Abstract:
An air bleed device for cooling components in a turbine engine, including an annular conduit having a substantially rectangular cross-section formed in a housing and having a radially internal wall swept by an airflow is disclosed. The device includes an air inlet orifice, and a flap valve for controlling the airflow entering through the orifice, formed by a plate borne by a maneuvering member mobile in translation parallel to the axis of the orifice between a position in which the plate closes off the orifice and a position in which the plate opens the orifice.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a cooling air bleed device in a turbine engine, such as an airplane turbojet, which is intended in particular for cooling flaps of a convergent-divergent jet nozzle. 
     The jet nozzle of a turbojet generally comprises mobile flaps that are subjected to strong thermal stresses due to the passage of very hot gases coming from the combustion chamber of the turbomachine. These thermal stresses generate large amounts of infrared radiation capable of hindering the stealth of military aircraft and that should be minimized. 
     A solution consists of bleeding cold air in a secondary flow of the turbomachine, so as to direct it toward the flaps of the nozzle and cool them. 
     2. Description of the Related Art 
     The patent application EP 1 522 680 of the applicant describes a system for ventilating mobile flaps of a convergent-divergent nozzle of an airplane turbojet, which system includes an annular conduit supplied with cooling air through orifices provided in a wall separating the interior of the conduit from the downstream end of an annular passage surrounding a post-combustion chamber of the turbojet and in which a cooling airflow circulates. This ventilation system also includes air distribution cells distributed around the conduit and connected thereto, and telescopic channels each connecting a cell to a divergent nozzle seal located in the same plane of symmetry as the cell. 
     The disadvantage of this system is that it does not enable the bled airflow to be modulated. 
     This air bleed adversely affects the performance of the turbojet and is generally unnecessary in all phases of the aircraft flight. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is intended in particular to provide a simple, economical and effective solution to this problem, in particular enabling the airflow bled to be modulated at will in order to cool the nozzle. 
     It relates in particular to means for supplying cooling air in a turbomachine, located at a short distance upstream of the nozzle flaps, and which are capable of withstanding significant mechanical stresses generated by the thrust of gases in this location, and significant deformations of the nozzle due to high thermal stresses. 
     The invention also relates to means for supplying cooling air that are low profile and relatively lightweight, and that enable disturbances in the airflows flowing into the turbomachine to be limited, so as to optimize the performance of the turbine engine. 
     It also relates to cooling air supply means that are manually controlled by the airplane pilot. 
     The invention thus proposes a cooling air bleed device for cooling components in a turbomachine, including an annular conduit formed in a housing and having a radially internal portion that is swept by an airflow moving from upstream to downstream and that comprises at least one air inlet orifice with a radial axis, which device includes a flap valve for controlling the airflow entering through the orifice, and wherein the flap valve is formed by a plate held at its periphery by a maneuvering member outside the orifice and mobile in translation parallel to the axis of the orifice between a position in which the plate is applied on the edge of the orifice and closes off said orifice and a position in which the plate is moved away from the orifice and opens said orifice. 
     In the closing position, the plate is held against the edge of the orifice and closes the latter tightly under the pressure of the airflow. 
     The opening and closing of the plate result from a translation movement of the latter according to the axis of the orifice, thereby enabling the wear of its surface applied on the edge of the orifice in the closing position to be minimized, and therefore the lifetime of the device to be improved. 
     According to another feature of the invention, the airflow is guided toward the orifice of the conduit by an oblique wall attached to the housing by means forming a stop limiting the movement of the plate of the flap valve in the direction of opening of the orifice. 
     The oblique wall enables the movement of the airflow to be facilitated and the disturbances and head losses thereof to be limited, thereby enabling the performance of the turbomachine to be optimized. 
     The surface of the plate of the flap valve intended to be applied on the edge of the orifice advantageously comprises a seal, which preferably has a stainless steel sheet structure inserted between graphite layers or a graphite metal screen structure. 
     According to another feature of the invention, the maneuvering member includes a ring with a cylindrical internal threaded surface, cooperating with means formed in the housing for guiding the ring in translation and locking it in rotation, with an end of the ring being connected to an end of the plate of the flap valve. 
     The locking in rotation of the ring can enable the latter to be driven in translation by a screw-nut effect, as demonstrated below. 
     The means for locking the ring in rotation preferably include at least one lug or a longitudinal rib engaged in a longitudinal groove formed on the external surface of the ring. 
     Alternatively, the ring has an external polygonal cross-section and is housed in a cavity of the housing which extends parallel to the axis of the orifice and which has an internal cross-section substantially identical to the external cross-section of the ring in order to lock the ring in rotation. 
     According to another feature of the invention, the valve includes a toothed wheel for rotating a threaded rod screwed into the ring of the maneuvering member and held securely in translation by the housing. 
