Abstract:
A floating collar assembly for a gas turbine engine combustor includes a ferrule having a peripheral wall and a recessed surface bounded by the peripheral wall, the recessed surface of the ferrule including a particulate collecting groove adjacent the peripheral wall, and a cap secured to the peripheral wall of the ferrule. The recessed surface of the ferrule, an interior surface of the cap and the peripheral wall of the ferrule define a cavity. A floating collar is disposed within the cavity and includes a peripheral flange inwardly spaced a distance from the peripheral wall of the ferrule.

Description:
TECHNICAL FIELD 
       [0001]    The disclosure relates generally to gas turbine engine combustors, and more particularly to floating collars for igniter and/or fuel nozzles of such combustors. 
       BACKGROUND 
       [0002]    Gas turbine combustors are typically provided with floating collar or seal assemblies for mounting igniters or fuel nozzles to the combustor, in order to facilitate movement of igniters or fuel nozzles relative to the combustor shell and/or permit thermal growth differential therebetween during engine operation. The floating collar may also reduce loading on the igniter, fuel tubes and fuel nozzles mounted to the combustor thereby, which might otherwise be generated from vibration, thermally induced and stress induced combustor movement relative to the adjacent supporting structures. 
         [0003]    Such floating collars may be retained within enclosed bosses mounted to the combustor. However, such enclosed bosses may be prone to obstruction by sand or other airborne particulate debris. Accordingly it is desirable to prevent particulate accumulation in spaces surrounding a floating collar. 
       SUMMARY 
       [0004]    There is accordingly provided a floating collar assembly for a gas turbine engine combustor, the floating collar assembly comprising: a boss assembly including first and second portions assembled to provide a peripheral wall and spaced apart top and bottom walls collectively defining a cavity therebetween, the top and bottom walls each having a central opening therein aligned with one another, and at least one of the top and bottom walls including a recessed particulate collecting groove adjacent to the peripheral wall; and a floating collar within the boss assembly and having a peripheral flange received within the cavity and an opening extending axially therethrough aligned with the central openings of the top and bottom walls, a periphery of the peripheral flange proximate the particulate collecting groove being spaced inwardly from the peripheral wall of the boss assembly a selected distance, the selected distance chosen based on an expected size of particulate ingested into the floating collar assembly. 
         [0005]    There is also provided a combustor for a gas turbine engine combustor having a floating collar assembly, the floating collar assembly comprising: a boss assembly including a ferrule and a cap secured together and cooperating to defined a cavity therewithin, the ferrule having a central axis, an opening extending axially therethrough, a peripheral wall and a recessed surface bounded by the peripheral wall, and the cap having an opening extending axially therethrough and a periphery secured to the peripheral wall of the ferrule, wherein the recessed surface of the ferrule, an interior surface of the cap and the peripheral wall of the ferrule define the cavity; and a floating collar trapped within the cavity of the boss assembly and having an opening extending axially therethrough in alignment with the openings of the ferrule and cap and a peripheral flange, the peripheral flange of the floating collar inwardly spaced a distance from the peripheral wall of the ferrule; wherein the recessed surface of the ferrule includes a particulate collecting groove adjacent the peripheral wall. 
         [0006]    There is alternately provided a floating collar assembly for a gas turbine engine, the floating collar assembly comprising: a ferrule assembly having first and second halves assembled to provide spaced apart walls defining a cavity between them, the walls each having a central opening aligned with the other, at least one of the walls including one or more sand collecting grooves extending substantially around the respective central opening; and a floating collar having a peripheral flange received within the cavity and an opening extending axially therethrough aligned with said wall central openings, a periphery of the peripheral flange spaced inwardly from a peripheral wall of the ferrule assembly a sufficient distance to allow sand to pass between the periphery of the peripheral flange and the peripheral wall. 
         [0007]    There is also alternately provided a floating collar assembly for a gas turbine engine combustor comprising: a ferrule having a central axis, an opening extending axially therethrough, a peripheral wall and a recessed surface bounded by the peripheral wall, the recessed surface of the ferrule including a particulate collecting groove adjacent the peripheral wall; a cap having an opening extending axially therethrough and being secured to the peripheral wall of the ferrule, whereby the recessed surface of the ferrule, an interior surface of the cap and the peripheral wall of the ferrule define a cavity; and a floating collar received within the cavity and having an opening extending axially therethrough and a peripheral flange inwardly spaced a distance from the peripheral wall of the ferrule. 
