Chapter 1 - Engine Components and Classification (1)

8/12/2019 Chapter 1 - Engine Components and Classification (1)

1/42

Prepared by: MUHAMMAD HILMI BIN

ZAID


2/42

The topic covers basic theoretical knowledge

and understanding of engine components,

classifications and terminologies. Areas

involving engine construction, operatingprinciples and valve train


3/42

Understand engine construction

Explain various types of internal combustion

engines construction and operation:

two-stroke petrol and diesel

four-stroke petrol and diesel

rotary/Wankel

Understand basic engine terminologies

Explain basic engine terminologies such as

TDC, BDC, stroke, bore, displacement,

compression ratio etc.


4/42


5/42

Engineprovides the power to drive thevehicles wheel.

Biggest part of the engine is the cylinderblock. The cylinder block is a large casting ofmetal that is drilled with holes to allow forthe passage of lubricants and coolant throughthe block and provide spaces for movementof mechanical parts.

The block contains the cylinders, which areround passageways fitted with pistons.

The block houses or holds the majormechanical parts of the engine.
http://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Engine%20Assembly%20By%20FORD.flvhttp://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Engine%20Assembly%20By%20FORD.flv


6/42

The cylinder head fits on top of the cylinderblock to close off and seal the top of thecylinder.

The combustion chamber is an area intowhich the air-fuel mixture is compressed andburned.

The cylinder head contains all or most of the

combustion chamber. The cylinder head also contains ports through

which the air-fuel mixture enters and burnedgases exit the cylinder and the bore for the

sparkplug.


7/42

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.

Springs are used to help close the valves.


8/42

The up-and-down motion of the pistons mustbe converted to rotary motion before it candrive the wheels of a vehicle.

This conversion is achieved by linking thepiston to a crankshaft with a connecting rod.

The upper end of the connecting rod moveswith the piston.

The lower end of the connecting rod isattached to the crankshaft and moves in acircle.

The end of the crankshaft is connected to

the flywheel.


9/42

Operational cycles. (4 stroke or 2 stroke)

Number of cylinders. (3,4,5,6,8,10,12

cylinders)

Cylinder arrangement. (Flat, inline, V-type) Valve train type. (OHC,OHV, DOHC)

Ignition type (Spark, Compression)

Fuel type (gasoline, natural gas, methanol,

diesel, propane, fuel cell, electric, hybrid)


10/42

Types of internal combustion engines

construction:

4 Stroke petrol and diesel

2 Stroke petrol and diesel Rotary/wankel


11/42

Intake StrokeCompression

StrokePower Stroke

ExhaustStroke


12/42

The first stroke of the cycle is the intake stroke.

As the piston moves away from top dead center (TDC), theintake valve opens.

The downward movement of the piston increases the volume ofthe cylinder above it, reducing the pressure in the cylinder. Lowpressure (engine vacuum) causes the atmospheric pressure to

push a mixture 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 air-fuel mixture to slowdown. It does not stop because of the weight and movement ofthe air-fuel mixture.

It continues to enter the cylinder until the intake valve closes.The intake valve closes after the piston has reached bottomdead center (BDC).

This delayed closing of the valve increases the volumetricefficiency of the cylinder by packing as much air and fuel into itas possible.


13/42

The compression stroke begins as the pistonstarts to move from BDC.

The intake valve closes, trapping the air-fuelmixture in the cylinder.

The upward movement of the piston compressesthe air-fuel mixture, thus heating it up.

At TDC, the piston and cylinder walls form acombustion chamber in which the fuel will be

burned. The volume of the cylinder with the piston at

BDC compared to the volume of the cylinderwith the piston at TDC determines thecompression ratio of the engine.


14/42

The power stroke begins as the compressedfuel mixture is ignited.

With the valves still closed, an electricalspark across the electrodes of a spark plug

ignites the air-fuel mixture. The burning fuel rapidly expands, creating a

very high pressure against the top of thepiston.

This drives the piston down toward BDC. Thedownward movement of the piston istransmitted through the connecting rod tothe crankshaft.


15/42

The exhaust valve opens just before the pistonreaches BDC on the power stroke.

