JPH062570A - Gas turbine - Google Patents

Abstract

PURPOSE:To prevent a phenomenon, called cat back, during turning operation of a rotor performed after operation of a gas turbine. CONSTITUTION:A device is provided such that turning operation of a rotor is suspended to perform spin operation based on a temperature difference between upper ard lower parts of a casing detected during the turning operation of the rotor performed after operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine applied to thermal power generation and the like.

[0002]

2. Description of the Related Art Conventionally, when a gas turbine is operated and then stopped as it is, the temperature in the upper layer becomes higher than that in the lower layer due to convection of air in the casing. For this reason, the temperature of the upper half of the rotor becomes higher than that of the lower half, and the rotor bends due to the difference in the amount of thermal expansion, causing plastic deformation. In order to prevent this, after the gas turbine is operated, a turning operation is performed in which the rotor is temporarily rotated by the turning motor at a very low speed of about 2 to 3 rpm.

[0003]

However, a temperature difference also occurs in the casing during such a turning operation of the rotor. FIG. 3 is an explanatory diagram of a conventional gas turbine used for thermal power generation and the like. In the figure, in one actual measurement example, the metal temperature difference between the upper part and the lower part of the casing may reach about 100 ° C. 12 hours after the stop, and thus the thermal expansion amount of the upper half of the casing C becomes lower half. If it is larger than the portion, the casing C shown by the solid line curves in a loose shape as shown by the dotted line. This phenomenon is a cat back
In some cases, the rotor during turning operation may come into contact with the stationary casing and the rotor may be unable to turn. If the gas turbine is left as it is in a state where the rotor cannot be turned in this manner, the rotor is curved and plastically deformed as described above, and the gas turbine cannot be restarted.

[0004]

A gas turbine according to the present invention is intended to solve the above-mentioned problems, and means for detecting a temperature difference between an upper part and a lower part of a casing during a turning operation of a rotor performed after the operation. And a means for stopping the turning operation of the rotor based on the detected temperature difference and performing a spin operation.

[0005]

That is, in the gas turbine according to the present invention,
Rotating operation of the rotor is stopped based on the temperature difference between the upper and lower parts of the casing detected during the turning operation of the rotor after the operation, and the spin operation is performed, which is performed after the operation of the gas turbine. When the temperature difference between the upper part and the lower part of the casing reaches a predetermined value during the turning operation of the rotor, the turning operation is automatically stopped and the spin operation is performed, and the temperature of the casing becomes uniform and the phenomenon called "catback" is prevented. It

[0006]

1 and 2 are explanatory views of a gas turbine according to an embodiment of the present invention. In the figure, the gas turbine according to the present embodiment is used for thermal power generation, etc., and if the gas turbine is stopped as it is after it is operated, the air in the casing becomes higher in temperature than the lower layer due to convection. . For this reason, the temperature of the upper half of the rotor becomes higher than that of the lower half, and the rotor bends due to the difference in the amount of thermal expansion, causing plastic deformation. In order to prevent this, a turning operation is performed in which the rotor is temporarily rotated by a turning motor at a very low speed of about 2 to 3 rpm.

However, a temperature difference also occurs in the casing during such a turning operation of the rotor. In one measurement example, the metal temperature difference between the upper part and the lower part of the casing reached about 100 ° C. 12 hours after the stop, and thus the thermal expansion amount of the upper half part of the casing was larger than that of the lower half part. Then, the casing bends in a loose shape. This phenomenon is called cat back, and in extreme cases, the rotor during turning operation may come into contact with the stationary casing, and the rotor may become unable to turn.
This gas turbine has a safety device,
This security device prevents a phenomenon called a catback. As shown in FIG. 1, the safety device includes a temperature detector 3 for detecting the metal temperature at the top of the casing of the gas turbine, a temperature detector 4 for detecting the metal temperature at the bottom of the casing, a subtractor 2 for calculating the temperature difference between the two. When the temperature difference reaches a set value, the switch 6 of the turning motor and its clutch 7 are disengaged, and the switch 1 of the starting motor 8 and its clutch 9 are transmitted by the transmitter 1 for starting the signal. It is composed of a timer 5 for setting the operating time of the motor.

During the turning operation of the rotor, which is performed after the operation of the gas turbine, the temperature difference between the top and the bottom of the casing gradually increases. As shown in FIG. 2, when the temperature difference reaches the set value, the turning motor is automatically stopped by the signal transmitted from the transmitter 1 and the clutch 7 is also disengaged. Then, the switch 8 and the clutch 9 of the starter motor are automatically turned on to rotate the starter motor of the gas turbine, and the gas turbine is spin-operated similarly to the start-up. The rotational speed of the rotor during spin operation of the gas turbine is usually about 600 rpm, although it varies depending on the specifications of the gas turbine. During this spin operation, the air supply / exhaust port of the casing is opened, and the air supply / exhaust in the casing is sufficiently performed. In addition to this spin operation, air is blown by an air compressor (not shown), and the air blows out the air stagnant in the casing. In this way, the temperature of the casing becomes uniform and the phenomenon called "catback" is prevented. After the casing temperature becomes uniform, timer 5
In reverse to the above process, the operation automatically shifts from the spin operation to the turning operation of the rotor.

The set value of the temperature difference in the casing when the gas turbine shifts from the turning operation to the spin operation varies depending on the specifications of the gas turbine, but is usually 10
0 ° C is sufficient. Further, instead of the subtractor 2, one end of the thermocouple wire of the thermocouple thermometer is connected to the top of the casing and the other end is connected to the bottom of the casing to detect the temperature difference in the casing by the thermoelectromotive force difference by the thermocouple. Good. In this case, the subtractor 2 and the temperature detectors 3 and 4 can be omitted. Further, the temperature difference between the top and bottom of the casing may be detected without using the timer 5, and the spin operation may be switched to the turning operation of the rotor based on the temperature difference. By preventing the phenomenon called "catback" in this way, contact between the rotating rotor and the stationary casing during the turning operation of the rotor, which is performed after the operation of the gas turbine, is prevented, and bending of the rotor due to turning failure is prevented. As a result, the reliability of the gas turbine is improved.

[0010]

The gas turbine according to the present invention is configured as described above, and the phenomenon called "catback" is prevented during the turning operation of the rotor performed after the operation of the gas turbine. There is no contact with the stationary casing.

[Brief description of drawings]

FIG. 1 is a block diagram of a gas turbine security device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of its operation.

FIG. 3 is an external view of a conventional gas turbine.

[Explanation of symbols]

 1 Transmitter 2 Subtractor 3 Temperature Detector 4 Temperature Detector 5 Timer 6 Switch 7 Clutch 8 Switch 9 Clutch

Claims (1)

[Claims] 1. A means for detecting a temperature difference between an upper part and a lower part of a casing during a turning operation of a rotor performed after the operation, and a turning operation of the rotor by stopping the turning operation of the rotor based on the detected temperature difference. A gas turbine comprising: a means for performing.