Method of operating a multi-stage flamesheet combustor

Abstract

The present invention discloses a novel way of controlling a gas turbine engine to reduce emissions levels when demand for power from the gas turbine engine is reduced. The operating system provides a series of operating modes for a gas turbine combustor through which fuel is staged to gradually increase engine power, yet harmful emissions, such as carbon monoxide are kept within acceptable levels.

1 . A method of operating a gas turbine combustor comprising:
 supplying fuel to a pilot fuel nozzle of the gas turbine combustor;   igniting the fuel injected by the pilot fuel nozzle;   supplying fuel to a set of pilot tune stage injectors and the pilot fuel nozzle, the pilot tune stage injectors positioned radially outward of the pilot fuel nozzle;   supplying fuel to a first portion of a set of main fuel injectors, the pilot fuel nozzle and the pilot tune stage injectors;   igniting the fuel injected by the first portion of the set of main fuel injectors to form a main combustion flame;   supplying fuel to a second portion of the set of main fuel injectors, the first portion of the set of main injectors, the pilot fuel nozzle and the pilot tune stage injectors; and   igniting the fuel injected by the second portion of the set of main fuel injectors to enhance the main combustion flame.   
     
     
         2 . The method of  claim 1  further comprising modulating the fuel to the pilot fuel nozzle and/or the pilot tune stage injectors. 
     
     
         3 . The method of  claim 1 , wherein fuel is supplied only to the pilot fuel nozzle during lightoff of the gas turbine combustor and up to a full speed no load (FSNL) condition. 
     
     
         4 . The method of  claim 3 , wherein fuel is supplied to the pilot tune stage injectors from light-off to approximately a 10% load condition. 
     
     
         5 . The method of  claim 4 , wherein fuel is supplied to the first portion of the main injectors beginning at light-off to approximately the 10% load condition. 
     
     
         6 . The method of  claim 5 , wherein fuel is supplied to the second portion of the main fuel injectors beginning at light-off to approximately a 25% load condition. 
     
     
         7 . The method of  claim 1 , wherein the first portion of the set of main fuel injectors comprises an arc-like segment of fuel injectors spanning approximately 120 degrees and the second portion of the set of main fuel injectors comprises an arc-like segment of fuel injectors spanning approximately 240 degrees. 
     
     
         8 . A computerized method, implemented by a processing unit, for staging fuel in a gas turbine combustor where the gas turbine combustor has a pilot fuel nozzle, a set of pilot tune stage injectors for tuning the pilot fuel nozzle and a main set of fuel injectors, the method comprising:
 operating the combustor in a first mode in which fuel is injected by the pilot fuel nozzle;   operating the combustor in a second mode in which fuel is injected by the pilot fuel nozzle and the injectors for the pilot tune stage;   operating the combustor in a third mode in which fuel is injected by the pilot fuel nozzle, the injectors for the pilot tune stage, and a first portion of the main set of fuel injectors; and   operating the combustor in a fourth mode in which fuel is injected by the pilot fuel nozzle, the injectors for the pilot tune stage, the first portion of the main set of fuel injectors and a second portion of the main set of fuel injectors.   
     
     
         9 . The method of  claim 8 , wherein the first portion of the main set of fuel injectors extend across an arc-like span of approximately 120 degrees and the second portion of the main set of fuel injectors extend across an arc-like span of approximately 240 degrees. 
     
     
         10 . The method of  claim 8 , wherein the first mode provides a pilot flame to the gas turbine combustor. 
     
     
         11 . The method of  claim 10 , wherein fuel injected by the pilot tune stage provides an additional fuel source for modulating and supporting the pilot flame. 
     
     
         12 . The method of  claim 8 , wherein fuel injected by the third mode and fourth mode is injected in an axially upstream direction and undergoes a reversal of direction prior to ignition. 
     
     
         13 . The method of  claim 8 , wherein the fuel flow to the pilot fuel nozzle and the injectors of the pilot tune stage is adjustable after operating the combustor in the fourth mode. 
     
     
         14 . A method of improving turndown capability of a gas turbine combustor while controlling carbon monoxide production from the gas turbine combustor comprising:
 modulating fuel flow to both a first portion and a second portion of an annular array of main fuel injectors supporting a main combustion flame; and   modulating fuel flow to one or more fuel injectors in a core section of the gas turbine combustor.   
     
