PowerPoint ® Presentation Engine Operation Engine Components Four-Stroke Cycle Engines Engine Output

PowerPoint® PresentationPowerPoint® Presentation

Engine OperationEngine Operation

Engine Components • Four-Stroke Cycle Engine Components • Four-Stroke Cycle Engines • Engine OutputEngines • Engine Output

Chapter 3 — Engine OperationChapter 3 — Engine Operation

CompetenciesCompetencies List the components of an engine block.List the components of an engine block. Describe a cylinder head.Describe a cylinder head. Explain the operation and components of a crankshaft.Explain the operation and components of a crankshaft. Describe pistons and piston rings.Describe pistons and piston rings. Explain the function of connecting rods and bearings.Explain the function of connecting rods and bearings.


CompetenciesCompetencies Describe the flywheel and valve train.Describe the flywheel and valve train. Compare the operation of four-stroke cycle and two-Compare the operation of four-stroke cycle and two-

stroke cycle engines.stroke cycle engines. Describe valving systems.Describe valving systems. Explain important features of diesel engines.Explain important features of diesel engines. Explain measurement of engine output.Explain measurement of engine output.


How it worksHow it works

The internal combustion engine converts The internal combustion engine converts potential chemical energy into potential chemical energy into mechanical energymechanical energy Is done by heat derived from a fuel sourceIs done by heat derived from a fuel source

Approximately 30% of energy released in Approximately 30% of energy released in engine is converted into workengine is converted into work Remaining energy lost in form of heat & Remaining energy lost in form of heat &

friction in enginefriction in engine


It’s Got To Hold UpIt’s Got To Hold Up

Components are designed to convert Components are designed to convert energy for maximum efficiencyenergy for maximum efficiency They must withstand heat and stress They must withstand heat and stress

generated inside engine during operationgenerated inside engine during operation Must meet size and weight requirementsMust meet size and weight requirements


Engine BlocksEngine Blocks

cylinder blockcylinder block cylinder borecylinder bore cooling finscooling fins valve train valve train

componentscomponents

crankcasecrankcase


Engine BlockEngine Block

Main structure of engineMain structure of engine Supports & maintains alignments of Supports & maintains alignments of

internal & external componentsinternal & external components Block can be produced as one-piece or Block can be produced as one-piece or

two-piece unittwo-piece unit


Cylinder BoreCylinder Bore

Hole in block that Hole in block that

aligns and directs piston aligns and directs piston

during movementduring movement


StrokeStroke

Stroke is the linear distance the piston travels Stroke is the linear distance the piston travels in bore from top dead center (TDC) to bottom in bore from top dead center (TDC) to bottom dead center (BDC)dead center (BDC) TDC point in which piston is closest to cylinder head TDC point in which piston is closest to cylinder head

before piston moves back down cylinderbefore piston moves back down cylinder BDC point which piston is farthest from cylinder BDC point which piston is farthest from cylinder

head before piston moves back up cylinderhead before piston moves back up cylinder


DisplacementDisplacement

Displacement (swept volume) that a Displacement (swept volume) that a piston displaces in an engine when it piston displaces in an engine when it travels from TDC to BDC during same travels from TDC to BDC during same piston strokepiston stroke


Calculating DisplacementCalculating Displacement

When bore and stroke are known then When bore and stroke are known then displacement can be founddisplacement can be found D=.7854 * B2 * SD=.7854 * B2 * S D = displacement (in cubic inches)D = displacement (in cubic inches) .7854 = constant.7854 = constant B2 = bore squared in inchesB2 = bore squared in inches S = Stroke in inchesS = Stroke in inches


Displacement ExampleDisplacement Example

An engine has a 2.5” bore & a 2” stroke. An engine has a 2.5” bore & a 2” stroke. Figure out displacement:Figure out displacement: D=.7854 * (2.5*2.5) * 2D=.7854 * (2.5*2.5) * 2 D = .7854 * 6.25 * 2D = .7854 * 6.25 * 2 D = 9.8175D = 9.8175 D = 9.82 cubic inchesD = 9.82 cubic inches


One More Time!!One More Time!!

What is the displacement of a single-What is the displacement of a single-cylinder engine that has a 3.25” bore and cylinder engine that has a 3.25” bore and a 3.375” stroke?a 3.375” stroke? D = .7854 * (3.25*3.25) * 3.375D = .7854 * (3.25*3.25) * 3.375 D = .7854 * 10.5625 * 3.375D = .7854 * 10.5625 * 3.375 D = 27.9982D = 27.9982 D = 28 cubic inchesD = 28 cubic inches


Do That Times 2Do That Times 2

For multiple-cylinder engines:For multiple-cylinder engines: Multiply the displacement of the single-Multiply the displacement of the single-

cylinder by the total number of cylinderscylinder by the total number of cylinders

Generally, the larger the displacement, Generally, the larger the displacement, the more power it can producethe more power it can produce


