Patent Publication Number: US-2013227928-A1

Title: Fuel nozzle assembly for use in turbine engines and method of assembling same

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH &amp; DEVELOPMENT 
     This invention was made with Government support under contract number DE-FC26-05NT42643 awarded by the Department of Energy. The Government has certain rights in this invention. 
    
    
     BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein generally relates to turbine engines and, more particularly, to a fuel nozzle assembly for use in a turbine engine. 
     At least some known turbine engines are used in cogeneration facilities and power plants. Such engines may have high specific work and power per unit mass flow requirements. To increase the operating efficiency, at least some known turbine engines, such as gas turbine engines, operate with increased combustion temperatures. In at least some known gas turbine engines, engine efficiency increases as combustion gas temperatures increase. 
     However, operating with higher temperatures may also increase the generation of polluting emissions, such as oxides of nitrogen (NO x ). In an attempt to reduce the generation of such emissions, at least some known turbine engines include improved combustion system designs. For example, many combustion systems may use premixing technology that includes micro-mixers that facilitate mixing substances, such as diluents, gases, and/or air with fuel to generate a fuel mixture for combustion. 
     However, the benefits of such combustion systems may be limited. High H 2  concentrations created by such combustion systems may generate a high dynamics tone greater than 1 kHz that is audible as a screech. The high dynamics tone may increase the wear of the combustor and its associated components, and/or may shorten the useful life of the combustion system and, in extreme cases, may cause damage to the combustion system. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment a fuel nozzle for use with a turbine engine is provided. The fuel nozzle includes a housing coupled to a combustor liner defining a combustion chamber. The housing is at least partially positioned within an air plenum and comprises an endwall that at least partially defines the air plenum. The fuel nozzle includes a plurality of mixing tubes extending through the housing for channeling a fuel to the combustion chamber, a cooling fluid plenum at least partially defined within the housing by the housing endwall, and a plurality of apertures defined within said housing endwall for channeling a cooling fluid from the cooling fluid plenum to the air plenum. 
     In another embodiment, a combustor assembly for use with a turbine engine is provided. The combustor assembly includes a casing comprising an air plenum, a combustor liner positioned within the casing and defining a combustion chamber therein, and a plurality of fuel nozzles coupled to the combustor liner. Each fuel nozzle of the plurality of fuel nozzles includes a housing coupled to the combustor liner. The housing comprises an endwall that at least partially defines the combustion chamber, a plurality of mixing tubes extending through the housing for channeling a fuel to the combustion chamber, a cooling fluid plenum at least partially defined within the housing by the housing endwall, and a plurality of apertures defined within said housing endwall for channeling a cooling fluid from the cooling fluid plenum to the air plenum. 
     In yet another embodiment, a method of assembling a fuel nozzle for use with a turbine engine is provided. The method includes coupling a housing to a combustor liner that defines a combustion chamber. The housing is at least partially positioned within an air plenum and comprises an endwall that at least partially defines the air plenum. The method includes coupling a plurality of mixing tubes to the housing for channeling a fuel to the combustion chamber, forming a cooling fluid plenum at least partially within the housing, and forming a plurality of apertures for channeling a cooling fluid from the cooling fluid plenum to the air plenum. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of an exemplary turbine engine; 
         FIG. 2  is a sectional view of an exemplary fuel nozzle assembly that may be used with the turbine engine shown in  FIG. 1  and taken along area  2 ; 
         FIG. 3  is a cross-sectional view of a portion of an exemplary fuel nozzle assembly taken along line  3 - 3  (shown in  FIG. 2 ); 
         FIG. 4  is an enlarged cross-sectional view of a portion of an exemplary fuel nozzle taken along area  4  (shown in  FIG. 2 ); 
         FIG. 5  is an enlarged schematic view of a portion of an exemplary fuel nozzle that may be used with the fuel nozzle assembly shown in  FIG. 3  and taken along area  6  (shown in  FIG. 4 ); and 
         FIG. 6  is an enlarged schematic view of a portion of an alternative fuel nozzle that may be used with the fuel nozzle assembly shown in  FIG. 3  and taken along area  6  (shown in  FIG. 4 ). 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The exemplary apparatus, systems, and methods described herein overcome at least some known disadvantages associated with at least some known combustion systems of turbine engines that operate with higher temperatures. The embodiments described herein provide a fuel nozzle assembly that may be used with turbine engines to facilitate at least one of reducing a temperature of a component within the combustor, reducing NO x  produced by operation of the combustor, mitigating combustion dynamics produced by operation of the combustor, and improving operability or durability of components of the combustor. More specifically, the fuel nozzle assembly includes a plurality of fuel nozzles that each include a plurality of tubes and has both an upstream surface and a downstream surface. The upstream surface of at least one of the fuel nozzles has at least one opening. Cooling fluid is channeled through the fuel nozzle from a cooling fluid supply to at least one opening to mix with air and other fluids on the cold side of the fuel nozzle. More specifically, by channeling the cooling fluid to at least one opening, the peak temperature of combustion is reduced, NO x  is reduced, combustion dynamics are reduced, and operability and durability of the combustor are increased. 
