By Dr. Manusha Jagdale, ARS

1. Agricultural Training Institute,
Ahmednagar
Subject: Governor and Ignition System
Presented by
Er. Manisha Jagadale
Scientist, ICAR- NINFET, Kolkata
Training Period: 1st June – 30th June 2021
One-month Online Training
on
“Farm Power and Agricultural Mechanization”

2. Points to be covered
➢ What is Governor?
➢ Need of Governor
➢ Type of Governor
➢ Governor Regulation
➢ Difference between Governor and Flywheel
➢ Ignition System
➢ BatteryIgntion System
➢ Magneto Ignition System
➢ Working
➢ Advantages& Disadvantages of Battery Systemandmagnetoignition
➢ Comparison between Battery& Magneto System

3. Governor
➢ “ Governor is a mechanical device which maintains a uniform speed
by regulating amount of fuel entering the combustion chamber”
➢ Flywheel which minimizes fluctuations of speed within the cycle but it
cannot minimize fluctuations due to load variation.
➢ This means flywheel does not exercise any control over mean speed of the
engine.
➢ To minimize fluctuations in the mean speed which may occur due to load
variation, governor is used.

4. Need of Governor
• A governor is essential on tractor engine for reasons that load on tractor
engine is subjected to rapid variation in the field & operator cannot control rapid
change of engine speed without any automatic device.
• If load on tractor is reduced, engine would tend to race suddenly. If the load is
increased, the engine would tend to slow down abruptly. Under these circumstances, it
becomes difficult for operator to regulate always the throttle lever to meet temporary
changes in engine load.
• A governor automatically regulates engine speed on varying load condition
& thus the operator is relived off the duty of constant regulating throttle lever to
suit different load conditions.
• Governor used on tractor engine is called Variable Speed Governor & the
one used on stationary engine is called Constant Speed Governor.

5. ❖ Principle of governor:
Engine Governor is used for automatically controlling the speed of an
engine regulating the intake of fuel or injection fuel, so that engine speed
is maintained at the desired level under all conditions of loading
❖ Types of Governors
The governors may, broadly, be classified as
(i) Hit and miss system
ii) Throttle system

6. 1) Hit & Miss System
• In this system, the frequency of explosions or power strokes of engine are
regulated.
• When engine speed exceeds the rated speed the exhaust valve gets open
which prevents fresh air-fuel mixture or fuel to enter into engine cylinder
during suction stroke.
• The main principle in this method is to keep all explosions alike at
maximum intensity but to vary number of explosions per unit time,
depending upon the power requirement.

7. •A detent or latch is provided on exhaust valve push rod which prevents
valve from closing when speed is too high.
•The inlet valve remains closed as long as exhaust valve is held open.
Consequently, no charge is drawn into cylinder on suction stroke & no
power is developed in cylinder due to complete absence of fuel & as a
result speed falls.
•Thus it is found that explosions are missed intermittently but every
charge is of normal strength.
•This method is mostly used on gas engines; it is not common on other
engines.

8. 2) Throttle System:
• This system consists in controlling amount of fuel mixture or fuel during
suction stroke & there by changing explosion intensity in cylinder.
• Here the number of explosions are not reduced only intensity of
explosion is changed. There is a uniform firing in cylinder
throughout period of operation.
• A suitable butterfly valve is provided in air passage between the inlet
manifold & carburetor.
• If speed decreases, throttle remains wide open & more charge goes to
engine cylinder.
• When engine speed goes up, throttle comes to nearly closed position &
less charge goes inside engine cylinder.

9. WORKING OF GOVERNOR

10. • Following three types of governors works on the throttle system
of governing:
i) Centrifugal governor
ii) Pneumatic governor
iii) Hydraulic governor

11. Centrifugal Governor (Watt
governor)
➢ It is common on tractor &
stationary engines.
➢ It consists of spring loaded
centrifugal weights, sliding collar &
connecting rod, either to control the
throttle valve in throttle governing
system, or to actuate exhaust valve
in hit & miss system.
➢ Governor weights may be either mounted on engine crank shaft or on a shaft
positively driven by crank shaft.
➢ The sliding collar moves along axis of shaft depending upon speed of centrifugal
weights.

12. ➢ At low loads, engine speed tend to go high due to which centrifugal weights tend
to fly outward against spring tension which closes the throttle valve. As throttle
valve closes, the entry of fuel or air-fuel mixture inside engine is reduced, reducing
the engine speed.
➢ At high loads, engine speed tends to become slower & centrifugal weights come
closer due to spring tension. The contraction of the weights causes the throttle valve
open fully, & it allowing more fuel to come in the engine cylinder increasing the
speed of an engine.

13. Working of centrifugal Governor

14. •It consists of,
i) Diaphragm unit
ii) Thrust lever & controlled
iii) Flexible tube
iv) Venturi Valve
v) Control Lever
vi) Pull Button
vii) Accelerator pedal
Pneumatic governor
•This is simple device used on both carburetor & diesel engines to control
quantity of air fuel mixture or fuel depending upon the requirements of engine
at different loads

15. ➢ When engine is running at idle speed.
Accelerator Pedal is at - Rest position
Venuri Valve practically - Closed position.
➢ In this condition adequate vacuum exists in the vacuum compartment so that,
governing spring pulled into it's idling position.
➢ When accelerator Pedal is fully depressed, venturi valve gets open & only a
slight vacuum is remain in vacuum compartment. Then spring pushes control rod
to full position & engine speed increases due to increased fuel supply.
➢ To stop the engine pull button which is connected to thrust lever & control
lever is pulled, which brings the plunger of fuel injection nozzle at "Stop"
position or "No fuel delivery" position, causing the engine to stop.

