 Governors

The function of a governor is to regulate (control) the mean speed of an

engine, when there are variations in the load e.g. when the load on an engine
increases, its speed decreases, therefore it becomes necessary to increase the
supply of working fluid. And when the load on the engine decreases, engine
speed increases and thus less working fluid is required. The governor
automatically controls the supply of working fluid to the engine with the varying
load conditions and keeps the mean speed within certain limits.
 Types of Governors
The major classification of governor is –
1. Centrifugal governors and 2. Inertia governors.
The centrifugal governors, further classified as

 Terms Used in Governors

The following terms are used in governors
1. Height of a governor:- It is the vertical distance from the centre of the ball to
a point where the axes of the arms (arms produced) intersect on the spindle
axis. It is usually denoted by h.
2. Equilibrium speed:- It is the speed at which the governor balls, arms etc., are
in complete equilibrium and the sleeve does not tend to move upwards or
downwards.
3. Mean equilibrium speed:- It is the speed at the mean position of the balls or
the sleeve.
4. Maximum and minimum equilibrium speeds:- The speeds at the maximum
 and minimum radius of rotation of the balls, without tending to move either
way are known as maximum and minimum equilibrium speeds respectively.
5. Sleeve lift:- It is the vertical distance which the sleeve travels due to change in
equilibrium speed.

 Difference Between Flywheel & Governor

Governor Flywheel
1. It maintains the mean speed of the 1. Flywheel maintains the fluctuations
m/c or prime mover constant by in energy and speed during cycle by
varying the fuel or working fluid supply absorbing or releasing the available
according to variation in load of m/c. energy during that cycle only.

2. It regulates the speed from cycle to 2. Flywheel is useful for regulating the
cycle i.e. over no. of cycles of a prime speed during one cycle.

3. It regulates speed by regulating fuel 3. Flywheel stores and releases energy

supply. available during a cycle.

4. It is very essential element as it 4. Flywheel may not be essential if

regulates fuel supply as per demand cycle fluctuations are not present as in
case of multi cylinder engines.

 Centrifugal Governors
The centrifugal governors are based on
the balancing of centrifugal force on the
rotating balls by an equal and opposite
radial force, known as the controlling
force.
It consists of two balls of equal mass,
which are attached to the arms. These
balls are known as governor balls or fly
balls. The balls revolve with a spindle,
which is driven by the engine through
bevel gears.
The upper ends of the arms are pivoted to the spindle, so that the balls may rise
up or fall down as they revolve about the vertical axis. The arms are connected
by the links to a sleeve, which is keyed to the spindle. This sleeve revolves with
the spindle; but can slide up and down.
The balls and the sleeve moves up when the spindle speed increases, and moves
down when the speed decreases. To keep this upward and downward
movement of balls and sleeve, the two stops (upper & lower) S, are provided on
the spindle. The sleeve is connected to a throttle valve by means of a bell crank
lever, which regulates the fuel suppl.
When the load on the engine increases, the engine and the governor speed
decreases. And due to this centrifugal force on the balls decreases and the balls
moves inwards, the sleeve moves downwards. Thus the throttle valve opens to
supply the fuel, and the engine speed increases.
When the load on the engine decreases, the engine and the governor speed
increases, the centrifugal force on the balls increases, the balls moves outwards
and the sleeve moves upwards. This upward movement of the sleeve reduces
the supply of the working fluid by means of throttle valve through bell crank
lever. Thus the speed of engine decreaes.
 Watt Governor: The simplest form of a
centrifugal governor is a Watt governor. It
is basically a conical pendulum with links
attached to a sleeve of negligible mass.

 Porter Governor: The Porter governor is

a modification of a Watt’s governor, with
central load attached to the sleeve as
shown in Fig. The central load moves up
and down and additional downward force
increases the speed of revolution required
for the balls movements.

 Proell Governor: This governor is similar

as that of Porter governor (with central
weight on sleeve), but difference is that,
the balls are attached to a short link which
is joined at intersection of link & arm. The
required balls are small in size.
  Hartnell Governor:
A Hartnell governor is a spring loaded type
governor. It is having two bell crank levers
pivoted to the frame. The frame is attached to
the governor spindle and therefore rotates with
spindle. These two bell crank levers having two
balls on the one end of the lever and a roller to
the other end which is in contact with sleeve. A
compressed helical spring exerts equal
downward forces on the sleeve through collar.
The spring force is adjusted by a nut as per
requirement provided at the top of the spindle.
 Hartung Governor
This is also a spring loaded type governor. In this
type of governor, the vertical arms of the bell
crank levers are fitted with spring balls which
compress against the frame of the governor
when the rollers at the horizontal arm press
against the sleeve.
 Wilson-Hartnell Governor
In this governor the fly balls are connected by a
spring in. An auxiliary spring is attached to the
sleeve mechanism through a lever; due to this
auxiliary the equilibrium speed of a given radius
may be adjusted.
  Pickering Governor
A Pickering governor is mostly used for driving
gramophone. It consists of three straight leaf
springs arranged at equal angular intervals
round the spindle. Each spring carries a weight
at the centre. The upper end of the spring is
attached to the nut fixed on the spindle;
whereas the lower ends of the spring are
attached to a sleeve which is free to slide on
the spindle. As the spindle speed increases
the weights moves outwards and the spring bends, and the spring rotates about
the spindle. A stop is provided for adjusting the movement of the leaf springs.

