components of fuel injection system-1

7/30/2019 Components of Fuel Injection System-1

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Fabrication and working model of fuel injection pump 21

Department of Mechanical Engineering, AWH Engineering College

CHAPTER 1

INTRODUCTION

This project is about single cylinder fuel injection system in diesel engine. The fuel

injection system of diesel engine consists of fuel filters, air cleaners; fuel feed pump, fuel

injection pump ,fuel injector, and fuel tank. The main difference between a diesel injection

system and a petrol injection system is a fuel injection pump is used in diesel system,

Instead of a carburetor in a petrol system, and all other components are same. Fuel supply

system in a diesel engine has to perform certain functions. They are given below:

Filter the fuel. Meter or measure the correct quantity of fuel to be injected. Control the rate of fuel injection. Atomize or break up the fuel to fine particles. Properly distribute the fuel in the combustion chamber. The functions of the fuel injection system is to inject proper quantity of fuel in to

the engine cylinder at the correct time and at a pre determined speed. The fuel

injection system may be broadly classified in to solid injection system and air

injection system .In solid injection system only liquid fuel is injected where as in

air injection system liquid fuel is injected along with the compressed airThe air

injection system is less reliable , less efficient, and requires an air compressor for

supplying air at high pressure, due to which reasons it has become obsolete .Thus

the solid injection system is most commonly used. The functional requirements of

an injection systems are;

Introduction of fuel into combustion chamber should take place with in a preciselydefined period of time.

The metering of the amount of fuel injected per cycle should be done veryaccurately

The quantities of fuel meter should vary to meet the changing load and speedrequirements

The injected rate should be such that it results in desired heat release pattern. The injected fuel must be broken into very fine droplets. The pattern of spray should be such as to ensure rapid mixing of fuel and air.


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The beginning and end of the injection should be sharp. The timing of injection, if desired should change as per the requirments of load and

speed.

The distribution of the metered fuel, in the case of multi cylinders engines, shouldbe uniform among various cylinders.

Besides above requirments, the weight and the size of the injection system must beminimum.

It should be cheaper to manufacture and least expensive.


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CHAPTER 2

COMPONENTS OF FUEL INJECTION SYSTEMThe main components of fuel injection systems are

1. Fuel tank

2. Fuel feed pump

3. Filter

4. Injection pump

5. Injector

During the operation, the fuel from the tank enters the fuel feed pump .In feed pump, the

pressure of fuel is raised slightly. There the fuel is drawn in to the filter where all the dust

particles are removed. From the filter, the fuel enters in to the injection pump where the

pressure of air in the cylinder at the end of compression. At this high pressure fuel is

sprayed in to the engine cylinder by means of fuel injector. Any spill over fuel in the

injector is returned to the filter.

Fig2.1: Out Sketch of FIS


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2.1 DIESEL FUEL FEED PUMP

The purpose of the diesel fuel feed pump is to transfer the fuel from the tank to the fuel

injection pump. Generally diesel fuel feed pump are used in engines. They are

1. Single acting fuel feed pump

2. Double acting fuel feed pump

1. Single acting fuel feed pump

In this single acting fuel feed pump consists of a barrel, plunger return spring, roller

tappet, spindle, suction and delivery valves. The plunger is driven by cam provided on the

cam shaft of the fuel injection pump through roller tappet.

2. Double acting fuel feed pump

The double acting fuel feed pump set up has four valves. Two suction valves and two

delivery valves.

Fig.2.2: Fuel Feed Pump

2.2 DIESEL FUEL INJECTION PUMP

The purpose of the diesel fuel injection pump is to supply the correct quantity of

fuel to the injection nozzle at required pressure. Generally two type of FIP is used. They

are

1. Jerk type fuel injection pump

2. Distributor type fuel injection pump


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2.3 DIESEL FILTERS

Fuel filters are used in diesel engines to prevent the entry of dust particles,

abrasives, water droplets etc. These impurities must be prevented for the following

reasons.

1. Dust particles may affect the operation of fuel pump

2. Due to the above reason, engine performance may be reduced.

3. Water droplet may combine with the sulphur forms sulphuric acid. It may cause

corrosion of moving parts.