     As used herein, the term “cooling fluid” refers to nitrogen, air, fuel, diluents, inert gases, or some combination thereof, and/or any other fluid that enables the fuel nozzle to function as described herein. 
       FIG. 1  is a schematic cross-sectional view of an exemplary turbine engine  100 . More specifically, turbine engine  100  is a gas turbine engine. While the exemplary embodiment includes a gas turbine engine, the present invention is not limited to any one particular engine, and one of ordinary skill in the art will appreciate that the current invention may be used in connection with other turbine engines. 
     Moreover, in the exemplary embodiment, turbine engine  100  includes an intake section  112 , a compressor section  114  coupled downstream from intake section  112 , a combustor section  116  coupled downstream from compressor section  114 , a turbine section  118  coupled downstream from combustor section  116 , and an exhaust section  120 . Turbine section  118  is coupled to compressor section  114  via a rotor shaft  122 . In the exemplary embodiment, combustor section  116  includes a plurality of combustor assemblies  124 . Combustor section  116  is coupled to compressor section  114  such that each combustor assembly  124  is positioned in flow communication with the compressor section  114 . A fuel nozzle assembly  126  is coupled within each combustor assembly  124 . Turbine section  118  is coupled to compressor section  114  and to a load  128  such as, but not limited to, an electrical generator and/or a mechanical drive application. In the exemplary embodiment, each compressor section  114  and turbine section  118  includes at least one rotor disk assembly  130  that is coupled to a rotor shaft  122  to form a rotor assembly  132 . A fuel supply system  138  is coupled to each fuel nozzle assembly  126  for channeling a flow of fuel to fuel nozzle assembly  126 . In addition, a cooling fluid supply system  140  is coupled to each fuel nozzle assembly  126  for channeling a flow of cooling fluid to each fuel nozzle assembly  126 . 
     During operation, intake section  112  channels air towards compressor section  114  wherein the air is compressed to a higher pressure and temperature prior to being discharged towards combustor section  116 . The compressed air is mixed with fuel and other fluids that are provided by each fuel nozzle assembly  126  and ignited to generate combustion gases that are channeled towards turbine section  118 . More specifically, each fuel nozzle assembly  126  injects fuel, such as natural gas and/or fuel oil, air, and/or diluents, such as nitrogen gas (N 2 ) in respective combustor assemblies  124 , and into the air flow. The fuel and air mixture is ignited to generate high temperature combustion gases that are channeled toward turbine section  118 . Turbine section  118  converts the thermal energy from the gas stream to mechanical rotational energy, as the combustion gases impart rotational energy to turbine section  118  and to rotor assembly  132 . By having each fuel nozzle assembly  126  inject the fuel with air and/or diluents in respective combustor assemblies  124 , the peak temperature, combustion dynamics and/or NOx may be reduced within each combustor assembly  124 . 