     The threaded rod cooperates with the internal threading of the ring in order to drive the ring in translation by a screw-nut effect. The aforementioned means for locking the ring in rotation participate in this screw-nut effect, by preventing the rotation of the ring and by guiding it according to a pure translation movement. 
     The toothed wheel is rotated by controlled means, including for example a flexible cable maneuvered by a cylinder. 
     The valve advantageously includes a disengageable connecting ring that is mounted coaxially and superimposed on the toothed wheel and secured in rotation with the threaded rod, and that comprises teeth with oblique flanks intended to cooperate by meshing with teeth having a conjugated shape formed at one end of the toothed wheel opposite the teeth of the connecting ring, and the valve also preferably includes resilient return means axially pushing the teeth of the toothed wheel engaged with those of the connecting ring. 
     During opening or closing of the flap valve, when the latter reaches the end of course against the means forming a stop or against the edge of the orifice, the connecting ring enables the rotation of the toothed wheel to be decoupled from that of the threaded rod, and therefore from the translation of the flap valve maneuvering member, so that the toothed wheel can optionally continue its rotation without risk of damaging the flap valve. 
     According to another feature of the invention, the air bleed device is installed on the housing of the turbine engine in order to cool control flaps of a jet nozzle, and it preferably includes a series of flap valves that are distributed uniformly around the axis of the turbomachine and a control actuator connected to the flap valves by synchronous drive means, such as, for example, a flexible cable or a ball cable, connected in series to the flap valves. 
     The flap valves of the air bleed device described above enable a simple movement of means for driving these valves to be converted into a movement of opening or closing of each of the flap valves, thereby enabling control of the device by a single simple drive means, which can moreover advantageously be chosen to be flexible, such as a ball cable, so that this device withstands deformations of the housing on which it is mounted and any mechanical stresses generated by the pressure of surrounding gases. The valves of the air bleed device according to the invention are capable of being used under these conditions, in particular temperature, which prohibit the use of electrical control valves, as is for example the case in the vicinity of a turbojet nozzle. These valves also have the advantage of having a low profile, and thus enabling the aerodynamic impact of the air bleed device on the flow of gases in the vicinity of the device to be limited. These valves are moreover uniformly distributed around the housing so as to enable uniform air bleed all around said housing. 
     The invention also relates to a turbine engine equipped with an air bleed device of the type described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be easier to understand, and other details, advantages and features thereof will become clearer in view of the following description, provided by way of a non-limiting example, in reference to the appended drawings, in which: 
         FIG. 1  is a partial diagrammatic view of an air bleed device according to the invention mounted on a turbojet nozzle with a closed flap valve; an upper left-hand portion of this figure is a frontal view while the remainder of the figure is a cross-section view according to a median axial plane of a valve of said device; 
         FIG. 2  is a partial diagrammatic cross-section in perspective of the jet nozzle equipped with the air bleed device of  FIG. 1 ; 
         FIG. 3  is a partial diagrammatic view of an air bleed device according to the invention mounted on a turbojet nozzle with an open flap valve; an upper left-hand portion of this figure is a frontal view while the remainder of the figure is a cross-section view according to a median axial plane of a valve of said device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference is first made to  FIG. 1 , which shows a cooling air bleed device  10  mounted on the housing  12  of the afterbody of an airplane bypass turbojet comprising a post-combustion chamber  14 , upstream of controlled flaps and nozzle seals of a jet nozzle, equivalent to the device described in document EP 1 522 680 cited above. 
     The device  10  includes an air circulation chamber  16  defined by a conduit  18  having a general annular shape and a rectangular axial cross-section, formed on the external surface of the housing. This conduit  18  includes orifices  20  with a radial axis  21  formed in its radially internal wall  22  and intended for bleeding cooling air onto a secondary cool airflow  24  moving from upstream to downstream around an annular wall  26  defining the post-combustion chamber, in which the conduit  18  also includes other orifices  28  formed in its radially external wall  30  and connected to means  32  for routing and diffusing the air over the nozzle flaps to be cooled, in which said means  32  can, for example, be of the type described in the aforementioned prior art document. 
     An annular wall  34  extends between the downstream end of the external wall  26  of the post-combustion chamber  14  and the radially internal wall  22  of the conduit  18 . This wall  34  is attached by rivets  36  to an annular flange  38  formed at the downstream end of the radially internal wall  22  of the conduit, and divides the secondary cool air flow  24  into a radially external flow intended to supply the bleed device  10  in order to cool divergent flaps of the nozzle, and a radially internal flow intended to cool convergent flaps of said nozzle, as already described in the aforementioned prior art. 
     According to the invention, the radially internal wall  22  of the annular conduit  18  includes flat portions in which the aforementioned air inlet orifices  20  are formed, so that the latter are flat. 
