Method for starting premixed combustion in combustor for two-shaft gas turbine

Abstract

A two-shaft gas turbine is capable of starting premixed combustion without extinguishing a flame. The two-shaft gas turbine includes a combustor and a gas generator controller. The combustor has a premix burner that includes combustion regions in which premixed combustion is to be carried out individually. The gas generator controller controls the combustor. In a method for starting the premixed combustion in the combustor, the gas generator controller selects at least one of the combustion regions in which the premixed combustion is to be carried out, on the basis of a fuel-air ratio, and starts premix combustion in the selected combustion region or separately in each of the selected combustion regions. Further, as the fuel-air ratio is increased, the controller increases the number of the selected region in which the premixed combustion is carried out.

1 . A two-shaft gas turbine comprising:
 a combustor that includes a first burner for diffusion combustion and a second burner for premixed combustion, the second burner being circularly arranged around the first burner and including at least two regions arranged in a circumferential direction to be carried out in the regions individually; and   a controller that controls the start of the premixed combustion that is to be carried out in the combustor,   wherein the controller selects at least one of the regions on the basis of the ratio of the amount of fuel to the amount of air in order to start the premixed combustion, starts the premixed combustion in the selected region or starts separately in each of the selected regions, and increases the number of the selected region in which the premixed combustion is carried out, as the fuel-air ratio is increased.   
   
   
       2 . The two-shaft gas turbine according to  claim 1 ,
 wherein as the fuel-air ratio is increased, the controller increases the number of the selected region in which the premixed combustion is carried out in an order of location from an upper side to a lower side of the combustor.   
   
   
       3 . The two-shaft gas turbine according to  claim 1 ,
 wherein as the fuel-air ratio is increased, the controller increases the number of the selected region in which the premixed combustion is carried out such that one of the regions to be selected is adjacent to the selected one of the regions.   
   
   
       4 . A method for starting premixed combustion in a combustor for a two-shaft gas turbine, the combustor including a first burner for diffusion combustion and a second burner for premixed combustion, the second burner being circularly arranged around the first burner and including at least two regions arranged in a circumferential direction to be carried out in the regions individually, the method comprising the steps of:
 selecting at least one of the region on the basis of the ratio of the amount of fuel to the amount of air by means of the controller that controls the start of the premixed combustion that is to be carried out in the combustor, and   starting the premixed combustion in the selected region or separately in each of the selected regions,   wherein as the fuel-air ratio is increased, the controller increases the number of the selected region in which the premixed combustion is carried out.   
   
   
       5 . The method according to  claim 4 ,
 wherein as the fuel-air ratio is increased, the number of the selected region in which the premixed combustion is carried out is increased in an order of location from an upper side to a lower side of the combustor.   
   
   
       6 . The method according to  claim 4 , wherein
 as the fuel-air ratio is increased, the number of the selected region in which the premixed combustion is to be carried out is increased such that one of the regions to be selected is adjacent to the selected one of the regions.