Download - Governing,ignition system,fire order
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GOVER
PROF. JIGNE
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GOVERNING OF I.C ENGINES
1. Qualitative governing
2. Quantitative governing
3. Hit & miss governing
QUALITATIVE GOVERNING
The amount of air taken inside is constant., but the fuel supply varies according to
Quality of air-fuel mixture changes as per the amount of the fuel supply.
So method is known as quality method.
C.I engine works on qualitative governing.
QUANTITY GOVERNING METHOD
Another name is throttle governing.
Used in petrol & gas engine.
This method varies the fuel & air mixture supplied to cylinder.
Quality of mixture remains same.
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HIT & MISS GOVERNING
In this type of governingthe fuel supply is stopped
for one or more cycle when the engine speed
increases.
By stopping the fuel supply CRANKSHAFT SPEED
BECOME NORMAL. LEVER CARRIES STRIKER which STRIKES THE STEEL
DIEat the normal speed due to rotation of cam. So
the steel die strikes the plunger of fuel pump or gas
valve. This cycle is known as HITTING.
During This Cycle Fuel Is Supplied To The Engine By
Fuel Pump Or By The Gas Valve In Case Of GasEngines.
When Engine Speed Increases, The Lever With Drop
Rod Moves In Upward Direction Due To The Upward
Movement Of The Sleeve.
So The Striker Will Not Strike The Plunger Through
The Steel Die & No Fuel Will Be Supplied During This
Cycle. This cycle is known as MISSING CYCLE.
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BATTERY IGNITION
Battery
It is charged by generator or alternator when engine
is in running.
Required electrical energy for functioning the
system is provided by battery of 6 to 12 volts.
lead acid battery & alkaline batteries are suitable for
i.c. engine.
Ignition switch
To turn on off the power supply from battery to
ignition system.Ignition coil
Primary winding 100 to 200 turns.
Secondary winding 10,000 turns.
Ballast resistor is connected in series with primary
winding to regulate the primary current.
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Cam & contact breaker
Through the cam shaft on which the cam is used to
brake & make contact between contact point.
Breaker point are closed electric current flows.
Condenser (capacitor) Condenser remains in parallel with contact breaker.
If condenser is not provided, the current would be
re-established which would results into heavy arc
across the contact breaker points & energy of
ignition coil will be consumed by the arc which may
be burn the contact breaker point.
Distributor
Arm is mounted on a cam shaft & it is rotated at the
half speed of the crank shaft in case of 4 ST engine.
Function is to distribute the current which comes
from ignition coil to individual spark plug according
to firing order.
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Ignition switch is on & primary circuit is closed by contact
breaker & magnetise the core of the coil & E.M.F. is
produced in secondary circuit.
Condenser is connected across contact breaker in primary
circuit which helps to collapse the field very rapidly byabsorbing part of energy.
Which is thrown back to primary winding & producing
very high voltage (10000v to 20000v ) in secondary .
When contact breaker is open & closed & every time high
voltage generated which is distributed by distributor.
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MAGNETO IGNITION SYSTEM
Magnetos Were Used On The Small Engine's
Ancestor, The Stationary "Hit And Miss"
Engine Which Was Used In The Early
Twentieth Century. Motor Cycle, Scooter.
Magneto Ignition System Has Its Own CurrentGenerating Device, Therefore Battery Is Not
Required.
Magneto Rotates Voltage Is Generated In The
Primary Circuit.
As The Cam Shaft Rotates, The Cam Opens The
Contact Breaker & Interrupts The Flow Of
Current In A Primary.
This Cause The Decay In The Magnetic Field
Lines & Cut The Lines Of Magnetic Field In The
Secondary, & High Voltage Is Generated In The
Secondary.
L C ONIC IGNI ION SYS
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ELECTRONIC IGNITION SYSTEM
Now a days mechanical operated system are changing to electronically operated system
maintenance is low.
Limitations of battery & magneto ignition system
1. Excessive wear at contact breaker
2. If the gap between contact breaker points changes , it will affect the current generation.
3. Interruption of carbon particles between the contact point will affect the engine performa
ELECTRONIC IGNITION SYSTEM
1. Transistorised coil ignition system
2. High voltage capacitive discharge ignition system
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TRANSISTORISED COIL IGNITION SYSTEM
In almost modern automobile, the conventional battery
system is replaced by Transistorised coil ignition system.