       FIG. 2  is a sectional view of an exemplary embodiment of fuel nozzle assembly  126  and taken along area  2  (shown in  FIG. 1 ).  FIG. 3  is a sectional view of a portion of fuel nozzle assembly  126  taken along line  3 - 3  in  FIG. 2 .  FIG. 4  is an enlarged cross-sectional view of a portion of fuel nozzle  236  taken along area  4  in  FIG. 2 . In the exemplary embodiment, combustor assembly  124  includes a casing  242  that defines a chamber  244  within the casing  242 . An end cover  246  is coupled to an outer portion  248  of casing  242  such that an air plenum  250  is defined within chamber  244 . Compressor section  114  (shown in  FIG. 1 ) is coupled in flow communication with chamber  244  to channel compressed air downstream from compressor section  114  to air plenum  250 . 
     In the exemplary embodiment, each combustor assembly  124  includes a combustor liner  252  that is positioned within chamber  244  and is coupled in flow communication with turbine section  118  (shown in  FIG. 1 ) through a transition piece (not shown) and with compressor section  114 . Combustor liner  252  includes a substantially cylindrically-shaped inner surface  254  that extends between an aft portion (not shown) and a forward portion  256 . Inner surface  254  defines annular combustion chamber  234  that extends axially along a centerline axis  258 , and extends between the aft portion and forward portion  256 . Combustor liner  252  is coupled to fuel nozzle assembly  126  such that fuel nozzle assembly  126  channels fuel and air into combustion chamber  234 . Combustion chamber  234  defines a combustion gas flow path  260  that extends from fuel nozzle assembly  126  to turbine section  118 . In the exemplary embodiment, fuel nozzle assembly  126  receives a flow of air from air plenum  250 , receives a flow of fuel from fuel supply system  138 , and channels a mixture of fuel/air into combustion chamber  234  for generating combustion gases. 
     Fuel nozzle assembly  126  includes a plurality of fuel nozzles  236  that are each coupled to combustor liner  252 , and at least partially positioned within air plenum  250 . In the exemplary embodiment, fuel nozzle assembly  126  includes a plurality of outer nozzles  262  that are circumferentially oriented about a center nozzle  264 . Center nozzle  264  is oriented along centerline axis  258 . 
     In the exemplary embodiment, an end plate  270  is coupled to forward portion  256  of combustor liner  252  such that end plate  270  at least partially defines combustion chamber  234 . End plate  270  includes a plurality of openings  272  that extend through end plate  270 , and are each sized and shaped to receive a fuel nozzle  236  therethrough. Each fuel nozzle  236  is positioned within a corresponding opening  272  such that fuel nozzle  236  is coupled in flow communication with combustion chamber  234 . Alternatively, fuel nozzles  236  may be coupled to combustor liner  252  such that no end plate is needed. 
     In the exemplary embodiment, each fuel nozzle  236  includes a housing  484  (shown in  FIG. 4 ). Housing  484  includes a sidewall  486  (shown in  FIG. 3 ) that extends between a forward endwall  488  and an opposite aft endwall  490 . Aft endwall  490  is oriented between forward endwall  488  and combustion chamber  234 , and includes an outer surface  492  that at least partially defines combustion chamber  234 . Sidewall  486  includes a radially outer surface  494  and a radially inner surface  496 . Radially inner surface  496  defines a substantially cylindrical cavity  498  that extends along a longitudinal axis  500  and between forward endwall  488  and aft endwall  490 . 
     An interior wall  502  is positioned within cavity  498  and extends inwardly from inner surface  496  such that a cooling fluid plenum  504  is defined between interior wall  502  and forward endwall  488 , and such that a fuel plenum  506  is defined between interior wall  502  and aft endwall  490 . In the exemplary embodiment, interior wall  502  is oriented substantially perpendicularly with respect to sidewall inner surface  496  such that fuel plenum  506  is oriented downstream of cooling fluid plenum  504  along longitudinal axis  500 . 
     In the exemplary embodiment, a plurality of cooling fluid conduits  508  extends from cooling fluid supply system  140  (shown in  FIG. 1 ) to fuel nozzle assembly  126 . Each cooling fluid conduit  508  is coupled in flow communication with corresponding fuel nozzle  236 . More specifically, cooling fluid conduit  508  is coupled to cooling fluid plenum  504  for channeling a flow of cooling fluid from cooling fluid supply system  140  to cooling fluid plenum  504 . Cooling fluid conduit  508  extends between end cover  246  and housing  484  and includes an inner surface  510  that defines a cooling fluid channel  512  within cooling fluid conduit  508  that is coupled to cooling fluid plenum  504 . Moreover, cooling fluid conduit  508  is coupled to forward endwall  488  and is oriented with respect to an opening  514  that extends through forward endwall  488  to couple cooling fluid channel  512  to cooling fluid plenum  504 . Each cooling fluid channel  512  is coupled to cooling fluid plenum  504  for channeling a flow of cooling fluid  515  from cooling fluid supply system  140  to cooling fluid plenum  504 . 