Air vs. Liquid CooledAir vs. Liquid Cooled

Air cooled enginesAir cooled engines Have cooling fins on exterior of blockHave cooling fins on exterior of block

Thin cast strips designed to provide efficient air Thin cast strips designed to provide efficient air circulation & head dissipation away from block circulation & head dissipation away from block into air streaminto air stream

Increases surface area of block contacting Increases surface area of block contacting ambient (existing) air for cooling efficiencyambient (existing) air for cooling efficiency Fins cast into or bolted onto flywheel act as fan Fins cast into or bolted onto flywheel act as fan

blades & give air circulation around block & headblades & give air circulation around block & head





Liquid cooled enginesLiquid cooled engines Have channels (sleeves) drilled or cast into Have channels (sleeves) drilled or cast into

block to allow coolant to pass through block to allow coolant to pass through engine and cool itengine and cool it Similar to engine in automobileSimilar to engine in automobile


Cylinder HeadsCylinder Heads

engine component engine component fastened to the fastened to the end of the cylinder end of the cylinder block farthest from block farthest from the crankshaftthe crankshaft

head gasket is head gasket is filler materialfiller material


CrankshaftsCrankshafts

convert linear convert linear motion of pistons motion of pistons to rotary motionto rotary motion

crankpin journalcrankpin journal bearing journalbearing journal counterweightcounterweight crankgearcrankgear


CrankcaseCrankcase Houses and supports crankshaftHouses and supports crankshaft In 4-stroke acts as oil reservoir for lubricationIn 4-stroke acts as oil reservoir for lubrication May have multiple parts like a sump or crankcase May have multiple parts like a sump or crankcase

covercover Sump is removable & acts like oil reservoir & provides access Sump is removable & acts like oil reservoir & provides access

to internal partsto internal parts Has bearing surface for vertical shaft engines & forms lower Has bearing surface for vertical shaft engines & forms lower

section of enginessection of engines Horizontal shaft engines have no sump as block serves as oil Horizontal shaft engines have no sump as block serves as oil

reservoirreservoir Crankcase cover provides access to internal parts in Crankcase cover provides access to internal parts in

crankcase & supports crankcasecrankcase & supports crankcase


Crankcase BreatherCrankcase Breather

Relieves crankcase pressure created by Relieves crankcase pressure created by reciprocating motion of the piston during reciprocating motion of the piston during operationoperation When piston moves towards TDC volume in crank When piston moves towards TDC volume in crank

increases resulting in lower existing pressure in increases resulting in lower existing pressure in crankcasecrankcase

When piston toward BDC volume in crankcase When piston toward BDC volume in crankcase decreases generating higher than ambient pressure decreases generating higher than ambient pressure in crankcasein crankcase


Crankcase BreatherCrankcase Breather Acts as a check valve allowing more air to Acts as a check valve allowing more air to

escape than can enter crankcaseescape than can enter crankcase Maintains pressure less than atmospheric pressure Maintains pressure less than atmospheric pressure

(14.7 PSI at sea-level)(14.7 PSI at sea-level) Gases, partially spent combustion gases & other Gases, partially spent combustion gases & other

engine gases are then routed to carburetorengine gases are then routed to carburetor Also serves as a oil mist collectorAlso serves as a oil mist collector

Prevents crankcase oil from escaping whenever Prevents crankcase oil from escaping whenever breather opensbreather opens

Required on most 4-stroke enginesRequired on most 4-stroke engines


Crankcase/Cylinder BlockCrankcase/Cylinder Block


Cylinder BlocksCylinder Blocks

Cast from materials strong enough to Cast from materials strong enough to withstand the heat & stress inside the withstand the heat & stress inside the engine during operationengine during operation

Must meet size & weight requirements of Must meet size & weight requirements of specific applicationspecific application


Cylinder BlocksCylinder Blocks

Common constructionCommon construction Cast aluminum alloyCast aluminum alloy

Lightweight & dissipates heat more rapidly than cast ironLightweight & dissipates heat more rapidly than cast iron Cast ironCast iron

Heavier & more expensive Heavier & more expensive More resistant to wear & less prone to heat distortionMore resistant to wear & less prone to heat distortion Cast aluminum alloy with cast iron cylinder sleevesCast aluminum alloy with cast iron cylinder sleeves Combine both for maximum strengthCombine both for maximum strength


Cylinder HeadsCylinder Heads


Cylinder HeadCylinder Head Cast aluminum alloy or cast ironCast aluminum alloy or cast iron Fastened to end of cylinder block farthest from Fastened to end of cylinder block farthest from

crankshaftcrankshaft Head gasket used between both to seal combustion Head gasket used between both to seal combustion

chamberchamber Made from soft metals & graphite layered togetherMade from soft metals & graphite layered together Allows for even heat distribution between block & headAllows for even heat distribution between block & head

Some 2-stroke engines have head & block cast Some 2-stroke engines have head & block cast together called a jugtogether called a jug Provides maximum structural integrity & eliminates potential Provides maximum structural integrity & eliminates potential

for leaks in combustion chamberfor leaks in combustion chamber


PistonsPistons Slides back and forth in Slides back and forth in

the cylinder borethe cylinder bore Piston pinPiston pin SkirtSkirt Ring grooveRing groove Piston ringsPiston rings

