Chapter IChapter IIntroduction to IC Engines

By

Dr. S. Murali

Professor & Head

Dept. of Mechanical Engineering

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

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

Internal Combustion engine

External Combustion engine

IC Engine(Reciprocating)

CylinderGudgeon pin

Cooling Jacket

Crank Shaft

CrankcaseCrank Web

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.

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

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 )(

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

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)

Application

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

Application

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

Basic Engine Design

HorizontalVertical

Slanted

Basic Engine Design

VIn-line

Horizontally opposed

Basic Engine Design

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)

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

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)

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

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

CLASSIFICATION OF IC ENGINESMi t P tiMixture Preparation

1. Carburetion2. Fuel Injection

(i) Diesel(ii) Gasoline

(a) Manifold (b) Port (c) Cylinder

CLASSIFICATION OF IC ENGINESI itiIgnition

1. Spark Ignition(a) Conventional

(i) Battery(ii) Magneto

(b) Other methods2. Compression Ignition

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

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

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.

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.

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.

Cooling

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

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

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

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

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

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

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

Working of 4 stroke CI Engine

additionheatvloumeconstncompressioisentropic

induction

.322110

→→→

j tih tpressureconst

ansionisentropic.014exp43

→→→

rejectionheat

Intake / exhaust0

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

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

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)

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