Abstract:
A turbomachine blade ( 10 ) comprising a body ( 11 ) and an elastomer gasket ( 12 ) fastened to said body ( 11 ).

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a turbomachine blade, to a rotor wheel fitted with such a blade, and to a turbomachine fitted with such a rotor wheel. In particular, the rotor wheel may optionally be a turbojet fan. 
       STATE OF THE PRIOR ART 
       [0002]    Structures for defining the gas passage in leaktight manner at the root of a blade within a rotor wheel generally comprise an inter-blade platform provided with a gasket that co-operates with the blade. Such a structure is described in Document FR 2 987 086. 
         [0003]    Nevertheless, it can happen that the gasket no longer performs its sealing function correctly, e.g. in the event of the gasket turning over. There therefore exists a need in this sense. 
       SUMMARY OF THE INVENTION 
       [0004]    An embodiment provides a turbomachine blade comprising a body and an elastomer gasket fastened to said body. 
         [0005]    It can be understood that the body of the blade comprises all of the blade other than the gasket. In particular, the body comprises a blade root and an airfoil. 
         [0006]    By providing a gasket on the blade rather than on an adjacent platform, the gasket is less likely to turn over in such a manner as to lose its sealing function. Specifically, in the rotor wheel fitted with said blade, the gasket co-operates with a portion that extends circumferentially (as contrasted with a portion that extends radially in the prior art), thereby making it easier to avoid unacceptable deformation of the gasket. 
         [0007]    Furthermore, by providing a gasket on the blade rather than on the platform, the gasket can extend continuously over the entire periphery of the blade, thereby improving sealing. 
         [0008]    In certain embodiments, the gasket is configured to co-operate with an inter-blade platform. 
         [0009]    This ensures that the portion of the rotor wheel with which the gasket needs to co-operate does indeed extend in the circumferential direction, thereby ensuring better sealing. For example, the gasket is configured to co-operate with a surface of a plate of a platform. 
         [0010]    In certain embodiments, the blade extends in a height direction and presents, in the height direction, a root and an airfoil, the gasket being arranged on the root and extending in a direction that is substantially perpendicular to the height direction. 
         [0011]    It can be understood that the height direction of the blade corresponds to a radial direction within a rotor wheel fitted with said blade. Furthermore, the term “direction substantially perpendicular to the height direction” should be understood as “direction forming an angle lying in the range 45° to 90° with the height direction”. It can also be understood that the gasket is a linear gasket. 
         [0012]    By arranging the gasket on the blade root, it is ensured that it does not disturb proper operation of the airfoil (i.e. does not disturb the flow of gas along the airfoil, in operation). 
         [0013]    In certain embodiments, the gasket extends around the entire perimeter of the blade. 
         [0014]    This makes it possible for the gasket to provide sealing around the entire perimeter of the blade. Sealing is thus improved. 
         [0015]    In certain embodiments, the gasket presents a linear base and a linear lip extending from the linear base, the base being fastened on the blade while the distal end of the lip presents a flyweight. 
         [0016]    In other words, the gasket is a linear gasket. It can be understood that the lip is connected to the base of the gasket while the distal end of the lip is configured to co-operate with a surface of a rotor wheel, e.g. a plate of a platform, so as to provide sealing between the blade and said surface. In operation, the flyweight serves to ensure that the distal end of the lip is pressed against said surface by the inertia effect. For example, the flyweight may be formed by extra thickness of the gasket at the distal end of the lip, e.g. by a linear rib. In another example, a linear metal portion may be embedded in the distal end of the lip. 
         [0017]    In certain embodiments, the gasket is bonded to the body. 
         [0018]    It can be understood that the gasket can be bonded with an adhesive, or by vulcanization against the surface of the blade, or by being co-cured with the blade if the blade is made of composite material, e.g. while polymerizing the composite matrix of the blade, or by any other means known to the person skilled in the art. 
         [0019]    Such a fastening technique serves to ensure complete sealing between the gasket and the body of the blade, hereby further improving the effectiveness of the gasket. 
         [0020]    In certain embodiments, the body is made of composite material. 
         [0021]    The fastening of the gasket by adhesive bonding is particularly strong when the body of the blade is made of composite material. 
         [0022]    In a first variant, the blade extends in a height direction and presents, in the height direction, a root and an airfoil, with the lip extending towards the free end of the root when considered in the height direction. 
         [0023]    It can thus be understood that the lip forms an angle lying in the range 0° to 90° with a plane perpendicular to the height direction, and extends beside the root, relative to that plane. Furthermore, such a shape provides the gasket with great robustness against any risk of turning over. 
         [0024]    In a second variant, the blade extends in a height direction and presents, in the height direction, a root and an airfoil, with the lip extending towards the free end of the airfoil when considered in the height direction. 
