Abstract:
The present invention discloses a means for restricting a flow of fuel to a fuel nozzle assembly for a gas turbine combustor such that the fuel nozzle assembly can be manufactured to accommodate a variety of engine configurations and flow conditions. Multiple embodiments of the present invention are disclosed with each embodiment generally directed towards a nozzle located generally along the centerline of a two-stage combustor.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates generally to a premix fuel nozzle for use gas turbine combustor and more specifically to a device that meters the fuel flow to the premix fuel nozzle.  
       BACKGROUND OF THE INVENTION  
       [0002]     The U.S. Government has enacted requirements for lowering pollution emissions from gas turbine combustion engines, especially nitrogen oxide (NOx) and carbon monoxide (CO). These emissions are of particular concern for land based gas turbine engines that are used to generate electricity since these types of engines usually operate continuously and therefore emit steady amounts of NOx and CO. A variety of measures have been taken to reduce NOx and CO emissions including the use of catalysts, burning cleaner fuels such as natural gas, and improving combustion system efficiency. One of the more significant enhancements to land based gas turbine combustion technology has been the use of multiple combustor stages to lower emissions.  
         [0003]     One particular combustor of this configuration, which is shown in  FIG. 1 , includes two combustion chambers located adjacent to one another and in fluid communication, separated by a region of reduced diameter. In order to establish and support combustion in the second combustion chamber, a centrally located fuel nozzle assembly directs a dedicated supply of fuel and air to the second combustion chamber.  
         [0004]     It has been determined that due to the emissions requirements of the region in which the engine is located as well as other variables, engines of the same design that are intended to perform similarly actually vary significantly. As a result, combustion components such as fuel nozzles must be specifically tailored to a specific engine, in order to meet the engine performance requirements, which thereby prevents such components from being easily exchanged amongst other similar parts. Specifically, fuel and air injector holes must be specifically sized such that they can account for external variables such as geographic location of the engine, elevation, temperature, and humidity.  
         [0005]     What is needed is a fuel nozzle assembly that accounts for the aforementioned external variables and provides a fuel nozzle structure that can be easily adjusted for use in a variety of gas turbine engines.  
       SUMMARY AND OBJECTS OF THE INVENTION  
       [0006]     The present invention provides a fuel nozzle assembly having a means for restricting a flow of fuel to the fuel nozzle such that the flow rates can be customized after the fuel nozzle has been manufactured. This fuel flow restriction technique can be applied to a variety of fuel nozzle designs, with each nozzle configuration comprising at least an elongated housing having a first end and a second end, at least one first injector extending radially outward from the elongated housing, an end plate fixed proximate the second end of the elongated housing, and a base fixed proximate the first end of the elongated housing for receiving a fuel to be provided to the fuel nozzle.  
         [0007]     It is an object of the present invention to provide a fuel nozzle assembly wherein the fuel flow rate through the fuel nozzle assembly is determined after the fuel nozzle assembly has been manufactured.  
         [0008]     It is another object of the present invention to provide a means by which the fuel nozzle manufacturing process time is reduced.  
         [0009]     In accordance with these and other objects, which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]      FIG. 1  is a cross section view of a gas turbine combustor in which the present invention preferably operates.  
         [0011]      FIG. 2  is a cross section view of a fuel nozzle assembly in accordance with the preferred embodiment of the present invention.  
         [0012]      FIG. 3  is a cross section view of a fuel nozzle assembly in accordance with a first alternate embodiment of the present invention.  
         [0013]      FIG. 4  is a cross section view of a fuel nozzle assembly in accordance with a second alternate embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     The present invention will now be described in detail with reference to the accompanying drawings.  FIG. 1  discloses a generic cross section of a two-stage combustor  5 , with combustor  5  having a first combustion chamber  6 , and a second combustion chamber  7 , separated by a venturi  8 . A plurality of primary fuel nozzles  9  are located about combustor centerline A-A and inject a fuel into first combustion chamber  6 . The present invention, which is shown in multiple embodiments in  FIG. 2-4  pertains to an improvement to the fuel nozzle located generally along the combustor centerline A-A.  
