Fuelihng of IC Engine

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TOPICS TO BE DISCUSSED

WHAT IS ENGINE?

CLASSIFICATION OF ENGINES.

INTERNAL COMBUSTION ENGINE.TYPES OF INTERNAL-COMBUSTION

ENGINES.

COMPONENTS OF IC ENGINES FUEL SUPPLY SYSTEMS

FUNCTIONAL ELEMENTS

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TOPICS TO BE DISCUSSED

COMPONENTS OF INTERNAL COMBUSTIONENGINE.

FUEL SUPPLY SYSTEM OF AN INTERNAL-COMBUSTION ENGINE

FUEL INJECTION SYSTEM

FUEL INJECTION SYSTEM FOR DIESEL

ENGINES COMMON RAIL FUEL INJECTION SYSTEMS

FOR DIESEL ENGINES

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WHAT IS ENGINE?

Engine is a machinefor converting energyinto motion ormechanical work.The energy is usuallysupplied in the formof a chemical fuel,such as oil orgasoline, steam, orelectricity, and themechanical work ismost commonlydelivered in the formof rotary motion of ashaft.

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CLASSIFICATION OF ENGINES

Engines are usually classified according to

The form of energy they utilize, as steam, compressed air, andgasoline.

The type of motion of their principal parts, as reciprocating androtary.

The place where the exchange from chemical to heat energytakes place, as internal combustion and external combustion.

The method by which the engine is cooled, as air-cooled orwater-cooled.

The position of the cylinders of the engine, as V, in-line, andradial.

The number of strokes of the piston for a complete cycle, astwo-stroke and four-stroke.

The type of cycle, as Otto (in ordinary gasoline engines) anddiesel.

And the use for which the engine is intended, as automobileand airplane engines.

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CLASSIFICATION OF ENGINES

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INTERNAL COMBUSTION ENGINE

Internal-Combustion

Engine, any type of machine that

obtains mechanical energy directly from

the expenditure of the chemical energy

of fuel burned in a combustion chamber

that is an integral part of the engine.

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TYPES OF INTERNAL-COMBUSTION ENGINES

Four principal types of internal-combustion engines are in general use:

The Otto-cycle engine. The diesel engine.

The rotary engine.

And the gas turbine.

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COMPONENTS OF INTERNAL

COMBUSTION ENGINE

The essential parts of Otto-cycle and diesel engines arethe same.

The combustion chamber consists of a cylinder, usuallyfixed, that is closed at one end and in which a close-fittingpiston slides. The in-and-out motion of the piston varies

the volume of the chamber between the inner face of thepiston and the closed end of the cylinder.

The outer face of the piston is attached to a crankshaft bya connecting rod. The crankshaft transforms thereciprocating motion of the piston into rotary motion.

Crankshafts have heavy flywheels and counterweights,

which by their inertia minimize irregularity in the motion ofthe shaft. An engine may have from 1 to as many as 28cylinders.

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COMBUSTION ENGINE

ValvesThe intake and exhaust valves open at theproper time to let in air and fuel and to letout exhaust. Note that both valves are

closed during compression and combustionso that the combustion chamber is sealed.

Spark plugThe spark plug supplies the spark that

ignites the air/fuel mixture so thatcombustion can occur. The spark musthappen at just the right moment for thingsto work properly.

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COMBUSTION ENGINE

PistonA piston is a cylindrical piece of metal thatmoves up and down inside the cylinder.

Piston rings

Piston rings provide a sliding seal between theouter edge of the piston and the inner edge ofthe cylinder. The rings serve two purposes:

They prevent the fuel/air mixture and exhaustin the combustion chamber from leaking into

the sump during compression and combustion.They keep oil in the sump from leaking into thecombustion area, where it would be burnedand lost.

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COMBUSTION ENGINE

Connecting rodThe connecting rod connects the piston to thecrankshaft. It can rotate at both ends so thatits angle can change as the piston moves and

the crankshaft rotates. Crankshaft

The crankshaft turns the piston's up and downmotion into circular motion just like a crank ona jack-in-the-box does.

SumpThe sump surrounds the crankshaft. Itcontains some amount of oil, which collects inthe bottom of the sump (the oil pan).

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WORKING OF VALVES IN 4-STROKE IC

ENGINE/ OTTO-CYCLE ENGINE


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WHAT IS FUEL SYSTEM?

The function of the fuel system is to store

and supply fuel to the cylinder chamber

where it can be mixed with air, vaporized,

and burned to produce energy. The fuel,which can be either gasoline or diesel is

stored in a fuel tank. A fuel pump draws the

fuel from the tank through fuel lines and

delivers it through a fuel filter to either acarburetor or fuel injector, then delivered to

the cylinder chamber for combustion.

