ic engines ppt lecture no 1

7/24/2019 IC Engines Ppt Lecture No 1

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Introduction to IE

BIRLA INSTITUT

Dr. RaviE

raviinder@pil

ternal Combustiongines

OF TECHNOLOGY AND SCIENCE,

PILANI

Inder Singhail id:ni.bits-pilani.ac.in


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Introduction

=

Heat engine : It can be de

thermal energy to mechanic

engines include: steam engine,engine.

n e as s o ow erma efluid of the heat engine, heat e

combustion engine and extern

ined as any engine that convert

l work output. Examples of hea

diesel engine, and gasoline (petrol

2

nergy s e ng e vere o wor ngine can be classified as an interna

l combustion engine.


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In an Internal combusti

place within working fluid

contaminated with combusti Petrol engine is an e

engine, where the w

and fuel . In an External combusti

energy using boilers by bu

fuel, thus the working fluidcombustion products.

Steam engine is an e

engine, where the wo

on engine, combustion takeof the engine, thus fluid get

on products.ample of internal combustio

rking fluid is a mixture of ai

n engine, working fluid getning fossil fuels or any othe

does not come in contact wit

ample of external combustio

king fluid is steam.


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Classification of Heat Engines


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Internal combustion engines ma

Spark Ignition engine

Compression Ignition

Spark ignition engine (SI

spark.

Compression ignition engin

the combustion process star

ignites due to high temper

caused by high compression.

Spark ignition and C

on either a four stroke

be classified as :

.

engines.

ngine): An engine in which the

(CI engine): An engine in which

s when the air-fuel mixture self

ture in the combustion chamber

mpression Ignition engine operate

cycle or a two stroke cycle.


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Spark Ignition Engine (SI engine):

Figure 1(a)

Compression Ignition Engine (CI

engine):

Figure 1(b)


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Figure 2: Engi e components


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ternal combustion Engine C

. Engine components shown in fi

defined as follows:Block : Body of the engine containing c

Cylinder : The circular cylinders in the

reciprocate back and forth.Head : The piece which closes the end

the clearance volume of the combustion

Combustion chamber:Combustion chamber: The end of theface where combustion occurs.

The size of combustion chamber c

volume when the piston is at TDC

BDC.

omponents:

ure1(a), 1(b) and figure 2 are

linders, made of cast iron or aluminum.

ngine block in which the pistons

f the cylinders, usually containing part o

chamber.

ylinder between the head and the piston

ontinuously changes from minimum

to a maximum volume when the piston


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Crankshaft :Crankshaft : Rotating shaft throuRotating shaft throu

supplied to external systems.supplied to external systems. The crankshaft is connecte

bearings.

It is rotated by the reciprorods connected to the cran

rotation. This offset is so

radius.

Connecting rod : Rod connecting

crankshaft, usually made of steel o

may be aluminum in some small e

Piston rings: Metal rings that fit i

the piston and form a sliding surfa

h which engine work output ish which engine work output is

d to the engine block with the main

ating pistons through the connecti shaft, offset from the axis of

etimes called crank throw or crank

the piston with the rotating

r alloy forging in most engines but

gines.

nto circumferential grooves around

e against the cylinder walls.


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Camshaft : Rotating shaft use

time in the engine cycle, either

hydraulic linkage (push rods, r

Push rods : The mechanical li

valves on overhead valve en i

crankcase.

Crankcase : Part of the engine

In many engines the oil p

housing.

Exhaust manifold : Piping sy

away from the engine cylinder

to push open valves at the proper

directly or through mechanical or

cker arms, tappets) .

kage between the camshaft and

es with the camshaft in the

block surrounding the crankshaft.

n makes up part of the crankcase

tem which carries exhaust gases

, usually made of cast iron .


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Intake manifold :Piping syste

cylinders, usually made of cast

In most SI engines, fuel is adsystem either by fuel injector

The individual pipe to a singl

Carburetor : A device which

the air flow by means of pressur

For many decades it was the

automobile (and other) engin

Spark plug : Electrical device

engine by creating high voltage

which delivers incoming air to the

etal, plastic, or composite material

ed to the air in the intake manifold or with a carburetor.

e cylinder is called runner.

eters the proper amount of fuel int

e differential.

asic fuel metering system on all

s.

sed to initiate combustion in an SI

ischarge across an electrode gap.


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Fuel injector : A pressuriz

incoming air (SI engines )or

Fuel pump : Electricallysupply fuel from the fuel tan

Glow plug : Small electric

the combustion chamber ofthe chamber enough so that

starting a cold engine.

The glow plug is turn off Starter : Several methods a

started by use of an electric

flywheel. Energy is supplied

d nozzle that sprays fuel into th

nto the cylinder (CI engines).

or mechanically driven pump t(reservoir) to the engine.

l resistance heater mounted insid

many CI engines, used to preheacombustion will occur when firs

fter the engine is started.e used to start IC engines. Most ar

otor (starter) geared to the engin

from an electric battery.


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Figure 3 : Engin Terminology


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Figure 3, shows the pressure volu

along with engine terminology a

Top Dead Center (TDC): Positi

furthest point away from the cra

Top because this positio

ngine Terminology

,

Because in some engines

engines(e.g: horizontally oppose

Some sources call this position

Some source call this poi

When the piston is at TD

minimum called the clea

e diagram of ideal engine cycle

follows:

on of the piston when it stops at th

kshaft.

is at the top of the engines (not

.

TDC is not at the top of the

engines, radial engines, etc,.)

ead End Dead Center (HEDC).

nt TOP Center (TC).

