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speed control mechanism in engine

In this lecture we will start our next chapter governors. You might have listened the word flywheel, governor is also like this but it has also some difference in function. So let us discuss governors and its types.


The function of the governor, as applied to the engines, is to adjust the supply of fuel according to the load requirements so as to keep the speeds at various, loads, as close to the mean speed as possible, over long range of working of the engines.
Its function is distinct from that of a flywheel, which acts as a reservoir and keeps the speed within certain limits of the mean speed during the thermodynamic cycles. The function of a flywheel is continuous from cycle to cycle, nut that of governor. It is more or less intermittent i.e. it reacts only whenever there is variation of load. In brief governor takes care of the change of speed due to load variation over periods of the engine’s running and tends to keep it as close to the mean speed as possible, where as the flywheel is responsible only in keeping the speed fluctuations, during each cycle within certain permissible limits of the mean speed. As such, one cannot be replaced by the other.

Principle of Operation When the load on an engine increases or decreases, obviously its speed will respectively decrease or increase to the extent of variation of load. This variation of speed has to be controlled by the governor, within small limits of the mean speed. This necessities that when the load increases and consequently the speed decreases, the supply of fuel to one engine has to be increased accordingly, to compensate for the loss of the speed, so as to bring back the speed close to the mean speed. Conversely when the load decreases, and the speed increase, the supply of fuel has to be reduced. This implies that the governor should have its mechanism working in such a way, that the supply of fuel is automatically regulated according to the load requirement for maintaining approximately a constant speed. There are some general terms used in governors that describe qualities of governor. These terms are as:

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