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FUEL SYSTEM

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FUNCTION OF FUEL SYSTEM

The function of fuel system is to supply the enginewith fuel in qualities exactly metered in proportionto the power required and timed with utmostaccuracy, so that the engine will deliver that powerwithin the limits prescribed for fuel consumption,

exhaust smoke, noise and exhaust emissions. The fuel must be injected through suitable nozzles at

pressures high enough to cause the required degreeof atomization in the combustion chamber and toensure that it mixes with sufficient air for completecombustion in the cycle time available.

In multi cylinder engines the periods of injection, thetiming and the delivered quantity must be accuratelymetered to ensure an even balance between thecylinders.

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FUEL SYSTEM

. In the past, fuel

metering on automotive engines was usuallyperformed by a carburetor. However, thisdevice has been largely replaced by fuel

injection into the intake manifold or ports,which increases fuel economy and

efficiency while lowering exhaust gasemissions. Various types of fuel managementsystems are used on automotive engines,

including electronically controlled feedbackcarburetors, mechanical continuous fuel

injection, and sequential electronic fuelinjection.

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OBJECTIVES OF THE INJECTION

SYSTEM

The injection system of the compressionignition engine should fulfill the followingobjectives consistently and precisely:

1. Meter the appropriate quantity of fuel,as demanded by the speed of, and theload on, the engine at the given time.

2. Distribute the metered fuel equally

among cylinders in a multi-cylinderengine.3. Inject the fuel at the correct time (with

respect to crank angle) in the cycle.

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4. Inject the fuel at the correct rate (perunit time or crank angle degree).

5. Inject the fuel with the correct spraypattern and sufficient atomization asdemanded by the design of thecombustion chamber, to provide properpenetration also.

6. Begin and end injection sharply withoutdribbling or after injection.

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OBJECTIVES OF THE INJECTION

SYSTEM


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FUNCTIONAL ELEMENTS

To accomplish these objectives, a number offunctional elements are required. Theseconstitute together, the fuel injection

system of the engine. These elements are asfollows.

Pumping elements to transfer the fuel fromthe tank to the cylinder, along with theassociate piping and hardware.

Metering elements to measure and supplythe fuel at the rate as desired by the speedand load conditions prevailing.

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Metering controls to adjust the rate ofthe metering elements for changes inload and speed of the engine.

Distributing elements to divide themetered fuel equally among thecylinders in a multi cylinder engine.

Timing controls to adjust the start andstop of injection.

Mixing elements to atomize anddistribute the fuel within the combustionchamber

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FUNCTIONAL ELEMENTS


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COMPONENTS OF FUEL SUPPLY SYSTEM

OF AN INTERNAL-COMBUSTION ENGINE.

The fuel supply system of an internal-combustion engine consists of

Fuel Tank

Fuel Lines Fuel Pump

Fuel Filters

And a device, Atomizer, for vaporizing oratomizing the liquid fuel. In Otto-cycleengines this device is either a carburetoror, more recently, a fuel-injection system.

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COMPONENTS OF FUEL SUPPLY SYSTEM OF

AN INTERNAL-COMBUSTION ENGINE.

Fuel tank stores the fuel for engine.

Tank location and design are always a compromise withavailable space. Most automobiles have a single tank located inthe rear of the vehicle.

Fuel tanks today have internal baffles to prevent the fuel from

sloshing back and forth. If you hear noises from the rear onacceleration and deceleration the baffles could be broken.

All tanks have a fuel filler pipe, a fuel outlet line to the engineand a vent system.

All catalytic converter cars are equipped with a filler piperestrictor so that leaded fuel, which is dispensed from a thickernozzle, cannot be introduced into the fuel system.

All fuel tanks must be vented. Before 1970, fuel tanks werevented to the atmosphere, emitting hydrocarbon emissions.Since 1970 all tanks are vented through a charcoal canister,into the engine to be burned before being released to theatmosphere. This is called evaporative emission control.

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Steel lines and flexible hoses carry

the fuel from the tank to the engine.

When servicing or replacing the steellines, copper or aluminum must never

be used. Steel lines must be replaced

with steel. When replacing flexible

rubber hoses, proper hose must be

used.

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A fuel pump is the device that transfers fuel fromthe fuel tank into an internal combustion engine.

A fuel pump is an essential component on a caror other internal combustion engine device. Fuelhas to be pumped from the fuel tank to theengine and delivered under low pressure to thecarburetor or under high pressure to the fuelinjection system. Some fuel injected engineshave two fuel pumps for this purpose: one low

pressure/high volume supply pump in the tankand one high pressure/low volume pump on ornear the engine.

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In earlier cars built before the late 1970s, thepump was mechanically driven by a lobe onthe engine's camshaft and therefore bolted tothe engine block. It created negative pressure

to "suck" the gasoline through the lines.However, the negative pressure from thepump, in combination with heat from theengine and/or hot weather, could cause thegasoline to boil. The fuel pump, designed to

pump liquid, not vapor, would be unable tosuck more gasoline to the engine, which wouldcut out. This condition is known as "vapourlock".

