2. Group Members
• Aziz ur Rehman 17093386-001
• Muhammad Sufyan 17093386-002
• Hafiz Ali Hamza 17093386-014
• Ahmad Mushtaq 17093386-022
• Qaisar Mehmood 17093386-023
• Mehboob Arshad Jan 17093386-034
• Ramzan Ali 17093386-055
3. Content
• Heat engine
• IC engine
• Engine construction
• Valve and valve train
• Ignition system
• Fuel system
• Lubrication system
• Cooling system
5. Heat Engine
• Heat Engine is a machine which converts heat
energy supplied to it into mechanical work.
Heat energy is supplied to the engine by
burning the fuel.
• Heat engine can be classified into two type
– External combustion engine
– Internal combustion engine
6. Difference between IC and EC engine
IC engine
• Combustion of air-fuel is
inside the engine cylinder.
• It is light and compact due
to lower ratio of weight and
bulk to output.
• Higher efficiency about 35-
40%
• Less requirement of water .
• E.g. Petrol, Diesel engine
EC engine
• Combustion of air-fuel is
outside the engine cylinder.
• Higher ratio of weight and bulk
to output due to presence of
auxiliary apparatus like boiler
and condenser. Hence it is
heavy and cumbersome.
• Lower efficiency about 15-20%
• Higher requirement of water
for dissipation of energy
through cooling system .
• E.g. Steam engine
7. IC engine
• In this engine, the
combustion of air and
fuels take place inside
the cylinder and are
used as the direct
motive force.
8. Terminologies used in IC engine
• Cylinder bore (D): The nominal inner diameter of the working
cylinder.
• Piston area (A): The area of circle of diameter equal to the cylinder
bore.
• Stroke (L): The nominal distance through which a working piston
moves between two successive reversals of its direction of motion.
• Dead centre: The position of the working piston and the moving
parts which are mechanically connected to it at the moment when
the direction of the piston motion is reversed (at either end point of
the stroke).
– Bottom dead centre (BDC): Dead centre when the piston is nearest to
the crankshaft.
– Top dead centre (TDC): Dead centre when the position is farthest from
the crankshaft.
Continue…
9. Terminologies used in IC engine
• Displacement volume or swept volume (Vs): The
nominal volume generated by the working piston when
travelling from the one dead centre to next one and
given as,
Vs=A × L
• Clearance volume (Vc): the nominal volume of the
space on the combustion side of the piston at the top
dead centre.
• Cylinder volume (V): Total volume of the cylinder.
V= Vs + Vc
Compression ratio (r): r=Vs/Vc
10. Four stroke engine
• Cycle of operation completed in four strokes of the
piston or two revolution of the piston.
– Suction stroke (suction valve open, exhaust valve closed)-
charge consisting of fresh air mixed with the fuel is drawn
into the cylinder due to the vacuum pressure created by
the movement of the piston from TDC to BDC.
– Compression stroke (both valves closed)-fresh charge is
compressed into clearance volume by the return stroke of
the piston and ignited by the spark for combustion. Hence
pressure and temperature is increased due to the
combustion of fuel
Continue…
11. Four stroke engine
– Expansion stroke (both
valves closed)-high
pressure of the burnt
gases force the piston
towards BDC and hence
power is obtained at the
crankshaft.
– Exhaust stroke (exhaust
valve open, suction valve
closed)- burned gases
expel out due to the
movement of piston
from BDC to TDC.
12. Two stroke engine
• No piston stroke for suction
and exhaust operations
• Suction is accomplished by
air compressed in crankcase
or by a blower
• Induction of compressed air
removes the products of
combustion through
exhaust ports
• Transfer port is there to
supply the fresh charge into
combustion chamber
13. Types of IC engine
• According to the basic engine design
– Reciprocating engine
– Rotary engine
• According to the type of fuel used
– Petrol engine
– Diesel engine
• According to the number of strokes per cycle
– Four stroke
– Two stroke engine
Continue…
14. Types of IC engine
• According to the method of igniting the fuel
– Spark ignition engine,
– compression ignition engine
• According to the number of cylinder-
– Single cylinder
– Multi-cylinder engine
• Method of cooling-
– Water cooled
– Air cooled
16. ENGINE CONSTRUCTION
• The construction of an engine varies little,
regardless of size and design. The intended
use of the engine determines its size and
design, and the temperature at which the
engine will operate determines the type of
metal it will be built from.
