FR3107077A1 - RIGIDIFIED TURBOMACHINE PLATFORM - Google Patents

Abstract

The invention relates to a platform (18) for a fan (12) of a turbomachine (10), which is intended to be mounted on a hub (14) of the fan (12) between two adjacent blades (16), the platform (18). ) comprising a main wall (20) which is of curved shape in the longitudinal direction having curved edges (24, 26), a stiffener (34) which is mounted on an internal face (36) of the main wall (20), characterized in that the stiffener (34) comprises at least two rectilinear sections (38) which are inclined with respect to each other and inclined with respect to the main longitudinal direction, the transverse end walls (44, 46 ) of each of said sections (38) having their outer edges located opposite the main wall (20) which are free so that the section of the stiffener is open opposite the main wall (20). Figure for the abstract: Figure 3

Description

RIGIDIFIED TURBOMACHINE PLATFORM

The invention relates to a platform for reconstituting a turbomachine fan section comprising stiffening means.

The invention relates more particularly to a platform intended to be installed on a fan comprising a low hub ratio.

PRIOR ART

In a turbomachine, a platform is a component which is installed between two adjacent blades, in particular at the level of the roots of the blades, to produce a continuous wall, having a reduced number of asperities.

Such platforms are in particular installed on the fan disposed upstream of the turbine engine.

A hub ratio for a fan is defined as being the ratio between the radial dimension of a first radially internal point and the radial dimension of a second radially external point of the fan.

The first point is located at the intersection of the leading edge of a blade with the wall of the hub which radially delimits the interior of the air flow path in the fan. The second point is located at the same axial position as the first point, along the main axis of the fan, and it is located on a radially inner wall of the fan casing, which radially delimits the outside of the vein .

A low hub ratio implies that the roots of the blades are close together and therefore that the width of each platform which is mounted on the hub is reduced.

In addition, in a fan with a low hub ratio, the blades are strongly cambered, that is to say that the profiles of the lower surfaces and the upper surfaces are strongly curved.

As a result, the side edges of the platform are also strongly curved and they are very close to each other.

The main shape of the platform is therefore also curved.

The platform mainly consists of a main wall, which has the curved shape of the platform and a stiffener which is arranged on a radially inner face of the main wall.

Due to manufacturing constraints, the stiffener is straight and extends over the longitudinal length of the main wall.

However, as was said previously, the main wall is also curved, which poses a problem of integration of the rectilinear stiffener on the main wall.

The object of the invention is to propose a platform for a fan with a low hub ratio, which comprises a stiffener adapted to the curved shape of the main wall of the platform.

The invention proposes a turbomachine fan platform, which is intended to be mounted on a hub of the fan between two adjacent blades, the platform comprising

a main wall having a transverse longitudinal main orientation by comprising an outer face intended to be in contact with a flow of air passing through the fan, which is of curved shape in the longitudinal direction by having curved edges,

a stiffener which is mounted on an internal face of the main wall, which comprises an upper wall which is joined against the main wall, and two transverse end walls offset transversely relative to each other, which extend vertically from the main wall, said upper wall being joined against the main wall on the one hand by transversely connecting the two transverse end walls at their outer ends located on the side of the main wall, and on the other hand by making projecting transversely with respect to the transverse end walls,

characterized in that the stiffener comprises at least two rectilinear sections which are inclined with respect to each other and inclined with respect to the main longitudinal direction, the transverse end walls of each of the said sections having their outer edges located at opposite the main wall which are free so that the section of the stiffener is open opposite the main wall.

The realization of the stiffener in two inclined sections makes it possible to follow the curvature of the main wall, while preserving the straightness of each section of the stiffener.

Preferably, each section has a proximal end which is located longitudinally close to an adjacent section, and the proximal end of each section is offset transversely relative to the proximal end of an adjacent section in a transverse direction perpendicular to the main longitudinal direction of the main wall.

Preferably, the proximal ends of two adjacent sections are joined longitudinally to one another.

Preferably, the first transverse end wall of a section and the second transverse end wall of an adjacent section are in the extension of one another.

Preferably, an end of the first transverse end wall of a section, which is located at the proximal end of said section, is offset transversely with respect to an end of the second transverse end wall of an adjacent section. , which is located at the proximal end of said adjacent section.

The invention also relates to a turbomachine fan comprising a central hub carrying blades distributed around a main axis of the fan and platforms according to the invention, each platform of which is fixed to the hub and is arranged between two adjacent blades.

Preferably, the main wall of each platform comprises a first edge which is in contact with a lower surface wall of a first blade and a second edge which is in contact with a lower surface wall of a second blade.