 Sensitiveness of Governors
Consider two governors A and B running at the same speed. When there is
change in speed increase or decrease by a certain amount, the lift of the sleeve
of governor A is greater than the lift of the sleeve of governor B. Then we can
say that the governor A is more sensitive than the governor B. Thus more the
movement of sleeve for a small change in speed more will be the sensitiveness.
The sensitiveness is defined as the ratio of the difference between the max. and
min. speeds to the mean equilibrium speed.

 Stability of Governors
A governor is said to be stable when for every speed within the working
range there is a definite configuration i.e. there is only one radius of rotation of
the governor balls at which the governor is in equilibrium. For a stable governor
when the equilibrium speed increases, the radius of governor balls must also
increase. {A governor is said to be unstable, if the radius of rotation decreases
as the speed increases.}

 Isochronous Governors
A governor is said to be isochronous when the equilibrium speed is
constant for all radii of rotation of the balls within the working range, neglecting
friction. The isochronous is the stage of infinite sensitivity.
The isochronous governor is not of practical use because the sleeve will
move to one of its extreme positions immediately the peed deviates from the
isochronous speed.

 Hunting of Governor
A governor is said to be hunt, when the speed of the engine fluctuates
continuously above and below the mean speed. This is caused by a too sensitive
governor which changes the fuel supply by a large amount when a small change
in the speed of rotation takes place.
As when the load on the engine increases, the engine speed decreases
and, if the governor is very sensitive, the governor sleeve immediately falls to
its lowest position. Due to this will the fuel supply through throttle valve to the
engine will be excess than the requirement and, hence engine speed rapidly
increases and the governor sleeve rises to its highest position. Due to this
movement of the sleeve, the control valve will cut off the fuel supply to the
engine and the engine speed decreases again. Same will happen again.
Such a governor may provide the max. or min. amount of fuel. And the
effect of this will be to cause wide fluctuations in the engine speed i.e. in other
words, the engine will hunt.
 Effort of Governor
The effort of a governor is the mean force exerted at the sleeve for a
given percentage change of speed or lift of the sleeve. OR the effort of governor
is the mean speed force required on the sleeve to raise or lower the sleeve.
When the governor is running at constant speed, there is no force at the
sleeve. But, when the speed changes, there is a resistance at the sleeve which
opposes its motion. It is assumed that this resistance which is equal to the
effort.

 Power of Governor
The power of a governor is the work done at the sleeve for a given
percentage change of speed. It is the product of the mean value of the effort
and the distance through which the sleeve moves.
Power = Mean effort × lift of sleeve

 Controlling Force
When a body rotates in a circular path, there is an inward radial force or
centripetal force acting on the body. When the governor running at a steady
(constant) speed, the inward force acting on the rotating balls is known as
controlling force. This force is equal and opposite to the centrifugal force.
Controlling force, FC = m.ω2.r
The controlling force is provided by the weight of the sleeve and balls as
in Porter governor and by the spring and weight as in Hartnell governor (or
spring controlled governor).
Centrifugal Governor:
In centrifugal governors, multiple masses know as governor balls, are responsible
to revolve about the axis of a shaft, which is driven through suitable gearing from
the engine crankshaft. Each ball is acted upon by a force which acts in the radially
inward direction and is provided by dead weight, a spring or a combination of
two. This force is commonly called as the controlling force and it will increase as
the distance of the ball from the axis of rotation increases. The inward or outward
movement of the ball is transmitted by the governor mechanism to the valve
which controls the amount of energy supplied to the engine.

Inertia Governor:
In inertia governors, the balls are arranged in manner that the inertia forces
caused by angular acceleration or retardation of the governor shaft tend to
change their position. The obvious advantage of inertia governor lies in its rapid
response to the effect of a change of load. This advantage is small, however by
the practical difficulty of arranging for the complete balance of the revolving parts
of the governor. For this reason Centrifugal governors are preferred over the
inertia governors.

State the function of governor.

Explain the following terms of centrifugal governor with neat sketch:
(i) Height of governor , (ii) Equilibrium speed , (iii) Sleeve lift
Define the sensitivity in relation to governor.
Draw neat sketch of centrifugal Governor. / Explain the construction and working
of centrifugal governor with the help of neat sketch.
Explain the working of Watt governor with neat diagram.
Compare flywheel with Governor.