FR3107718A1 - Turbine assembly - Google Patents

Abstract

The present invention relates to a turbine assembly (10) for a turbine engine (1) extending around an axis, comprising a rotor assembly, a stator assembly, and sealing means, the sealing means separating a first cavity (C1) of a second cavity (C2), the turbine assembly (10) being characterized in that it comprises at least two rotor elements (121, 122) assembled by at least one screw (50 ) for fixing, said at least one fixing screw (50) comprising a threaded body (51) which extends mainly along said axis, a head (52) located in the second cavity (C2) and an acceleration device a flow of air within the second cavity (C2), the device for accelerating the flow of air comprising at least one blade (55). Figure for the abstract: Fig. 1

Description

Impeller assembly

FIELD OF THE INVENTION

The present invention relates to the general field of the sealing of a high pressure turbine of a twin-spool turbomachine, such as an aircraft turbojet. More specifically, the invention relates to a turbine assembly comprising a device for accelerating an air flow.

STATE OF THE ART

Turbomachines include a turbine recovering part of the energy released by fuel combustion to drive a fan that generates thrust.

In dual-flow turbomachines, the turbine generally consists of one or more high-pressure (HP) stages (stator-rotor) and one or more low-pressure (LP) stages.

It can be seen that a problem linked to LP turbines is the tightness control between the inter-disc cavities C1 and C2. Typically, cavity C1 is a cavity upstream of the LP turbine and cavity C2 is an open cavity downstream of the LP turbine. Traditionally, a turbine comprises a plurality of stages of which a first stage is formed by a first bladed stator (a rectifier) and other stages each formed by a bladed stator (another rectifier) and a rotor paddle wheel (another impeller) respectively. The stators are fixed to a casing of the turbine engine, the rotors rotate inside the casing of the turbine engine and are integral in rotation by being driven together in rotation via a common shaft.

The interdisc cavities mentioned are arranged between a rotor and a stator or between two rotor discs. For example, a first upstream cavity and a second downstream cavity.

The first cavity (or upstream cavity) and the second cavity (or downstream cavity) are separated by sealing means such as a labyrinth seal.

For cooling purposes, fluid is injected into the first cavity to cool the upstream of the LP turbine.

However, it is more difficult to cool cavity C3 downstream of the LP turbine with cooling air because this cavity is far from the air intake in the turbomachine (see figure 1).

Furthermore, it is sought to separate the cooling of the upstream cavity C1 of the LP turbine from the cooling which is directed towards the downstream cavity C3 of the LP turbine. Mastering the tightness at this level is however complex, because it is located at the interface between two rotors.

The document EP3234309 proposes rotors provided with blades in order to reduce the pressure at the level of a labyrinth seal. These blades make it possible to limit leaks at the level of the labyrinth seals but this document in no way aims to improve cooling towards a cavity distant from the air intake in the turbomachine and which is located downstream of the LP turbine.

In addition, the solution presented in this document has several drawbacks. On the one hand, these blades are not adjustable and therefore do not allow the pressure differential to be adjusted. In addition, the installation of these blades can be relatively tricky from the point of view of service life and mechanical strength. Indeed, adding appendages to the faces of a disc risks greatly increasing the stress concentrations in these areas, thus favoring the appearance of cracks on the disc and, seeing a dangerous event such as the release of high-energy debris.

The invention improves the situation by making it possible to carry out and control/adjust the cooling towards a cavity downstream of the LP turbine far from the air intake point in the turbomachine.

According to a first aspect, the invention proposes a turbine assembly for a turbomachine extending around an axis, comprising a rotor assembly, a stator assembly, and sealing means, the sealing means separating a first cavity of a second cavity. The turbine assembly comprises at least two rotor elements assembled by at least one fixing screw, said at least one fixing screw comprising a threaded body which extends mainly along said axis, a head located in the second cavity and a device for accelerating an air flow within the second cavity, the device for accelerating the air flow comprising at least one blade.

Said at least one fixing screw may comprise angular wedging means making it possible to adjust and lock the orientation of said at least one blade.

The blade may have a profile with a convex plane, or a profile with an asymmetrical biconvex plane, or a profile with a hollow plane.

The head of said at least one screw may include the blade.

The blade can be machined to the head or the blade can be welded or brazed to the head.

The head may include stiffeners or shelving to reinforce the head.

The head may include the angular wedging means.

The angular wedging means may comprise at least one rectilinear wall of the screw head.

The screw head may have a D-shape with a straight wall and a curved wall.

The threaded body of said at least one screw may have a thread.

The sealing means may comprise a labyrinth seal radially delimiting the second cavity on the outside.

The first cavity may be intended to cool an upstream zone of the LP turbine, and the second cavity may be intended to cool a downstream zone of the LP turbine.

According to another aspect, the invention relates to an aircraft comprising at least one turbine assembly according to the invention.

DESCRIPTION OF FIGURES

Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which must be read in conjunction with the appended drawings in which:

Figure 1 is a partial representation, in section, of a turbine assembly according to the invention, adapted to receive a fixing screw according to the invention.

