I c engine by Patait S.B

 Introduction
 Classification
 Working of Two stroke
 Working of Four stroke
 Power cycles
 Valve timing diagram
 IC engine combustion
 Working of simple
carburetor
 M.P.F.I. system
 Lubricant additives and
their
advantages

 A perfect gas is used as a working medium
 The transfer of heat that does not affect the temperature
of source and sink.
 The wall of piston and cylinder perfectly insulator
 The cylinder head is perfect heat conductor or perfect insulator
as requirement.
 The working fluid has a fixed mass
 The working medium does not undergoes any chemical
changethroughout the cycle
 The specific heat Cp and Cv do not vary with temperature

• In an Internal combustion engine, combustion takes place within
working fluid of the engine, thus fluid gets contaminated with
combustion products.
– Petrol engine is an example of internal combustion engine,
where the working fluid is a mixture of air and fuel .
• In an External combustion engine, working fluid gets energy using
boilers by burning fossil fuels or any other fuel, thus the working
fluid does not come in contact with combustion products.
– Steam engine is an example of external combustion engine,
where the working fluid is steam.

Internal combustion engines may be classified as :
– Spark Ignition engines.
– Compression Ignition engines.
• Spark ignition engine (SI engine): An engine in which the combustion
process in each cycle is started by use of an external spark.
• Compression ignition engine (CI engine): An engine in which the
combustion process starts when the air-fuel mixture self ignites due to
high temperature in the combustion chamber caused by high
compression.
– Spark ignition and Compression Ignition engine operate on
either a four stroke cycle or a two stroke cycle

• Four stroke cycle :It has four piston strokes over two
revolutions for each cycle.
• Two stroke cycle :It has two piston strokes over one
revolution for each cycle.
• We will be dealing with Spark Ignition engine and
Compression Ignition engine operating on a four stroke
cycle.

 Top dead center (TDC), bottom dead center (BDC), stroke,
bore, intake valve, exhaust valve, clearance volume,
displacement volume, compression ratio, and mean
effective pressure
7

T-S Diagram
P-V Diagram
Process 1-2: reversible isothermal during this air expand and heat
addition at temperature T1
Process 2-3: Air expand from temperature T2 to T3
Process 3-4: Air is compressed isothermally. heat is rejected during this
process.
Process 4-1: Air is compressed adiabatically from T4 to T1

Otto cycle
The air standard Otto Cycle is an i deal cycle that approximates
a spark- ignition internal combustion engine. It assumes that the heat
addition occurs instantaneously while the piston is at TDC.

Process 1-2: Isentropic compression
Process 2-3: Constant pressure heat addition
Process 3-4: Isentropic expansion
Process 4-1: Constant volume heat rejection

P-v diagram of an ideal dual cycle. T-s diagram of an ideal dual cycle.
Process 2-3:Constant pressure heat addition
Process 3-4: Constant volume heat addition
Process 5-5:Isentropic expansion
Process 5-1: Constant volume heat rejection

1 – 2 isentropic compression
2 – 3 heat supply
at constant pressure
3 – 4 isentropic expansion
4 – 1 heat rejection
at constant volume
1
V
2 3
4
(ideal cycle for some low speed CI engines)
p

Process 2-3: Constant pressure heat addition
Process 3-4: Isentropic expansion
Process 4-1: Constant pressure heat rejection

1 – 2 isentropic compression
2 – 3 heat supply
at constant pressure
3 – 4 isentropic expansion
4 – 1 heat rejection
at constant volume
(ideal cycle for some low speed CI engines)
p
1
V
2 3
4


44
2  1   2 
n
n
 T1n1     
P V T
P1  V2 
2  1   2 
n
n
 T1n1
     
P V T
P1  V2 
Qin  mCv T3 T2 
Qout  mCv T4 T1 






1. CYCLEOFOPERATION
Twostrokeengine
Fourstrokeengine
2. THERMODYNAMICCYCLE
Ottocycle
Dieselcycle
Dualcycle
3. METHODOFIGNITION
S.I.ENGINE
C,I.ENGINE
4.NO.OFCYLINDERS
Single
Multi
5. COOLINGSYSTEM
Aircooled
Watercooled
Oilcooled

