Patent Publication Number: US-8113002-B2

Title: Combustor burner vanelets

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     This invention has been made with government support under Contract No. DE-FC26-05NT42643 awarded by the U.S. Department of Energy. The Government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     The present application relates generally to gas turbine engines and more particularly relates to a combustor burner with vanelets positioned between the fuel vanes. 
     BACKGROUND OF THE INVENTION 
     Various types of combustors are known and used in gas turbine engines. In turn, these combustors generally use different types of fuel burners or nozzles depending upon the type of fuel in use. For example, most natural gas fired systems operate using lean premixed flames. In these systems, fuel is mixed with air upstream of the reaction zone to create a premixed flame. One example is a “swozzle” (swirler+nozzle) in which the fuel ports are positioned about a number of extending vanes so as to inject the fuel into the air stream. Alternatively in systems using syngas or other types of fuels, diffusion nozzles may be used to inject the fuel and the air directly into the combustion chamber due to the generally higher reactivity of the fuel. 
     Current combustor designs, however, focus on fuel flexibility with respect to the use of natural gas and other types of fuels. As a result, operational issues may arise when switching from one type of fuel to another while using the same components. For example, syngas may have a much higher volumetric flow rate as opposed to natural gas due to its lower Modified Wobbe Index. As a result of this and the high reactivity of some of these fuels, flame holding issues may arise. The design of the combustor and its components thus should accommodate these varying fuel characteristics such as different fuel reactivities, fuel temperatures, heating values, molecular weight, etc. 
     There is thus a desire for improved combustor components in general and an improved burner in specific. Such a burner may provide for good fuel and air mixing for greater fuel flexibility while maintaining system efficiency and limiting overall emissions. Such fuel flexible systems should accommodate natural gas and other types of fuels without expensive equipment changeovers. 
     SUMMARY OF THE INVENTION 
     The present application thus provides a burner for use with a combustor of a gas turbine engine. The burner may include a center hub, a shroud, a pair of fuel vanes extending from the center hub to the shroud, and a vanelet extending from the center hub and/or the shroud and positioned between the pair of fuel vanes. 
     The present application further provides a method of mixing fuel and air in a combustor burner of a gas turbine. The method includes the steps of flowing the air into a swozzle assembly, flowing the fuel through a number of fuel vanes in the swozzle assembly, imparting swirl to the flow of air and the flow of fuel to create a premixed flow, and positioning a vanelet between a pair of the of the fuel vanes so as to at least maintain the premixed flow at a predetermined velocity as the premixed flow leaves the fuel nozzles. 
     The present application further provides for a swozzle assembly for use with a combustor of a gas turbine engine. The swozzle assembly may include a center hub, a shroud, a number of swozzle vanes extending from the center hub to the shroud, and a number of vanelets extending from the center hub and/or the shroud and with one of the vanelets positioned between each pair of the swozzle vanes. 
     These and other features of the present patent 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 schematic view, partly in cross-section, of a conventional swozzle type burner. 
         FIG. 3  is a perspective view of the fuel vanes of the swozzle burner of  FIG. 2 . 
         FIG. 4  is a perspective view of the fuel vanes with vanelets in the swozzle burner as is described herein. 
         FIG. 5  is a plan view of a vanelet of  FIG. 4 . 
         FIG. 6  is an alternative embodiment of the swozzle burner as is described herein with extended vanelets. 
         FIG. 7  is an alternative embodiment of the swozzle burner as is described herein with the vanelets positioned on the shroud. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     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 the combustor  30 . The combustor  30  mixes the compressed flow of air with a 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 delivered in turn to a turbine  40 . The turbine  40  drives the compressor  20  and an external load  50  such as an electrical generator and the like. The gas turbine engine  10  may use other configurations and components herein. The gas turbine engine  10  may use natural gas, various types of syngas, and other fuels. 
       FIG. 2  shows a swozzle burner  60  that may be used with the combustor  30  as described above. As is known, the swozzle burner  60  may include a number of annular fuel passages  70 . Some of the annular fuel passages  70  may extend to a diffusion tip  80  while others may extend to a swozzle assembly  90 . The swozzle assembly  90  may include a center body or a hub  100  and a shroud  110  connected by a series of airfoil shaped fuel vanes  120 . Each vane  120  may have an upstream end  122  and a downstream end  124 . As is shown in  FIGS. 2 and 3 , each fuel vane  120  may include one or more fuel injection ports  130 . The swozzle assembly  90  also defines an air inlet  140  upstream of the fuel vanes  120 . Other configurations of the swozzle burner  60  and the swozzle assembly  90  may be used herein 
     In operation, fuel injected from the fuel injection ports  130  of the fuel vanes  120  thus mixes with the incoming airflow from the air inlet  140 . The shape of the fuel vanes  120  imparts swirl to the fuel flows and the air flows so as to promote good mixing in a premix flow. The premix flow is then ignited downstream of the swozzle assembly  90 . 
