Abstract:
An annulus filler element ( 40 ) for a rotor of a turbomachine, the annulus filler element ( 40 ) comprising: a lid portion ( 42 ) having a radially outwardly facing surface for forming an inner wall of a flow annulus of the rotor between adjacent blades ( 102 ) and a radially inwardly facing surface; and a nose cone attachment portion ( 52 ) integrally formed with the lid portion ( 42 ) for connection with a nose cone ( 122 ) of the turbomachine.

Description:
BACKGROUND 
     The present invention relates to an annulus filler element for a turbomachine, in particular for the bypass fan assembly of a turbo fan engine. 
     RELATED ART 
     A conventional turbo fan engine uses the core engine to drive a bypass fan mounted near the engine intake. Fan blades on the bypass fan drive a bypass flow around the core engine which combines downstream with the core exhaust flow to provide propulsive thrust. 
     A casing assembly extends around the outside of the fan to provide an outer wall of a flow annulus through the fan. The fan blades themselves are not normally provided with blade platforms, and so a number of separate circumferential wall inserts or “annulus fillers” are mounted on the outside of the fan rotor disc, in-between the fan blades, to form the inner wall of the flow annulus through the fan. 
     The annulus fillers are typically mounted on the fan rotor disc using a hook arrangement, such as the one described in International Application PCT/GB93/00372 (published as WO93/21425). Here, each annulus filler is provided with a pair of hooks which extend radially inwardly from the filler to engage correspondingly shaped hooks provided on the outer face of the fan rotor disc. 
     A similar configuration is shown in  FIG. 1 . A blade  2  is connected to a disc  4  at a radially outer face of the disc  4  by an interlocking configuration, such as a dovetail joint. A plurality of blades  2  are assembled onto the disc  4  around the circumference of the disc  4  to form a rotor. As described previously, an annulus filler  6  is provided between adjacent blades  2  so as to form the inner wall of the flow annulus through the fan. The annulus filler  6  is mounted to the disc by a pair of annulus filler hooks  8 ,  10  which engage with correspondingly shaped disc hooks  12 ,  14 . The hook arrangement provides radial retention of the annulus filler  6  against centrifugal loads experienced during operation of the rotor. A plurality of annulus fillers  6  are provided, one between each pair of adjacent blades  2 . To ensure that the annulus filler hooks  8 ,  10  are maintained in engagement with the disc hooks  12 ,  14 , the axial position of the annulus filler  6  with respect to the disc  4  is fixed by a nose cone support ring  16 . The nose cone support ring  16  covers the full circumference of the rotor and retains each of the annulus fillers  6 . The nose cone support ring  16  is connected to an arm  18  of the disc and also to an arm  20  of the annulus filler  6 . Consequently, the axial position of the annulus filler  6  is fixed so that the hooks remain engaged. During operation, the nose cone support ring  16  also bears a component of the centrifugal load of the annulus filler  6  which creates hoop stress in the nose cone support ring  16 . 
     The nose cone support ring also functions as the primary fixation point for a nose cone of the turbomachine. The nose cone creates smooth airflow into the fan, particularly at the root of the blades, and also must be capable of withstanding bird strikes and preventing build up of ice. The nose cone  22  is located on an annular shoulder  24  of the nose cone support ring  16  and is connected at positions around the nose cone support ring  16  via abutting radial flanges  26 . 
     The connection between the nose cone support ring  16  and the nose cone  22  is enclosed by a cover portion  28 . The foremost axial end of the annulus filler  6  has a tongue portion  29  which is received under a lip portion  32  of the cover portion  28 . A similar arrangement is provided at the opposite rearmost axial end, where a tongue  33  is provided for mating with a lip  34  of a rotating seal element  35 . 
     The annulus filler  6 , nose cone support ring  16 , nose cone  22  and cover portion  28  must all be connected to one another which increases the assembly time and complexity. In addition, the connections increase the weight of the assembly and increase the risk of failure as a result of stress concentrations and misassembly of the components. 
     The present invention seeks to provide an improved annulus filler, and in particular seeks to provide an annulus filler assembly which addresses one or more of the specific problems referred to above. 
     SUMMARY 
     According to the present invention there is provided an annulus filler element for a rotor of a turbomachine, the annulus filler element comprising: a lid portion having a radially outwardly facing surface for forming an inner wall of a flow annulus of the rotor between adjacent blades and a radially inwardly facing surface; and a nose cone attachment portion integrally formed with the lid portion for connection with a nose cone of the turbomachine. 
     The integrally formed annulus filler element of the present invention provides a reduction in weight and also a reduction in assembly time. 
     The nose cone support portion may be conical. 
     The nose cone support portion may be provided with a circumferential locating ridge operable to locate the nose cone in a radial position. 
     The annulus filler element may further comprise a substantially radially extending flange integrally formed with the lid portion and nose cone attachment portion for connection with a disc of the rotor. 
     The flange may comprise a reference recess operable to locate the annulus filler element in a radial and axial position with reference to a complementary portion of the disc. 
     The flange may be connected to the disc. 
     The flange may comprise a balance tang for attachment of a balancing weight. 
     The flange may comprise a projection for retaining a slider of an adjacent blade. 
