Tractor engine

1. ENGINE
MAJOR PARTS, WORKING PRINCIPLE
AND SYSTEMS

2. Major components of engine
• Cylinder head
• Engine block
• Crank case
Exercise:- identify Parts of each major
component of engine
• Cylinder head
• Engine block
• Crank case

3. Working principle of IC engine
Four stroke engine
In four stroke engine there are four systematic strokes namely
• Induction/suction stroke
• Compression stroke
• Power stroke
• Exhaust stroke
During induction stroke piston moves to the bottom dead
centre, intake valve opens and clean air in terms of diesel
engine or fuel air mixture in terms of petrol engine passes
into the combustion chamber, exhaust valve remain closed.
By then crankshaft has moved through half revolution

4. Working principle of four stroke engine
In compression stroke the piston moves to the top dead
centre, intake and exhaust valves closed so that fuel-air
mixture or clean air is compressed in the combustion
chamber. By then crankshaft has completed one
revolution.
Power stroke fuel-air mixture is ignited by electrical spark
in diesel engine fuel is injected into the hot air within
the cylinder just before the piston has reached to the
top dead centre. Explosion occur, gases expand and
force the piston down ward. At this point crankshaft
has gone through one and half revolutions.

5. Working principle of four stroke engine..
cont
During exhaust stroke the piston moves towards
the top dead centre, exhaust valve opens and
gases escape through it . At this point
crankshaft has made two complete
revolutions

6. Working principle of two stroke engine
Two stroke engine have the following features
• They are lubricated by mixture of oil and fuel
• They have ports or ducts instead of valves
• One cycle involve one revolution of crankshaft
Working principle
During first stroke suction and compression
takes place while in second stroke combustion
and exhaust occur simultaneously

7. Working principle of two stroke engine
• First stroke (suction and compression):-Piston
moves to top dead centre and closes exhaust and
inlet ports. Mixture present in the combustion
chamber is compressed above the piston while
fresh mixture is admitted bellow the piston.
• Second stroke (combustion and exhaust):-
immediately before the piston reaches the top
dead centre fuel air mixture is ignited by spark.
The mixture explodes and pushes the piston
downward as the piston moves downward it
compresses fuel-air mixture below the piston and
at the same time the exhaust gases above the
piston are released through the exhaust port.

8. Engine Systems
• Different systems available for efficient
functioning of an engine are as follows
• Fuel system
• Cooling system
• Lubrication system
• Transition system
• Electrical system and ignition system
• Hydraulic system

9. Functions of engine systems
• Fuel system:-To supply fuel in correct ratio to the
engine
• Cooling system:-To maintain optimum
temperature of engine for efficient operation
under all conditions
– To dissipate surplus heat for protection of engine
components like cylinder, cylinder head, piston, piston
rings, and valves
– To maintain the lubricating property of oil inside engine
• Lubrication system:-To supply thin film of oil on
surfaces of moving parts on an engine in order to
reduce wear and help in sealing, cooling and
cleaning

10. Functions of engine systems cont…
• Transition system:- To transmit power
produced by engine to traction wheels. it also
provide varying speed according to the
operation being undertaken
• Electrical system:-Supply electricity for
starting the engine and lighting
• Hydraulic system:-Oil is used to transmit
power from one point to another

11. Operation mechanism of engine
systems
Fuel system
• Petrol:-Fuel from a tank is pumped into the
carburettor through filter which removes
water and sediment. The function of
carburettor is to mix fuel and air to the
proportion. This mixture is then sucked into
the engine cylinders for combustion.

12. Operation mechanism of fuel system
• Diesel:-Fuel from tank is drawn by fuel feed
pump and forced to injection pump through
fuel filters and compressed to high pressure.
This pump injects the fuel through injectors at
very high pressure into cylinder which contain
compressed air. When it comes into contact
with compressed air it ignites due to high
temperature of compressed air

13. Operation mechanism of cooling
system
• Air cooling- The cylinder of an air cooled engine
has fins to increase the area of contact of air for
speedy cooling.
• The cylinder is normally enclosed in a sheet metal
casing called cowling. The fly wheel has blades
projecting from its face, so that it acts like a fan
drawing air through a hole in the cowling and
directed it around the finned cylinder.
• For maintenance of air cooled system, passage of
air is kept clean by removing grasses etc. by a stiff
brush of compressed air

14. Operation mechanism of cooling
system
WATER COOLING SYSTEM
• Engines using water as cooling medium are
called water cooled engines. Water is
circulated round the cylinders to absorb heat
from the cylinder walls. The heated water is
conducted through a radiator to remove the
heat and cool the water.

15. Operation mechanism of lubrication
system
• There are two types of lubrication system
forced feed and splash feed lubrication
• In forced feed lubrication oil is feed under
pressure from a pump to all bearings
• In splash feed lubrication which is used mainly
in small single cylinder engines, moving parts
are lubricated by oil being splashed over them

16. Operation mechanism of ignition
system and electrical system
• The starting of engine is facilitated by ignition
system
• There are two types of ignition system
– Spark ignition system
– Compression ignition system

17. Operation mechanism of spark ignition
• Battery supplies low voltage current in the primary
circuit. The contact breakers are opened and closed
intermittently.
• When the points are open the condenser is charged
when the points close the condenser discharges. This
this causes a current of low voltage from the battery to
pass through the primary coils.
• The secondary coils then step up this low current
voltage to very high voltage. The high voltage causes a
spark to jump across electrodes of spark plug. The
distributor rotor rotates and in doing so distributes this
high voltage current from one spark plug to another
according to the firing order of the engine.

18. Firing order
• Firing order of internal combustion engine:-I
the sequence of ignition for the cylinders.
• In a spark ignition firing order correspond to
the order in which spark plugs are operated.
• In diesel engine firing order corresponds to
the order in which fuel is injected into each
cylinder

19. Operation mechanism of compression
ignition
• Fuel is ignited when air in the cylinder has
been compressed to the point where it is hot
enough to start burning.