Abstract:
The present application provides a liner for a combustor. The combustor liner may include a mouth, a passage for a flow of fuel, a passage for a flow of air, a first zone for mixing the flow of fuel and the flow of air, and the first zone having a constant diameter. The combustor liner may have at least one transition zone with first and second side walls angled substantially in the same direction, and an off center exit. This configuration will provide a more stable flow when exiting the combustor liner.

Description:
TECHNICAL FIELD 
     The present application relates generally to gas turbine engines and more particularly relates to a combustor liner or other type of passage with an off center throat and exit. 
     BACKGROUND OF THE INVENTION 
     Modern gas turbine engines generally must operate under strict emissions guidelines, particularly with respect to nitrogen oxides (NO x ). As such, gas turbine engine design must operate at high efficiency without producing undesirable air emissions. Many modern gas turbine engines thus use a very lean, premixed flame for low NO x  combustion. 
     One way to limit turbine emissions is to ensure good mixing of the fuel and the air in the combustor. Proper mixing may involve mixing flow manipulation using dilution tuning or similar methods. Tuning a combustor in the field, however, may be difficult and time consuming. Moreover, the need to tune properly a combustor also may influence the time required for initial commissioning and/or cause other types of delays. 
     There is thus a desire for an improved combustor and other types of turbine components that promote good mixing of both fuel and air while providing high overall efficiency with limited emissions. Preferably the combustor or the other components may be used with new and existing equipment. 
     SUMMARY OF THE INVENTION 
     The present application thus provides for a liner for a combustor. The combustor liner may include a mouth, one or more angled transition zones, and an off center exit. 
     The present application also provides for a method of mixing fuel and air in a combustor. The method may include the steps of flowing the fuel and the air into a combustor liner, flowing the fuel and the air through one or more angled transition zones, and flowing the fuel and the air through an off center throat. 
     The present application also provides for a gas turbine. The gas turbine may include a passage for a flow of fuel, a passage for a flow of air, a first zone for mixing the flow of fuel and the flow of air, one or more angled transition zones down stream of the first zone, and an off center exit down stream of the one or more angled transition zones. 
     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 side cross-section view of a combustor that may be used with the gas turbine engine of  FIG. 1 . 
         FIG. 3  is a perspective view of a combustor liner as may be described herein. 
         FIG. 4  is a perspective view of an alternative combustor liner as may be 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 the combustor  30 . The combustor  30  mixes the compressed flow of air with a flow of fuel and ignites the mixture. The hot combustion gases are in turn delivered 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. 
       FIG. 2  shows an example of a combustor  100  as may be used herein. In this example, the combustor  100  may be a Model 6B or Model 7EA of the DLN-1 (Dry Low NO x ) Combustor System offered by General Electric Company of Schenectady, N.Y. The concepts described herein, however, may be applicable to any type of combustor and also to many other types of turbine related components and other types of pathways. 
     Generally described, the combustor  100  may include an end cover assembly  110 . The end cover assembly  110  may include a number of fuel manifolds  120 . The fuel manifolds  120  may be in communication with a fuel nozzle assembly  130 . The fuel nozzle assembly  130  may support both diffusion and premixed combustion. Compressed air may be delivered to the combustor  100  by the compressor  20  via an air passage  140 . The air passage  140  may be defined by a combustor flow sleeve  150  and a combustor liner  160 . Many other designs and turbine configurations also may be used herein. 
     The fuel flows and the air flows may meet about the fuel nozzle assembly  130  and may be ignited within the combustion liner  160 . The combustor liner  160  may include a mixing zone  170  and a combustion zone  180 . The combustor liner  160  extends into a transition piece  190  that is adjacent to the turbine  40 . As is shown, the existing combustor liner designs  160  are essentially concentric in shape with a horizontal centerline extending uniformly therethrough. At least a portion of the flow path, however, comes into contact with the curved transition piece  190 . This concentric shape of the liner  160 , when combined with the curve of the transition piece  190 , thus may create a somewhat restrictive flow path therethrough. 
       FIG. 3  shows a combustor liner  200  as may be described herein. Instead of the combustion liner  160  with the mixing zone  170  and the combustion zone  180  merging into the transition piece  190  as is described above, the combustion liner  200  may be a unified element. The combustor liner  200  may include a mouth  205 , a combustion zone  210 , a number of angled transition zones  220 , at least one straight transition zone  230 , and an off center throat  240  with an off center exit  245 . As is shown, the combustor liner  200  has an essentially flat first side  250  and with the angle transitions zones  220  positioned about a stepped second side  260 . As a result of this shape, the flow path through the liner  200  is off center as compared to the entrance of the mouth  205 . Although the flow path takes a small dip in each of the angled transition zones  220 , the flow path is actually less restrictive therethrough. Any number of angled transition zones  220  may be used. 
     The off center throat  240  and the exit  245  of the liner  200  thus provides a shape similar to that of a Forstman funnel concept. A Forstman funnel is a funnel with the exit mouth being off center from the inlet. Liquid flowing through a funnel tends to swirl and form a whirlpool. As a result, centrifugal forces move the liquid away from the drain hole thus reducing the funnel capacity. The asymmetric shape of the Forstman funnel, however, reduces the rotation speed of the liquid in the whirlpool such that the funnel capacity may be increased. Such a design may flow about fifty percent (50%) to about seventy percent (70%) more than a conventional funnel. 
     Applying this concept to a combustor  100 , the design provides a more stable flow exiting the combustor  100  as compared to conventional cylindrically shaped components. Increased flow through the combustor  100  thus may allow for more complete airflow mixing. Likewise, the combustion zone  210  is lengthened by eliminating the curved transition piece  190 . Improved mixing thus should result. More uniform flow and better mixing also should promote more complete combustion and hence lower emissions. Likewise, more even exhaust temperatures should result. The design should increase flow, cooling, and/or the exhaust profile by making the flow path therethrough less restrictive. 
       FIG. 4  shows an alternative embodiment of a combustor liner  300  as is described herein. As described above, the combustor liner  300  includes a mouth  305 , a combustion zone  310 , a number of angled transition zones  320 , one or more straight transition zones  330 , and an off center throat  340  with an off center exit  345 . In this embodiment, however, instead of the flat first side  250 , the combustor liner  300  includes a stepped first side  350  that matches a stepped second side  360 . As a result, the flow path therethrough is even more off center as compared to the combustor liner  200  described above. 
     Although the Forstman funnel concept described herein has focused on the combustor liners  200 ,  300 , the concept also could be applied to flow sleeves, combustion cases, liner cap assemblies, secondary and primary fuel nozzles, fuel nozzle tips, end cover primary fuel nozzles, and in any place that flow goes through a staggered hole or is necked down. 
     It should be apparent that the foregoing relates only to the preferred 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.