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.
The function of the governor 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, but that of governor it is more or less intermittent, i.e., it reacts only whenever there is variation of load. The speed control mechanism by governor is shown in Figure 14.2.
Figure 14.2 Speed Control by Governor
Figure 14.2 shows schematic diagram of a governor along with linkages which regulates the supply of fuel. The governor shaft is coupled with engine shaft. If load on the engine increases the engine speed tends to reduce, as a result of which governor balls move inwards. The inward movement of ball causes sleeve to move downwards and hence increase the opening of valve through the linkage. Thus, fuel supply increases at higher load.
On the other hand, decrease in the load increases engine speed. As a result of which the governor balls try to fly outwards. This causes an upward movement of the sleeve and it reduces the supply of fuel. Thus, the energy input is adjusted to the new load on the engine. Thus, the governor senses the change in speed and then adjusts the supply of fuel.
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