Patent Publication Number: US-9423134-B2

Title: Bundled tube fuel injector with a multi-configuration tube tip

Description:
FIELD OF THE INVENTION 
     The present invention generally involves a bundled tube fuel injector such as may be incorporated into a combustor of a gas turbine or other turbomachine. Specifically, the invention relates to a tube tip for pre-mix tubes of the bundled tube fuel injector. 
     BACKGROUND OF THE INVENTION 
     Gas turbines are widely used in industrial and power generation operations. A typical gas turbine may include a compressor section, a combustion section disposed downstream from the compressor section, and a turbine section disposed downstream from the combustion section. A working fluid such as ambient air flows into the compressor section where it is progressively compressed before flowing into the combustion section. The compressed working fluid is mixed with a fuel and burned within one or more combustors of the combustion section to generate combustion gases having a high temperature, pressure, and velocity. The combustion gases flow from the combustors and expand through the turbine section to produce thrust and/or to rotate a shaft, thus producing work. 
     The combustors may be annularly arranged between the compressor section and the turbine section. In a particular combustor design, the combustors include one or more axially extending bundled tube fuel injectors that extend downstream from an end cover. 
     The bundled tube fuel injector generally includes a plurality of pre-mix tubes arranged radially and circumferentially across the bundled tube fuel injector. The pre-mix tubes extend generally parallel to one another. An outer shroud extends circumferentially around the pre-mix tubes downstream from a fuel distribution module of the bundled tube fuel injector. An aft plate extends radially and circumferentially across a downstream end of the outer shroud adjacent to a combustion chamber or zone defined within the combustor. A cooling air or purge air plenum is at least partially defined within the outer shroud between the fuel distribution manifold and the aft plate. In a conventional bundled tube fuel injector, a downstream or end portion of each pre-mix tube extends through the aft plate such that an outlet of each tube is downstream from a hot side surface of the aft plate, thus providing for fluid communication into the combustion chamber or zone. 
     Each of the pre-mix tubes extends generally axially through the fuel distribution module and the cooling air plenum. The compressed working fluid is routed through inlets of each of the parallel pre-mix tubes upstream from the fuel distribution module. Fuel is supplied to the fuel plenum through the fluid conduit and the fuel is injected into the pre-mix tubes through one or more fuel ports defined within each of the pre-mix tubes. The fuel and compressed working fluid mix inside the pre-mix tubes before flowing out of the outlet which is defined at the downstream or end portion of each of the pre-mix tubes and into the combustion chamber or zone for combustion. 
     During operation of the combustor, the downstream or end portion of the pre-mix tubes is exposed to extreme temperatures due their proximity to the combustion chamber and/or the combustion flame. Over time, the downstream or end portion of the pre-mix tubes degrades due to the thermal stresses, thus requiring scheduled inspection and in some cases repair or refurbishment of the bundled tube fuel injectors. Materials that are suitable for high or extreme temperatures and that may enhance the life of the pre-mix tubes are relatively expensive. As a result it may be impractical and/or cost prohibitive to manufacture the pre-mix tubes entirely from these materials. Therefore, an improved bundled tube fuel injector would be useful. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     One embodiment of the present invention is a bundled tube fuel injector. The bundled tube fuel injector includes a fuel plenum that is defined within the bundled tube fuel injector and a plurality of pre-mix tubes that extend downstream from the fuel plenum substantially parallel to one another. Each pre-mix tube includes an end portion and a radially extending end surface. The bundled tube fuel injector further includes a tube tip that is fixedly connected to the end portion of a corresponding pre-mix tube. 
     Another embodiment of the present disclosure is a combustor having an outer casing, an end cover coupled to the outer casing and a bundled tube fuel injector coupled to the end cover and extending axially downstream from the end cover. The bundled tube fuel injector comprises a fuel plenum that is defined within the bundled tube fuel injector and a plurality of pre-mix tubes that extend downstream from the fuel plenum substantially parallel to one another. Each pre-mix tube includes an end portion and a radially extending end surface. The bundled tube fuel injector further includes a tube tip that is fixedly connected to the end portion of a corresponding pre-mix tube. In particular embodiments, the combustor may be coupled to a turbomachine such as a gas turbine. 
     Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which: 
         FIG. 1  provides a functional block diagram of an exemplary gas turbine that may incorporate various embodiments of the present invention; 
         FIG. 2  is a simplified cross-section side view of an exemplary combustor as may incorporate various embodiments of the present invention; 
         FIG. 3 , is a cross section perspective view of an exemplary bundled tube fuel injector according to one embodiment of the present invention; 
         FIG. 4 , is an enlarged cross sectional side view of a portion of the bundled tube fuel injector as shown in  FIG. 3  including a tube tip, according to various embodiments of the present invention; 
         FIG. 5  is an enlarged cross sectional view of an exemplary tube tip and a corresponding pre-mix tube as shown in  FIG. 4 , according to one embodiment of the present invention; 
         FIG. 6  is an enlarged side view of the exemplary tube tip shown in  FIG. 5 , fixedly connected to the pre-mix tube; 
         FIG. 7  is an enlarged cross sectional view of an exemplary tube tip and a corresponding pre-mix tube as shown in  FIG. 4 , according to one embodiment of the present invention; 
         FIG. 8  is an enlarged side view of the exemplary tube tip shown in  FIG. 7 , fixedly connected to the pre-mix tube; 
         FIG. 9 , is an enlarged cross sectional side view of a portion of the bundled tube fuel injector as shown in  FIG. 3  including a tube tip, according to various embodiments of the present invention; 
         FIG. 10  is an enlarged cross sectional view of an exemplary tube tip and a corresponding pre-mix tube as shown in  FIG. 9 , according to one embodiment of the present invention; 
         FIG. 11  is an enlarged side view of the exemplary tube tip shown in  FIG. 10 , fixedly connected to the pre-mix tube; 
         FIG. 12  is an enlarged cross sectional view of an exemplary tube tip and a corresponding pre-mix tube as shown in  FIG. 9 , according to one embodiment of the present invention; 
         FIG. 13  is an enlarged side view of the exemplary tube tip shown in  FIG. 12 , fixedly connected to the pre-mix tube; 
         FIG. 14 , is an enlarged cross sectional side view of a portion of the bundled tube fuel injector as shown in  FIG. 3  including a tube tip, according to various embodiments of the present invention; 
         FIG. 15  is an enlarged cross sectional view of an exemplary tube tip and a corresponding pre-mix tube as shown in  FIG. 14 , according to one embodiment of the present invention; 
         FIG. 16  is an enlarged side view of the exemplary tube tip shown in  FIG. 15 , fixedly connected to the pre-mix tube; 
         FIG. 17  is an enlarged cross sectional view of an exemplary tube tip and a corresponding pre-mix tube as shown in  FIG. 14 , according to one embodiment of the present invention; and 
         FIG. 18  is an enlarged side view of the exemplary tube tip shown in  FIG. 17 , fixedly connected to the pre-mix tube. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the terms “first”, “second”, and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. The term “radially” refers to the relative direction that is substantially perpendicular to an axial centerline of a particular component, and the term “axially” refers to the relative direction that is substantially parallel to an axial centerline of a particular component. 
     Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Although exemplary embodiments of the present invention will be described generally in the context of a bundled tube fuel injector incorporated into a combustor of a gas turbine for purposes of illustration, one of ordinary skill in the art will readily appreciate that embodiments of the present invention may be applied to any combustor incorporated into any turbomachine and are not limited to a gas turbine combustor unless specifically recited in the claims. 
     Referring now to the drawings, wherein identical numerals indicate the same elements throughout the figures,  FIG. 1  provides a functional block diagram of an exemplary gas turbine  10  that may incorporate various embodiments of the present invention. As shown, the gas turbine  10  generally includes an inlet section  12  that may include a series of filters, cooling coils, moisture separators, and/or other devices to purify and otherwise condition a working fluid (e.g., air)  14  entering the gas turbine  10 . The working fluid  14  flows to a compressor section where a compressor  16  progressively imparts kinetic energy to the working fluid  14  to produce a compressed working fluid  18 . 