Fuel filters for diesel engines:

Generally two types of fuel filters are used in diesel engines. They are

1. Primary filter or pre filter.

2. Secondary filter or micro filter.

2.3.1. Primary filter.

Fig 2.3 shows the sedimentation type primary filter. It consists of a conical

diffuser, sedimentation chamber and drain plug. Due to the suction created by the fuel feed

pump, the fuel from the tank flows around the conical diffuser and moves downward to

the sedimentation chamber.

The impurities such as water and solid particles having large size above 40 micro

metre are settle down at the bottom of the sedimentation chamber. The filtered fuel moves

up and passes in to the fuel feed pump through the outlet The impurities are drained out

through a drain plug periodically. The primary filter is located between the fuel tank and

fuel feed pump.


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Fig.2.3:Primary Filter

2.3.2 Secondary filter:

Fig.2.4:Secondary Filter

Fig2.4 shows the generally used secondary filter. It may filter out very minute

particles up to 3 micro mater and water content in the fuel. In this type, the filtering

element is made of cotton. The fuel injection timing in this type of pump is controlled by

rotating the internal cam ring. As the engine speed increases the fuel feed pump delivery

pressure increases. This increase in the pump pressure is utilized to move the cam in an

advance direction with the increase of engine speed.

2.4 FUEL INJECTOR

A fuel injector is a device which atomizes the fuel from fuel feed pump and injects

it in to the engine cylinder in the form of fine sprays.

Fig.2.5: Fuel Injector


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CHAPTER 3

WORKING OF COMPONENTS

3.1 FUEL FEED PUMP

3.1.1. Single acting fuel feed pump

In this single acting fuel feed pump consists of a barrel, plunger return spring,

roller tappet, spindle, suction and delivery valves. The plunger is driven by cam provided

on the cam shaft of the fuel injection pump through roller tappet.

The plunger along with the spindle moves up and down through the action of

spring. The suction and delivery valves are located on their respective side. They are one

way valve. When the single acting pump cam shaft is in such a position that the feed pump

cam follows lies against the back of its cam lobe, the pump plunger is forced by the spring

towards cam shaft creating a low pressure area in the plunger spring chamber. Because of

this low pressure, suction of the fuel takes place inside the chamber as shown in fig3.1.

Then as the cam lobe drives the plunger against its spring the fuel is forced by the plunger

through the outlet valve fig3.1. At this position the spring is in compressed position. Some

amount of fuel is also entered behind the plunger. The compressed spring pushes the

plunger back towards the cam and the fuel behind the plunger is delivered in to the fuel

line leading to the filters and injection pump fig3.1. This completes the cycle. The plunger

continues to reciprocate and the intake and delivery of fuel takes place continuously as per

the speed requirements of the engine. Thus in one cycle of piston one suction and one

delivery takes place. Hence its name is single acting fuel feed pump.

Fig.3.1:Single Acting Fuel Feed Pump


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3.1.2. Double acting fuel feed pump.

The double acting fuel feed pump set up has four valves. Two suction valves and

two delivery valves. Due to the action of the cam when the piston is pushed downwards

the fuel already present in the pressure chamber is delivered through the delivery valve d1

and simultaneously the fuel enters the other side if the chamber through the suction valves

s2. In this position suction valve s1 and delivery valve d2 are in closed position

This constitute one suction stroke and one delivery stroke.

Now due to the spring action the piston is pushed upward. During this action the

fuel which entered through s2 valve is delivered through d2 valve and simultaneously.

Due to the suction created in the other part of the chamber suction occurs through s1

valve. In this position the valve s1 and d1 are in closed position.

This constitute the second suction and second delivery strokes. In this way in one

complete rotation of the cam shaft two suction and two delivery process takes place. This

gives the name of the pump as double acting fuel feed pump.

Fig3.2:Double Acting Fuel Feed Pump


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3.2 DIESEL FUEL INJECTION PUMP

3.2.1. Jerk type fuel injection pump

The fuel injection pump serves the supply of metered quantity of fuel in to the

engine cylinder. The principle of fuel injection pump is shown in fig3.3.It comprises

plunger reciprocating in a barrel is a cylindrical one with two diametrically opposite Ports,

one is inlet port and other is spill port. Inlet port serves to fill the barrel space above the

plunger with fuel.

