Internal combustion engines

INTERNALCOMBUSTIONENGINES

Theautomobileenginewillcome,andthenIwillconsidermylife'sworkcomplete.- RudolfDiesel

Dr.Rohit SinghLather

ICENGINESARECYCLICDEVICESTOSATISFYHUMANNEEDS

Comfort!Power to do more work efficiently!

2Introduction toICEngines- Dr.RohitSinghLather

COMMONAPPLICATIONSOFICENGINES


PASTTOPRESENT

4

SimpleGasEngine1800’s

PresentDayComplexElectronicallyControlledEngines

(CocktailofTechnologies)

Over100yearsofContinuousDevelopment

Introduction toICEngines- Dr.RohitSinghLather

HEATENGINE

• An engine which derives heat energy from the combustion of the fuel and converts part of this energy in to

mechanical work is known as heat engine

5

HEATENGINES

InternalCombustion ExternalCombustion

SIEngine CIEngine

OttoCycle DieselCycle

AdvantagesofI.C.EoverE.C.E

• Mechanicallysimpleandlowerweight/power ratio

• Don’tneedauxiliaryequipment, suchasboiler&condenser

• Canbestartedandstopped inashort time

• HigherThermalefficiency

• Lowinitialcost


INTRODUCTION

• The purpose of internal combustion engines is the production of mechanical power from the chemical

energy contained in the fuel

• Fuelled by oil/gas and air mixture

6

• The internal combustion engine is an machine which converts LOW grade energy (Heat) to HIGH

grade energy (Work)

• Internal combustion engines convert reciprocatory motion to rotary motion


WHATIS/ISNOTANI.C.ENGINE

IS

• Gasoline-fueled reciprocating pistonengine• Diesel-fueled reciprocating pistonengine• Gas turbine• Rocket

ISNOT

• Steampowerplant• Solarpowerplant• Nuclearpowerplant


1700s- STEAMENGINES(externalcombustionengines)

1859- OILDISCOVERED

1860 - LENOIRENGINE- Frenchgentleman, J.J.E.Lenoir,in1860,developed thefirstICengine forcommercialuse- Firstmarketableengine- Fueledbycoalgasandairmixture- Lenoirengine (h =5%)

1861 -OTTObuilthisfirstgasengine1867 - OTTOINPARTNERSHIPWITHEUGENLANGEN,

- ImprovedthedesignandwonagoldmedalattheParisExposition- Produced famous“Silent”engine,nowcalledthe“OttoCycle”

HISTORY OFICENGINES

• Power:2hp @160rpm;Weight:1250pounds• Comp.ratio=4(knocklimited),14%efficiency(theory38%)• TodayCR=9(stillknocklimited),30%efficiency(theory55%)

1867 - OTTO- LANGENENGINE(η =11%,90RPMmax.)

1876 - OTTOFOURSTROKE“SPARKIGNITION”ENGINE- Premixed-charge,4-strokeengine– Otto- 1st PracticalICE

1880s - Two stroke engine1892 - Diesel four stroke “compression ignition”engine1897 - Non-premixed-charge engine - Diesel - Higher efficiency due to

Higher compression ratio (no knock problem)No throttling loss - use fuel/air ratio to control power

1901 - “2nd Industrial Revolution”will be fueled by oil

1921 - Tetraethyl lead anti-knock additivediscovered at GeneralMotors

- Enabled higher compression ratio (thusmore power, better efficiency) in Otto-type engines

1952 - A.J.Haagen-Smit,CaltechNO+UHC+O2 +sunlight= NO2 +O3

(fromexhaust)(brown)(irritating)(UHC=unburnedhydrocarbons)

1957 - Wenkel “rotary”engine

1960s - Emissionsregulations• Initialstop-gapmeasures- leanmixture,EGR,retardspark• Poorperformance&fueleconomy


