Engine components and classification

7/21/2019 Engine components and classification

http://slidepdf.com/reader/full/engine-components-and-classification 1/44

CHAPTER 1 –ENGINE

COMPONENTS &

CLASSIFICATION



SUMMARY The topic covers basic theoretical knowledge

and understanding of engine components,

classifications and terminologies. Areas

involving engine construction, operatingprinciples and valve train



SYLLABUS Understand engine construction

Explain various types of internal combustion

engines construction and operation: twostroke petrol and diesel fourstroke petrol and diesel

rotary!"ankel

Understand basic engine terminologiesExplain basic engine terminologies such as

T#$, %#$, stroke, bore, displacement,

compression ratio etc.



Understand cylinder head and valve train

construction&tate the purpose of cylinder head

#escribe various type of valve train: '() '($

*ultivalve

Explain typical valve timing diagram

Explain basic operating principles of: )TE$

*+)E$ ))T+

$&

#))T



INTRODUCTION TO ENGINES Engine provides the power to drive the vehicle-s

wheel.

%iggest part of the engine is the cylinder block.

The cylinder block is a large casting of metalthat is drilled with holes to allow for the

passage of lubricants and coolant through the

block and provide spaces for movement of

mechanical parts.

The block contains the cylinders, which are

round passageways fitted with pistons.

The block houses or holds the maor mechanical

parts of the engine.

http://var/www/apps/conversion/tmp/Video/Chapter%201/Engine%20Assembly%20By%20FORD.flv

http://var/www/apps/conversion/tmp/Video/Chapter%201/Engine%20Assembly%20By%20FORD.flv



The cylinder head fits on top of the cylinder

block to close off and seal the top of the

cylinder.

The combustion chamber is an area into which

the airfuel mixture is compressed and burned.

The cylinder head contains all or most of the

combustion chamber. The cylinder head also contains ports through

which the airfuel mixture enters and burned

gases exit the cylinder and the bore for the

sparkplug.



The valve train is a series of parts used to

open and close the intake and exhaust ports.

A valve is a movable part that opens andcloses the ports.

A camshaft controls the movement of the

valves.

&prings are used to help close the valves.



The upanddown motion of the pistons must be

converted to rotary motion before it can drive

the wheels of a vehicle.

This conversion is achieved by linking the piston

to a crankshaft with a connecting rod.

The upper end of the connecting rod moves

with the piston.

The lower end of the connecting rod is attached

to the crankshaft and moves in a circle.

The end of the crankshaft is connected to the

flywheel.



ENGINE CLASSIFICATIONS 'perational cycles. /0 stroke or 1 stroke2

3umber of cylinders. /4,0,5,6,7,89,81

cylinders2

$ylinder arrangement. /lat, inline, )type2 )alve train type. /'($,'(), #'($2

+gnition type /&park, $ompression2

uel type /gasoline, natural gas, methanol,

diesel, propane, fuel cell, electric, hybrid2



ENGINE CONSTRUCTION Types of internal combustion engines

construction:0 &troke petrol and diesel

1 &troke petrol and diesel;otary!wankel



4 STROKE PETROL

+ntake &troke$ompression

&trokeower &troke

Exhaust&troke



INTAKE STROKE The first stroke of the cycle is the intake stroke.

As the piston moves away from top dead e!te" #TDC$, the intake

valve opens.

The downward movement of the piston increases the volume of the

cylinder above it, reducing the pressure in the cylinder. <ow

pressure /engine vacuum2 causes the atmospheric pressure to push amixture of air and fuel through the open intake valve.

As the piston reaches the bottom of its stroke, the reduction in

pressure stops, causing the intake of airfuel mixture to slow down.

+t does not stop because of the weight and movement of the airfuel

mixture.

+t continues to enter the cylinder until the intake valve closes. The

intake valve closes after the piston has reached %otto deade!te" #BDC$.

This delayed closing of the valve increases the volumetric efficiency

of the cylinder by packing as much air and fuel into it as possible.



COMPRESSION STROKE The compression stroke begins as the piston starts to

move from %#$.

The intake valve closes, trapping the airfuel

mixture in the cylinder.

The upward movement of the piston compresses the

airfuel mixture, thus heating it up.

At T#$, the piston and cylinder walls form a

combustion chamber in which the fuel will be

burned. The volume of the cylinder with the piston at %#$

compared to the volume of the cylinder with the

piston at T#$ determines the compression ratio of

the engine.



PO'ER STROKE The power stroke begins as the compressed fuel

mixture is ignited.

"ith the valves still closed, an electrical spark

across the electrodes of a spark plug ignites the

airfuel mixture.