         [0025]    It can thus be understood that the lip forms an angle lying in the range 0° to 90° with a plane perpendicular to the height direction, extending beside the airfoil relative to that plane. Such a structure presents the advantage of being capable of being retracted completely under the platform so as not to project into the gas passage. 
         [0026]    An embodiment also provides a rotor wheel having at least one blade in accordance with any of the embodiments described in the present disclosure. 
         [0027]    For example, the rotor wheel comprises a disk having a plurality of blades mounted at its periphery, which blades may optionally be identical, and a plurality of inter-blade platforms, which platforms may optionally be identical. 
         [0028]    It can be understood that the rotor wheel extends in an axial direction, a radial direction, and a circumferential direction. In general manner, the axial direction corresponds to the direction of the axis of rotation of the rotor wheel, and a radial direction is any direction perpendicular to the axial direction. The circumferential direction corresponds to a direction describing a ring around the axial direction. The axial, radial, and circumferential directions correspond respectively to the directions defined by the z-coordinate, the radius, and the angle in a cylindrical coordinate system. Naturally, the height direction of each of the blades corresponds to a radial direction of the rotor wheel. 
         [0029]    In certain embodiments, the rotor wheel has an inter-blade platform adjacent to said blade, in which the platform presents a plate extending circumferentially while the gasket extends under said plate, considered in a radial direction. 
         [0030]    The term “under” should be understood as meaning that the gasket is radially closer to the axis of the rotor wheel than the plate. Thus, in general manner in the present description, and unless specified to the contrary, terms such as “over”/“under” should be understood as radially further away from or closer to the axis of the rotor wheel. Likewise, unless specified to the contrary, the adjectives “inner” and “outer” are used relative to a radial direction such that an inner portion (i.e. the radially inner portion) of an element is closer to the axis of the rotor wheel than an outer portion (i.e. radially outer portion) of the same element. 
         [0031]    Such a configuration makes it possible to ensure that the gasket is pressed well against the underside of the plate and co-operates properly therewith, which underside forms a surface extending circumferentially inside the rotor wheel so that the gasket does not interfere with the flow of gas through the passage defined by the blades and the platforms. 
         [0032]    In certain embodiments, the inter-blade platform has a second linear gasket fastened to the plate, said second gasket being configured to co-operate with said blade, with the second gasket extending between the gasket of the blade and the platform when considered in the radial direction. 
         [0033]    In other words, the second gasket is under the plate, while the gasket of the blade is under the second gasket. It can be understood that the gasket of the blade forms a first gasket while the gasket of the platform forms a second gasket. These two gaskets form a double barrier for opposing gas leakage and they provide good sealing. 
         [0034]    An embodiment also provides a turbomachine including a rotor wheel in accordance with any of the embodiments described in the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    The invention and its advantages can be better understood on reading the following detailed description of various embodiments of the invention given as non-limiting examples. The description is made with reference to the sheets of the accompanying figures, in which: 
           [0036]      FIG. 1  shows a turbojet presenting a fan; 
           [0037]      FIG. 2  shows a blade in a first embodiment; 
           [0038]      FIG. 3  is a fragmentary section view of the  FIG. 1  turbojet fan fitted with a blade of the first embodiment; 
           [0039]      FIG. 4  shows a blade in a second embodiment; 
           [0040]      FIG. 5  is a fragmentary section view of the  FIG. 1  turbojet fan fitted with a blade of the second embodiment; and 
           [0041]      FIG. 6  shows a variant of the  FIG. 5  fan. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0042]      FIG. 1  shows a turbomachine  100 , specifically a turbojet  100  having a rotor wheel  80 , specifically a fan  80 , fitted with blades  10  as shown in  FIG. 2  or in  FIG. 4 . In this example, all of the blades  10  and all of the platforms  20  of the fan  80  are identical. 
         [0043]    With reference to  FIG. 2 , the blade  10  extends in a height direction H, and in its height direction it presents a root  10 A surmounted by an airfoil  10 B, the root  10 A and the airfoil  10 B forming the body  11  of the blade  10 . In this example, the body  11  is made of composite material. In the height direction H, the root  10 A presents a free end  10 AA, and the airfoil  10 B presents a free end  10 BA. An elastomer gasket  12  is fastened to the body  11 , and in this example to the root  10 A. The gasket  12  is linear and extends perpendicularly to the height direction H. The gasket  12  extends over the entire periphery of the root  10 A, naturally considered perpendicularly to the height direction H. 
