Patent Publication Number: US-2013232977-A1

Title: Fuel nozzle and a combustor for a gas turbine

Description:
FIELD OF THE INVENTION 
     The present invention generally involves a fuel nozzle and a combustor for a gas turbine. 
     BACKGROUND OF THE INVENTION 
     Gas turbines generally include a combustor with one or more fuel nozzles positioned about an end cover in various configurations. For example, some combustors may include a six fuel nozzle configuration which includes a center fuel nozzle surrounded by five outer fuel nozzles. In particular combustor designs, the fuel nozzle(s) extend downstream from the end cover and at least partially through one or more annular passage(s) of a cap assembly. Typically, the annular passage(s) includes an annular impingement sleeve disposed concentrically within the annular passage and/or a floating collar coupled to the impingement sleeve and/or the cap assembly. During assembly of the combustor, the fuel nozzle(s) are generally positioned so that a radial gap exists between the fuel nozzle and the floating collar. 
     In operation, a fuel and/or a working fluid flow through the fuel nozzle(s) and into the floating collar before exiting the cap assembly for combustion in a combustion zone within the combustor. However, during operation the floating collar may shift radially and/or axially due to combustor dynamics, thermal growth and/or compressor discharge pressures within the combustor, thereby contacting the fuel nozzle(s) and potentially reducing the mechanical life of the fuel nozzle(s) and/or the cap assembly. 
     Improved floating collar designs, however, may result in increased manufacturing, maintenance, and repair costs. For example, improved floating collar designs typically incorporate costly wear resistant materials. However, these materials do not prevent the collar from contacting the fuel nozzle. Therefore, an improved fuel nozzle design that eliminates the floating collar from the cap assembly 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 fuel nozzle for a gas turbine. The fuel nozzle includes an annular passage configured to flow a fuel and includes a first end axially separated from a second end. A disk concentric with the annular passage is disposed at the second end and extends radially outward from the second end. A plurality of passages extend through the disk from an upstream surface of the disk to a downstream surface of the disk and are configured to impart swirl to a fluid flowing through the passages. A shroud circumferentially surrounds the disk and includes an upstream end axially separated from a downstream end, wherein the shroud is coupled to the disk. 
     Another embodiment is a fuel nozzle for a gas turbine that includes an annular passage configured to flow a fuel and includes a first end axially separated from a diverging second end. A disk concentric with the annular passage is disposed at the diverging second end and extends radially outward from the diverging second end. A plurality of passages extends through the disk from an upstream surface of the disk to a downstream surface of the disk. A shroud, including an upstream end axially separated from a downstream end, circumferentially surrounds and extends axially downstream from the disk and is coupled to the disk. The fuel nozzle further includes a spring at least partially surrounding the shroud. 
     Embodiments of the present invention may also include a combustor. The combustor generally includes an end cover. An annular passage extends from the end cover and is configured to flow a fuel. The annular passage includes a first end axially separated from a diverging second end. A disk concentric with the annular passage is disposed at the diverging second end and extends radially outward from the diverging second end. A plurality of passages extend through the disk from an upstream surface of the disk to a downstream surface of the disk. The passages are configured to impart swirl to a fluid flowing through the passages. A shroud at least partially circumferentially surrounds the disk and extends axially downstream from the disk. The combustor further includes a spring at least partially surrounding the shroud. 
     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  is a schematic view of a gas turbine engine; 
         FIG. 2  is an enlarged cross section view of a simplified combustor according to one embodiment of the present invention; 
         FIG. 3  is an enlarged perspective cut-away view of a fuel nozzle as shown in  FIG. 2 ; 
         FIG. 4 . is an enlarged perspective cut-away view of a cross section of the combustor as shown in  FIG. 2 ; and 
         FIG. 5  is an enlarged axial cross section view of a portion of the combustor as shown in  FIG. 2 . 
     
    
    
     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. 
     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. 
     Various embodiments of the present invention provide a combustor and a fuel nozzle for a gas turbine. The combustor generally includes an end cover, a casing, a fuel nozzle and a cap assembly. In particular embodiments, the fuel nozzle may include an annular passage configured to connect to the end cover and to flow a fuel and/or a diluent. The fuel nozzle may further include a disk disposed at one end of the annular passage. In particular embodiments, a plurality of passages may extend from an upstream surface of the disk through a downstream surface of the disk and may be configured to impart swirl to the fuel and/or a working fluid passing through the passages. The fuel nozzle may further include a shroud generally surrounding and extending downstream form the disk. In certain embodiments, the fuel nozzle may also include a spring and an annular plate at least partially surrounding the shroud. The cap assembly may include an annular passage and an annular impingement sleeve disposed within the annular passage and configured to receive the fuel nozzle. In this manner, the various embodiments within the scope of the present invention may increase the mechanical life of the fuel nozzle and the cap assembly without compromising cooling flow within the combustor, reduce manufacturing costs of the combustor and provide a retrofit option for existing gas turbines. Although exemplary embodiments of the present invention will be described generally in the context of a combustor incorporated into 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 and are not limited to a gas turbine combustor unless specifically recited in the claims. 
