【Q&A Question 139】2016.09.06
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【Q&A Question 139】September 06, 2016: What is the free rotation of a turbine rotor? The answer key will be available after responding; scoring is based on answering the key points. When steam stops flowing into the turbine, the rotor of the unit cannot stop immediately due to rotational inertia and will continue to rotate for a while. The period from the cessation of steam flow until the rotor comes to a complete stop is known as coasting.
The turbine rotor coasting period is the time elapsed from the disconnection of the generator, following the closure of the high and medium pressure main steam valves, control valves, as well as the high-pressure exhaust and extraction check valves, until the rotor comes to a complete stop.
It refers to the rotation of the rotor due to inertia after the main steam valve of the turbine is closed, which is known as coasting.
After the turbine stops, it continues to rotate due to inertia; the time elapsed from the closing of the control valves and emergency stop valves until the rotor comes to rest is called the coasting time
After the turbine is stopped, the rotor continues to rotate for a while due to inertia. The period from when the main steam valve and the throttle valve are closed until the rotor comes to a complete stop is called coasting, and the time required for this process is referred to as the rotor’s coasting time.
Rotation of the rotor due to inertia after the steam supply is stopped
Time from the start of closing the quick-shut valve to the rotor stopping rotating
The phenomenon in which the rotor of a steam turbine generator set continues to rotate on its own inertia after the steam supply is cut off as a result of tripping is known as coasting.
During shutdown, after the turbine is shut down, the main steam valve, the high-pressure control valve, and the medium-pressure combined steam valve are all closed. The turbine stops receiving steam, and the rotor continues to rotate due to its own inertia; this process is known as rotor coasting
The coasting of a turbine refers to the rotation that occurs from the moment the generator is disconnected until the automatic main steam valve and throttle valves close, bringing the rotor to a complete stop.