Patent Publication Number: US-2012031097-A1

Title: Multi-premixer fuel nozzle

Description:
TECHNICAL FIELD 
     The present application relates generally to gas turbine engines and more particularly relates to the use of fuel nozzles with one fuel supply and mounting column and multiple premixers for premixing prior to combustion. 
     BACKGROUND OF THE INVENTION 
     Current fuel nozzle designs for gas turbine combustion systems generally include one central mounting and fuel supply center body per fuel nozzle or a separate fuel supply. Several fuel and air circuits may be contained within the center body. When the fuel nozzle counts is in the range of about four to six nozzles, current combustion chambers with the center bodies generally present no problem from the standpoint of distributing airflow to the more central nozzles. 
     As the fuel nozzle count increases, however, the center bodies begin to restrict airflow to the more central nozzles. This restriction may cause unacceptable variations in the airflow uniformity between the center and outer fuel nozzles and between adjacent nozzles. This variation may cause uneven fuel air mixing and may result in decreased flame holding margins and non-uniform flame temperatures within the within the combustion chamber. Further, these uneven temperatures may lead to increased emissions and durability concerns. 
     There is thus a desire therefore for a gas turbine combustion system with more even airflow distribution about the center and the outer nozzles, regardless of the nozzle count. Such a combustion system should maintain reduced emissions while providing flame holding margins and low combustion dynamics response over a variety of operating conditions. 
     SUMMARY OF THE INVENTION 
     The present application thus provides a fuel nozzle for use in a gas turbine. The fuel nozzle may include a mounting flange, a number of premixers attached to each other, and a number of gas pathways extending from the mounting flange to the number of premixers. 
     The present application further provides a combustion chamber. The combustion chamber may include a center nozzle with a fuel passage and a premixer and a number of outer nozzles. Each of the outer nozzles may include a number of fuel passages and a number of premixers. 
     The present application further provides a fuel nozzle for use in a gas turbine. The fuel nozzle may include a mounting flange, a number of premixers attached to each other, a number of gas tubes extending from the mounting flange to the premixers, and an outer shell surrounding the fuel tubes. 
     These and other features of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a gas turbine engine. 
         FIG. 2  is a perspective view of a known standard single center body fuel nozzle. 
         FIG. 3  is a perspective view of a known combustion chamber with a number of nozzles having a single premixer per center body. 
         FIG. 4  is a perspective view of a multiple premixer fuel nozzle as is described herein. 
         FIG. 5  is a perspective view of a combustion chamber with a number of nozzles having multiple premixers per center body as is shown in  FIG. 4 . 
         FIG. 6  is side cross-section view of an alternative embodiment of a multiple premixer fuel nozzle as is described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, in which like numbers refer to like elements throughout the several views,  FIG. 1  shows a schematic view of a gas turbine engine  10 . As is known, the gas turbine engine  10  may include a compressor  20  to compress an incoming flow of air. The compressor  20  delivers the compressed flow of air to a combustor  30 . The combustor  30  mixes the compressed flow of air with a compressed flow of fuel and ignites the mixture. (Although only a single combustor  30  is shown, the gas turbine engine  10  may include any number of combustors  30 .) The hot combustion gases are in turn delivered to a turbine  40 . The hot combustion gases drive the turbine  40  so as to produce mechanical work. The mechanical work produced in the turbine  40  drives the compressor  20  and an external load  50  such as an electrical generator and the like. The gas turbine engine may use natural gas, various types of syngas, and other types of fuels. 
     Other types of gas turbine engines  10  may be used herein. The gas turbine engine  10  may have other configurations and may use other types of components. Multiple gas turbine engines  10 , other types of turbines, and other types of power generation equipment may be used herein together. 
       FIG. 2  shows a known fuel nozzle  100 . Generally described, the fuel nozzle  100  may include a flange  110  on one end that leads to a premixer  115 . The nozzle  100  may include a center body tube  120  that extends from the flange  110  and through the premixer  115 . Positioned within the center body tube  120  may be a purge air pathway  130  extending therethrough. A number of fuel pathways  140  may encircle the purge air pathway  130  and may extend from the flange  110  through the center body tube  120 . The fuel nozzle  100  also may include a swirler  150  positioned with the center body tube  120  of the premixer  115 . The swirler  150  may extend from the center body tube  120  to a burner tube  160 . The swirler  150  may include a number of vanes  170 . The fuel pathways  140  may extend from the flange  110  through the center body tube  120  in-part and may exit via the vanes  170  of the swirler  150 . The premixer  115  of the fuel nozzle  100  also may include an inlet section  190  for the admission of air through the swirler  150 . Other configurations of the fuel nozzle  100  and the components thereof may be used herein. 
