Patent Publication Number: US-2020292168-A1

Title: Stackable air swirlers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of U.S. patent application Ser. No. 16/248,137 filed Jan. 15, 2019, now issued as U.S. Pat. No. 10,557,630 which is incorporated by reference herein in its entirety. 
     BACKGROUND 
       1 . Technological Field 
     The present disclosure relates to nozzles and injectors, and more particularly to swirlers for nozzle and injectors such as used in fuel injection for gas turbine engines. 
     2. Description of Related Art 
     Air swirlers, such as for use as inner air swirlers in fuel injectors and nozzles, are traditionally difficult to make. Advanced engine designs have high requirements for performance including low emissions. This often translates into complex swirler designs. Using conventional machining the geometry, e.g., aerodynamic vane geometry, is intricate and therefore costly and time consuming. If turning slots are used, milling out the slots is time consuming and costly. Additive manufacturing can accommodate a variety of geometries, but is also slow and expensive due to the fact that traditional additive manufacturing machines do not have a large enough build plate to economically produce a large number of swirlers. 
     The conventional techniques have been considered satisfactory for their intended purpose. However, there is an ever present need for improved swirlers and processes of making swirlers. This disclosure may address at least one of these needs. 
     SUMMARY 
     A swirler includes an inner body defining a swirl axis. A plurality of swirl vanes extend outward from the inner body. The swirl vanes define respective swirl slots therebetween for imparting swirl on a fluid passing through the swirl slots. 
     The inner body can follow a first cone angle that diverges in a downstream direction along the swirl axis. The swirl vanes can define a frustoconical volume that follows a second cone angle that converges in the downstream direction. The swirl slots and swirl vanes can be oriented tangential to the swirl axis. An outer ring can be connected to the swirl vanes and can provide an outward boundary to the swirl slots. The inner body can have a constant wall thickness. The inner body can define a plurality of cooling holes therethrough inboard of the swirl slots. 
     A method of making swirlers includes additively manufacturing a vertical stack of swirlers as described above. Additively manufacturing the vertical stack can include building an external ring and an inner point inside the external ring and additively manufacturing the vertical stack in a vertical build direction from the external ring and inner point. The inner body of a lower most swirler in the vertical stack can originate from the inner point. The method can include additively manufacturing a central support rod aligned with the swirl axis of the swirlers. The central support rod can support between adjacent swirlers in the stack so that the inner bodies of swirlers in the stack can be built up, each starting from the central support rod and diverging therefrom in the vertical build direction. The central support rod can include frangible features adjacent each swirler connected thereto and further comprising breaking the frangible features to separate the swirlers in the stack from one another. Breaking the frangible features can include twisting the swirlers relative to one another. The method can include separating the swirlers from one another by machining away the central support rod. An external tube outboard of the swirl vanes can be built up from the external ring to support the build from outside. The method can include machining the external tube away to separate the swirlers from one another. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG. 1  is a cross-sectional side elevation view of an exemplary embodiment of a swirler constructed in accordance with the present disclosure, showing the swirler as an inner air swirler in a nozzle with an outer air cap and a fuel circuit between the inner swirler and outer air cap; 
         FIG. 2  is a cross-sectional side-elevation view of a stack of swirlers like the swirler of  FIG. 1 , showing the stack after additive manufacturing but before separation of the individual swirlers from the stack; 
         FIG. 3  is a partially cut away perspective view of an additive manufacture build of swirlers like the swirler of  FIG. 1 , showing a build plate with a plurality of stacks like that of  FIG. 2  build thereon; 
         FIG. 4  is a cross-sectional side elevation view of a portion of the stack of  FIG. 2 , showing the frangible features of the central support rod; and 
         FIG. 5  is a cross-sectional side elevation view of the swirler of  FIG. 1 , with a central bore therethrough. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of a swirler in accordance with the disclosure is shown in  FIG. 1  and is designated generally by reference character  100 . Other embodiments of swirlers in accordance with the disclosure, or aspects thereof, are provided in  FIGS. 2-5 , as will be described. The systems and methods described herein can be used to facilitate manufacture of swirlers, such as for use as inner air swirlers in fuel injectors and nozzles. 
     The swirler  100  is seated as an inner air swirler in the inner air passage  12  of a nozzle  10  that defines a fuel passage  14  outboard of the inner air passage  12  and an outer air passage  16  with an outer air cap  18  outboard of the fuel passage  14 . Fuel issued from the fuel passage  14  is sheared between swirling air from the outer air swirler  18  and from the inner air swirler  100  to atomize the fuel spray indicated in  FIG. 1  by stippling for combustion, e.g., in a combustor of a gas turbine engine. Gaseous fuel can be used in addition to or in lieu of liquid fuel. The swirler  100  includes an inner body  102  defining a swirl axis A. A plurality of swirl vanes  104  extend outward from the inner body  102 , i.e. away from the swirl axis A. The swirl vanes  104  define respective swirl slots  106  therebetween for imparting swirl on a fluid, e.g., air, passing through the swirl slots  106  from upstream of the swirler  100 , i.e. the left side of the swirler  100  in  FIG. 1 , to downstream of the swirler  100 , i.e. on the right side of the swirler  100  in  FIG. 1 . 
