Gas turbine

A gas turbine comprising a compressor, a combustor receiving compressed air discharged from said compressor and fuel and burning the fuel and a turbine connected to said compressor through a shaft and driven by combustion gas from said combustor, wherein said gas turbine further comprises:

• a first fuel feed line supplying a first fuel from a first fuel supply means to said combustor;
• an extraction system extracting a part of compressed air supplied from said compressor;
• a control valve provided on said extraction system;
• an expander communicating with said extraction system and driven by the compressed air supplied therefrom;
• a first fuel compressor connected to said expander through a shaft for pressurizing a second fuel supplied from a second fuel supply means and having a lower calorific value than the first fuel;
• a second fuel compressor connected to said turbine through a shaft for further pressurizing the second fuel discharged from said first fuel compressor;
• a second fuel feed line supplying the second fuel pressurized in said second fuel compressor into said combustor;
• and
• a control means for controlling so as to suppress a pressure change of compressed air supplied to said combustor by opening said control valve according to a calorific value of the second fuel to increase a quantity of compressed air extracted from said extraction system and supplied to said expander upon switching of fuel to be supplied into said combustor from the first fuel to the second fuel.

A gas turbine comprising:

• a compressor;
• a combustor having a first fuel supply system for supplying a first fuel and a second fuel supply system for supplying a second fuel lower in calorific value than the first fuel and burning compressed air discharged from said compressor and fuel supplied through switching said first fuel supply system and said second fuel supply system;
• a turbine connected to said compressor through a shaft and driven by combustion gas supplied from said combustor;
• wherein said gas turbine further comprises
• an extraction system extracting a part of the compressed air supplied from said compressor to said combustor out of the system,
• a control valve provided on said extraction system,
• a detection means for detecting a calorific value of the second fuel supplied to said combustor, and
• a control means for controlling so as to suppress a pressure change of the compressed air supplied to said combustor by adjusting an opening of said control valve on the basis of a signal of a calorific value of the second fuel detected by said detection means when fuel to be supplied to said combustor is switched from the first fuel to the second fuel and changing so as to increase a quantity of compressed air extracted from said extraction system;
• and
• wherein said extraction system and said control valve supply said part of the compressed air to an expander driving a fuel compressor of said second fuel supply system.