Turbomachine polyspherical hub for variable pitch blades
The present invention concerns a turbomachine hub, intended to be mounted so as to be able to rotate about a longitudinal axis (X) of the turbomachine, the hub comprising a main body ( 1 ) arranged around the longitudinal axis (X), an outer surface of which has a plurality of recesses; a plurality of platforms ( 3 ) comprising an outer surface delimited by a circular outer edge of radius r, each platform ( 3 ) being arranged in a corresponding recess of the plurality of recesses of the main body ( 1 ), and intended to receive a variable pitch blade ( 2 ), the pitch of which is variable according to a pitch change axis (Z), the platform ( 3 ) being centred and able to rotate about the pitch change axis (Z); characterised in that, for each platform, at least one part of the outer surface of the platform ( 3 ) and the main body ( 1 ) of the hub comprises a curvature defined by a same sphere portion of radius R and centre C, the at least one part being situated at the outer edge of the platform ( 3 ), in a junction zone between the platform ( 3 ) and the main body of the hub ( 1 ), the centre C of the sphere being situated on the pitch change axis (Z) outside a hemispherical zone delimited between the longitudinal axis (X) and the outer surface of the platform ( 3 ).
1. A turbomachine hub to be mounted in rotation along a longitudinal axis of a turbomachine, the turbomachine hub comprising a main body disposed around the longitudinal axis, of which an outer surface has a plurality of housings;
a plurality of platforms comprising an outer surface delimited by a circular outer edge of radius r, each platform being disposed in a corresponding housing of the plurality of housings of the main body, and intended configured to receive a variable pitch blade according to a pitch change axis, each platform being centered and movable in rotation along the pitch change axis;
wherein, for each platform, at least part of the outer surface of each platform and of the main body of the turbomachine hub comprises a curvature defined by a same spherical portion of radius R and center C, the at least part of the outer surface being situated at the outer edge of each platform, in a junction zone of each platform and of the main body of the turbomachine hub,
the center C being situated on the pitch change axis outside a hemispherical zone delimited between the longitudinal axis and the outer surface of each platform.
2. The turbomachine hub according to claim 1 , wherein the outer surface of the platform is entirely defined by the spherical portion of radius R and center C.
3. The turbomachine hub according to claim 1 , wherein the junction zone is defined by a projection of the junction zone into a plane orthogonal to the pitch change axis, the projection being a ring centered on the pitch change axis and delimited between a circle with inner radius ri less than the radius r of the outer edge of each platform, and a circle with outer radius re greater than the radius r of the outer edge of each platform.
4. The turbomachine hub according to claim 3 , wherein the outer surface of each platform comprises a central part having a curvature opposite to the curvature of the outer surface in the junction zone, a projection of the central part in the plane orthogonal to the pitch change axis being delimited by the circle of inner radius ri.
5. The turbomachine hub according to claim 1 , wherein the center C defining the outer surface of each platform is situated at the intersection of the pitch change axis and of the longitudinal axis.
6. The turbomachine hub according to claim 1 , wherein the main body of the turbomachine hub comprises a plurality of intermediate zones situated between two junction zones with adjacent platforms of the plurality of platforms, each intermediate zone having an outer surface having a curvature opposite to the curvature of the outer surface of the main body in the junction zone.
7. A turbomachine assembly comprising a turbomachine hub according to claim 1 and a plurality of variable pitch blades configured to be connected to the main body of the turbomachine hub by means of the plurality of platforms.
8. The assembly according to claim 7 , wherein each platform of the plurality of platforms is made in one piece with a corresponding blade of the plurality of blades.
9. The assembly according to claim 7 , wherein each platform comprises at least two distinct parts, intended to surround a root part of a corresponding blade.
10. The assembly according to claim 7 , wherein the outer surface of each platform is complementary to the shape of a corresponding blade, so that the platform is in contact with the corresponding blade from a leading edge of the corresponding blade to a trailing edge of the corresponding blade, and is also in contact with a suction side and a pressure side of the corresponding blade.
11. A turbomachine with a shrouded or unshrouded fan, comprising an assembly according to claim 7 .