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TYPES OF FUEL PUMP

Two types of fuel pumps are used in

automobiles:1. Mechanical

2. Electric

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MECHANICAL FUEL PUMP Carbureted cars use mechanical fuel pumps.

Mechanical fuel pumps are diaphragm

pumps, mounted on the engine and operatedby an eccentric cam usually on the camshaft.A rocker arm attached to the eccentricmoves up and down flexing the diaphragmand pumping the fuel to the engine.

While mechanical pumps operate onpressures of4-6 psi (pounds per squareinch).

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ELECTRIC FUEL PUMP

All fuel injected cars today use electric fuel pumps.

Electric pumps do not depend on an eccentric foroperation, they can be located anywhere on the

vehicle. In fact they work best when located nearthe fuel tank.

Electric pumps can operate on pressures of30-40psi.

Current is supplied to the pump immediately when

the key is turned. This allows for constant pressureon the system for immediate starting. Electric fuelpumps can be either low pressure or highpressure.

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FUEL PUMP SAFETY It creates positive pressure in the fuel lines, pushing the

gasoline to the engine. The higher gasoline pressureraises the boiling point. Placing the pump in the tank puts

the component least likely to handle gasoline vapor well(the pump itself) farthest from the engine, submersed incool liquid. Another benefit to placing the pump inside thetank is that it is less likely to start a fire. Though electricalcomponents (such as a fuel pump) can spark and ignitefuel vapors, liquid fuel will not explode and thereforesubmerging the pump in the tank is one of the safestplaces to put it. In most cars, the fuel pump delivers aconstant flow of gasoline to the engine; fuel not used isreturned to the tank. This further reduces the chance ofthe fuel boiling, since it is never kept close to the hotengine for too long.

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OPERATING A FUEL PUMP The fuel pump is generally on whenever the

car's ignition switch is in the "on" position.

Depressing the gas pedal results in the throttlebody opening on the engine (metering the airgoing in) rather than engaging the fuel pump.The ignition switch does not carry the power tothe fuel pump, instead it activates a relay

which will handle the higher current load.It iscommon for the fuel pump relay to become

oxidized and cease functioning; this is muchmore common than the actual fuel pumpfailing.

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FUEL PUMPS IN AN ACCIDENT Some cars with an electronic control unit have

safety logic that will shut the electric fuel pump

off even if the ignition is "on" if there is no oilpressure, either due to engine bearingdamage or a stalled engine in a car accident.In case of an accident this will also prevent

fuel leaking from any ruptured fuel line. Othercars have an additional roll over valve, that willshut off the fuel pump in case the car rolls

over.

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The fuel filter is the key to a properly functioning fueldelivery system. This is more true with fuel injectionthan with carbureted cars.

Fuel injectors are more susceptible to damage from

dirt because of their close tolerances, but also fuelinjected cars use electric fuel pumps.

When the filter clogs, the electric fuel pump works sohard to push past the filter, that it burns itself up.Most cars use two filters.

One inside the gas tank and one in a line to the fuel

injectors or carburetor. Unless some severe andunusual condition occurs to cause a large amount ofdirt to enter the gas tank, it is only necessary toreplace the filter in the line.

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FUEL SYSTEM

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Atomization is conversion of bulk liquid into aspray or mist (i.e. collection of drops), oftenby passing the liquid through a nozzle.

Despite the name, it does not imply that theparticles are reduced to atomic sizes.

An atomizer is an atomization apparatus;carburetors, airbrushes, misters, and spraybottles are only a few examples of atomizersused ubiquitously. In internal combustionengines, fine-grained fuel atomization isinstrumental to efficient combustion.

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Carburetor, device that mixes fuel and air for burning in aninternal-combustion engine. A carburetoratomizes(converts into a vapor of tiny droplets) liquid gasoline. Anairflow carries the atomized gasoline to the enginescylinders, where the gas is ignited.

The carburetor has been part of internal-combustionengines since the beginning of the 20th century. In mostpassenger vehicles and light trucks built since 1985 thecarburetor has been replaced by fuel injection, a moreefficient, computer-controlled method of injecting fuel intothe engine. Diesel engines, because of their design, havealways used fuel injection instead of carburetors.Carburetors today are found only on older gasolineengines in cars and trucks. They are still common in boatengines, aircraft engines, and some sports vehicles,including jet-skis and motorcycles.

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FUNCTIONS OF CARBURETOR

1) it combines gasoline and air creating

a highly combustible mixture.

2) it regulates the ratio of air and fuel.