Preferably, the minimum transverse distance between the first edge and the second edge is greater than the width of the stiffener.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended figures, among which:

is an end view of an aircraft turbine engine showing the upstream fan;

is a top view of a platform without stiffeners;

is a top view of a platform made according to the invention;

is a side view of the platform produced according to the invention;

is an end view of the platform produced according to the invention;

is a view similar to that of FIG. 3 showing an alternative embodiment of the stiffener

is a schematic sectional representation of the platform made according to the invention;

is a bottom view of a platform showing both the relative shape of the main wall of the platform and of the blades and showing another embodiment of a stiffener comprising three sections.

DETAILED DESCRIPTION OF THE INVENTION

For the description of the invention, the vertical, longitudinal and transverse orientations according to the reference V, L, T indicated in the figures will be adopted without limitation. The longitudinal direction being a direction along the main axis of the turbomachine and in which the orientation from upstream to downstream being from right to left with reference to FIGS. 3 et seq.

There is shown in Figure 1 an aircraft turbine engine 10 comprising a fan 12 upstream.

The fan 12 compresses a large mass of cold air, of which part of this mass of air compressed by the fan 12 is injected into a primary stream of the turbomachine and the rest of this air mass is injected into a secondary stream. of the turbomachine, forming a cylindrical flow enveloping the engine and directed rearwards to create thrust.

The fan 12 comprises a central hub 14 and a plurality of blades 16 which are carried by the hub 14 and which extend radially with respect to the main axis of the turbomachine 10 from the hub 14.

The hub carries a plurality of platforms 18, one platform 18 of which is shown in Figures 2 and following, which are installed between the blades 16, close to the root of each blade 16.

The platforms 18 make it possible to form a part of the outer wall of the hub 14, delimiting the air flow vein, to limit the aerodynamic disturbances between the blades 16.

As can be seen in Figure 2, each platform 18 has a main wall 20, which forms the outer wall of the hub 14, the outer face 22 of which comes into contact with the air flow.

The main wall 20 of the platform 18 has a main longitudinal orientation generally parallel to the main axis of the turbine engine 10. It is delimited transversely by a first edge, which will be called the intrados edge 24 and which is intended to come in contact with the lower surface wall of a first blade 16, and by a second edge, which will be called extrados edge 26 and which is intended to come into contact with the upper surface wall of a second blade 16 which is immediately adjacent to the first blade 16.

The main wall 20 of the platform 18 is also delimited longitudinally by an upstream edge 30 and a downstream edge 28 which include means for fixing the platform 18 to the hub 14 of the fan 12.

Referring to Figure 1, for sizing the fan 12, a hub ratio is used as the ratio dm/df, where dm is the diameter of the hub 14 and df is the outside diameter of the fan.

A line of development for improving the efficiency of a turbomachine consists in increasing its bypass rate, i.e. the ratio between the mass of air circulating through the fan, which is commonly called the cold flow and the mass of air from the primary stream, or hot stream, which has passed through the fan and which is injected into the primary stream of the turbomachine. This hot flow notably passes through the compressor and is heated in the combustion chamber.

In order to increase the bypass ratio, it was proposed to reduce the hub ratio of the fan 12.

Thus, by keeping the same diameter df of the fan 12, the diameter dm of the hub 14 is consequently reduced.

This has the consequence that the roots of the blades 16 are brought closer together.

Also, each blade 16 is strongly curved at its root, which implies that the leading edge and the trailing edge have a significant curvature.

Consequently, the intrados edge 24 and the extrados edge 26 of the main wall 20 of the platform 18 also have a significant curvature. The main wall 20 of the platform 18 therefore has a very pronounced general curvature.

Also, this low hub ratio implies that the transverse distance between the intrados edge 24 and the extrados edge 26 is relatively small, as illustrated by the longitudinal segments 32 showing the smallest transverse distance between the edge of intrados 24 and the extrados edge 26.

As can be seen in Figures 3 and following, the platform 18 also includes a stiffener 34 which is fixed to the internal face 36 of the main wall 20.

As can be seen in the figures, the stiffener 34 has a so-called Pi-shaped section open downwards.

The stiffener 34 thus comprises a first transverse end wall 44 which extends vertically downwards and which is located at a first transverse side of the platform 18, a second transverse end wall 46 which extends vertically downwards bottom and which is located at a second transverse side of the platform 18 and an upper wall 50 transversely connecting the upper end edges of the two transverse end walls 44, 46, which are located near the main wall 20.

