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BITS PilaniK K Birla Goa Campus

I.C. ENGINES

(ME F242)Dr. RANJIT S PATIL

Mechanical Engineering

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BITS PilaniK K Birla Goa Campus

Lecture No. 1

Ch. 1: Introduction to I.C. Engines

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Its all about engines .

9= 32

5T F T C

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Applications

0.01 273.16 32

22

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0 0

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1860-- - J.J.E. Lenoir (France) (Gas Engines)

1867 --- Nicolaus A. Otto & E. Langen

1873 --- Brayton Engine (American)

1876 --- Otto -- 4- Stroke atented

History

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1881 --- Karl Benz & Dugald Clark - Germany (2-Stroke)

1885 --- Atkinson Engine (UK)

1892 --- Rudolf Diesel C.I. Engine

1957 --- Felix Wankel

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The Diesel Engine

A History from 1870 Steam to Internal

Story

Introduction - History

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BITS PilaniK K Birla Goa Campus

Lecture No. 2

Ch. 1: Introduction to I.C. Engines

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Heat engineIt can be defined as any engine that converts thermalenergytomechanical workoutput.

steam engine,

diesel en ine

Introduction

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gasoline (petrol) engine.

On the basis of how thermal energy is being delivered toworking fluid of the heat engine, heat engine can beclassified as:

Internal combustion engine (IC Engine)

External combustion engine.

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Internal combustion engine:combustiontakes place within the engine

Gasoline (petrol) or diesel engines

External combustion en ine:

Introduction

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combustiontakes place outside the engine

Steam engine or steam turbine is an example of

external combustion engine, where the working

fluid is steam.

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Internal combustion engines may be classified as :

Spark Ignition engines.

Compression Ignition engines.

Introduction

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combustion process in each cycle is started by use of anexternal spark.

Compression ignition engine (CI engine): An engine inwhich the combustion process starts when the air-fuelmixture self ignites due to high temperature in thecombustion chamber caused byhigh compression.

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Spark ignition and Compression Ignition engine operate oneither a four stroke cycle or a two stroke cycle.

Four stroke cycle :It has four piston strokes over

two revolutions of crank shaft for each cycle.

Introduction

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Two stroke cycle :It has two piston strokes over

one revolution for each cycle.

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Engine Components

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Engine Components

Cylinder Block: It is the main supporting structures for thevarious parts. Part that covers and encloses the cylinder.

Cylinder head is mounted on the cylinder block.

It contains cooling fins or water jackets.

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Engine Components

Cylinder : The circular cylinders in theengine block in which the pistonsreciprocate back and forth.

Head :The piece which closes the end of

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,the clearance volume of the combustionchamber.

Piston : A movable part fitted into acylinder, which can receive and transmitpower. Through connecting rod, pistonforces the crank shaft to rotate.

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Engine Components

Combustion chamber:The end of the cylinder between thehead and the piston face where combustion occurs.

The size of combustion chamber continuously

changes from minimum volume when the piston is at

TDC to a maximum volume when the piston at BDC.

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Engine Components

Crankshaft : Rotating shaft through which engine workoutput is supplied to external systems.

The crankshaft is connected to the engine block with

the main bearings.

It is rotated b the reci rocatin istons throu h the

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connecting rods connected to the crankshaft,

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Engine Components

Connecting rod :Rod connecting the piston with the rotatingcrankshaft, usually made of steel or alloy forging in mostengines but may be aluminum in some small engines.

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Engine Components

Piston rings: Metal rings that fitinto circumferential groovesaround the piston and form asliding surface against the cylinder

walls.

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,are compression rings (sealing thecompression pressure in thecylinder) and the third is an oil ring

(scrapes excessive oil from thecylinder walls)

Two Stroke: Two Rings Both therings are Compression rings.

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Engine Components

Exhaust manifold : Piping system which carries exhaustgases away from the engine cylinders, usually made of castiron .

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Engine Components

Spark plug : Electrical device used toinitiate combustion in an SI engine bycreating high voltage discharge acrossan electrode gap.

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Cylinder Exhaust Valvelets the exhaust gases

escape the combustion Chamber.

(Diameter is smaller then Intake valve) Intake Valve lets the air or air fuel

mixture to enter the combustionchamber. (Diameter is larger than the

exhaust valve)

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Engine Components

Exhaust System: Flow system forremoving exhaust gases from thecylinders, treating them, and exhaustingthem to the surroundings.

