Abstract:
A simplified floating collar mounting arrangement for receiving a fuel nozzle swirler body of a gas turbine engine combustor is provided. The assembly comprises a floating collar mounted between a spaced-apart mounting flange and cap, and slidably trapped therebetween such that relative radial movement is permitted. The arrangement offers reduced part count and simplicity, and therefore improves reliability.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application relates to U.S. Patent Application Publication No. US 2006/0042269, filed Aug. 24, 2004, the specification of which is incorporated herein by reference. 
   TECHNICAL FIELD 
   The invention relates generally to gas turbine engine combustors and, more particularly, to a floating collar arrangement therefor. 
   BACKGROUND OF THE ART 
   Gas turbine combustors are typically provided with floating collars or seals to permit relative radial or lateral motion between the combustor and the fuel nozzle while minimizing leakage therebetween. The collar is subject to wear and heat, and is therefore cast/machined form a heat resistant material. As fuel nozzles, combustors and related components must be periodically removed for cleaning, inspection, repair and, occasionally replacement, the floating collar arrangement is provided in a manner which facilitates such removal, to thereby facilitate maintenance. Floating collar arrangements have become quite elaborate in the recent art, as designers continuously improve gas turbine efficiency. Such improvement, however, often comes at the expense of economical operation for the operator, as elaborate parts are typically more expensive to repair and replace. Accordingly, there is a need to provide a solution which addresses these and other limitations of the prior art, and in particular, there is a need to provided economical solutions to enable the emerging general aviation very small turbofan gas turbine market. 
   SUMMARY OF THE INVENTION 
   In one aspect, the present invention provides a gas turbine combustor floating collar assembly for receiving a fuel nozzle swirler body, the combustor having a nozzle opening defined in a dome thereof, the swirler body having an abutment shoulder extending therearound, the assembly comprising a mounting arrangement including a mounting flange spaced apart from the dome and circumscribing the opening, the flange fixedly bonded to the dome, and a cap spaced apart in an axial direction relative to the combustor from the mounting flange, the cap fixedly bonded to the mounting flange; and a floating collar slidably trapped between the mounting flange and the cap such that relative axial movement is substantially restrained but relative radial movement is permitted, the collar having a central aperture alignable with the dome opening and adapted for axial sliding engagement with the nozzle body, wherein the floating collar cannot be released from the mounting arrangement and the mounting arrangement cannot be released from the combustor without damaging at least one of the combustor, the mounting arrangement and the floating collar. 
   In another aspect, the present invention provides a method of providing a floating collar assembly on a gas turbine engine, the method comprising the steps of providing an assembly having a combustor with a nozzle opening defined in a dome thereof, a mounting arrangement including a sheet metal mounting flange, a sheet metal cap, and a sheet metal floating collar, the mounting flange, cap and floating collar each having a central aperture alignable with the dome opening, the floating collar aperture adapted for axial sliding engagement with a fuel nozzle air swirler body; fixedly bonding the mounting flange to the combustor dome in a spaced apart manner such that the flange central opening is generally aligned with dome opening; inserting the floating collar into the mounting flange; and fixedly bonding the cap to the mounting flange to thereby slidingly trap the floating collar between cap and the mounting flange. 
   Further details of these and other aspects of the present invention will be apparent from the detailed description and Figures included below. 

   
     DESCRIPTION OF THE DRAWINGS 
     Reference is now made to the accompanying Figures depicting aspects of the present invention, in which: 
       FIG. 1  is a schematic longitudinal sectional view of a turbofan gas turbine engine; 
       FIG. 2  is a partial sectional view of a combustor in accordance with an embodiment of the present invention; 
       FIG. 3  is an isometric view of a portion of  FIG. 2 ; and 
       FIG. 4  is an exploded isometric view of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     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  12  through which ambient air is propelled, a multistage compressor  14  for pressurizing the air, a combustor  16  in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section  18  for extracting energy from the combustion gases. 
     FIG. 2  shows an enlarged axial sectional view of a combustor  16  having a liner  20  and a dome  22  having an exterior side  24  and a central opening  26  for receiving a air swirler fuel nozzle (depicted in stippled lines in  FIG. 2 ) of the type generally described in U.S. Pat. Nos. 6,289,676 or 6,082,113, for example, and which are incorporated herein by reference. A mounting arrangement  28  is provided as will now be described. 
