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INJECTION SYSTEM IN C.I ENGINE
PROF. JIGNESH SOHA
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OBJECTIVES OF FUEL INJECTION SYSTEMS
a. Meter The Correct Amount Of Fuel As Per Engine Demand,
b. Equally Distribute This Fuel Among All Cylinders,
c. Inject This Fuel Inside The Cylinder At The CorrectTime And Rate,
d. Inject This Fuel Into The Cylinder With AProper Pattern And Atomization As
e. The Combustion Chamber Design Demands,
f. Start And End Of Injection Should BeSharp Without Dribbling Or After Injection,
g. InjectionTiming Should Vary As Per Engine Load And Speed And
h. It Should Maintain All The Above Requirements Throughout Its Operational Life Wi
Reliability.
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TO ACCOMPLISH THESE REQUIREMENTS
1) Pumping Element (To Move The Fuel From The Tank To The Cylinder),
2) Metering Element (To Measure And Supply The Fuel At Rate As Per The Engine Dem
3) Metering Control (To Adjust The Rate Of Fuel Metering Element As Per Engine Dema
4) Timing Control (To Adjust The Start And End Of The Injection Process),
5) Mixing Element (To Atomize And Distribute The Fuel Inside The Combustion Chambe
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CLASSIFICATION OF INJECTION SYSTEMS.
The injection system in diesel engines can be of two types
1. Air injection.
2. Airless injection(SOLID INJECTION).
Air Injection System : In This System, Fuel Is Forced Into The Cylinder By Means Of C
This Is Rarely Used Nowadays As It Is Bulky And Requires Multi-stage Compressors.
It Has Certain Advantages Of Producing Good Mixing Between The Air And Fuel AOf Cheaper And Higher Viscosity Fuels.
Solid Injection System : This Is Also Called Air-less Mechanical Injection. In This Sy
Injected Into The Cylinder.
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SOLID INJECTION SYSTEM OR AIR LESS INJECTION SYSTEM OR DIREC
SOLIDINJECTION
SYSTEM
MECHANICALINJECTION
COMMOM RAILDIRECT
INJECTION(CRDI)
INDIVIDUALPUMP SYSTEM
DISTRIBUTOSYSTEM
ELECTRONIINJECTION
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COMMON RAIL DIRECT INJECTION (CRDI)
Fuel from the tank is supplied to common
header calledaccumulator
A spring loaded high pressure relief valve
are maintain constant pressure in the system
Fuel sprayed into the cylinder through nozzle
whose opening & closing by needle valve
Needle valve is controlled bycam.
When cam is during dwell period, spring forces
needle valve & it will close.
Wedge is operated either manually or by
governor which control the amount of fuel.
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INDIVIDUAL PUMP SYSTEM
Fuel injection is affected by a separate fuel
pump & nozzle for each cylinder.
Fuel low pressure pump(raise the pressure
2.5 bar)
Pump are connected to camshaft C.
L is the control device to control the amount of
fuel.
Pressure requirement vary from 100bar to
300bar
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DISTRIBUTOR SYSTEM
Distribution of the fuel is done by the distributor to various nozzle.
N C ON M
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FUEL INJECTION PUMP
OBJECTIVE
1. TO DELIVER ACCURATE METERED QUANTITY OF FUEL.
2. FOR CORRECT TIMING
3. HIGH PRESSURE IN THE RANGE OF 100 BAR TO 300 BAR NEEDED DEPENDING UPON THE
TYPES OF INJECTION PUMP
1. JERK TYPE INJECTION PUMP OR BOSCH FUEL INJECTION PUMP
2. DISTRIBUTOR TYPE INJECTION PUMP.
BOSCH FUEL INJECTION PUMP
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BOSCH FUEL INJECTION PUMP
It consist cylindricalplunger closely fitted in to a barrel.
Reciprocating motion of the plunger is givenby cam.
The plunger has a rectangular vertical groove which
extended from the top to another helical groove.
Delivery valve lifted from its seat due to pressure of the
fuel.
Outlet passage is connected to the automiser.
Fuel comes through the supply port & it trapped in a barrel.
As plunger pushed up both supply & spill port are covered
by plunger.
Plunger upward causes fuel to a high pressure.
Through delivery valve fuel goes to outlet passage.
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DISTRIBUTOR TYPE FUEL PUMP
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DISTRIBUTOR TYPE FUEL PUMP
PUMP HAS ONLY A SINGLE PUMPING ELEMENT &
THE FUEL IS DISTRIBUTED TO EACH CYLINDER BY
MEANS OF A ROTOR AS SHOWN IN FIG.
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FUEL INJECTOR
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FUEL INJECTOR Main function is to atomize the fuel & distribute such
that it makes homogenous mixture of air & fuel.
Nozzle valve is lift up due to high pressure fuel entering
at the bottom of the valve. & fuel is injected inside
cylinder. As the pressure of fuel falls as the injected into the
cylinder & nozzle valve moves down to under spring
force.
INJECTION NOZZLE
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INJECTION NOZZLE
NOZZLE IS THAT PART OF AN INJECTOR THROUGH WHICH THE LIQUID FUEL IS SPRAYED
THE COMBUSTION CHAMBER.
VARIOUS TYPES OF NOZZLES ARE USED IN CI ENGINES. THESE TYPES ARE SHOWN IN IM
THE MOST COMMON TYPES ARE:
i. THE PINTAL NOZZLE
ii. THE SINGLE HOLE NOZZLE
iii. THE MULTI-HOLE NOZZLE
iv. THE PINTAUX NOZZLE
Size Of The Hole Is Around 0.2mm.
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Single point
Size Of The Hole Is Around 0.2mm.
Injection Pressure Is 10 To 12 Mpa.
Advantages
Very High Injection Pressure.
Disadvantages
Tendency To Dribble & Facilitating Poor
Mixture.
MULTI HOLE
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MULTI HOLE
NUMBERS OF HOLE AROUND 4 TO 18 & SIZE
FROM 35 TO 200 MICROMETER.
MIXING THE FUEL & AIR PROPERLY..
DISADVANTAGES
IT REQUIRED HIGH INJECTION PRESSURE UP TO
180 TO 200 BAR.
CLOGGING OF THE HOLE OWING TO VERY
SMALLER IN SIZE.
PINTLE NOZZLE
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Spray Characteristics Can Be Varied Over A Fairly Wide
Range.
By Altering The Section Of The Pin Along Its Length, The Type
Of The Spray Can Be Varied So As To Give Different EffectsDuring The Injection Period.
PINTLE NOZZLE
PINTAUX NOZZLE
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PINTAUX NOZZLE
AUXILIARY HOLE DRILLED IN THE NOZZLE BODY.
THIS ALLOWS A SMALL AMOUNT OF FUEL INJECTION IN THE
UPSTREAM DIRECTION AT TIME SLIGHTLY IN ADVANCE OF THE
MAIN DOWN STREAM INJECTION.
AT LOW SPEED, THE NEEDLE VALVE DOES NOT LIFT , RESULTING IN
VERY GOOD STARTING PERFORMANCE.