         [0008]    There is further alternately provided a combustor for a gas turbine engine combustor having a floating collar assembly comprising: a ferrule having a central axis, an opening extending axially therethrough, a peripheral wall and a recessed surface bounded by the peripheral wall; a cap having an opening extending axially therethrough and being secured to the peripheral wall of the ferrule, whereby the recessed surface of the ferrule, an interior surface of the cap and the peripheral wall of the ferrule define a cavity; a floating collar having an opening extending axially therethrough and a peripheral flange inwardly spaced a distance from the peripheral wall of the ferrule, the flange disposed within the cavity; and wherein the recessed surface of the ferrule includes a particulate collecting groove adjacent the peripheral wall. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Reference is now made to the accompanying Figures, in which: 
           [0010]      FIG. 1  is a schematic cross-sectional view of a gas turbine engine; 
           [0011]      FIG. 2  is sectional isometric view of a ferrule of a floating collar assembly having a particulate collecting groove adjacent the peripheral wall and a particulate ejection slot in a downstream end; 
           [0012]      FIG. 3  is a perspective view of the ferrule of  FIG. 2 , showing the complete particulate collecting groove and the particulate ejection slot; 
           [0013]      FIG. 4  is a perspective view of the floating collar used with the ferrule of  FIGS. 2-3 ; 
           [0014]      FIG. 5  is a perspective view of the floating collar assembly, having a boss assembly including the ferrule of  FIGS. 2-3  and a cap assembled therewith, and the floating collar of  FIG. 4  disposed within the boss assembly; 
           [0015]      FIG. 6  is a cross-sectional perspective view of the floating collar assembly taken along line  6 - 6  of  FIG. 5 , with the cap removed to illustrate the particulate collecting groove and particulate ejection slot; 
           [0016]      FIG. 7  is a cross-sectional view of the following collar assembly of  FIG. 5  with the cap in place, showing the containment of the floating collar, the particulate collecting groove and particulate ejection slot; and 
           [0017]      FIG. 8  is a partial detail sectional isometric view of the floating collar assembly of  FIG. 7 , showing the particulate collecting groove and particulate ejection slot in the downstream end of the ferrule. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  illustrates a gas turbine engine  10  of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan  1  enclosed by a fan case  2  and through which ambient air is propelled, a multistage compressor  4  for pressurizing the air, a combustor  8  in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section  9  for extracting energy from the combustion gases. Although a turbofan engine is depicted, it will be understood however that the gas turbine engine  10  as described herein may comprise other types of gas turbine engines such as turbo-shaft, turbo-prop and/or auxiliary power units. A longitudinal engine centerline  11  extends through the center of the engine  10 , and at least the rotating components of the fan  1 , the compressor section  4  and the turbine section  9  are concentric with and rotate about the engine centerline  11 . 
         [0019]    Referring still to  FIG. 1 , fuel is supplied to the combustor  8  through fuel tubes  7  and fuel is mixed with compressed air when sprayed through fuel nozzles  12  into the combustor  8  as a fuel air mixture that is ignited. Multiple fuel nozzles  12  and at least one igniter  13  are attached to and extend through the combustor liner into the combustion chamber within the combustor  8 . 
         [0020]    One or more of the fuel nozzles  12  and the igniter  13  may include a floating collar assembly  18  as described herein. The floating collar assembly  18  includes an at least partially enclosed boss assembly and provides particulate buildup prevention, as will be described in further below. The floating collar assembly  18  is applicable to fuel nozzles  12  which pass through the end combustor shell wall and to igniters  13  which pass through the outer combustor shell wall. In both cases, compressed air flows within a plenum surrounding the combustor and passes over the floating collar assemblies  18  that engage the fuel nozzles  12  and igniter  13 . The air flow may contain sand and/or other airborne particulate material (herein, simply referred to as “particulate” material) that may become trapped and accumulate within the floating collar assembly. The floating collar assembly  18  as described herein therefore seeks to prevent or reduce the build up of such particulate material therewith, and limit any possible reduction in the efficacy of the floating collar. 
         [0021]    As seen in  FIG. 1 , the igniter  13  may mounted with a mounting flange to the plenum wall and extends through the three part floating collar assembly  18  described below into an opening defined in the combustor wall which is part of the combustor  8  of  FIG. 1 . 
         [0022]    Referring first to  FIG. 5 , the floating collar assembly  18  includes generally a boss assembly  19  and a floating collar  28  trapped within the boss assembly. The boss assembly  19  includes at least first and second portions  27  and  29 , which in the depicted embodiment comprise a ferrule  27  and a cap  29  secured thereto. The floating collar assembly  18  can be applied to both ignitors  13  and fuel nozzles  12 . 
