Method for controlling surge margin of gas turbine and extraction device for gas turbine

1. An extraction device of a gas turbine comprising a turbine coupled to a compressor formed of a plurality of compressor stages, the plurality of compressor stages including a first stage of the compressor, the extraction device comprising:

a controller;

a sensor unit configured to sense a rotational speed and a pressure ratio of each of the plurality of compressor stages, the sensor unit outputting to the controller a value indicative of the respectively sensed rotational speeds and the respectively sensed pressure ratios;

a compressor housing surrounding each of the plurality of compressor stages;

each of the plurality of compressor stages including an extraction pipe, wherein each of the extraction pipes having a plurality of inlet portions respectively communicating with the compressor housing and an outlet portion communicating with the turbine, and

wherein each of the plurality of inlet portions of the extraction pipe comprises a branch pipe having a first end inserted into the compressor housing and a second end that extends outside the compressor housing; and

a plurality of valves respectively installed in the plurality of inlet portions of the extraction pipe, each of the plurality of valves configured to have an opening degree controlled by the controller according to the value sensed by the sensor unit.

2. The extraction device of claim 1 , wherein the second ends of the branch pipes are joined with each other; and

wherein each of the outlet portion of the extraction pipes comprises a main pipe formed as a single pipe having one end communicating with the second ends of the branch pipes.

3. The extraction device of claim 2 , wherein the branch pipes each have a larger diameter than the main pipe.

4. The extraction device of claim 2 , wherein the branch pipes are disposed at equal intervals around the compressor housing and separated from each other in a circumferential direction of the compressor housing.

5. The extraction device of claim 2 , wherein the branch pipes are arranged symmetrically in a top-to-bottom direction and a side-to-side direction of the compressor housing.

6. The extraction device of claim 2 , wherein the plurality of valves are respectively disposed between the first and second ends of each of the plurality of inlet portions.

7. The extraction device of claim 1 , wherein the plurality of compressor stages include at least three compressor stages that are consecutively arranged beginning from the first stage of the compressor.

8. The extraction device of claim 7 , wherein the controller is configured to control the opening degree of each of the plurality of valves sequentially beginning from the first stage of the compressor.

9. The extraction device of claim 7 , wherein the controller is configured to open the plurality of valves corresponding to the first stage of the compressor and a next stage of the compressor, when the value outputted by the sensor unit indicates a normal operation of the first stage of the compressor and an abnormal operation of the next stage of the compressor.

10. The extraction device of claim 7 , wherein the controller is configured to open the plurality of valves corresponding to the first stage of the compressor and a next stage of the compressor, when the value outputted by the sensor unit indicates a normal rotational speed and a normal pressure ratio of the first stage of the compressor and indicates either of an abnormal rotational speed or an abnormal pressure ratio of the next stage of the compressor.