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GOVERNING OF SIMPLE STEAM ENGINE





The main purpose of governing of simple steam engine is to controls the speed of an engine by regulating the amount of fuel (or working fluid) admitted, so ita maintain the speed of an engine fairly constant irrespective of load. or fuel-supply conditions.




The governing of simple steam engines is done by the following two methods :





(1) By throttling the steam.
(2) By varying cut-off point of the steam.


1. Throttle governing :

Now a Days throttle governing process are widely using method in steam turbine governing for smaller turbines where the steam flow is less.The throttle governing, of simple steam engines, is a method of controlling the engine output by varying pressure of the intake steam. The pressure of intake steam is varied by opening or closing the throttle valve under the control of a centrifugal governor. In throttle governing, cut-off point of the engine cylinder remains the same.



If load on the engine is increased, then pressure of the admission steam is also increased to suit the increased load.The throttle governing of a simple steam engine result in the reduction of its thermal efficiency, and as such is somewhat wasteful with regard to the steam. The reason for the same is that at any load (below the full load), the full pressure of the steam is not used. Moreover, due to constant cutoff, a large quantity of steam is used in every stroke. This also tends to lower the thermal efficiency of the engine.


2. Cut-off governing :



It is another process by which turbine's speed can be controlled. The cut-off governing, is used in simple steam engine, to controlling output by varying volume of intake steam. This is done by varying the cut-off point by slide valve under the control of a centrifugal governor. It may be noted that In a cut-off governing, pressure of the intake steam remains the same.If a load on the engine is increased, then pressure of the admission steam is also increased to suit the increased load.This method is more economical and efficient. That is why these days cut-off governing is mostly used. But it requires a special valve gear.






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