internal combustion engine course

8/10/2019 Internal Combustion Engine Course

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InternalCombustionEngineOverview


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Points of discussionTypes of enginesClassification of enginesGlossary of Engine TermsLubrication SystemCarburetor and EFI systemCombustion chambers: Designs and typesCNG, LNG and LPGEffects on the environment


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Types of enginesThere are basically two types of engines1. Internal Combustion Engines2. External Combustion Engines


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Internal combustion enginesIn internal combustion engines thecombustion of the fuel occurs inside thecombustion chamber. The fuel air mixture isentered the combustion chamber and thenit is provided by the spark for the ignition ofthe fuel.


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CLASSIFICATION OF ICENGINES

ApplicationBasic Engine DesignOperating CycleWorking Cycle

Valve/Port Design and LocationFuelMixture PreparationIgnitionStratification of ChargeCombustion Chamber DesignMethod of Load ControlCooling


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ApplicationsAutomotive

CarTruck/BusOff-highway

LocomotiveLight AircraftMarinePower GenerationAgricultural

TractorsPump sets

Home UseLawnmowersSnow blowersTools


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Basic Engine Design

1. ReciprocatingSingle Cylinder

Multi-cylinderRadialOpposedCylinderOpposed

PistonRotary


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Types of Reciprocating

Engines


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V Engine


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Operating cycles

Otto (For the Conventional SI Engine)Atkinson (For Complete Expansion SIEngine)Miller (For Early or Late Inlet Valve Closing

type SI Engine)Diesel (For the Ideal Diesel Engine)Dual (For the Actual Diesel Engine)


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FuelConventional

Crude oil derivedPetrolDiesel

Other sourcesCoalWood (includes bio-mass)Tar Sands

AlternatePetroleum derived

CNGLPG

Bio-mass Derived

Alcohols (methyl and ethyl)Vegetable oilsProducer gas and biogasHydrogen

BlendingDual fueling


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Mixture PreparationCarburetionFuel Injection

DieselGasoline

ManifoldPort

Cylinder


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IgnitionSpark Ignition

ConventionalBatteryMagneto

Compression Ignition


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Combustion ChamberDesign

1. Open ChamberDisc type

WedgeHemisphericalBowl-in-pistonOther design

Divided Chamber (For CI) Swirl chamberPre-chamber


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Methods of Load controlThrottling: (To keep mixture strength constant)Also called Charge Control

Used in the Carbureted S.I. EngineFuel Control (To vary the mixture strengthaccording to load)

Used in the C.I. Engine

CombinationUsed in the Fuel-injected S.I. Engine.


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Types of coolingDirect Air-cooling

Indirect Air-cooling (Liquid Cooling)

Low Heat Rejection (Semi-adiabatic) engine.


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Basic Engine TermsCamshaftShaft that is moved by the crankshaft with two or more offset cams(lobes) that operate the valves

CombustionProcess in which a substance reacts with oxygen to give heat andlight (burning)CompressionPhase in the working of an internal combustion engine where acombination of fuel and air is compressed in a cylinder beforebeing ignitedCrank/crankshaftRod that spins and drives a piston movement in the cylinderCrank angleAngle that can be measured between the crankshaft and topdead centre


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Basic Engine TermsCylinderCentral working part of a reciprocating (or piston) engine, thespace through which a piston travelsExhaustGases ejected from an engine as waste productsFlame speedFuel's ability to undergo controlled combustion without detonation.Flame speed can be used as a measure of efficiencyFuel injectionSystem for mixing fuel with air. Fuel injection atomizes the fuel byforcibly pumping it through a small nozzle under high pressureSpark plugElectrical device that fits into the cylinder head of some internalcombustion engines and ignites compressed aerosol gasoline bymeans of an electric spark


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Basic Engine TermsInlet valveOne way valve that allows air into a compressor

Naturally aspiratedAn internal combustion engine devoid of forced induction methods

NOxA chemical term for nitrogen oxides produced during combustion and acontributor to smog and acid rain

Outlet valve (exhaust valve)One way valve that allows compressed air out of a compressor

Piston

Rod inside a cylinder that is moved by pneumatic pressure


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CarburetorThe carburetor works on Bernoulli's principle:the faster air moves, the lower its staticpressure, and the higher its dynamicThe carburetor is a device that vaporizesgasoline and mixes it with air in the proper ratiofor combustion in an internal combustionengine. pressure.