     The radially inwardly facing surface of the lid portion may have a hook extending therefrom for attachment to a disc of the rotor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example, to the following drawings, in which: 
         FIG. 1  is a side cross-sectional view of a prior art annulus filler; 
         FIG. 2  is a side cross-sectional view of a annulus filler element in accordance with the present invention; and 
         FIG. 3  is a perspective view of a portion of the annulus filler element of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     As in the prior art configuration shown in  FIG. 1 , the arrangement shown in  FIG. 2  comprises a blade  102  which is connected to a disc  104  at a radially outer face of the disc  104  by an interlocking configuration, such as a dovetail joint. A plurality of blades  102  are assembled onto the disc  104  around the circumference of the disc  104  to form a rotor. 
     An annulus filler element  40  according to the present invention is provided between adjacent blades  102  of the rotor. The annulus filler element  40  comprises a lid portion  42  having a radially outwardly facing surface which forms the inner wall of the flow annulus through the fan. The annulus filler element  40  is mounted to the disc by a pair of annulus filler hooks  108 ,  110  which engage with correspondingly shaped disc hooks  112 ,  114 . The hook arrangement provides radial retention of the annulus filler element  40  against centrifugal loads experienced during operation of the rotor. A plurality of annulus filler elements  40  are provided between each pair of adjacent blades  102 . 
     At a rearmost axial end, the annulus filler element  40  is provided with a tongue  133  which is received under a lip portion  134  of a rotating seal element  135 . 
     At a foremost axial end, the annulus filler element  40  has a flange  44  which extends radially inwardly from the lid portion  42 , as shown in more detail in  FIG. 3 . The flange  44  has a reference recess  46  formed in its surface. The reference recess  46  is dimensioned to receive a complementarily shaped arm  118  of the disc  104  which interlocks with the reference recess  46 . The flange  44  comprises two holes  47  which pass axially through the flange  44  in the location of the reference recess  46 . 
     The flange  44  terminates at a radially innermost end with a balancing tang  48 . The tang  48  has a hole  50  extending axially therethrough for receiving a bolt or other fixation means. Additionally, a protrusion  60  projects from an axially rearmost surface of the flange  44 . 
     A nose cone support portion  52  projects from the lid portion  42  and the flange  44 . The nose cone support portion  52  is adapted to receive a nose cone  122 . Conventionally the nose cone  122  has a wall of substantially uniform thickness and thus an internal surface of the nose cone  122  is also conical. The nose cone support portion  122  therefore is angled relative to the flange  44  and also curved to correspond to the conical internal surface of the nose cone  122 . A hole  54  passes through the nose cone support portion  52  and allows the nose cone  122  to be connected to the nose cone support portion  52 . 
     A ridge  56  runs across the width of the nose cone support portion  52  on a radially upper surface of the nose cone support portion  52 . The ridge  56  is positioned at or near where the nose cone support portion  52  meets with the flange  44  and lid portion  42 . The ridge  56  mates with a correspondingly shape recess in the inner surface of the nose cone  122 , as shown in  FIG. 2 . 
     When correctly located on the nose cone support portion  52 , the nose cone  122  abuts with an end face  58  of the lid portion  42  and the nose cone  122  and radially outwardly facing surface of the lid portion  42  form a substantially continuous surface. 
     The annulus filler element  40  is of one-piece construction such that the lid portion  42 , flange  44  and nose cone support portion  52  are all integrally formed with one another. 
     In use, the annulus filler element  40  is mounted to the disc  104  after the blades  102  have been assembled to the disc  104 . The annulus filler element  40  is positioned such that the hooks  108 ,  110  of the annulus filler element are engaged with the hooks  112 ,  114  of the disc  104 . In this position, the tongue  133  of the annulus filler element  40  is received under the lip  134  of the rotating seal element  135 . Furthermore, an axial portion of an arm  118  of the disc  104  is received within the reference recess  46  of the flange  44 . The axial portion of the arm  118  carries a dowel which is received in one of the holes  47  so as to fix the angular location of the annulus filler element  40 . Alternatively, the configuration may be reversed wherein one of the holes  47  is replaced by a dowel which is received in a hole on the axial portion of the arm  118 . The other of the holes  47  is used to bolt the flange  44  to the arm  118  and thus to provide axial retention of the annulus filler element  40 . 
     When in this position, the protrusion  60  from the flange  44  contacts a slider assembly (not shown) which is located between the blade  102  and the disc  104  at the base of the interlocking configuration. The protrusion  60  therefore prevents the slider assembly from being withdrawn. 
     The nose cone  122  is located on the nose cone support portion  52  with the ridge  56  received in the recess of the nose cone  122  and the nose cone  122  abutting the end face  58  of the lid portion  42 . When correctly located the holes  54  of the nose cone support portions  52  are aligned with holes in the nose cone  122  and the two can be bolted together. 
     A balancing weight may be attached to the balancing tang  48  if required to correctly balance the rotor when rotating. Alternatively, balancing of the rotor may be achieved by altering the weight of the bolts which connect the nose cone  122  to the nose cone support portion  52 , for example by using longer or shorter bolts. 
     In the prior art example, the centrifugal loads experienced by the annulus filler were carried by the nose cone support ring  16 . In the present invention the annulus filler elements  40  and thus nose cone support portions  52  are not connected to one another. However, the centrifugal loads created are instead carried by the nose cone  122 . Utilising the nose cone  122  in this manner allows the removal of the nose cone support ring  16  and thus reduces the weight of the rotor and also reduces the assembly required. 
     The nose cone  122  may not always have a conical inner surface. For example, the internal surface of the nose cone  122  may have a number of flat axial slots which define a regular polygon. Consequently, the nose cone support portion  52  may be planar and run axially. However, in all configurations the nose cone support portion  52  will be correspondingly shaped to the portion of the inner surface to which it is connected.