 FUELUSED
Petrol
Diesel
Gas
SPEED
Highspeed
Lowspeed
Mediumspeed
APPLICATION
Automotiveengines
Aircraftengines
Marineapplication
Generatorsets

 ARRANGEMENTOF CYLINDERS
Vertical
Horizantal
V- engine
Radial engine
Opposed cylinder
Opposed piston

types of heat engines
external combustion
internal combustion
steam engines
turbines
Stirling engine
Otto engine
Diesel engine
Vankel engine

 BORE
 STROKE
 TDC
 BDC
 CLEARENCEVOLUME
 SWEPTVOLUME
 COMPRESSIONRATIO

Intake Valve
Valve Cover
Intake Port
Head
Coolant
Engine Block
Oil Pan
Oil Sump
Crankshaft
Camshaft
ExhaustValve
Spark Plug
ExhaustPort
Piston
Connecting Rod
RodBearings
Back
Next
Diagram

10
 Intake
 Compression
 Power
 Exhaust

11
 Intake valve opens.
 Piston moves down,
½ turn of
crankshaft.
 A vacuum is created in
the cylinder. Atmospheric pressure
the air/fuel
into the
pushes
mixture
cylinder.

12
 Valves close.
 Piston moves up, ½
turn of crankshaft.
 Air/fuel mixture is
compressed.
 Fuel starts to vaporize
and heat begins to
build.

13
 Valves remain closed.
 Spark plug fires
igniting fuel mixture.
 Piston moves
down, ½turn of
crankshaft.
 Heat is converted to
mechanical energy.

14
 Exhaust valve
opens.
 Piston move
up, crankshaft
makes ½turn.
 Exhaust gases are
pushed out
polluting the
atmosphere.

 Otto cycle
 Air – fuel mixture
suction stroke
 spark plug is needed
 C.R.=6-12
 Cheap
 Less vibration & noise
 Motor cycles, cars, light
duty vehicles
 Diesel cycle
 Only air sucked
during suction
stroke
 No spark plug
needed
 C.R.= 14-22
 High efficiency
 HeavyCostly
 More
PETROLENGINE(S.I.) DIESELENGINE(C.I.)

 Cycle - 1 rev & 2strokes
 1 power stroke per Rev.
 Ports
 Simple ,light weight ,low
cost
 More power for same
size engine
 Piston shape –crown
 Less efficiency
 E.g,mopeds, scooters
 Cycle-2rev & 4strokes
 1 Power stroke per 2 Rev
 valves
 Complicated,heavy
 ,costly
 Less power
 Flat piston
 More efficiency
 Cars, bikes,trucks,buses
FOURSTROKES

  Ignition Lag
 It is related with growth and development of a left
 propagating flame.
  Flame Propagation
 During this the sudden pressure and temperature rise.
The heat released rate is depend on turbulence intensity and
reaction rate of charge.
  After Burning
 This is instant at which the pressure is reached on the
indicator diagram. The velocity of flame decreases so
combustion rate decreases. Since the expansion stroke start
before this stage.

33
Ignition delay (ab) - fuel is injected directly into the cylinder towards the
end of the compression stroke. The liquid fuel atomizes into small
drops and penetrates into the combustion chamber. The fuel vaporizes
and mixes with the high-temperature high-pressure air.
Premixed combustion phase (bc) – combustion of the fuel which has
mixed with the air to within the flammability limits (air at high-
temperature and high- pressure) during the ignition delay period occurs
rapidly in a few crank angles.
Mixing controlled combustion phase (cd) – after premixed gas consumed,
the burning rate is controlled by the rate at which mixture becomes
available for burning. The rate of burning is controlled in this phase
primarily by the fuel-air mixing process.
Late combustion phase (de) – heat release may proceed at a lower rate
well into the expansion stroke (no additional fuel injected during this
phase).
Combustion of any unburned liquid fuel and soot is responsible for this.