     The compressed working fluid  18  is mixed with a fuel  20  from a fuel source  22  such as a fuel skid to form a combustible mixture within one or more combustors  24 . The combustible mixture is burned to produce combustion gases  26  having a high temperature, pressure and velocity. The combustion gases  26  flow through a turbine  28  of a turbine section to produce work. For example, the turbine  28  may be connected to a shaft  30  so that rotation of the turbine  28  drives the compressor  16  to produce the compressed working fluid  18 . Alternately or in addition, the shaft  30  may connect the turbine  28  to a generator  32  for producing electricity. Exhaust gases  34  from the turbine  28  flow through an exhaust section  36  that connects the turbine  28  to an exhaust stack  38  downstream from the turbine  28 . The exhaust section  36  may include, for example, a heat recovery steam generator (not shown) for cleaning and extracting additional heat from the exhaust gases  34  prior to release to the environment. 
       FIG. 2  provides a simplified cross section of an exemplary combustor  24  as may incorporate a bundled tube fuel injector  40  configured according to at least one embodiment of the present disclosure. As shown, the combustor  24  is at least partially surrounded by an outer casing  42 . The outer casing  42  at least partially forms a high pressure plenum  44  around the combustor  24 . The high pressure plenum  44  may be in fluid communication with the compressor  16  or other source for supplying the compressed working fluid  18  to the combustor  24 . In one configuration, an end cover  48  is coupled to the outer casing  42 . The end cover  48  may be in fluid communication with the fuel supply  22 . 
     The bundled tube fuel injector  40  extends downstream from the end cover  48 . The bundled tube fuel injector  40  may be fluidly connected to the end cover  48  so as to receive fuel from the fuel supply  22 . For example, a fluid conduit  52  may provide for fluid communication between the end cover  48  and/or the fuel supply  22  and the bundled tube fuel injector  40 . One end of an annular liner  54  such as a combustion liner and/or a transition duct surrounds a downstream end  56  of the bundled tube fuel injector  40  so as to at least partially define a combustion chamber  58  within the combustor  24 . The liner  54  at least partially defines a hot gas path  60  for directing the combustion gases  26  from the combustion chamber  58  through the combustor  24 . For example, the hot gas path  60  may be configured to route the combustion gases  26  towards the turbine  28  and/or the exhaust section. 
     In operation, the compressed working fluid  18  is routed towards the end cover  48  where it reverses direction and flows through one or more of the bundled tube fuel injectors  40 . The fuel  20  is provided to the bundled tube fuel injector  40  and the fuel  20  and the compressed working fluid  18  are premixed or combined within the bundled tube fuel injector  40  before being injected into a combustion chamber  58  for combustion. 
       FIG. 3  is a cross section perspective view of an exemplary bundled tube fuel injector  100  herein referred to as “fuel injector” as may be incorporated into the combustor  24  as described in  FIG. 2 , according to various embodiments of the present disclosure. As shown, the fuel injector  100  generally includes a fuel distribution module  102  that is in fluid communication with the fluid conduit  52 . In particular embodiments, the fuel distribution module  102  includes an upstream plate  104  that is axially separated from a downstream plate  106 . The upstream and downstream plates  104 ,  106  extend generally radially and circumferentially within the fuel injector  100 . An outer band  108  circumferentially surrounds and extends axially between the upstream and downstream plates  104 ,  106 . The outer band  108  may extend axially beyond either one or both of the upstream and downstream plates  104 ,  106 . A fuel plenum  110  may be at least partially defined between the upstream and downstream plates  104 ,  106  and the outer band  108 . The fluid conduit  52  provides for fluid communication between the fuel supply  22  ( FIG. 1 ) and the fuel plenum  110 . 
     In particular configurations, an aft plate  112  is disposed at a downstream or aft end  114  of the fuel injector  100 . The aft plate  112  extends radially outwardly and circumferentially across the aft end  114  with respect an axial centerline  116  of the fuel injector  100 . The aft plate  112  at least partially defines a plurality of tube tip passages  118  that extend generally axially through the aft plate  112 . 
     In particular embodiments, an impingement plate  120  is disposed upstream from the aft plate  112 . The impingement plate  120  may be welded, brazed or otherwise coupled to the aft plate  112 . The aft plate  112  and/or the impingement plate  120  may at least partially define a cartridge or fuel nozzle passage  122  that extends generally axially therethrough. A fluid cartridge or fuel nozzle  124  may be coupled to the aft plate  112  at the center nozzle passage  122 . An outer shroud  126  may extend generally axially between the fuel distribution module  102  and the aft plate  112 . The outer shroud  126  may be coupled to the aft plate  112  and/or the fuel distribution module  102  via welding, brazing, mechanical fasteners or by any suitable means for the operating environment of the fuel injector  100 . 
