introduction to ic engines
TRANSCRIPT
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Chapter IChapter IIntroduction to IC Engines
By
Dr. S. Murali
Professor & Head
Dept. of Mechanical Engineering
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ThermodynamicsB h f i hi h d l ith H t •Branch of science which deals with Heat and WorkB i i i l•Basic principles–Zeroeth law
• Basis for Temperature measurement• Basis for Temperature measurement–First Law
• Conversion of Energies• Conversion of Energies–Second Law
• Rectifies flaws in First LawRectifies flaws in First Law• Basic theories for Heat Engines development
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Engine & Heat EngineE i D i d t t f Engine : Device used to convert one form of energy another form of energy.
A heat engine diverts some heat as it flows naturally from hot to cold and converts naturally from hot to cold and converts that heat into useful work
Heat Engine:(i) Internal combustion engine(i) Internal combustion engine(ii) External combustion engine
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Internal Combustion engine
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External Combustion engine
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IC Engine(Reciprocating)
CylinderGudgeon pin
Cooling Jacket
Crank Shaft
CrankcaseCrank Web
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Reciprocating IC Engine(Parts)Pi t li d i l i f t l th t •Piston- cylindrical piece of metal that moves up and down the cylinder.
•Piston rings rings provide a sliding seal •Piston rings- rings provide a sliding seal between the piston and cylinder.
•Rings serve two purposes:•Rings serve two purposes:–prevent fuel/air from leaking into the sumpsump
–prevent oil from entering the combustion chamber0
•Combustion chamber- area where combustion and compression takes place.
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Reciprocating IC Engine(Parts)C ti d t th i t t th •Connecting rod- connects the piston to the crankshaft.C k h ft th k h ft t th •Crankshaft- the crankshaft turns the up and down motion of the piston into circular motionmotion
•Sump- (oil pan) contains and collects oil for lubricationfor lubrication
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IC Engine Terminology
Clearance Top dead center(TDC)
Stoke (L)C li d B
Bottom dead center(BDC)
Cylinder Bore(D)
LDLAVVolumeStrokeorntDisplaceme s2
4)( π
=×=VV lC li d )( 4
CS VVvolumeclearancevolumetdispacemenVVolumeCylinder
+=+=)(
SSC VVVVrRationCompressio +=+
== 1)(CCC VVV
p )(
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CLASSIFICATION OF IC ENGINES1 Application1. Application2. Basic Engine Design3. Operating Cycle3. Operating Cycle4. Working Cycle5. Valve/Port Design and Location6. Fuel7. Mixture Preparation8 I iti8. Ignition9. Stratification of Charge10 Combustion Chamber Design10. Combustion Chamber Design11. Method of Load Control12. Coolingg
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CLASSIFICATION OF IC ENGINESApplicationApplication1. Automotive:
(i) Car( )(ii) Truck/Bus(iii) Off-highway
2 Locomotive2. Locomotive3. Light Aircraft4. Marine: (i) Outboard4. Marine: (i) Outboard
(ii) Inboard(iii) Ship
5. Power Generation: (i) Portable (Domestic)(ii) Fixed (Peak Power)(ii) Fixed (Peak Power)
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Application
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CLASSIFICATION OF IC ENGINES6 Agricultural: 6. Agricultural:
(i) Tractors(ii) Pump sets(ii) Pump sets
7. Earthmoving: (i) Dumpers(ii) Tippers(iii) Mining Equipment
8 H U8. Home Use:(i) Lawnmowers(ii) Snow blowers(ii) Snow blowers(iii) Tools
9. Others
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Application
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CLASSIFICATION OF IC ENGINESBasic Engine DesignBasic Engine Design:
