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AKTU B. Tech I-Year

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Semester -I & II Common to All Branches

Fundamentals of Mech. Engg.(BME101/201)

UNIT-2 : IC Engines & Electric Vehicles

Gateway Series for Engineering

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AKTU B. Tech I-Year

Gateway Classes
Fundamentals of Mech. Engg.(BME101/201)

Unit-2
Introduction to IC Engines & Electric Vehicles
Syallbus
IC Engine: Basic definition of engine and Components, Construction
and Working of Two stroke and four stroke SI & CI engine, merits
and demerits, scavenging process; difference between two-stroke
and four stroke IC engines and SI and CI Engines.

Electric vehicles and hybrid vehicles: Components of an EV, EV

batteries, chargers, drives, transmission and power devices.
Advantages and disadvantages of EVs. Hybrid electric vehicles,
HEV drive train components, advantages of HV.

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 Engine : definition

 It is a device which converts one form of energy into another

form of useful energy.

Fuel Engine
Chem. Energy Thermal Energy Mech. Energy
Burning

Based on combustion engines are classified into

 Internal Combustion Engine (I.C. Engine)

 External Combustion Engine (E.C. Engine)

 Internal Combustion Engine [Sem Exam]

 In internal combustion engine the burning or combustion of the fuel takes place inside the
cylinder.

Example-Automobile Engines
 Petrol engine
 Diesel engine
 External Combustion Engine

 In external combustion engine the combustion of the fuel takes place outside
the engine.

Example- Steam Engine, Closed gas turbine etc.

 Differences between ICE and ECE

𝑺. 𝑵𝒐. 𝑬𝑪 𝑬𝒏𝒈𝒊𝒏𝒆 𝑰𝑪 𝑬𝒏𝒈𝒊𝒏𝒆

𝟏 𝑪𝒐𝒎𝒃𝒖𝒔𝒕𝒊𝒐𝒏 𝒐𝒇 𝒇𝒖𝒆𝒍 𝒊𝒔 𝒐𝒖𝒕𝒔𝒊𝒅𝒆 𝑪𝒐𝒎𝒃𝒖𝒔𝒕𝒊𝒐𝒏 𝒐𝒇 𝒇𝒖𝒆𝒍 𝒊𝒔 𝒊𝒏𝒔𝒊𝒅𝒆

𝒕𝒉𝒆 𝒆𝒏𝒈𝒊𝒏𝒆 𝒕𝒉𝒆 𝒆𝒏𝒈𝒊𝒏𝒆
𝟐 𝑩𝒖𝒍𝒌𝒚 𝒅𝒖𝒆 𝒕𝒐 𝒑𝒓𝒆𝒔𝒆𝒏𝒄𝒆 𝒐𝒇 𝒂𝒖𝒙𝒊𝒍𝒊𝒂𝒓𝒚 𝑰𝒕 𝒊𝒔 𝒍𝒊𝒈𝒉𝒕 𝒂𝒏𝒅 𝒄𝒐𝒎𝒑𝒂𝒄𝒕
𝒂𝒑𝒑𝒂𝒓𝒂𝒕𝒖𝒔 𝒍𝒊𝒌𝒆 𝒃𝒐𝒊𝒍𝒆𝒓 𝒂𝒏𝒅 𝒄𝒐𝒏𝒅𝒆𝒏𝒔𝒆𝒓

