Patent Publication Number: US-2017370589-A1

Title: Multi-tube late lean injector

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with Government support under Contract No. DE-FE0023965 awarded by the United States Department of Energy. The Government has certain rights in this invention. 
    
    
     TECHNICAL FIELD 
     This invention relates generally to a combustion system and, more specifically, to a combustion system that comprises a primary reaction zone and a secondary reaction zone, which includes an injector for injecting a fluid into a stream of combustion products generated within the primary reaction zone. 
     BACKGROUND 
     Fuel is delivered from a fuel source to a combustion section of a gas turbine where the fuel is mixed with air and ignited to generate hot combustion products. The hot combustion products are working gases that are directed to a turbine section where they effect rotation of a turbine rotor. It has been found that the production of NOx gases from the burning fuel in the combustion section can be reduced by providing a secondary combustion zone downstream from a main combustion zone. The fuel-air mixture provided to the secondary combustion zone may be a lean mixture. 
     BRIEF SUMMARY 
     One aspect of the disclosed technology relates to a micromixer injector having a compact arrangement including a plurality of premixing tubes having a spaced-apart configuration at an upstream face of the micromixer and a more densely packed arrangement at a downstream face. 
     One exemplary but nonlimiting aspect of the disclosed technology relates to a micromixer injector comprising a fuel plenum to receive a supply of fuel; a plurality of premixing tubes extending through the fuel plenum, each tube having an air inlet at an intake end of the tube and an outlet at a discharge end of the tube, the air inlet of each tube being configured to receive a supply of air, each tube having a plurality of fuel holes formed therein to receive the supply of fuel for mixing with the air in the tube; and an upstream face having the inlet of each tube formed therein, and a downstream face having the outlet of each tube formed therein, wherein the air inlet of each tube has a first geometrical shape and the outlet of each tube has a second geometrical shape that is different from the first geometrical shape, and wherein an overall inlet area of the plurality of premixing tubes on the upstream face is larger than an overall outlet area of the plurality of premixing tubes on the downstream face such that the plurality of premixing tubes are relatively spaced-apart at the upstream face and more densely packed at the downstream face. 
     Another exemplary but nonlimiting aspect of the disclosed technology relates to a combustor section comprising a primary combustion system generating a stream of combustion products: a secondary combustion system located downstream of the primary combustion system, the secondary combustion system including: at least one micromixer injector to deliver a fuel air mixture into the stream of combustion products, the at least one micromixer injector comprising: a fuel plenum to receive a supply of fuel; a plurality of premixing tubes extending through (be fuel plenum, each tube having an air inlet at an intake end of the tube and an outlet at a discharge end of the tube, the air inlet of each tube being configured to receive a supply of air, each tube having a plurality of fuel holes formed therein to receive the supply of fuel for mixing with the air in the tube; and an upstream face having the inlet of each tube formed therein, and a downstream face having the outlet of each tube formed therein, wherein the air inlet of each tube has a first geometrical shape and the outlet of each tube has a second geometrical shape that is different from the first geometrical shape, and wherein an overall inlet area of the plurality of premixing tubes on the upstream face is larger than an overall outlet area of the plurality of premixing tubes on the downstream face such that the plurality of premixing tubes are relatively spaced-apart at the upstream lace and more densely packed at the downstream face. 
     Other aspects, features, and advantages of this technology will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a pan of this disclosure and which illustrate, by way of example, principles of this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings facilitate an understanding of the various examples of this technology. In such drawings: 
         FIG. 1  is a partial cross-sectional side view of a turbomachine in accordance with an example of the disclosed technology; 
         FIG. 2  is a cross-sectional side view of an example of the combustor of the turbomachine of  FIG. 1 ; 
         FIG. 3  is an enlarged detail of  FIG. 2 ; 
         FIG. 4  is a front perspective view of a micromixer slot injector according to an example of the disclosed technology; 
         FIG. 5  is rear perspective view of the micromixer slot injector of  FIG. 4 ; 
         FIG. 6  is another rear perspective view of the micromixer slot injector of  FIG. 4 ; 
         FIG. 7  is a partial rear perspective view of a micromixer according to another example of the disclosed technology; 
         FIG. 8  is a left side view of the micromixer slot injector of  FIG. 4 ; 
         FIG. 9  is a right side view of the micromixer slot injector of  FIG. 4 ; 
         FIG. 10  is a top view of the micromixer slut injector of  FIG. 4 ; 
         FIG. 11  is a front view of the micromixer slot injector of  FIG. 4 ; 
         FIG. 12  is a cross-sectional front perspective view along the line  12 - 12  in  FIG. 10 ; 
         FIG. 13  is a cross-sectional rear perspective view along the line  13 - 13  in  FIG. 8 ; 
         FIG. 14  is a cross-sectional front perspective view along the line  13 - 13  in  FIG. 8 ; 
         FIG. 15  is a cross-sectional front perspective view along the line  15 - 15  in  FIG. 11 ; 
         FIG. 16  is a cross-sectional front perspective view along the line  16 - 16  in  FIG. 10 ; and 
         FIG. 17  is a schematic representation illustrating flow paths of fluids used in the secondary combustion system, in accordance with an example of the disclosed technology. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
       FIG. 1  is a partial cross-sectional side view of a turbomachine  10  in accordance with an embodiment of the disclosed technology. The turbomachine  10  may comprise a primary combustion system  22  and a secondary combustion system  24  including at least one micromixer slot injector  200 , (not illustrated in  FIG. 1 ), for injecting a secondary fluid, into a stream of combustion products generated by the primary combustion system  22 . 
