Engine Types of Engine Parts of IC Engine Working Principle of  Four Stroke Petrol Engine Working Principle of Four Stroke Diesel engine Comparisons Between Petrol and Diesel Engines Working Principle of  Two Stroke Petrol Engine Comparisons of Two Stroke and Four Stroke Engines Classification of IC Engines Power Calculation Terminologies Indicated power (IP) Brake power (BP) Indicated thermal efficiency (Ƞith) Brake thermal efficiency(Ƞbth) Mechanical

1. Internal
Combustion
Engine
By: Prof. Siddesh Kumar N M
Department of Mechanical Engineering
PES College of Engineering
Mandya

2. Content
Engine
Types of Engine
Parts of IC Engine
Working Principle of Four Stroke Petrol Engine
Working Principle of Four Stroke Diesel engine
Comparisons Between Petrol and Diesel
Engines
Working Principle of Two Stroke Petrol Engine
Comparisons of Two Stroke and Four Stroke
Engines
Classification of IC Engines
Power Calculation Terminologies
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Prof. Siddesh Kumar N M PESCE Mandya

3. Engine
Engine is a device
which converts one
form of energy into
other form of energy.
Heat engine is a
device which converts
heat energy into
mechanical energy
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4. Types of engine
• Internal Combustion Engine (IC
engine)
• External Combustion Engine
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5. Parts
of
IC
Engine
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6. Working Principle of four
Stroke Petrol Engine
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7. Working
Principle of
four Stroke
Petrol Engine
As the name suggest the Four Stroke Petrol
Engine uses a cycle of four strokes and
petrol as the fuel.
Each cycle includes 2 rotations of the
crankshaft and four strokes, namely:
1.Suction Stroke
2.Compression Stroke
3.Combustion Stroke also called Power
Stroke
4.Exhaust Stroke
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8. Petrol Engine
works on otto
cycle
• A-B - Constant Pressure
Process
• B- C - Isentropic
Compression Process
• C - D - Constant Volume
Heat Addition Process
• D - E - Isentropic Expansion
Process
• E - B - Constant Volume
Heat Rejection Process
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9. Working of 4 Stroke Petrol Engine
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10. Suction stroke
• During suction stroke the inlet valve is opened and
exhaust valve is closed
• Piston moves from Top Dead Centre (TDC ) to Bottom
Dead Centre (BDC)
• The crank will moves from 0 degree to 180 degree
• The fresh air fuel mixture enters into the cylinder because
of the pressure difference due to the vacuum creation
from carburetor
• Carburetor is a device which will mix the air fuel
• The AB line in the PV diagram represents the suction
stroke
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11. Compression stroke
• During Compression stroke the both inlet and exhaust
valves are closed
• Piston moves from Bottom Dead Centre (BDC) to Top
Dead Centre (TDC )
• The crank will moves from 180 degree to 360 degree
• The mixture of fuel and air will get compressed and
pressure increases
• At the end of the stroke the spark plug ignites the fire, as
the ignition takes places at constant volume otto cycle is
also called as constant volume heat addition cycle
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12. Power/ Working/
Expansion stroke
• During Expansion stroke the both inlet and exhaust
valves are closed
• Piston moves from Top Dead Centre (TDC ) to
Bottom Dead Centre (BDC)
• The crank will moves from 360 degree to 540 degree
• High pressure gas produced during combustion will exert
pressure on the piston and hence piston moves from
TDC to BDC
• Power will be developed.
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13. Exhaust stroke
• During exhaust stroke the exhaust valve is opened
and inlet valve is closed
• Piston moves from Bottom Dead Centre (BDC) to Top
Dead Centre (TDC )
• The crank will moves from 540 degree to 720 degree
• As the piston ascends the burnt gases are pushes out of
the cylinder
• In 4 stroke petrol engine crank shaft moves 2 rotation to
complete the one cycle
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14. Working Principle of four
Stroke Diesel Engine
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15. Working
Principle of
four Stroke
Diesel Engine
As the name suggest the Four Stroke
Diesel Engine uses a cycle of four strokes
and Diesel as the fuel.
Each cycle includes 2 rotations of the
crankshaft and four strokes, namely:
1.Suction Stroke
2.Compression Stroke
3.Combustion Stroke also called Power
Stroke
4.Exhaust Stroke
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16. Diesel Engine
works on Diesel
cycle
• A-B - Constant Pressure
Process
• B- C - Isentropic
Compression Process
• C - D - Constant
Pressure Heat Addition Process
• D - E - Isentropic Expansion
Process
• E - B - Constant Volume
Heat Rejection Process
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17. Working of 4 Stroke Diesel Engine
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18. Suction stroke
• During suction stroke the inlet valve is opened and
exhaust valve is closed
• Piston moves from Top Dead Centre (TDC ) to Bottom
Dead Centre (BDC)
• The crank will moves from 0 degree to 180 degree
• The fresh air enters into the cylinder because of the
pressure difference due to the vacuum creation from
carburetor
• The AB line in the PV diagram represents the suction
stroke
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Prof. Siddesh Kumar N M PESCE Mandya

