Patent Publication Number: US-2018051883-A1

Title: Pre-mixing based fuel nozzle for use in a combustion turbine engine

Description:
STATEMENT REGARDING FEDERALLY SPONSORED DEVELOPMENT 
     Development for this invention was supported in part by Contract No. DE-FC26-05NT42644, awarded by the United States Department of Energy. Accordingly, the United States Government may have certain rights in this invention. 
    
    
     BACKGROUND 
     1. Field 
     Disclosed embodiments are generally related to a fuel nozzle for use in a combustion turbine engine, such as a gas turbine engine and, more particularly, to a pre-mixing type of fuel nozzle that in one non-limiting application may be used in a distributed combustion system (DCS) injection system. 
     2. Description of the Related Art 
     In gas turbine engines, fuel is delivered from a fuel source to a combustion section where the fuel is mixed with air and ignited to generate hot combustion products defining working gases. The working gases are directed to a turbine section. The combustion section may comprise one or more stages, each stage supplying fuel to be ignited. See U.S. Pat. Nos. 8,281,594 and 8,752,386 in connection with fuel nozzles involving pre-mixing of air and fuel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view that may be helpful for visualizing an upstream end of one non-limiting embodiment of a fuel nozzle embodying aspects of the invention that may be used in a combustor of a combustion turbine engine. 
         FIG. 2  is a top view of the upstream end of the fuel nozzle shown in  FIG. 1 . 
         FIG. 3  is a bottom view of a downstream end of the fuel nozzle shown in  FIG. 1 . 
         FIG. 4  is a cross-sectional view illustrating a non-limiting schematic representation of respective pre-mixing conduits and air flow conduits constructed in the body of the fuel nozzle. 
         FIG. 5  is a cross-sectional view illustrating a non-limiting schematic representation of fuel flow in a fuel-directing structure constructed in the body of the fuel nozzle. 
         FIG. 6  is a top view illustrating a non-limiting schematic representation of fuel-injecting locations in a given pre-mixing conduit. 
         FIG. 7  is a simplified schematic of one non-limiting embodiment of a combustion turbine engine, such as a gas turbine engine, that can benefit from disclosed embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The inventors of the present invention have recognized certain issues that can arise in the context of certain prior art fuel nozzles involving pre-mixing of air and fuel, also referred in the art as micro-mixing. These prior art fuel nozzles generally involve a large number of point injection arrays having a relatively small diameter, and the fabrication of such injection arrays may involve costly fabrication techniques. In view of such a recognition, the present inventors propose an improved fuel nozzle that can benefit from more economical fabrication techniques while providing appropriate levels of NO x  emissions and enabling practically a flashback-free operation, even on applications involving a relatively high-content of hydrogen fuel. 
     In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that embodiments of the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well-understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation. 
     Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art depending on the needs of a given application. 
     The terms “comprising”, “including”, “having”, and the like, as used in the present application, are intended to be synonymous unless otherwise indicated. Lastly, as used herein, the phrases “configured to” or “arranged to” embrace the concept that the feature preceding the phrases “configured to” or “arranged to” is intentionally and specifically designed or made to act or function in a specific way and should not be construed to mean that the feature just has a capability or suitability to act or function in the specified way, unless so indicated. 
       FIG. 1  is an isometric view of one non-limiting embodiment of a fuel nozzle  10  embodying aspects of the invention that in one non-limiting application may be used in a combustor of a combustion turbine engine, such as a gas turbine engine. Fuel nozzle  10  includes a body  12  having an inlet end  14  and an outlet end  16  and defines a central axis  18  that extends between inlet end  14  and outlet end  16  along an axial direction of the fuel nozzle. 
     As may be appreciated in  FIG. 1 , an array of pre-mixing conduits  20  extends between inlet end  14  and outlet end  16  of body  12 . The array of pre-mixing conduits  20  is circumferentially disposed about central axis  18 . Each pre-mixing conduit  20  is fluidly coupled to receive air at a respective inlet. 
     In one non-limiting embodiment, fuel nozzle  10  further includes an array of air flow conduits  22  disposed radially inwardly relative to the array of pre-mixing conduits  20 . In one non-limiting embodiment, fuel nozzle  10  may include means to aerodynamically reduce flow recirculation (flow separation) in the array of pre-mixing conduits  20 . It will be appreciated that the reduction of flow recirculation need not be limited to within the array of pre-mixing conduits  20 , since zones beyond outlet end  16  can also benefit from such flow recirculation reduction. As may be appreciated in  FIG. 4 , in one non-limiting embodiment, the means to aerodynamically reduce the flow recirculation in a respective pre-mixing conduit  20  may comprise an inter-conduit passageway  24  arranged to provide fluid communication between the respective pre-mixing conduit  20  and a corresponding air flow conduit  22 . It will be appreciated that the geometry of pre-mixing conduits  20  may be optionally configured to reduce flow recirculation in combination or in lieu of inter-conduit passageways  24 . 
