System and method for reducing modal coupling of combustion dynamics

Abstract

A system for reducing modal coupling of combustion dynamics includes a plurality of combustors, and at least one fuel injector in each of the plurality of combustors. The system also includes structure for dithering a combustion instability frequency in at least one combustor in the plurality of combustors. A method for reducing modal coupling of combustion dynamics includes flowing a compressed working fluid at a temperature to a plurality of combustors and flowing a fuel to at least one fuel injector in each of the plurality of combustors. The method further includes dithering at least one of the temperature of the compressed working fluid flowing to the plurality of combustors or the fuel flow to the at least one fuel injector in at least one combustor in the plurality of combustors.

What is claimed is: 
     
         1 . A system for reducing modal coupling of combustion dynamics, comprising:
 a. a plurality of combustors;   b. at least one fuel injector in each of the plurality of combustors; and   c. means for dithering a combustion instability frequency in at least one combustor in the plurality of combustors.   
     
     
         2 . The system as in  claim 1 , wherein the means for dithering the combustion instability frequency in at least one combustor in the plurality of combustors dithers a fuel flow to at least one fuel injector in at least one combustor in the plurality of combustors. 
     
     
         3 . The system as in  claim 1 , wherein the means for dithering the combustion instability frequency in at least one combustor in the plurality of combustors dithers a temperature of a fuel flow to at least one fuel injector in at least one combustor in the plurality of combustors. 
     
     
         4 . The system as in  claim 1 , wherein the means for dithering the combustion instability frequency in at least one combustor in the plurality of combustors dithers a Wobbe index of a fuel flow to at least one fuel injector in at least one combustor in the plurality of combustors. 
     
     
         5 . The system as in  claim 1 , wherein the means for dithering the combustion instability frequency in at least one combustor in the plurality of combustors comprises a processor configured to execute logic stored in a memory that causes the processor to dither at least one of a fuel flow, a temperature of the fuel flow, or a Wobbe index of the fuel flow to at least one fuel injector in at least one combustor in the plurality of combustors. 
     
     
         6 . The system as in  claim 1 , further comprising a compressor section upstream from the plurality of combustors configured to produce a compressed working fluid at a temperature and the means for dithering the combustion instability frequency in at least one combustor in the plurality of combustors dithers a temperature of a working fluid entering the compressor section. 
     
     
         7 . The system as in  claim 1 , further comprising a compressor section upstream from the plurality of combustors configured to produce a compressed working fluid at a temperature and the means for dithering the combustion instability frequency in at least one combustor in the plurality of combustors dithers a flow rate of a working fluid entering the compressor section. 
     
     
         8 . The system as in  claim 1 , further comprising a compressor section upstream from the plurality of combustors configured to produce a compressed working fluid at a temperature and the means for dithering the combustion instability frequency in at least one combustor in the plurality of combustors dithers a flow rate of the compressed working fluid recirculated through the compressor section. 
     
     
         9 . A gas turbine comprising:
 a. a compressor section configured to produce a compressed working fluid at a temperature;   b. a plurality of combustors downstream from the compressor section, wherein each combustor comprises a fuel injector;   c. a turbine section downstream from the plurality of combustors; and   d. means for dithering the temperature of the compressed working fluid produced by the compressor section.   
     
     
         10 . The gas turbine as in  claim 9 , wherein the means for dithering the temperature of the compressed working fluid produced by the compressor section dithers a temperature of a working fluid entering the compressor section. 
     
     
         11 . The gas turbine as in  claim 9 , wherein the means for dithering the temperature of the compressed working fluid produced by the compressor section dithers a flow rate of a working fluid entering the compressor section. 
     
     
         12 . The gas turbine as in  claim 9 , wherein the means for dithering the temperature of the compressed working fluid produced by the compressor section dithers a flow rate of the compressed working fluid recirculated through the compressor section. 
     
     
         13 . The gas turbine as in  claim 9 , wherein the means for dithering the temperature of the compressed working fluid produced by the compressor section comprises a processor configured to execute logic stored in a memory that causes the processor to dither at least one of a temperature of a working fluid entering the compressor section, a flow rate of the working fluid entering the compressor section, or a flow rate of the compressed working fluid recirculated through the compressor section. 
     
     
         14 . The gas turbine as in  claim 9 , further comprising means for dithering a fuel flow to at least one fuel injector in at least one combustor in the plurality of combustors. 
     
     
         15 . The gas turbine as in  claim 14 , wherein the means for dithering the fuel flow to at least one fuel injector in at least one combustor in the plurality of combustors dithers the fuel flow to each fuel injector in the plurality of combustors. 
     
     
         16 . A method for reducing modal coupling of combustion dynamics, comprising:
 a. flowing a compressed working fluid at a temperature to a plurality of combustors;   b. flowing a fuel to at least one fuel injector in each of the plurality of combustors; and   c. dithering at least one of the temperature of the compressed working fluid flowing to the plurality of combustors or the fuel flow to the at least one fuel injector in at least one combustor in the plurality of combustors.   
     
     
         17 . The method as in  claim 16 , further comprising dithering a temperature of the fuel flow to at least one fuel injector in at least one combustor in the plurality of combustors. 
     
     
         18 . The method as in  claim 16 , further comprising dithering a Wobbe index of the fuel flow to at least one fuel injector in at least one combustor in the plurality of combustors. 
     
     
         19 . The method as in  claim 16 , dithering a flow rate of the compressed working recirculated through a compressor. 
     
     
         20 . The method as in  claim 16 , further comprising compressing a working fluid to produce the compressed working fluid and dithering at least one of a temperature or flow rate of the working fluid.