         [0015]     Referring to  FIG. 2 , a fuel nozzle assembly  10  for a gas turbine combustor is shown in cross section. Fuel nozzle assembly  10  comprises an elongated housing  11  having a first end  12  and a second end  13  in spaced relation and a first passage  14  located proximate first end  12 . Extending radially outward from elongated housing  111  is at least one first injector  15  such that at least one first injector  15  is in fluid communication with first passage  14 . At least one first injector  15  also includes a plurality of first holes  16  that preferably inject fuel from injector  15  into a surrounding stream of air. The size, quantity, and spacing of first holes  16  depend on the desired fuel spray pattern into the surrounding air stream. First injector  15  can comprise different configurations depending on the fuel injection requirements and the desired mixing characteristics. For example, at least one first injector  15  can comprise a plurality of pegs, a generally annular ring extending circumferentially about elongated housing  11 , or a plurality of axially extending fins, as shown in  FIG. 2 . Fixed to elongated housing  11  proximate second end  13  is an end plate  17  having a plurality of second holes  18 . Located opposite end plate  17  and fixed to elongated housing  11 , proximate first end  12 , is a base  19  having a first inlet  20  in fluid communication with elongated housing first passage  14  and at least one first injector  15 . First inlet  20  further comprises a means for restricting a flow of fuel  21  to elongated housing first passage  14 . It is preferred that means for restricting a flow of fuel  21  to elongated housing  11  comprises a plate  22  fixed to first inlet  20  with plate  22  having at least one third hole  23 .  
         [0016]     In the preferred embodiment of the present invention, a fuel such as natural gas enters fuel nozzle assembly  10  through first inlet  20  and is restricted to the desired flow level by at least one third hole  23  in plate  22 . The fuel then passes through first passage  14  of elongated housing  11  to at least one first injector  15  and into the surrounding air stream through plurality of first holes  16 . A stream of air enters fuel nozzle assembly  10  through air holes  24  and passes through second holes  18  to cool end plate  17 . The use of a means for restricting a fuel flow  21  allows for fuel nozzle assembly  10  to be fabricated entirely before knowing what type of engine, and associated flow level, will be required. At least one third hole  23  is sized as required to restrict the fuel flow through first inlet  20  such that the proper amount of fuel is injected at the optimum pressure and flow rate through plurality of first holes  16  to properly mix with the surrounding air stream.  
         [0017]     Referring now to  FIG. 3 , a first alternate embodiment of the present invention is shown in cross section. Fuel nozzle assembly  30  comprises an elongated housing  31  having a first end  32  and a second end  33  in spaced relation and a first passage  34  located proximate first end  32  and a second passage  35  located radially outward of first passage  34 . Extending radially outward from elongated housing  31  is at least one first injector  36  such that at least one first injector  36  is in fluid communication with first passage  34 . At least one first injector  36  also includes a plurality of first holes  37  that preferably inject fuel from first injector  36  into a surrounding stream of air. First injector  36  can comprise different configurations depending on the fuel injection requirements and the desired mixing characteristics. For example, at least one first injector  36  can comprise a plurality of pegs, a generally annular ring extending circumferentially about elongated housing  31 , or a plurality of axially extending fins, as shown in  FIG. 3 . Located along elongated housing  31  and in fluid communication with second passage  35  is at least one second injector  38  having a plurality of fourth holes  39 . The size, quantity, and spacing of first holes  37  and fourth holes  39  depend on the desired spray pattern into the surrounding air stream. Fixed to elongated housing  31  proximate second end  33  is an end plate  40  having a plurality of second holes  41 . Located opposite end plate  40  and fixed to elongated housing  31 , proximate first end  32 , is a base  42  having a first inlet  43  in fluid communication with elongated housing first passage  34  and at least one first injector  36 . Base  42  further comprises a second inlet  44  in fluid communication with elongated housing second passage  35  and at least one second injector  38 . First inlet  43  further comprises a means for restricting a flow of fuel  45  to elongated housing first passage  34 . It is preferred that means for restricting a flow of fuel  45  to elongated housing  31  comprises a plate  46  fixed to first inlet  43  with plate  46  having at least one third hole  47 .  