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It consists of an exhaust manifold which carries theexhaust gases away from the engine, a thermal or catalyticconverter to reduce emissions, a muffler to reduce enginenoise, and a tailpipe to carry the exhaust gases away from

the passenger compartment.

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Engine Components

Flywheel :Rotating mass with a large moment of inertiaconnected to the crank shaft of the engine.

The purpose of the flywheel is to store energy and furnishlarge angular momentum that keeps the engine rotating

between power strokes and smooth's out engine

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.

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Engine Components

Animated Engine

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Engine Components

Engine components assembly

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Lecture No. 3

Ch. 1: Introduction to I.C. Engines

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Engine Terminology orNomenclature

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Engine Terminology

Top Dead Center (TDC): Position of the piston when itstops at the furthest point away from the crankshaft.

Top because this position is at the top of the

engines (not always), and dead because the

piston stops as this point.

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Some sources call this position Head End Dead

Center (HEDC).

Some source call this point TOP Center (TC).

When the piston is at TDC, the volume in the

cylinder is a minimum called the clearance

volume.

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Engine Terminology

Bottom Dead Center (BDC) :Position of the piston whenit stops at the point closest to the crankshaft.

Some sources call this Crank End Dead Center

(CEDC) because it is not always at the bottom of

the engine. Some source call this point Bottom

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Center (BC).

Stroke :Distance traveled by the piston from one extreme

position to the other : TDC to BDC or BDC to TDC.

Bore : It is defined as cylinder diameter or piston facediameter; piston face diameter is same as cylinderdiameter( minus small clearance).

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Engine Terminology

Swept volume/Displacement volume :Volume displacedby the piston as it travels through one stroke.

Swept volume is defined as stroke times bore

area.

Displacement can be given for one cylinder or

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cylinders).Clearance volume : It is the minimum volume of the

cylinder available for the charge (air or air fuel mixture)

when the piston reaches at its outermost point (top deadcenter or outer dead center) during compression stroke ofthe cycle.

Minimum volume of combustion chamber with

piston at TDC.

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Engine Terminology

Compression ratio : The ratio of total volume toclearance volume of the cylinder is the compression ratioof the engine.

Typically compression ratio for SI engines varies

form 6 to 10 and for CI engines it varies from 16

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to 20.

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Working Principle of SI Engine4 Stroke

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Working Principle of SI Engine4 Stroke

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W ki P i i l f CI E i

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Working Principle of CI Engine4 Stroke

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Working Principle of CI Engine

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Working Principle of CI Engine4 Stroke

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Lecture No. 4

Ch. 1: Introduction to I.C. Engines

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HCCI Engine

Sterling Engine

Wankel Engine

Nonconventional Engines(only for knowledge)

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SI Engine CI Engine

1.OTTO Cycle for Petrol (Gasoline) 1.Diesel Cycle for Diesel Fuel

2.Constant Volume Heat Addition 2.Constant Pressure Heat Addition

3. Air + Petrol enters at Suction

stroke

3.Only air enters at suction stroke, at

the end of compression stroke Diesel is

injected

Comparison: SI vs CI Engines

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.

Ignition system are required.

.

required.

5.Compression ratio = 6 to 10 5.Compression ratio = 16 to 20

6. Lower Compression ratio, hence

lower thermal efficiency

6. Higher Compression ratio, hence

higher thermal efficiency

7. Lower in weight due to lower

peak pressure. Homogeneous

combustion.

7.Higher in weight due to higher peak

pressure. Heterogeneous combustion.

Working Principle of Two

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Working Principle of TwoStroke IC Engines

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4 St k V 2 St k E i

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4 Stroke Engine 2 Stroke Engine

1. One power stroke per 2

revolutions of crank shaft hence its

turning moment is not uniform so

heavier flywheel is needed.

1. One Power stroke for every

revolution of crank shaft so its turning

moment is uniform so lighter flywheel

may be required.

2. Because of One power stroke per 2

revolutions of crank shaft, power

produced by same size or same speed

2. Because of One power stroke for

every revolutions of crank shaft,

power produced by same size or

4 Stroke Vs 2 Stroke Engines

engine is less than 2 stroke engine. Or

for the same power output, engine

will be heavier.

same speed engine is theoretically

double than 4 stroke engine*. (Please

see next slide) or for the same power

output as 4 stroke engine, 2 stroke

engine will be light is weight.

3.Because of less power generation,

required lesser cooling and

lubrication.

3.Because of high power generation,

required greater cooling and

lubrication.

4.Valve mechanism is used. 4.Ports are used so it is mechanically

simpler