Fig.3.3: Jerk Type Fuel Injection Pump

The upper portion of plunger is provided with a vertical groove. Fuel injection pump is

connected to fuel injector through delivery valve which opens under fuel pressure against

the spring action high. The plunger is turned by means of control sleeve which is driven by

rack and teethed segment. The operation of an injection pump as the plunger makes a

stroke has been shown in fig3.4


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Fig.3.4:Operation Of Flip As Plunger Makes Stroke

Figure A

When the plunger is at the bottom of its stroke, the inlet port and the spill port are

uncovered; the fuel from a low pressure pump after filtration is forced in to the barrel.

Figure B

As the plunger moves up it closes the inlet port and spill port of the barrel. On

further movement of plunger the fuel above it is compressed and its pressure increase

causing delivery valve to open and allow the fuel to enter in to the fuel injector at high

pressure.

Figure C

The plunger rises up still further, and at a certain moment the spill port is

connected to the edge of helical groove. As soon as spill port uncovers the fuel passes

through the vertical groove and annular helical groove to the spill port, thus suddenly

reduces the pressure of the fuel above plunger .As a result, the delivery valve is closed by

the spring action. The quantity of fuel delivered is controlled by the turning of the plunger.

Figure D

The plunger has been rotated in the shut off position. The slot connecting the rod

of the plunger with the recess is in line with the port. No fuel can be trapped and injected

in this position.


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Figure E

The plunger has been rotated in the idling position. The narrow port of the plunger

formed by the helix will cover the port for only a short part of the stroke. This position

permits only a small amount of fuel to be injected stroke.

Figure F

The plunger has been rotated in to the full load position. The wide part for the

plunger formed by the helix covers the port for longer part for the stroke. A large amount

fuel to be injected per stroke is permitted in this position.

3.2.2. Distributor fuel injection pump

The line diagram of distributor type fuel injection pump as shown in fig3.5

The feed pumps take the diesel from fuel tank. After filtering it feeds it to the transfer

pump. From the transfer pump diesel is pumped at a higher pressure to the metering valve

where the quantity of fuel going to the distributor is metered and controlled with the help

of governor.

From here, the diesel is sent to the distributor body through inlet port. From here it

finds its way to the center of the distributor and to the center of two plungers. These two

plungers are guided by cam ring and get pressed together. During this time this diesel oil

which have found its way between these gets pressed and pushed to the outlet pipe at

distributor which register with an opening in the housing for onwards feeding to respective

injectors. It goes on feeding diesel oil under pressure to all the injector pipes which re

arranged all its housing periphery.

The principle of working of a distributor type of fuel injection pump has been

illustrated by means of fig3.6 shown.


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Fig.3.5: Line Diagram Of Distributor Type Fuel Injection Pump

The rotor has a central longitudinal passage and a set of radial holes each equal to

the number of engine cylinders for in fig shown. Similar the outer sleeves has a set equal

number of holes At a different level B-B. Besides there is a metering port in the sleeve for

the fuel intake level A-A and a distribution port in the rotor level B-B. This distributionport is connected to the central passage in the rotor. Each of the delivery ports is connected

to the high pressure delivery lines leading to the injectors on the engine cylinders.

The lower end of the central passage in the rotor opens in to a chamber in which

two opposed pumping plungers are housed. As the rotor rotates a stationary ring with the

internal cams operates the plungers through rollers and shoes are placed in slots in to the

rotor base. The number of lobes on the cam ring is equal to the number of engine cylinders

and these are evenly spaced around the ring.

As the pump plungers move away from each other the fuel is drawn in to the

central rotor passage from the inlet port through suction ports. The fuel thus charged is

delivered to each cylinder in turn high pressure when the distribution ports coincide with

the delivery port for any cylinder.

The metering valve controlled by the governor restricts the amount of fuel entering

the rotor. Pressing the accelerator pedal increases the area of the metering port allowing

more fuel to enter rotor. There by increasing the engine speed. The maximum amount of

fuel intake to the pump is controlled by adjusting the outward travel of the pump plungers.


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Fig.3.6: Principle Of Distributor Type FIP

Each cam on the stationary ring has usually two peaks. When the roller reached

first peak which is higher, fuel injection stops. The second peak on the cam prevents the

pipeline pressure from collapsing completely for a time long enough for the distribution

port to be cut off from the delivery port.

