Patent Publication Number: US-9404659-B2

Title: Systems and methods for late lean injection premixing

Description:
FIELD OF THE DISCLOSURE 
     Embodiments of the present application relate generally to gas turbine engines and more particularly to combustor assemblies including late lean injection (LLI) premixing. 
     BACKGROUND OF THE DISCLOSURE 
     In gas turbine engines, mixtures of fuel and gas are combusted within a combustor disposed upstream from a transition piece and a turbine. The combustor produces high energy fluids from which mechanical energy can be derived for the generation of power and electricity. The high energy fluids are continually reused until significant levels of power generation cannot be derived at which point they are exhausted into the atmosphere. This exhaust often includes pollutants produced during the combustion, such as nitrous oxides (NOx) and carbon monoxide (CO). 
     Efforts have been expended to reduce the amount of pollutants produced by the combustion processes and include the development of LLI. LLI involves the injection of combustible materials into the flow of the high energy fluids at a location downstream from the normal combustion zone in the combustor. This downstream location could be defined as a section of the combustor liner or at a section of the transition piece. In any case, the combustible materials injected at this location increase the temperature and energy of the high energy fluids and lead to an increased consumption of CO with little to no significant increase in NOx for reasonable levels of LLI fuel flow. 
     BRIEF DESCRIPTION OF THE DISCLOSURE 
     Some or all of the above needs and/or problems may be addressed by certain embodiments of the present application. According to one embodiment, there is disclosed a LLI combustor assembly. The LLI combustor assembly may include a first interior in which a first fuel supplied thereto is combustible. The LLI combustor assembly may also include a flow sleeve annulus including a second interior in which a second fuel supplied thereto is combustible. The flow sleeve annulus may fluidly couple the first interior and the second interior. The LLI combustor assembly may also include at least one fuel injector disposed about the second interior. The at least one fuel injector may be configured to supply the second fuel to the second interior. The LLI combustor assembly may also include at least one elongate premixing conduit disposed about the flow sleeve annulus and in fluid communication with the at least one fuel injector. In this manner, the at least one elongate premixing conduit may be in fluid communication with a compressor discharge air and the second fuel such that the compressor discharge air and the second fuel are premixed within the elongate premixing conduit before entering the second interior by way of the at least one fuel injector. 
     According to another embodiment, there is disclosed a gas turbine engine assembly. The gas turbine engine assembly may include a combustor having a first interior in which a first fuel supplied thereto is combustible. The gas turbine engine assembly may also include a turbine that receives the products of at least the combustion of the first fuel. The gas turbine engine assembly may also include a flow sleeve annulus including a second interior in which a second fuel supplied thereto and the products of the combustion of the first fuel are combustible. The flow sleeve annulus may fluidly couple the combustor and the turbine. The gas turbine engine assembly may also include at least one fuel injector disposed about the second interior and configured to supply the second fuel to the second interior. The gas turbine engine assembly may also include at least one elongate premixing conduit disposed about the flow sleeve annulus and in fluid communication with the at least one fuel injector. In this manner, the at least one elongate premixing conduit may be in fluid communication with a compressor discharge air and the second fuel such that the compressor discharge air and the second fuel are premixed within the elongate premixing conduit before entering the second interior by way of the at least one fuel injector. 
     Further, according to another embodiment, there is disclosed a method for facilitating LLI. The method may include providing a first fuel to a first interior of a combustor. The method may also include providing a second fuel to at least one elongate premixing conduit disposed about a flow sleeve annulus. The method may also include providing compressor discharge air to the at least one elongate premixing conduit. The method may also include premixing the second fuel with the compressor discharge air within the at least one elongate premixing conduit. The method may also include injecting the premixed second fuel/compressor discharge air into a second interior of the combustor with at least one fuel injector. 
     Other embodiments, aspects, and features of the invention will become apparent to those skilled in the art from the following detailed description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  is a schematic of an example diagram of a gas turbine engine with a compressor, a combustor, and a turbine. 