     As shown in  FIG. 3 , the fuel injector  100  includes a pre-mix tube bundle  128 . The pre-mix tube bundle  128  comprises a plurality of pre-mix tubes  130  that extend generally parallel to one another along or parallel to the axial centerline  116  of the fuel injector  100 . The pre-mix tubes  130  extend downstream from the fuel plenum  110  towards the aft plate  112  and/or the combustion chamber  58  ( FIG. 2 ). A portion of the pre-mix tubes  130  extends through the fuel plenum  110 . 
     The pre-mix tubes  130  may be formed from a single continuous tube or may be formed from two or more coaxially aligned tubes fixedly joined together. Although generally illustrated as cylindrical, the pre-mix tubes  130  may be any geometric shape, and the present invention is not limited to any particular cross-section unless specifically recited in the claims. In addition, the pre-mix tubes  130  may be grouped or arranged in circular, triangular, square, or other geometric shapes, and may be arranged in various numbers and geometries. 
     In one embodiment, each pre-mix tube  130  is generally aligned with a corresponding tube tip passage  118 . In one embodiment, the pre-mix tubes  130  are arranged in multiple rows  132 . Each row  132  may include one or more of the pre-mix tubes  130 . In one embodiment, each row  132  is radially spaced with respect to the axial centerline  116  from an adjacent row  132 . The pre-mix tubes  130  of at least some of the rows  132  may be arranged annularly around the axial centerline  116 . The pre-mix tubes  130  of each row  132  may be arranged generally circumferentially across the fuel injector  100  with respect to an axial centerline of the combustor  24  and/or the axial centerline  116  of the fuel injector  100 . 
     An exemplary pre-mix tube  130 , as shown in  FIG. 3 , generally includes an inlet  134  defined upstream from the fuel plenum  110  and/or the upstream plate  104 . The inlet  134  may be in fluid communication with the high pressure plenum  44  and/or the compressor  16 . A downstream or end portion  136  is defined downstream from the fuel plenum  110 . A radially extending surface  138  is defined between an inner and outer diameter of the pre-mix tube  130  at a distal end of the end portion  136 . One or more fuel ports  140  may provide for fluid communication between the fuel plenum  110  and a corresponding pre-mix passage  142  within the pre-mix tubes  130 . 
       FIG. 4  is an enlarged cross sectional side view of a portion of the fuel injector  100  as shown in  FIG. 3 , according to various embodiments of the present disclosure. In various embodiments, as shown in  FIG. 4 , a tube tip  200  is fixedly connected to the end portion  136  of a corresponding pre-mix tube  130 . In particular embodiments, the tube tip  200  may comprise high temperature alloys that are dissimilar to a material that forms the corresponding pre-mix tube. For example, the tube tip  200  may comprise of at least one of nickel, cobalt, chromium, molybdenum or stainless steel based alloys. In particular embodiments, the fuel injector  100  may include a plurality of tube tips  200  in one or more configurations, as described below, each coupled to a corresponding end portion  136  of a corresponding pre-mix tube  130 . 
     In one embodiment, as shown in  FIG. 4 , an exemplary tube tip  210  comprises a mating end  212 , an opposing outlet end  214  and a pre-mix portion  216  that extends therebetween. In one embodiment, the outlet end  214  extends axially through a corresponding tube tip passage  118  of the aft plate  112 . As detailed in  FIGS. 5 and 6 , the mating end  212  of the tube tip  210  defines a socket  218 . The socket  218  is configured to receive a portion of the end portion  136  of the corresponding pre-mix tube  130 . For example, the socket  218  generally has an inner diameter that is greater than an outer diameter of the end portion  136  of the pre-mix tube  130 . The socket  218  also extends axially across the end portion  136  with respect to an axial centerline of the pre-mix tube  130  and/or the tube tip  210 . The tube tip  210  may be fixedly connected to the pre-mix tube  130  via brazing, welding, adhesive cladding or by any means and/or process suitable for joining the two components. 
