Abstract:
A method enables a gas turbine engine to be assembled. The method includes providing a combustor including a liner that defines a combustion chamber therein, and coupling a casing within the gas turbine engine to extend circumferentially around the combustor liner, wherein the casing includes an inlet and a scroll duct that is coupled in flow communication to the inlet and extends at least partially circumferentially around the liner. The method also includes coupling the inlet in flow communication with a feed air source.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [[0001]]     The U.S. Government may have certain rights in this invention pursuant to contract number DAAE07-00-cc-N086. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates generally to gas turbine engines, more particularly to methods and apparatus for supplying feed air to turbine combustors.  
         [0003]     Known turbine engines include a compressor for compressing air which is suitably mixed with a fuel and channeled to an annular combustor wherein the mixture is ignited for generating hot combustion gases. The gases are channeled to at least one turbine, which extracts energy from the combustion gases for powering the compressor, as well as for producing useful work, such as propelling a vehicle.  
         [0004]     In at least some known turbine engines, compressor discharge air is preheated in a separate heat exchanger before being routed to the combustor via a duct. More specifically, the feed air is routed through to the combustor through a single feed point inlet. Although all of the air entering the inlet is channeled to the combustor, because the feed air may not be supplied uniformly to the annular combustor, unnecessary pressure losses and mal-distribution of supply air to the combustor. As a result, engine performance may be reduced and circumferential temperature gradients may be induced around the casing surrounding the combustor. Over time, such gradients may cause non-circumferential thermal growth which may adversely impact turbomachinery blade tip clearances and/or reduce engine performance. Furthermore, continued operation with such thermal gradients may reduce the useful life of the combustor.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0005]     In one aspect, a method for assembling a gas turbine engine is provided. The method comprises providing a combustor including a liner that defines a combustion chamber therein, and coupling a casing within the gas turbine engine to extend circumferentially around the combustor liner, wherein the casing includes an inlet and a scroll duct that is coupled in flow communication to the inlet and extends at least partially circumferentially around the liner. The method also comprises coupling the inlet in flow communication with a feed air source.  
         [0006]     In a further aspect of the invention, a combustor for a gas turbine engine is provided. The combustor includes a liner that defines a combustion chamber therein, and a casing that extends circumferentially around the combustor liner. The casing includes an inlet coupled in flow communication with a feed air source, and a scroll duct coupled in flow communication with the inlet. The scroll duct extends at least partially circumferentially around the liner.  
         [0007]     In another aspect, a gas turbine engine is provided. The gas turbine engine includes a compressor, and a combustor upstream from the compressor. The combustor includes a liner that defines a combustion chamber therein, and a casing that extends circumferentially around the combustor liner. The casing includes an inlet coupled in flow communication with the compressor, and a scroll duct that is coupled in flow communication with the inlet and extends at least partially circumferentially around the liner. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a schematic of a gas turbine engine.  
         [0009]      FIG. 2  is a cross-sectional illustration of a portion of the gas turbine engine shown in  FIG. 1 ;  
         [0010]      FIG. 3  is a perspective view of a combustor casing shown in  FIG. 2  and viewed from downstream;  
         [0011]      FIG. 4  is a partial perspective view of the combustor casing shown in  FIG. 3  and taken along line  4 - 4 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0012]      FIG. 1  is a schematic illustration of a gas turbine engine  10  including a low pressure compressor  12 , a high pressure compressor  14 , and a combustor  16 . Engine  10  also includes a high pressure turbine  18  and a low pressure turbine  20 . Compressor  12  and turbine  20  are coupled by a first shaft  24 , and compressor  14  and turbine  18  are coupled by a second shaft  26 . In one embodiment, the gas turbine engine is an LV100 available from General Electric Company, Cincinnati, Ohio. In the exemplary embodiment, gas turbine engine  10  is a recouperated engine.  
         [0013]     In operation, air flows through low pressure compressor  12  and compressed air is supplied from low pressure compressor  12  to high pressure compressor  14 . The highly compressed air is delivered to combustor  16 . Airflow from combustor  16  drives turbines  18  and  20  before exiting gas turbine engine  10 .  
