Patent Application
20200263565
The invention relates to a blade of a guide vane assembly of a turbomachine. In particular, the invention relates to a blade of a guide vane assembly fitted with a cooling system for the blade and for other parts of the turbomachine.
A turbomachine generally comprises, from upstream to downstream, one or more compressor stages, for example a low-pressure compressor and a high-pressure compressor, a combustion chamber, one or more turbine stages, for example a high-pressure turbine and a low-pressure turbine. Upstream and downstream are defined relative to the normal gas flow direction in an outflowing jet (from upstream to downstream).
The turbine converts the thermal and kinetic energy of the gas flow coming from the combustion chamber into mechanical energy required, for example, to drive the compressor and/or rotor in the case of a helicopter.
The turbine usually comprises one or more blade stages, each stage generally comprising, in a known manner, a fixed cascade called a guide vane assembly and a moving cascade. The assembly of blades in a cascade is sometimes referred to as “blading”. The blades comprise a section directed upstream, called a leading edge, and a section directed downstream, called a trailing edge.
The guide vane assembly is generally cooled by forced convection, by means of circuits running through the inside of the blades and forming a labyrinth. The cooling air enters the blades on the side of the combustion chamber of the turbine on the periphery of the combustion chamber, at a section of each blade of the guide vane assembly called the external meridian. The cooling air circulates from the external meridians and passes through the blades, so as to cool the blades on the inside (including the leading edges of the blades) up to a section of each blade of the guide vane assembly called the internal meridian, located on the side of a central hub of the turbine. The terms cooling air or cold air designate air whose temperature is lower than the temperature of the gas flowing in the outflowing jet of the turbomachine and used to lower the temperature of the elements located in the outflowing jet.
Some of the cooling air is bled at these internal meridians to be sent to the hub, so as to cool other parts of the turbine. Nevertheless, in cooling systems where the blades are cooled by means of labyrinth-type circuits, the air sent to the hub is air that has been heated at the leading edges of the blades and therefore has a higher temperature than the cooling air. In addition, the quantity of cooling air consumed is significant.
Other cooling systems include inserts or double skins, arranged inside the blades and used to cool the internal surface of the blades. In particular, the inserts comprise a wall with multiple perforations used to cool the leading edges of the blades by means of impacts of cold air. These inserts are used to reduce air consumption in relation to labyrinth-type cooling systems. In addition, the convective heat transfer coefficients are higher than those created by the labyrinth-type system. In some cases, these inserts are extended so that they cross the internal meridian in order to route some of the bleed air towards other parts of the turbine, via the hub.
However, this insert configuration causes a significant leakage of cold air at the interface between the insert and the internal meridian. The air escaping owing to this leakage is lost (particularly in the outflowing jet of gases) and does not serve to cool the blades or other parts of the turbine.
The inventors have therefore sought a way to improve the blades of existing guide vane assemblies.
The invention aims to alleviate at least some of the disadvantages of known blades.
In particular, the invention aims to provide, in at least one embodiment of the invention, a blade fitted with a cooling system that is used to effectively cool the blade and other parts of a turbomachine in which the blade is installed.
The invention also aims to provide, in at least one embodiment, a blade fitted with a cooling system limiting the consumption of cooling air.
The invention also aims to provide, in at least one embodiment, a blade fitted with a cooling system reducing the loss of cooling air.
The invention also aims to provide, in at least one embodiment, a blade fitted with a cooling system used to limit the heating of air passing through the blade in order to cool other parts of the turbomachine.
To that end, the invention relates to a blade of a guide vane assembly of a turbomachine fitted with a cooling system comprising:
A blade according to the invention thus enables, via its cooling system, a direct bleeding of some of the cooling air in the insert before it is heated by elements to be cooled. The cooling air is therefore routed into the hub, centripetally, minimising the extent to which it is heated between its arrival through the inlet of the blade and its arrival at the hub. The temperature of the air arriving at the hub is therefore close to the temperature of the air at the inlet of the insert. Once the cooling air is sent to the hub, it is used to cool other elements of the turbomachine.
In addition, the arrangement of the bleed head in the internal cavity of the blade enables the containment of potential air leakages at the opening of the insert in which the bleed head is arranged, which remain inside the internal cavity of the blade. These air leakages are thus controlled; they contribute to the cooling of the blades and the air coming from leakages is not lost.
Advantageously and according to the invention, the bleeding device comprises a bleed duct, connected on one hand to the blade by a first ball joint and designed to be connected on the other hand to a central hub of the turbomachine by a second ball joint, designed to send the bleed air coming from the bleed head to the hub of the turbomachine.
