Abstract:
A system includes a compressor that compresses incoming airflow, and a combustor assembly mixing the compressed incoming airflow with fuel and combusting the air and fuel mixture in a combustion zone. The combustor assembly includes a hot side downstream of the combustion zone and a cold side upstream of the combustion zone. The system also includes a turbine receiving products of combustion from the combustor. The combustor assembly includes a resonator positioned in the cold side of the combustor assembly in an annular passage between a flow sleeve and a casing of the combustor assembly.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a combustor assembly for a gas turbine and, more particularly, to a DLN combustor assembly including an acoustics resonator. 
         [0002]    Gas turbine systems typically include at least one gas turbine engine having a compressor, a combustor assembly, and a turbine. The combustor assembly may use dry, low NOx (DLN) combustion. In DLN combustion, fuel and air are pre-mixed prior to ignition, which lowers emissions. However, the lean pre-mixed combustion process is susceptible to flow disturbances and acoustic pressure waves. More particularly, flow disturbances and acoustic pressure waves could result in self-sustained pressure oscillations at various frequencies. These pressure oscillations may be referred to as combustion dynamics. Combustion dynamics can cause structural vibrations, wearing, and other performance degradations. 
         [0003]    It is desirable to suppress combustion dynamics in a DLN combustor below specified levels to maintain low emissions. For axial mode frequencies, which are typically below 500 Hz, combustion dynamics can be effectively controlled using acoustic resonators provided at optimal locations. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In an exemplary embodiment, a gas turbine combustor assembly includes a casing defining an external boundary of the combustor assembly, and a plurality fuel nozzles disposed in the casing and coupled with a fuel supply. A liner receives fuel and air from the fuel nozzles and defines a combustion zone, and a flow sleeve is disposed between the liner and the casing. The flow sleeve serves to distribute compressor discharge air to a head end of the combustor assembly and to cool the liner. A transition piece is coupled with the liner and delivers products of combustion to a turbine. A resonator is disposed adjacent the flow sleeve upstream of the transition piece. The resonator serves to attenuate combustion dynamics. 
         [0005]    In another exemplary embodiment, a system includes a compressor that compresses incoming airflow, a combustor assembly mixing the compressed incoming airflow with fuel and combusting the air and fuel mixture in a combustion zone, and a turbine receiving products of combustion from the combustor. The combustor assembly includes the noted casing, fuel nozzles, liner, flow sleeve, transition piece and resonator. 
         [0006]    In yet another exemplary embodiment, a system includes a compressor that compresses incoming airflow, and a combustor assembly mixing the compressed incoming airflow with fuel and combusting the air and fuel mixture in a combustion zone. The combustor assembly includes a hot side downstream of the combustion zone and a cold side upstream of the combustion zone. The system also includes a turbine receiving products of combustion from the combustor. The combustor assembly includes a resonator positioned in the cold side of the combustor assembly in an annular passage between a flow sleeve and a casing of the combustor assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a block diagram of an exemplary gas turbine system; 
           [0008]      FIG. 2  is a schematic diagram of a combustor assembly; 
           [0009]      FIG. 3  is a cross-sectional end view of the combustor shown in  FIG. 2 ; 
           [0010]      FIG. 4  is a schematic illustration showing the components of the resonator; and 
           [0011]      FIG. 5  is a schematic illustration with the resonator in an alternative embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    As described above, gas turbine systems include combustor assemblies which may use a DLN or other combustion process that is susceptible to flow disturbances and/or acoustic pressure waves. Specifically, the combustion dynamics of the combustor assembly can result in self-sustained pressure oscillations that may cause structural vibrations, wearing, mechanical fatigue, thermal fatigue, and other performance degradations in the combustor assembly. One technique to mitigate combustion dynamics is the use of a resonator, such as a Helmholtz resonator. Specifically, a Helmholtz resonator is a damping mechanism that includes several narrow tubes, necks, or other passages connected to a large volume. The resonator operates to attenuate and absorb the combustion tones produced by the combustor assembly. The depth of the necks or passages and the size of the large volume enclosed by the resonator may be related to the frequency of the acoustic waves for which the resonator is effective. 
         [0013]      FIG. 1  is a block diagram of an embodiment of a gas turbine system  10 . The gas turbine system  10  includes a compressor  12 , combustor assemblies  14 , and a turbine  16 . In the following discussion, reference may be made to an axial direction or axis  42 , a radial direction or axis  44 , and a circumferential direction or axis  46  of the combustor  14 . The combustor assemblies  14  include fuel nozzles  18  which route a liquid fuel and/or gas fuel, such as natural gas or syngas, into the combustor assemblies  14 . As illustrated, each combustor assembly  14  may have multiple fuel nozzles  18 . More specifically, the combustor assemblies  14  may each include a primary fuel injection system having primary fuel nozzles  20  and a secondary fuel injection system having secondary fuel nozzles  22 . Fuel nozzles can have multiple circuits, e.g., a total of six fuel nozzles, wherein one of them is independently fueled, a group of two fuel nozzles may have an independent fuel circuit, and a group of three fuel nozzles may have another independent circuit. Regardless of the arrangement and grouping of fuel nozzles, the combustor assembly includes multiple independent fuel circuits. 