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CarburetorThe carburetor has a FLOAT CHAMBER that issupplied with fuel from the FUEL TANK.

The fuel is forced through a FUEL FILTER underpressure from the FUEL PUMP.The float chamber contains a FLOAT VALVE thatregulates the flow of fuel into the chamber.When the float chamber is full of fuel, the float

valve stops the flow of fuel until needed again.


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Carburetor


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FunctionThe function of the carburetor is to supply theproper fuel-air ratio to the engine cylinder duringsuction created by the downward movement of

the piston.As the piston moves downward a pressuredifference is created betweenthe atmosphere and the cylinder which leads tothe suction of air in the cylinder.This sucked air will also carry with it some droplets

of fuel discharged from a tube.The rate at which fuel is discharged into the air willdepend upon the pressure difference created.


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Advantages

Cheaper to BuyCheaper to TuneEasier to Tune


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DisadvantagesIdleInternal Problems

A busted connection rod, a hole in the piston, abent valve or a destroyed head gasket, maycause compression problems, according to RCTrucks.

Fuel/Air Mixture Some carburetors do not have adequate fuel/airmixture, which usually occurs after the motorcyclehas not been operated for a while. The gasoline inthe motorcycle decomposes and clogs thecarburetor circuits, according to RC Trucks.


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Fuel InjectionFuel Injection is a technology that is being usedin bikes and cars these days.The technology is used to eliminate the needfor carburetors.The technology helps the engine to supply fueldirectly to the cylinder in the intake manifold,eliminating the use of carburetor to muchextent.


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Function of Fuel Injection

Filter the fuelMeter or measure the correct quantity offuel to be injectedTime of fuel injectionControl the rate of fuel injectionAtomize or break up the fuel to fine

particlesProperly distribute the fuel in thecombustion chamber


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Advantages of Fuel InjectionUniform Air/Fuel Mixture Distribution Each cylinder has its own injector which delivers fuel directly to the intakevalve.Highly Accurate Air/Fuel Ratio Control Throughout All Engine Operating Conditions EFI supplies a continuouslyaccurate air/fuel ratio to the engine no matter what operating conditionsare encountered.Superior Throttle Response and Power This improves torque and throttle response.Excellent Fuel Economy With Improved Emissions Control Cold engine and wide open throttle enrichment can be reduced with an EFIengine because fuel puddling in the intake manifold is not a problem.Improved Cold Engine Start ability and Operation The combination of better fuel atomization and injection directly at theintake valve improves ability to start and run a cold engine.

Simpler Mechanics, Reduced Adjustment Sensitivity The EFI system does not rely on any major adjustments for cold enrichmentor fuel metering. Because the system is mechanically simple, maintenancerequirements are reduced.


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Disadvantages of EFI

Every system has its own share of benefits and risks.So does the fuel injection system, though the risksare very minimal. Due to the high pressuredeveloped in the engine, a fuel injection systemcauses some potential hazards. A residual pressuremay remain in the engine even after the engine isturned off and it may cause an injury to theoperator

The EFI system does not rely on any majoradjustments for cold enrichment or fuel metering.Because the system is mechanicallysimple, maintenance requirements are reduced.


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Types of Fuel Mixtures

Rich MixtureLean MixtureChemically Balanced


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Combustion ChambersThe combustion chamber is the areainside the engine where the fuel/airmixture is compressed and then ignited.Air-fuel mixture is injected in the chamberwhere it is burned with the help of spark orcompression.


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COMBUSTION CHAMBER DESIGN

Open ChamberDisc typeWedgeHemispherical

Bowl-in-pistonDivided Chamber (For CI)

Swirl chamberPre-chamber

Divided Chamber(For SI)CVCCOther designs


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HEMISPHERICAL/PENT-ROOF OR THEHEMI COMBUSTION CHAMBER


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WEDGE-SHAPED CHAMBERS

Used over the years by almost everymanufacturer, this type of chamber resemblesan inclined basin recessed into the deck of thehead.