     A plurality of fuel conduits  516  extend between fuel supply system  138  (shown in  FIG. 1 ) and fuel nozzle assembly  126  for channeling a flow of fuel to fuel nozzle assembly  126 . In the exemplary embodiment, each fuel conduit  516  is coupled to a corresponding fuel nozzle  236  for channeling a flow of fuel  518  to fuel plenum  506 . Each fuel conduit  516  includes an inner surface  520  that defines a fuel channel  522  that is within fuel conduit  516  and coupled in flow communication with fuel plenum  506 . 
     Fuel conduit  516  is disposed within, and is substantially circumscribed by, cooling fluid conduit  508  and extends through cooling fluid plenum  504  to interior wall  502 . Fuel conduit  516  is oriented with respect to an opening  524  that extends through interior wall  502  to couple fuel channel  522  in flow communication with fuel plenum  506 . 
     In the exemplary embodiment, fuel nozzle  236  includes a plurality of mixing tubes  528  that are each coupled to housing  484 . Each mixing tube  528  extends through housing  484  to couple air plenum  250  to combustion chamber  234 . Mixing tubes  528  are oriented in a plurality of rows  530  (shown in  FIG. 3 ) that extend outwardly from a center portion  532  (shown in  FIG. 3 ) of fuel nozzle assembly  126  towards housing sidewall  486 . Each row  530  includes a plurality of mixing tubes  528  that are oriented circumferentially about nozzle center portion  532 . Each mixing tube  528  includes an outer surface  534  and a substantially cylindrical inner surface  536 , and extends between an inlet portion  538  and an outlet portion  540 . Mixing tube  528  includes a width  541  measured between inner surface  536  and outer surface  534 . Inner surface  536  defines a flow channel  542  that extends along a centerline axis  544  between inlet portion  538  and outlet portion  540 . Inlet portion  538  is sized and shaped to channel a flow of air, represented by arrow  546 , from air plenum  250  into flow channel  542  to facilitate mixing fuel and air within flow channel  542 . 
     Forward endwall  488  includes a plurality of inlet openings  548  that extend through forward endwall  488 . In addition, aft endwall  490  includes a plurality of outlet openings  550  that extend though aft endwall  490 . Each mixing tube inlet portion  538  is oriented adjacent to forward endwall  488  and extends through a corresponding inlet opening  548 . Moreover, outlet portion  540  is oriented adjacent to aft endwall  490  and extends through a corresponding outlet opening  550 . In addition, each mixing tube  528  extends through a plurality of openings  552  that extend through interior wall  502 . In the exemplary embodiment, each mixing tube  528  is oriented substantially parallel with respect to longitudinal axis  500 . Alternatively, at least one mixing tube  528  may be oriented obliquely with respect to longitudinal axis  500 . 
     In the exemplary embodiment, one or more mixing tubes  528  include at least one fuel aperture  554  that extends through mixing tube inner surface  536  to couple fuel plenum  506  to flow channel  542 . Fuel aperture  554  is configured to channel flow of fuel  518  from fuel plenum  506  to flow channel  542  to facilitate mixing fuel  518  with air  546  to form a fuel-air mixture, represented by arrow  558 , that is channeled to combustion chamber  234 . In the exemplary embodiment, fuel aperture  554  extends along a centerline axis  560  that is oriented substantially perpendicular to flow channel axis  544 . In another embodiment, fuel aperture  554  is oriented obliquely with respect to flow channel axis  544 . Alternatively, fuel aperture  554  may be oriented at any angle with respect to flow channel axis  544  that enables fuel nozzle  236  to function as described herein. 