       FIG. 1  provides a schematic view of a gas turbine  10 . As shown, the gas turbine  10  may include a compressor  12 , a combustor  14  in fluid communication with the compressor  12  and a turbine  16  downstream and in fluid communication with the combustor  14 . Although a single combustor  14  is shown, the gas turbine  10  may include a plurality of combustors  14  in fluid communication with the turbine  16 . In operation, a working fluid, such as air, flows through the compressor  12  to provide a compressed working fluid to the combustor  14 . The compressed working fluid is mixed with a fuel and ignited within the combustor  14 , thereby creating a rapidly expanding hot gas. The hot gas flows from the combustor  14  to the turbine  16 . As the hot gas flows through the turbine  16 , kinetic energy from the hot gas is transferred to a plurality of turbine buckets (not shown) attached to a turbine shaft  18  causing the turbine shaft  18  to rotate and produce mechanical work. The mechanical work produced may drive the compressor  12  or other external loads, such as a generator (not shown) to produce electricity. 
       FIG. 2  provides an enlarged cross section view of a simplified combustor according to one embodiment of the present invention.  FIG. 3  is an enlarged perspective cut-away view of a fuel nozzle as shown in  FIG. 2 ,  FIG. 4  is an enlarged perspective cut-away view of a cross section of the combustor as shown in  FIG. 2  and  FIG. 5  is an enlarged axial cross section view of a portion of the combustor as shown in  FIG. 2 . As shown in  FIG. 2 , a casing  20  generally surrounds the combustor  14  to contain a working fluid, such as compressed air, flowing to the combustor  14 . The casing  20  may include an end cover  22  disposed at one end. The end cover  22  may be configured to provide a fuel and/or a working fluid to one or more fuel nozzle(s)  24  extending generally downstream from the end cover  22 . The combustor  14  may further include a cap assembly  26  extending radially within the casing  20 . A combustion liner  28  may at least partially surround and extend generally downstream from the cap assembly  26 . 
     As shown in  FIG. 3 , the fuel nozzle(s)  24  generally include an annular passage  30 , a disk  32  concentric with the annular passage  30 , a shroud  34  surrounding the disk  32  and a spring  36  surrounding the shroud  34 . The annular passage  30  includes a first end  38  axially separated from a second end  40 . The annular passage  30  may be configured to connect to the end cover  22  and to provide fluid communication between the end cover  22  and the combustor  14 . The annular passage  30  may be configured to flow at least one of a liquid fuel, a gaseous fuel and a working fluid. In particular embodiments, the annular passage  30  may diverge at the second end  40 . In this manner, the fuel or working fluid flowing through the annular passage  30  may be accelerated as it flows from the first end  38  to the second end  40  of the fuel nozzle(s)  24 . A plurality of ports  42  may extend radially and/or axially through the annular passage  30 , thus providing a flow path for the fuel and/or working fluid to flow from the annular passage  30  and into the combustor  14 . The annular passage  30  may be constructed from steel or steel alloys capable of withstanding the expected temperatures found within the combustor  14 , and may be constructed of similar or dissimilar materials from that of the disk  32  and/or the shroud  34 . 
     The disk  32  may be disposed at the second end  40  of the annular passage  30 . The disk  32  may be mechanically coupled; for example, welded or brazed, or the disk may be cast and/or machined as part of the annular passage  30 . The disk  32  may be constructed from steel or steel alloys capable of withstanding the expected temperatures found within the combustor  14 , and may be constructed of similar or dissimilar materials from that of the annular passage  30  and/or the shroud  34 . The disk  32  generally extends radially outward and axially downstream and/or upstream from the second end  40 . The disk  32  also includes an upstream surface  44  axially separated from a downstream surface  46  and a circumferential outer surface  48  extending axially from the upstream surface  44  to the downstream surface  46 . The disk  32  may include a plurality of passages  50  extending through the disk  32  from the upstream surface  44  to the downstream surface  46 . In particular embodiments, the passages  50  may be configured to impart swirl to the fuel and/or the working fluid flowing through the passages  50 . The passages  50  may be configured to impart clockwise and/or counterclockwise swirl. In this manner, the fuel and/or working fluid may premix prior to combustion, thereby resulting in a more efficient burn of the fuel and/or the working fluid and decreased NOx emissions. 
     The shroud  34  generally circumferentially surrounds and may be coupled to the disk  32 . In alternate embodiments, the shroud  34  may be coupled to the annular passage  30 . The shroud  34  may be coupled by any mechanical means, such as welding or brazing, or the shroud may be cast and/or machined as part of the annular passage  30  and/or the disk  32 . The shroud  34  includes an upstream end  52  axially separated from a downstream end  54  and forms an axial flow path for the fuel and/or the working fluid. The shroud  34  may be constructed from steel or steel alloys capable of withstanding the expected temperatures found within the combustor  14 , and may be constructed of similar or dissimilar materials from that of the annular passage  30  and/or the disk  32 . In particular embodiments, the shroud  34  may further include a flange  56  extending radially outward from the shroud  34 . The flange  56  may at least partially circumferentially surround the shroud  34  and may be disposed at any point axially along the shroud  34 . In particular embodiments, the flange  56  may be coupled to the shroud  34  at or near the upstream end  52 . The flange  56  may be coupled by any mechanical means, such as welding or brazing, or the flange  56  may be cast and/or machined as part of the shroud  34 . The flange  56  may be constructed from steel or steel alloys capable of withstanding the expected temperatures and may be annularly or conically shaped to reduce the flow resistance as the compressed working fluid flows around the flange  56 . 