This system provided handling the increasing voltage
required for high performance of the engines, longer
sparkplug life, reduced wear, maintanace of ignitionsystem & high reliable.
Working
Contact points are connected to the base of transistor
which is further connected to primary circuit.
Contact point is reduced to approximate 1/10th
of theoriginal value of conventional system.
Emitter of the transistor is connected to ignition coil
through ballast resistor & collector to battery.
Base circuit current being much smaller as compared to
primary current
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HIGH VOLTAGE CAPACITIVE DISCHARGE IGNITION SYS
CAPACITOR Discharge Ignition System (CDI)
Dc To Dc Convertor Is Used To Conver 12v Of
Battery To 500v.
Condenser Is Charged To This Output Voltage
Of The Converter Through The Charging
Resistance.
Resistance Is So Designed That It Controls
The Required Current In The Silicon
Controlled Rectifier(SCR).
The Condenser Is Discharged When The SCR
Triggering Device Sends The Pulse &
Producing High Voltage In Secondary Circuit.
SPARK PLUG
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SPARK PLUG
It Consist Two Electrodes With A Proper Gap About
1mm.
Electrodes Are Subjected To High Corrosion &
Erosion So It Is Made From High Nickel Alloy.
Tip Of The Electrode Are Subjected To Very High
Temperature In Order Of 2000-2400 C.
Depending Upon The Temp. Of Tip The Spark Plug
Are Classified
1. Hot Spark Plug
2. Cold Spark Plug
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CENTRIFUGAL
SPARK
ADVANCE
MECHANISM
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CENTRIFUGALSPARKADVANCEMECHANISM
It Consist Of Spring Loaded Weights Mounted
On A Platform & Connected To The Contact
Breaker Cam.
Platform Gets Rotating Motion From Cam Shaft
As It Is Connected With Cam Shaft Of Engine.
Fly Weights Are Connect With Platform Only By
Pivot.
Speed Increases Fly Weight To Move
Outward Which Alters The Ignition Timing As
Per Requirement.
VACUUM ADVANCE MECHANISM
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VACUUM ADVANCE MECHANISM
Intensity Of Vacuum At Ventury Tube Is Vary
With The Position Of Throttle.
In Idling Position , There Is No Vacuum
Advance.
As Soon As The Throttle Valve Open, It SwingsThe Past Opening Of Vacuum Passage.
This Cause Diaphragm To Move Against
Spring.
Linkages To The Breaker Plate Than Rotate
The Breaker Plate.
This Movement Create A Contact Between
Contact Point. Due To Movement Of Contact Point , Cam Is
Also Displaced .
Supply Spark At The Spark Plug Earlier In The
Compression Stroke.
FIRING ORDER FOR I C ENGINES
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FIRING ORDER FOR I.C ENGINES.
The Main Factor For Deciding The Order Of Firing, The Engine Cylinder Are Balancing Of
Reduce Vibration, Engine Cooling & The Development Of Back Pressure.
If The Firing Order Is Kept 1-2-3-4 The Exhaust Of The Cylinder 2 Will Overlap With The Exha
It Would Be Need Size Of Exhaust Pipe Bigger In Size Otherwise The Back Pressure On Th
Increase & Reducing Net Output.
Firing Order Is 1-3-4-2 Or 1-2-4-3.
1-3-4-2 Is Common Used.
For Six Cylinder 1-5-3-6-2-4, 1-5-4-6-2-3, 1-2-4-6-5-3, 1-2-3-6-5-4
1-5-3-6-2-4 Is Common Used.
INTAKE & EXHAUST SYSTEM
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INTAKE & EXHAUST SYSTEM
In S.I engine PETROL + AIR
In C.I engine only AIR
The size, shape & orientation of intake manifold is
designed such that there is a smooth flow of mixture or
air.
It will improve volumetric efficiency & power output.
