Which device automatically controls the speed of a steam turbine?

The governor valve functions as the device that automatically controls the speed of a steam turbine by adjusting the amount of steam that flows into the turbine. It maintains the desired speed by continuously monitoring the turbine's performance and making real-time adjustments to the steam supply. This is crucial for ensuring that the turbine operates efficiently and safely, as deviations from the proper speed can lead to operational issues or damage.

The governor valve achieves this by utilizing feedback from the turbine’s speed sensor, which informs the governor of any changes in speed. If the turbine speed exceeds the set point, the governor will close the valve slightly to reduce steam flow, and if the speed is below the desired level, it will open to allow more steam in. This automatic adjustment helps maintain a stable operation.

Other devices, while related to the management of fluid flow and system regulation, do not automatically control turbine speed in the manner that a governor does. For example, a throttle valve controls the flow and pressure of the steam manually or semi-automatically, but it does not provide continuous feedback for speed control. Similarly, control and regulating valves can manage flow rates but do not have the specific functionality to automatically maintain the turbine's operational speed as the governor does.