The upper wall 50 is joined against the inner face 36 of the main wall 20. Also, this upper wall 50 extends transversely beyond the transverse end walls 44, 46, that is to say that it projects transversely on either side of the transverse end walls 44, 46.

The upper wall 50 thus forms the interface between the stiffener 34 and the main wall 20. Preferably, the shape of the upper wall 50 of the stiffener 34 is substantially identical to the shape of the main wall 20, that is to say say that it is delimited transversely by edges which are curved in a similar way to the intrados edge 24 and to the extrados edge 26 of the main wall 20.

The two transverse end walls 44, 46 thus extend vertically downwards from the upper wall 50 and their lower ends, that is to say their outer edges which are located opposite the main wall 20 , are free, that is to say they are not connected to any other wall.

Thus, the section of the stiffener 34 is open downwards, that is to say opposite the main wall 20.

Here, it will be considered that the first transverse end wall 44 is located near the upper surface edge 26 and the second transverse end wall 46 is located near the lower surface edge 24.

Thus, the stiffener 34 is mounted on an internal face 36 of the main wall 20 by comprising its upper wall 50 which is joined against the main wall 20. The two transverse end walls 44, 46 of each stiffener 34 are offset transversely l relative to each other, and they extend vertically from the main wall 20.

The upper wall 50 of the stiffener 34 is joined against the main wall 20 on the one hand by transversely connecting the two transverse end walls 44, 46 at their upper end edge external ends located on the side of the main wall 20, and on the other hand by projecting transversely with respect to the transverse end walls 44, 46. The end edges of the upper wall 50 are located on the side of the main wall 20.

Also, the stiffener 34 is made in a single piece of composite material which is attached to the main wall 20.

The stiffener 34 is rectilinear in shape along the main longitudinal direction of the platform 18.

As mentioned above, the transverse distance between the intrados edge 24 and the extrados edge 26 is relatively small and this distance is less than the minimum width of the stiffener 34 for it to be able to offer sufficient stiffness. to the platform 18, i.e. less than the transverse distance between the transverse end walls 44, 46.

The stiffener 34 is for this purpose produced in at least two rectilinear sections 38, the orientation and position of each section 38 of which with respect to the main wall 20 makes it possible to produce the stiffener 34.

As can be seen in Figure 3, each section 38 is inclined relative to the main longitudinal direction of the platform 18 and they are inclined relative to each other forming an open V towards the upper surface edge. 26.

Each section 38 has a first end 40, which will be called the proximal end hereinafter, which is located longitudinally close to the other section 38, that is to say which is located at an intermediate longitudinal position along of platform 18.

This intermediate longitudinal position of the proximal end 40 is defined according to the general curvature of the main wall 20. According to a non-limiting example, the proximal end 40 is located longitudinally at the level of the middle of the main wall.

In the embodiment for which the stiffener is made in two sections 38, each of these two sections 38 comprises a second end 42, which will be referred to below as the distal end and which is located at the level of the upstream edge 30 or the downstream edge 28 of the main wall 20.

Preferably, as can be seen in FIG. 4, the two proximal ends 40 of the two sections 38 are joined longitudinally to one another. This prevents part of the main wall 20 from being stiffened by the stiffener 34.

Each end 40, 42 has a flat end edge which extends in a plane substantially perpendicular to the longitudinal direction, which allows the two proximal ends 40 of the two sections 38 to be joined.

As was said previously, with reference to FIG. 7, the section of the stiffener 34, along a transverse vertical plane, is in the form Pi. Consequently, the section of each of the sections 38 of the stiffener 34 also has this shape. Thus, the stiffener 34 has its two sections 38 whose transverse end walls 44, 46 each have their outer edge located opposite the main wall 20 which is free so that the section of the stiffener is open to the opposite the main wall.

Each section 38 thus comprises a first transverse end wall 44 which extends vertically downwards and which is located at a first transverse side of the platform 18, a second transverse end wall 46 which extends vertically downwards bottom and which is located at a second transverse side of the platform 18 and an upper wall 50 transversely connecting the upper end edges of the two transverse end walls 44, 46, which are located near the main wall 20.

As shown in Figure 3, the proximal ends 40 of the two sections 38 are offset transversely relative to each other. It will be understood that the invention is not limited to this embodiment and that the proximal ends 40 of the two sections 38 can also be located at the same transverse position.

According to a first aspect of the embodiment represented in FIG. 3, the transverse offset of the proximal ends 40 of the sections 38 is such that the ends of the transverse end walls 44, 46 are all offset transversely relative to each other.

