Governor is a type of mechanical device which is generally
used to determine and regulate the speed of the engine to the desired level. It
is a particular feedback system used where is the need to control
variation of load present in the system. The main purpose of the governor is to
control the flow of fuel into the engine to maintain a constant speed hence sometimes it is known as speed limiter. When the load of an engine increases the
speed of engine decreases and vice versa when the load on engine decreases
speed of engine increases. This is where governors play an important role to
increase or reduce the fuel flow to engine according to the requirements.
Types of Governor:
The Governors are mainly divided into two types i.e
Centrifugal Governor and Inertia Governor. These are further divided into following types according to their design.
1. Centrifugal Governor
In Centrifugal Governor only centrifugal force and change in
speed are responsible for controlling the actions. It widely used due to the
variety of applications and mostly preferred when balance on the masses is needed
in the operation.
Principle
It works on the principle of balancing centrifugal force
of the rotating balls.
Construction
A Centrifugal Governor has a simple design. This type of
governor has multiple masses known as governor balls which rotate at the
distance from the axis of a shaft and driven through suitable gearing from the
engine crankshaft. It has two balls of equal masses attached to the arm. These
balls are provided by the combination of dead weight or spring. Spindle axis is
connected to the sleeve and driven by bevel gear mechanism connected with crankshaft.
Throttle valve is connected to the sleeves and operate by the actual change of
speed of engine. As load increases speed got decreases and the speed of
governor ball as well as governor also decreases which is geared with the crankshaft.
Working
It works as the mechanical link between the throttle which
is responsible for fuel supply and the speed. The governor balls revolve with spindles and create a centrifugal force in the inward direction which is generally known as the
controlling force. A governing action is depends upon the change of speed and
centrifugal force provided by the balls. As soon as the throttle valve opens it
increase the supply of fluid increasing speed of the engine. The inward and upward
movement of the ball is transmitted by the governor sleeve to the throttle valve which
controls the amount of fuel supplied to the engine. As soon as the shaft
rotates, the object start rotating around the shaft and goes away from it due
to action of centrifugal force which operate the throttle valve.
Advantages
1. Easy to balance revolving parts.
Limitations
1. Slow response and less sensitive.
Applications
1. It limits the rotation speed in the internal combustion
engine of automobile and keep it controlled according desired speed.
2. It is used to control speed of turbine shaft in
Hydro-electric power plant.
3. Centrifugal governors are also used to control speed of
mechanical music box.
The Centrifugal Governors are further classified into two
types. Pendulum and spring control governor.
A.) Pendulum type Governor:
Watt Governor is a pendulum governor according to their design.
a.) Watt Governor:
It is oldest and simplest type of Centrifugal governor.
Previously it was used by James watt in his steam engine.
Construction
In Watt governor two balls are arranged on the sleeves
consisting arms. Upper side of the arm is connected to the spindle to move the
ball in the upward and downward direction when they revolve with Spindle. The
lower arm is connected to the sleeve which is joined to the spindle to operate the throttle valve. The spindle gets drives through a bevel gear and two stoppers are provide
to the bottom and top of the spindle to restrict the movements of the sleeves.
Working
When the load at the engine increases the angular velocity
as well as speed of the engine automatically decreases. At the uniform speed
controlling force is equal to the centrifugal force which balances each other
but when centrifugal force on balls decreases, the balls and spindle start to
move inward and downward direction, respectively. These movements are responsible
for the mechanism of the throttle valve and cause it opening widely which increases the fuel supply to maintain the speed.
Limitations
1. suitable for only vertical position application.
Applications
1. It is used in ship and train to maintain the speed of
engine.
2. It can be used in AC generators to maintain electric
supply.
B.) Gravity Loaded Governor:
There are two different design of gravity controlled centrifugal governor.
1. Porter Governor
2. Proell Governor
a.) Porter Governor
It is a dead weight loaded type governor works on the action
of gravity. Porter Governor is a modification of Watt governor.
Construction
In Porter Governor two balls are located at the top and load
is attached to the sleeves. The lower
link is connected to central sleeve and two stoppers are provided to control
the movements of sleeves. A mechanism is
attached to the sleeves to operate the throttle valve.
