Types of fuel feed system - PowerPoint Presentation

Slide1

Types of fuel feed system

Gravity system

Pressure system

Vaccum system

Pump system

Fuel injection systemSlide2

Types of fuel pumps

Mechanical fuel pump

Electrical fuel pumpSlide3

According to the arrangement of float chamber:

Eccentric and

Concentric

According to the number of units

SingleDual andFour-barrelAccording to the type of metering systemAir-bleed jet and Metering rod typeAccording to the type of power systemManually operated and Vacuum controlled

Types of CarburettorSlide4

According to the type of venturi

- Plain venturi, - Double venturi,

- Vane venturi, - Nozzle-bar venturi and

- Triple venturi

Depending upon the direction of air flow or forms of Carburettors:a) Up-drought b) Horizontal c) Down-drought Carburettors.Types of CarburettorSlide5

Types of Carburettor

Depending on the method of varying the mixture strength or

choke area

carburettors are classified as:

1.Open Choke or Constant Choke carburettor The mixture strength is determined by the varying depression of a fixed tube or venturiEg: solex and zenith2.Variable Choke or Constant Depression or

Constant

Vaccum

carburettor

Depression in the choke tube is reasonably constant and the size of the jet is varied to provide the correct mixture for all engine operating conditions.

Eg

: S.U. carburettorSlide6

Venturi

Throttle valve

Metering system

Simple CarburettorSlide7

Various systems or circuits in the carburettor

Float system

Idling and low speed system

High speed system

Power systemAnti-percolatorAccelerating pump systemChoke systemSlide8

AIR CLEANER

CHOKE

VENTURI

THROTTLE VALVE

Float ValveFloat ArmFloat

Float Chamber

Float systemSlide9

Idling and low speed system

Rich mixture is needed- 10:1

It consists of idle passages for fuel and air

Idling system – starting, idling and low speeds

Cut off when speed increases to about 40kmphSlide10

High speed system

Throttle valve is sufficiently opened

Faster air flow through the air horn and greater the vacuum created in the venturi

Additional fuel will be discharged

This system comes in action as soon as the engine speed increases from 33 KMPH Slide11

Power system

When the engine is under strain requiring more power, a richer, a more powerful mixture

Power system is either manually operated or vacuum controlledSlide12

Anti-percolator

This device is to relieve the

vapour

pressure that develops in the carburettor due to the vaporization of fuel in hot weather

This pressure causes flooding of fuelThis valve relieves the pressure by venting the passage in the discharge nozzle to the atmosphereSlide13

Accelerating system

For rapid acceleration, additional fuel must be delivered by carburettor

Quick opening of throttle valve

Produces leaner mixture instead of being richer

Accelerating pump is used to provide correct A-F mixture, discharges directly into mixing chamberSlide14

Choke

For starting the cold engine, a rich mixture is needed

Choke is operated to shut off the air supply to carburettor

During the suction stroke less amount of air, and more amount of fuel is sucked thus a rich mixture is obtained

After starting the engine choke should be opened to atmosphere– else floodingSlide15

Constant Choke or C.C. Carburettor

Here the main orifice known as the choke tube or venturi is of fixed dimensions and metering is affected by varying the pressure drop across it.

e.g

Solex carburettor

Zenith carburettorCarter carburettorStromberg carburettorSlide16

Solex CarburettorSlide17
Slide18

Working of Solex Carburettor

Starter

Consists of a starter valve in the form of flat disc having holes of different sizes

These holes connect the petrol jet and starter jet sides to the passage which opens to air hornStarter lever is operated by the driver At starting bigger holes are connectedAfter starting smaller holesLater in off positionSlide19

2. Idling and low speed operation

From the lower part of the well of the emulsion system a hole leads off to pilot jet(13)

At idling throttle partly closed and engine suction is applied at pilot jet. Fuel from the pilot jet mixes with small amount of air from the small pilot air bleed orifice(14)

The rich mixture for idling is discharged into the throttle body past the idling control screw(15).

By-pass orifice(17) provided on the venturi side of the throttle valve ensures smooth transfer of idle and low speed circuit to the main jet circuit .Slide20

3. Normal running

During normal running, the throttle valve is partly opened and the engine suction is applied at the main jet, which supplies the fuel

Air enters directly through the venturi and mixes with the fuel

The air-fuel mixture is governed by the throttle valveSlide21

4.Acceleration:

A diaphragm type acceleration pump supplies extra fuel needed for acceleration through pump injector

Pump lever is connected to the accelerator so that pressing the pedal, the lever moves towards the left, pressing the membrane towards the left, thus forcing the petrol through pump jet and injector.

