Abstract:
Disclosed is a combustor including a baffle plate having at least one through baffle hole and at least one fuel nozzle extending through the at least one baffle hole. A plurality of injection holes extend through the at least one fuel nozzle and are configured to meter a flow of diluent into the combustor. Further disclosed is a method for providing diluent to a combustor including providing a plurality of openings located at at least one fuel nozzle extending through a through hole in a baffle plate. The diluent is flowed through the plurality of openings toward at least one airflow opening in the at least one fuel nozzle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject invention relates generally to combustors. More particularly, the subject invention relates to the introduction of diluent flow into a combustor via a fuel nozzle. 
         [0002]    Combustors typically include one or more fuel nozzles that introduce a fuel or a mixture of fuel and air to a combustion chamber where it is ignited. In some combustors, the fuel nozzles extend through holes disposed in a baffle plate of the combustor. In these combustors, it is often advantageous to introduce a volume of diluent, often nitrogen or steam, to the combustor to reduce NOx emissions and/or augment output of the combustor. The diluent is urged from a chamber through a gap between the baffle plate and each fuel nozzle, and then flows along a periphery of the fuel nozzle where a portion of the diluent enters the fuel nozzle via holes in the air collar of the fuel nozzle. The gaps between the baffle plate and the fuel nozzles, however, vary due to assembly tolerance stack-ups between the baffle plate and the fuel nozzles. The gap variation results in variation in diluent flow around each nozzle and throughout the combustor assembly. Further, an axial distance between the gap and the air collar holes in the fuel nozzle allow diluent to reach the combustion reaction zone without passing through the fuel nozzle and mixing directly with the fuel and air. Both of these effects reduce diluent efficiency and therefore a greater volume of diluent is required to achieve an equivalent amount of diluent flow into the fuel nozzle. The excess diluent that flows toward the combustion reaction zone without passing through the fuel nozzle leads to operability problems in the combustor such as dynamics and blow out. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    According to one aspect of the invention, a combustor includes a baffle plate having at least one through baffle hole and at least one fuel nozzle extending through the at least one baffle hole. A plurality of injection holes extend through the at least one fuel nozzle and are configured to meter a flow of diluent into the combustor. 
         [0004]    According to another aspect of the invention, a method for providing diluent to a combustor includes providing a plurality of openings located at at least one fuel nozzle extending through a through hole in a baffle plate. The diluent is flowed through the plurality of openings toward at least one airflow opening in the at least one fuel nozzle. 
         [0005]    These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0007]      FIG. 1  is a cross-sectional view of an embodiment of a combustor; 
           [0008]      FIG. 2  is an end view of an embodiment of a baffle plate assembly of a combustor; 
           [0009]      FIG. 3  is a partial cross-sectional view of an embodiment of the baffle plate assembly of  FIG. 2 ; 
           [0010]      FIG. 4  is a partial perspective view of a cover ring that supplies diluent to a plenum defined by the baffle plate assembly of  FIG. 2 ; 
           [0011]      FIG. 5  is a cross-sectional view of another embodiment of the baffle plate assembly of  FIG. 2 ; 
           [0012]      FIG. 6  is a perspective view of the baffle plate assembly of  FIG. 5 ; 
           [0013]      FIG. 7  is a cross-sectional view of yet another embodiment of the baffle plate assembly of  FIG. 2 ; 
           [0014]      FIG. 8  is an end view of an embodiment of injection openings in the fuel nozzle shown in the baffle plate assembly of  FIG. 7 ; 
           [0015]      FIG. 9  is a cross-sectional view of still another embodiment of the baffle plate assembly of  FIG. 2 ; and 
           [0016]      FIG. 10  is a cross-sectional view of one variation of the embodiment of baffle plate assembly of  FIG. 9 . 
       
    
    
       [0017]    The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Shown in  FIG. 1  is a combustor  10 . The combustor  10  includes a baffle plate  12  having six baffle holes  14 , through which six fuel nozzles  16  extend, for example, one fuel nozzle  16  extending through each baffle hole  14 , as best shown in  FIG. 2 . While six fuel nozzles  16  are shown in  FIG. 1 , it is to be appreciated that other quantities of fuel nozzles  16 , for example, one or four fuel nozzles  16 , may be utilized. As shown in  FIG. 3 , the baffle plate  12  and a cover ring  18  define a plenum  20  into which a diluent flow  22  is guided via an array of orifices  24  (best shown in  FIG. 4 ) in the cover ring  18 . In some embodiments, the diluent flow  22  may comprise steam, or other diluents such as nitrogen. 