         [0014]    The combustor assemblies  14  illustrated in  FIG. 1  ignite and combust an air-fuel mixture, and then pass hot pressurized combustion gasses  24  (e.g., exhaust) into the turbine  16 . Turbine blades are coupled to a common shaft  26 , which is also coupled to several other components throughout the turbine system  10 . As the combustion gases  24  pass through the turbine blades in the turbine  16 , the turbine  16  is driven into rotation, which causes the shaft  26  to rotate. Eventually, the combustion gases  24  exit the turbine system  10  via an exhaust outlet  28 . Further, the shaft  26  may be coupled to a load  30 , which is powered via rotation of the shaft  26 . For example, the load  30  may be any suitable device that may generate power via the rotational output of the turbine system  10 , such as a power generation plant or an external mechanical load. For instance, the load  30  may include an electrical generator, a propeller of an airplane, and so forth. 
         [0015]    In an embodiment of the turbine system  10 , compressor blades are included as components of the compressor  12 . The blades within the compressor  12  are also coupled to the shaft  26 , and will rotate as the shaft  26  is driven to rotate by the turbine  16 , as described above. The rotation of the blades within the compressor  12  compresses air from an air intake  32  into pressurized air  34 . The pressurized air  34  is then fed into the fuel nozzles  18  of the combustor assemblies  14 . The fuel nozzles  18  mix the pressurized air  34  and fuel to produce a suitable mixture ratio for combustion (e.g., a combustion that causes the fuel to more completely burn) so as not to waste fuel or cause excess emissions. 
         [0016]      FIG. 2  is a schematic diagram of one of the combustor assemblies  14  of  FIG. 1 , illustrating an embodiment of a resonator  40  disposed in cooperation with the combustor assembly  14 . As described above, the compressor  12  receives air from an air intake  32 , compresses the air, and produces a flow of pressurized air  34  for use in the combustion process within the combustor  14 . As shown in the illustrated embodiment, the pressurized air  34  is received by a compressor discharge  48  that is operatively coupled to the combustor assembly  14 . As illustrated by arrows  52 , the pressurized air  34  flows from the compressor discharge  48  towards a head end  54  of the combustor  14 . More specifically, the pressurized air  34  flows through an annulus  56  between a liner  58  and a flow sleeve  60  of the combustor assembly  14  to reach the head end  54 . A casing serves as an external boundary or housing of the combustor assembly. 
         [0017]    In certain embodiments, the head end  54  includes plates  61  and  62  that may support the fuel nozzles  20  depicted in  FIG. 1 . In the embodiment illustrated in  FIG. 2 , a fuel supply  64  provides fuel  66  to the fuel nozzles  20 . Additionally, the fuel nozzles  20  receive the pressurized air  34  from the annulus  56  of the combustor assembly  14 . The fuel nozzles  20  combine the pressurized air  34  with the fuel  66  provided by the fuel supply  64  to form an air/fuel mixture. The air/fuel mixture is ignited and combusted in a combustion zone  68  of the combustor assembly  14  to form combustion gases (e.g., exhaust). The combustion gases flow in a direction  70  toward a transition piece  72  of the combustor assembly  14 . The combustion gases pass through the transition piece  72 , as indicated by arrow  74 , toward the turbine  16 , where the combustion gases drive the rotation of the blades within the turbine  16 . 
         [0018]    The combustor assembly  14  also includes the resonator  40  disposed between the flow sleeve  60  and the casing  59  adjacent an inlet of the flow sleeve  60 . As described above, the combustion process produces a variety of pressure waves, acoustic waves, and other oscillations referred to as combustion dynamics. Combustion dynamics may cause performance degradation, structural stresses, and mechanical or thermal fatigue in the combustor assembly  14 . Therefore, combustor assemblies  14  may include the resonator  40 , e.g., a Helmholtz resonator, to help mitigate the effects of combustion dynamics in the combustor assembly  14 . 
         [0019]    As shown in  FIG. 2 , the resonator  40  is mounted on the flow sleeve on a cold side of the combustor assembly.  FIG. 3  is a cross section along lines  3 - 3  in  FIG. 2 . As shown, the resonator  40  is preferably positioned in an annular passage between the flow sleeve and the casing  59 . The resonator  40  is preferably attached to the flow sleeve  60 . As shown in  FIG. 4 , the resonator  40  includes a volume  78  containing a plurality of tubes  76  in fluid communication with air flow between the liner  58  and the flow sleeve  60 . The tubes  76  extend into an annular passage within the volume  78  between the flow sleeve  60  and the casing  59 .  FIG. 5  shows an alternative arrangement with the resonator  40  positioned immediately downstream of an axial injection flow sleeve. By locating the resonator  40  in this manner, high amplitude acoustic pressure can be mitigated effectively. 
         [0020]    In  FIG. 4 , P′ IN identifies acoustic pressure waves traveling from the combustor head end, and P′ OUT identifies acoustic pressure waves traveling from the transition piece. 
         [0021]    The resonator  40  on the flow sleeve  60  can be tuned for a targeted frequency range. Additionally, since the resonator  40  may be secured to the flow sleeve  60 , it is easily replaced. 
         [0022]    The resonator of the described embodiments serves to suppress/attenuate combustion-generated acoustics. As a consequence, operability and durability of a DLN combustor can be extended. 
         [0023]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.