The fuel injection timing in this type of pump is controlled by rotating the internal

cam ring. As the engine speed increases the fuel feed pump delivery pressure increases.

This increase in the pump pressure is utilized to move the cam in an advance direction

with the increase of engine speed.

3.3 FUEL INJECTOR

3.3.1Constructional Details

It consists of a nozzle, nozzle body, spindle and pressure adjusting screw. The

injector fitted with a nozzle is screwed in to the cylinder head. The nozzle valve is seated

on its seat by the force of spring. A fuel passage is cut in the body of the injector.

3.3.2Working

The high pressure fuel from the injection pump passes in to the pressure chamber

of the nozzle through fuel passage. Due to the high pressure of the fuel, the nozzle valve is

lifted on its seat against the spring force. Hence, the fuel is injected in to the combustion

chamber in the form of fine spray.


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When the fuel pressure falls, the nozzle valve is brought to its seat by the spring

force .A small quantity of fuel which leaks through the plunger provides necessary

lubrication and returned to the fuel tank through leak off passage.

Fig3.7: Fuel Injector

3.3.3Injector Nozzles

The function of the fuel injection nozzle is to inject the fuel delivcred by the pump

in to the combustion chamber and at the same time to assist in atomizing the fuel.

In diesel engines there are two type of nozzle are used.

1. Open type nozzle

2. Closed type nozzle

1. Open type nozzle

In the design of open type nozzle, the shut off device is not placed between

delivery pipe and the nozzle. Now a day open type nozzles are not used commonly.

2. Closed type nozzle

In the design of closed type nozzle a spring delivery valve is placed between the

delivery pipe and the nozzles. After each injection of fuel in to the combustion chamber,

the nozzle is closed with a spring loaded needle valve. This type of nozzle is mostly used

now a day.


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The different types of closed type nozzles are used in diesel engines

1. Single hole nozzle

2. Multi hole nozzle

3. pintle hole nozzle

4. Pintaux nozzle

1. Single hole nozzle

Fig 3.9 shows the arrangement of single hole nozzle. This type of nozzle contains a

single hole at the end of the nozzle. The fuel is passed through this hole in to the

combustion chamber. It is closed at the inner end by the nozzle valve. It may be either flat

end type or conical end type. In flat end type the hole is drilled at the center of the nozzle

axis. In the conical type the hole is drilled at an angle of 5-15 to he nozzle axis. It is used

in engines having turbulent combustion chamber.

Demerits of Single Hole Nozzle

1. It requires high pressure.

2. As the hole is very small it is subjected to clogging.

3. It has a tendency to fall in drops.

4. It requires more maintenance and operating cost.

Fig.3.8: Type Of Nozzle


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3.3.4 Injection rate characteristics

It is always desirable to supply less quantity of fuel to avoid the knocking in the

engine. The characteristics of the three nozzles are shown in fig 3.9. It is obvious from fig

that the pintle gives desired characteristics is smaller at the beginning compared with the

multiple nozzles. The characteristics of pintaux nozzle is totally different because of fuel

supply through auxiliary and main orifices

Fig.3.9: Injection Rate Characteristics


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Chapter 4

FABRICATION OF DISEL FUEL INJECTION PUMP

1. Suitable for single cylinder diesel engine was selected2. The FIP and the injector were cleaned thoroughly using diesel and air3. Then the working model was made as shown in figure4. A manually operated handled was attached to the cam shaft in order to

rotate the shaft which in turn will actuate the plunger unit

5. The injection system was then fixed on a stand made with ankle.6.Now the injection system is ready to pump and inject the diesel

Fig.4.1: Fabricated Model Of Fuel Injection Pump


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CHAPTER 5

SPECIFICATIONS OF FABRICATED WORKING MODEL

1. Fuel tank: A plastic mug

Specifications

Diameter- 11 cm

Height- 15 cm

Hole- 1 cm

2. Fuel injection pump: Mitsubishi

SpecificationsMaterial Cast iron

3. Fuel injector:

Specification

Material Cast iron

Hole diameter .025cm

Length 6.8 cm

4. Welded standSpecification

Length: 48.9cm

Breadth: 22.9cm

Height: 27.3cm


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CHAPTER 6

CALIBRATION

Calibration of the pump should be carried out after the phase angle test. This

consists of adjusting each element to deliver an equal quantity of fuel to the cylinders. The

quantity delivered per stroke depends upon the engine manufacturers requirement. As the

elements of the fuel pump deliver the fuel at various speeds and for different control rod

position .Fuel injection pump calibrated is as under.

