60.

The axial rod78of each movable body extends through a through opening64defined in the connection annulus60.

We will now present the kinematics of the various members during the change of pitch of the blades of the stator vanes. All the blades of the stator vanes26pivot simultaneously. As a first movable body76of a first control means31displaces in translation along the longitudinal axis, the free end79of the axial rod78of this first movable body76also displaces in translation along the axis X and drives the rotation of a lever73to which it is connected to the support. This lever73, which is also connected to the connection annulus60, drives in rotation the connection annulus60about the longitudinal axis, which generates the change in pitch of the blades of the stator vanes26connected to the connection annulus60via the arms65. In this way, with a translation of the first movable body of the cylinders and a rotation of the levers73connected to the single connection annulus60, all the blades of the stator vanes26change their pitch or their orientation. The blades of the stator vanes26rotate between −10° and +10°.

The turbomachine module may comprise a second system100for changing the pitch of the movable blades of the propeller2, as shown inFIG.1. This second pitch change system is arranged upstream of the gas turbine3and radially below the roots of the movable blades21of the propeller2. This pitch change system100comprises a second control means101comprising a second body102axially movable relative to a second stationary body mounted on the internal casing13. The pitch change system also comprises at least one load transfer bearing103comprising an internal ring connected to the second movable body and an external ring, as well as a second mechanism104for connecting the external ring to the movable blades of the propeller. The system for changing the pitch of the blades of the propeller2allows to vary the pitch of the blades21around their pitch axes so that they occupy different angular positions according to the operating conditions of the turbomachine and the phases of flight concerned, such as an extreme working position (thrust reversal position) and an extreme feathering position of the blades. The second control means is also a hydraulic cylinder comprising the second stationary body and the second movable body. The connection mechanism here comprises connecting rods.