1973&1979- Theenergycrises

1975- Catalyticconverters, unleadedfuel

- More“aromatics”(e.g.,benzene)ingasoline- highoctanebutcarcinogenic,soot-producing

1980s -Microcomputercontrolofengines

• Tailoroperationforbestemissions,efficiency

1990s - Reformulatedgasoline• Reducedneedforaromatics,cleaner(?)• Highercost,lowerkilometerperliter• ThenwefoundthatMethyltertiarybutylether(MTBE)pollutesgroundwater!• Alternative“oxygenated”fueladditive- ethanol- veryattractive

2000’s - hybrid vehicles• Use small gasoline engine operating at maximum power (most efficient way to operate) or turned off if notneeded

• Use generator/batteries/motors tomake/store/use surplus power fromgasoline engine• More efficient, butmuch more equipment on board - not clear if fuel savings justify extra cost• Plug-in hybrid: half-waybetween conventional hybridand electric vehicle


LARGESTINTERNALCOMBUSTIONENGINE• Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel, built in Finland, used in container ships• Also one of the most efficient IC engines: 51%


14CYLINDERDIESELENGINE(80MW)

13

Max.Power81,221kW(108,920hp)@102rpmMax.Torque7,603,850Nm@102RPM

Weight:2300tonsLength:89feetHeight:44feet



MOSTPOWERFULINTERNALCOMBUSTIONENGINE• Space Shuttle Solid Rocket Boosters are themost powerful

(≈42millionhorsepower;notshaftpowerbutkineticenergyofexhauststream)


MOSTPOWERFULINTERNALCOMBUSTIONENGINE• Most powerful shaft-power engine:Siemens SGT5-8000H

16

Stationarygasturbine (340MW=456,000HP)usedforelectricalpowergeneration


WORLDSSMALLESTICENGINE

• Produced by engineers at theUniversity of Birmingham

• World’s smallest petrol engine that is tiny enough to power a watch

• The mini-combustion engine can run for two years on a single dose of a light

fuel

• Produces 700 times more energy than a conventional battery despite having

a size less than a centimeter long

• If the technology matures, it could be used to power laptops and mobile

phones formonths


PARTSOFANICENGINECOMMONTOSIANDCI

18

Crankcase

Piston

WaterJacket

CoolingWater

CylinderHead

ExhaustValve

ValveSpring

Crankshaft

Connecting rod

Cylinderblock

Combustion chamber

Cam

IntakeValve

IntakeManifold ExhaustManifold



20

SparkPlug Injector

PortInjection DirectInjection

COMMONLY USED FUEL INDUCTION TECHNIQUES FOR GASOLINE AND DIESEL ENGINES


GEOMETRYOFANICENGINE

Displacement Volume Volume displaced by the piston as it

travels through one stroke

21

LDdV 4

2π=

zLDdV .4

2π=

Top Dead Center

Bottom Dead CenterEngine displacement volume Displacement volume multiplied by no.

of cylinders (z)

Bore (B)Diameter of the cylinder

Stroke (L) Movement distance of the piston from one extreme position to the other: TDC to BDC or BDC to TDC

Clearance volumeMinimum Volume in the combustion

chamber with piston at TDC


22

Compression Ratio (rc): The ratio between the volume

of the cylinder, when the piston is at the bottom of its

stroke (BDC), and the volume when the piston is at the

top of its stroke (TDC). This volume is called

“clearance volume” (Vc):

cVdV

cVcVdVcr +=

+= 1

Typical values of the compression ratio are:

- SI Engines: 8 – 12 - CI Engines: 16 – 22


CLASSIFICATIONOFINTERNALCOMBUSTIONENGINES


ICEngineClassificationTree

24

ICENGINES

FourStroke

SIEngine CIEngine

Gasoline Gas

TwoStroke

MultiFuel DividedChamber

Carbureted Injection PreChamber SwirlChamber

Battery Magneto

WaterCooled AirCooled

Steady NonSteady

Premixed NonPremixed

GasTurbine RocketRamjet

Turboshaft TurbojetTurbojet

SolidFuel LiquidFuel


MAINCLASSIFICATIONCRITERION

FuelType(Gasoline/Diesel)

