Internal combustion engine - introduction, types

Basic Mechanical Engineering
Unit 1: Introduction to Mechanical Engineering,
Introduction to Laws of Thermodynamics with simple examples pertaining to respective
branches, IC Engines: Classification, Applications, Basic terminology, 2 and 4 stroke IC engine
working principle,
Power Plant: Types of Power plant; Gas power plant, Thermal power plant, Nuclear power plant,
Automobiles: Basic definitions and objectives [4 hrs]
Unit 2: Design Basics, Machine and Mechanisms, Factor of safety, Engineering Materials: types
and applications, basics of Fasteners Machining and Machinability, Introduction to Lathe
machine, Drilling machine, Milling machine, basics of machining processes such as turning,
drilling and milling, Introduction to casting [4 hrs]

Internal Combustion Engine
(I C Engine)
• What is an engine?

What is an engine?
• It is a device which transfer the chemical
energy of fuel in to thermal energy & this
energy uses for producing mechanical work.

Classification
• IC Engine(Internal Combustion Engine)
• EC Engine (External Combustion Engine)

Nomenclature
1. Bore(D):It is inner diameter of engine.
2. Stroke Length(L): It is the length measured from TDC to
BDC
3. TDC(Top Dead center):It is the farthest position of piston
from Crankshaft
4. BDC(Bottom Dead Center): It is the Nearest position of
piston from Crankshaft
5. Clearance Volume(Vc):It is the volume provided between
TDC & Cylinder head to avoid striking of piston to cylinder.
6. Compression Ratio(r) : it is the ratio of vol of air incide
cylinder before compression(Vc+Vs) to the vol of air inside
cylinder after compression (Vc).
r = Vc+Vs
Vc
7. Piston Speed: It is the speed of piston while moving from
TDC to BDC & vice –versa at elevated r.p.m of crankshaft(N)
Piston Speed=2LN

Internal combustion engine - introduction, types

Main parts in IC Engine
1. Cylinder
2. Piston
3. Connecting rod
4. Crank
5. Crankshaft
6. Crankcase
7. Flywheel
Another Important Parts are;
1. Gudgeon Pin
2. Crank Pin
3. Piston Ring
4. Spark Plug/Fuel Injector
5. Water jacket/Fins
6. Inlet & Exhaust valve
7. Oil sump

Classification of IC Engine
1. According to cycle of operation:
1.Two-stroke cycle engines
2. Four-stroke cycle engines
2. According to cycle of combustion:
1.Otto cycle engine
2.Diesel cycle engine
3.Dual-combustion
3. According to the fuel employed and the method
of fuel supply to the engine cylinder:
• Petrol engine
• Diesel engine
• Oil, Gas engine

4.According to method of ignition:
1. Spark ignition (S.L) engine
2. Compression ignition (C.I.) engine
5. According to method of cooling the cylinder:
1.Air-cooled engine
2.Water-cooled engine
6. According to number of cylinders:
1.Single cylinder engine
2.Multi-cylinder engine
7.According to type of piston.
1.Rotary
2.Reciprocating.

4-Stroke Engine Working
1.Suction Stroke
2.Compression Stroke
3.Expansion/Power Stroke
4.Exhaust Stroke

Actual Working of two-stroke Engine

Comparison Between 2-Stroke & 4-Stroke Engine
Two-Stroke Engine Four-Stroke Engine
1 The Cycle is completed in tow stroke i.e. in one
revolution of crank shaft.
The Cycle is completed in Four stroke i.e. in Two
revolution of crank shaft.
2 Overlapping in operations Each operation separately
3 Its Size & weight is less It is bulky & heavy
4 Scavenging of exhaust gases is poor. Fresh
charge leaks out. So incomplete combustion &
less efficiency.
Scavenging is more effective, giving high efficiency.
5 More lubricating is required. Less lubricating is required.
6 In 2-Stroke engine provide inlet ,Exhaust port. In 4-Stroke engine Inlet & Exhaust valve are provided.
7 Thermal Efficiency is less. Thermal Efficiency is more.
8 Less Cost Due to Heavy Wt & Size Cost is more.
9 Greater Cooling is Required. Lesser Cooling is required.
10 Wear & tear is more. Wear & tear is less.
11 Power produced for same size is More Power produced for same size is Less.
12 It is used where effi.is important i.e. in
car,truck,Aeroplane,tractor etc
Used where low cost & compactness is req. like
bike,Motor cycle.

Comparison Between SI Engine & CI Engine
SI Engine CI Engine
1 It has a spark plug to ignite air-fuel Mix by
electric spark
It has a fuel injector to inject a fuel & mix is ignited by
high compression temp.
2 Fuel used petrol Fuel used Diesel
3 Compression ratio up to 9 Compression ration up to 20
4 Pr & Temp is less Pr. & temp is high
5 Light in construction Heavy in construction
6 It operates at high speed It operates at low speed
7 Starting is easy It is difficult
8 Less noise More noise
9 Initial & maintenance cost is less High Initial & Maintenance cost
10 Low efficiency High efficiency
11 It operate on Otto Cycle It operate on Diesel Cycle

Internal combustion engine - introduction, types

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