17. Engine Cylinder Block
• The cylinder block is the basic
frame of a liquid-cooled engine
whether it is in-line, horizontally
opposed, or V-type. The cylinder
block is a solid casting made of
cast iron or aluminum that
contains the crankcase, the
cylinders, the coolant passages,
the lubricating passages.
• Body of an engine containing the
cylinders.
• Normally made of ALUMINUM or
CAST IRON.
• Old engine also have a case for
water jackets.
18. CAMSHAFT
• Rotating shaft used to push
open valves at proper timing
in engine cycle. Can be control
Hydraulically or mechanically.
Modern engine have more
then two cams. Rotating shaft
through which engine is work
output supply to the system. It
rotate by which work is done.
Mostly they made of forged
steel or cast iron. It is attached
with the engine block by main
bearing. Rotates in circular
motion. Having crank weights
attached with crankshaft
19. Cylinder Sleeve
• Cylinder sleeves, or liners,
are metal pipe shaped
inserts that fit into the
cylinder block. They act as
cylinder walls for the piston
to slide up and down on.
Cast iron sleeves are
commonly used in
aluminum cylinder blocks.
Sleeves can also be installed
to repair badly damaged
cylinder walls in cast iron
blocks. There are two basic
types of cylinder sleeves,
dry and wet.
20. PISTON
• A cylindrical-shaped mass
that reciprocate back and
forth in the cylinder
transmitting force to the
crankshaft. The top of the
piston is called crown and
the sides are called skirt.
Piston is made up of cast
iron, steel or aluminum.
Aluminum piston are light .
Used for light engine .
Piston is one of the
important component of IC
engine.
21. Piston rings
• These are housed in the
circumferential grooves provided
on the outer surface of the piston
and made of steel alloys which
retain elastic properties even at
high temperature. 2 types of
rings- compression and oil rings.
Compression ring is upper ring of
the piston which provides air
tight seal to prevent leakage of
the burnt gases into the lower
portion. Oil ring is lower ring
which provides effective seal to
prevent leakage of the oil into the
engine cylinder.
22. Connecting rod
• It converts reciprocating
motion of the piston into
circular motion of the crank
shaft, in the working stroke.
The smaller end of the
connecting rod is connected
with the piston by gudgeon
pin and bigger end of the
connecting rod is connected
with the crank shaft. The
special steel alloys or
aluminum alloys are used
for the manufacture of
connecting rod.
23. Cylinder Head
• The cylinder head bolts to the deck of
the cylinder block. It covers and
encloses the top of the cylinders.
Combustion chambers, small pockets
formed in the cylinder heads where
combustion occurs, are located
directly over the cylinders. Spark
plugs (gasoline engine) or injectors
(diesel engine) protrude through
holes into the combustion chambers.
Intake and exhaust ports are cast into
the cylinder head. The intake ports
route air (diesel engine) or air and
fuel (gasoline engine) into the
combustion chambers. The exhaust
port routes burned gases out of the
combustion chamber.
24. Flywheel
• It is big wheel mounted
on the crankshaft,
whose function is to
maintain its speed
constant. It is done by
storing excess energy
during the power
stroke, which is
returned during other
stroke.
26. Ignition system
• An ignition system
generates a spark or
heats an electrode to a
high temperature to
ignite a fuel-air mixture
in spark ignition internal
combustion engines.
27. Functions
• The Ignition System has three major functions that should be
perform:
– Generate a spark, capable of bridge the gap of the spark plug in the
harsh environment of the combustion chamber and ignite the mister.