Fueldelivery(Port/Direct)

IgnitionType(Spark/Compression)

CamshaftType(DOHC/SOHC)

ConstructionType(Inline/V)

CoolingType(Air/Water)

Application(Car/Bus/Genset)

OperatingCycle(Otto/Dual)

ChargePressure(Natural,Turbo)

GasExchange(2/4Stroke)


CLASSIFICATIONONBASISOFBASICDESIGN• Reciprocating

(a) Single Cylinder


MULTICYLINDERS

In-lineAllcylindersarearrangedlinearly

VCylindersareintwobanksinclinedatanangletoeachotherandwith

onecrank-shaft

Radial/Rotarytheradialengineisanenginewithmorethantwocylindersineachrowequally

spacedaround thecrankshaft

OpposedCylinderBankslocatedinthesameplaneonopposite sidesofthecrank- shaft

OpposedPistonWhenasinglecylinderhousestwopistons,eachofwhichdrivesaseparatecrankshaft

• Cylinders may be vertical or horizontal • Vertical engines needs smaller area• When area is available horizontal engines may

be used


ROTARYENGINES:WANKELENGINE

SingleRotor Multi- Rotor


RECIPROCATINGROTARYENGINES• A rotary engine is characterized by a fixed crankshaft and cylinders that rotate• The propeller is attached to the spinningcrankcase• A fuel meteringcarburetor is attached to the hollow fixed crankshaft- Air, fuel and castor oil (for lubrication), are drawn into the crankcase then pass through the intake pipes to the cylinders- The exhaust is timed to exit at the bottom of the engine to minimize interference with the pilot

• This arrangement was common in World War I, when modern high-strength, heat resistant, steels were notcommonly available

• Coolingwas accomplished byhaving the cylinders spin• Always odd number of cylinders• Completely different from theWankel Rotary Engines

29

Fixed Crankshaft

(viewed from the side)

AircraftNose

RotatingCylinders


MECHANICALARRANGEMENT– RADIAL/ROTARYENGINES

Cylinders Crankcase

Valve Gear

Valve Pushrod

Spark Plug

Propeller Mount Bolts


GASTURBINEENGINES

• Thegasturbinegroupneedsacompressors,itsweightissmallerthanreciprocatingI.C.E.ofthesamepower,its

efficiencyislower,thefuelrelativelycheap,anditissuitableforaircraft

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CombustionChamber

Compressor

FuelIn

Turbine

AtmosphericAir ExhaustGases

ShaftOutput=WnetWCompresssor


• Gas turbine engines are, theoretically, extremely simple. Theyhave three parts:- Compressor - Compresses the incoming air to high pressure- Combustion area - Burns the fuel and produces high-pressure, high-velocity gas- Turbine - Extracts the energy from the high-pressure, high-velocity gas flowing from the combustion chamber

Compressor Combustion Turbine


WANKELROTARYPISTONENGINE

33

• Rotary engine is a substitute for the reciprocating I.C.E. Wankel engine has a three lobe rotor which is

driven eccentrically in a casing in such a way that there are three separate volumes trapped between the

rotor and the casing

• These volumes perform induction, compression, combustion, expansion and exhaust process in

sequence

Rotary Engine


34

• Uses non-cylindrical combustion chamber.• Provides one complete cycle per engine revolution without “short circuit” flow of 2-strokes (but still

need some oil injected at the rotor apexes)• Simpler, fewer moving parts, higher RPM possible• Very fuel-flexible - can incorporate catalyst in combustion chamber since fresh gas is moved into

chamber rather than being continually exposed to it (as in piston engine) - same design can usegasoline, Diesel, methanol, etc.