     The spring  36  extends axially downstream from the upstream end  52  of the shroud  34  and includes a first surface  58  axially separated from a second surface  60 . The first surface  58  and/or the second surface  60  may be filed or otherwise formed to provide a generally flat surface. In particular embodiments, the spring  36  may be coupled to the shroud  34 . For example, the first surface  58  of the spring may be coupled to the upstream end of the shroud  34  and/or to the flange  56 . The spring  36  may be coupled to the shroud  34  or to the flange  56  by any mechanical means, such as welding or brazing. In particular embodiments, as shown, the spring  36  may include a bellows spring  36 . In this manner, the bellows spring  36  may provide a compressive force to seal the fuel nozzle(s)  24  with the cap assembly  26 . As a result, the bellows spring  36  may form a plenum wherein the working fluid may flow to cool the fuel nozzle(s)  24 . In addition, the bellows spring  36  may decrease the likelihood of misalignment in both the axial and/or radial directions between the fuel nozzle(s)  24  and the cap assembly  26  during assembly and/or operation of the combustor. In alternate embodiments, the spring  36  may include any spring  36  designed to resist compression loads. For example, the spring  36  may include a coil spring, a conical spring, a helical spring, a wave spring or a Belleville washer. The spring  36  may be constructed from steel or steel alloys or any material capable of withstanding the expected temperatures and compressive loads. 
     In particular embodiments, the fuel nozzle(s)  24  may include an at least partially annular plate  62  disposed on the second surface of the spring  60 . As shown in  FIG. 4 , the plate  62  may be configured to provide a first mating surface  64  so as to form a seal between the fuel nozzle(s)  24  and the cap assembly  26 . In this manner, the probability of the fuel leaking from behind the cap assembly  26  may be decreased, thereby reducing the likelihood of flashback and/or flame holding within the combustor  14 . For example, as shown in  FIGS. 3 , and  5 , the first mating surface  64  may include a flat surface and/or a grooved surface and the cap assembly  26  may include a complementary second mating surface  66 . The plate  62  may be coupled to the spring  36  by any mechanical means, such as welding or brazing. The plate  62  may be constructed from steel or steel alloys or any material capable of withstanding the expected temperatures and compressive loads. 
     As shown in  FIGS. 2 ,  4  and  5 , the cap assembly  26  at least partially surrounds the fuel nozzle(s)  24 . As shown in  FIGS. 4 and 5 , the cap assembly  26  generally includes one or more annular channel(s)  68  that are configured to receive the fuel nozzle(s)  24 . In particular embodiments, the cap assembly  26  may include one or more annular impingement sleeve(s)  70  disposed within the annular channel(s)  68 . The impingement sleeve(s)  70  may be generally larger in diameter than the shroud  34 . The impingement sleeve(s)  70  may include a plurality of radially extending cooling passages  72 . In this manner, the working fluid may flow through the cooling passages  72  to cool the fuel nozzle(s)  24 . The impingement sleeve(s)  70  may also include the second mating surface  66  extending radially outward from and at least partially circumferentially surrounding the impingement sleeve(s)  70 . The second mating surface  66  may be formed to be complementary to the first mating surface  64  of the plate  62 . The impingement sleeve(s)  70  may be sized to provide a radial gap  74  between the shroud  34  and the impingement sleeve  70 . In this manner, an effective cooling flow of the working fluid may be maintained to cool the fuel nozzle(s)  24  during operation of the gas turbine. 
     During assembly of the combustor, the fuel nozzle(s) may be inserted generally axially through the impingement sleeve. The annular plate first mating surface may seal against the impingement sleeve second mating surface due to a compressive force provided by the spring. The compressive force may also provide for proper axial and radial alignment between the fuel nozzle(s) and the cap assembly. Particularly, in the case where the cap assembly may be misaligned. During operation of the combustor, the spring may allow for thermal growth variations between the fuel nozzle(s) and the cap assembly without compromising the seal. As a result, leakage of the working fluid and/or the fuel may be significantly reduced. 
     The technical effect of the present matter is improved performance and/or operation of a gas turbine. In particular, by adding the shroud and and/or the spring to the fuel nozzle(s), wear between the cap assembly and the fuel nozzle(s) may be significantly reduced and the need for expensive wear coatings may be eliminated. As a result, the mechanical life of the combustor may be extended and the design simplified, thereby resulting in decreased operating costs. In addition, the design may be retrofitted to existing gas turbine combustors to increase the life of the fuel nozzle(s) and the cap assembly. 
     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 languages of the claims.