Abstract:
A method of repairing a combustor dome with a swirler assembly having a first deflector component attached to a swirler having a first joint configuration includes: removing the first deflector component; machining a second joint configuration different from the first joint configuration in the swirler; providing a replacement deflector component having a shape complementary to the second joint configuration; and securing the replacement deflector component to the swirler

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates generally to combustors for gas turbine engines and more particularly to a method of repairing an annular dome of a combustor.  
         [0002]     In gas turbine engines, compressed air is mixed with fuel and burned within a combustor to produce high-temperature working gases, which are directed to one or more downstream turbines for work extraction. A known type of combustor includes an annular dome attached to annular inner and outer liners which define a combustion chamber therebetween. Fuel injection devices are attached to the combustor in flow communication with the dome and supply fuel to the combustion chamber. The dome includes a structural dome plate carrying a plurality of swirler assemblies. Each swirler assembly includes an air swirler, and a divergent deflector assembly which extends aft from the swirler to prevent hot combustion gases from impinging upon the dome plate. The deflector assembly is comprised of a cylindrical sleeve and a deflector plate, attached at a cylindrical interface.  
         [0003]     In some engines, the combustor dome experiences heavy “burning” (i.e. localized overheating) and oxidation of the sleeve and deflector plate. Prior art repair methods require either complete replacement of the dome with a newly manufactured dome, or repair of the dome by removal and replacement of the sleeve and deflector plate. Unfortunately, removal of the sleeve and deflector plate while preserving the geometric features of the swirler requires expensive and complex machining processes, such as wire electrodischarge machining (EDM).  
         [0004]     Accordingly, there is a need for a method of replacing a combustor deflector plate and or sleeve using simple machining processes.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     The above-mentioned need is met by the present invention, which according to one aspect provides a method of repairing a swirler assembly having a first deflector component attached to a swirler having a first joint configuration, including: removing the first deflector component; machining a second joint configuration different from the first joint configuration in the swirler; providing a replacement deflector component having a sleeve with a shape complementary to the second joint configuration; and securing the replacement deflector component to the swirler.  
         [0006]     According to another aspect of the invention, a method of repairing a combustor dome for a gas turbine engine includes: providing a combustor having: a swirler defining a first joint configuration for receiving a deflector component; and a first deflector component having: a sleeve with generally conical aft section; and a generally cylindrical forward section complementary to the first joint configuration, wherein the forward section is secured to the swirler; removing the first deflector component; machining a second joint configuration different from the first joint configuration into the swirler; providing a replacement deflector component having a shape complementary to the second joint configuration; and securing the replacement deflector component to the swirler. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:  
         [0008]      FIG. 1  is a cross-sectional view of a typical gas turbine engine annular combustor;  
         [0009]      FIG. 2  is an enlarged view of a swirler in the dome portion of  FIG. 1 ;  
         [0010]      FIG. 3  is a cross-sectional view of a portion of a swirler and sleeve portion of the deflector assembly in the dome showing an initial attachment joint;  
         [0011]      FIG. 4  is a view showing the swirler portion of  FIG. 3  machined in a different configuration for repair;  
         [0012]      FIG. 5  is a cross-sectional view of a replacement sleeve portion of the deflector assembly constructed and machined according to the present invention; and  
         [0013]      FIG. 6  is a cross-sectional view of a joined swirler and replacement sleeve portion of the deflector assembled according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,  FIG. 1  illustrates an exemplary gas turbine engine combustor  10 . The combustor  10  includes spaced-apart annular inner and outer liners  12  and  14 , respectively, which define generally a combustion chamber  16 . A dome assembly  18  comprising a dome plate  20  carrying a plurality of swirler assemblies  22  extends between the inner and outer liners  12  and  14 . Each swirler assembly  22  has a deflector assembly  23  attached thereto. A fuel injection device  25  is located forward of the dome assembly  18  and introduces fuel into the swirler assemblies in a manner to produce a combustion process. In the exemplary embodiment, the dome  18  is arranged in a single annular configuration. The present invention is equally applicable to other known configurations such as “double annular” and “triple annular” domes (not shown) which include multiple concentric rings of swirler and deflector assemblies.  
         [0015]      FIG. 2  illustrates one of the swirler assemblies  22  in more detail. It includes a primary swirler  24  and a secondary swirler  26  integrally formed as a unitary swirler body that is fixedly received in the dome plate  20 . The primary swirler  24  includes a first plurality of circumferentially spaced swirl vanes  28  disposed about a central venturi  30 , and the secondary swirler  26  includes a second plurality of circumferentially spaced swirl vanes  32  disposed coaxially about the venturi  30 . Incoming air passing through the first swirl vanes  28  is swirled into the venturi  30 . This swirling air interacts with fuel injected from a fuel injection device (not shown in  FIG. 2 ) so as to mix as it passes into the venturi  30 . The secondary swirl vanes  32  then act to present a flow of air swirling in the same or opposite direction that interacts with the fuel/air mixture so as to further atomize the mixture.  
         [0016]      FIG. 3  illustrates that the secondary swirler  26  has a radially-extending forward section  34  connected to a cylindrical axially-extending aft section  36 . Together they form a generally L-shaped cross section. The aft end of the aft section  36  has an inner ring  38  and an outer ring  40  which define a cylindrical swirler groove  42  therebetween (see  FIG. 3 ) to accept the deflector assembly  23 .  