• Very difficult to seal both vertices and flat sides of rotor• Seal longevity a problem• Large surface area to volume ratio means more heat losses

Advantages:Drawbacks:• HigherpoweroutputIncreasedwearofrubbingparts• NoreciprocatingmassHigherfuelconsumption• SimplerandlighterconstructionRequirementforbettermaterials


Inlet Port

Exhaust Port

Casing

Spark Plug

Output Shaft

Rotating Triangular

‘Piston’

Fixed (non-rotating) Pinion

This motion drives the rotating crankshaft

Which in turn drives the output shaft

The piston rotates around the fixed pinion

Shape of the piston and the casing also make the piston

move up and down by a small amount as well

Rotating ‘Crankshaft’

Points of contact marked in yellow


Chamber A

Chamber C

Inlet Port

Exhaust Port

Chamber B

WankelEngine– EngineCycle


ENGINECONFIGURATION

• After the type and size of engine have been determined, the number and disposition of the cylinders must be

decided.

• The main constraints influencing the number and dispositionof the cylinders are as follows:

1. The number of cylinders needed to produce a steadyoutput

2. Theminimum swept volume for efficient combustion

3. The number and disposition of cylinders for satisfactory balancing

4. The number of cylinders needed for an acceptable variation in the torque output


WORKINGCYCLE(STROKES)1.FourStrokeCycle:(a)NaturallyAspirated:Admissionofchargeatnearatmosphericpressure

(b)Supercharged/Turbocharged:Admissionofchargeatapressureaboveatmospheric

2.TwoStrokeCycle:(a)CrankcaseScavenged(b)UniflowScavenged

(i)Inletvalve/ExhaustPort(ii)InletPort/ExhaustValve(iii)InletandExhaustValveMaybeNaturallyAspirated/Turbocharged


FUELUSED

39

• Volatileliquidfuels:Petrol,Alcohol,benzene- Fuel/Airmixtureisusuallyignitedbyaspark- Sparkignition

• Viscousliquidfuels:Fueloil,Heavyandlightdieseloil,Gas-oil,Bio-fuels

- Usuallycombustionoffueltakesplaceduetoitscontactwithhightemperaturecompressedair(self- ignition)

- Compressionignition

LIQUIDFUELS

• LiquidPetroleumGas(LPG)

• Naturalgas(NG)

• Towngas

• BlastFurnacegas

- Ignitionusuallybyaspark

GASEOUSFUELS

• DUALFUELENGINESareoperatedwithtwotypesoffuels,eitherseparatelyormixedtogether

• Multi-fuelenginescouldbeoperatedbyamixtureofmorethantwofuels,gaseous;suchas:Hydrogen,methane,L.P.G.etc.,

combinedwithoneormoreofliquid fuels, suchasalcohol,ethers,esters,gasoline,dieseletc...


GENERALFOURSTROKECYCLE

40

PowerorExpansionStroke(TDCtoBDC)

ExhaustStroke(BDCtoTDC)

CompressionStroke(BDCtoTDC)

IntakeorInductionStroke(TDCtoBDC)


1st Stroke - INTAKE stroke - 180° CAAir– FuelMixture/OnlyAirenterintothecylinder

IntakeValveOpen

2nd Stroke - Compression stroke - 360° CAAir- Fuel/AirgetscompressedInlet&ExhaustValveClosed

3rd Stroke = Power stroke = 540° CASpark/Fuelissupplied;Combustionstarts;Gasesexpandmovingthepistondownwards

IntakeandExhaustValvesareclosed

4th Stroke - Exhaust stroke - 720° CAExhaustgasesexitthroughexhaustvalve

ExhaustValveOpen

Top Dead Centre (TDC)

Bottom Dead Centre (BDC)


FOURSTROKESICYCLE

42

Intake or Induction Stroke(TDC to BDC)

Compression Stroke (BDC to TDC)

