Abstract:
Embodiments of the present application can provide systems and methods for dampening combustor dynamics. According to one embodiment, the system may include a micromixer. The system may also include at least one annular resonator disposed within the micromixer adjacent to a cap face plate or an impingement plate of the micromixer. The at least one annular resonator may include a first side including a number of holes forming a cold side hole pattern, a second side including a number of holes forming a hot side hole pattern, and a cavity substantially defined by the first side and the second side.

Description:
FIELD OF THE INVENTION 
     Embodiments of the present application relate generally to gas turbine engines and more particularly to systems and methods for dampening combustor dynamics. 
     BACKGROUND OF THE INVENTION 
     Gas turbines are generally operated at either a base load or at a part load. The load operation partly determines the amount of fuel consumption. Fluctuations in the rate of fuel consumption may create combustor dynamics, which may extend throughout the combustor. When the gas turbine is at base load, the peaks of the combustor dynamics are generally relatively low. However, during a transient mode switching or part load operation, the peaks of combustor dynamics may be high. Furthermore, screech dynamics, generally considered as one of the most destructive forms of dynamics, may get to higher levels during a part load operation. Accordingly, there is a need for systems and methods for dampening combustor dynamics. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Some or all of the above needs and/or problems may be addressed by certain embodiments of the present application. According to one embodiment, there is disclosed a system for dampening combustor dynamics. The system includes a micromixer. The system also includes at least one annular resonator disposed within the micromixer adjacent to a cap face plate of the micromixer. The annular resonator includes a first side having a number of holes forming a cold side hole pattern, a second side having a number of holes forming a hot side hole pattern, and a cavity substantially defined by the first side and the second side. 
     According to another embodiment, there is disclosed another system for dampening combustor dynamics. The system includes a micromixer. The system also includes at least one annular resonator disposed within the micromixer adjacent to an impingment plate of the micromixer. The annular resonator includes a first side having a number of holes forming a cold side hole pattern, a second side having a number of holes forming a hot side hole pattern, and a cavity substantially defined by the first side and the second side. 
     Further, according to another embodiment, there is disclosed a method for dampening combustor dynamics. The method includes positioning at least one annular resonator within a micromixer. The annular resonator includes a first side having a number of holes forming a cold side hole pattern, a second side having a number of holes forming a hot side hole pattern, and a cavity substantially defined by the first side and the second side. 
     Other embodiments, aspects, and features of the invention will become apparent to those skilled in the art from the following detailed description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIG. 1  is a schematic of an example diagram of a gas turbine engine with a compressor, a combustor, and a turbine, according to an embodiment. 
         FIG. 2  is a schematic of an example diagram of a micromixer, according to an embodiment. 
         FIG. 3  is a schematic of an example diagram of an annular resonator, according to an embodiment. 
         FIG. 4  is a schematic of an example diagram of an annular resonator, according to an embodiment. 
         FIG. 5  is a schematic of an example diagram of an annular resonator, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Illustrative embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. The present application may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like numbers refer to like elements throughout. 
     Illustrative embodiments are directed to, among other things, micromixers for a combustor.  FIG. 1  shows a schematic view of a gas turbine engine  10  as may be used herein. As is known, the gas turbine engine  10  may include a compressor  15 . The compressor  15  compresses an incoming flow of air  20 . The compressor  15  delivers the compressed flow of air  20  to a combustor  25 . The combustor  25  mixes the compressed flow of air  20  with a pressurized flow of fuel  30  and ignites the mixture to create a flow of combustion gases  35 . Although only a single combustor  25  is shown, the gas turbine engine  10  may include any number of combustors  25 . The flow of combustion gases  35  is in turn delivered to a turbine  40 . The flow of combustion gases  35  drives the turbine  40  so as to produce mechanical work. The mechanical work produced in the turbine  40  drives the compressor  15  via a shaft  45  and an external load  50  such as an electrical generator and the like. 
     The gas turbine engine  10  may use natural gas, various types of syngas, and/or other types of fuels. The gas turbine engine  10  may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, N.Y., including, but not limited to, those such as a 7 or a 9 series heavy duty gas turbine engine and the like. The gas turbine engine  10  may have different configurations and may use other types of components. 
     Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together. 
       FIG. 2  depict a component of the combustor  25  in  FIG. 1 ; specifically, a micromixer  100  or a portion thereof. The micromixer  100  may include a fuel plenum  104 , an air intake  106 , and numerous mixing tubes  108 . In one embodiment, a fuel line  102  supplies fuel to the fuel plenum  104 . The fuel exits the fuel plenum  104  and enters the mixing tubes  108  via one or more holes  109  in the mixing tubes  108 . Air is directed into the mixing tubes  108  through the air intake  106  and mixes with the fuel to create an air/fuel mixture or working fluid. The air/fuel mixture exits the mixing tubes  108  and enters a combustion chamber  111 . The micromixer  100  may also include a central fuel nozzle  112  for supplying fuel directly to the combustion chamber  111 . 