         [0023]    Referring now back to  FIGS. 2 to 4 , the ferrule  27  of the boss assembly  19  and the floating collar  28  are shown in isolation. More particularly, the ferrule  27  of the boss assembly  19  is shown in  FIGS. 2-3 . The other portion of the boss assembly  19 , namely the cap  29 , is secured to the ferrule  27  of the boss assembly  19  as can be seen in  FIG. 5 . The floating collar  28  is shown in  FIG. 4 . 
         [0024]    Referring to  FIG. 4 , the floating collar  28  has a central collar that slides on the outer surface of the igniter  13  and an outer flange  20  that is contained within a space defined by the peripheral walls of the ferrule  27 , the recessed surface  24  of the ferrule  27  bounded by the peripheral walls  23  and the inner surface of the cap  29 . While providing an air flow seal, relative movement between the igniter  13  and the combustor wall are accommodated by axial sliding of the floating collar  28  on the igniter  13 , and by lateral sliding of the flange  20  within the space defined by the peripheral walls  23  of the ferrule  27 , the recessed outer surface  24  of the ferrule  27  and the inner surface of the cap  29 . 
         [0025]    The floating collar assembly has a shape chosen for preventing rotation with a circular upstream half to reduce air flow resistance and a square downstream half with rounded corners to prevent rotation of the floating collar  28 . As shown in  FIGS. 6-8  the gap  21  surrounding the outer edges of the flange  20  inward of the peripheral wall  23  allows the floating collar  20  to move laterally a limited distance. 
         [0026]    The sealing between the igniter  13  and combustor wall is imperfect and leakage gaps exist all around the flange  20  of the floating collar  28  shown with arrows in  FIGS. 7-8 . To permit lateral movement of the floating collar  28  with minimal frictional resistance, the thickness dimension of the flange  20  must be less than the height dimension of the space defined between the cap  29  and the recessed surface  24  of the ferrule  27 . 
         [0027]    Since the air flow can carry sand and other airborne particulate, the air flow through gaps in the floating collar assembly can result in trapping and accumulation particles which then block the lateral movement of the floating collar  28  and defeat the purpose of the floating collar assembly. Particulate accumulation can also lead to surface abrasion, friction and wear. 
         [0028]    Referring to  FIGS. 5-8 , the assembled ferrule  27 , floating collar  28  and cap  29  are shown. The recessed surface  24  of the ferrule  27  bounded by the peripheral wall  23  includes a particulate collecting groove  25  and a particulate ejection port  26  in a downstream end of the ferrule  27 . Air flow direction through the plenum upstream to downstream is indicated with large arrows in  FIGS. 7-8 . Leakage air flow through the floating collar assembly which carries particulate into the groove  25  is indicated with thin arrows in  FIGS. 7-8 . 
         [0029]    Particulates carried by the air flow are directed through gravity and air flow into the groove  25 . Lateral movement of the floating collar  28  towards the groove  25  also pushes the particulates into the groove  25 . The outer edge of the floating collar  28  is shown chamfered at a 45 degree angle to aid in pushing particulates to the groove and to prevent particles from wedging between the floating collar  28  and the ferrule  27 . 
         [0030]    The particulate collecting groove  25  at a downstream end communicates with the particulate ejection port  26 . Compressed air flow through the floating collar assembly follows a tortuous leakage path (shown in thin arrows in  FIGS. 7-8 ) passing over the floating collar  28 , through the groove  25  and out the particulate ejection port  26  taking particles with it. 
         [0031]    The particulate collecting groove  25  is shown in the drawings encircling the ferrule  27  inward of the peripheral wall  23 . However the groove  25  could be limited to the downstream half of the ferrule  27 . The outer edge of the floating collar  28  is shown chamfered but could be tapered, stepped or rounded to similar effect. The remaining portions of the flange  20  of the floating collar  28  have a uniform thickness. 
         [0032]    The ferrule  27 , cap  29  and floating collar  28  have a rectangular downstream end to prevent rotation of the floating collar  28  and a half circular shaped upstream end as illustrated, however any alternative shape that would prevent rotation is equally applicable. The groove  25  is shown with a rectangular cross sectional profile and has a continuous or common bottom surface with the particulate ejection port  26  for ease of manufacture and effective clearing of particles ejected out of the groove  25 . 
         [0033]    Although the above description relates to a specific preferred embodiment as presently contemplated, it will be understood that the embodiment includes mechanical and functional equivalents of the elements described herein.