16. •Governor is fitted on engine to maintain uniform speed. Even then
some variation in speed is observed at full load & no load conditions.
•In normal working, a variation of about 100 rpm is observed between
full load & no load condition for a good governor.
•“The extent of regulation done is expressed in terms of percentage called
percentage regulation. This is also called as speed drop.”
Governor Regulation

17. • Governor regulation is the variation in the engine speed between
full load & no load condition. It is always expressed as percentage of rated
speed. It is given as follows.
N1 - N2
R = -----------------
(N1 + N2)/2
Where,
R = Percentage regulation.
N1 = Speed at NO LOAD.
N2 = Speed at LOAD.
Governor regulation

18. •A new governor sometimes give trouble because of sticking parts or
paint interfering with it's operation.
•This causes engine speed to rise above & drop below governor speed,
as governor seeks it's correct speed, this is called as hunting.
Governor Hunting

19. Fly wheel Governor
Its function is to store the available
mechanical energy when it is in
excess of the load requirement and to
use it the available energy is less than
that required by the load
Its function is to regulate the
supply of fuel producing energy,
according to the load requirements
sio that at different loads almost a
constant speed is maintained.
In engine it takes care of fluctuations
of speed during thermodynamic
cycle.
In engine it takes care of
fluctuations of speed due to
variation of load over range of
working of engine
It works continuously from cycle to
cycle.
It works intermittently i.e. only
when there is change in load.
Difference between Flywheel and Governor

20. Ignition System
➢ Ignition system
- Turns the engine on andoff
- Creates a timed spark and distributes it to thecylinders
➢ The ignition system provides a high voltage spark in the combustion
chamber at the propertime.
➢ Distributes high voltage spark to each spark plug in correct sequence
➢ Times the spark so it occurs as piston is nearing top dead center
➢ Varies spark timing with load, speed, and other conditions

21. ➢ Ignition systems are mainly of twotypes
➢ Spark ignition system
➢ Compression ignition system
➢ An ignition system obeys laws of conservation ofenergy
➢ Hence it can be treated as a balance of energybetween;
➢ That provided by an externalsource
➢ That released by chemical reaction
➢ That dissipated to the surroundings as thermalenergy

22. ➢ Twotypes of spark ignition systems
-Battery
-Magneto
➢ Battery -Battery systems transforms the battery voltage and firesthe spark plug
at the correcttime.
➢ Magneto
➢ Magneto systems must produce the current, transform the voltage and
time the sparkplug
➢ Most small engines use the magnetosystem
➢ Twotypes of magneto systems:
➢ 1. Breaker point ignition 2. Solid state (electronic) ignition

23. ➢In this system, we use battery of 12 or 24 volts & this voltage is raised to an
extremely high value of 15000to 24000volts for producing aspark.
➢ Battery supplies all the electrical power to the ignition system

24. • BATTERYprovides power for system
• IGNITION SWITCH allows driver to turn ignition on andoff.
• IGNITION COIL changes battery voltage to 30,000Vduring
normal operation and has a potential to produce up to60,000V.
• SWITCHING DEVICE mechanical or electronic switch that
operates Ignition coil(Pick-up coil, Cranksensor, Cam sensor).
• SPARKPLUG uses high voltage from ignition coil to produce anarc
in the combustionchamber.
• IGNITION SYSTEMWIRES connect components.

25. ➢ As the key inserted to the ignition switch primary ignition circuit starts at
thebattery.
➢ A low voltage is supply to the ignition coil.
➢ The primary coil winding is not electrically to the secondary coil.
➢ Secondary coil have work to increase the voltage supply.
➢ This high voltage around 24000volts goes todistributer circuit.
➢ The distributer circuit have work to distribute the incoming voltage to the
different spark plugs at suitable timing.
➢ After that current jumps the plug gap, igniting the gasoline mixture.

26. Working of battery ignition system

27. ➢In this system , battery is replaced by a generator ordynamo. This generates
electricity of 6 to 12volts, which is raised to 15000t0 30000volts by an ignitioncoil.

28. • Magnets
• Points (Breaker pointonly)
• Trigger coil
• Conductors
• Spark plug
• Condenser (Breaker pointonly)
• Lamination stack
• Primary winding
• Secondary winding

29. e.
➢ As magnets in flywheel rotate past the
magneto, the pointsclose
➢ The magnetic flux of themagnets the
flywheel induces a current in the primary
coil.
➢ With current flowing inthe
primary circuit, a magnetic field
develops around the primary coil.
➢ This magnetic field also surrounds the secondarycoil.
➢ As the flywheel continues to rotate the breaker points open.

30. ➢ When the breaker points open the magnetic field produced by the current in
the primary windingcollapses.
➢ The collapsing magnetic field flows across the secondary coil which induces a
current in the secondarycoil.
➢ Because there is a 60:1 ratio of windings in the two coils, the voltage is
transformed to the 10,000and 15,000volts needed to fire the sparkplug.

31. ADVANTAGES
•Initial cost of systemis low
•It offers bettersparksat low speedsand at the starting of engine
•Disadvantages
•At High speeds,sparkvoltage decreases
•Because of batterybulk of systemis high

32. Advantages
•Systemisreliableas no batteryis present
•Systemismore suitable for medium and high speeds
Disadvantages
•At low speedsand during cranking the voltage isvery low
•The powerful sparksat high speedscause burning of
electrodes