System and method of controlling a two-shaft gas turbine
A two-shaft gas turbine control system and method are provided that can enhance the efficiency and reliability thereof by controlling the amount of intake air spray and the rotational speed of a high-pressure turbine in accordance with the aperture of an inlet guide vane in a state where a two-shaft gas turbine is being operated with the efficiency of its compressor reduced. The control system includes a droplet spray device for spraying droplets to intake air for the compressor and a controller. The controller includes a fuel control section for adjusting a flow rate of the fuel to be supplied to the combustor, a spray flow rate control section for adjusting a flow rate of spray water to be supplied to the droplet spray device, an inlet guide vane aperture control section for adjusting the aperture of the inlet guide vane, and an efficiency improvement control section for outputting a command signal for bringing a balance between driving force for the compressor and power output of the high-pressure turbine to the fuel control section, the spray flow rate control section and the inlet guide aperture control section. In response to the commands from the improvement control section, the controller reduces the rotational speed of the high-pressure turbine and controls the inlet guide vane so as to be more open, thereby appropriately controlling the flow rate of the spray water.
1. A control system for a two-shaft gas turbine, the two-shaft gas turbine comprising:
a compressor provided with an inlet guide vane at an air inlet of the compressor;
a combustor configured to mix compressed air compressed by the compressor with fuel for sake of combustion to generate combustion gas;
a high-pressure turbine mechanically connected to the compressor and driven by the combustion gas generated by the combustor; and
a low-pressure turbine driven by expanded combustion gas resulting from action of the high-pressure turbine driven by the combustion gas;
a high pressure nozzle configured to spray droplets to intake air for the compressor; and
the control system comprising:
a tachometer configured to detect a rotational speed of the high-pressure turbine;
an aperture detector configured to detect an aperture of the inlet guide vane; and
a controller that is configured to take in the rotational speed of the high-pressure turbine detected by the tachometer and the aperture of the inlet guide vane detected by the aperture detector,
wherein when the rotational speed of the high-pressure turbine detected by the tachometer is a rated rotational speed or a fraction of the rated rotational speed and the aperture of the inlet guide vane detected by the aperture detector is less than a specified value, the controller
lowers the rotational speed of the high-pressure turbine while controlling the inlet guide vane so as to be more open,
monitors the aperture of the inlet guide vane along with the reduction in the rotational speed of the high-pressure turbine,
stops the reduction in the rotational speed of the high-pressure turbine and starts intake air spray of the high pressure nozzle when the aperture of the inlet guide vane exceeds the specified value.
2. A control system for a two-shaft gas turbine, the two-shaft gas turbine comprising:
a compressor provided with an inlet guide vane at an air inlet of the compressor;
a combustor configured to mix compressed air compressed by the compressor with fuel for sake of combustion to generate combustion gas;
a high-pressure turbine mechanically connected to the compressor and driven by the combustion gas generated by the combustor; and
a low-pressure turbine driven by expanded combustion gas resulting from action of the high-pressure turbine driven by the combustion gas;
a high pressure nozzle configured to spray droplets to intake air for the compressor; and
the control system comprising:
a tachometer configured to detect a rotational speed of the high-pressure turbine;
an aperture detector configured to detect an aperture of the inlet guide vane; and
a controller that is configured to
adjust a flow rate of the fuel to be supplied to the combustor,
adjust a flow rate of spray water to be supplied to the high pressure nozzle,
adjust the aperture of the inlet guide vane, and
take in the rotational speed of the high-pressure turbine detected by the tachometer and the aperture of the inlet guide vane detected by the aperture detector,
wherein when the rotational speed of the high-pressure turbine detected by the tachometer is a rated rotational speed or a fraction of the rated rotational speed and the aperture of the inlet guide vane detected by the aperture detector is less than a specified value, the controller
lowers the rotational speed of the high-pressure turbine while controlling the inlet guide vane so as to be more open,
monitors the aperture of the inlet guide vane along with the reduction in the rotational speed of the high-pressure turbine,
stops the reduction in the rotational speed of the high-pressure turbine and starts intake air spray of the high pressure nozzle when the aperture of the inlet guide vane exceeds the specified value.
3. The control system according to claim 1 , further comprising:
a clearance sensor configured to measure a tip clearance of a rotor blade at an intermediate stage of the compressor, wherein
the controller receives a tip clearance of the rotor blade detected by the clearance sensor, and
stops the intake air spray when a difference from a preset clearance margin is less than a predetermined value.
4. A method for controlling a two-shaft gas turbine, the method comprising:
adjusting a flow rate of the fuel to be supplied to a combustor of the two-shaft gas turbine, the two-shaft gas turbine including a compressor provided with an inlet guide vane at an air inlet of the compressor, a combustor configured to mix compressed air compressed by the compressor with fuel for sake of combustion to generate combustion gas, a high-pressure turbine mechanically connected to the compressor and driven by the combustion gas generated by the combustor, a low-pressure turbine driven by expanded combustion gas resulting from action of the high-pressure turbine driven by the combustion gas, a high pressure nozzle configured to spray droplets to intake air for the compressor, a tachometer configured to detect a rotational speed of the high-pressure turbine, an aperture detector configured to detect an aperture of the inlet guide vane, and a controller;
adjusting a flow rate of spray water to be supplied to the high pressure nozzle;
adjusting the aperture of the inlet guide vane; and
taking in the rotational speed of the high-pressure turbine detected by the tachometer and the aperture of the inlet guide vane detected by the aperture detector, wherein
when the rotational speed of the high-pressure turbine detected by the tachometer is a rated rotational speed or a fraction of the rated rotational speed and the aperture of the inlet guide vane detected by the aperture detector is less than a specified value, the controller
lowers the rotational speed of the high-pressure turbine while controlling the inlet guide vane so as to be more open,
monitors the aperture of the inlet guide vane along with the reduction in the rotational speed of the high-pressure turbine, and
stops the reduction in the rotational speed of the high-pressure turbine and starts intake air spray of the high pressure nozzle when the aperture of the inlet guide vane exceeds the specified value.