         [0017]     The deflector assembly  23  is comprised of the sleeve  27  and deflector plate  29 . In some instances these may be a single integral part. The sleeve  27  of the deflector assembly  23  has a generally conical aft section  44  and a generally cylindrical forward section  46 . The forward cylindrical end  46  of the sleeve  27  is formed into an axially-extending tang  48  of reduced thickness which is received in the swirler groove  42 . In the illustrated example, the axial length of the tang  48  is selected so that an attachment slot  50  is present between the tang  48  and the base of the swirler groove  42 . This provides space to put alloy material for the purpose of bonding the two parts. During initial manufacture, the dome  18  including the swirler assemblies  22  and deflector assemblies  23  are put through a high temperature furnace cycle sufficient to cause the alloy material to melt and flow. As a result the swirler assemblies  22  and deflector assembly  23  are thus securely bonded together. By the original process, when replacement of the deflector assembly  23  or subfeatures are required, it may not be cost effective or desirable to machine and disassemble the deflector assemblies from the entire dome  18 . In the prior art, this leads to the replacement of the deflector assemblies  23  by using a process such as EDM to machine them away while maintaining the integrity of the swirler groove  42 .  
         [0018]     The dome  18  may be repaired in accordance with the present invention as follows. First, the dome  18  is separated from the rest of the combustor  10  to expose the dome plate  20 , individual swirler assemblies  22  and deflector assemblies  23 . Next, the original deflector assembly  23  is removed from the swirler assembly  22 . In contrast to prior art repair methods, there is no need to preserve the swirler groove  42 . This allows the use of simple machining methods. For example, the original deflector  23  may be cut away with an ordinary end-mill. Alternatively, the deflector assembly  23  could be removed in two steps by first separating the swirler  22  from the sleeve  27  with a mill or a fly-cutter, for example along line “L” in  FIG. 3 , and then milling away the remainder. By this method it is possible to retain a deflector plate  29  that is not damaged for future use.  
         [0019]     Once the original deflector assembly  23  is removed, a lap joint geometry is machined into the aft end of the aft section  36  of the secondary swirler  26 . As shown in  FIG. 4 , this is done by machining away the inner ring  38  to create a machined cylindrical surface  52  having an inner radius “R 1 ”. This can be accomplished with a conventional cutting tool. The machined diameter  52  may be formed simultaneously with the removal of the original deflector assembly  23  as described above. Depending on the exact configuration of the secondary swirler  26  and deflector assembly  23 , an alternate approach may be to remove the outer ring  40  instead of the inner ring  38 .  
         [0020]      FIG. 5  illustrates the sleeve portion of a replacement deflector assembly  123 . The replacement deflector assembly  123  is substantially similar in construction to the original deflector assembly  23  and includes a sleeve  127  with a generally conical aft section  144  and a generally cylindrical forward section  146 . The forward end of the forward section  146  lacks the annular tang  48  of the original deflector assembly  23  and instead is a substantially constant-thickness member, with an outer radius “R 2 ” substantially equal to, or slightly smaller than the inner radius RI of the machined cylindrical surface  52 .  
         [0021]     As with the original deflector assembly  23 , the replacement deflector sleeve  127  and deflector plate similar to deflector plate  29  (not shown) may be cast or otherwise formed from a suitable high-temperature alloy such as a Mar-M-509 cobalt-based alloy. Alternatively, the replacement deflector sleeve  127  or deflector plate may be constructed from different materials, preferably an alloy having enhanced oxidation resistant material properties. It is often the case that during the service life of a gas turbine engine component, improved alloys suitable for use with such components are developed. Traditionally, engine operators would have to replace existing dome assemblies with a new dome containing components fabricated from the improved alloy to realize the enhanced material properties. However, by fabricating the replacement deflector assembly  123  or sleeve  127  or deflector plate from the improved alloy, the repaired combustor  10  may obtain, in part, the enhanced material properties and resultant extended service life.  
         [0022]     A suitable braze alloy, is placed on the radiused surface R 2 . The replacement deflector sleeve  127  or deflector plate is then assembled and placed in the secondary swirler  26  so that it engages the swirler groove  42 , forming a lap joint  54 , as shown in  FIG. 6 . This pre-assembly sequence is then repeated for each deflector assembly  23  that is to be replaced. After all of the swirler assemblies  22  have been prepared, the dome  18  is placed in a furnace and heated at an appropriate temperature for a time sufficient to enable the attachment material to bond the deflector assembly  23  to the swirler assembly  22 . Once fully processed, the dome  18  is ready for reassembly into the combustor  10 .  
         [0023]     It has been found that the above-described repair method will be much more cost-effective than either complete replacement of the dome assembly  18  or prior art methods of deflector assembly replacement. Analysis has also shown that an acceptable joint in terms of strength and operational durability is created while requiring significantly less machining effort than the original joint.  
         [0024]     The foregoing has described a method for repairing a combustor dome. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention. Accordingly, the foregoing description of the preferred embodiment of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation, the invention being defined by the claims.