Pressure within the cylinder causes the exhaust gas torush past the open valve and into the exhaust system.

Movement of the piston from BDC pushes most of theremaining exhaust gas from the cylinder.

As the piston nears TDC, the exhaust valve begins toclose as the intake valve starts to open.

The exhaust stroke completes the four-stroke cycle.

The opening of the intake valve begins the cycleagain.

This cycle occurs in each cylinder and is repeatedover and over, as long as the engine is running.


16/42

It takes two full revolutions of the crankshaft

to complete the four-stroke cycle.

One full revolution of the crankshaft is equalto 360 degrees of rotation; therefore, it

takes 720 degrees to complete the four-

stroke cycle.

During one piston stroke, the crankshaftrotates 180 degrees.
http://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/How%204-Stroke%20Engines%20Work.flv


17/42

The operation of a diesel engine is comparable to a gasolineengine.

They also have a number of components in common, (crankshaft,pistons, valves, camshaft, and water and oil pumps.

However, diesel engines have compressionignition systems.Rather than relying on a spark for ignition, a diesel engine uses

the heat produced by compressing air in the combustion chamberto ignite the fuel.

The compression ratio of diesel engines is typically three times(as high as 25:1) that of a gasoline engine.

As intake air is compressed, its temperature rises to 700C to900C. Just before the air is fully compressed, a fuel injectorsprays a small amount of diesel fuel into the cylinder. The hightemperature of the compressed air instantly ignites the fuel.

The combustion causes increased heat in the cylinder and theresulting high pressure moves the piston down on its powerstroke.


18/42


19/42

This engine requires only two strokes of thepiston to complete all four operations: intake,compression, power, and exhaust.

This is accomplished as follows: Movement of the piston from BDC to TDC completes

both intake and compression. When the piston nears TDC, the compressed air/fuel

mixture is ignited, causing an expansion of the gases.During this time, the intake and exhaust ports areclosed.

Expanding gases in the cylinder force the pistondown, rotating the crankshaft.

With the piston at BDC, the intake and exhaust portsare both open, allowing exhaust gases to leave thecylinder and air-fuel mixture to enter.


20/42
http://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/How%202-Stroke%20Engines%20Work.flv


21/42

Although the two-stroke-cycle engine is

simple in design and lightweight because it

lacks a valve train, it has not been widely

used in automobiles.

It tends to be less fuel efficient and releasesmore pollutantsinto the atmosphere thanfour-stroke engines.


22/42

The rotary engine, or Wankel engine, issimilar to the standard piston engine in that

it is a spark ignition, internal combustion

engine.

Its design, however, is quite different. For

one thing, the rotary engine uses a rotating

motion rather than a reciprocating motion.

In addition, it uses ports rather than valvesfor controlling the intake of the air-fuel

mixture and the exhaust of the combusted

charge.


23/42
http://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Rotary%20Engine.flvhttp://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Rotary%20Engine.flvhttp://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Rotary%20Engine.flvhttp://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Rotary%20Engine.flv


24/42


25/42

Bore cylinder diameter measured ininches(in) or milimeters (mm).

Stroke length of the piston travel betweenTDC & BDC.

TDC Top dead center

BDC Bottom dead center

If bore = stroke, the engine is called asquare engine.

If bore > stroke, the engine is called aoversquare engine.

If bore < stroke, the engine is called aundersquare engine.


26/42

Cylinder Displacement volume of the cylinder

when the piston is at BDC.

Engine displacement sum/total of the

displacement of each of the engine cylidners.

Typically, an engine with a larger displacement

produces more torque than a smaller

displacement engine.

Compression ratio comparison of a cylindersvolume when the piston is at BDC to the

cylinders volume when the piston is at TDC.

The higher the compression ratio, the more power an

engine theoretically can produce.


27/42

Volumetric efficiency describes the engines

ability to have its cylinders filled with air-

fuel mixture.

If the engines cylinders are able to be filledwith air-fuel mixture during its intake stroke,

the engine has a volumetric efficiency of

100%.

Typically, engines have a volumetricefficiency of 80% to 100%.