     An embodiment of the turbomachine  10  may comprise an inlet section  14 ; a compressor section  16  downstream from the inlet section  14 ; a combustion section  20  comprising the primary combustion system  22  downstream from the inlet section  14 , and the secondary combustion system  24  downstream from the primary combustion system  22 ; a turbine section  18  and an exhaust section  26 . As illustrated in  FIG. 2 , for example, the secondary combustion system  24  may comprise at least one micromixer slot injector  200  for injecting a secondary fluid, such as, but not limited to, a fuel and air mixture, into a stream of combustion products flowing from the primary combustion system  22 . 
     Referring again to  FIG. 1 , the turbomachine  10  may also include a turbine section  18 . The turbine section  18  may drive the compressor section  16  and the load  28  through a common shaft connection. The load  28  may be, but is not limited to, an electrical generator, a mechanical drive or the like. 
     The combustion section  20  may include a circular array of a plurality of circumferentially spaced combustors  110 . A fuel and air mixture may be burned in each combustor  110  lo produce a stream of combustion products, which may flow through a transition piece  122  and then to a plurality of turbine nozzles  112  of the turbine section  18 . A conventional combustor  110  is described in U.S. Pat. No. 5,259,184. For purposes of the present description, only one combustor  110  may be referenced, all of the other combustors  110  arranged about the combustion section  20  may be substantially identical to the illustrated combustor  110 . 
     Although  FIG. 1  illustrates a plurality of circumferentially spaced combustors  110  and  FIG. 2  shows a cross-section of a combustor  110  that may be considered a can combustor, the disclosed technology may be used in conjunction with other combustor systems including and not limited to annular or can combustor systems. 
       FIG. 2  is a cross-sectional side view of an embodiment of a combustor  110  of the combustion section  20  in  FIG. 1 .  FIG. 2  illustrates the combustor  110  comprising a primary combustion system  22  and a secondary combustion system  24  within an assembly; as described in U.S. Pat No. 6,047,550 and U.S. Pat. No. 6,192,688. The combustor  110  comprises a plurality of micromixer slot injectors  200 , and a transition piece  122 , which generally allows for the generated combustion products to flow to the turbine nozzle  112 . 
     The primary combustion system  22  may include a casing  126 , an end cover  128 , a plurality of start-up fuel nozzles  130 , a plurality of premising fuel nozzles  116 , a cap assembly  134 , a flow sleeve  120 , and a combustion liner  132  within the flow sleeve  120 . An example of a cap assembly  134  is described in U.S. Pat. No. 5,274,991. Combustion in the primary combustion system  22  may occur within the combustion liner  132 , Typically, combustion air is directed within the combustion liner  132  via the flow sleeve  120  and enters the combustion liner  132  through a plurality of openings formed in the cap assembly  134 . The air may enter the combustion liner  132  under a pressure differential across the cap assembly  134  and mixes with fuel from the start-up fuel nozzles  130  and/or the premising fuel nozzles  116  within the combustion liner  132 . Consequently, a combustion reaction occurs within the combustion liner  132  that releases heat energy mat drives the turbine section  18 . 
     High-pressure air from the primary combustion system  22  may enter the How sleeve  120  and an impingement sleeve  118 , from an annular plenum  144 . The compressor section  16 , represented by a series of vanes, blades, other compressor components  114  and a diffuser  136 , supplies this high-pressure air. Each premixing fuel nozzle  116  may include a swirler  148 , which may comprise a plurality of swirl vanes  150  that impart rotation to the entering air and allowing for the entering fuel to be distributed within the rotating air stream. The fuel and air then mix in an annular passage within the premix fuel nozzle  116  before reacting within the primary reaction zone  152 . 