         [0018]     In the first alternate embodiment of the present invention, a fuel such as natural gas enters fuel nozzle assembly  30  through first inlet  43  and is restricted to the desired flow level by at least one third hole  47  in plate  46 . The fuel then passes through first passage  34  of elongated housing  31  to at least one first injector  36  and into the surrounding air stream through plurality of first holes  37 . A stream of air passes through a third passage  48  of fuel nozzle assembly  30  and through second holes  41  to cool end plate  40 . In the primary operating mode of fuel nozzle assembly  30 , air also passes through second passage  35  and is injected into the surrounding air stream through second injector  38 . However, fuel may pass through second passage  35  and second injector  38 , if required, instead of air, depending on the operating mode of the combustor. The use of a means for restricting a fuel flow  45  allows for fuel nozzle assembly  30  to be fabricated entirely before knowing what type of engine, and associated flow level, will be required. At least one third hole  47  is sized as required to restrict the fuel flow through first inlet  43  such that the proper amount of fuel is injected at the optimum pressure and flow rate through plurality of first holes  37  to properly mix with the surrounding air stream.  
         [0019]     Referring now to  FIG. 4 , a second alternate embodiment of the present invention is shown in cross section. A fuel nozzle assembly  50  comprises an elongated housing  51  having a first end  52  and a second end  53  in spaced relation and a first passage  54  located proximate first end  52  and a second passage  55  located radially outward of first passage  34 . A third passage  56  is also located within elongated housing  51 , but proximate second end  53  and is in fluid communication with first passage  54 . Extending radially outward from elongated housing  51  is at least one first injector  57  such that at least one first injector  57  is in fluid communication with first passage  54 . At least one first injector  57  also includes a plurality of first holes  58  that preferably inject fuel from first injector  57  into a surrounding stream of air. First injector  57  can comprise different configuration depending on the fuel injection requirements and the desired mixing characteristics. For example, at least one first injector  57  can comprise a plurality of pegs, a plurality of axially extending fins, or a generally annular ring extending circumferentially about elongated housing  51 , as shown in  FIG. 4 . Fixed to elongated housing  51  proximate second end  53  is an end plate  59  having a plurality of second holes  60  that are in fluid communication with third passage  56 . Located proximate end plate  59  is a second injector device  61  that is in fluid communication with second passage  55  and has a plurality of fourth holes  62 . The size, quantity, and spacing of first holes  58 , second holes  60 , and fourth holes  61 , depend on the desired spray pattern into the surrounding air stream. Located opposite end plate  59  and fixed to elongated housing  51 , proximate first end  52 , is a base  63  having a first inlet  64  in fluid communication with elongated housing first passage  54  and at least one first injector  57 . Base  63  further comprises a second inlet  65  in fluid communication with elongated housing second passage  55  and at least one second injector  61 . First inlet  64  further comprises a means for restricting a flow of fuel  66  to elongated housing first passage  54 . It is preferred that means for restricting a flow of fuel  66  to first passage  54  comprises a plate  67  fixed to first inlet  66  with plate  67  having at least one third hole  68 .  
         [0020]     In the second alternate embodiment of the present invention, a fuel such as natural gas enters fuel nozzle assembly  50  through first inlet  64  and is restricted to the desired flow level by at least one third hole  68  in plate  67 . The fuel then passes through first passage  54  of elongated housing  51  to at least one first injector  57  and into the surrounding air stream through plurality of first holes  58 . The fuel that does not pass through first injector  57 , passes through pilot injector  69  and into third passage  56  where it premixes with air from air channels  70 . This premixture then passes through plurality of second holes  60  in end plate  59  and into a combustion chamber. In the primary operating mode of fuel nozzle assembly  50 , air also passes through second passage  55  and is injected into the surrounding air stream through second injector  61 . However, fuel may pass through second passage  55  and second injector  61 , if required, instead of air, depending on the operating mode of the combustor. The use of a means for restricting a fuel flow  66  allows for fuel nozzle assembly  50  to be fabricated entirely before knowing what type of engine, and associated flow level, will be required. At least one third hole  68  is sized as required to restrict the fuel flow through first inlet  64  such that the proper amount of fuel is injected at the optimum pressure and flow rate through plurality of first holes  58  to properly mix with the surrounding air stream and through plurality of second holes  60  to support the pilot flame established by fuel nozzle assembly  50 .  
         [0021]     While the invention has been described in what is known as presently the preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment but, on the contrary, is intended to cover various modifications and equivalent arrangements within the scope of the following claims.