Method for operating a gas turbine with sequential combustion and gas turbine for conducting said method

A gas turbine comprising:

• a compressor,
• a first combustor with a first combustion chamber and first burners, which receives compressed air from the compressor,
• a second combustor with a second combustion chamber and second burners, which receives hot gas from the first combustor with an inlet temperature of the second combustor, and
• a turbine, which receives the hot gas from the second combustor;
• a mixer arranged in a hot gas channel directly connecting the first combustor and the second combustor, the hot gas channel extending between the first combustor and the second combustor to supply the hot gas from an exit of the first combustor to an inlet of the second combustor;
• the mixer being connected to a dilution air supply, the mixer configured to mix air from the dilution air supply with the hot gas in the hot gas channel;
• and
• a controller configured to control the dilution air supplied to the hot gas channel;
• wherein there is no turbine located between the first combustor and the second combustor;
• wherein the inlet temperature of the second combustor is reduced for base-load operation of the gas turbine and the inlet temperature of the second combustor is increased when decreasing gas turbine load from the base-load to part-load via control of the dilution air supply.

A method of operating a gas turbine with sequential combustion comprising:

• compressing air in via a compressor;
• receiving compressed air from the compressor by a first combustor having a first combustion chamber and first burners;
• mixing dilution air with hot gas received from an exit of the first combustor in a hot gas channel extending between the exit of the first combustor and an inlet of a second combustor via a mixer to reduce a temperature of the hot gas and to reduce an inlet temperature of the second combustor during base-load operation of the gas turbine;
• receiving the hot gas from the exit of the first combustor at the inlet of the second combustor via the hot gas channel, the second combustor having a second combustion chamber and second burners and wherein there is no turbine located between the first combustor and the second combustor;
• controlling a flow of the dilution air supplied to the hot gas in the hot gas channel via a controller to control reduction of the inlet temperature of the second combustor during the base-load operation of the gas turbine;
• adjusting a second combustor inlet temperature target based on a load of the gas turbine such that the inlet temperature of the second combustor is reduced when the gas turbine is at the base-load operation and the inlet temperature of the second combustor is increased when gas turbine load decreases from the base-load to a part-load via the controlling the flow of the dilution air.