On making the pedal free, the lever moves the diaphragm back towards right creating vacuum towards left which opens the pump inlet valve and thus admits the petrol from the chamber into pump.Slide22

Zenith carburettor

3 jets

Main jet, compensating jet (around main jet) and idling jet

Choke valve is used for starting

Idling and slow speed running the air enters through the holesMixes with the fuel in idling passage and passes to the idling jet Slide23

A separate knob is provided for idle adjustment i.e., supply of mixture

When the throttle valve is widely opened, the main jet comes into action along with idling jet

On further opening the throttle valve, the whole suction is applied on the main and compensating jet and idling jet is cut off

The compensating jet takes care of A-F correct ratios at different speedsSlide24

Carter Carburettor

Float circuit

Starting circuit

Idle and low speed circuit

Part throttle circuitFull throttle circuitAcceleration pump circuitSlide25

Constant Depression or C.D. Carburettor or constant vacuum type

SU CARBURETTOR

SU Carburetters (named for Skinners Union, company that produced them) were a brand of carburettor usually of the side draught type but down draught variants were also used.Slide26
Slide27

Working of SU carburettor

It is a constant vacuum or depression type with automatically variable choke or venturi

The mixture compensation is achieved by maintaining constant vacuum over the jet and varying the effective size of the jet

It is a horizontal type of carburettor

Spring loaded piston controls the air passage which is in the form of rectangular opening of constant width and adjustable heightThe position of piston at any instant depends upon the balance of it’s own weight against vacuum forceAs piston weight is constant, vacuum also remain constantConsists of single jet in which a tapered needle operatesA tapering needle is fixed to the piston Slide28

Area of throat is varied by means of a piston which slides up and down

When accelerator is operated the piston moves up and down to control the air supply

And there by needle moves up and down in the jet controlling the fuel supply

Piston moves up throat area increases and air flow increases

Also needle moves up area of jet increases and fuel flow increasesSimilarly it reduces and maintain correct A-F mixture at different operating conditionsUsed in racing cars, scooters and motor cyclesNo separate idling or acceleration device is usedSlide29
Slide30

Petrol Injection

Petrol is supplied into intake manifold through petrol Injectors . This process is called the petrol injection.

The petrol is received by the injector from the pump and is sprayed into the air stream in atomized form.

Adv:High powerQuick starting and warm upLow specific fuel consumptionNo necessity to maintain a stable ignition mixture in the manifoldNo necessity of induction heatingSlide31

Free from icing trouble

Avoidance of acceleration disturbances during cornering and braking

Quick starting and warm-up

Greater freedom in choice of fuels

Dis adv:Higher initial costHigher maintenance costComplicated designDifficult in operationDifficult servicingSlide32

Types

According to location of injector

Cylinder or direct injection system

Port injection system and

Manifold or throttle body injectionAccording to control methodMechanical injectionElectronic injection According to number of injectorsMulti point injection systemSingle point injection systemSlide33

In port injection the Injector is placed on the side of the intake manifold and sprays petrol into the air inside the intake manifold. The petrol mixes with air completely. This mixture of petrol and air then passes through the intake valve and enters into the cylinder.Slide34

Port Injection SystemSlide35

Multi-point fuel injectionSlide36

Single point fuel injection

Single Injector is placed slightly above throat of the throttle body. The Injector sprays petrol into the air in the intake manifold where petrol mixes with air.

This mixture then passes through the throttle valve and enters the intake manifold.Slide37

Octane number

The anti-knock value of fuel is measured in octane number rating (ONR).

The fuel

iso

-octane is highly knock resistant and it is rated 100Normal heptane (n-heptane) knocks easily and it is rated zeroThe percentage of iso-octane by volume in a mixture if iso-octane and n-heptane, which exactly matches the knocking intensity of a given fuel in a standard engine under prescribed operating conditions is termed as “Octane Number” of the fuelSlide38

Cetane number

The

cetane

number of diesel fuel refers to the ease with which the fuel ignites

The best diesel fuel is that which ignites readily and burns steadily and rapidlyIt is rated by means of a scale called cetane ratingThe cetane number assigned to a diesel fuel is a mesure of its ignition qualities compared to those of a standard fuel, normal cetane (C16H34)Lower the cetane number there is more possibility of fuel to knockSlide39

Fuel Injection System in Diesel Engines

Functions of a Fuel injection system:

Filter the fuel

Measure the correct quantity of fuel to be injected

Time the fuel injectionControl the rate of fuel injectionAtomize the fuelDistribute the fuel in the combustion chamberSlide40
Slide41

Air blast injection

In this method the, air is compressed in a compressor to high pressure and injected air blast along with fuel into the cylinder.

The rate of fuel admission can be controlled by varying the pressure of injection air.