– The spark needs to have the proper duration to allow all the compress
gases to burn
– The spark should be delivering on the right moment to maximize the
power and minimize the emissions
• To give the maximum cylinder pressure and therefore the maximum
horsepower, burning of the gasses must be finished by shortly after
Top Dead Center. If the piston is allowed to go too far down the
cylinder, the combustion chamber volume will have become too
big, the pressure will drop and so will the power and economy.
28. Direct ignition system
• The most common arrangement in modern
engines is an ignition coil mounted on top of
each cylinder, right on top of the spark plug,
eliminating the need of spark plug wires, since
the spark plug boot is connected directly to
the ignition coil. In either set-up, the timing is
controlled directly by the engine control
computer, either advancing it as it needs to or
retarding it if necessary.
29. Electronic ignition system
• The basic difference between the contact
point and the electronic ignition system is in
the primary circuit. The primary circuit in a
contact point ignition system is open and
closed by contact points. In the electronic
system, the primary circuit is open and closed
by the electronic control unit (ECU) that uses
sensors to identify the cycle positioning.
30. Breaking ignition system
• With the engine running, the distributor shaft
and distributor cam rotate. This action causes the
distributor cam to open and close the contact
points. With the contact points wired to the
primary windings of the ignition coil, the contact
points make and break the ignition coil primary
circuit. With the contact points closed, the
magnetic field builds up in the coil. As the points
open, the magnetic field collapses and voltage is
sent to the spark plugs.
31. Working
• Primary circuit
• The primary circuit of the ignition circuit
includes all of the components and wiring
operating on low voltage. Wiring in the
primary circuit uses conventional wire, similar
to the wire used in other electrical circuits on
the vehicle.
Continue…
32. Working
• The primary circuit consists of:
– Battery - provides the power to run the system.
– Ignition Switch - allows the driver to turn the system
on and off.
– Breaker switch - a mechanical switch that acts as the
triggering mechanism.
– Condenser - protects the points from burning out.
– Primary Coil - produces the magnetic field which
creates the high voltage in the secondary coil.
– Wires - join all the components together.
Continue…
33. Working
• Secondary circuit
• The secondary circuit of the ignition circuit is
the high voltage section. It consists of the wire
and components between the coil output and
the spark plug ground. Wiring in the
secondary circuit must have a thicker
insulation than that of the primary circuit to
prevent leaking (arcing) of the high voltage.
Continue…
34. Working
• The Secondary Circuit consists of:
– Secondary Coil - the part of the coil that creates the high voltage
electricity.
– Coil Wire - a highly insulated wire, that takes the high voltage from the
coil, to the distributor cap.
– Distributor Cap - a plastic cap which goes on top of the distributor, to
hold the high tension wires in the right order.
– Rotor - spins around on the top of the distributor shaft, and distributes
the spark to the right spark plug.
– Spark Plug Wires - another highly insulated wire that takes the high
voltage from the cap to the plugs.
– Spark Plugs - take the electricity from the wires, and give it an air gap
in the combustion chamber to jump across, to light the mixture.
Continue…
38. What is Fuel ?
• It is a substance consumed by the engine to
• produce energy
• There are some fuel used in I.C engine
– Petrol
– Power kerosene
– High speed diesel oil
– Low speed diesel oil
39. Properties of Fuel
• In compression ignition engines, the fuel is
• injected at the end of the compression stroke.
• The air alone compressed to a pressure of
about 35 Kg/cm2
• After this compression the temperature is
about 600o c.
40. Qualities of Diesel Fuel
• High speed diesel oil (HSD)
– High speed diesel oil is used for high speed diesel
engines. It is lighter than light diesel oil.
• Light diesel oil (LDO)
– Light diesel oil is the main source of fuel for slow
speed engines.
41. • For satisfactory operation, the diesel must satisfy
the following requirements;
– It must ignite readily and burn evenly.
– It should have a low viscosity so that it can be
atomized from the nozzle holes.
– It must have some lubrication qualities to operate
the valves and FI pump parts.
