Southern University Bangladesh

Course Title: Mechanical Engineering Fundamentals

Course Teacher: Ridoanur Rahaman

Prepared by:

Anowar Hossain Rana

Topic: Internal Combustion (IC) Engines

Department of Computer Science and Engineering (CSE)

cxranabd@gmail.com www.cxrana.com

INTRODUCTION

It is an engine in which combustion of fuel take place inside the engine. When the

fuel burns inside the engine cylinder, it generates a high temperature and pressure.

This high pressure force is exerted on the piston (A device which free to moves

inside the cylinder and transmit the pressure force to crank by use of connecting

rod), which used to rotate the wheels of vehicle. In these engines we can use only

gases and high volatile fuel like petrol, diesel. These engines are generally used in

automobile industries, generation of electric power etc.

In these engines there is a sequence of processes: compression

combustion

expansion

exhaust / induction

There are two basic mechanical designs to achieve these four processes in either:

four strokes of the piston - hence the 4-stroke engine, ortwo strokes of the piston - hence 2-stroke engines.

Pictured here is an animation showing the basic mechanics of how an internal combustion engine works.

Animated graphic by Sarah Gerrity

ADVANTAGES OF I.C. ENGINE

It has overall high efficiency over E.C. engine.

These engines are compact and required less space.

Initial cost of I.C. engine is lower than E.C. engine.

This engine easily starts in cold because of it uses high volatile fuel.

Types of I.C. Engine

According to number of stroke:

Two stroke engine

Four stroke engine

According to design of engine:

Piston engine

Rotary engine

According to design of engine:

Diesel engine

Petrol engine

Gas engine

Electric engine

According to method of ignition:

Compression ignition engine

Spark ignition engine

According to number of cylinder:

Single cylinder engine

Multi-cylinder engine

According to air intake process:

Naturally aspirated

Supercharged engine

Turbocharged engine

APPLICATIONS OF IC ENGINES

I.C. engines have many applications, including:

Road vehicles(e.g. scooter , motorcycle , buses etc.)

Aircraft

Motorboats

Small machines, such as lawn mowers, chainsaws and portable engine-

generators

DIFFERENT PARTS OF I.C. ENGINE

Parts common to both diesel & petrol engine

Cylinder

Cylinder head

Piston

Piston Rings

Connecting rod

Crankshaft

Crank

Engine bearing

Crankcase

Flywheel

Governor

Valves

Parts common to Petrol engine only Spark plug

Carburetor

Parts common to Diesel engine only Injector

COMPARISON CHARTS

2 Stroke Engine 4 Stroke Engine

Its piston makes two strokes in the engine Its piston makes four strokes in the engine

Loud Quieter

Less efficient, hence environmentally unfriendly Efficient, hence environmentally friendly

Relatively cheaper as they don’t have valves Relatively expensive because of the complexity of incorporating valves

Produce high power for a relatively short period Produce low power for a long period

The extra oil required to mix with fuel makes them expensive to maintain Doesn’t require oil in the fuel

Four Stroke

ENGINE PERFORMANCE

Efficiency:Mechanical Efficiency = Brake Power (bhp)/ Engine Power (hp)

Thermal Efficiency = Engine Power (hp) / Fuel Power (hp)

Overall Efficiency = Mechancal x Thermal

An Engine is not 100% efficient (typical efficiency is about 30%). Because it

has some losses

Heat loss to cooling water 30%

Heat loss to exhaust gases 30%

Heat loss to lubricating oil 5%

Heat loss due to friction of mechanical components

5%

Useful brake power available from engine

30%

Total Heat Input to the engine 100%

THANK YOU ALL