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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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ngine Performance Parameter
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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ngine Performance Parameter
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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ngine Performance Parameter
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
ngine Performance Parameter
s (Cont )
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ngine Performance Parameter
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