C, the volume in the cylinder is a

ance volume.


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Bottom Dead Center (BDC): Positi

closest to the crankshaft.

Some sources call this Crank

not always at the bottom of theBottom Center (BC).

Stroke : Distance traveled by the pist

.

Bore :It is defined as cylinder diamet

diameter is same as cylinder diamete

Swept volume/Displacement volum

travels through one stroke.

Swept volume is defined as str

Displacement can be given for

times number of cylinders).

n of the piston when it stops at the point

nd Dead Center (CEDC)because it is

engine. Some source call this point

on from one extreme position to the othe

er or piston face diameter; piston face

( minus small clearance).

: Volume displaced by the piston as it

ke times bore.

one cylinder or entire engine (one cylind


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Clearance volume : It is the m

available for the charge (air or

reaches at its outermost point (t

during compression stroke of t

Minimum volume of c

.

Compression ratio : The ratio

of the cylinder is the compressi

Typically compressionto 12 and for CI engine

nimum volume of the cylinder

ir fuel mixture) when the piston

p dead center or outer dead center

e cycle.

mbustion chamber with piston at

of total volume to clearance volum

n ratio of the engine.

ratio for SI engines varies form 8it varies from 12 to 24


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lassification of IC en ines


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- Internal Combustion Engines

1. Intake / Compression

a. inlet port opens

b. compressed fuel-air mixturerushes into the cylinder

c. piston upward movementrovides further com ression

two stroke -

2. Power / Exhaust

a. ignition

b. piston moves downwardcompressing fuel-airmixture in the crankcase

c. exhaust port opens


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Internal Combustion Engines

starting position

a. piston stdown

b. intake vac. air-fuelgets in

1. in

four stroke -

rts moving

lve opens ixture

ake

a. piston moves upb. both valves closed

c. air-fuel mixturegets compressed

2. compression


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Internal Combustion Engines four stroke -

ignition

a. air-

explodpiston

3.

uel mixture

es driving thedown

ower

a. piston moves up

b. exhaust valve opensc. exhaust leaves thecylinder

4. exhaust


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II Cycle of operation

Otto Cycle Diesel Cycle


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III Type of fuel used

1. Volatiles liquid fuels [Gasoli

2. Gaseous fuels[Compressed

furnace gas and biogas]

3. Solid fuels [Solid fuels conve

4. Viscous liquid like heavy a

Light Diesel Oils]

5. Engines using two fuels [along with air and other fuel

e, Alcohol, Kerosene]

atural Gas(CNG), LPG, Blast

rts into gaseous fuels]

d light diesel oils [Heavy and

ighly Volatile fuel is injecteds injected in combustion space]


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IV Method of Charging

I Naturally Aspirated Engines

II Supercharged Engines

V Type of IgnitionI Battery Ignition II Magneto Ignition system


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VI Type of Cooling

Air Cooled Engine Water Cooled Engine


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Cylinder Arrangements

Fi t L A l i f E i l


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First Law Analysis of Engine ycle


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Engine Terminology (Recap)

Compression ratio ( r) = VT/VC = VC + VS / VC

i P f P


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ngine Performance Parameter

Indicated Thermal Efficiency( )

Brake Thermal Efficiency( )

ith

b th

Mechanical Efficiency ( )m

Mechanical efficiency is how much of the power

gases in cylinders is actually delivered as useful po

s Indicated power is the theoreti

maximum output power of the engine. The indicated power is the total po

available from the expanding of the gases

the cylinders negating any friction, heat l

or entropy within the system.

Brake power is the power output of th

drive shaft of an engine without with o

the power loss caused by gear

transmission friction etc.

developed by the expanding of the

wer.

i P f P (C )


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Volumetric Efficiency( )v

Relative Efficiency( )rel

tan

Actual thermal efficiency

Air s dard efficiency

=

rel

Volumetric efficiency is defined as the ratio

volume flow rate into the intake system to th

which the volume is displaced by the system.

ean ec ve pressure pm

Mean Effective pressure is the average

combustion engine based on the calculated or

pressure increases.

60 1000

mp LAnKip =

60000m

ippLAnK

= b

p

s (Cont)

.

/ 2

av

a d i s pV N

m

=

f actual

rate at

pressure inside the cylinders of an internal

easured power output . It increase as manifold

60000 bpAnK

=

Area of the indicator diagra

Length of the indicator diagr

imp

i P f P t

(C t )


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Mean Piston Speed ( )pS

2pS LN=

Specific Power Output (Ps)

=

Specific Power Output (Ps) of an engine is defined as t

s

= Constantpbm pS

Specific Fuel Consumption (sfc)

Sfc = Fuel consumption per unit time

Power

s (Cont)

e power output per unit piston area.

i P f P t

(C t )


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Inlet Valve Mach Index (Z)

p

i i

Au V

C A=

Fuel-Air (F/A) or Air Fuel Ratio (A/F)

A mixture that contains just enough air for c

the mixture is called a chemically correct or sto

SI engines : 15:1CI engines : 18:1 to 80: 1 from ful

= Actual fuel-air rati

Stoichiometric fuel

s (Cont)

mplete combustion of all the fuel in

ichiometric fuel-air ratio.

load to no load

air ratio


s (Cont )


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Calorific Value (CV)

Calorific value of a fuel is the thermal energ

fuel is burned completely and the product

temperature of the combustible mixture. Ot

value and heat of combustion.

Th

s (Cont)

y released per unit quantity of the fuel when the

of combustion are cooled back to the initial

er terms used for the calorific value are heating

ank

ou

ic engines ppt lecture no 1

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