3) it controls the engine's speed

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A carburetor basically consists of an open pipe, thecarburetor's "throat" or "barrel", through which the airpasses. The pipe is in the form of a venturi - it narrows insection and then widens again.

Just after the narrowest point is a butterfly valve or throttle- a rotating disc that can be turned end-on to the airflow,so as to hardly restrict the flow at all, or can be rotated sothat it (almost) completely blocks the flow of air.

This valve controls the flow of air through the carburetorthroat and thus the quantity of air/fuel mixture the systemwill deliver. This in turn affects the engine power and

speed. The throttle is connected, via a Bowden cable or aset of rods and ball joints, to the accelerator pedal on acar or the equivalent control on other vehicles orequipment.

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THROTTLE VALVE A throttle valve at the base of the carburetor controls the

amount of air pulled through the engine by the partialvacuum in the pistons. The driver opens the throttle valveby pressing down on the accelerator (gas pedal). As the

valve opens wider, more air flows through the carburetor,delivering larger amounts of fuel to the engine. The drivercloses the throttle valve by decreasing pressure on thegas pedal.

FLOAT BOWL

The fuel that enters the carburetor is stored in a reservoircalled a float chamber or float bowl. A device that floats onthe reservoirs surface is linked to a small valve, whichkeeps a constant amount of fuel in the reservoir.

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VENTURI Carburetors pull fuel into the airflow using a principle

called Bernoullis effect, named for Dutch-born Swissscientist Daniel Bernoulli. Bernoulli discovered that

pressure in a fluid decreases as its velocity increases.Italian physicist Giovanni Venturi (1746-1822) designed aspecialized type of passageway for fluids based onBernoullis effect. A carburetor has such a passageway,called a venturi, in its throat.

The venturi is a narrowing of the carburetors throat andmakes the throat look a little like an hourglassnarrow inthe middle and wider at the ends. Air rushing through thenarrow part speeds up. At the same time, air pressureagainst the sides of the passageway decreases, creatinga partial vacuum inside the throat. This partial vacuumdraws fuel through the nozzle and into the air.

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THE WORKINGS OF THE VENTURI TOSPEED THE FLOW OF FUEL

A fluid passing through smoothly varying

constrictions is subject to changes invelocity and pressure, as described byBernoulli's principle. A Venturi is a systemfor speeding the flow of the fluid, by

constricting it in a cone-shaped tube. Theyare found in many applications where thespeed of the fluid is important, and form thebasis of devices like a carburetor.

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Venturis are also used to measure thespeed of a fluid, by measuring pressurechanges from one point to another alongthe venturi. Placing a liquid in a U-shapedtube and connecting the ends of the tubesto both ends of a venturi is all that isneeded. When the fluid flows though theventuri the pressure in the two ends of thetube will differ, forcing the liquid to the "lowpressure" side. The amount of that movecan be calibrated to the speed of the fluidflow.

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Venturi are more expensive to construct than asimple orifice plate which uses the same principle asa Venturi, but the orifice plate causes significantlymore permanent energy loss and is less accurate.

A venturi can also be used to mix a fluid with air. If apump forces the fluid through a tube connected to asystem consisting a venturi to increase the waterspeed (the diameter decreases), a short piece oftube with a small hole in it, and last a venturi thatdecreases speed (so the pipe gets wider again), airwill be sucked in trough the small hole because ofchanges in pressure, and at the end of the system amixture of fluid and air will appear.

To avoid undue drag, a venturi typically has an entrycone of30 degrees and an exit cone of5 degrees.

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IDLE AND TRANSFER PORTS In addition to the main nozzle in the venturi portion of

the carburetor, two other nozzles, or ports, deliverfuel to the engine. The idle port is located below the

venturi and allows the engine to get fuel when airflowthrough the carburetor is minimal, such as when theengine is idling at a low speed. An off-idle or transferport located just above the idle port deliversadditional fuel at low engine speeds. Fuel from thesetwo ports is drawn into the cylinders by engine

vacuum. The two ports supply enough fuel to keepthe engine running at slow speeds. Fuel from themain nozzle is necessary to run the engine at normaloperating speeds.

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AIR-FUEL RATIO A carburetor can be adjusted to mix larger or smaller

amounts of air with the fuel. An idling engine at normaloperating temperature requires an air-to-fuel ratio of about

15-to-1 (by weight) to completely burn the fuel. Raising orlowering the air ratio makes the mix either lean(containing less fuel) or rich (containing more fuel). A leanmixture produces a cleaner, hotter combustion for cruisingspeeds, but not enough fuel for starting the engineefficiently or allowing it to produce more power. A richmixture is easier for the engine to burn, but produces

more pollutants as byproducts. The carburetor is adjusted to provide a rich mixture for

cold engine starts because the rich mixture burns easierand longer. As the engine warms up, the carburetor altersthe air-fuel ratio for a leaner mixture.