         [0014]      FIG. 2  is a cross-sectional illustration of a portion of gas turbine engine  10  including combustor  16  and turbine  18 .  FIG. 3  is a perspective view of a combustor casing  40  that extends circumferentially around combustor  16 .  FIG. 4  is a partial perspective view of combustor casing  40  taken along line  4 - 4  shown in  FIG. 3 . Combustor  16  is annular includes a liner assembly  43  that includes an inner liner  44  and an outer liner  46  that each extend downstream from an upstream end  50  of combustor  16  to a turbine nozzle assembly  52 . Inner liner  44  is spaced radially inwardly from outer liner  46  such that a combustion chamber  54  is defined therebetween. Combustor  16  is positioned radially inwardly from combustor casing  40 .  
         [0015]     Combustor casing  40  is annular and extends circumferentially around combustor  16 . Casing  40  includes an air delivery portion  60  and a mounting portion  62  that extends downstream from air delivery portion  60 . In the exemplary embodiment, air delivery portion  60  is formed integrally with mounting portion  62 . Mounting portion  62  is substantially cylindrical and extends downstream from air delivery portion  60  to a mounting flange  64 . Flange  64  is annular and includes a plurality of circumferentially-spaced openings  66  that are sized to receive a plurality of fasteners (not shown) therethrough for securing a downstream end  68  of casing  40  within gas turbine engine  10 . Mounting portion  62  also includes a plurality of openings  70  extending therethrough between casing portion  60  and flange  64 . Openings  70  are each sized to receive a fastener  74  therethrough for securing engine components, such as a turbine frame  76 , to casing  40 . Openings  70  also enable engine services to extend through casing  40 .  
         [0016]     Casing air delivery portion  60  includes an annular shield portion  82 , a recouperator air inlet  84 , and a scroll duct  86  extending therebetween. Annular shield portion  82  defines a bluff upstream end  88  of casing  40  and includes a mounting flange  90  that is radially inward of, and downstream from, upstream end  88 . Mounting flange  90  includes a plurality of circumferentially-spaced openings  92  that are each sized to receive a fastener  94  therethrough for securing casing upstream end  88  within gas turbine engine  10 . Shield portion  82  also includes a plurality of openings  96  that extend therethrough between upstream end  88  and scroll duct  86 . Openings  96  permit passage of engine components and/or engine services  100  therethrough. For example, in the exemplary embodiment, a plurality of fuel injectors  102  extend through openings  96 .  
         [0017]     Air inlet  84  is positioned circumferentially at approximately a one-o&#39;clock position when viewed from upstream. Air inlet  84  includes a substantially cylindrical duct portion  110  that extends downstream from a downstream surface  112  of scroll duct  86 . Air inlet  84  is coupled by duct portion  110  in flow communication to a discharge from compressor  14  (shown in  FIG. 1 ). Air inlet duct portion  110  has an inner diameter D 1  measured with respect to an inner surface  112  of duct portion  110 .  
         [0018]     Scroll duct  86  is hollow and extends in flow communication from air inlet  84  such that all fluid flow discharged from inlet  84  enters scroll duct  86 . According, immediately adjacent inlet  84 , scroll duct  86  has an inlet cross-sectional area  114  that is defined with an inner diameter D 1 . In the exemplary embodiment, scroll duct  86  includes a left-hand scroll arm  120  and a right-hand scroll arm  122  that is a mirror image of arm  120 . Arms  120  and  122  are each arcuate and extend approximately 180° from inlet  84 . In an alternative embodiment, scroll duct  86  includes only one arm  120  or  122  that extends slightly less than 360° from inlet  84  such that the arm facilitates distributing fluid flow as described in more detail below.  