The burning fuel rapidly expands, creating a

very high pressure against the top of the piston.

This drives the piston down toward %#$. Thedownward movement of the piston is

transmitted through the connecting rod to the

crankshaft.



E(HAUST STROKE The exhaust valve opens ust before the piston

reaches %#$ on the power stroke.

ressure within the cylinder causes the exhaust gas to

rush past the open valve and into the exhaust system.

*ovement of the piston from %#$ pushes most of theremaining exhaust gas from the cylinder.

As the piston nears T#$, the exhaust valve begins to

close as the intake valve starts to open.

The exhaust stroke completes the fourstroke cycle. The opening of the intake valve begins the cycle

again.

This cycle occurs in each cylinder and is repeated

over and over, as long as the engine is running.



+t takes two full revolutions of the crankshaft

to complete the fourstroke cycle.

'ne full revolution of the crankshaft is e=ualto 469 degrees of rotation> therefore, it

takes ?19 degrees to complete the four

stroke cycle.

#uring one piston stroke, the crankshaftrotates 879 degrees.



4 STROKE DIESEL The operation of a d)e*e+ e!,)!e is comparable to a gasoline

engine.

They also have a number of components in common, /crankshaft,

pistons, valves, camshaft, and water and oil pumps.

(owever, diesel engines have op"e**)o! ignition systems. ;ather

than relying on a spark for ignition, a diesel engine uses the heatproduced by compressing air in the combustion chamber to ignite

the fuel.

The compression ratio of diesel engines is typically three times /as

high as 15:82 that of a gasoline engine.

As intake air is compressed, its temperature rises to ?99@$ to

99@$. Bust before the air is fully compressed, a fuel inector

sprays a small amount of diesel fuel into the cylinder. The high

temperature of the compressed air instantly ignites the fuel.

The combustion causes increased heat in the cylinder and the

resulting high pressure moves the piston down on its power stroke.



4 STROKE DIESEL ENGINE



- STROKE ENGINE This engine re=uires only two strokes of the piston to

complete all four operations: intake, compression,

power, and exhaust.

This is accomplished as follows:

*ovement of the piston from %#$ to T#$ completes bothintake and compression.

"hen the piston nears T#$, the compressed air!fuel

mixture is ignited, causing an expansion of the gases.

#uring this time, the intake and exhaust ports are closed.

Expanding gases in the cylinder force the piston down,rotating the crankshaft.

"ith the piston at %#$, the intake and exhaust ports are

both open, allowing exhaust gases to leave the cylinder

and airfuel mixture to enter.



- STROKE ENGINE



- STROKE ENGINE Although the twostrokecycle engine is

simple in design and lightweight because it

lacks a valve train, it has not been widely

used in automobiles. +t tends to be +e** ./e+ e..))e!t and releases

o"e po++/ta!t* into the atmosphere than

fourstroke engines.



ROTARY0'ANKEL ENGINE The "ota" engine, or 'a!2e+ engine, is

similar to the standard piston engine in that

it is a spark ignition, internal combustion

engine. +ts design, however, is =uite different. or

one thing, the rotary engine uses a rotating

motion rather than a reciprocating motion.

+n addition, it uses ports rather than valvesfor controlling the intake of the airfuel

mixture and the exhaust of the combusted

charge.



ROTARY0'ANKEL ENGINE

http://var/www/apps/conversion/tmp/Video/Chapter%201/Rotary%20Engine.flv






CHARACTERISTICS OF ROTARYENGINE The rotating combustion chamber engine is

small and light for the amount of power it

produces, which makes it attractive for use

in automobiles.

(owever, the rotary engine at present cannot

compete with a piston gasoline engine in

terms of durability, exhaust emissions, and

economy.



BASIC ENGINE TERMINOLOGIES %ore C cylinder diameter measured in inches/in2 or

milimeters /mm2.

&troke C length of the piston travel between T#$

D %#$.

T#$ C Top dead center

%#$ C %ottom dead center

+f bore stroke, the engine is called a *3/a"ee!,)!e.

+f bore F stroke, the engine is called a oe"*3/a"ee!,)!e.

+f bore G stroke, the engine is called a

/!de"*3/a"e e!,)!e.



$ylinder #isplacement C volume of the cylinder

when the piston is at %#$.

Engine displacement C sum!total of the

displacement of each of the engine cylidners.

Typically, an engine with a larger displacement

produces more tor=ue than a smaller

displacement engine.

$ompression ratio C comparison of a cylinder-s

volume when the piston is at %#$ to the

cylinder-s volume when the piston is at T#$.The higher the compression ratio, the more power

an engine theoretically can produce.