Piston moves into the cylindercompressing the fuel-air mixture / only air to high

density, pressure and temperature

At the end of the compression an electric spark ignites the mixture starting the combustion process and converting air and fuel into extremely hot burned gas

Fuel-air mixture is drawn into the

cylinder


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Power or Expansion Stroke (TDC to BDC)

Exhaust Stroke (BDC to TDC)

During this stroke the mixture burns rapidly, expanding gases drive

piston downwards

During this stroke the exhaust gases are expelled

from the cylinder ready for the next induction

stroke. In this stroke piston will move from BDC

to TDC


FEATURESOF4STROKESIENGINES

• Most common type of IC engine

• Simple, easy to manufacture, inexpensive materials

• Good power/weight ratio

• Excellent flexibility - works reasonably well over a wide range of engine speeds and loads

• Rapid response to changing speed/load demand

• “Acceptable” emissions

• Weaknesses

• Fuel economy (compared to Diesel, due lower compression ratio & throttling losses at part-load)

• Power/weight (compared to gas turbine)


FOURSTROKECI

45

PowerorExpansionStroke(TDCtoBDC)

ExhaustStroke(BDCtoTDC)

CompressionStroke(BDCtoTDC)

IntakeorInductionStroke(TDCtoBDC)


FOURSTROKECI

46

Intake or Induction Stroke(TDC to BDC)

Compression Stroke (BDC to TDC)

Piston moves into the cylinder, compressing the only air to high density, pressure and temperature

At the end of the compression fuel is injected at high pressure, starting the combustion process and

converting air and fuel into extremely hot burned gas. Only air is drawn into the cylinder


FOURSTROKECI

47

Power or Expansion Stroke (TDC to BDC)

During this stroke the mixture burns rapidly, expanding gases drive

piston downwards

Exhaust Stroke (BDC to TDC)

During this stroke the exhaust gases are expelled

from the cylinder ready for the next induction

stroke. In this stroke piston will move from BDC

to TDC


TWO-STROKECYCLE• The two-stroke cycle of an internal combustion engine differs from the more common four-stroke cycle

by completing the same four operations (intake, compression, power, exhaust) in only two strokes (linearmovements of the piston) rather than four

• There is a power stroke per piston for every engine revolution, instead of every second revolution• Two-stroke engines can be arranged to start and run in either direction

PoppetIntakeValve

Crankcase

ExhaustPort

TransferPort

Compression causes combustionPiston pushed down forces

fuel/air mixture into cylinder

48

Pistonrisingpullsfuel/airmixtureintocrankcase


49

PowerCompression

Piston rises, driven by flywheel

momentum

compresses the fuel mixture

(At the same time, another intake stroke is happening

beneath the piston)

At the top of the stroke the spark plug ignites

the fuel mixture

The burning fuel expands, driving the piston downward,

to complete the cycle


SHORTCIRCUITINGOFFUELIN2STROKEENGINES

50

• Air and fuel mixture move out from the exhaust port when it is open• This happens due to overlapping of the inlet and exhaust ports


• Transfer/Exhaust: Toward the end of the stroke, the piston exposes the transfer port, allowing thecompressed fuel/air mixture in the crankcase to escape around the piston into the main cylinder- This expels the exhaust gasses out the exhaust port, usually located on the opposite side of the

cylinder. Unfortunately, some of the fresh fuel mixture is usually expelled as well