19. Compression stroke
• During Compression stroke the both inlet and exhaust
valves are closed
• Piston moves from Bottom Dead Centre (BDC) to Top
Dead Centre (TDC )
• The crank will moves from 180 degree to 360 degree
• The air will get compressed and pressure increases
• At the end of the stroke the fuel injector injects the fuel,
the compressed air with high temperature catches the fire
when the fuel get injected. The heat addition takes at
constant Pressure. Diesel cycle is also called as constant
Pressure heat addition cycle
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20. Power/ Working/
Expansion stroke
• During Expansion stroke the both inlet and exhaust
valves are closed
• Piston moves from Top Dead Centre (TDC ) to
Bottom Dead Centre (BDC)
• The crank will moves from 360 degree to 540 degree
• High pressure gas produced during combustion will exert
pressure on the piston and hence piston moves from
TDC to BDC
• Power will be developed.
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21. Exhaust stroke
• During exhaust stroke the exhaust valve is opened
and inlet valve is closed
• Piston moves from Bottom Dead Centre (BDC) to Top
Dead Centre (TDC )
• The crank will moves from 540 degree to 720 degree
• As the piston ascends the burnt gases are pushes out of
the cylinder
• In 4 stroke Diesel engine crank shaft moves 2 rotation to
complete the one cycle
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Prof. Siddesh Kumar N M PESCE Mandya

22. Comparisions between petrol and diesel engines
Petrol Engine Diesel Engine
Petrol engine works on OTTO cycle Diesel engine works on DIESEL cycle
Air fuel mixture is introduced during suction stroke Only air is introduced during suction stroke
Spark plug is used to ignite the fuel Fuel is ignited as it comes in contact with
compressed air
Fuel consumption is more Fuel consumption is less
Compression ratio ranges from 6:1 to 10:1 Compression ratio ranges from 16:1 to 22:1
Thermal efficiency is less Thermal efficiency is more
Power developed is less due to low compression
ratio
Power developed is more due to high compression
ratio
Engine is simple in construction Engine is heavy or bulk in construction
Runs at high speed due to less weight Runs at medium speed due to robot in construction
Used in light weight vehicles like scooters and cars Used in heavy weight vehicles like trucks and buses
Can be easily started in cold weather Cannot be easily started in cold weather
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23. Working Principle of
Two Stroke Petrol Engine
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24. Working
Principle of
Two Stroke
Petrol Engine
• As the name itself indicates two stroke is
required for one working cycle
• Suction and exhaust strokes are
eliminated and these strokes
are performed at the time of compression
and working stroke are in progress
• Two stroke petrol engine works on the
pinciple of Otto cycle
• Two stroke engine consists of cylinder
fiited with one end and the other end
fitted with hermiterically sealed crankcase
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25. Working of 2 Stroke Petrol Engine
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26. Working of 2
Stroke Petrol
Engine
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27. 1st Stroke
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28. 2nd Stroke
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29. Comparisions of two stroke and four
stroke engines
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30. Comparisions of two stroke and four stroke engines
Four Stroke Engine Two Stroke Engine
Four stroke per cycle Two strokes per cycle
Number of cycles per minute is half of the speed
of the engine
Number of cycles per minute is equal to the
speed of the engine
Power stroke is obtained for every alternative
revolution of the crankshaft
Power stroke is obtained for each revolution of
the crankshaft
Heavy fly wheel is required Lighter fly wheel is required
Torque generated will not be uniform Torque generated will be uniform
Admission of charge is directly into the cylinder Admission of charge is 1st into crank then into
cylinder
Inlet and outlet valves are operated by cams Inlet and exhaust port will be operated by piston
itself
Fuel consumption is less Fuel consumption is more
Less noise More noise
Used at low speeds and high power application Used at high speeds and low power application
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31. Classification
of IC Engines
1. According to the type of fuel used
 Petrol engines - fuel used in these engines is petrol.
 Diesel engines - fuel used is Diesel.
 Gas engines - gaseous fuels like Natural gas, Biogas,
Blast furnace gas
 Bi-Fuel engines - these engines use a mixture of two
fuels.
2. According to the number of strokes per cycle
 4-stroke engine - the working cycle is completed in
four different strokes.
 2-stroke engine - the working cycle is completed in
two different strokes.
3. According to the method of igniting the fuel
Spark ignition engines
Compression ignition engine
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Prof. Siddesh Kumar N M PESCE Mandya