34
Start of
injection
End of
injecction
-10 TC-20 10 20 30

  It is the process of clearing or sweeping out the
exhaustgases from the combustion chamber of the cylinder.
  It is necessary that cylinder should not have any
burntgases because they mixed with the fresh incoming
charge and reduce its strength.
  Power will loss if the fresh charge is diluted by
the exhaust gases.
  The scavenging is necessary only in two stroke engines
since piston does not help for clearing the burned gas
from the cylinder.

 Cross flow scavenging
 Full loop or back flow scavenging
 Uniform flow scavenging

1.Cross flow scavenging:
Thepiston crown is
designed into a
particular shape, sothat
the fresh charge moves
upwards and pushes
out the burnt gasesin
the form of crossflow.

2. Back flow or loop
scavenging: In this
method, the inlet and
outlet ports aresituated
on the sameside of the
engine cylinder. The
fresh charge , while
entering into theengine
cylinder, forms aloop
and pushes out the
burnt gases.

3.Uniflow scavenging: In
this method, the fresh
charge, while entering
from one or both side
of the engine cylinder
pushes out the gases
through the exit valve
situated on the top of
the cylinder.

  In SI engine the combustion during
the normalworking is initiated by a electric
spark.
 The spark is timed to occur at a definite
point justbefore the end of the compression
stroke.
 The ignition of the charge should not occurs
beforethe spark is introduced in the cylinder, if the
ignition start due to any other reasons when the
piston is still doing its compression stroke is called
as pre-ignition

 High compression ratio
 Overheated spark plug point
 Incandescent carbon deposit on cylinder wall.
 Overheated exhaust valve
 It may occur due to faulty timing of spark
production.

 Reduce useful work per cycle
 Increase heat losses from engine
 Reduction in the thermal efficiency
 Subjected the engine components to
excessivepressure

 It is the indication of abnormal combustion in the
engine cylinder, in normal combustion of SI engine
the spark is produce just before the end of
compression .
 In abnormal combustion after the combustion
produced, there is rise of temperature and pressure
due to the combustion of the ignited fuel which leads
to propagate the flame to the remote part of the
cylinder & the charge present in the remote part
reaches to critical temperature

 Noise
 Mechanical damage
 Increase heat transfer
 Pre-ignition
 Decrease in power out
put

© Goodheart-
Willcox Co., Inc.
Permission granted to
reproduce for educational
use only
 Ignition Timing
 Lean Air/Fuel ratio
 Fuel Octane
 Exhaust gas back pressure
 Intercooler
 Ambient heat

© Goodheart-
Willcox Co., Inc.
use only
 The two most common tricks (and easiest options),
 used by supercharger manufacturers and
 engine tuners looking to obtain maximum performance
without detonation is
1. use higher octane fuel, and
 Higher octane fuel burns more controllably and is not
 as likely to combust before the flame front.
2. retard the ignition timing.
 Retarding the ignition timing will delay the timing of the spark, which also
moves you away from your detonation threshold.

© Goodheart-
Willcox Co., Inc.
use only

• To increase the output of any engine more fuel can
be burned and make bigger explosion in every
cycle.
 One way to add power is to build a bigger engine.
> But bigger engine, which weigh more and
cost more to build and maintain are not
always better
 Another way to add power is to make a normal sized
engine more efficient.
> This can be accomplish by forcing more air
into the combustion chamber.
> More air means more fuel can be added and more
fuel means a bigger explosion and greater

 A supercharger is an air compressor used for forced
induction of an internal combustion engine.
 The greater mass flow-rate provides more oxygen to
support combustion than would be available in a
naturally aspirated engine.
 Supercharger allows more fuel to be burned and more
work to be done per cycle, increasing the power output
of the engine.
 Power for the unit can come mechanically by a belt,

 To raise the density of the air charge, before it enters
the cylinders.
 To raise engines power output for a given weight and
size of the engine. (for aircraft, marine and
automotive engines).
 To compensate for the loss of power due to altitude.
 To increase the volumetric efficiency.