𝟑 𝑯𝒊𝒈𝒉 𝒓𝒂𝒕𝒊𝒐 𝒐𝒇 𝒘𝒆𝒊𝒈𝒉𝒕 𝒕𝒐 𝒑𝒐𝒘𝒆𝒓 𝒐𝒖𝒕𝒑𝒖𝒕 𝑳𝒐𝒘 𝒓𝒂𝒕𝒊𝒐 𝒐𝒇 𝒘𝒆𝒊𝒈𝒉𝒕 𝒕𝒐 𝒑𝒐𝒘𝒆𝒓 𝒐𝒖𝒕𝒑𝒖𝒕

𝟒 𝑰𝒕 𝒄𝒂𝒏 𝒖𝒔𝒆 𝒄𝒉𝒆𝒂𝒑𝒆𝒓 𝒇𝒖𝒆𝒍𝒔 𝒊𝒏𝒄𝒍𝒖𝒅𝒊𝒏𝒈 𝑯𝒊𝒈𝒉 𝒈𝒓𝒂𝒅𝒆 𝒇𝒖𝒆𝒍𝒔 𝒂𝒓𝒆 𝒖𝒔𝒆𝒅 𝒘𝒊𝒕𝒉
𝒔𝒐𝒍𝒊𝒅 𝒇𝒖𝒆𝒍𝒔 𝒑𝒓𝒐𝒑𝒆𝒓 𝒇𝒊𝒍𝒕𝒓𝒂𝒕𝒊𝒐𝒏
𝟓 𝑯𝒊𝒈𝒉𝒆𝒓 𝒓𝒆𝒒𝒖𝒊𝒓𝒆𝒎𝒆𝒏𝒕 𝒐𝒇 𝒘𝒂𝒕𝒆𝒓 𝒇𝒐𝒓 𝑳𝒆𝒔𝒔𝒆𝒓 𝒓𝒆𝒒𝒖𝒊𝒓𝒆𝒎𝒆𝒏𝒕 𝒐𝒇 𝒘𝒂𝒕𝒆𝒓
𝒅𝒊𝒔𝒔𝒊𝒑𝒂𝒕𝒊𝒐𝒏 𝒐𝒇 𝒉𝒆𝒂𝒕
𝟔 𝑳𝒐𝒘𝒆𝒓 𝒆𝒇𝒇𝒊𝒄𝒊𝒆𝒏𝒄𝒚 𝑯𝒊𝒈𝒉𝒆𝒓 𝒆𝒇𝒇𝒊𝒄𝒊𝒆𝒏𝒄𝒚

𝟕 𝑺𝒊𝒍𝒆𝒏𝒕 𝒐𝒑𝒆𝒓𝒂𝒕𝒊𝒐𝒏 𝒅𝒖𝒆 𝒕𝒐 𝒐𝒖𝒕𝒔𝒊𝒅𝒆 𝑽𝒆𝒓𝒚 𝒏𝒐𝒊𝒔𝒚 𝒐𝒑𝒆𝒓𝒂𝒕𝒆𝒅 𝒆𝒏𝒈𝒊𝒏𝒆

𝒄𝒐𝒎𝒃𝒖𝒔𝒕𝒊𝒐𝒏
 Advantages of an I.C. Engine

These are the following advantages of an I.C. Engine

1. Mechanical Simplicity

2. Low initial cost due to absence of boiler, turbine condenser etc.

3. High efficiency than external combustion engine

4. Power to weight ratio is high

5. Very suitable for small power requirement applications

6. Starting time is very less

7. Requires less maintenance

 Dis-advantages of an I.C. Engine

These are the following disadvantages of an I.C. Engine

1. Variety of fuels that can be used is limited to very fine quality gaseous and liquid fuel.

2. Fuel used is very costly like gasoline or diesel.

3. Engine emissions are generally high compared to external combustion engine.

4. Not suitable of large scale power generation.

5. In case of reciprocating internal combustion noise is generated due to detonation.

 Classification of an I.C. Engine

1. On the basis of strokes used

 Two Stroke cycle Engines
 Four Stroke Cycle Engines

2. On the basis of cycle used

 Otto Cycle Engines
 Diesel Cycle Engines
 Dual Cycle Engines

3. On the basis of types of fuel used

 Petrol Engines
 Diesel Engines
 Gas Engines
4. On the basis of types of Ignition Method :
 Spark Ignition (SI)
 Compression Ignition (CI)

5. On the basis of types of cooling system used:

 Air cooled engines
 Water cooled engines

5. On the basis of number of cylinders used:

 Single cylinder engines
 Multi cylinders engines
6. Classify the IC engine on the basis of l/d ratio. Sem Exam
 Long-stroke engines
• These engines have a relatively long stroke compared to the bore diameter.
• Have an l/d ratio greater than 1.
 Square engines
• Square engines have an l/d ratio close to 1, which means the stroke length is roughly
equal to the bore diameter.
 Short-stroke engines
• These engines have a shorter stroke compared to the bore diameter.
• Have an l/d ratio less than 1.