     As may be appreciated in  FIG. 5 , fuel nozzle  10  further includes a fuel-directing structure  26  that in one-non-limiting embodiment includes a plurality of non-swirl elements  28 . Each non-swirl element includes a radially-extending passageway to direct fuel flow along a radial direction (schematically represented by arrows  30 ). Each non-swirl element  28  includes at least one orifice  32  arranged to inject the fuel that flows along the radial direction into a respective air/fuel pre-mixing conduit. Without limitation, orifices  32  may be located in regions of relatively high axial flow velocity, thus increasing the static pressure drop across orifices  32 . See  FIG. 6  that illustrates a non-limiting example of fuel-injecting locations (schematically represented by arrows  34 ) in a given pre-mixing conduit  20 . Fuel-directing structure  26  further includes a central passageway  36  ( FIG. 5 ) arranged to direct fuel flow along the axial direction (schematically represented by arrows  38 ) towards a central outlet  39 . 
     In one non-limiting embodiment, the array of pre-mixing conduits  20  each comprises at least a respective pre-mixing conduit segment (schematically represented by line  40  ( FIG. 4 )) having a cross-sectional area that increases as the respective pre-mixing conduit segment extends from a location between inlet end  14  and outlet end  16  towards a respective outlet  41  of the respective pre-mixing conduit. This may be effective so that flow velocity is increased without substantially increasing the overall pressure drop. In one non-limiting embodiment, pre-mixing conduit segment  40  includes at least one surface  42  tilted radially inwardly relative to central axis  18  as the segment extends towards the respective outlet  41  of the respective pre-mixing conduit  20 . 
     In one non-limiting embodiment, the array of air flow conduits  22  each comprises at least a respective air flow conduit segment (schematically represented by line  44  ( FIG. 4 ) having a cross-sectional area that decreases as the respective air flow conduit segment  44  extends from a respective inlet  45  of the respective air flow conduit  22  towards a location between inlet end  14  and outlet end  16 . In one non-limiting embodiment, the array of air flow conduits  22  each comprises an outlet  46  arranged radially inwardly relative to central axis  18 . In one non-limiting embodiment, central outlet  39  of central passageway  36  in combination with the respective outlets  46  of the array of air flow conduits  22  forms a jet-assisted mixing stage. It will be appreciated that the respective starting/end points and/or respective geometries of the conduit segments schematically represented by lines  40  and  44  should be construed in a non-limiting sense since other starting/end points and/or geometries may be arranged depending on the needs of a given application. 
       FIG. 7  is a simplified schematic of one non-limiting embodiment of a combustion turbine engine  50 , such as gas turbine engine, that can benefit from disclosed embodiments of the present invention. Combustion turbine engine  50  may comprise a compressor  52 , a combustor  54 , a combustion chamber  56 , and a turbine  58 . During operation, compressor  52  takes in ambient air and provides compressed air to a diffuser  60 , which passes the compressed air to a plenum  62  through which the compressed air passes to combustor  54 , which mixes the compressed air with fuel, and provides combusted, hot working gas via a transition  64  to turbine  58 , which can drive power-generating equipment (not shown) to generate electricity. A shaft  66  is shown connecting turbine  58  to drive compressor  52 . Disclosed embodiments of a fuel nozzle embodying aspects of the present invention may be incorporated in combustor  54  of the combustion turbine engine to achieve superior pre-mixing of fuel and air. 
     In operation and without limitation, disclosed embodiments are expected to provide a cost-effective fuel nozzle including arrays of fluid flow conduits that produce a substantially homogenous mixture of fuel and air at the outlet end of the nozzle and thus effective to produce appropriate pre-mixing of fuel and air conducive to ultra-low levels of NO x  emissions. Additionally, disclosed embodiments need not involve swirler elements, and thus flashback resistance is substantially high, even for fuel blends comprising a high hydrogen content (e.g., at least 50% hydrogen content by volume). 
     Without limitation, practical embodiments of the disclosed the nozzle may comprise fluid flow conduits having a minimum diameter in a range from about 0.75 mm to about 1 mm and thus capable of benefiting from relatively low-cost manufacturing technologies, such as, without limitation, three-dimensional (3D) printing, direct metal laser sintering (DLMS), etc., in lieu of presently costlier manufacturing technologies. 
     While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.