1. Reciprocating (a) Single Cylinder(a) Single Cylinder(b) Multi-cylinder
(I) In-line (I) In-line (ii) V (iii) Radial (iv) Opposed Cylinder(v) Opposed Piston
2 R t ( ) Si l R t2. Rotary: (a) Single Rotor(b) Multi-rotor
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Basic Engine Design
HorizontalVertical
Slanted
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Basic Engine Design
VIn-line
Horizontally opposed
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Basic Engine Design
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CLASSIFICATION OF IC ENGINESO ti C lOperating Cycle
• Otto (For the Conventional SI Engine)• Atkinson (For Complete Expansion SI
Engine)Mill (F E l L t I l t V l • Miller (For Early or Late Inlet Valve Closing type SI Engine)Di l (F th Id l Di l E i )• Diesel (For the Ideal Diesel Engine)
• Dual (For the Actual Diesel Engine)
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CLASSIFICATION OF IC ENGINESWo king C cle (St okes)Working Cycle (Strokes)
1. Four Stroke Cycle:(a) Naturally Aspirated(a) Naturally Aspirated(b)Supercharged/Turbocharged
2 Two Stroke Cycle: 2. Two Stroke Cycle: (a) Crankcase Scavenged(b) Uniflow Scavenged(b) Uniflow Scavenged
(i) Inlet valve/Exhaust Port(ii) Inlet Port/Exhaust Valve(ii) Inlet Port/Exhaust Valve(iii) Inlet and Exhaust Valve
May be Naturally Aspirated ay b a u a y sp a dTurbocharged
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CLASSIFICATION OF IC ENGINESVal e/Po t DesignValve/Port Design
1. Poppet Valve2 Rotary Valve2. Rotary Valve3. Reed Valve4 Piston Controlled Porting4. Piston Controlled Porting
Valve Location1 The T-head1. The T head2. The L-head3. The F-head3. The F head4. The I-head: (i) Over head Valve (OHV)
(ii) Over head Cam (OHC)( ) O ad Ca (O C)
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CLASSIFICATION OF IC ENGINESFuelFuel
1.Conventional: (a) Crude oil derived (a) Crude oil derived
(i) Petrol(ii) Diesel
(b) Other sources (i) Coal(ii) W d (i l d bi )(ii) Wood (includes bio-mass)(iii)Tar Sands(iv)Shale(iv)Shale
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CLASSIFICATION OF IC ENGINESFuelFuel
2. Alternate: (a) Petroleum derived (a) Petroleum derived
(i) CNG(Compressed Natural Gas)(ii) LPG(Liquid Petroleum Gas)
(b) Bio-mass Derived (i) Alcohols (methyl and ethyl)(ii) V t bl il(ii) Vegetable oils(iii) Producer gas and biogas(iv) Hydrogen(iv) Hydrogen
3. Blending4. Dual fuelingg
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CLASSIFICATION OF IC ENGINESMi t P tiMixture Preparation
1. Carburetion2. Fuel Injection
(i) Diesel(ii) Gasoline
(a) Manifold (b) Port (c) Cylinder
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CLASSIFICATION OF IC ENGINESI itiIgnition
1. Spark Ignition(a) Conventional
(i) Battery(ii) Magneto
(b) Other methods2. Compression Ignition
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CLASSIFICATION OF IC ENGINESCh St tifi tiCharge Stratification
1. Homogeneous Charge (Also Pre-mixed charge)
2 St tifi d Ch 2. Stratified Charge (i) With carburetion(ii) With fuel injection
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CLASSIFICATION OF IC ENGINESComb stion Chambe DesignCombustion Chamber Design
1. Open Chamber (i) Disc type(i) Disc type(ii) Wedge(iii) Hemispherical(iii) Hemispherical(iv) Bowl-in-piston(v) Other design(v) Other design
2. Divided Chamber(For CI) (For SI) (For CI) (For SI) (i) Swirl chamber (i) CVCC(ii) Pre-chamber (ii) Other designs( ) a b ( ) O d s g s
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CLASSIFICATION OF IC ENGINESM th d f L d C t lMethod of Load Control
1. Throttling: (To keep mixture strength t t) Al ll d Ch C t lconstant) Also called Charge Control
Used in the Carbureted S.I. Engine2 F l C t l (T th i t 2. Fuel Control (To vary the mixture