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CHOKE AND COLD STARTS The choke is a device that can partially block

air from getting into the carburetor. If the

throttle valve is open and the choke valve isclosed, the vacuum from the engine is strongenough inside the carburetor to draw fuel fromall three nozzles. This added fuel produces arich air-fuel ratio to help a cold engine get

started. Once the engine is warm, the choke isshut off. Early automobiles had manuallyoperated chokes. The process eventuallybecame automatic and electronicallycontrolled.

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CARBURETOR ADJUSTMENT Too much fuel in the fuel-air mixture is referred to as too "rich"; not

enough fuel is too "lean". The "mixture" is normally controlled byadjustable screws on an automotive carburetor or a pilot-operatedlever on a propeller aircraft (since mixture is air density (altitude)dependent). The correct air to petrol ratio is 14.6:1, meaning that foreach weight unit of petrol, 14.6 units of air will be burned.Carburetor adjustment can be checked by measuring the carbonmonoxide and oxygen content of the exhaust fumes. A moresophisticated way to determine correct mixture, as used in modernfuel injected engines, is by using a lambda sensor in the exhaustsystem. The lambda sensor output is fed to the enginemanagement system that in turn will adjust the amount of injected

fuel. The mixture can also be judged by the state and color of the spark

plugs: black, dry sooty plugs indicate a too rich mixture, white tolight grey deposits on the plugs indicate a lean mixture. The correctcolor should be a brownish grey.

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HOW A CARBURETOR MIXES FUEL ANDAIR?

When the piston moves down the cylinder on the intakestroke it draws air from the cylinder and intake manifold. A

vacuum is created that draws air from the carburetor. Theairflow through the carburetor causes fuel to be drawnfrom the carburetor through the intake manifold past theintake valves and into the cylinder. The amount of fuelmixed into the air to obtain the required air to fuel ratio iscontrolled by the venturi or choke. When air flows throughthe venturi its speed increases and the pressure drops.

This causes the fuel to be sucked into the air stream froma hole or jet. When the engine is at idle or at rapidacceleration there is not enough air passing through theventuri to draw fuel. To overcome these problems othersystems are used.

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DELIVERING GASOLINE TO THECARBURETOR

Gasoline is delivered to the carburetor by thefuel pump and is stored in the fuel bowl. Tokeep this level of fuel stored in the bowlconstant under all conditions a float system isused. A float operated needle valve and seatat the fuel inlet is used to control the fuel levelin the bowl. If the fuel level drops below a

certain level the float lowers and opens thevalve letting more fuel in. When the float risesit pushes the inlet valve against the seat andshuts off the flow of fuel into the bowl.

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HANDLING LOW SPEEDS When the engine is idle there is very little air flowing

through the venturi because the throttle valve is closed.The idle port allows the engine to operate under this

condition. Fuel is forced through the idle port because of apressure differential between air in the fuel bowl andvacuum below the throttle valve. Idle fuel mixture iscontrolled by an adjustable needle valve.

HANDLING HIGH SPEEDS At higher engine speeds more fuel is drawn from the main

nozzle. Fuel comes from the fuel bowl through the fuelnozzle and into the throat of the carburetor where it mixeswith air.

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THE CARBURETOR UNDER HIGH ENGINELOAD

Higher engine loads demand more fuel. Thecarburetor handles this by increasing the amount offuel through the power valve controlled by the intakemanifold vacuum. Manifold vacuum travels from thebase of the carburetor to the power valve through apassage. The manifold vacuum under normalrunning conditions holds the valve closed becausethe vacuum is at its greatest. As the engine load isincreased the vacuum drops and the power valvestarts to open. The valve will be completely openedwhen the engine is under a heavy load resulting invery low vacuum.

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THE CARBURETOR DURINGENGINE ACCELERATION

When an engine initially accelerates thebalance of air and fuel is thrown offbalance because fuel is heavier than air.This results in more air than fuel, an overlylean mixture. To solve this, the accelerator

pump is used to supply more fuel to theengine. This maintains the balance until thefuel air ratio reaches proper levels. Theaccelerator pump is operated by a linkageand does not rely on vacuum to operate.

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THE CARBURETOR UNDER COLDENGINE STARTING CONDITIONS

Cold engine starting uses more fuel because the fuel is not fullyvaporized due to less air in the carburetor. To increase the

amount of fuel during starting the choke plate is used. When thechoke plate is closed the vacuum in the carburetor increasesand pulls more fuel from the fuel nozzle and both the idle ports.The choke is usually thermostatically controlled but can becontrolled manually. Once the engine gets started the amount ofextra gas for starting needs to reduced. This is done by usingthe vacuum in the intake manifold, which pulls the chokepartially opened to stop too much gas from flowing in the engineand allowing more air flow while the engine starts. As theengine warms up the thermostat control of the carburetor opensthe plate until the engine reaches normal temperature. Atnormal running engine temperature, the plate will be fully open.