1. Mount and couple the injection pump with the pump calibrating machine

2. Set the control rod to the maid position or say at 5mm rack position.

3. Make all the connections of fuel pipes at inlet and outlet of pump elements ensuring

them leak proof.

4. Operating the machine and run the pump at 600 rpm and then bleed the system by

opening the air vent lock.

5. The trip plate is arranged in its position. Allow the fuel to enter the glass tubes at 600

rpm and for 200 strokes. Then take the readings of fuel delivered in to the glass tubes.

6. Compare these readings with the manufacturers chart values for the 5mm rack position.

7. If there are variations in these readings then adjust the pump elements to bring the

readings as close as possible to the given chart.

8. Repeat the experiment at other speed.


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Chapter 7

CALIBRATED DATA OF FABRICATED MODEL

For the calibration of the fabricated model, the following steps are done.

1. The cam axis is rotated N number of time.2. Time for N rotation is noted.3. The quantity of fuel injected is calculated using a measuring jar.4. The procedure is repeated for a no of time .5. The mean value is calculated.

Table 7.1:Calibrated Datas Of Fabricated Model

Fig.7.1:Graph of Calibration


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Chapter 8

DESIGN OF NOZZLE SIZE

The quantity of oil injected per cycle depends upon the load of the engine when the

engine is running at constant speed. The velocity of fuel for good atomization is of the

order 400m per sec. The velocity of the fuel passing through the orifice of the nozzle is

given by

Vf= 2(P

i-P

a)

f

Where Pi and Pa are the oil pressure at the time of injection and P a is the pressure

of air inside the cylinder at the time of fuel injection.(N/m2) and f is the density of fuel

injected.


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CHAPTER 9

ADVANCEMENT IN THE FUEL INJECTION SYSTEM

9.1 COMMON RAIL DIESEL INJECTION

In normal injection system doping occurs and engine noise will be more. Pressure

maintained is not uniform and correct timing of injection is not maintained. This result in

decreased engine performance and fuel efficiency and emission will be more. To avoid the

above problems, the injection timing and pressure should be maintained constantly. This is

done by common rail direct injection.

Common rail means injecting the fuel with constant pressure through anaccumulation tank. CRDI system is an electronic system with more sensors which controls

the pressure and injection timing.

Components of CRDI

The main components of CRDI system are

1. High pressure fuel feed pump.

2. Common rail.

3. Pressure regulator.

4. Electronic injector.

5. Electronic control module.

6. Group of sensors.

Fig.9.1:Common Rail Diesel Injection


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9.2 INDIVIDUAL PUMP AND NOZZLE SYSTEM

This differs from constantpressure injection both in design and operation of the

pump and fuel injector. Each injector has a separate pump and the injector contains a

spring loaded hydraulically operated automatic plunger valve. No separate mechanism is

required to operate it.

In this system, separate pumps, each (depending upon the number of cylinder)

driven individually or a single pump having 4 plungers in a common block may be used.

In this case, the single pump is driven by the crank shaft through single cam shaft having

individual cam for each cylinder.

The arrangement of the individual pump system is shown in fig 9.2 with all pumpsin one block, 4 plungers in one barrel and a common cam shaft.

Fig.9.2:Individual Pump and Nozzle System


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CHAPTER 10

CONCLUSION

A detailed study ofFUEL INJECTION PUMP for single cylinder diesel engine

was carried out in this mini project. And the working model also has been made with

function of FIP without dismantling. The quantitative calibration of fabricated model

using single jet nozzle has been made in this project. By this project ,we can study the

working principle and calibration ofFUEL INJECTION PUMP.


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Department of Mechanical Engineering AWH Engineering College

REFFERENCE

1. Kripal Singh: Automobile engineering vol-2-second edition,2. K.K Jain &R B Asthana: Automobile Engineering-first edition3. R.B Gupta : Automobile Engineering sathya Prakashan Publication

components of fuel injection system-1

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