Patent Number: 6,253,537

Title: Revolution speed control method in gas turbine shutdown process

Abstract: Stress occurring in a moving blade in a gas turbine stopping process is decreased. Time t.sub.1 is load decrease start or fuel throttling start, time t.sub.2 is no load operation start, time t.sub.3 is fuel shut-off and time t.sub.4 is a time of largest stress. A 4/4 load maintained until t.sub.1 decreases gradually to a 0/4 load at t.sub.2, which is then maintained until t.sub.3 and then decreases further. The rotational speed is the rated speed until t.sub.2, at which point it is controlled to be decreased gradually to about 60% of the rated rotational speed at t.sub.3. The metal differential temperature between a moving blade point A and a platform point B is constant until t.sub.1 and is then decreased slightly between t.sub.1 and t.sub.2 and between t.sub.2 and t.sub.3. Differential temperature .DELTA.t, largest after t.sub.3, occurs at t.sub.4. Stress occurring in the moving blade, while decreasing between t.sub.1 and t.sub.3, becomes largest at t.sub.4 by the effect of centrifugal force and thermal stress, but as the rotational speed is decreased to about 60% of the rated rotational speed at t.sub.3 and the metal temperature is also decreased as compared with the prior art, the influence of the centrifugal force and the differential temperature is decreased, whereby stress occurring in the moving blade is mitigated.

Inventors: Suenaga; Kiyoshi (Takasago, JP), Hashimoto; Yukihiro (Takasago, JP), Tomita; Yasuoki (Takasago, JP)

Assignee: Mitsubishi Heavy Industries, Ltd.

International Classification: F01D 21/00 (20060101); F01D 21/06 (20060101); F02C 9/00 (20060101); F02C 9/46 (20060101); F02C 007/00 ()

Expiration Date: 07/03/2018