According to this aspect of the invention, the ball joint-type mechanical connections connecting the bleed duct to the blade and to the hub enable the air bled by means of the bleed head to be sent to the hub, while retaining the possibility of displacements between the blade of the guide vane assembly and the hub. These displacements are due in particular to the action of thermo-mechanical loads and may damage the bleed duct in the absence of these ball joints.
Advantageously and according to this last aspect of the invention, the bleed head and the bleed duct are integrally connected.
According to this aspect of the invention, the bleed head and the bleed duct form a single piece, called a bleed mechanism, which is easy to manufacture without needing to change the blade significantly. In this variant of the invention, the gap between the bleed head and the opening in the insert is designed to allow displacement of the bleed head, since this is integral with the bleed duct which is able to move when the blade and/or hub move, while minimising air leakage at the opening.
Advantageously and according to the invention, the bleed head and the blade are integrally connected.
According to this aspect of the invention, the bleed head is fixed, which enables the gap between the opening of the insert and the bleed head to be reduced and thus reduces air leakage at the opening. The bleed head may be formed of a section of the blade and thus be manufactured when the blade is manufactured.
The invention also relates to a guide vane assembly comprising a plurality of blades arranged around a central hub of the turbomachine, characterised in that at least one blade of the guide vane assembly is a blade according to the invention.
The invention also relates to a turbomachine, comprising a central hub and characterised in that it comprises a guide vane assembly according to the invention.
The invention also relates to a blade, a guide vane assembly and a turbomachine characterised by a combination of all or some of the features mentioned above or below.
Other aims, features and advantages of the invention will become apparent on reading the following description provided solely by way of non-limiting example and which refers to the appended figures, wherein:
The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. In the figures, scales and proportions are not strictly adhered to and this is for the purposes of illustration and clarity.
The blade 10 is fitted with a cooling system according to various embodiments described below. In
The blade 10 represented in
The cooling system comprises an insert 22, also called a double skin, arranged in an internal cavity 24 of the blade 10, and connected to a cooling air inlet 26 of the blade 10. The insert comprises micro-perforations 28 for creating impacts of cold air on the surface of the internal cavity 24 of the blade 10, in particular at the leading edge 18.
The cooling system further comprises a bleed device, comprising a hollow bleed head 30, arranged in the internal cavity 24 of the blade 10 and configured to bleed some of the cooling air inside the insert 22. To do this, the bleed head 30 passes through an opening 34 of the insert 22, so that some of the air circulating in the insert 22 enters the bleed head 30.
The gap between the opening 34 and the bleed head 30 causes leakages 36 of cooling air. Since the bleed head 30 is arranged in the internal cavity 24 of the blade 10, the air leaking due to these leakages 36 remains inside the internal cavity 24 of the blade 10 and thus participates in the cooling of the blade 10.
The bleed device further comprises a hollow bleed duct 32, designed to send the air bled inside the insert 22 coming from the bleed head 30 and to send it to the central hub 16.
The bleed duct 32 is connected on one hand to the blade 10 by a first ball joint connection 38 and on the other hand to the hub 16 by a second ball joint connection 40. In particular, the first ball joint connection 38 is located on the internal meridian 14 of the blade 10, since this section of the blade 10 is located near and facing the hub 16. The ball joint connections 38, 40 form mechanical connections enabling the blade 10 and the hub 16 to move relative to each other.
In this first embodiment, the bleed head 30 and the bleed duct 32 are integrally connected and form a single piece called a bleed mechanism.
Due to the presence of the first ball joint connection 38 between the bleed duct 32 and the blade 10, the bleed head 30 is able to move into the opening 34 of the insert 22 in the event of displacement of the blade 10 relative to the hub 16. Thus, the dimensions of the opening 34 are designed for this displacement of the bleed head 30: the gap between the opening 34 and the bleed head 30 is large enough to allow the displacement of the bleed head 30, but small enough to minimise air leakages 36. As described above, these air leakages 36 are in all cases controlled and participate in the cooling of the blade 10; they do not therefore represent a loss of cooling air.
The blade 10 represented in
This embodiment is similar to the first embodiment described above, but the bleed head 30 is not integrally connected to the bleed duct 32: the bleed head 30 is integrally connected to the blade 10, in particular at the internal meridian 14 of the blade, facing the hub 16 of the turbomachine. The bleed head 30 may for example be formed of a section of the blade 10 and manufactured with the blade 10 in the same material.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1561123 | Nov 2015 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2016/052921 | 11/10/2016 | WO | 00 |