       FIGS. 4 and 5  show portions of a swozzle burner  150  as is described herein. The swozzle burner  150  may include the components of the swozzle burner  60  described above. The swozzle burner  150  also includes a number of vanelets  160 . The vanelets  160  may be positioned between the fuel vanes  120  that are described above. The vanelets  160  may be positioned about the downstream end  124  of the fuel vanes  120  and may extend for any length towards the upstream end  122  as shown in the two rightmost vanelets of  FIG. 4 . The vanelets  160  also may be positioned anywhere upstream of the downstream end  124  of the fuel vanes  120  and may extend for any length towards the upstream end  122  as shown by the leftmost vanelet in  FIG. 4 . The vanelets  160  may have an oval-like shape as is shown or any desired shape or desired size. The vanelets  160  may include one or more fuel injection ports  170  therein. The vanelets  160  also may be used without the fuel injection ports  170 . Further, some of the vanelets  160  may have a fuel injection port  170  and others may not. Any number of vanelets  160  may be used. The vanelets  160  also may extend off the hub  100  or come down from the shroud  110  as is described below. 
       FIG. 6  shows an alternative embodiment of a swozzle burner  180 . In this embodiment, the swozzle burner  180  may have a number of vanelets  190  that extend at least in part beyond the downstream end  124  of the fuel vanes  120 . The vanelets  190  may have an oval-like shape as is shown or any desired shape or desired size. The vanelets  190  also may have a fuel injection port  200  therein. The vanelets  190  also may be used without the fuel injection ports  200 . Further, some of the vanelets  190  may have a fuel injection port  200  and others may not. Any number of the vanelets  190  may be used. 
       FIG. 7  shows an alternative embodiment of a swozzle burner  210 . In this embodiment, the swozzle burner  210  may have a number of vanelets  220  that are positioned about the shroud  110  as opposed to the hub  100 . The vanelets  220  likewise may have an oval shape or any desired shape or desired size. The vanelets  220  also may have a fuel injection port therein if desired. Any number of the vanelets  220  may be used. Several of the vanelets  220  may be positioned on the shroud  110  while others may be positioned on the hub  100 . 
     The use of the vanelets  160 ,  190 ,  220  between the fuel vanes  120  helps to maintain mixture velocity as the fuel flow extends downstream along each vane  120 . Specifically, the velocity of the fuel/air mixture remains high in the turning portion of each of the vanes  120  as the vanes  120  taper towards the downstream end  124 . The vanelets  160 ,  190 ,  220  thus allow a reduction in the swirl and an increase in axial velocity of the mixture. This maintained, predetermined velocity permits a reduction in the swirl along the main vanes  120  without creating an expansion zone or a low velocity zone adjacent to the main vanes  120  until the flow is further downstream. The vanelets  160 ,  190 ,  220  also may provide sequestration by preventing interaction between the fuel injection ports  170  from opposing vanes  120 . The flow sequestration also may improve the flame holding margin. The vanelets  160 ,  190 ,  220  also may function as a quenching surface. 
     The use of the vanelets  160 ,  190 ,  220  with the fuel injection ports  170 ,  200  also provides secondary fuel injection points such that the fuel flow from the main fuel injection ports  130  of the fuel vanes  120  may be reduced. The size of the fuel injection ports  130  also may be reduced. Such a reduction of the main flow may improve the flame holding margin. 
     As described above, higher reactivity fuels, such as high hydrogen syngas, usually are burned in a diffusion mode instead of premixed in the swozzle assembly  90 . By providing for a higher axial velocity of the fuel flow, the vanelets  160 ,  190 ,  220  may permit premixing of these higher reactivity fuels while maintaining reduced nitrogen oxide (NO x ) emissions. The need for a diluent flow also may be reduced. The vanelets  160 ,  190 ,  220  thus may improve the fuel holding margins for higher reactivity fuels by allowing a higher axial velocity for a given pressure drop. 
     The fuel injection ports  170 ,  200  of the vanelets  160 ,  190 ,  220  may be used to inject alternative fuels so as to provide greater fuel flexibility. The fuel injection ports  170 ,  200  of the vanelets  160 ,  190 ,  220  also may be used to inject diluent, inert gases, or other types of fluids. 
     The use of the fuel injection ports  170 ,  200  of the vanelets  160 ,  190 ,  220  thus permits a reduced fuel flow through the main vanes  120  and/or permits a reduction in the size of the fuel injection ports  130 . The fuel injection ports  170 ,  200  of the vanelets  160 ,  190 ,  220  further provide fuel flexibility for fuels outside of the Modified Wobbe index range of the main fuel injector ports  130  by allowing premixing of other fuels so as to keep NO x  emissions low. 
     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.