7. On the basis of types of different position of cylinder :

 Horizontal cylinder engines
 Vertical cylinder engines
 Inclined cylinder engines
Main Components of an I.C.E.
Main Components of an I.C.E. [AKTU : 2021-22,23]
 Cylinder Block: The foundation of the engine, housing the cylinders where the
combustion process occurs.
It is made of cast iron or aluminum.

Cylinders: These are cylindrical chambers where the combustion of fuel and air takes place. It is
made of cast iron or aluminum.
Pistons: Pistons are cylindrical components that move up and down inside each cylinder. The
pressure created by the combustion process forces the pistons down, converting the pressure into
mechanical motion. It is made of aluminum alloy, sometimes with steel reinforcement.
Crankshaft: The crankshaft is a rotating shaft connected to the pistons through connecting rods. It
converts the linear motion of the pistons into rotational motion, which is then used to drive the
wheels of the vehicle. It is made of forged steel or nodular cast iron.
Camshaft(s): The camshaft controls the opening and closing of intake and exhaust valves. It is
made of steel or cast iron .It is synchronized with the crankshaft and is responsible for timing the
engine's valve operation.
Valves: Valves are responsible for allowing the intake of air and fuel into the
combustion chamber (intake valve) and expelling the exhaust gases (exhaust valve)
after combustion. These are made of stainless steel .
Combustion Chamber: The area inside the cylinder where the air and fuel mixture is
ignited by a spark plug (in petrol engines) or by compression (in diesel engines).
Spark Plugs: In gasoline engines, spark plugs are used to ignite the air-fuel mixture in the
combustion chamber, creating the controlled explosion that drives the piston down. It is
made of Ceramic insulator with metal electrodes
Intake and Exhaust Manifolds: These are pathways that direct the intake air and fuel
mixture into the cylinders and expel the exhaust gases out of the engine, respectively.
Fuel Injection/Carburetor System: The system responsible for mixing air and fuel in the
right proportion before it enters the combustion chamber. Older engines use carburetors,
while modern ones use fuel injection systems.
 IC Engine Terminology [AKTU : 2021-22]

Top-Dead-Center (TDC): It is position of the piston when it is

farthest from the crank shaft.

Bottom-Dead-Center (BDC): It is the position of the piston

when it is nearest to the crankshaft.

Stroke: When piston moves from TDC to BDC or BDC to TDC

is known as stoke.

Stroke Length (L): It is the distance between TDC and BDC.

Bore (D): Inner diameter of the cylinder or diameter of the

piston face.
 IC Engine Terminology [AKTU : 2021-22]

Swept Volume (VS): Volume displaced by the piston as it

travels through one stroke.
𝝅
𝑽𝒔 = 𝟒 𝑫𝟐𝑳
𝝅 𝟐
Total swept 𝑽𝒔 = 𝑲 𝑫𝑳
𝟒

Where K = no. of cylinders

Clearance Volume (VC): It is the volume of the cylinder when

piston is at TDC, therefore it is minimum volume.

Compression ration (r): It is defined as the ratio of volume before compression to the volume of after
compression.

Volume before compression = VC + VS

Volume after compression = VC

 Four Stroke Engines

 If a Cycle of an engine is completed in FOUR strokes of the

piston or TWO revolution (720o) of the crank is known as four
stroke engine.

 Cycle consists of processes i.e. Intake, Compression,

Expansion and Exhaust.

 Four Stroke Engines may be SI or CI.

 SI engines work on Otto cycle

 CI engines work on Diesel cycle

 Four Stroke Engines

 If a Cycle of an engine is completed in FOUR strokes of

the piston or TWO revolution (720o) of the crank is known
as four stroke engine.

 Cycle consists of processes i.e. Intake, Compression,

Expansion and Exhaust.

 Four Stroke Engines may be SI or CI.