Figure 2 is a perspective view of a fixing screw according to a first embodiment of the invention.

Figure 3 is a top view of a fixing screw according to a first embodiment of the invention.

Figure 4 is a side view of a fixing screw according to a first embodiment of the invention.

Figure 5 is a perspective view of a fixing screw according to a second embodiment of the invention

Figure 6 is a top view of a fixing screw according to a second embodiment of the invention.

In all the figures, similar elements bear identical references.

DETAILED DESCRIPTION OF THE INVENTION

Flow supply

The invention proposes to improve the flow rate supply to a zone downstream of the LP turbine, the supply being carried out via an air circuit which extends through the turbine assembly 10. It is specified that the cavities C1 and C2 can be located in various places of the turbine assembly, the principle of operation remaining identical. Typically, the two cavities C1 and C2 can be interdisc cavities of the turbine assembly 10. Preferably, a seal radially delimits the outside of the cavity C2, to separate an air flow which cools the upstream of the low pressure turbine of the cooling circuit, of the cooling circuit which cools the downstream part of the low pressure turbine. Typically the seal may be a 122 labyrinth seal.

The flow supply which circulates in the separate cavities C1 and C2 largely depends on the supply taken from the level of separate sampling points upstream of the turbomachine and which open into these respective cavities (see figure 1). In practice, there is a pressure differential between these cavities C1 and C2 and it is necessary to prevent the cooling flow passing through these two separate cavities to cool separate areas (Upstream of the LP turbine and Downstream of the LP turbine) of the turbomachine does not mix in order to better control the cooling carried out in the separate zones. For this purpose, the cavities C1 and C2 are separated by a labyrinth seal.

The present turbine assembly 10 improves the cooling flow circulating in the cavity C2 which feeds the downstream of the LP turbine. To this end, at least two elements 121, 122 are assembled by at least one fixing screw 50 in the cavity C2. According to the embodiment shown in Figure 1, the fixing screw 50 makes it possible to assemble two elements 121, 122. In this embodiment, the elements 121, 122 of the rotor elements.

In addition, said at least one fixing screw 50 comprises a threaded body, a head 52 and an airflow acceleration device located in the second cavity C2, the airflow acceleration device comprising at least one blade 55.

As will be detailed below, the blade 55, fixed to the rotor of the turbine assembly 10, makes it possible to increase the tangential speed of the air flow and therefore to reduce the associated pressure, which makes it possible to increase the flow from cavity C2 downstream of the LP turbine.

Fixing screw body

The fixing screw 50 is a particularly advantageous arrangement of the invention.

In a known manner, the fixing screw 50 comprises a threaded body 51 and a head 52.

The threaded body 51 is adapted to allow the assembly of several elements 121 and 122. As such, the threaded body 51 has an adequate length. It is remarkable that the screw 50 can replace a pre-existing screw of a turbine of the prior art, requiring only a few modifications. This is a particularly advantageous arrangement, since it is not necessary to carry out major and costly transformations on the turbine assembly 10 to install the screw 50.

Typically, the threaded body 51 is adapted to cooperate with a nut 80 to ensure the assembly of the two elements 121, 122.

Conventionally, the threaded body 51 may have a thread having a so-called right-hand pitch. In this case, the thread 50 (i.e. the thread) is oriented so that the nut 80 is screwed in by turning clockwise.

According to another arrangement, the threaded body 51 may have a thread having a so-called left-hand pitch. In this case, the screw thread (i.e. the thread) is oriented so that the nut 80 is screwed in by turning counter-clockwise. This arrangement can allow a better hold of the screw-nut assembly. In particular by avoiding inadvertent unscrewing (the directions of screwing and unscrewing are reversed compared to a thread on the right) and by allowing better resistance to vibrations. Indeed, depending on the topography of propagation of the vibration waves in the turbine assembly (and the direction of rotation of the turbine assembly), the nut 80 and the screw 50 will receive forces encouraging clockwise rotation. or anti-clockwise. Depending on the direction of rotation induced by the vibrations and the movement of the turbine 10, it is wise to choose a thread pitch oriented so that the nut 80 works naturally in the direction of tightening. In other words, if under the work of the vibrations and the rotation of the turbine assembly 10, the nut 80 tends to rotate counter-clockwise, it is wise to choose a left-hand thread so that that the nut 80 naturally tends to remain tight.

Head of the fixing screw – Device for accelerating an air flow

The screw head 52 is a particularly advantageous arrangement of the invention. Indeed, the head 52 can in particular comprise the device for accelerating an air flow.

The airflow acceleration device mainly includes a 55 blade.

According to the embodiments, the blade 55 may have a generally flat profile, or a profile with a convex plane, or a profile with an asymmetrical biconvex plane, or a profile with a hollow plane.

According to a particular arrangement, the blade 55 can be machined on the head 52. In other words, the blade 55 can be cut in the mass of the head 52 of screws. Typically the machining can be carried out by electroerosion, laser or milling. Several machining processes that can be combined to obtain the mechanical characteristics and the desired degree of finish. According to another arrangement, the blade 55 can be welded or brazed on the head 52.