         [0019]     Each scroll duct arm  120  and  122  has an inlet end  130  that is adjacent inlet  84  and a discharge end  132  that is opposite inlet end  130  and is approximately offset 180° from inlet  84 . Scroll duct arms  120  and  122  are coupled together in flow communication, and each arm  120  and  122  includes a plurality of openings  134  that extend therethrough. More specifically, openings  134  are formed only along an inner diameter of scroll duct arms  120  and  122  and thus, extend only through a radially inner surface  136  of each scroll duct arm  120  and  122 , and are thus, in flow communication with a fluid passageway  140  defined within scroll duct  84 .  
         [0020]     In the exemplary embodiment, a splitter  200  is positioned between air inlet  84  and scroll duct  86 . In an alternative embodiment, casing  40  does not include splitter  200 . Splitter  200  is contoured to channel fluid flow discharged from air inlet  84 . More specifically, in the exemplary embodiment, splitter  200  is formed integrally with casing  40  and channels a portion of fluid flow discharged from inlet  84  into arm  120 , and the remaining fluid flow into arm  122 . In the exemplary embodiment, splitter  200  channels approximately 50% of the total discharged fluid flow into each arm  120  and  122 . Accordingly, approximately 50% of the fluid flowing through scroll duct  86  flows in a clockwise direction, and approximately 50% of the fluid flowing through scroll duct  86  flows in a counter-clockwise direction.  
         [0021]     Each scroll duct arm  120  and  122  has a variable cross-sectional profile extending between each respective inlet end  130  and discharge end  132 . Scroll duct  86  has an inner diameter D 2  at discharge end  132  that is smaller than inlet inner diameter D 1 . More specifically, scroll duct  86  has a variable cross-sectional area that diminishes from scroll duct inlet end  130  to duct discharge end  132 . Accordingly, a discharge cross-sectional area  204  defined by inner diameter D 2  is smaller than inlet cross-sectional area  87 .  
         [0022]     During operation, a portion of pressurized air discharged from compressor  14  is routed to combustor  16  for use as feed air. Specifically, the air is eventually channeled to combustor casing air delivery portion  60  through recouperator air inlet  84 . More specifically, in the exemplary embodiment, air discharged from inlet  84  contacts splitter  200  and approximately 50% of the fluid flow exiting inlet  84  is directed clockwise into scroll duct arm  122  and the remaining fluid flow is directed counter-clockwise into scroll duct arm  120 . Air flowing through scroll duct  86  is directed radially inwardly through duct openings  134  towards combustor liner assembly  43 . The combination of the decreasing cross-sectional flow area defined within scroll duct  86 , and the circumferential-spacing and size of openings  134  facilitates providing a substantially uniform flow towards combustor liner assembly  43 . More specifically, because openings  134  extend between scroll duct inlet and discharge ends  130  and  132 , respectively, openings  134  provide circumferential flow towards liner assembly  43 .  
         [0023]     In the exemplary embodiment, as a result of the decreasing cross-sectional flow area defined within scroll duct  86  and openings  134  all feed air flowing through scroll duct  86  is exhausted after traveling approximately 180° from inlet  84 . Because the feed air is supplied substantially uniformly around combustor liner assembly  43 , thermal gradients induced within liner assembly  43  and thermal growth distortion of liner assembly  43  is facilitated to be reduced. Furthermore, scroll duct  86  also facilitates improving combustion pattern factor, which results in improved combustor performance and/or extending a useful life of combustor  16 . In addition, because thermal growth distortion of liner assembly  43  is facilitated to be reduced, scroll duct  86  also enhances turbomachinery blade tip clearance control.  
         [0024]     The above-described combustor casing provides a cost-effective and reliable means for reducing thermal gradients induced withinthe combustor liner. More specifically, the casing directs feed air substantially uniformly and circumferentially towards the combustor liner. As a result, thermal growth distortion of the liner is facilitated to be reduced. Moreover, the combustor casing facilitates extending a useful life of the combustor in a cost-effective and reliable manner.  
         [0025]     An exemplary embodiment of a combustor casing is described above in detail. The casing illustrated is not limited to the specific embodiments described herein, but rather, components of each may be utilized independently and separately from other components described herein.  
         [0026]     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.