Commonly made from Commonly made from cast ironcast iron Compression RingCompression Ring Wiper RingWiper Ring Oil ringOil ring


PistonsPistons Generally made of cast aluminum alloyGenerally made of cast aluminum alloy Material will always be different than engine Material will always be different than engine

block to prevent piston merging into blockblock to prevent piston merging into block Excellent thermal conductivityExcellent thermal conductivity

Ability of material to conduct & transfer heatAbility of material to conduct & transfer heat Aluminum expands when heated so proper Aluminum expands when heated so proper

clearance must be providedclearance must be provided Insufficient clearance can cause piston to seize in boreInsufficient clearance can cause piston to seize in bore Excessive clearance can cause loss of compression & Excessive clearance can cause loss of compression &

increase piston noiseincrease piston noise


Connecting RodsConnecting Rodsand Bearingsand Bearings

connecting rod connecting rod transfers motion transfers motion from piston to from piston to crankshaftcrankshaft

bearings reduce bearings reduce friction, maintain friction, maintain clearanceclearance


CrankshaftCrankshaft



Converts liner motion of piston into rotary Converts liner motion of piston into rotary motionmotion

Main rotating component of engineMain rotating component of engine Commonly made of ironCommonly made of iron Vertical or Horizontal orientationVertical or Horizontal orientation



Components:Components: Crankpin JournalCrankpin Journal

Precision ground surface provides pivot point to Precision ground surface provides pivot point to attach connecting rod to crankshaftattach connecting rod to crankshaft

Bearing JournalsBearing Journals Precision ground surface which the crankshaft Precision ground surface which the crankshaft

rotatesrotates Mates with bearing surface in cylinder blockMates with bearing surface in cylinder block



CounterweightsCounterweights Protruding mass used to partially balance Protruding mass used to partially balance

the forces of a reciprocating pistonthe forces of a reciprocating piston



Crank gearCrank gear Gear located on crankshaft used to drive Gear located on crankshaft used to drive

other parts of an engineother parts of an engine Not required on all small enginesNot required on all small engines

Power take-off (PTO)Power take-off (PTO) Extension of crankshaft that allows engine Extension of crankshaft that allows engine

to transmit power to an applicationto transmit power to an application


Flywheels and Valve TrainsFlywheels and Valve Trains

a flywheel is a disk mounted at one end a flywheel is a disk mounted at one end of a crankshaftof a crankshaft provides inertia for the engineprovides inertia for the engine maintains crankshaft rotation between maintains crankshaft rotation between

combustion intervalscombustion intervals

a valve train controls the flow of gases a valve train controls the flow of gases into and out of the combustion chamberinto and out of the combustion chamber



intake eventintake event introduces air and fuel (or just air in a diesel introduces air and fuel (or just air in a diesel

engine) to the combustion chamber engine) to the combustion chamber piston moves from TCD to BDCpiston moves from TCD to BDC

compression eventcompression event air and fuel (or just air in a diesel engine) in air and fuel (or just air in a diesel engine) in

combustion chamber is compressed in the combustion chamber is compressed in the cylindercylinder



ignition (combustion) eventignition (combustion) event charge is ignited and rapidly oxidized to charge is ignited and rapidly oxidized to

release energy release energy

power eventpower event expanding gases force the piston head expanding gases force the piston head

away from the cylinder headaway from the cylinder head



exhaust eventexhaust event spent gases are removed from the chamber spent gases are removed from the chamber

and released to atmosphere and released to atmosphere

valve overlap is the point when both valve overlap is the point when both intake and exhaust valves are openintake and exhaust valves are open


Engine OutputEngine Output

measured by torque and horsepowermeasured by torque and horsepower units of measurement of horsepowerunits of measurement of horsepower

brake, friction, and indicated horsepowerbrake, friction, and indicated horsepower dynamometer measures torque, load, dynamometer measures torque, load,

speed, and horsepowerspeed, and horsepower


Engine OutputEngine Output

factors affecting engine outputfactors affecting engine output displacementdisplacement volumetric efficiencyvolumetric efficiency thermal efficiencythermal efficiency air densityair density


Chapter 3 ReviewChapter 3 Review

What is the function of a crankshaft?What is the function of a crankshaft? A crankshaft is an engine component that A crankshaft is an engine component that

converts the linear (reciprocating) motion of the converts the linear (reciprocating) motion of the piston into rotary motion.piston into rotary motion.

What are the five events of four-stroke cycle What are the five events of four-stroke cycle engines?engines? The five events of four-stroke cycle engines are The five events of four-stroke cycle engines are

intake, compression, ignition, power, and intake, compression, ignition, power, and exhaust.exhaust.

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PowerPoint ® Presentation Engine Operation Engine Components Four-Stroke Cycle Engines Engine Output