Working
The balls tend to moves up and down on the spindle due to
the speed of revolution of the spindle. As load at the engine decreases speed
of the engine as well as spindle also tends to increases. Centrifugal force is
responsible for movement of balls in the upward direction while lower arm
pushes the sleeves upward to move the ball outward. These movements actuate the
throttle valve and fuel supply gets decreases through the mechanism connected
to the sleeves.
b.) Proell Governor
It is another type of governor works on the gravity control.
The function of porter and proell governor are same with little difference in
working.
Construction and working
The construction and working of the Proell Governor is
nearly similar to the porter governor. Here revolving balls are attached to the
extension link situated at lower part and it reduces the change in the speed
responsible for movement of the sleeves. The movements of sleeve and balls
operates the throttle valve and decreases fuel supply to the engine.
C.) Spring Controlled Governor"
There are four different design of spring control governor.
1. Hartnell Governor
2. Wilson Hartnell Governor
3. Hartung Governor
4. Pickering Governor
a.) Hartnell Governor
Construction
Hartnell Governors consists two bell cranks situated the
different points of the frame. A frame is attached to the spindle, each lever
carries a ball to the horizontal roller at the end of vertical arm. The helical
ring is provided to maintain the equal level force on the rollers and
arrangement of the screw is there to adjust a force of the spring.
Working
The working of Hartnell governor is depends on control of
spring force. Here spring rotates around the spindle axis and controls the
movement of the ball and sleeves. The
spring applies the downward force while sleeves move upward and downward
depending on the speed. Two bell cranks situated at the frames carries a ball
at one end and roller carry it at the other end. As speed of the engine
increases ball moves outward and bell crank lever moves at the pivot lifting
sleeves upward against the spring force. These movements then passed to the
throttle valve with the help of mechanism and it results in lowering fuel
supply as well as speed.
Advantages
1. Suitable for very
high speed
2. Pre-compression can be adjusted to achieve desired
equilibrium speed.
b.) Wilson- Hartnell
Construction and working
The balls are associated with the vertical arm and attached
to the spring arranged on either side of the sleeves. The spring consists two
parts which belongs to the each ball. At the horizontal arm roller comes into
contact with sleeves and press it and make the bell-cranks to rotate along the
spindle. Speed tends to improve the ball movement and spring gets exerted at
the inward pressing roller against the sleeves due to centrifugal force. One
end of the spring is attached to the spring and other is connected to the lever
and it tends to remain the sleeves down.
c.) Hartung Governor:
Construction and working
This is another type of governor work on the principle of
controlled by the movement of spring. In Hartung type governor bell crank
levers are connected with the rotating spring balls. These balls are compressed
against the frame of the governor while rollers are pressed against the sleeves
at the horizontal arms.
d.) Pickering Governors
Construction and working
In Pickering Governor there are three springs arranged
around the spindle. The arrangement ids angular and each spring hold similar
weight at the centers. The revolving balls act against these flat spring and
weights move outwards. Spring tends to bend as the ball rotate about the axis
of the spindle with greater speed.
Advantages
1. Quick response to the change in load
2. Great durability and reliability
Application
1. It is used in Gramophone for adjusting the speed of
turntable
2. Inertia Governor
Inertia governor is completely different from the
centrifugal governor. The combination of angular and centrifugal force is used
to control the position of the balls as well as operation of the Governor.
Since it is not very popular, it is preferred when a rapid response is the main
concern.
Principle
It works on the principle of movement of inertia due to both
centrifugal and inertia force.
Construction
This type of governor is connected to the crankshaft and
flywheels of an engine. The governor balls are arranged in such a way that the
position of it is affected by the force due to angular acceleration of the
shaft. A suitable spring is loaded inside
the governor to control the amount of displacement of governor balls and the
mechanism of governor alters the supply of energy to the engine.
Working
In inertia governor more rapid response is obtained to the
change of load as the position of the balls are affected by the rate of change
of speed of the governor shaft. This type of governors action is depends upon
acceleration and not due to the finite change in speed. A movement of the ball
is controlled by spring and mechanism of governor and through this the supply
of air fuel mixture can be controlled.
Advantages
1. Highly sensitive to varying load
2. Quick response due to fast reaction
Limitations
1. Hard to balance revolving parts
Applications
1. It is used in the steam turbine to control and maintain
desired speed of the turbine when load increase or decrease during working
2. It is used in a diesel engine to control speed of the
engine at a particular set point.
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