     Still referring to  FIG. 2 , the mixing tubes  108  may include an end cap assembly  114  encompassing the mixing tubes  108  downstream of the fuel plenum  104 . The end cap assembly  114  may include a cap face plate  116  disposed near the downstream end of the mixing tubes  108 . A cooling air hole  118  may be located in the end cap assembly  114 . The cooling air hole  118  directs air from the compressor into the end cap assembly  114  about the interstitial space between the mixing tubes  108 . The diverted air cools the mixing tubes  108 . The end cap assembly  114  may also include an impingement plate  120  disposed near the cap face plate  116 . The impingement plate  120  impinges the cooling air flow in the end cap assembly  114 . 
     One or more annular resonators  122  may be located within the end cap assembly  114  about the centerline of the micromixer  100 . The annular resonators  122  may be attached to the cap face plate  116  and/or the impingement plate  120  within the end cap assembly  114 . 
     As collectively depicted in  FIGS. 3-5 , the annular resonators  122  may each include a first side  124 , a cavity  126 , and a second side  128 . The first side  124 , the cavity  126 , and second side  128  are joined to form the resonator  122 . In certain illustrative embodiments, the annular resonator  122  may be disposed about the center fuel nozzle  112 . In other illustrative embodiments, the annular resonator  122  may be disposed between co-annular bundles of mixing tubes  108 . 
     The first side  124  may include a first side facing surface  130  and a cold side hole pattern  132 . The first side  124  may form the upstream side of the annular resonator  122 . The first side  124  may have a number of holes forming a cold side hole pattern  132 . The cold side hole pattern  132  may be formed through a first side facing surface  130 . The cold side hole pattern  132  allows for cooling air to enter the annular resonator  122 . The cooling air cools the second side  128  and may prevent the working fluid from back flowing into the resonator  122 . 
     The number of holes in the cold side hole pattern  132  may be configured and oriented such that cooling air flows through each hole on the cold side hole pattern  132 . This may allow for the second side  128  to receive sufficient cooling air, which eventually effuses out of the second side facing surface  134 . 
     The cavity  126  may be defined as the annular volume between the first side facing surface  130  and the second side facing surface  134 . Typically, the cavity  126  is a closed volume. The fluid inertia of the working fluid passing through the hot side hole pattern  136  is reacted by the volumetric stiffness of the cavity  126 , producing a resonance in the velocity of the working fluid through the hot side hole pattern  136 . This flow oscillation generally has a well-defined natural frequency and provides an effective mechanism for absorbing acoustic energy. Therefore, the cavity  126  receives and absorbs the acoustic energy from the second side  128 , dampening the screech dynamics. 
     The second side  128  may include a second side facing surface  134  and a hot side hole pattern  136 . The second side  128  may form the downstream side of the resonator  122 . The second side  128  receives portion of the working fluid. The working fluid is directed through the second side  128  and flows through to the cavity  126 . The second side  128  may have a number of holes, which forms a hot side hole pattern  136 . The hot side hole pattern  136  may be formed through a second side facing surface  134 . 
     The thickness of the second side  128  generally functions as the throat length of the annular resonator  122 . The throat length typically serves as an important parameter for configuring a resonator to dampening dynamics of a specific frequency. An embodiment of the present invention serves to dampening screech dynamics, which may occur at frequencies of 1000 Hz or higher. 
     The amount of holes in the hot side hole pattern  136  is configured and oriented such that a jet of working fluid that flows through each hole on the cold side hole pattern  132  is directed in a such a way that the jet impinges on the second side facing surface  134 . In an embodiment, the number of holes forming the cold side hole pattern  132  may be less than the number of holes forming the hot side hole pattern  136 . Furthermore, in an embodiment, the size of each hole among the cold side hole pattern  132  may be smaller than the size of each hole among the hot side hole pattern  136 . The aforementioned features may ensure that adequate directing of the working fluid and damping of the combustor dynamics occurs. 
     In use, the resonator  122  may be tuned to remove a specific combustion dynamic frequency, i.e., the resonator  122  may be configured to remove a specific combustion dynamic frequency by varying the size and number of holes in the resonator. For example, combustion dynamic frequencies may range from about 1000 hz to about 4000 hz; furthermore, combustion dynamic frequencies may occur from any frequencies greater than about 1000 hz. 
     Co-assigned and co-pending patent application Ser. No. 11/732,143 to Bandaru et al., filed on Apr. 3, 2007, having a Pub. No. 2008/0245337, includes a resonator device and is hereby incorporated by reference. 
     The annular resonator  122  has been described in relation to the micromixer  100  depicted in  FIG. 2 . It will be appreciated, however, that the annular resonator may be disposed about the center line of any micromixer configuration, including, but not limited to, the segmented micromixer described in co-pending U.S. patent application Ser. No. 13/423,894, filed Mar. 19, 2012, which is hereby incorporated by reference. For example, the annular resonator described above may be disposed within the end cap assembly about the base nozzle structure of co-pending U.S. patent application Ser. No. 13/423,894. 
     Although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments.