PROPELLER RING COMPRISING RADIAL HOUSINGS WITH AN OVOID CROSS-SECTION

Abstract

The invention relates to a propeller ring (10) of a turbomachine (1), with variable-pitch blades (P), the propeller ring (10) comprising a substantially coaxial annular body (11) with a main axis (A) and a plurality of radial housings (12) uniformly distributed around the main axis (A), each radial housing (12) being designed to receive a bearing (13) for a root (14) of a blade (P) so as to allow the variable pitch of the blade (P), the radial housings (12) having a substantially ovoid cross-section in a plane (T) tangential to the annular body (11).

Claims

1. Propeller ring of a turbomachine with variable pitch blades (P), the propeller ring comprising an annular body substantially coaxial with a main axis (A) and a plurality of radial housings uniformly distributed around the main axis (A), each radial housing being designed to receive a bearing for a root of a blade (P) so as to allow variable pitch of the blade (P), the propeller ring the radial housings have, in a plane (T) tangential to the annular body, a substantially ovoid cross-section, said substantially ovoid cross-section having a minor diameter and a major diameter with distinct dimensions.

2. The propeller ring according to claim 1, wherein the section of the radial housings is elliptical.

3. The propeller ring according to claim 1, wherein the major diameter is greater than the minor diameter, said major diameter extending substantially parallel to the main axis (A) of the propeller ring.

4. The propeller ring according to claim 1, wherein the major diameter is greater than the minor diameter, said minor diameter extending substantially parallel to the main axis (A) of the propeller ring.

5. The propeller ring according to claim 3, wherein the bearing comprises an outer bearing ring and a difference between the major diameter and the minor diameter of the substantially ovoid cross-section is comprises between 0.5 and 1% of a diameter of the outer bearing ring.

6. The propeller ring according to claim 5, wherein the diameter of the outer bearing ring is on the order of 200 mm and the difference between the major diameter and the minor diameter is comprised between 1 mm and 2 mm.

7. The propeller ring according to claim 1, wherein the bearing has, in the plane (T) tangential to the propeller ring a substantially circular cross-section.

8. The propeller ring according to claim 1, wherein the annular body has a polygonal shape.

9. A turbomachine with variable pitch blades (P), comprising a propeller ring according to claim 1.

10. The turbomachine according to claim 9, wherein the propeller is unducted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, aims and advantages of the present invention will appear more clearly upon reading the detailed description that follows, and with reference to the appended drawings given by way of non-limiting examples wherein:

[0021] FIG. 1 is a schematic view of a turbomachine with unducted propellers,

[0022] FIG. 2 illustrates schematically a polygonal propeller ring 10,

[0023] FIG. 3 shows, in a partial section view, a propeller module of a conventional open rotor (or unducted fan),

[0024] FIG. 4 is a top view of a first embodiment of a radial housing in a polygonal propeller ring 10, and

[0025] FIG. 5 is a top view of a second embodiment of a radial housing of a polygonal propeller ring 10.

DETAILED DESCRIPTION OF AN EMBODIMENT

[0026] A propeller ring 10 of a turbomachine 1 with variable pitch blades P according to the invention will now be described.

[0027] A propeller ring 10 according to the invention comprises, in a manner known in se and as previously described with reference to the appended FIGS. 1 to 3, an annular body 11 of the rotor, centered on the longitudinal axis A of the turbomachine 1 and having a series of radial housings 12 regularly distributed around the axis A. Each radial housing 12 is provided for receiving a bearing 13 of an associated blade P of the propeller 9, which makes it possible to adjust the angular orientation of the blade P.

[0028] To this end, each bearing 13 comprises in a manner known per se, ball bearings placed in an inner bearing ring and an outer bearing ring of circular shape.

[0029] Here, the annular body 11 of the rotor is of polygonal shape. This is not limiting, however, the annular body 11 being capable of having any suitable shape, a circular shape for example.

[0030] As can be seen in FIGS. 4 and 5, the radial housings 12 have, in a plane T tangential to the annular body 11, a substantially ovoid cross-section.

[0031] What will be understood here by a plane T tangential to the annular body 11 is a plane substantially normal to a radial axis X of the propeller ring 10 (that is an axis perpendicular to the axis A of the propeller ring 10 and running through the axis A) and comprising the associated radial housing 12 and the bearing 13.