In addition, the head 52 may include stiffeners or shelving to reinforce the attachment of the blade 55 to the head 52.

Fixing screw head – Angular wedging means

In a particularly advantageous manner, the screw head 52 also comprises angular wedging means.

The angular wedging means are a particularly advantageous arrangement of the invention. Indeed, the angular wedging means make it possible to lock an angular position chosen for the blade 55. In other words, the angular wedging means make it possible to block the screw head 52 in rotation, to block the blade 55 in (i.e. an orientation) chosen.

According to a particularly advantageous arrangement, the angular wedging means comprise at least one rectilinear wall 53 of the head 52 of the screw. Preferably, the screw head 52 may have a D-shape with a straight wall 53 and a curved wall 54.

According to the embodiments presented here, the screw head 52 has a D-shaped base partially visible in Figures 2 to 6. According to a first embodiment, shown in Figures 2 to 4, the D-shaped base is surmounted by a parallelepipedal plate 56 on which the blade 55 is positioned. According to a second embodiment, shown in Figures 5 to 6, the base (not visible in these figures) is surmounted by a cylindrical and fluted plate which is positioned the blade 55.

The rectilinear wall of the screw head 52 is adapted to rest flat against a counter-support of one of the two assembled elements. Against this support can be formed by a bore having the shape, hollow of the head 52 of the screw. According to another particular arrangement, the counter-support can be produced by a rib of one of the two elements to be assembled. As will be developed below, in conditions of use, the support of the rectilinear wall of the screw head 52, on the counter-support makes it possible to block the screw 50 in rotation. Thus, on the one hand, the screw 50 does not risk unscrewing under the effect of vibrations, and on the other hand, it is possible to define and lock the angular position of the blade 55.

Functioning - Increased pressure differential

In operation, the, or each, blade 55 is rotating within the second cavity C2, which causes the pressure within the cavity C2 to drop by p bar.

The increase in the pressure differential between the first and second cavities C1, C2 increases the supply flow in the circuit, allowing better sealing downstream of the circuit and better cooling of the parts interacting with it.

In other words, in operation, the rotation of the blade 55 increases the speed of the air flow, which has the consequence of increasing the flow of air which passes from the cavity C2 to a downstream zone C3 of the turbine. LP, and consequently the cooling of the turbine of the downstream zone C3 of the LP turbine is improved in particular because a greater quantity of air is ventilated towards the downstream zone C3 of the LP turbine.

Turbomachinery

According to another aspect, the invention relates to a turbomachine 1 incorporating a turbine assembly 10 according to the invention.

Aircraft

According to another aspect, the invention relates to an aircraft incorporating at least one turbine assembly 10 according to the invention.

Claims (13)

Turbine assembly (10) for a turbomachine (1) extending around an axis, comprising a rotor assembly, a stator assembly, and sealing means, the sealing means separating a first cavity (C1 ) of a second cavity (C2), the turbine assembly (10) being characterized in that it comprises at least two rotor elements (121, 122) assembled by at least one fixing screw (50), said at least one fixing screw (50) comprising a threaded body (51) which extends mainly along said axis, a head (52) located in the second cavity (C2) and a device for accelerating a flow of air within the second cavity (C2), the air flow acceleration device comprising at least one blade (55). Turbine assembly (10) according to claim 1 wherein said at least one fixing screw (50) comprises angular setting means making it possible to adjust and lock the orientation of said at least one blade (55). A turbine assembly (10) according to any one of claims 1 or 2 wherein the blade (55) has a convex plane profile, or an asymmetrical biconvex plane profile, or a hollow plane profile. A turbine assembly (10) according to any of claims 1 to 3, wherein the head (52) of said at least one screw (50) comprises the blade (55). A turbine assembly (10) according to claim 4 wherein the blade (55) is machined to the head (52) or the blade (55) is welded or brazed to the head (52). A turbine assembly (10) according to claim 4 or 5, wherein the head (52) includes stiffeners or shelving to reinforce the head (52). A turbine assembly (10) according to any one of claims 1 to 6 wherein the head (52) includes the angular setting means. A turbine assembly (10) according to claim 7 wherein the angular wedging means comprises at least one straight wall of the screw head (52). A turbine assembly (10) according to claim 8 wherein the screw head (52) is D-shaped with a straight wall (53) and a curved wall (54). A turbine assembly (10) according to any one of claims 1 to 9 wherein the threaded body (51) of said at least one screw (50) has a thread. Turbine assembly (10) according to any one of Claims 1 to 10, in which the sealing means comprise a labyrinth seal radially delimiting the second cavity (C2) on the outside. Turbine assembly (10) according to any one of claims 1 to 11, in which the first cavity (C1) is intended to cool an upstream zone of the LP turbine, and the second cavity (C2) is intended to cool an downstream (C3) of the LP turbine. Aircraft comprising at least one turbine assembly (10) according to any one of claims 1 to 12.