     As illustrated in  FIGS. 2 and 3 , a plurality of micromixer slot injectors  200  may penetrate the transition piece  122  or combustion liner  132  and introduce additional fuel mixture into the secondary reaction zone  124  within the combustor  110 . The combustion products exiting the primary reaction zone  152  may be at a thermodynamic stale that allows for the auto-ignition of the secondary fuel mixture. The resulting secondary hydrocarbon fuel oxidation reactions go to substantial completion in the transition piece  122 . An embodiment of the secondary combustion system  24  and micromixer slot injector  200  may allow for burning a fuel different from the fuel burned within the primary combustion system  22 . For example, the injector may allow for burning a synthetic fuel, syngas, or the like. 
     Referring to  FIGS. 2 and 3 , an embodiment of the disclosed technology may function with at least one micromixer slot injector  200 . located within the combustion liner  132  or transition piece  122 . An alternate embodiment of the disclosed technology may incorporate a plurality of micromixer slot injectors  200  positioned (e.g., circumferentially) in the combustion liner  132  or transition piece  122 , as shown in  FIGS. 2 and 3 . 
     Turning to  FIGS. 4-6 , micromixer slot injector  200  is shown. Micromixer slot injector  200  is configured to receive supplies of air and fuel and to discharge a fuel/air mixture (e.g., a lean fuel/air mixture). Although the micromixer slot injector has a compact arrangement, since there is limited space in the circumferential regions of the combustion liner  132  and transition piece  122  downstream of the primary reaction zone, the configuration of the micromixer slot injector enables the production of a fuel/air mixture with a high degree of fuel/air mixedness. A well-mixed fuel air stream is preferable in order to minimize the formation of nitrogen oxide (NOx) emissions. 
     Micromixer slot injector  200  includes a body  205  having an upstream lace  207  and a downstream face  209 , as shown in  FIGS. 4-6 . A plurality of premixing tubes  220  extend between upstream face  207  and downstream face  209 , forming a plurality of corresponding air inlets  223  in the upstream face  207  and a plurality of corresponding outlets  227  in the downstream face. The air inlets  223  are arranged to receive a supply of air (e.g., bled off from compressor section  16 ). 
     Referring to  FIGS. 4-6 and 10 , a fuel inlet  210  is formed in body  205  and configured to receive a supply of fuel. The fuel inlet is in fluid communication with a fuel plenum  230  within body  205 . as best shown in  FIG. 12 . Fuel in the plenum  230  is received through a plurality of fuel holes  225  in each tube  220  to mix with air in the tubes. The plurality of premixing tubes  220  have a spaced-apart arrangement in the plenum  230  (which is toward the upstream face  207 ), as can be seen in  FIG. 12 . This arrangement enables the fuel to flow around all of the tubes so as to be evenly distributed among the tubes, which results in a well-mixed fuel/air stream. 
     As best seen in  FIGS. 13-15 , each of the plurality of premixing tubes  220  has an intake end  222 , a transition portion  224  and a discharge end  226 . The intake end  222  includes the air inlet  223  which is formed in the upstream face  207  of body  205 . The fuel holes  225  are also preferably formed in the intake ends  222  of the tubes. In the illustrated embodiment, the air inlet  223  of each tube has a non-rectilinear shape (e.g., an arcuate shape such as a circular shape). The non-rectilinear shape of the tubes continues into, and preferably through, the intake ends  222  of the tubes. The non-rectilinear shape facilities the spaced-apart arrangement of the tubes and the provision of a plurality of evenly distributed fuel holes  225  in the tubes. 
     Still referring to  FIGS. 13-15 , the transition portion  224  of each tube  220  extends between the intake end  222  and the discharge end  226 . The transition portion  224  is also the portion of each tube where the tube transitions from the non-rectilinear shape to a non-circular shape (e.g., a rectilinear shape). 
     The discharge end  226  of each tube  220  extends from the transition portion  224  to outlet  227  which is formed in the downstream face  209  of the micromixer slot injector, as can be seen in  FIGS. 13-15 . The outlets  227  have a non-circular shape (e.g., a rectilinear shape such as rectangular). The non-circular shape of the outlets  227  facilitates a dense packing of the outlets on the downstream face  209 . For example, each tube  220  may be bounded by at least one (e.g., 2 or 3) common wall with an immediately adjacent tube  220  such that no space exists between immediately adjacent tubes. In the illustrated example, each tube  220  (except for the four tubes at the upper and lower ends) has at least three common walls with immediately adjacent tubes. Those skilled in the art will recognize that the outlets could have other non-circular shapes, such as the triangular shaped outlets  337  shown in  FIG. 7 . 