ENGINE EFFICIENCY )olumetric efficiency describes the engine-s

ability to have its cylinders filled with air

fuel mixture.

+f the engine-s cylinders are able to be filledwith airfuel mixture during its intake stroke,

the engine has a volumetric efficiency of

899H.

Typically, engines have a volumetricefficiency of 79H to 899H.



CYLINDER HEAD & 5AL5E TRAIN urpose of cylinder head

The cylinder head fits on top of the cylinder

block to close off and seal the top of the

cylinder.

The cylinder head also contains ports through

which the airfuel mixture enters and burned

gases exit the cylinder and the bore for the

sparkplug.



TYPE OF 5AL5E TRAIN 'verhead )alve /'()2

'verhead $am /'($2

*ultivalve



O5ERHEAD 5AL5E #OH5$ The intake and exhaust valves in an '() engine

are mounted in the cylinder head and are operated

by a camshaft located in the cylinder block.

This arrangement re=uires the use of valve lifters,

pushrods, and rocker arms to transfer camshaftrotation to valve movement.





O5ERHEAD CAM #OHC$ An '($ engine also has the intake and exhaust valves

located in the cylinder head.

%ut the cam is located in the cylinder head.

+n an '($ engine, the valves are operated directly by

the camshaft or through cam followers or tappets.

Engines with one camshaft above a cylinder are often

referred to as single overhead camshaft /&'($2

engines.





MULTI5AL5E A multivalve design typically has three, four, or

five valves per cylinder to achieve improved

performance.

Any fourstroke internal combustion engine

needs at least two valves per cylinder: one for

intake of air and fuel, and another for exhaust

of combustion gases.

*ultivalve engines tend to have smaller valveshave lower reciprocating mass,

can reduce wear on each cam lobe,

more power from higher ;* without the danger of

valve bounce.



MULTI5AL5E Threevalve cylinder head

This has a single large exhaust valve and two

smaller intake valves

ourvalve cylinder headThis is the most common type of multivalve

head, with two exhaust valves and two similar

/or slightly larger2 inlet valves.

ivevalve cylinder head<ess common is the fivevalve head, with two

exhaust valves and three inlet valves. All five

valves are similar in siIe.





5AL5E TIMING "ith traditional fixed valve timing, an engine will have a period

of valve overlap at the end of the exhaust stroke, when both

the intake and exhaust valves are open.

The intake valve is opened %T#$ because to give enough time for

airfuel mixture to get into the cylinder.

The intake valve is allowed open A%#$ because to get advantagesof inertia created by velocity assists in drawing in the fresh

charge.

The exhaust valve is opened %%#$ because the gases inside the

cylinder posses a higher pressure even after the expansion

stroke. This higher pressure enables it to reduce the work that

needs to be done by the engine piston in pushing out these gases.

The exhaust valve close AT#$ because to give sufficient time for

exhaust gas exit through the exhaust valve. +f the exhaust valve

is closed like in actual timing diagram, a certain amount of

exhaust gases will get compressed and remain inside the cylinder

and will be carried to the next cycle also.



5ARIABLES 5AL5E TIMING At low speed, a little valve lift already sufficient for

air!fuel to enter the cylinder.

The fuel consumption is better and enough for

cruising and low speed.

%ut at high speed, the valve need to open and closevery fast and need more longer time for air!fuel to

enter the cylinder.

Therefore, the valve lift must be higher and the

timing is longer.

+f the engine has fixed valve lift and valve timing, the

performance will be bad.

To increase the performance of the engine and better

fuel consumption, variable valve timing is introduced.







5IDEO (ow an Engine "orks $omprehensive Tutoria

l Animation featuring Toyota Engine Technol

ogies

http://var/www/apps/conversion/tmp/Video/Chapter%201/How%20an%20Engine%20Works%20-%20Comprehensive%20Tutorial%20Animation%20featuring%20Toyota%20Engine%20Technologies.flv








E(ERCISE

8. Explain how 0stroke engine worksJ

1. $ompare 1stroke and 0stroke engines.

4. $ompare petrol and diesel engine.

0. &ketch and explain 0 process in the rotaryengine.

5. An engine has 0 cylinders. Each cylinder has

a bore of 5.85cm and its stroke is 6cm.

$alculate the engine displacements.6. #raw and explain a typical valve timing

diagram for 0stroke petrol engine.

?. "hat is Kvalve overlap-J



7UI8 1

$hapter 8

Buly 1984 /Tuesday2



THANK YOU

Documents

Engine components and classification