     In one embodiment, as shown in  FIG. 4 , the end portion  136  of a corresponding pre-mix tube  130  extends through a corresponding tube tip passage  118 . In this embodiment, as shown in  FIGS. 4, 6 and 7 , an exemplary tube tip  220  extends circumferentially around and axially along the end portion  136  of the pre-mix tube  130 , thereby forming a collar or sleeve around the end portion  136 . The tube tip  220  may be fixedly connected to the pre-mix tube  130  via brazing, welding, adhesive cladding or by any means or process suitable for joining the two components. The tube tip  220  may extend through the aft plate  112  and/or the impingement plate  120 . 
     In one embodiment, as illustrated in  FIGS. 6 and 7 , the tube tip  220  extends radially inwardly with respect to an axial centerline of the pre-mix tube  130  across the radially extending surface  138  of the pre-mix tube  130 , thereby thermally shielding the radially extending surface  138  of the pre-mix tube  130  from the combustion flame and/or the combustion gases  26 , thus enhancing thermal and/or mechanical performance of the pre-mix tube  130 . 
     In one embodiment, as shown in  FIGS. 9, 10 and 11 , the tube tip  220  includes a retention feature  222 . The retention feature  222  may comprise a collar  224  that extends radially outwardly from a main body  226  of the tube tip  220 . As shown in  FIG. 9 , the retention feature  222  may be disposed upstream from the aft plate  112 . For example, the retention feature  222  may be disposed adjacent to a cool or upstream side  228  of the aft plate  112 . In the alternative, the retention feature  222  may be disposed adjacent to an upstream side of the impingement plate  120 . The retention feature may prevent the tube tip  220  from flowing downstream in case the tube tip  220  prematurely liberates from the pre-mix tube  130  during operation of the combustor  24 , thereby potentially preventing damage to downstream components such as the liner  54  and/or the turbine  28 . 
     In one embodiment, as shown in  FIG. 9  and as detailed in  FIGS. 12 and 13 , an exemplary tube tip  230  comprises a radially extending mating surface  232  and a step  234  defined along the radially extending mating surface, wherein the downstream end  136  of the pre-mix tube  130  is seated adjacent to the step  234 . The tube tip  230  may be fixedly connected to the pre-mix tube  130  via brazing, welding, adhesive cladding or by any means and/or process suitable for joining the two components. The tube tip  230  may extend through the aft plate  112  and/or the impingement plate  120 . 
     In one embodiment, as shown in  FIGS. 14, 15 and 16 , an exemplary tube tip  240  comprises a radially extending mating surface  242  that forms a butt joint  244  with the radially extending end surface  138  of the pre-mix tube. The tube tip comprises a radially extending mating surface that forms a butt joint with the radially extending end surface of the pre-mix tube. The tube tip  240  may be fixedly connected to the pre-mix tube  130  via brazing, welding, adhesive cladding or by any means and/or process suitable for joining the two components. The tube tip may extend through the aft plate  112  and/or the impingement plate  120 . 
     In one embodiment, as shown in  FIGS. 14, 17 and 18 , an exemplary tube tip  250  comprises a radially extending mating surface  252  that forms a joint  254  with the radially extending end surface  138  of the pre-mix tube  130 . A coupling sleeve  256  circumferentially surrounds the joint  254 . The coupling sleeve  256  may be fixedly connected to the pre-mix tube  130  via brazing, welding, adhesive cladding or by any means and/or process suitable for joining the two components. The tube tip may extend through the aft plate  112  and/or the impingement plate  120 . The coupling sleeve  256  provides structural support the connection between the pre-mix tube  130  and the tube tip. 
     The various embodiments provided herein, provide various technical advantages over existing bundled tube fuel injectors. For example, the tube tips  200  may reduce costs currently associated with the repair and/or replacement of pre-mix tubes. In addition, the tube tips  200  provide a two part tubing system that allows for design flexibility in material selection which may enhance mechanical and thermal performance of the bundled tube fuel injector  100 , thus increasing part life. Another technical benefit of the various tube tip geometries may include improvements in disassembly, repair and assembly time of the bundled tube fuel injector  100 . 
     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 include 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.