According to a variant embodiment of this embodiment, which has been represented in FIG. 6, the first transverse end wall 44 of one section and the second transverse end wall 46 of the other section 38 are in the extension of each other, thus forming the same continuous V-shaped wall.

This junction between the two walls 44, 46 makes it possible to improve the rigidity imparted by the stiffener 34.

In other words, the stiffener 34 is formed from a strip of fabric, a section of which forms the transverse end walls which are continuous with each other, and cut at the level of the proximal end. 40 of the sections 38 and is folded on either side of this first segment to form one or the other of the two rectilinear sections 38 of the stiffener 34.

The fabric of fibers used to form the stiffener 34 consists of an assembly of so-called warp fibers, which have a main direction according to the direction of the material to be produced, and so-called weft fibers which are oriented perpendicular to the warp figures.

In the case of the production of a stiffener 34 of curved shape, the perpendicularity of the warp fibers and of the weft fibers would be affected, one then speaks of off-framing of the fabric. To avoid this misalignment despite the curved shape of the stiffener, there are complex manufacturing processes, which would increase the production cost of the platform 18.

The realization of a stiffener 34 in two rectilinear sections 38 makes it possible to limit the unframing of the fabric, consequently ensuring a good hold of the fabric during the manufacturing process of the platform 18, and simplifies this manufacturing process compared to a process of fabrication of a platform comprising a curved stiffener.

It will be understood that the invention is not limited to a platform 18 comprising a stiffener 34 formed solely of two sections 38 and that the stiffener may comprise a greater number of sections 38, this number being defined with respect to the curvature of the main wall 20 of the platform 18.

As an example of a stiffener formed of more than two sections, FIG. 8 represents a platform comprising a stiffener formed of three sections 38.

The length of each section 38 is defined so that each section 38 of the stiffener 34 has the greatest possible width.

Claims (8)

Platform (18) of the fan (12) of the turbomachine (10), which is intended to be mounted on a hub (14) of the fan (12) between two adjacent blades (16), the platform (18) comprising
a main wall (20) having a transverse longitudinal main orientation by comprising an external face (22) intended to be in contact with a flow of air passing through the fan (12), which is of curved shape in the longitudinal direction by having curved edges (24, 26),
a stiffener (34) which is mounted on an internal face (36) of the main wall (20), which comprises an upper wall (50) which is joined against the main wall (20), and two transverse end walls ( 44, 46) offset transversely relative to each other, which extend vertically from the main wall (20), said upper wall being joined against the main wall on the one hand by transversely connecting the two walls transverse end at their outer ends located on the side of the main wall (20), and on the other hand projecting transversely with respect to the transverse end walls (44, 46),
characterized in that the stiffener (34) comprises at least two rectilinear sections (38) which are inclined with respect to each other and inclined with respect to the main longitudinal direction, the transverse end walls (44, 46 ) of each of said sections (38) having their outer edges located opposite the main wall (20) which are free so that the section of the stiffener is open opposite the main wall (20). Platform (18) according to Claim 1, characterized in that each section (38) has a proximal end (40) which is located longitudinally close to an adjacent section (38), and in that the proximal end (40 ) of each section (38) is offset transversely relative to the proximal end (40) of an adjacent section (38) in a transverse direction perpendicular to the main longitudinal direction of the main wall (20). Platform (18) according to Claim 2, characterized in that the proximal ends (40) of two adjacent sections (38) are joined longitudinally to one another. Platform (18) according to claim 1, characterized in that the first transverse end wall (44) of a section (38) and the second transverse end wall (46) of an adjacent section (38) are in continuation of each other. Platform (18) according to claim 1, characterized in that an end of the first transverse end wall (44) of a section (38), which is located at the proximal end (40) of said section (38) , is offset transversely relative to an end of the second transverse end wall (46) of an adjacent section (38), which is located at the proximal end (40) of said adjacent section (38). Fan (12) of a turbomachine (10) comprising a central hub (14) carrying blades (16) distributed around a main axis of the fan (12) and platforms (18) according to any one of the preceding claims, each platform (18) of which is fixed to the hub (14) and is arranged between two adjacent blades (16). Fan (12) according to Claim 6, characterized in that the main wall (20) of each platform (18) comprises a first edge (24) which is in contact with an underside wall of a first blade (16) and a second edge (26) which contacts an upper surface wall of a second vane (16). Fan (12) according to Claim 6 or 7, characterized in that the minimum transverse distance between the first edge (24) and the second edge (26) is greater than the width of the stiffener.