INTAKE & EXHAUST SYSTEM FOR S.I ENGINE
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INTAKE & EXHAUST SYSTEM FOR S.I ENGINE
AIR + fuel mixture from carburetor.
Partially evaporated fuel & air with high
velocity passes through the intake manifold
& than reach to suction valve of cylinder.
Sometimes Liquid May Be Condenseon thesurface of intake manifold &reduces their
heat transfer.
So for better vaporization of fuel intake
manifold is heated.
it provided byexhaust gases& this purpose
mostly intake & exhaust manifold hascommon wall.
Overheating of the intake manifold will
reduces volumetric efficiency & power
output.
Inner surface of intake manifold kept
smooth so that friction during flow reduces.
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In Multi Cylinder Engine The Design Of The
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y g g
Intake Manifold Become Very Important In
Order To Reduce Inertia Effect & To Make
Distribution Of ChargeTo All Cylinder.
Parameters should be consider for designing
1. Inlet surface should be smooth so that
pressure losses are minimum.
2. Air-fuel mixture should be distribute
uniformly.
3. For max. vaporization of fuel, intake
manifold should be heated by exhaust gases.
4. Condensation of fuel should not take place
during the flow.
Exhaust Gases Are Useless.
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The Passage Or Pipe Through Which Exhaust
Gases Come Out Is Known As Exhaust
Manifold.
Main Components
1. Exhaust Manifold
2. Muffler (Silencer)
3. Tail Pipe Muffler It Reduces The Noise Level Of
Exhaust System.
In Modern Vehicle Gas Converter Is Also
Attached Which ConvertsHarmful Gases To
HarmlessExhaust Gases.
Parameter considered for designing
1. Passage should be smooth & withminimum obstruction to reduce the back
pressure.
2. Proper design of muffler.
3. Gases should quickly discharge.
4. For multi cylinder, more braches to avoid
overlapping.
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SCAVENGING SYSTEM
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SCAVENGING SYSTEM
The compressed charge passes through transfer
port into the engine cylinder flushing the
products of combustion. This process is known as
scavenging process.
Based on direction of flow of fresh charge &exhaust gases, scavenging methods
1. Cross scavenging
2. Loop or reverse scavenging
a. Full loop or MAN scavenging
b. Tangential loop
c. Curtis scavenging
3. Uniflow scavenging
CROSS SCAVENGING
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CROSS SCAVENGING
In cross scavenging the incoming air is directed
upwards, pushing the exhaust gases before it. The exhaust gases then travel down and out of
the exhaust ports. Figure above illustrates the
process.
Used for low capacity 2 stroke engine.
Inlet & exhaust port are replaced opposite to eachother.
Deflector is provided on piston top.
LOOP SCAVENGING
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LOOP SCAVENGING
In this method flow of fresh charge makes a loop
for better removal of exhaust.
Incoming charge is directed in such a way that
both charge loss & mixing are minimized.
In loop scavenging the incoming air passes over
the piston crown then rises towards the cylinder
head.
The exhaust gases are forced before the air
passing down and out of exhaust ports located
just above the inlet ports.
UNIFLOW SCAVENGING
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UNIFLOW SCAVENGING
With uniflow scavenging the incoming air enters at
the lower end of the cylinder and leaves at the top.
The outlet at the top of the cylinder may be ports or
a large valve.
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Each Of The Systems Has Various Advantages And Disadvantages.
Cross Scavenging Requires The Fitting Of A Piston Skirt To Prevent Air Or Exhaust Gas Esca
At The Top Of The Stroke.
Loop Scavenge Arrangements Have Low Temperature Air And High Temperature Exhaus
Adjacent Ports, Causing Temperature Differential Problems For The Liner Material.
Uniflow Is The Most Efficient Scavenging System But Requires Either An Opposed Pisto
Exhaust Valve In The Cylinder Head.
All Three Systems Have The Ports Angled To Swirl The Incoming Air And Direct It In The App
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CRANK CASE SCAVENGING
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CRANK CASE SCAVENGING
ROOT BLOWER
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ROOT BLOWER
CENTRIFUGAL BLOWER
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CENTRIFUGAL BLOWER
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PISTON TYPE BLOWER
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TH NK YOU