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TYPES OF CARBURETORS

There are two types of carburetors:

1. Fixed choke

2. Constant depression

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FIXED CHOKE CARBURETORS

Fixed choke carburetors, makes the varying airpressure in the venture alter the fuel flow; this is

the common downdraft carburetor found on

American and most Japanese cars.

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CONSTANT DEPRESSIONCARBURETORS

The constant depression carburetors vary theairflow to change the fuel jet opening witch in turn

altars the fuel flow. A vacuumed operated pistonconnected to a tapered needle, which slides insidethe fuel jet, does this. The most common variablechoke (constant depression) type carburetor is theside draft SU carburetor, which was simple inprinciple to adjust and maintain. This rose to a

position of domination in the UK car market for thatreason. Other similar designs are used on someEuropean and a few Japanese automobiles

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Carburetor is also categories as

Natural or side draft Updraft

Downdraft

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NATURALDRAFTCARBURETOR

This carburetor isused where thereis little space on

top of the engine.The air horizontallyinto the manifold.

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UPDRAFTCARBURETORS

This type is placed

low on the engineand use a gravityfed-fuel supply. Inother words, the

tank is above thecarburetor and thefuel falls to it

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DOWNDRAFTCARBURETORS

This carburetoroperates withlower airvelocities andlargerpassages. Thisis becausegravity assiststhe air-fuelmixture flow tothe cylinder.

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Fuel-Injection System, method of delivering fuel toan internal-combustion engine.

In a fuel-injection system, electronically controlledfuel injectors spray measured amounts of fuel intoeach of the engines cylinders where the fuel is

burned, powering the engine. Modern, computer-operated fuel injection produces

more power, lower exhaust emissions, improved fueleconomy, and smoother operation than a carburetorsystem.

F

uel injection began replacing the carburetor duringthe 1980s and is now the fuel-delivery system forvirtually all new automobiles. Fuel injection hasalways been the standard fuel-delivery system fordiesel engines.

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The fuel injection may be purely mechanical, purelyelectronic or a mix of the two. Early systems weremechanical but from about 1980 onward more andmore systems were completely electronic. By themiddle of the decade, nearly all new passenger

vehicles were equipped with electronic fuel injection.The 1990 Subaru Justy was the last passenger carsold in the United States with a carburettor.

The modern electronic systems that cars areequipped with today utilise a number of sensors tomonitor engine conditions, and an electronic control

unit (ECU) to accurately calculate the neededamount of fuel. Thus fuel injection can increase fuelefficiency and reduce pollution.

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History

Frederick William Lanchester joined the Forward Gas EngineCompany Birmingham, England in 1889. He carried out whatwere possibly the earliest experiments with fuel injection. Fuelinjection has been used in diesel engines since the mid 1920s,almost from their introduction (due to the higher energy required

for diesel to evaporate). It was adapted for use in petrol-powered aircraft during World WarII and a system developedby Bosch was first used in a car in 1955 with the introduction ofthe Mercedes-Benz 300SL. An electronic fuel injection systemwas also developed by the Bendix Corporation.

Fuel injection became widespread with the introduction ofelectronically controlled fuel injection systems in the 1980s and

the gradual tightening of emissions and fuel economy laws.Meeting modern emissions standards whilst retainingacceptable performance would be impossible without it. Inaddition, the development of microprocessor technology madeit possible to control the amount of fuel injected precisely.

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COMPARISON WITH CARBURETOR

As in a traditional carburetor, fuel is converted to a finespray and mixed with air. However, where a traditional

carburetor forces the incoming air through a venturi to pullthe fuel into the air stream, a fuel injection system forcesthe fuel through nozzles under pressure to inject the fuelinto the air stream without requiring a venturi.

The use of a venturi reduces volumetric efficiency byapproximately 15%, which results in a reduction in engine

power. Thus, a fuel injection system increases the powerthat an engine with the same engine displacement willproduce. Additionally, fuel injection allows for moreprecise control over the mixture of fuel and air, both inproportion and in uniformity.

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FUEL INJECTOR A typical injector has a nozzle, a needle valve that blocks the

opening in the nozzle by protruding from it, and a compressionspring.

A pump controlled by the ECM shoots fuel into the injector withenough pressure to compress the spring. This pressure lifts theneedle valve, which opens the nozzle.

In another type of injector, the nozzles opening is blocked by asmall ball held in place by a plunger. The ECM controls amagnetic switch that pulls the plunger upward and lets fuelspray past the ball into the combustion chamber. Another signalfrom the ECM pushes the plunger, which pushes the ball intoplace and stops the flow of fuel.

An ECM opens the injector nozzle, holds it open, and closes itafter a precise interval, more than 1000 times per minute athighway speeds.