   An annular mounting flange  30  is fixedly bonded, preferably by a weld  32 , to the exterior side  24  of dome  22 , and includes an axially-disposed annular portion  30   a , a radially disposed annular flange portion  30   b , both defining a central aperture  34  therein. Central aperture  44  can be aligned with dome opening  26  when mounting flange  30  is mounted on the combustor. Mounting flange  30  may also include a plurality of legs  36  as will be described further below. 
   An annular cap  40  is provided and fixedly bonded, preferably by a weld  42 , to mounting flange  30 , preferably at legs  36 . Cap is provided in a spaced-apart manner relative to mounting flange  30 , as will be described further below. Cap  40  has a central aperture  44  which is aligned with dome opening  26  when mounted on combustor  16  and adapted to receive the fuel nozzle therein. 
   A floating collar  50  is provided having a axially-disposed nozzle collar portion  50   a , and a radially disposed annular flange portion  50   b , both surrounding a central aperture  54 , and a smooth transition  50   c  joins portions  50   a  and  50   b . Central aperture  54  and collar portion  50   a  are provided for axially slidingly engaging a circumferential shoulder of the fuel nozzle swirler body (stippled lines in  FIG. 2 ). Collar portion  50   a  preferably extends to, or inside, dome  22  though opening  26 . Flange portion  50   b  is trapped between opposed surfaces of mounting flange  30  and cap  40 , with mounting flange  30  and cap  40  being sufficiently spaced apart to permit radial (relative to the engine axis of  FIG. 1 ) sliding motion to occur between floating collar  50  and mounting flange  30 /cap  40 . An anti-rotation tang  56  depends from flange portion  50   b  and is likewise trapped between adjacent mounting flange legs  36 , to thereby limit the amount by which floating collar  50  may rotate relative to mounting flange  30 /cap  40 . 
   In use, the fuel nozzle air swirler (not shown) is positioned within central aperture  54  and delivers a fuel air mixture to combustor  16 . As forces acting upon the fuel nozzle and the combustor tend to cause relative movement therebetween, floating collar  50  is able to displace radially with the nozzle while maintaining sealing with respect to combustor through maintaining sliding engagement with mounting flange  30  and cap  40 . Welds  32  and  42  ensure that mounting flange  30  and cap  40  maintain their spaced-apart relation and thereby keep floating collar  50  trapped therebetween. 
   Referring to  FIG. 4 , mounting arrangement  28  is assembled through a process involving at least the following steps: welding mounting flange  30  to combustor dome  22  so that the flange central opening  36  is generally aligned with dome opening  26 ; inserting floating collar  50  into the mounting flange  30 , so that the collar portion  50   a  extends through central opening  36  and is generally aligned with dome opening  26 , and preferably also so that anti-rotation tang  56  is trapped between two closely adjacent legs  36 ; and welding cap  40  to mounting flange  30 , preferably at legs  36 , to slidingly trap the floating collar between cap and the mounting flange. The order of operations may be any suitable, and need not be chronologically as described. 
   Mounting arrangement  28  and floating collar  50  are preferably provided from sheet metal using a suitable fabrication process. An simplified example process is to provide a sheet of metal, cut a blank, and perform at least one bending operation to provide the floating collar. Referring again to  FIG. 2 , it is evident that a sheet metal collar  50  has a continuous transition  50   c  is provided as a result of a sheet metal forming operation, such a bending, and helps strengthen the collar  50 . Unlike prior art collars made by investment casting and/or machining processes (see U.S. Pat. Nos. 4,454,711, 4,322,945 and 6,497,105, for example), the present invention&#39;s use of sheet metal advantageously permits a very light weight and inexpensively-provided part, due to its simple geometry, and yet provides good performance and reliability. 
   Unlike the prior art, the mounting assembly of the present invention is geometrically simple, lightweight, easy to manufacture and east to assemble. Contrary to the prior art which teaches providing a high-cost device which facilitates replacement, the design and method of the present invention instead has relatively low initial cost, which assists in providing a lower-overall cost to the gas turbine engine, thereby facilitating the provision of an affordable general aviation turbofan engine, for example. As well, because the initial cost is lower, the cost of replacement may also be lowered. 
   The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, the present invention may be applied to any gas turbine engine, and is particularly suitable for airborne gas turbine applications. The means by which flange  30  is mounted to cap  40  may be different than that described. For example legs  36  may be replaced or supplemented with a continuous or discontinuous flange or lip, and/or may extend from flange  30 , cap  40  or both. The mode of anti-rotation may be any desirable. Though welding is preferred, brazing or other bonding methods may be used. Other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the equivalents accorded to the appended claims.