     The inner body  102  is a conical body that follows a first cone angle  0  which diverges in a downstream direction along the swirl axis A, i.e. the conical body  102  gets further from the swirl axis A the further to the right it is along the swirl axis A in  FIG. 1 . The swirl vanes  104  define a frustoconical volume, e.g. indicated by the dotted area in  FIG. 1 , that follows a second cone angle a that converges in the downstream direction, i.e. the swirl vanes  104  get closer to the swirl axis A the further to the right they are in  FIG. 1 . Those skilled in the art will readily appreciate that while the inner body and swirl vanes follow conical geometries, it is not necessary for them to be strictly conical, e.g., they can follow any suitable curve. The swirl slots  106  and swirl vanes  104  are oriented tangential to the swirl axis A, in other words, the swirl slots  106  and swirl vanes  104  are not aligned along radii of axis A, but are offset from the radii of axis A as in a radial type swirler. An outer ring  108  is connected to the swirl vanes  104  and provides an outward boundary to the swirl slots  106 . The inner body  102  has a constant wall thickness T, and a plurality of cooling holes  110  therethrough inboard of the swirl slots  106 . 
     With reference now to  FIG. 2 , a method of making swirlers such as swirler  100  described above includes additively manufacturing a vertical, nested stack  112  of swirlers  100 . Additively manufacturing the vertical stack includes building an external ring  114  and an inner point  116  inside the external ring  114  and additively manufacturing the vertical stack in a vertical build direction D from the external ring  114  and inner point  116 . The external ring  114  and inner point  116  can be formed on a build plate  118 , e.g. of a selective laser sintering machine. The inner body  102  of a lower most swirler in the vertical stack  112  originates from the inner point  116 . The angle of the inner body  102  is conducive to being built up from this central point  116  in additive manufacturing machines. The method includes additively manufacturing a central support rod  120  aligned with the swirl axis A of the swirlers  100 . The central support rod  120  supports between adjacent swirlers  100  in the stack  112  so that the inner bodies  102  of swirlers  100  in the stack  112  can each be built up from a central point, with all the swirlers but the lower most each starting from the central support rod  120  and diverging therefrom in the vertical build direction D. 
     As shown in  FIG. 4 , the central support rod  120  includes frangible features  122 ,  124  adjacent each swirler  100  connected thereto. Each frangible feature  122  is just below the respective inner body  102  and is a frustoconical indentation in the cylindrical body of the central support rod  120 . Each frangible feature  124  is a similar frustoconical indentation just above the respective inner body  102 . The connection  124  between the central support rod  120  and the inner body  102  provides support and allows some heat transfer and mechanical support for a proper build. As shown in  FIG. 2 , an external tube  126  outboard of the swirl vanes  104  and outer rings  108  of the swirlers is built up from the external ring  114  to support the build from outside. 
     There is a respective ledge  128  protruding inward from the external tube  126  for supporting the build of each of the outer rings  108 . The frustoconical angle a of the swirl vanes described above with reference to  FIG. 1  is conducive to building up in additive manufacturing machines from the ledges  128 . 
     As shown in  FIG. 3 , several stacks  112  of swirlers  100  can be fit on a single build plate  118 . In this example, there are eight swirlers  100  in each of nine stacks for a total of seventy-two swirlers  100  that can be produced in a single additive manufacture build. Those skilled in the art will readily appreciate that any suitable number of swirlers in each stack, and any suitable number of stacks can be included on a build plate without departing from the scope of this disclosure. 
     After the build, e.g., the build on build plate  118  in  FIG. 3 , is complete, each stack  112  can be removed from the build plate  118 . The external tube  126 , labeled in  FIG. 2 , can be machined away from the stack  112  using any suitable process such as turning down on a lathe, e.g., to the final braze diameter, to begin separating the swirlers  100  from one another. The frangible features  122 ,  124  (labeled in  FIG. 4 ) can then be broken to finish separating the swirlers  100  in the stack  112  from one another. Breaking the frangible features  122 ,  124  can include twisting the swirlers relative to one another about the swirl axis A. Any remnant features of the central support rod  120  can be machined away from the swirler  100  using conventional techniques. Having the support structure  132  (labeled in  FIG. 4 ) between the frangible feature  122  and the inner body  102  protects the inner body  102 , e.g., from being damaged during the additive manufacturing process. It is also contemplated that in addition to or in lieu of using the frangible features  122 ,  124 , the swirlers  100  can be separated from one another by machining away the central support rod  120 , e.g., by drilling it down the swirl axis A or using electrical discharge machining (EDM), resulting in swirlers  100  with a central aperture  130  through the inner body  102  thereof. This central aperture  130  can be kept as a cooling bore, or can be plugged, e.g. by welding or brazing. 
     Systems and methods as disclosed herein provide swirlers that can economically be produced using additive manufacturing, while providing design flexibility needed for intricate features such as required in modern engines, e.g. for stringent emissions requirements. Relative to the number of swirlers that can be produced as disclosed herein, there is little support clean up required after a build. The conical geometries disclosed herein provide for nearly self-supporting build structures and allow nesting within one another for compact and efficient manufacturing. The methods and systems of the present disclosure, as described above and shown in the drawings, provide for swirlers with superior properties including ease of manufacture. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.