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THROTTLE-BODY INJECTION Electronic throttle-body injection (normally

called TBI, though Ford used theabbreviation, CFI) was introduced in theearly 1980s as a transition technology tofully-electronic port injection. The systeminjects fuel into the throttle-body (a wetsystem), so fuel can condense and cling tothe walls of the intake system, harmingemissions. Computer-controlled TBI wasinexpensive and simple, however, andlasted well into the 1990s.

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CENTRAL PORT INJECTION General Motors developed a new "in-

between" technique called central port

injection or CPI. It uses tubes from acentral injector to spray fuel at the intakeport rather than the throttle-body (it is adry system). However, fuel is

continuously injected to all portssimultaneously, which is less thanoptimal.

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SEQUENTIAL CENTRAL POINTINJECTION

GM refined the CPI system into a

sequential central port injection (SCPI)system in the mid-1990s. It used valves tometer the fuel to just the cylinders thatwere in the intake phase. This worked wellon paper, but the valves had a tendency tostick. Fuel injector cleaner sometimesworked, but the system remainedproblematic.

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MULTI-PORT FUEL INJECTION

The goal of all fuel injection systems isto carefully meter the amount and timing

of fuel to each cylinder. This is achievedwith the more sophisticated fuel injectionsystems, often called multi-port fuelinjection (MFI) or sequential port fuel

injection (SFI). It uses a single injectorper cylinder and sprays the fuel rightabove the intake valves.

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DIRECT INJECTION The newest method for petrol engines now is direct

injection or DI. It has a special fuel injector inside thecombustion chamber itself, along with the valves andspark plugs. This system is just appearing in the mid-2000s, and like most systems before, it is beingpioneered in Diesel applications. This method wasused in various WWII aircraft as well. Notableengines included the Daimler Benz DB 605 and laterversions of the Wright R-3350 used in the B-29Super fortress.In direct injection, the pistonincorporates a depression (often toroidal) which iswhere initial combustion takes place. Direct injectiondiesel engines are generally more efficient thanindirect injection engines, but tend to be noisier.

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DIRECT INJECTION


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DIRECT INJECTION

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Y


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HOW IT WORKS One type of fuel injection (throttle-body injection, or TBI)

sprays a fuel mist through one or more injectors locatednear the start of the intake manifold, which carries air tothe individual cylinders. The injectors in a TBI system are

located in the intake manifold close to where a carburetorwas typically housed. The pistons in the cylinders create apartial vacuum that pulls fuel and air through the manifoldinto the combustion chambers. Port-type fuel-injectionsystems, sometimes called multi-port systems, haveinjectors that spray fuel directly into each cylinders intake

portan opening through the engine into the combustionchamber. A port-type injection is better able to deliverequal amounts of fuel to each cylinder. Moving theinjectors to the ports also permits alterations to the intakemanifold that improve engine performance.

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Y


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HOW IT WORKS To start the engine, the ECM regulates fuel flow and

ignition timing according to preset specifications. As theengine warms up, sensors report temperatures in theintake manifold and the cylinder head, which forms the

top of the combustion chamber. Other sensors relayinformation about the position of the crankshaft andwhether fuel is igniting too early inside the combustionchambers. More sensors report vehicle speed,transmission status, changes in manifold pressure (theair pressure inside the intake manifold), and oxygen

content of the exhaust gas. Using information fromthose and other sensors, the ECM adjusts the fuel-injection and ignition-timing systems for differentdriving conditions.

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FUEL INJECTION SYSTEM FOR


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FUEL INJECTION SYSTEM FOR DIESEL

ENGINE CONSISTS OF

Electronic distributor pump

Electronic unit injector (EUI)

High-pressure common rail

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DIESEL ENGINE



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Electronic DistributorPump

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Electronic Unit Injector (EUI)

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DIESEL ENGINE



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High-Pressure Common Rail

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DIESEL ENGINE

COMMON RAIL FUEL INJECTION


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COMMON RAIL FUEL INJECTION

SYSTEM AND ITS FUNCTION

Provide the diesel engine with fuel

Generate the high pressure needed for fuel

injection and distribute the fuel to the

individual cylinders

Inject precisely correct amount of fuel at

exactly the right moment in time.

In contrast to other injection systemCommon rail fuel injection system is an

accumulator injection system.

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HOW DOES A CR SYSTEM


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HOW DOES A CR SYSTEM

FUNCTION?

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Subfunctions of aCRFIsystem

Lowpressurecircuit Highpressurecircui ECUwithsensors

COMMONRAILFUELINJECTIONSYSTE

THE COMMON RAIL SUB


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THE COMMON RAIL SUB

FUNCTIONS

Low pressure circuit comprises of:

Fuel tank ,Pre-supply pump, Fuel filter,And the respective connection lines.