     In use, gas may enter the flange  110 , pass into the premixer  115 , and exit from the vanes  170  of the swirler  150 . The gas flow may mix with an incoming airflow from the inlet section  190 . The gas and air flows thus may mix within the premixer  115  and then may be ignited downstream of the fuel nozzle  100 . 
     As is shown in  FIG. 3 , multiple fuel nozzles  100  may be mounted within an end cover assembly  200  of a combustion chamber  205 . As is shown, each of the nozzles has a single fuel supply tube  210 . The use of the multiple nozzles  100 , however, may create a circuitous path  220  for the airflow, at least with respect to one or more center nozzles  230 . This restricted airflow between the center nozzles  230  and a number of outer fuel nozzles  240 , however, may cause unacceptable variations in the airflow. These variations may cause uneven temperatures within the combustion chamber  205  as a whole. As described above, these uneven temperatures may lead to increase emissions and durability concerns. 
       FIG. 4  shows a multiple premixer fuel nozzle  250  as is described herein. The multiple premixer fuel nozzle  250  also may include a flange  260  leading to a center body tube  270 . Likewise, a purge pathway  280  may extend from the flange  260  and through the center body tube  270 . Similarly, a number of fuel pathways  290  may extend from the flange  260  and through the center body tube  270 . Other configurations may be used herein. 
     The multiple premixer fuel nozzle  250  may include a number of premixers  300 . Although three (3) premixers  300  are shown, any number of premixers  300  may be used. Each premixer  300  may include a swirler  310  positioned therein. As described above, each swirler  310  may include a number of vanes  320 . The fuel pathways  290  may pass through the flange  260 , through the center body tube  270  in part, into each premixer  300 , and exit about the vanes  320  of the swirler  310 . Each premixer  300  also may include a burner tube  335  positioned about the swirler  310  and an air inlet section  340  in a manner similar to that described above 
     In use, gas flows through the fuel pathways  290  and then into the vanes  320  of the swirler  310  of each premixer  300 . Likewise, air passes through the inlet sections  340  and the swirlers  310  so as to mix with the gas within the burner tube  335 . The mixed pathways are then ignited downstream of the multiple premixer fuel nozzle  250 . 
       FIG. 5  shows the use of the multiple premixer fuel nozzles  250  within a combustion chamber  350 . As is shown, a single fuel nozzle  100  is used as a center nozzle  360  while a number of the multiple premixer fuel nozzles  250  are used as a number of outer fuel nozzles  370 . As is shown, the combustor chamber  350  has a simplified airflow path  380  to the center nozzle  360  in particular. Specifically, the airflow path  380  may have fewer restrictions as compared to the design of  FIG. 3 . Further, less restricted air access also is available to the air inlet sections  340  of each premixer  300  of the outer fuel nozzles  370 . 
     The use of the multiple premixer fuel nozzles  250  thus not only provides an even airflow distribution among the nozzles  100 ,  250  so as to increase the overall efficiency of the gas turbine engine  10 , but use of the multiple premixer fuel nozzles  250  also should provide a cost reduction relative to the single center body designs of the fuel nozzles  100 . Moreover, the overall design of the combustion chamber  350  also may be simplified. 
       FIG. 6  shows a cross-sectional view of an alternative embodiment of a multiple premixer fuel nozzle  400 . Instead of use of the center body tube  270 , the multiple premixer fuel nozzle  400  may include a number of fuel tubes  410  that extend from a flange  420  to a number of premixers  430 . The space between the flange  420  and the premixers  430  may be encased in an outer shell  440 . The outer shell  440  provides structure in the absence of the center body tube  270 . The fuel tubes  410  thus may be made out of flexible tubing as opposed to a structural member. Each fuel tube  410  may be in communication with one of the premixers  430 . The flange  420  may include a number of apertures therein including a number of fuel apertures  450  and air apertures  460 . The fuel apertures  450  may be in communication with the fuel tubes  410  while the air apertures  460  may direct a flow of air towards each of the premixers  430 . Other configurations may be used herein. 
     The use of the multiple fuel tubes  410  thus allows a variable flow of fuel to each of the premixers  430 . Depending upon the nature of the load, steady state conditions, and transient conditions, varying the flow of fuel may be desired to each of the premixers  430 . 
     It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.