     To enable control of the cooling airflow bled, each air inlet orifice  20  is closed off by a flap valve  40 , which includes means for driving a flapper  42  of the valve in translation according to the axis  21  of the orifice, between a position of opening shown in  FIG. 3 , and a position of closing the orifice  20  by said flapper  42  shown in  FIG. 1 , as described in greater detail below. 
     The flapper  42  includes an external circular disk  44  with a larger diameter, perpendicular to the axis  21  of the orifice and of which the periphery is intended to be applied against a seat or an edge of the orifice  20  in order to close off the latter, and an internal disk  46  with a smaller diameter formed on the external disk  44 . The periphery of the external disk  44  intended to be applied against the edge of the orifice  20  is covered by a seal  47 , made for example of a stainless steel sheet inserted between two graphite sheets, according to a structure sometimes called “Papiex”. The seal can also be graphite with a metal screen. 
     The external disk  44  of the valve is secured at its periphery to a lug  48  forming the closed end of a ring  50  intended to maneuver the flapper  42  in order to open and close the orifice  20 . 
     This ring  50  is housed, centered and guided in a path with a square internal cross-section  52  having an axis  54  substantially parallel to the axis  21  of the orifice  20  and formed on the external surface of the housing  12 . 
     The ring  50  is mobile in translation according to the axis  54  and has a square external cross-section substantially conjugated with the internal cross-section of the vent  52 . 
     At its end opposite the lug  48  of the flapper, the ring  50  comprises a cylindrical internal threaded channel  56  into which the threaded end  58  of a rod  60  rotationally mounted in the vent  52  is screwed. 
     The rod  60  comprises a circular collar  62  intended to enable it to be locked in translation parallel to the axis  21  of the orifice in the radially outward direction of the turbojet, i.e. toward the top of  FIG. 1 . For this, the vent  52  comprises, at its radially external end, a shoulder  64  of its internal surface against which the collar  62  abuts. 
     The locking of the rod  60  in translation radially inwardly with respect to the turbojet is ensure by rotating members mounted on a portion of the rod outside the vent  52 , as will be demonstrated more clearly below. 
     To facilitate the guiding of the rod  60  in rotation, a sleeve  66  with a cylindrical internal cross-section is mounted around the rod  60  so as to be interposed between the rod and the shoulder  64  of the vent  52 . The sleeve  66  has a square external cross-section conjugated with the internal cross-section of the shoulder  64  of the vent, and comprises a collar  68  with a square external cross-section conjugated with the internal cross-section of the vent, with said collar  68  being interposed between the collar  62  of the rod and the shoulder  64  of the vent. 
     The collar  62  of the rod  60  divides the latter into a first threaded portion  58  extending into the vent  52  and screwed into the internal channel  56  of the ring  50 , and a second portion  70  extending outside of the vent  52  and bearing a toothed wheel  72  for driving in rotation. 
     The toothed wheel  72  has radial teeth  74  intended to be engaged with suitable drive means  76 , of which an example will be described in greater detail below, and which are shown diagrammatically in  FIG. 1  by teeth  78  cooperating by meshing with the teeth  74  of the toothed wheel  72 . This toothed wheel is also held on the rod  60  by a nut  80  screwed at the end of the latter. 
     The valve  40  advantageously includes a disengageable connecting ring  82  coaxial to and superimposed on the toothed wheel  72 , and comprising teeth with oblique flanks  84  intended to cooperate by meshing with teeth  86  having a conjugated shape formed at one end of the toothed wheel  72  opposite the teeth  84  of the connecting ring  82 . 
     Resiliently deformable washers  88 , such as wave or frustoconical washers, for example numbering three, are interposed between the toothed wheel  72  and its retaining nut  80  on the rod  60 , in order to axially push the teeth with oblique flanks  86  of the toothed wheel  72  against the teeth  84  of the connecting ring  82  and thus cause the toothed wheel to be rotationally secured with the connecting ring. 
     The connecting ring  82  includes splines (not visible in  FIG. 1 ) extending radially over its internal face and cooperating with splines (also not visible) with a substantially conjugated shape formed on the second portion  70  of the rod  60  in order to transmit to said rod the rotating movement of the connecting ring  82 , and therefore that of the toothed wheel  72 . Alternatively, the connecting ring  82  can be welded to the second portion  70  of the rod  60 . 
     To facilitate the rotation of the connecting ring  82  and prevent the wear thereof as well as the wear of the external surface of the vent  52 , a metal washer  90  or a resilient material is interposed between the radially internal face of the connecting ring and the edge of the orifice of the vent  52 . The washer  90  also opposes the translation of the rod  60  radially inwardly with respect to the turbojet. 
     The device according to the invention works as follows: with the valve  40  initially in its closure position shown in  FIG. 1 , it is simply necessary, in order to cause the opening of the orifice  20  and the entrance of cool air into the conduit  18 , to rotate the toothed wheel  72  in the direction of unscrewing of the threaded portion  58  of the rod  60  from the internal channel  56  of the ring  50 , owing to suitable drive means  76 . 
