injection in c.i engine

8/12/2019 Injection in c.i engine

1/22

INJECTION SYSTEM IN C.I ENGINE

PROF. JIGNESH SOHA


2/22

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.


3/22

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


4/22

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.


5/22

SOLID INJECTION SYSTEM OR AIR LESS INJECTION SYSTEM OR DIREC

SOLIDINJECTION

SYSTEM

MECHANICALINJECTION

COMMOM RAILDIRECT

INJECTION(CRDI)

INDIVIDUALPUMP SYSTEM

DISTRIBUTOSYSTEM

ELECTRONIINJECTION


6/22

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.


7/22


8/22

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


9/22

DISTRIBUTOR SYSTEM

Distribution of the fuel is done by the distributor to various nozzle.

N C ON M


10/22

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


11/22

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.


12/22


13/22


14/22

DISTRIBUTOR TYPE FUEL PUMP


15/22

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.


16/22

FUEL INJECTOR


17/22

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


18/22

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.


19/22

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


20/22

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


21/22

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


22/22

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.

injection in c.i engine

Documents