 SI engines work on Otto cycle

 CI engines work on Diesel cycle

Working of Four Stroke SI Engines(Petrol Engine) [SEM EXAM]
P-V and T-s diagrams for Otto Cycle : SI Engine
 Working of Four Stroke SI Engines [AKTU : 2021-22]
The working of a four-stroke spark-ignition (SI) engine involves four strokes:
1. Intake
2. Compression
3. Power
4. Exhaust.
These strokes are repeated in a continuous cycle to produce power
1.Intake Stroke (Suction)
 Piston moves downward from TDC to BDC.
 Inlet valve is opened and the exhaust valve is closed.
 Pressure inside the cylinder is reduced below the atmospheric pressure.
 The mixture of air-fuel is sucked into the cylinder through the inlet valve.
 The timing of the intake valve is controlled by the camshaft, which is synchronized with
the engine's rotation.
2. Compression Stroke:
 Compression Stroke:
 Piston moves up from BDC to TDC.
 Both inlet and exhaust valves are closed.
 Temperature and pressure increased due to compression of air
 fuel mixture in the cylinder.
 At the end of compression combustion starts with spark plug.
3. Power Stroke (Expansion):
 The burning gases expand rapidly.
 Gases exert an impulse (thrust or force) on the piston.
 The piston is pushed from TDC to BDC.
 This linear motion of the piston is converted into rotary motion of the crankshaft
through connecting rod.
 Both inlet and exhaust valves are closed.
4. Exhaust Stroke:
 Piston moves upward from BDC to TDC.
 Exhaust valve is opened and the inlet valve is closed.
 The burnt gases are forced out to the atmosphere through the exhaust
valve.
 The inlet valve opens slightly before TDC and the cylinder is ready to
receive fresh charge to start a new cycle.

After the exhaust stroke, the cycle repeats, and the engine continues to
operate as long as there is a supply of air-fuel mixture and a spark to ignite it.
Working of Four Stroke CI Engines(Diesel Engine) [Sem Exam]
P-V and T-s diagrams for Diesel Cycle : CI Engine
 Working of Four Stroke CI Engines [AKTU : 2020-21]
The working of a four-stroke spark-ignition (SI) engine involves four strokes:
1. Intake
2. Compression
3. Power
4. Exhaust.
These strokes are repeated in a continuous cycle to produce power
1.Intake Stroke (Suction)
 Piston moves from TDC to BDC.
 Inlet valve is opened and the exhaust valve is closed.
 When piston moves from TDC to BDC ,the pressure inside the cylinder is reduced below the
atmospheric pressure.
 Fresh air from the atmosphere is sucked into the engine cylinder through air cleaner and
inlet valve.
2. Compression stroke:
 Piston moves from BDC to TDC.
 Both inlet and exhaust valves are closed.
 The only air is drawn during suction stroke is compressed to a high pressure
and temperature.

 3. Power Stroke (Expansion):

 Fuel (diesel) is injected inside the cylinder with the help of fuel injector.
 The burning gases expand rapidly and push the piston from TDC to BDC.
 This linear motion of piston is converted into rotary motion of the crank shaft
through connecting rod.
 Both inlet and exhaust valves are closed.
Exhaust Stroke:
 Piston moves from BDC to TDC.
 Exhaust valve is opened the inlet valve is closed.
 The burnt gases are forced out to the atmosphere through the exhaust valve.
 The inlet valve opens slightlybefore TDC and the cylinder is ready to receive
fresh air to start a new cycle.

After the exhaust stroke, the cycle repeats, and the engine continues to operate as
long as there is a supply of air-fuel mixture and a spark to ignite it.
 Differences between SI and CI Engines [AKTU : 2021-22,2022-23]
S. SI Engine CI Engine
No.
1 It works on OTTO Cycle or constant It works on DIESEL Cycle or
volume heat addition. constant pressure heat addition.
2 During the intake or suction process, air During the intake or suction process, only
and fuel are used. air is used.
The fuel used Petrol which is highly volatile. The fuel used Diesel which is low volatile.
3 Self Ignition temperature is high. Self- ignition temperature is low.
4 The fuel is supplied by Carburetor. The fuel is supplied by Injector.
5 The maintenance cost is low. The maintenance cost is high.
6 It is used in Small Vehicles. It is used in Heavy Vehicles.
7 The compression ratio is 6 to 10. The compression ratio is 16 to 22.
8 The starting of this engine is easy. Starting is a little difficult
comparatively SI engine.
9 It produces less noise. It produces high noise.
10 Lower thermal efficiency because of the low High thermal efficiency because of the high
compression ratio. compression ratio.
 TWO Stroke Engines

 If a Cycle of an engine is completed in TWO strokes of

the piston or ONE revolution (360o) of the crank is
known as four stroke engine.