51

the piston exposes the transfer port Piston moving downwards

towards the BDC,near the end of the stroke

crankcase

cylinder exhaust gasses out the exhaust port


MECHANICALLAYOUTOFATYPICAL2STROKEMOTORCYCLEENGINE

52

CoolingFins


ATYPICALDIESEL2STROKEENGINE

• Used in large engines, e.g. locomotives

– Air comes in directly through intake ports, not via crankcase

– Must be turbocharged or supercharged to provide pressure to

force air into cylinder

– Rather than ports - not necessary to have intake & exhaust paths

open at same time

– Only air, not fuel/air mixture enters through intake ports, “short

circuit” of intake gas out to exhaust is not a problem

– 2-stroke diesels have far fewer environmental problems than 2-

stroke gasoline engines

53

Nooilmixedwithair- crankcaselubricationlike4-stroke

Exhaustvalves


4- STROKEVS2- STROKEADVANTAGESAdvantages4- StrokeEngine

üHigh Volumetric Efficiency over a wide engine speedrange

üLow Sensitivity to Pressure Losses in the exhaustsystem

üEffective Control of the Charging Efficiency troughappropriate valve timingand intake systemdesign

Advantages 2– StrokeEngineüVerySimpleandCheapenginedesignüLowWeightüLowManufacturingCostüBetterTorsionalForcesPatternü2-stroke engines may not have valves, whichsimplifies their construction and lowers theirweight.

üFire once every revolution, while 4-stroke enginesfire once every other revolution. This gives two-stroke engines a significant power boost.


4- STROKEVS2- STROKEDISADVANTAGES

Disadvantages4-StrokeEngine

üHighComplexityoftheValveControl

üReducedPowerDensitybecausetheworkisgeneratedonlyeverysecondshaftrotation

Disadvantages2-StrokeEngine

üHigherfuelconsumption

üHigherHCemissions(Poorscavenging)

üLowerMeanEffectivePressure(PoorVolumetricEfficiency)

üHigherThermalLoad

(Nogasexchangestroke)

üPooridle(Highresidualgaspercentageintothecylinder)

• More pollution because of 30% of the fuel is wasted.

• Less efficiency comparedwith four stroke engine.

• Requires special two stroke oil ("premix")


VALVE/PORTDESIGN1. PoppetValve2. RotaryValve3. ReedValve4. PistonControlledPorting

• ValveLocation1. TheT-head2. TheL-head3. TheF-head4. TheI-head:(i)OverHeadValve(OHV)

(ii)OverHeadCam(OHC)


DIFFERENTTYPESOFVALVELOCATION

57

LHeadSIEnginesOnly

IHeadSI&CIEnginesCurrentPractice

FHeadSIPromising

THeadObsolete


OVERHEADVALVEARRANGEMENT

58

SingleOverHeadCamshaft(SOHC)

DoubleOverHeadCamshaft(DOHC)


VALVEOPERATION


OVERHEADCAMVS.OVERHEADVALVE


VALVETIMINGDIAGRAM

61

GeneralValveTimingDiagram


VALVETIMINGDIAGRAMOFFOURSTROKEENGINES


UNDERSTANDINGVALVEOVERLAP

63

PowerStroke ExhaustStroke IntakeStroke CompressionStroke00 1800 3600 5400 7200

BothValveOpen

ExhaustValveStartstoOpen

IntakeValveCloses

Thedurationofcrankangleinwhichbothinletandexhaustvalveremainsopeniscalledasvalveoverlap

Itoccursattheendofexhauststrokewhenthepiston isabouttoreachTDCandcontinues forafewdegreeofcrankangleafter TDC

ExhaustGasesOut



• Exhaust Blowdown : Late in the power stroke, the exhaust valve is opened and exhaust blowdown occurs

• Pressure and temperature in the cylinder are still high relative to the surroundings at this point, and a pressure

differential is created through the exhaust systemwhich is open to atmospheric pressure

- This pressure differential causes much of the hot exhaust gas to be pushed out of the cylinder and through the

exhaust systemwhen thepiston is near BDC

- This exhaust gas carries away a high amount of enthalpy,which lowers the cycle thermal efficiency

- Opening the exhaust valve before BDC reduces the work obtained but is required because of the finite time

needed for exhaust blowdown

EXHAUSTBLOWDOWN


FIRINGORDER

• Every engine cylindermust fire once in every cycle

• The order in which various cylinders of a multi cylinder engine fire is called the firing order

- For a four-stroke four- cylinder engine the ignition systemmust fire for every 180 degrees of crank rotation

- For a six- cylinder engine the time available is only 120 degrees of crank rotation.

