Porter Governor Construction, Working, Equation of Height
Porter governor is dead weight loaded type of gravity controlled centrifugal governor. It is similar to Watt governor with slight modification. When a heavy central load is attached to the sleeve of Watt governor, it becomes a porter governor.
Read: Watt Governor – Construction and Working
Construction of porter governorThe two balls are pivoted at the top so that it can move up and down on a vertical spindle as the speed of revolution of the spindle vary. The lower links are connected to the central sleeve. Vertical sleeve can move up and down along with the ball movements. Two stoppers are provided in spindle to limit the movement of the sleeve. The sleeve is carrying a heavy central load. A mechanism is connected to the sleeve of the governor to actuate the throttle valve.
Working of porter governorThe engine is connected to the central spindle of governor through gear trains. When the load on an engine decrease, there will be a sudden increase in speed of the engine. Governor spindle speed also increases. The centrifugal effect tends ball pair to move outward direction. The upper arms of ball pivoted at the top. Hence the lower arm pushes the sleeve upward as ball move outward. It actuates the throttle valve through the mechanism connected to the sleeve to decrease the fuel supply to the engine. The decreased availability of fuel decreases the speed. Hence speed is maintained.
In the case of increasing the load speed of the engine decreases. It causes downward movement of ball and sleeve. It makes throttle valve to increase fuel supply and hence to increase the speed of the engine.
Porter governor - equation of heightWhen the length of arms and links of height governor are same,
m = Mass of the ball
M = Mass of center load and sleeve
ω = Angular velocity of the balls and arms about the spindle axis
g = Acceleration due to gravity
N = Speed of ball in rpm
The ratio of height of a porter governor to that of Watt governor is (m+M)/M