 There are two main types of superchargers
defined according to the method of
compression
i. Positive displacement (ex. Twin-screw, roots)
ii. Dynamic compressors (ex. Centrifugal)
 The former deliver a fairly constant level of pressure
increase at all engine speeds (RPM), whereas the
latter deliver increasing pressure with increasing
engine speed.
 Dynamic compressors rely on accelerating the air to
high speed and then exchanging that velocity for

Centrifu
gal
Axial
Flow
Van
e
Twin-
Roo
ts

A supercharger can consume as much as 20
percent of an engine's total power
output.
Increase in pressure increases thermal load on
engine due to increase in the rate of heat release.
Detonation tendency increases in SI engine.
Reliability of engine decreases with increase in
maximum pressure in the cylinder.
Increase the strain on engine and gear train.

 A turbocharger, or turbo is a centrifugal compressor powered
by a turbine that is driven by an engine's exhaust gases.
 To improve an engine's volumetric efficiency by increasing the
intake density.
 The turbine converts the engine exhaust's potential
pressure energy and kinetic velocity
energy into rotational power, which is in turn used to drive the
compressor.

 More power compared to the same size naturally aspirated
engine.
 Better thermal efficiency over naturally aspirated engine and
super charged engine.
 Better Fuel Economy by the way of more power and torque
from the same sized
engine.
 Better volumetric efficiency.
 High speed obtained.
 Better average obtained.
 Engine weight will increase.
 If there will be improper maintenance then there will be
problem in turbo such as turbo lag.
 Engine cost will increase.

 In petrol engines, the air and fuel is mixed outside the
engine and partly evaporated mixture is supplied to the
engine.
 In S.I. engine suction created is sufficient to create air
flow and fuel injected easily evaporates. While for C.I.
engine separate injection system is used.
 The process of preparing air fuel mixture in S.I. engine
outside cylinder is called carburetion with the help of
carburetor.
 It is desirable to have complete vaporized mixture in
cylinder for proper combustion.

 The design of carburetor is difficult and complicated as the
requirement by the engine for A/F ratio vary from 1/1 to
15/1 under different operating conditions.

III.
I. It has number of moving parts which may out and
effects the performance.
II. Ice formation and freezing may be take place and may
be affect the combustion.
In multi cylinder engine A/F mixture ratio may vary in
each cylinder.
IV. Air and fuel has to pass from various path and devices
like chock, ventury, inlet/outlet pipes, bends, throttle
valve which may restrict the flow and decreases the
volumetric efficiency.
V. Backfiring may be take place in suction and exhaust
manifold.

 The desired A/F ratio is one that gives the maximum
economy . But the engines used for transportation, the
A/F ratio must change depending on whether maximum
economy or maximum power is desired and also for
different loads and speeds.
 There is limited range of A/F ratio which is 7/1 to 20/1
for S.I. engine.

 Fuel injection is a system for introducing fuel into
internal combustion engines, and into automotive
engines, in particular.
 It is always indirect, petrol being injected into the inlet
manifold or port rather than directly into combustion
chamber. This ensures that fuel is well mixed with the air
before it enters the chamber.
 On diesel engines, fuel injection is necessity, while for
petrol engines it is alternative to the carburetor or
gasoline direct injection.