     In consideration of the locking in rotation of the ring  50  and the locking in translation of the rod  60  radially outwardly with respect to the turbojet, the rotation of the rod  60  in the direction of unscrewing of its threaded portion  58  drives a translation of the ring  50  toward the interior of the turbojet parallel to the axis  21  of the orifice  20 . The ring  50  drives with it the flapper  42  to which it is secured, until the downstream end of said flapper abuts against the radially external surface of the annular flange  38 . 
     In the opening position of the orifice  20 , the annular wall  34  ensures the guiding of the air toward the interior  16  of the conduit  18 . 
     The closing of the orifice  20  by the flapper  42  is performed by rotating the toothed wheel  72  in the direction of screwing of the threaded portion  58  of the rod  60  in the internal channel  56  of the ring  50 , until the seal  47  of the flapper is applied against the edge of the orifice  20 . 
     In a maneuver of the flapper  42  caused by the rotation of the toothed wheel  72 , the disengageable connecting ring  82  transmits the rotation of the toothed wheel  72  to the rod  60 . 
     When the flapper  42  reaches its closing position in contact with the edge of the orifice  20  or when it reaches its maximum opening position in which its downstream end abuts against the annular flange  38 , the ring  50  can no longer move in translation. 
     The connecting ring  82  then enables the rotation of the toothed wheel  72  to be decoupled from that of the rod  60 , if the toothed wheel  72  continues to be driven in rotation by the drive means  76 . Indeed, the locking in translation of the ring  50  prevents the rotation of the rod  60  and therefore of the connecting ring  82 , which is secured in rotation with said rod  60 . The force exerted by the rotational drive means  76  of the toothed wheel  72  is then converted into an axial force oriented radially outwardly by the respective teeth with oblique flanks  84  and  86  of the connecting ring and the toothed wheel, which force tends to move the toothed wheel  72  away from the connecting ring  82  while causing a compression of the resiliently deformable washers  88 . 
     The disengageable connecting ring  82  thus enables the risks of damage of the air bleed device  10  to be minimized if the toothed wheel  72  is driven beyond the limits of the course of the flapper  42  or the ring  50 , and thus prevents the need for sophisticated control means for controlling the drive means  76  of the toothed wheel  72 . 
     To prevent the flapper  42  or its lug  48  for connection to the ring  50  from being subjected to excessive mechanical stresses when the orifice is closed, and to prevent the rod  60  from being moved in translation radially inwardly with respect to the turbojet, causing compression of the resiliently deformable washers  88  by the nut  80 , in the closing position, it is preferable for the ring  50  to have an axial range such that, when the flapper is in the closing position, the open end of said ring abuts against the shoulder  64  of the internal surface of the vent  52  and/or against the collar  62  of the rod  60 , as in  FIG. 1 . This also enables any clearance at the opening of the orifice to be prevented. 
     In addition, the external cross-section of the ring  50  and the internal cross-section of the vent  52  may be not square but rectangular, or more generally polygonal, so as to enable the ring  50  to be locked in rotation. 
     Alternatively, the ring  50  and the vent  52  can be cylindrical, and the locking in rotation of the ring  50  is in this case ensured by a rib/groove cooperation between the ring  50  and the vent  52 . For example, the internal surface of the vent  52  can comprise a rib extending according to the axis  54  of the vent and engaged in a groove with a conjugated shape formed on the external surface of the ring  50  in order to prevent the rotation of the latter. 
       FIG. 2  shows an overview of the cooling air bleed device  10  described above, and more specifically shows two valves  92  and  94  of this device and means for controlling these valves. The toothed wheel of each valve of the device is protected by a cylindrical fairing  96  comprising a rectilinear aperture  98  for the passage of a drive member, such as a flexible cable or a ball cable  100  in order to drive the toothed wheel. The cable  100  is actuated by a cylinder  102  mounted on the housing  12  of the nozzle and connected to an end  104  of the cable, with the other end  106  of said cable  100  being free at the outlet of the last valve  94  controlled by said cable. 
     The air bleed device  10  according to the invention provides the possibility of controlling all of the valves distributed around the nozzle in a synchronized manner by means of a single control actuator, in order to cool the controlled turbojet nozzle flaps, in which the control of this device can be performed manually by the airplane pilot. 
     The use of a flexible cable  100  in order to transmit the control movement of the actuator  102  to the toothed wheels  72  of the valves enables the system to withstand deformations of the housing  12  on which it is mounted while resisting the mechanical and thermal stresses generated by the flow of gases around said system. 
     In addition, such a cable  100  does not have to be in a closed circuit, and its end opposite the control cylinder  102  can remain free as already mentioned, thereby allowing for an advantageous weight gain.