       FIG. 5  is an enlarged schematic view of a portion of an exemplary fuel nozzle  236  shown in  FIG. 4  and taken along area  6 .  FIG. 6  is an enlarged schematic view of a portion of an alternative fuel nozzle. In the exemplary embodiment, one or more cooling fluid apertures  602  extend through forward endwall  488  for coupling cooling fluid plenum  504  in flow communication with air plenum  250 . Cooling fluid aperture  602  is configured to channel cooling fluid  515  from cooling fluid plenum  504  to air plenum  250 . Fuel nozzle  236  may have any number and/or arrangement of cooling fluid apertures  602  to enable fuel nozzle assembly  126  to function as described herein. 
     In the exemplary embodiment, cooling fluid aperture  602  has a radially inner surface  604  that defines a flow channel  608  that extends along a centerline axis  610 . Cooling fluid aperture  602 , and therefore centerline axis  610 , is substantially parallel to centerline axis  544 . Alternatively, at least one cooling fluid aperture  602 , and therefore centerline axis  610 , may be oriented obliquely with respect to centerline axis  544 . More particularly, the oblique angle may be between about 30 to 60 degrees. 
     During operation, fuel is channeled from fuel supply system  138  through fuel conduit  516  and supplied to fuel nozzle assembly  126 , wherein the fuel is mixed with at least air to form a combustible mixture. More specifically, fuel is channeled from fuel conduit  516  to at least one aperture  554  located on mixing tube  528 . Air and other fluids flow through mixing tube  528 , as shown by arrow  546 , and mix with fuel to form the combustible mixture. The combustible mixture is ignited after discharging from outlet opening  550  of fuel nozzle  236  to combustion chamber  234 . High concentrations of H 2  burning in combustion chamber  234  generate a high dynamics tone greater than 1 kHz. The high dynamics tone, in extreme cases, causes damage to combustor section  116  or other parts of turbine engine  100 . 
     To reduce the high dynamics tone and NO x , other fluids are channeled to combustion chamber  234  via fuel nozzle  236 . More specifically, in the exemplary embodiment, when fuel is supplied to nozzle  236 , cooling fluid is channeled through cooling fluid conduit  508  to fuel nozzle  236 . More specifically, cooling fluid is channeled from cooling fluid supply system  140  (shown in  FIG. 1 ) through cooling fluid channel  512  to cooling fluid plenum  504 . The cooling fluid is channeled through at least one aperture  602  and discharged into air plenum  250 . The cooling fluid is mixed with air and/or other fluids present in air plenum  250  before flowing through mixing tube  528 , as shown by arrows  546 , such that the cooling fluid facilitates the reduction of a temperature, e.g., a local peak, in combustion chamber  234 , the reduction of the high dynamics tone and the reduction of NO x . By reducing the peak temperature of combustion chamber  234 , the overall temperature of combustor assembly  124  (shown in  FIG. 1 ) is reduced. 
     As compared to known apparatus and systems that are used with turbine engines, the above-described fuel nozzle assembly may be used with turbine engines to facilitate reducing the peak temperature generated within a combustor. More specifically, the fuel nozzle assembly includes a plurality of fuel nozzles. Each of the plurality of fuel nozzles includes a plurality of mixing tubes for channeling air, fuel, and other fluids to the combustion chamber. A cooling fluid is channeled through apertures on the cold-side of at least one fuel nozzle for mixing with air and/or other fluids before being channeled through the plurality of tubes to the combustion chamber. By channeling the cooling fluid to at least one of the fuel nozzles, the peak temperature in the combustion chamber is reduced, NO x  is reduced, combustion dynamics are reduced, and operability and durability of the combustor are increased. 
     Exemplary embodiments of a fuel nozzle assembly and method of assembling same are described above in detail. The fuel nozzle assembly and method of assembling same are not limited to the specific embodiments described herein, but rather, components of the fuel nozzle assembly and/or steps of the assemblage of the assembly may be utilized independently and separately from other components and/or steps described herein. For example, any of the openings described herein may be used with any of the fuel nozzles described herein. Additionally, the fuel nozzle assembly may also be used in combination with other machines and methods, and is not limited to practice with only a turbine engine as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other systems. 
     Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.