 The primary difference between carburetors and fuel
injection is that fuel injection atomizes the fuel through a
small nozzle under high pressure, while a carburetor
relies on suction created by intake air, accelerated though
a ventury tube to draw the fuel into airstream.
 Basically, there are two types of fuel injection system:
Injection
System
Throttle
injection system
(single point)
Port injection
system (multi
point)

 Power output, fuel efficiency
 Emission performance
 Ability to accommodate alternative fuels
 Reliability and smooth operation
 Initial and maintenance cost
 Diagnostic capability
 Range of environmental operation
 Engine tuning

MPFI
 The purpose of this system is to
supply proper A/F mixture to each cylinder
of the engine.
 These are classified as:
 Port
Injection
Throttle
Injection

 The injector is fitted in the inlet manifold near the inlet
valve. The uniform mixture formed enters into the
cylinder.
 Every cylinder is provided with a separate injector in
multi-cylinder engine as shown in fig below.
Multi-point Flue Injection (MPFI) near Port

 In this kind of system, the petrol is sucked from the tank
by a pump and pressurized petrol at 3 bar is supplied
through a distributor to the fuel injector to a particular
cylinder.
 The relief valve shown in the fig maintains the pressure
and allows the excess petrol to return to tank.
 The pump may be drive by engine or separate motor.
 In this system, the petrol is injected continuously into the
inner port as shown in fig at a varied rate. The
distribution may be made by having a separate metering
pump for each cylinder, all are timed by the arrangement
of a series of cams on one cam shaft.

 Now-a-days electronically controlled fuel injection
system are used as it functions rapidly and responds
automatically to the change in manifold air pressure,
engine speed, crankshaft angle and many other factors.
 This system access data from various sensing devices
then adjust the A/F ratio for the best performance of the
engine.
 This system has to contain a means of supplying extra
fuel for cold starting , during warming and enriching the
mixture during acceleration.

 The system is shown in the fig, where single injector is
used like a single carburetor. The throttle valve controls
the amount of air entering in the intake manifold.
 The injector is located above the throat of the body and
injected fuel mixes with air. then the mixture passes into
the intake manifold. The fuel injected is controlled as per
the speed and load on the engine.
 The combustion chamber injection is just similar to CI-
engines.
 Mitsubishi engineers Drs. Ando and Akira were
successful to develop a gasoline direct injection(GDI)
engine in 1996.

 To understand arrangement of
conventional carburetor system with
injection systems shown in fig.
Throttle Body Injection (Single Point)

 The most widely used GDI injector is needle type, high
pressure, swirl spray unit which delivers conical spray.
 It has finite no of holes to provide uniform fuel spray
over conical circumference. This method of spray has
two important advantages:
I. Pressure energy is transformed into an axial
momentum and partial into rotational which results
in better atomization.
II. It can provide various spray geometry.

 The fuel injectors are screwed into either the inlet
manifold or the cylinder head and are angled so that the
spray of fuel is fired towards inlet valve. The injectors
are of two types, depending upon the injection system.
 The first system uses continuous injection where fuel is
squirted into the inlet port all the time the engine is
running. The injector simply act as spray nozzle to break
up the fuel into a fine spray, it does not actually control
the fuel flow.
 The other popular system is timed injection where the
fuel is delivered in manifold to coincide with the
induction stroke of the cylinder.

MECHANICA
L INJECTOR
ELECTRON
IC
INJECTOR

 We know that fuel injection reduces emission of
exhaust gases and develops maximum power with
equal power generation by each cylinder. However, the
mechanical system response is slow as well as it has
few limitation because of system inertia.
 In present modern system, computer and solenoid
operated fuel injectors are used to meter and inject
right amount of fuel at right time into cylinder.
 The computer receives signals either in form of current
or voltage from different sensors.

 The system contains different sensors as given below:
A. Inlet manifold pressure sensor: It is used to sense the
pressure of the air in the intake manifold in order to adjust
A/F ratio as per load on the engine.
B. Air flow sensor: Measures volume of air flowing through
intake manifold to adjust A/F ratio
C. Engine speed sensor: Sense the speed of the engine to
adjust A/F ratio
D. Throttle position sensor: Monitors position of throttle
valve to adjust A/F ratio for required speed and
acceleration
E. Engine temperature sensor: Senses the outlet temperature
of cooling water so that ECU adjust the A/F ratio for
mixing rich mixture

F. Knock sensor: Detects pitching noise so that the ignition
timing can be retarded to avoid knocking
G. Exhaust gas sensor: Measures O2 percentage in exhaust
gases and calculate A/F ratio for adjustment.
 The MPFI electronic system on the basis of function, is
divided into three main components as listed below:
I. Electronic control unit (ECU)
II. Fuel supply unit
III. Air induction unit

 This system is shown in figure. In this system, the
sensor monitor the inlet air temperature, outlet cooling
water temperature, the O2 in the exhaust manifold, the
throttle position, air volume entering cylinder and
engine speed send signals to ECU.