 Cycle consists of processes i.e. Intake, Compression,

Expansion and Exhaust.

 Two Stroke Engines may be SI or CI.

 SI engines work on Otto cycle
 CI engines work on Diesel cycle
TWO Stroke Vs FOUR Engines
 Working of Two-Stroke SI Engines [Univ Exam]

Working
 The working of a two-stroke spark-ignition (SI)
engine involves a simpler cycle compared to a
four-stroke engine.

 It completes one power cycle in just two

strokes of the piston.

 These engines are commonly used in small

applications like motorcycles, scooters etc.
1.Intake and Compression:

 The piston moves from (BDC) to (TDC).

 Both transfer and exhaust ports are covered by the piston.
 Air fuel mixture which is already transferred into the cylinder is compressed by
moving piston.
 The pressure and temperature increases at the end of compression.
 As piston almost reaches the top dead center. The air fuel mixture inside the
cylinder is ignited by means of an electric spark produced by a spark plug.
 At the same time, the inlet port is uncovered by the piston. Fresh air fuel mixture
enters the crankcase through the inlet port.
2. Power and Exhaust:
 The burning gases expand in the cylinder. The burning gases force the piston
to move down. Thus useful work is obtained.
 When the piston moves down, the air fuel mixture in the crankcase is partially
compressed.
 This compression is known as crank case compression.
 At the end of expansion, exhaust port is uncovered. Burnt gases escape to the
atmosphere. Transfer port is also opened.
 Working of Two Stroke CI Engines [Sem exam]

Working
 The working of a two-stroke compression-
ignition (CI) engine involves a simpler cycle
compared to a four-stroke engine.

 It completes one power cycle in just two

strokes of the piston.

 These engines are commonly used in small

applications like motorcycles, scooters etc.
 Working of Two Stroke CI Engines [Univ Exam]

1.Intake and Compression:

 The piston moves from (BDC) to (TDC).

 Both transfer and exhaust ports are covered by the piston.
 Air which is already transferred into the cylinder is compressed by moving piston.
 The pressure and temperature increases at the end of compression.
 Piston almost reaches the top dead center. The fuel is injected into the hot
compressed air inside the cylinder.
 The fuel mixed with hot air and burns.
 The admission of fresh air into the crankcase continues till the
 piston reaches the top dead center.
2. Power and Exhaust:

 The burning gases expand in the cylinder.

 Burning gases force the piston to move down. Thus useful work is obtained.
 At the same time, the air in the crank case is compressed partially by the
movement of the piston from TDC to BDC.
 At the end of expansion, the exhaust port is uncovered.
 The burnt gases escape to the atmosphere through the exhaust port.
 Scavenging process [AKTU : 2020-21]

Scavenging:
 Scavenging is a process of pushing exhaust
gases out of the cylinder.
 One of the critical aspects of two-stroke engine
design is scavenging, which involves replacing
the exhaust gases with fresh air-fuel mixture to
optimize combustion efficiency.

 The charge (air fuel mixture or air) enters the

engine cylinder from the crank case at a
pressure higher than the exhaust gases.
 Differences between 4 strokes and 2 strokes engines [Univ Exam]

S. No. 4-Stroke Engine 2-Stroke Engine

1 Four stroke of the piston and two revolution Two stroke of the piston and one revolution
of crankshaft of crankshaft
2 One power stroke in every two revolution One power stroke in each revolution of
of crankshaft crankshaft
3 Power produce is less Theoretically twice power
4 Heavier flywheel due to non-uniform Lighter flywheel due to more uniform
turning movement turning movement
5 Lesser cooling and lubrication requirements Greater cooling and lubrication requirements

6 Contains valve and valve mechanism Contains ports arrangement

Volumetric efficiency and Thermal efficiency Volumetric efficiency and Thermal efficiency
7 are are
high but mechanical efficiency is low. low but mechanical efficiency is high.
8 Heavy and bulky Light and compact
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