         FIG. 2  is a cross-sectional view of a portion of a combustor assembly, according to an embodiment. 
         FIG. 3  is an example flow diagram of a method, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Illustrative embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. The present application may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like numbers refer to like elements throughout. 
     Illustrative embodiments are directed to, among other things, a combustor assembly including LLI premixing.  FIG. 1  shows a schematic view of a gas turbine engine  10  as may be used herein. As is known, the gas turbine engine  10  may include a compressor  15 . The compressor  15  may compress an incoming flow of air  20 . The compressor  15  may deliver the compressed flow of air  20  to a combustor  25 . The combustor  25  may mix the compressed flow of air  20  with a pressurized flow of fuel  30  and ignite the mixture to create a flow of combustion gases  35 . Although only a single combustor  25  is shown, the gas turbine engine  10  may include any number of combustors  25 . The flow of combustion gases  35  is in turn delivered to a turbine  40 . The flow of combustion gases  35  may drive the turbine  40  so as to produce mechanical work. The mechanical work produced in the turbine  40  may drive the compressor  15  via a shaft  45  and an external load  50  such as an electrical generator or the like. 
     The gas turbine engine  10  may use natural gas, various types of syngas, and/or other types of fuels. The gas turbine engine  10  may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, N.Y., including, but not limited to, those such as a 7 or a 9 series heavy duty gas turbine engine and the like. The gas turbine engine  10  may have different configurations and may use other types of components. 
     Other types of gas turbine engines may also be used herein. Moreover, multiple gas turbine engines, other types of turbines, and other types of power generation equipment may be used herein together. 
       FIG. 2  depicts an embodiment of a LLI combustor assembly  200  of the present application for facilitating LLI premixing. The LLI combustor assembly  200  may include a first interior  202  in which a first fuel  201  supplied thereto is combustible. For example, the first interior  202  may be a primary combustion zone of a combustor. In this manner, the first fuel  201  may be a primary fuel that is injected into the primary combustion zone. In some instances, the primary fuel may be premixed with a compressor discharge air before, during, or after being injected into the primary combustion zone. For example, one or more premixing nozzles may inject the first fuel  201 , having been premixed, into the first interior  202 . In other instances, the first fuel  201  may be injected directly into the first interior  202 . Accordingly, the first interior  202  may include a flow of primary combustion gases  204  from the primary combustion zone. The first interior  202  and the associated combustor components for creating the primary combustion gasses  204  are not illustrated in detail. That is, any number of combustor or nozzle arrangements may be used to provide the primary combustion gases  204 . 
     Still referring to  FIG. 2 , in an embodiment, a flow sleeve annulus  210  may connect the first interior  202  with a transition piece  212 . The transition piece  212  may direct the contents of the combustor assembly  200  to a turbine (not shown). In some instances, the flow sleeve annulus  210  may include a liner  211  forming a passageway for a cooling flow  213 . The cooling flow may include, among other things, compressor discharge air  216 . The flow sleeve annulus  210  may include a second interior  206  in which a second fuel  215  (having been mixed with air) may be supplied. For example, in certain embodiments, the second fuel  215  may be supplied to the second interior  206  via a fuel manifold  220  and associated fuel conduit  221  disposed about the flow sleeve annulus  210 . The first fuel and the second fuel may initiate from the same source or different sources. Moreover, the first fuel and the second fuel may be the same, dissimilar, or any combination thereof. Indeed, the first fuel and the second fuel may be any fuel. 
     In one embodiment, one or more fuel injectors  214  may be structurally supported by the flow sleeve annulus  210 . The fuel injectors  214  may be disposed about the second interior  202  and may be configured to supply the second fuel  215  (having been mixed with air) to the second interior  206 . The fuel injectors  214  may be disposed about the second interior  206  in any one of a single axial stage, multiple axial stages, a single axial circumferential stage, multiple axial circumferential stages, or the like. In this manner, the fuel injectors  214  may supply the second fuel  215  to the second interior  206  in a direction that is substantially traverse to a predominant flow of the flow sleeve annulus  210 . Any number, type, or arrangement of fuel injector nozzles  214  may be used. 