 The fuel from pump is supplied through cold start
injector with the help of cold start switch which supplies
rich A/F mixture to the air-intake chamber.
 The main injector operates only after getting signal from
ECU once engine starts.

 The fig is self explanatory. The quantity of air supplied
is controlled, in such a way that is necessary for
complete combustion.

 The MPFI electronic system is also classified as
1) D-MPFI system: The main input signal are the intake
manifold pressure, Engine speed and flow volume of
air which are sent to ECU to control the A/F ratio.
2) L-MPFI system: The main input signal are air flow
rate and engine speed to regulate fuel quantity injected.
 The both system mentioned above, sends the
information of respective sensors to ECU and then
ECU processes the information and sends commend to
fuel injector to regulate fuel injected. Then the mixture
formed enters into the engine.

I. Engine requires different A/F ratio at different operating
condition like idling, part/full load, acceleration, etc. this
system satisfy all condition and provides required A/F
ratio at different condition results in best performance.
II. There is no ventury as in carburetor so there is sooth
flow of air, hence volumetric efficiency increases.
III. Less problem of icing and vapor lock.
IV. Easy starting.
V. In multi cylinder engine same A/F ratio will be supplied
to all cylinders.

VI. As required A/F ratio supplied at different conditions,
exhaust emission will be lower and more power
bsfc results in better mileage of an
developed.
VII. Improved
automobile.

I. High initial cost
II. Major parts electronic so can be repair which increases
the cost of maintenance.
III. Skilled worker and special service equipments required
for diagnosis and maintenance.
IV. System is more complicated which require more care
and attention.

 Here is the example of automobile company using MFI
system.
 Ford first debuted their multi-port fuel injection on the
1983 1.6 liter Escorts and the 2.3-liter Mustang and
Thunderbirds. Multi-port or MFI became Ford’s
standard fuel-injection system on all V-6 and V-8
engines in 1986.

Structural difference:
 Carburetor consists of an air inlet through air filter,
after that there is chock valve and passing it air pass
through a throat in which it mix with fuel and there is
throttle valve after which mixture pass into engine.
 Construction of fuel injector consist of following
things: O-ring, filter, Electric connector, Electric coil,
Magnet, etc.
Device category:
 Carburetor is a pure mechanical device where as fuel
injector could be pure mechanical or electrical device
but most of them are electrical now.

Diagnose of problem:
 The complete electronic nature of the electric fuel injector
allows problems to be diagnosed simply by connecting the
ECU to diagnostic device or a computer where as in
carburetors a specific experience is required for
maintenance and tuning because it has to be done manually.
Fuel variation:
 Fuel injector allow the engine to perform with various
fuels, and the operation from the driver’s perspective is
smooth and fast this property is completely absent in
carburetor.

Efficiency and Emissions reducing:
 The fuel consumption can be optimized to suit the
performance of the engine in the fuel injectors, which
increasing the efficiency and reducing the emission where
as in carburetor fuel consumption cannot be optimized
because of its working phenomena.

 There are many companies providing services
of automotive parts to automobile
manufactures. But here, is the one company
having major distribution of automotive parts
of Germany.
 Bosch is the multinational company founded
on 15 nov., 1886. The founder of this
company was Robert Bosch.
 Bosch’s core products:
 Automotive components: Brakes, controls,
electronics ,fuel systems, generators, steering
system

I c engine by Patait S.B

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