Inline valves are normally tilted toaccommodate the sloping roof of this design. The spark plug is located on the thick side ofthe wedge and is usually positioned midway

between the valves.


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BATHTUB OR HEART-SHAPEDCOMBUSTION CHAMBER

The bathtub designation is generallyreserved for any chamber that's not a

wedge or hemispherical.Most domestic engines of pushrod designhave used it in varying forms.In some instances the shape of thecombustion chamber was almost oval,with later trends being the more efficientheart shape.


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DESIGN CONSIDERATIONThe distance travelled by the flame frontshould be minimized.

The exhaust valve (s) and sparkplug (s) should be close together.There should be sufficient turbulence.The end gas should be in a cool partof the combustion chamber


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LIQUEFIED PETROLEUM G AS (LPG)LPG (Liquefied Petroleum Gas), has manyuses; from heating to vehicles. It is made

up of hydrocarbon gases. When used forvehicles, LPG is a mixture of propane andbutane (this is called auto gas). Whencompressed, it turns into liquid form. 1L of

LPG liquid is equivalent to 270L of LPGvapors.


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ADVANTAGES AND DISADVANTAGES LPG A DVANTAGES LPG D ISADVANTAGES

LPG is cheaper than petrol (up to50%)It produces less exhaust emissionsthan petrolIt is better for the engine and it canprolong engine lifeIn some vehicles, it can providebetter performanceHas a higher octane rating than

petrol (108 compared to 91)

It isn't highly availableThe initial cost for converting yourvehicle to LPG can cost up to $3000.However the average car can repaythe cost of the conversion in about 2yearsIt has a lower energy density thanpetrolNo new passenger cars come readily

fitted with LPG (they have to beconverted)The gas tank takes up a considerableamount of space in the car boot


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C OMPRESSED NATURAL G AS (CNG)Compressed natural gas (CNG) is a fossilfuel substitute for gasoline (petrol), diesel,

or propane/LPG.CNG may also be mixed with biogas,produced from landfills or wastewater,which doesn't increase the concentration

of carbon in the atmosphere.

C G A C G


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CNG A DVANTAGES CNG D ISADVANTAGES Is more environment friendly thanoil or coal? It is largely because ofthe fact that it has only onecarbon, and hence, produces

fewer emissions. It is a known factthat for same amount of heat, itemits 30% less carbon dioxide thanburning oil and 45% less carbondioxide than burning coal, thereby,improving the quality of air.Is cheap (less expensive thangasoline), and therefore, very cost-effective.Can be safely stored and burned.Most of its natural reserves are stillunderutilized.Emits 60-90% less smog-producing

pollutants.Due to clean burning process,doesn't produce ashes afterenergy release.Has high heating value of 24,000Btu per pound.

One disadvantage of natural gasthat is often credited as anadvantage by experts is that it's anon-renewable energy resource. Its

availability is finite. Critics also pointthat its extraction leaves out largecraters within the earth.Is highly volatile (highly flammable),and can be dangerous, if handledcarelessly.Is colorless, odorless, and tasteless,that makes detection of its leakvery difficult.In gas pipelines, a substance(contains carbon monoxide) thathas a strong odor is added to helpdetect a leak. But, these

substances may be harmful andcause deaths. In fact, natural gasuse is the most common cause ofcarbon monoxide deaths.Constructing and managing suchpipelines cost a lot.


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LIQUEFIED NATURAL G AS (LNG)For certain applications where weight andvehicle range are critical; LNG may be the

perfect choice.LNG systems operate at low pressure and canstore as much as 2.5 times the fuel in thesame space as conventional CNG systems.LNG is transported and stored at extremelylow temperatures and requires the use ofvacuum-insulated storage tanks.