– It should have minimum foreign materials, otherwise,
the engine parts may rapidly wear out.
42. Working principle of fuel
System in SI ENGINE
• In some spark ignition engine, the fuel tank is
placed above the level of carburetor.
• The fuel flows from the fuel tank to the
carburetor under the action of gravity.
• There are one or two filters between the fuel
tank and the carburetor.
• Carburetor mix the air and fuel at required air-
fuel ratio according to speed and loads of the
engine.
Continue…
43. Working Principle
• Carburetor supply air-fuel mixture into inlet
manifold.
• Inlet manifold distribute air-fuel mixture into
different cylinder uniformly.
• At last the air-fuel mixture injected into the
combustion chamber.
• After combustion of fuel the unwanted
exhaust gases flow out through exhaust
manifold.
44. Components of fuel system
• The fuel supply system of SI Engine consists of;
– Fuel tank
– Fuel lift pump
– Fuel pipes
– Sediment bowl (as a fuel filter)
– carburetor
46. Fuel supply system in
diesel engine
• Fuel is drawn from the fuel tank by feed pump and
forced to the injection pump through fuel filter.
• The injection pump supplies high pressure fuel to
injection nozzles through delivery valve and high
pressure pipes.
• Fuel injected into the combustion chamber through
injection nozzles.
• The fuel that leaks out from the injection nozzles
passes out through leakage pipe and returns to the fuel
tank through overflow pipe.
• The fuel pressure at the feed pump must be in the
range of 1.5 to 2.5 kg/cm2.
47. Precaution in handling
of fuel system
• Fuel
– High quality fuel is necessary to the fuel injection
pump.
– Only filtered fuel should be supply to the fuel tank.
• Fuel tank cleaning
– Water and deposits should be drained from the fuel
tank at least every six month.
49. Cooling system
• An automobile's cooling system is the
collection of parts and substances
(coolants) that work together to maintain
the engine's temperature at optimal levels.
Comprising many different components
such as water pump, coolant, a thermostat
etc. the system enables smooth and
efficient functioning of the engine at the
same time protecting it from damage.
50. Cooling System
• An automotive cooling
system must perform
several functions.
– Remove excess from
the engine
– Maintain a constant
engine temperature
51. Types of cooling system
• Types of cooling
system are
– Liquid or indirect
cooling system.
– Air or direct cooling
system.
52. Liquid Cooled System
• A liquid is circulated around the cylinders
and absorb heat from the cylinder walls
and cylinder head.
• Coolant absorbs heat as it passes through
the engine and also lubricates the water
pump.
• Hot coolant enters the radiator in which
the heat is passed on to air that is flowing
through the radiator.
53. Advantages and Disadvantages
• Uniform cooling of cylinder,
cylinder head and valves.
• Specific fuel consumption of
engine improves by using
water cooling system.
• If we employ water cooling
system, then engine need
not be provided at the front
end of moving vehicle.
• Engine is less noisy as
compared with air cooled
engines, as it has water for
damping noise.
• It depends upon the supply
of water.
• The water pump which
circulates water absorbs
considerable power.
• If the water cooling system
fails then it will result in
severe damage of engine.
• The water cooling system is
costlier as it has more
number of parts. Also it
requires more maintenance
and care for its parts.
54. Air Or Direct Cooled System
• In air cooled system a current of air made to flow
past the outside of the cylinder barrel ,outer
surface area which has been considerably
increased by providing cooling fins.
• The amount of heat dissipated to air depends
upon:
– Amount of air flowing through the fins.
– Fin surface area.
– Thermal conductivity of metal used for fins.
55. Advantages and Disadvantages
• Radiator/pump is absent
hence the system is light.
In case of water cooling
system there are
leakages, but in this case
here are no leakages.
• Coolant and antifreeze
solutions are not
required.
• This system can be used
in cold climates, where if
water is used it may
freeze.
• Comparatively it is less
efficient.
• It is used in aero planes
and motorcycle engines
where the engines are
exposed to air directly.
