Gas turbine with sequential combustion arrangement

Abstract

The present disclosure refers to a method for operating a gas turbine with sequential combustors having a first-burner, a first combustion chamber, and a second combustor arranged sequentially in a fluid flow connection. To minimize emissions and combustion stability problems during transient changes when the fuel flow to a second combustor is initiated the method includes the steps of increasing the second fuel flow to a minimum flow, and reducing the first fuel flow to the first-burner of the same sequential combustor and/or the fuel flow to at least one other sequential combustor of the sequential combustor arrangement in order keep the total fuel mass flow to the gas turbine substantially constant. Besides the method a gas turbine with a fuel distribution system configured to carry out such a method is disclosed.

What is claimed is: 
     
         1 . A method for operating a gas turbine having at least a compressor, a sequential combustor arrangement with a plurality of sequential combustors, and a turbine downstream of the sequential combustor arrangement, each sequential combustor having a first-burner, a first combustion chamber, and a second combustor arranged sequentially in a fluid flow connection, the method comprising:
 compressing an inlet gas in the compressor,   admixing a first fuel in the first-burners of the sequential combustor,   burning a mixture of first fuel and compressed gas in the first combustion chamber to obtain first combustion products,   wherein at low relative load no further fuel is injected into the sequential combustor downstream of the first-burner, and at high relative load a second fuel is injected into the sequential combustor downstream of the first combustion chamber, and   burning a mixture of first combustion products, and the second fuel to obtain second combustor combustion products, and expanding the combustion products in the turbine,   wherein during part load operation of the gas turbine, when initiating fuel admittance of the second fuel, a second fuel flow is increased to a minimum flow, and a first fuel flow to the first-burner of the same sequential combustor and/or a fuel flow to at least one other sequential combustor of the sequential combustor arrangement is reduced to keep a total fuel mass flow to the gas turbine substantially constant.   
     
     
         2 . The method as claimed in  claim 1 , wherein dilution gas is admixed to the first combustor combustion products, before burning the mixture of first combustor combustion products and second fuel. 
     
     
         3 . The method as claimed in  claim 1 , wherein the first fuel flow to the first-burner upstream in the same sequential combustor, in which the second fuel flow is initiated, is reduced. 
     
     
         4 . The method as claimed in  claim 1 , wherein the first fuel flow to at least one neighboring sequential combustor of the sequential combustor, into which a second fuel flow is initiated, is reduced. 
     
     
         5 . The method as claimed in  claim 1 , wherein the second fuel flow is initiated at the same time to a plurality of sequential combustors. 
     
     
         6 . The method as claimed in  claim 1 , wherein the second fuel flow to all the sequential combustors of the sequential combustor arrangement is initiated at the same time and that the first fuel flow to all the first-burners of the sequential combustor arrangement is reduced at the same time. 
     
     
         7 . The method as claimed in  claim 1 , wherein the second fuel flow to the sequential combustors initiated sequentially for individual sequential combustors or initiated for groups of sequential combustors as a function of at least one of: the gas turbine load, a temperature indicative of the load, and a pressure indicative of the load. 
     
     
         8 . The method as claimed in  claim 7 , wherein the first fuel flow to the first-burner of the same sequential combustor and/or the fuel flow to at least one other sequential combustor which was reduced upon initiation of the second fuel flow is increased back to the fuel flow before initiation of the second fuel flow, and then initiate the second fuel flow to the next sequential combustor or next group of sequential combustors. 
     
     
         9 . The method as claimed in  claim 6 , wherein the second fuel flow is increased above a minimum flow after the fuel flow to the first-burner of the same sequential combustor arrangement and/or the fuel flow to the at least one other sequential combustor which was reduced upon initiation of the second fuel flow is increased back to the fuel flow before initiation of the second fuel flow to control the load of the gas turbine. 
     
     
         10 . The method as claimed in  claim 1 , wherein the switching off of the second fuel is carried out in reverse order. 
     
     
         11 . The method as claimed in  claim 1 , wherein after ail first-burners and second fuel injections are brought into operation the fuel flow to at least one first-burner is increased over the fuel flow to at least another first-burner of the sequential combustor arrangement and that the fuel flow to the second fuel injection of the sequential combustor with increased fuel flow to its first-burner is reduced compared to the fuel flow to at least another second fuel injection of the sequential combustor arrangement such that the total fuel flow to the sequential combustor remains unchanged.