         [0019]    At each fuel nozzle  16 , as shown in  FIG. 3 , a shroud  26  is disposed at the baffle hole  14  between the baffle plate  12  and the fuel nozzle  16 . In the embodiment of  FIG. 3 , the shroud  26  includes an attachment flange  28  disposed at, for example, an upstream face  30  of the baffle plate  12 . In some embodiments, the attachment flange  28  is secured to the upstream face  30  by welding, but other means may be use such as mechanical fasteners, brazing, or adhesives. Further, it is to be appreciated that the shroud  26  may be secured to other portions of the baffle plate  12 , for example a downstream face  32 . The shroud  26  and an outer surface  34  of the fuel nozzle  16  define a flow channel  36  therebetween. Two piston rings  38  are disposed at the shroud  26  to seal between the shroud  26  and the fuel nozzle  16 . As shown in  FIG. 3 , each piston ring  38  is disposed in a piston ring slot  40  at a tip end  42  of the shroud  26 . It will be appreciated that while two piston rings  38  and two piston ring slots  40  are shown in  FIG. 3 , other quantities of piston rings  38  per piston ring slot  40  and quantities of piston ring slots  40 , for example two or three piston rings  38  per piston ring slot  40  or one or three piston ring slots  40  may be utilized. A plurality of injection holes  44  extend, in the embodiment of  FIG. 3 , through the fuel nozzle  16  from the flow channel  36  to a nozzle end  46 , and may be directed at an angle to a nozzle central axis  48 . In operation, the diluent flow  22  is guided from the plenum  20 , along the flow channel  36  and through the plurality of injection holes  44 . Upon entering the nozzle end  46 , the diluent flow  22  is, in some embodiments, mixed with an airflow  50  entering a nozzle air collar  52  via a plurality of airflow openings  54 . Sealing between the shroud  26  and the outer surface  34  via the two piston rings  38 , and injecting the diluent flow  22  via the plurality of injection holes  44  increases a proportion of the diluent flow  22  that is mixed with the airflow  50  and enters a head end (not shown) of the combustor  10  via the fuel nozzle  16 . 
         [0020]    In another embodiment, as shown in  FIG. 5 , the plurality of injection holes  44  extend through the fuel nozzle  16  substantially parallel to the central axis  48 . The plurality of injection holes  44  extends from the plenum  20  through, for example, a raised injection surface  56  which is integral to the fuel nozzle  16 . As shown in  FIG. 6 , an exit  58  of each injection hole  44  substantially aligns with an airflow opening  54  in a circumferential direction. Referring again to  FIG. 5 , the diluent flow  22  passes flows from the plenum  20 , through the plurality of injection holes  44  to an exterior  60  of the baffle plate  12  at the head end of the combustor  10 , near the plurality of airflow openings  54 . At least a portion of the diluent flow  22  enters the plurality of airflow openings  54  where it is mixed with the airflow  50 . Configuring the plurality of airflow openings  44  as shown in  FIG. 5  is advantageous since the exit  58  of each injection hole  44  aligns circumferentially with an airflow opening  54 , thereby increasing an amount of diluent flow  22  that enters the plurality of airflow openings  54 , mixes with the airflow  50  and enters the combustor via the fuel nozzle  16 . Further, as shown in  FIG. 5 , sealing between the fuel nozzle  16  and the baffle plate  12  may be achieved via piston rings  38  disposed therebetween, without utilizing the shroud  26  of  FIG. 3 . The piston rings  38  of  FIG. 5  are disposed in corresponding piston ring slots  62  in the fuel nozzle  16  and are compressed by the baffle plate  12 . The piston rings, however, may also be disposed in piston ring slots  62  in the baffle plate  12  and compressed by the fuel nozzle  16 . 
         [0021]    Referring now to  FIG. 7 , in some embodiments, the plurality of injection holes  44  comprises a plurality of injection channels  64 , with a plurality of ribs  66  (shown in  FIG. 8 ) therebetween, in the fuel nozzle  16 . A sheath  68 , which may be substantially annular, is secured to the ribs  66  thus defining, together with the plurality of injection channels  64 , the plurality of injection holes  44 . The sheath  68  may be secured by brazing, or other means such as welding, adhesives, or mechanical fasteners. In this embodiment, the piston rings  34  seal between the baffle plate  12  and the sheath  68  at an outer surface  70  of the sheath  68 . 
         [0022]    As shown in  FIG. 9 , in some embodiments the shroud  26  is secured to the fuel nozzle  16  by, for example, welding or brazing, and the piston rings  38  are utilized to seal between the shroud  26  and the baffle plate  12 . The shroud  26  and outer surface  34  define the flow channel  36 . In this embodiment, the plurality of injection holes  44  is disposed at an attachment leg  72  of the shroud  26 . As shown in  FIG. 8 , the shroud  26  is disposed such that the attachment leg  72  is located at the plurality of airflow openings  54 . In other embodiments, such as the embodiment shown in  FIG. 9 , the shroud  26  is reversed, so that the diluent flow  22  flows through the plurality of injection holes  44  before flowing through the flow channel  36 . 
         [0023]    Guiding the diluent flow  22  through the plurality of injection openings  44  allows injection of the diluent flow  22  nearby the air flow openings  54  to increase efficiency of the diluent flow  22 . Further, the diluent flow  22  is metered via the injection openings  44  and consistent throughout the combustor  10 . Thus, a volume of diluent flow  22  required is reduced thereby reducing operability issues such has dynamics and lean blow out. 
         [0024]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.