     The intake end  222 , transition portion  224  and discharge end  226  of each tube form a passageway  229  extending from the air inlet  223  to the outlet  227 , as illustrated in  FIG. 14 . The length of each passageway  229  may be at least  10  times the diameter of the respective tube  220  to allow the fuel/air mixture to achieve sufficient premixing. The diameter of the tube  220  at the air inlet  223  may be between 0.25 and 0.45 inches (e.g.. 0.3-0.4 inches). Thus, micromixer slot injector  200  has a compact configuration. However, the arrangement of the air inlets  223  and the outlets  227  of the tubes  220  allow for a scalable configuration; thus, larger and/or smaller configurations are feasible. 
     As can be seen in  FIGS. 4-6, 8, 9 and 13-16 , body  205  of micromixer slot injector  200  has a tapering profile from the upstream face  207  to the downstream face  209 . That is, the micromixer slot injector tapers from an upstream end where the plurality of premixing tubes  220  are spaced-apart and have a first geometrical shape to a downstream end where the tubes are more densely packed and have a second, different geometrical shape. In  FIG. 16 , spaces  235  are shown between the discharge ends  226  of the tubes. The spaces  235  are smaller than the spaces between the tubes at the upstream face  207 . At the downstream face  209 , the spaces  235  are eliminated thereby allowing the outlets  227  of the tubes to be stacked without any wastage of space. Since there are no spaces between the outlets  227 , the volume of flow exiting the outlets relative to the overall outlet area  236  (described below) is maximized. Those skilled in the art will recognize that the downstream face  209  could be arranged such that small spaces exist between the tubes. 
     As can be seen in  FIGS. 12 and 13 , tubes that are arranged side-by-side on the upstream face  207  are stacked vertically at the downstream face  209 , resulting in an elongate structure at the downstream face. 
     In other words, an overall inlet area  232  ( FIG. 11 ), representing a surface area of upstream face  207  required to accommodate the air inlets  223  of the plurality of premixing tubes  220  in the spaced-apart arrangement is larger than an overall outlet area  236  ( FIG. 5 ) representing a surface area of downstream face  209  required to accommodate the outlets of the plurality of premixing tubes in the densely paced arrangement. Thus, the overall outlet area  236  on downstream face  209  has an elongate structure that extends along a longitudinal axis of combustor  110 . Those skilled in the art will recognize that the overall outlet area  236  may have a shape other than the slot shape formed by the elongate structure of the downstream face  209 . For example, the overall outlet area  236  and the downstream face  209  could have a hexagonal shape. 
     The elongate structure of the overall outlet urea  236  facilitates the micromixer slot injector in achieving deep penetration of the fuel air mixture into the stream of combustion products produced by the primary combustion system. Deep penetration of the fuel/air mixture results in an efficient entrainment of the fuel/air mixture into the stream of combustion products, which minimizes the formation of NOx emissions. 
     Turing to  FIG. 17 , it can be seen that outlets  227  that are relatively downstream in the direction of the combustion flow achieve deeper penetration into the combustion flow as compared to more upstream outlets. This occurs because the fuel/air mixture flowing from each relatively upstream outlet acts as a buffer for each downstream outlet enabling the How of each downstream outlet to be initially somewhat shielded from the combustion flow, thereby permitting progressively deeper penetration into the combustion flow. As a result, micromixer slot injector  200  can be scaled to achieve a desired penetration, since the greater the number of tubes in the micromixer slot injector the greater the length of the overall outlet area  236  in the direction of the combustion flow. 
     It is noted that micromixer slot injector  200  may be mounted flush or in an inserted arrangement in the combustion liner  132  or transition piece  122 . A flush mounting, as shown in  FIG. 3 , may reduce the amount of heat transferred to the micromixer slot injector from the combustion flow, thereby requiring less energy to cool the micromixer slot injector. Other the other hand, penetration of the fuel air mixture into the combustion flow may be enhanced by inserting the micromixer slot injector a desired depth into the combustion flow. Overheating of the micromixer slot injector may be prevented by the flow of air and fuel which cool the micromixer slot injector as they pass through. In  FIG. 17 , micromixer slot injector  200  is shown slightly inserted into the transition piece  122 . 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred examples, it is to be understood that the invention is not to be limited to the disclosed examples, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.