28/42

Purpose 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 air-fuel mixture enters and burned

gases exit the cylinder and the bore for the

sparkplug.


29/42

Overhead Valve (OHV)

Overhead Cam (OHC)

Multivalve


30/42

The intake and exhaust valves in an OHV engineare mounted in the cylinder head and areoperated by a camshaft located in the cylinderblock.

This arrangement requires the use of valve

lifters, pushrods, and rocker arms to transfercamshaft rotation to valve movement.


31/42


32/42

A multivalve design typically has three, four, or

five valves per cylinder to achieve improved

performance.

Any four-stroke internal combustion engine

needs at least two valves per cylinder: one for

intakeof air and fuel, and another for exhaust

of combustion gases.

Multi-valve engines tend to have smaller valves

have lower reciprocating mass,

can reduce wear on each cam lobe,

more power from higher RPM without the danger of

valve bounce.


33/42

Three-valve cylinder head

This has a single large exhaust valve and two

smaller intake valves

Four-valve cylinder head This is the most common type of multi-valve

head, with two exhaust valves and two similar

(or slightly larger) inlet valves.

Five-valve cylinder head

Less common is the five-valve head, with two

exhaust valves and three inlet valves. All five

valves are similar in size.


34/42

Valve timing is the precise timing of the opening and closing ofthe valves.

One way to look at this diagram is to think of these events interms of the position of the crankshaft and 360 degrees rotation.


35/42

With traditional fixed valve timing, an engine will have a periodof valve overlap at the end of the exhaust stroke, when both

the intake and exhaust valves are open.

The intake valve is opened BTDC because to give enough time for

air-fuel mixture to get into the cylinder.

The intake valve is allowed open ABDC because to get advantagesof inertia created by velocity assists in drawing in the fresh

charge.

The exhaust valve is opened BBDC 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 ATDC because to give sufficient time for

exhaust gas exit through the exhaust valve. If 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.


36/42

At low speed, a little valve lift already sufficientfor air/fuel to enter the cylinder.

The fuel consumption is better and enough forcruising and low speed.

But at high speed, the valve need to open andclose very fast and need more longer time forair/fuel to enter the cylinder.

Therefore, the valve lift must be higher and thetiming is longer.

If the engine has fixed valve lift and valvetiming, the performance will be bad.

To increase the performance of the engine andbetter fuel consumption, variable valve timing isintroduced.


37/42

How it works?

As the camshaft spins, the lobes open and close

the intake and exhaust valves in time with the

motion of the piston.

VVT is the process of altering the timing of a

valve lift event, and is often used to improve

performance, fuel economy or emissions.

Some cars use a device that can advance the

valve timing. This does not keep the valves openlonger; instead, it opens them later and closes

them later.

VIDEO
http://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Standard%20vs%20Performance%20Cam.swfhttp://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Standard%20vs%20Performance%20Cam.swf


38/42

Type of variables valve timing

VTEC(Honda)

MIVEC (Mitsubishi)

VVTI (Toyota) CPS(Proton)

DVVT (Perodua)
http://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/How%20VTEC%20works.flvhttp://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Camshaft%20Profile%20Switching%20(CPS).flvhttp://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/Camshaft%20Profile%20Switching%20(CPS).flvhttp://localhost/var/www/apps/conversion/tmp/Video/Chapter%201/How%20VTEC%20works.flv


39/42

How an Engine Works - Comprehensive

Tutorial Animation featuring Toyota Engine

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


40/42

1. Explain how 4-stroke engine works?

2. Compare 2-stroke and 4-stroke engines.

3. Compare petrol and diesel engine.

4.

Sketch and explain 4 process in the rotaryengine.

5. An engine has 4 cylinders. Each cylinder hasa bore of 5.15cm and its stroke is 6cm.Calculate the engine displacements.

6. Draw and explain a typical valve timingdiagram for 4-stroke petrol engine.

7. What is valve overlap?


41/42

Chapter 1

9 July 2013 (Tuesday)


42/42

Chapter 1 - Engine Components and Classification (1)

Documents

Transcript of Chapter 1 - Engine Components and Classification (1)