Used in large stationary and marine engines

Adv:It provides better atomization and distribution of the fuelAs the combustion is more complete the BMEP is higherInferior fuels can be usedSlide42

Dis

Adv:

It requires high pressure multi stage compression

A separate mechanical linkage is required to time the operation of fuel valve

Due to compression and linkage the size of the engine increasesSince the fuel burns very near to the nozzle it is overheatedSlide43

Airless or Solid Injection

In this method the fuel under high pressure is directly injected into the combustion chamber

It burns due to the heat of compression of the air

This method requires a fuel pump to deliver the fuel at high pressure- 300kg/cm

2 This method is used for all types of small and big diesel enginesSlide44

Comparison between Air blast and Air less injection

Description

Air blast injection

Air less injection

Construction ComplicatedSimple Weight Heavy Light

Cost

Costly

Cheap

Fuel

atomized

Not proper

Properly

Suitable

for engines

Lower

output

Higher

output

Accuracy in manufacturing

Less

More is required for pump barrel and fuel injection plunger

Compressor

Multi stage compressor is required

Not requiredSlide45

Types of modern airless or solid fuel injection system:

Common Rail Injection System

Individual Pump Injection System

Distributor SystemSlide46

COMMON RAIL INJECTION SYSTEM

A single pump supplies high pressure fuel to header, a relief valve holds the pressure constant.

The control wedge adjusts the lift of mechanically operated valve to set amount and time of injection.Slide47

Adv:

System is simple and less maintenance cost

Only one pump is sufficient for multi cylinder engine

It fulfills requirements of either constant load with variable speeds or variable loads with constant speed

Variation in pump supply pressure effects all the cylinders equallyDis adv:Leaks in the injection valveAccurate design and workmanship is requiredSlide48

Individual pump injection system

In this system an individual pump or pump cylinder connects directly to each fuel nozzle.

Pump meters charge and control injection timing.Slide49

Each cylinder has its own individual high pressure pump and metering unit

It is quite compact method and involve higher cost

Dis

adv:

This system has to be designed accurately to pump small quantity of fuelSlide50

Distributor System

In this system the fuel metered at a central point, a pump pressurizes, meters the fuel and times the injection.

From here fuel is distributed to cylinders in correct firing order by cam operated poppet valves which open to admit fuel to the nozzles.Slide51

Fuel injection pump

Generally the fuel injection pumps are classified as

Jerk pump type

Distributor typeSlide52

FUEL PUMP

L is the plunger driven by a cam and tappet mechanism at the bottom . B is the barrel in which plunger reciprocates.

There is a rectangular vertical groove in the plunger which extends from top to another helical groove.

V is the delivery valve which lifts off its seat under the liquid fuel pressure and spring force.

The fuel pump is connected to the fuel atomizer through passage P. SP and Y are the spill and the supply port respectively. When the plunger is at the bottom both ports SP and Y are uncovered by the plunger and fuel enters from the port SP into the barrel. On further upward movement of the plunger both the ports are closed and fuel is compressed and delivered through passage P to the atomizer as delivery valve lifts off from its seat. Slide53

With further rise of the Plunger at certain moment, the port SP is connected to the fuel in the upper part of the plunger through rectangular vertical groove through helical groove , as a result of which sudden fall in pressure occurs and delivery valve occupies seat against the spring force.

The plunger is rotated by the Rack R which is moved in or out by the governor. By changing the Angular position of the helical groove according to the load and speed of the vehicle amount of fuel delivered can be varied.Slide54

Fuel InjectorSlide55

FUEL INJECTOR OR ATOMISER

It consist of a nozzle valve(NV) fitted in the nozzle body (NB).

The nozzle valve is held on its seat by a spring ‘S’ which exerts pressure through spindle E. ‘AS’ is the adjusting screw by which nozzle valve lift can be adjusted.

The fuel under pressure from the fuel pump enters the injector through the passages B and C and lifts the nozzle valve.

The fuel travels down nozzle N and injected into the engine cylinder in the form of fine spray.Then the pressure of the oil falls, the nozzle valve occupies its seat under the spring force and fuel supply is cut off. Slide56

Any leakage of fuel accumulated above the valve is led to the fuel tank through passage-A. The leakage occurs when the nozzle valve is worn out

FP is the feeling pin which indicates whether valve is working properly or not

Usually the nozzle valve is set to lift at 135 to 175 bars pressure. Slide57

Types of filters:

Cloth

Felt

Combination of cloth and felt- heavy vehicles

Paper – better since even smallest dust and dirt particles are removedFelt with paper element- commonly used in heavy vehicles Fuel FilterSlide58

Fuel FilterSlide59

Fuel governor

Different methods to control the flow of fuel:

Hit and miss method-

fuel supply is cut off during few cycles, Used in gas engines

Quality governing- A:F ratio varied based on engine load, used in diesel enginesQuantity governing- quantity of A:F ratio according to engine load, used in petrol enginesTypes of governors:Mechanical or centrifugal governorPneumatic governorHydraulic governor