Patent Publication Number: US-11035255-B2

Title: Blade equipped with a cooling system, associated guide vanes assembly and associated turbomachine

Description:
TECHNICAL FIELD 
     Embodiments of the disclosure relate to a blade of a guide vane assembly of a turbomachine. In some embodiments, the disclosure relates to a blade of a guide vane assembly fitted with a cooling system for the blade and for other parts of the turbomachine. 
     BACKGROUND 
     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 some embodiments, 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. 
     SUMMARY 
     The disclosure aims to alleviate at least some of the disadvantages of known blades. 
     In some embodiments, the disclosure aims to provide, in at least one embodiment of the disclosure, 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 disclosure also aims to provide, in at least one embodiment, a blade fitted with a cooling system limiting the consumption of cooling air. 
     The disclosure also aims to provide, in at least one embodiment, a blade fitted with a cooling system reducing the loss of cooling air. 
     The disclosure 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 disclosure relates to a blade of a guide vane assembly of a turbomachine fitted with a cooling system comprising:
         an insert arranged inside an internal cavity of the blade, connected to a cooling air inlet of the blade and designed to cool the surface of the internal cavity of the blade,   a bleed device, configured to bleed some of the cooling air inside the insert and designed to send it to a central hub of the turbomachine, characterized in that the bleed device comprises:   a bleed head, arranged in the internal cavity of the blade and passing through an opening of the insert, and configured to bleed some of the cooling air inside the insert.       

     A blade according to the disclosure 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, minimizing 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 disclosure, 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 disclosure, 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 disclosure, the bleed head and the bleed duct are integrally connected. 
     According to this aspect of the disclosure, 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 disclosure, 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 minimizing air leakage at the opening. 
     Advantageously and according to the disclosure, the bleed head and the blade are integrally connected. 
     According to this aspect of the disclosure, 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 disclosure also relates to a guide vane assembly comprising a plurality of blades arranged around a central hub of the turbomachine, characterized in that at least one blade of the guide vane assembly is a blade according to the disclosure. 
     The disclosure also relates to a turbomachine, comprising a central hub and characterized in that it comprises a guide vane assembly according to the disclosure. 
     The disclosure also relates to a blade, a guide vane assembly and a turbomachine characterized by a combination of all or some of the features mentioned above or below. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of the claimed subject matter will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic perspective view of a blade of a guide vane assembly fitted with a cooling system according to a first embodiment of the disclosure; 
         FIG. 2  is a schematic cross-sectional view of a blade of a guide vane assembly fitted with a cooling system according to a first embodiment of the disclosure; and 
         FIG. 3  is a schematic cross-sectional view of a blade of a guide vane assembly fitted with a cooling system according to a second embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
       FIGS. 1 to 3  schematically represent, as a perspective view for  FIG. 1  and as a cross-sectional view for  FIGS. 2 and 3 , a blade  10  of a guide vane assembly of a turbomachine. The blade  10 , as arranged in a turbomachine, comprises a section called an external meridian  12  located on the side of a combustion chamber (not represented) of the turbomachine, and a section called an internal meridian  14  located on the side of a central hub  16  of the turbomachine around which the rotational parts of the turbomachine turn. In addition, a gas passes through the turbomachine from upstream to downstream, and the section of the blade  10  directed upstream is called the leading edge  18  and the section of the blade  10  directed downstream is called the trailing edge  20 . The blade  10  is fitted with a cooling system according to various embodiments described below. In  FIGS. 1 to 3 , arrows partially represent the circulation of the cooling air in the various elements of the blade  10  and/or of the cooling system. 
     The blade  10  represented in  FIGS. 1 and 2  is fitted with a cooling system according to a first embodiment of the disclosure. 
     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 some embodiments, 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 minimize 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  FIG. 3  is fitted with a cooling system according to a second embodiment of the disclosure. 
     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. 
     The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure which are intended to be protected are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure, as claimed.