strength according to load)U d i th C I E iUsed in the C.I. Engine
3. CombinationU d i th F l i j t d S I E iUsed in the Fuel-injected S.I. Engine.
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CLASSIFICATION OF IC ENGINESCoolingCooling
1 Direct Air cooling1. Direct Air-cooling
2 Indirect Air-cooling (Liquid Cooling)2. Indirect Air-cooling (Liquid Cooling)
3 Low Heat Rejection (Semi-adiabatic) 3. Low Heat Rejection (Semi adiabatic) engine.
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CLASSIFICATION OF IC ENGINESCoolingCooling
1 Direct Air cooling1. Direct Air-cooling
2 Indirect Air-cooling (Liquid Cooling)2. Indirect Air-cooling (Liquid Cooling)
3 Low Heat Rejection (Semi-adiabatic) 3. Low Heat Rejection (Semi adiabatic) engine.
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Cooling
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Working of Four Stroke SI Engine
S i l iSequential operations
•Induction Stroke: fill cylinder with air fuelmixture
•Compression Stroke: squeeze mixture
•Power Stroke: burn and extract work
•Exhaust Stroke: empty cylinder of exhaust
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Induction Stroke(1→2)• Piston moves from TDC to BDC • Intake valve - open• Exhaust valve- closed• Engine pulls piston out of cylinder• Low pressure inside cylinder• air fuel mixture (carburretted 14 to 15
on weight basis) enters into cylinder• Flywheel angle of rotation 0-180• Engine does work on the gases during
this stroke
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Compression Stroke(2→3)• Piston moves from BDC to TDC• Intake valve – closed• Exhaust valve- closed• Engine pushes piston into cylinder• Mixture is compressed to high
pressure and temperature• Flywheel angle of rotation 180-360• Engine does work on the gases during
this stroke
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Power Stroke(3→4)
• Piston moves from TDC-BDC • Intake valve - closed• Exhaust valve - closed• Mixture burns to form hot gases• Gases push piston out of cylinder• Gases expand to lower pressure and
temperature• Flywheel angle of rotation 360-540• Gases do work on engine during this
stroke
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Exhaust Stroke• Piston moving up• Intake valve closed• Exhaust valve open
• Engine pushes piston into cylinder• High pressure inside cylinder• Pressure pushes burned gases out of
cylinder• Flywheel angle of rotation 540-720• Engine does work on the gases during
this stroke
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SI Engine Animation & Ideal PV-Diagram
0 1 intake1 2 isentropic compression 2 3 i h i h ti
P 3 2 3 isochoric heating
3 4 isentropic expansion 4 1 0 exhaust
igni
tion
2
4
ust
1 exha
u
Patm
Intake / exhaust
0
V V1V2
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Working of 4 stroke CI Engineti i it i il t SI i• operation is quite similar to SI engine
–HoweverF l I j t d f • Fuel Injectors are used for atomized fuel injection
• Fresh air is entered during induction strokeg
• Heterogeneous mixture is burned because of self ignition of the fuel
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Working of 4 stroke CI Engine
additionheatvloumeconstncompressioisentropic
induction
.322110
→→→
j tih tpressureconst
ansionisentropic.014exp43
→→→
rejectionheat
Intake / exhaust0
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Salient features of 4 stroke engineP id d ith l•Provided with valves
•It requires four strokes
•Two revolution of crank shaft
•One power stroke for every four strokes
•Flywheel stores energy during power stroke and supplies part of energy for idle strokes
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SI engine Vs CI engineDescription SI CIBasic Cycle Otto cycle or constant
volume heat addition cycleDiesel cycle or constant pressure heatvolume heat addition cycle constant pressure heat addition
Fuel Gasoline, a highly volatile Diesel, a non volatile , g yfuel, high self ignition temperature
,fuel, low self ignition temperature
I t d ti f A i t f f l d i i F l i i j t d j t tIntroduction of Fuel
A mixture of fuel and air isintroduced during suction stroke(Induction Stroke)
Fuel is injected just at the end of compression stroke
Load control Quantity governed Quality governed
Fuel Ignition Requires Spark plug Self ignitiong q p p g g
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SI engine Vs CI engine(contd)Description SI CICompression ratio
6-10 16-20ratioThermalefficiency
Low efficiency(Lower compression ratio)
Higher efficiency(higher y p ) y( gcompression ratio)
Weight Lighter in weight(low k )
Heavier(higher peak )peak pressure) pressure)