[0032] In one embodiment, the ovoid cross-section can for example be substantially elliptical.

[0033] The ovoid cross-section of each radial housing 12 comprises a minor diameter 12b and a major diameter 12a having a distinct dimension. Here, the minor diameter 12b is smaller than the major diameter 12a. For example, when the radial housing 12 is elliptical in shape, the minor diameter 12b corresponds to the shorter axis of the ellipse while the major diameter 12a corresponds to its long axis.

[0034] In a first embodiment illustrated in FIG. 4, the radial housings 12 have a substantially ovoid cross-section, the major diameter 12a (or long axis) whereof extends substantially parallel to the axis A of the propeller ring 10.

[0035] Such an embodiment makes it possible to correct deformations of the radial housings 12 due to very large tangential loads under the influence of centrifugal loads, which are greater than the axial forces to which the propeller ring 10 is subjected. This is the case in particular of the embodiment illustrated in FIG. 2, wherein the ring comprises inter-blade portions (that is arms connecting the radial housings 12) positioned on either side of the radial housings 12.

[0036] As a variant, in a second embodiment illustrated in FIG. 5, the radial housings 12 have a substantially ovoid cross-section, the minor diameter 12b whereof (or short axis A) extends substantially parallel to the axis A of the propeller ring 10.

[0037] Such an embodiment is advantageous when the propeller ring 10 is flexible and narrow. It is the case, for example, when the annular body 11 comprises inter-blade portions positioned at the center of the structure: such an annular body 11 is capable of having deformations of the radial housings in the axis parallel to the axis of revolution A of the ring. Implementation of radial housings 12 according to the second embodiment. It thus allows correction of the deformations of the radial housings 12 due to axial forces which are greater than the tangential forces to which the propeller ring 10 is subjected.

[0038] The ovoid shape of the cross-section of the radial housings 12 thus makes it possible to compensate the deformation of the radial housings 12 during operation of the turbomachine 1. In this manner, when the propeller ring 10 is under load (that is when the turbomachine 1 is in operation and the propeller ring 10 is subjected to considerable axial and/or centrifugal loads), the radial housings 12 deform until they attain a substantially circular cross-section allow good resistance of the parts of the bearing and optimal operation of the pitch of the blades P and an extension of the lifetime of the bearing parts. Typically, in the case of the radial housings 12 illustrated in FIG. 4 (ovoid axial cross-section), the centrifugal loads have a tendency to deform the radial housings 12 in the tangential direction, which tends to extend the minor diameter 12b of the ovoid cross-section and to reduce its major diameter 12a.

[0039] The minor diameter 12b and the major diameter 12a of the ovoid cross-section of the radial housings 12 are therefore selected so that, under load, the second of the radial housings 12 takes on a circular geometry.

[0040] The difference between the major diameter 12a and the minor diameter 12b of the substantially ovoid cross-section of the radial housings 12 can for example be comprised between 0.5 and 1% of the diameter of the radial housing 12 under load. The diameter of the radial housing 12 under load corresponds substantially to the diameter of the outer bearing ring, the difference between the major diameter 12a and the minor diameter 12b of the substantially ovoid cross-section of the radial housings 12 can therefore be comprised between 0.5 and 1% of the associated bearing 13.

[0041] Typically, for a radial housing 12, the diameter whereof under load must be on the order of 200 mm, the difference between the major diameter 12a and the minor diameter 12b is comprised between 1 mm and 2 mm.

[0042] In order to create radial housings 12 with a substantially ovoid cross-section while still retaining the cylinder-of-revolution shape of the bearing rings, it is for example possible to sinter the bearing rings by heating the ring then to deform the minor diameter 12b of the radial housings 12 until reaching a slightly greater diameter than that of the bearing rings (typically a few tenths of millimeters) to allow assembly.

[0043] The invention thus proposes to correct the deformation of the radial housings 12, rather than attempting to prevent or limit this deformation by directly modifying the structure of the propeller ring 10, which negatively impacts the mass, as is generally proposed in conventional propeller rings 9. The proposed solution is therefore simple to implement and does not impact the size or the overall weight of the propeller ring 10.