     In certain aspects, at least one elongate premixing conduit  208  may be disposed about the flow sleeve annulus  210 . The elongate premixing conduit  208  may include any passageway, channel, slot, duct, or the like that facilitates the mixing of fuel and air. For example, in some instances, the elongate premixing conduit  208  may be formed between an inner and outer wall of the flow sleeve annulus  210  and may extend wholly or partially along the axial length of the flow sleeve annulus  210 . 
     In an embodiment, the elongate premixing conduit  208  may be in fluid communication with the fuel injectors  214 , a compressor discharge air  216 , and the second fuel  215 . In this manner, the compressor discharge air  216  and the second fuel  215  may be premixed within the elongate premixing conduit  208  before entering the second interior  206  by way of the fuel injectors  214 . For example, the fuel manifold  220  may be in fluid communication with the elongate premixing conduit  208  via the fuel conduit  221  for supplying the second fuel  215  to the elongate premixing conduit  208 , as denoted by the dotted line  222 . Compressor discharge air  216  may enter the elongate premixing conduit  208  at inlet  218  such that the second fuel  215  and the compressor discharge air  216  may be premixed within the elongate premixing conduit  208  thereby forming an air/fuel mixture as denoted by dashed line  224 . Accordingly, in this embodiment, a portion of the axial length of the flow sleeve annulus  210  may be utilized to premix the second fuel  215  with the compressor discharge air  216 . The premixed air/fuel mixture may then be directed into the second interior  206  by the fuel injector nozzles  214 . 
     The second fuel  215  and the compressor discharge air  216  may be supplied to the elongate premixing conduit  208  by any number of circuit arrangements. For example, the LLI combustor assembly  200  may include one or more fuel conduits  221  (or feeds) in fluid communication with the elongate premixing conduit  208  and/or one or more compressor discharge air inlets  218  (or feeds) in fluid communication with the elongate premixing conduit  208 . In this manner, any number or combination of conduits or passageways may be used to supply the fuel  215  and/or air  216  to the elongate premixing conduits  208 . Moreover, any number or combination of elongate premixing conduits  208  may be used. 
     The transition piece  212  may also include a similar configuration for facilitating LLI premixing. That is, the transition piece may include any number or combination of fuel manifolds, fuel conduits, air inlets, elongate premixing conduits, fuel injectors, or the like disposed about the transition piece  212  in a similar fashion to the flow sleeve annulus  210  described above. 
       FIG. 3  illustrates an example flow diagram of a method  300  for facilitating late lean injection. In this particular embodiment, the method  300  may begin at block  302  of  FIG. 3  in which the method  300  may include providing a first fuel to a first interior of a combustor. For example, the first interior may be a primary combustion zone of a combustor. At block  304 , the method  300  may include providing a second fuel to at least one elongate premixing conduit disposed about a flow sleeve annulus. For example, the second fuel may be supplied to the elongate premixing conduit via a fuel manifold and associated fuel conduit disposed about the flow sleeve annulus. At block  306 , the method  300  may include providing compressor discharge air to the at least one elongate premixing conduit. The compressor discharge air may be provided to the elongate premixing conduit via any number of openings or slots about the elongate premixing conduit. For example, the compressor discharge air may be provided before and/or after the second fuel enters the elongate premixing conduit. At block  308 , the method  300  may include premixing the second fuel with the compressor discharge air within the at least one elongate premixing conduit. In this manner, the second fuel and the compressor discharge air may be mixed along the axial length of all or part of the flow sleeve annulus. At block  310 , the method  300  may include injecting the premixed second fuel/compressor discharge air into a second interior of the combustor with at least one fuel injector. 
     Although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments.