Centrifugal governors control the speed of an engine (or other prime mover) using mechanical control only. The centrifugal governor was invented in the late 1700s by James Watt and its design is still in use today. Centrifugal governors may be used on two stroke engines, four stroke engines, and many other types of prime mover.
How do Centrifugal Governors Work?
The below video is an extract from our Diesel Engine Fundamentals (Part 2) Online Video Course.
As the engine speed increases, the fly balls move up and outwards as the kinetic energy imparted to the fly balls overcomes the force of gravity. As the balls move, they act upon a series of linkages and a sliding sleeve.
The sliding sleeve is connected via an additional series of linkages to a valve. As the sleeve moves up and down the governor shaft, the valve changes position. Because of the direct mechanical linkages used, the valve response is proportional to the engine speed.
Centrifugal Governor Diagram From 1900
If the engine is operating to fast, the valve moves towards the closed position, which reduces the amount of fuel (or steam etc.) flowing to the engine, and thus the engine speed decreases.
If the engine is operating too slow, the valve moves towards the open position, which increases the amount of fuel (or steam etc.) flowing to the engine, and thus the engine speed increases.
Increasing Speed Example
As the engine speed increases, the fly balls move up and outwards, the sliding sleeve moves upwards, and the valve moves further towards the closed position.
Decreasing Speed Example
As the engine speed decreases, the fly balls move down and inwards, the sliding sleeve moves downwards, and the valve moves further towards the open position.