         [0044]    The gasket  12  presents a linear base  12 A and a linear lip  12 B connected to the base  12 A. The gasket  12  is fastened to the body via its base  12 A, which base is adhesively bonded to the body  11 . A linear rib  12 C is formed on the distal end  12 BB of the lip  12 B, thus forming a flyweight. In this example, the rib  12 C is in the form of a cylindrical bead centered on the distal end of the lip  12 B. The lip  12 B extends in the height direction H towards the free end  10 AA of the root  10 A (i.e. radially towards the inside of the wheel  80 , see  FIG. 3 ). In this example, the lip  12 B extends beside the root  10 A relative to the base  12 A. 
         [0045]    As shown in  FIG. 3 , when the blade  10  is mounted in a rotor wheel  80 , the height direction H of each blade  10  coincides with a radial direction R of the wheel  80 . The rotor wheel  80  thus extends in an axial direction X, a radial direction R, and a circumferential direction C. 
         [0046]    The gasket  12  co-operates with two inter-blade platforms  20  that are adjacent to the blade  10 . More particularly, each platform  20  presents a plate  20 B extending circumferentially, the platform  20  being mounted on the wheel  80  by conventional means (not shown), the gasket  12  co-operating with the inside circumferential surface  20 BA of the plate  20 B. Thus, the gasket  12  is arranged in the radial direction R below the plate  20 B. In operation (i.e. when the wheel  80  is rotating), the rib  12 C is pressed against the surface  20 BA of the plate  20 B by centrifugal forces, thereby ensuring good sealing between the blade  10  and the platform  20  at the blade root, under all circumstances. 
         [0047]    In general manner, it can be understood that the gasket  12  is configured to remain in contact with the platform  20 , and more particularly with the surface  20 BA under all conditions, including at rest when the wheel  80  is not rotating. 
         [0048]      FIGS. 2 and 3  correspond to the first above-described variant.  FIGS. 4, 5, and 6  show a second embodiment of the blade, corresponding to the second above-described variant. The blade in the second embodiment is identical to the blade in the first embodiment, with the exception of the elastomer gasket. Thus, only the reference signs relating to the gasket are modified, the other reference signs remaining unchanged. 
         [0049]    In  FIGS. 4 and 5 , the lip  12 ′B of the gasket  12 ′ extends in the height direction H towards the free end  10 BA of the airfoil  10 B (radially towards the outside of the wheel  80 ). In this example, the lip  12 ′B extends beside the airfoil  10 B relative to the base  12 ′A. Naturally, when the gasket  12 ′ co-operates with a platform  20 , the lip  12 ′B is folded and deforms elastically in such a manner that the lip  12 ′B extends substantially in the circumferential direction C of the wheel  80  (i.e. forming an angle lying in the range 0° to 45° relative to the circumferential direction C). More generally, when the blade  10  is mounted in a rotor wheel  80 , the gasket  12 ′ co-operates with an inter-blade platform  20  so that the lip  12 ′B extends substantially perpendicularly to the radial direction R (or the height direction H of the blade  10 ). 
         [0050]      FIG. 6  shows a rotor wheel that is modified relative to the rotor wheel of  FIG. 5 . The only modification lies in the presence of a second gasket  32  arranged on the inside surface  20 BA of the plate  20 B of the platform. Thus, compared with  FIG. 4 , the reference signs for common elements remain unchanged. 
         [0051]    The second gasket  32  is arranged radially between the plate  20 B and the gasket  12 ′ (or first gasket  12 ′) of the blade  10 . In this example, the second gasket  32  is a linear gasket presenting a second liner base  32 A fastened to the inside surface  20 BA of the plate  20 B, and a second linear lip  32 B. The second lip  32 B extends radially towards the root  10 A of the blade  10  (i.e. radially towards the inside of the wheel  80 ). The distal end  32 BA of the second linear lip  32 B co-operates with the blade  10 . Naturally, the rib  12 ′C of the first gasket  12 ′ co-operates with the inside surface  20 BA. The second lip  32 B also co-operates in part with the lip  12 ′B (or first lip  12 ′B) of the gasket  12 ′. Thus, in this example, the second gasket  32  forms firstly a second barrier for improving sealing, and also serves to block the gasket  12 ′ of the blade  10  in position so as to avoid any potential excessive deformation thereof. 
         [0052]    Naturally, the present invention is described with reference to specific embodiments, and it is clear that modifications and changes may be made to those embodiments without going beyond the general ambit of the invention as defined by the claims. In particular, individual characteristics of the various embodiments shown and/or mentioned may be combined in additional embodiments. Consequently, the description and the drawings should be considered in a sense that is illustrative rather than restrictive. 
         [0053]    For example, the first embodiment blade  10 , as shown in  FIGS. 2 and 3 , could be mounted in a rotor wheel having an inter-blade platform  20  fitted with a gasket  32  as shown in  FIG. 6 .