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LNG A DVANTAGES LNG D ISADVANTAGES Few tanks , less space requirementsGreater fuel densityLower weight storage

The complexity of tanksPressure and temperaturemanagement of the fuel to theengine is more complexHigh maintenance cost of cryogenicpartsUse the fuel or lose itReliability is challengingThe life cycle fuel cost over CNGmaybe the higher


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Cetane vs OctaneThe Octane Number of a gasoline is defined as thevolume percent of isooctane(2,2,4-trimethylpentane,an isomer of octane) in a blend of isooctane and n-heptane whereas The cetane number of a fuel isdefined as the volume percent of n-hexadecane ina blend of n-hexadecane and 1-methylnaphthalenethat gives the same ignitiondelay period as the test sample.The octane Number is a measure of the auto ignitionresistance of gasoline (petrol) and other fuels used in

spark-ignition internal combustion engines. It's ameasure of anti-detonation of a gasoline or fuel orThe Cetane Number is a measure of the combustionquality of diesel fuel under compression.


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Cetane vs OctaneIsooctane is given a maximum octane number, i.e.100. N-heptane is given a minimum octanenumber, i.e. 0 whereas N-hexadecane is given a

maximum octane number, i.e. 100. 1-methylnaphthalene is given a minimum octanenumber, i.e. 0.Octane numbers are only used between 0and100. The fuels having better anti-knocking propertythan isooctane are rated in other scales likeoctane Performance whereas Cetane numbersare only used for the relatively light distillate dieseloils. For heavy (residual) fuel oil two other scale areused CCAI and CII.


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Cetane vs OctaneOctane number is actually a measure of a fuel's autoignition (prematurely) delay; the time period between thestart of injection and start of combustion (ignition) of thefuel. In a particular internal combustion engine, higheroctane fuels will have larger ignition delay periods thanlower octane fuels whereas Cetane number is actually ameasure of a fuel's ignition delay; the time period betweenthe start of injection and start of combustion (ignition) ofthe fuel. In a particular diesel engine, higher cetane fuelswill have shorter ignition delay periods than lower cetanefuels.The higher the octane number the better is the resistanceof Gasoline to combustion prematurely, known as Knockingwhereas The Higher Cetane number means that the Dieselwill ignite readily and, therefore, perform better in a dieselengine.


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Lubrication System in IC EnginesIn an IC engine the engine parts rub witheach other and causes friction

Heat is generated due to that friction andcause wear easily


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Function of LubricationReduces friction between moving partsReduces wear and tearsMinimize power losses due to frictionProvide cooling effectReduces noises created by moving parts


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Parts that required lubricationCrank shaftCrank pinBig and small end of the connecting rodPiston pinInternal surfaces of the cylinder wallsPiston ringsValve mechanisms


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Lubrication SystemsThe main lubrication systems are:

Petrol lubrication system or Mist lubricationsystem.Wet sump lubrication system.


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Disadvantage If the added oil is less, there will not besufficient lubrication and even result inseizure of the engineIf the added oil is more, it will lead toexcess exhaust smoke and carbon

deposits in the cylinder exhaust parts andspark plugs


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Pressure-Feed SystemIn the pressure-feed system, oil is forced by the oil pumpthrough oil lines and drilled passageways.The oil, passing through the drilled passageways underpressure, supplies the necessary lubrication forthe crankshaft main bearings, the connecting-rod bearings piston-pin bushings, camshaft bearings, valvelifters, valve push rods, and rocker studs.Oil passing through the oil lines is directed to the timinggears and the valve rocker shafts in order to lubricate theseparts. The cylinder walls are lubricated by oil thrown off theconnecting-rod and piston-pin bearings.

Some engines have oil spit holes in the connecting rodsthat line up with drilled holes in the crankshaft journal duringeach revolution, and through or spit a steam of oil onto thecylinder walls.


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The Splash systemThe splash system is used only on small four-stroke-cycle engines such as lawn mowerengines. As the engine is operating, dipperson the ends of the connecting rods enter theoil supply; pick up sufficient oil to lubricate theconnecting-rod bearing, and splash oil to theupper parts of the engine. The oil is thrown up as droplets, or fine spray,which lubricates the cylinder walls, piston pinsand valve mechanism.


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Full Force Feed In a full force-feed lubrication system, themain bearings, rod bearings, camshaftbearings, and the complete valve

mechanism are lubricated by oil underpressure.The full force-feed lubrication system provideslubrication under pressure to the pistons andthe piston pins.This is accomplished by holes drilled thelength of the connecting rod, creating an oilpassage from the connecting rod bearing


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Thank YouFor your attention!

internal combustion engine course

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