32. Classification
of IC Engines
4. According to the cycle of operation
Otto cycle engines,
Diesel cycle engines
Dual cycle engines
5. According to the speed of the engine
Slow speed engines
Medium speed engines
High speed engines
6. According to the cooling system
Air-cooled engines
Water-cooled engines.
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Prof. Siddesh Kumar N M PESCE Mandya

33. Classification
of IC Engines
7.According to the number of cylinders
 Single cylinder engines
 Multi-cylinder engines.
8. According to the arrangement of cylinders
 Vertical engines,
 Horizontal engines,
 Radial engines,
 In-line multi-cylinder engines,
 V-type multi-cylinder engines,
 Opposite-cylinder engines
 Opposite-piston engines.
9.According to their uses
 Automobile engine
 Marine engines
 Aircraft engine
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Prof. Siddesh Kumar N M PESCE Mandya

34. Different classifications of Engines
Prof. Siddesh Kumar N M PESCE Mandya 34
Radial Engine
V type Engine
Opposite type Engine
Single & Multi cylinder Engine

35. Power Calculation
Terminologies
Prof. Siddesh Kumar N M PESCE Mandya
Indicated power (IP)
Brake power (BP)
Indicated thermal efficiency
(Ƞith)
Brake thermal
efficiency(Ƞbth)
Mechanical
efficiency(Ƞmech)
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36. BRAKE POWER
(BP)
 The net power available at the
crankshaft is called brake power.
 The power developed inside the cylinder
is transmitted to the crankshaft through
the piston, connecting rod. crank etc.
 A fraction of the indicated power (actual
power) developed is lost due to friction of
these moving parts.
 The net power available at the crankshaft
is always less than the indicated power.
 BP = KW
Where N = speed of engine in RPM
T = Torque in N-m.
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37. Indicated power (IP)
The total power developed inside
the engine cylinder is called
indicated power.
It is denoted by IP and is
expressed in KW (Kilo watts).
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38. Mechanical efficiency(Ƞmech)
Mechanical efficiency is defined as the ratio of brake power to
indicated power
• Ղ mech = * 100
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39. Indicated
thermal
efficiency (Ƞith)
• Indicated thermal
efficiency is the ratio
of indicated power (IP) and
energy in fuel per
second(mf*CV)
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40. Brake
thermal efficiency
(Ƞbth)
• Brake thermal efficiency is
the ratio of brake power (BP)
and energy in fuel per
second(mf*CV)
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41. Working of Internal Combustion Engine
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42. Thank you
By:
Prof Siddesh Kumar N M
Assistant Professor
Department of Mechanical Engineering
PES College of Engineering
Mandya
Mail Id: siddeshkumarnm@pesce.ac.in