     
         15 . The method of  claim 14 , wherein modulating fuel flow to both a first portion and a second portion of an annular array of main injectors comprises increasing the fuel flow to both the first portion and second portion. 
     
     
         16 . The method of  claim 15 , wherein modulating fuel flow to one or more fuel injectors in a core section comprises decreasing the fuel flow to at least the pilot fuel nozzle. 
     
     
         17 . The method of  claim 16 , wherein a ratio of fuel flow to main fuel injectors compared to the fuel flow to at least the pilot nozzle increases while total fuel flow to the engine decreases. 
     
     
         18 . The method of  claim 14 , wherein the first portion comprises an annular array of main fuel injectors extending approximately 120 degrees and the second portion comprises an annular array of main fuel injectors extending approximately 240 degrees. 
     
     
         19 . The method of  claim 14 , wherein the core section of the gas turbine combustor comprises a pilot fuel nozzle and injectors of a pilot tune stage, where the pilot tune stage of fuel injectors provide a fuel flow to support the pilot flame. 
     
     
         20 . A method of operating a gas turbine combustor comprising:
 supplying fuel to a pilot fuel nozzle and a set of pilot tune stage injectors of the gas turbine combustor;   igniting the fuel injected by the pilot fuel nozzle and the pilot tune stage injectors;   supplying fuel to a first portion of a set of main fuel injectors, the pilot fuel nozzle, and the pilot tune stage injectors;   igniting the fuel injected by the first portion of the set of main fuel injectors to form a main combustion flame;   supplying fuel to a second portion of the set of main fuel injectors, the first portion of the set of main injectors, the pilot fuel nozzle, and the pilot tune stage injectors; and   igniting the fuel injected by the second portion of the set of main fuel injectors to enhance the main combustion flame.   
     
     
         21 . The method of  claim 20  further comprising modulating the fuel to the pilot fuel nozzle and/or the pilot tune stage injectors for improving stability to the main combustion flame. 
     
     
         22 . The method of  claim 20 , wherein fuel is supplied only to the pilot fuel nozzle and pilot tune stage injectors during lightoff of the gas turbine combustor and up to approximately a 10% load condition. 
     
     
         23 . The method of  claim 22 , wherein fuel is supplied to the first portion of the main injectors beginning at light-off to approximately the 10% load condition. 
     
     
         24 . The method of  claim 23 , wherein fuel is supplied to the second portion of the main fuel injectors beginning at light-off to approximately a 25% load condition. 
     
     
         25 . The method of  claim 20 , wherein the first portion of the set of main fuel injectors comprises an arc-like segment of fuel injectors spanning approximately 120 degrees and the second portion of the set of main fuel injectors also comprises an arc-like segment of fuel injectors spanning approximately 240 degrees. 
     
     
         26 . A method of operating a gas turbine combustor comprising:
 supplying fuel to a pilot fuel nozzle of the gas turbine combustor;   igniting the fuel injected by the pilot fuel nozzle;   supplying fuel to a first portion of a set of main fuel injectors and the pilot fuel nozzle;   igniting the fuel injected by the first portion of the set of main fuel injectors to form a main combustion flame;   supplying fuel to a second portion of the set of main fuel injectors, the first portion of the set of main injectors, and the pilot fuel nozzle; and   igniting the fuel injected by the second portion of the set of main fuel injectors to enhance the main combustion flame.   
     
     
         27 . The method of  claim 26  further comprising modulating the fuel to the pilot fuel nozzle. 
     
     
         28 . The method of  claim 26 , wherein fuel is supplied only to the pilot fuel nozzle and pilot tune stage injectors during lightoff of the gas turbine combustor and up to approximately a 10% load condition. 
     
     
         29 . The method of  claim 28 , wherein fuel is supplied to the first portion of the main injectors beginning at light-off to approximately the 10% load condition. 
     
     
         30 . The method of  claim 29 , wherein fuel is supplied to the second portion of the main fuel injectors beginning at light-off to approximately a 25% load condition. 
     
     
         31 . The method of  claim 26 , wherein the first portion of the set of main fuel injectors comprises an arc-like segment of fuel injectors spanning approximately 120 degrees and the second portion of the set of main fuel injectors also comprises an arc-like segment of fuel injectors spanning approximately 240 degrees.