• The number of possibilities of firingorder depends upon thenumber of cylinders and throwsof the crankshaft

• It is desirable to have the power impulses equally spaced and from the point of view of balancing this has led to

certain conventional arrangements of crankshaft throws


• Factors to be considered before deciding the optimum firing order of an engine- Engine vibrations- Engine coolingand- Development of back pressure

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4

3

2

1

4

3

2

1

4

3

2

1

WithoutFiringOrder WithFiringOrder1 WithFiringOrder2


GENERALFIRINGORDER• 4-Cylinder engines: 1-3-4-2 (commonly used); 1-2-4-3• 6-Cylinder engine : 1-5-3-6-2-4 (commonly used);1-5-4-6-2-3;1-2-4-6-5-3; 1-2-3-6-5-4.• 3 Cylinder engine: 1-3-2• 8 Cylinder in-line engine: 1-6-2-5-8-3-7-4• 8 Cylinder V engine: 1-5-4-8-6-3-7-2; 1-8-4-3-6-5-7-2; 1-6-2-5-8-3-7-4; 1-8-7-3-6-5-4-2; 1-5-4-2-6-3-7-8.

Note: Cylinder No. 1 is taken from front of the in-line engines whereas in V shape front cylinder on right side-bank is consideredcylinder No.1 for fixing H.T. leads according to engine firing order.


69

ba

1

2 3

4

1 4

2 3

EFFECTOFFIRINGORDERONENGINEVIBRATIONSFire cylinder 1- A pressure p, generated in the cylinder number 1 will give rise to the forces shown in the figure

{pA x[b/(a+b)]} {pA x[a/(a+b)]}

BearingsA BearingsB

LoadonA>B

Fire cylinder 2 – Imbalance in load on the two bearingswould lead to imbalance and sever engine vibration

Fire cylinder 3 - after cylinder number 1, the loadmay be more or less evenly distributed


• When the first cylinder is fired its temperature increases.

• If the next cylinder that fires is number 2, the portion of the engine between the cylinder number 1 and 2

gets overheated.

• If then the third cylinder is fired, overheating is shifted to the portion between the cylinders 2 and 4.

• The task of the cooling system becomes very difficult because it is then, required to cool more at one

place than at other places and this imposes great strain on the cooling system. If the third cylinder is fired

after the first the overheating problem can be controlled to a greater extent.

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EFFECTOFFIRINGORDERONENGINECOOLING


• After firing the first cylinder, exhaust gases flow out to the exhaust pipe.

• If the next cylinder fired is the cylinder number 2, we find that before the gases exhausted by the first

cylinder go out of the exhaust pipe the gases exhausted from the second cylinder try to overtake them.

• This would require that the exhaust pipe be made bigger. Otherwise the back pressure in it would

increase and the possibility of back flow would arise.

• If instead of firing cylinder number 2, cylinder number 3 is fired. then by the time the gases exhausted by

the cylinder 3 come into the exhaust pipe, the gases from cylinder 1 would have sufficient time to travel

the distance between cylinder 1 and cylinder 3 and thus, the development of a high back pressure is

avoided.

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EFFECTOFFIRINGORDERONFLOWOFEXHAUSTGASES


• With the analogy of human metabolism one can explain combustion of engine:

- Human metabolism = Oxidization of food converts chemical energy into Mechanical energy

- Food = Fuel

- Oxygen = Air

- Optimum air fuel ratio leads = Balanced diet leadsto optimum engine performance to healthy human life

- Cooling of engine via water, air or = Human body maintains its temperature byany coolant to maintain its temperature perspiration, sweating

HUMAN ANALOGY


ASSIGNMENT


Date post:	20-Feb-2017
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Internal combustion engines

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