A governor is a system that is used to maintain the mean speed of an engine, within certain limits, under fluctuating load conditions. It does this by regulating and controlling the amount of fuel supplied to the engine.

1. LNCT GROUP OF COLLEGES
Name of Faculty: Prem Kumar Soni
Designation: Assistant Professor
Department: Mechanical Engineering
Subject: Theory of Machines (403)
Unit: 6
1
Lecture – I
Governor
Topics
1. Definition
2. Difference between Flywheel and Governor
Definition
Governor as speed control device as its main function is to control the mean speed
regardless of load variations.
Concept of Governor
A governor, or speed limiter or controller, is a device used to measure and regulate the
speed of a machine, such as an engine.
A classic example is the centrifugal governor, also known as the Watt or fly-ball governor
on a reciprocating steam engine, which uses the effect of inertial force on rotating weights
driven by the machine output shaft to regulate its speed by altering the input flow of steam.
Governors can be used to limit the top speed for vehicles, and for some classes of vehicle
such devices are a legal requirement. They can more generally be used to limit the
rotational speed of the internal combustion engine or protect the engine from damage due
to excessive rotational speed.
As we know that as the load on engine increases, its speed decreases. Therefore, it is
mandatory to increase the supply of fuel. In the other case, as the load on engine decreases,
its speed increases which in turn require less supply of fuel. So, the governor automatically
maintains the supply of fuel despite of varying load conditions and this keep the mean
speed constant. The governors are mainly classified as centrifugal governors, Pickering
and inertia governors.
Application of Governor
1. Governors are mostly used in steam turbines and water turbines.
2. They are used to limit the rotational speed of internal combustion engines.
3. Today, BMW, Audi, Jaguar, Mercedes all have speed limiters that protect engines
from damage due to excessive rotational speed and thus limit the top speed.

2. LNCT GROUP OF COLLEGES
Name of Faculty: Prem Kumar Soni
Designation: Assistant Professor
Department: Mechanical Engineering
Subject: Theory of Machines (403)
Unit: 6
2
Difference between Flywheel and Governor
S. No. Flywheel Governor
1
Flywheel is used to prevent
fluctuation of energy and does not
maintain a constant speed.
Governor is used to maintain the
constant speed, whenever there are
changes in load.
2
Generally, flywheel is a heavy part
of the machine.
Governor is a lighter in weight than
flywheel.
3 It is a rotating component. It is a non-rotating component.
4
Energy generated due to flywheel
is directly proportional to the
square of its angular speed.
There is no such proportionality or
equation in a governor.
5
As there are energy variations in
engines, a flywheel results in a
maintaining a constant speed of
crankshaft in each cycle by supply
the required energy to the
preparatory stokes (other than
power stroke).
As the load on engine increases, the
speed decreases. This increases the
flow of fuel for regulating constant
speed.
6
While storing energy, rotational
speed increases and during
supplying of energy speed
decreases.
Under all fluctuating load
conditions mean speed is regulated.
7
The moment of inertia of flywheel
is very large.
The moment of inertia is very
small.
8 It doesn’t control the fuel supply. It controls the fuel supply.

3. LNCT GROUP OF COLLEGES
Name of Faculty: Prem Kumar Soni
Designation: Assistant Professor
Department: Mechanical Engineering
Subject: Theory of Machines (403)
Unit: 6
3
Difference between Flywheel and Governor
Basics of Flywheel and Governor
Both are mechanical devices used for speed regulation/control to compensate for speed
variations but with different point of impact. A flywheel maintains a constant speed under
different load conditions for each thermodynamic cycle. A governor, on the other hand, also
controls the engine operation and its main speed but the means is different from that of a
flywheel.
Function of Flywheel and Governor
The flywheel stores excess of rotational energy for intermittent use. It stores energy when the
supply is more than what’s required for the operation and releases the same when the supply
is less than the requirement. The governor regulates the flow of fuel to maintain a constant
mean speed throughout the cycle regardless of variations in load.
Operation of Flywheel and Governor
Flywheel is a heavy rotating metal wheel that resists changes in rotational speed providing
energy when the energy source is discontinuous. The momentum of inertia is what drives the
flywheel and it rotates at a varying angular speed. Despite energy variations, the crankshaft
runs at constant speed in each stroke of the cycle. Governor, on the other hand, controls and
maintains the speed of the engine by regulating the amount of fuel supply to the engine.
Speed of Flywheel and Governor
A flywheel rotates at a varying angular speed which increases when storing energy and
decreases when releasing the same. It absorbs mechanical energy by increasing its angular
velocity and releases the energy by decreasing the angular velocity. A governor, on the other
hand, minimizes fluctuations within the mean speed which occurs due to load variation. It
increases the fuel flow to keep the mean speed constant.
Application of Flywheel and Governor
A flywheel is more like an intra-cycle device that’s mainly used in reciprocating engines
where the energy source is variable such as in automobile engines or fabricating machines
like rolling mill, punching machines, etc. A governor, on the contrary, is like a speed-
controller device used to regulate the speed of a machine and is mostly used in vehicles,
turbine shafts, centrifugal governor, etc.