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LOW PRESSURE CIRCUIT


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LOW PRESSURE CIRCUIT

The low pressure circuit isresponsible for transporting the fuel tothe high pressure circuit.

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THE COMMON RAIL SUB


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THE COMMON RAIL SUB

FUNCTIONSHigh pressure circuit comprises:

High pressure pump with pressure control valve

The high pressure accumulator (Rail )with the rail pressure sensor

Injectors, and

The respective high pressure connection lines.

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THE HIGH PRESSURE


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THE HIGH PRESSURE

CIRCUIT

It is the responsibility of the high

pressure circuit to generate a constant

unvarying high pressure in the high

pressure accumulator (the rail) and to

inject the fuel through the injectors

into the engines combustion

chambers.

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THE COMMON RAIL SUB FUNCTIONS


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The common rail ECU evaluates the signals fromthe following sensors:

Boost pressure sensor, Air temperaturesensor,

Air mass meter, and Rail pressure sensor.

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ECU and sensors

The sensor are responsible for measuring important physicalquantities. The ECU calculates injected fuel quantity, start ofinjection, duration of injection, and rate of discharge curve,as well supervises the correct functioning of the injectionsystem as a whole.

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COMMON RAIL FUEL INJECTION SYSTEM


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DESIGN

PRE SUPPLY PUMP

Transports fuel from the fuel tank to the

high pressure pump.

An electric fuel pump is used for this

purpose in the CRFIS.

When the electric fuel pump is switched

off, the supply of fuel is interrupted andthe engine stops.

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PRE SUPPLY PUMP


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PRE SUPPLY PUMP

The electric fuel pump comprises of:

1.Electric Motor

2.Roller-Cell Pump

3.Non Return Valve

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PRE SUPPLY PUMP


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PRE SUPPLY PUMP

The roller cell isdriven by anelectric motor.

Its rotor ismountedeccentrically andprovided with slotsin which movablerollers are free totravel.

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PRE SUPPLY PUMP


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PRE SUPPLY PUMP

The rollers areforced against thebase plate byrotation and by

fuel pressure . The fuel is

transported to theoutlet openings

on the pumpspressure side.

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PRE SUPPLY PUMP VARIANTS


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PRE SUPPLY PUMP VARIANTS

Gear type fuelpump

The drive gearwheel is driven by

the engine . Delivery quantity is

directlyproportional toengine speed .

Shut off is bymeans of anelectromagnet..

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HIGH PRESSURE PUMP


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HIGH- PRESSURE PUMP

The pump plunger moves downwards

The inlet valve opens

The fuel is drawn in to the pumping element

chamber(suction stroke)

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HIGH PRESSURE PUMP


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HIGH- PRESSURE PUMP

At BDC, the inlet valve closes

The fuel in the chamber can be compressed

by the upward moving plunger.

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HIGH PRESSURE PUMP


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HIGH- PRESSURE PUMP

An

electromagnet

is used for

pumping

element switch-off.

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RAIL-PRESSURE SENSOR


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(RDS)

Measures the pressure in the rail

inputs the information to theECU

RDS should provide extremely precise

measured values.

RDS is mounted directly on the rail.

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INJECTOR


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INJECTOR

Injects exactly the correct amount of fuel

in to the combustion chamber at

precisely the right moment in time

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INJECTOR


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INJECTOR

The injector is equipped with: 2/2 electromagnetic servo valve

Nozzle

Valve control chamber

Return line

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INJECTOR


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INJECTOR

The essential forces for correct functioningare:

Nozzle-spring force

Valve spring force Electromagnet force

Force due to the pressure in the valve-control chamber

Force due to the pressure in the nozzleneedle

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COMMON RAIL FUEL INJECTION SYSTEM

SUMMARY


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SUMMARY

Components of CRFIS are:

Pre-supply pump

High-pressure pump

High-pressure accumulator(rail)

Pressure-control valve

Rail-pressure sensor

Injectors

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A DUAL FUEL CONVERSION SYSTEM FOR


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DIESEL ENGINES

Dual fuel systems, engines that operate

on more than one fuel source, are

gaining popularity because they reduce

the amount of diesel fuel used. Until recently, adding a dual fuel system

was impractical due to the cost of

replacing the original engine and the

loss of power traditionally associated

with these replacement systems.

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A DUAL FUEL CONVERSION SYSTEM FOR


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Energy Conversions, Inc. (ECI), has invented a

dual fuel conversion system that easily converts

diesel engines into diesel-natural gas engines,

eliminating the need for companies to replace their

diesel engines with natural gas engines. The system reduces emissions by allowing

engines to operate cleanly on domestically

produced natural gas while still maintaining the

potential to operate on traditional diesel fuel as

well.

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DIESEL ENGINES


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Fuelihng of IC Engine

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