Watt governor is the simplest form of centrifugal governors. Centrifugal governors are special type of governors with a feedback system that controls the speed of an engine by regulating the flow of fuel or working fluid.
Watt governor has two fly balls attached to two arms of negligible masses. Watt governor is used to supply the required amount of fuel at different speed.
When the speed of engine increases, the supply of fuel needs to increase and as the engine speed decreases the supply of fuel should be decreased . So the fuel supply should be regulated according to the speed of the engine. With the help of watt governor we can obtain a required load on the engine with constant smooth function.
Watt governor consists of two fly balls which are located at the end of the arms . The upper parts of these two arms are pivoted to the spindle. This spindle is driven by the engine through the bevel gears. The lower parts of arms are connected to the sleeve which move upward or downward as the balls moves upward or downward . The sleeve has stopper which are placed at up and down of sleeve to limit its movement. The sleeve is connected to throttle valve through bell crank lever . The movement of sleeve controls openng and closing of throttle valve.
Working of Watt Governor
Watt governors consists of two balls which are attached to both arms which are of negligible mass. The upper side of arms are pivoted so that its balls can move upwards and downwards. These arms are connected to the spindle . The engine drives the spindle through bevel gears.
When the speed of the engine increases, the spindle rotates at high speed. The arms as well as the balls connected to spindle rotates at high speed. As the balls rotates at high speed and the upper side of arms are pivoted to the spindle , the balls moves in upward direction.
The lower arms are connected to the sleeves. These sleeeves are keyed to the spindle in such a way that it revolves with the spindle and can slide up and down according to the speed of rotation of spindle.
As the engine speed increases and the balls move in upward direction, the sleeve connected to arms also moves upward and similarly moves downward when the speed of engine decreases. There are stoppers placed above and below the sleeve to limit the upward and downward motion of the sleeve.
Now, there are two cases :-
i) When engine speed increases.
ii) When engine speed decreases.
Lets discuss these two case.
i) When the engine speed increases :-
When the speed of engine increases , the load on the engine decreases and the speed of rotation of spindle increases. The centrifugal force on balls increases and the balls move upwards and hence the sleeve moves upward. As the sleeve moves upward . The upward movement of sleeve causes the throttle valve at the end of the ball crank lever to decrease the fuel supply. The power output is reduced.
ii) When the engine speed decreases :-
When the engine speed decreases, the load on engine increases and speed of rotation of spindle decrease. The centrifugal force on balls decreases and the balls moves downwards. As the balls move downwards, hence the sleeve moves downward whic causes the throttle valve to increase the fuel supply and the power output is increased.