IC Engine in autmobile engineering

7/25/2019 IC Engine in autmobile engineering

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1. INTERNAL COMBUSTION ENGINE(ICE) is a heatenginewhere the combustion of a

fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of

the working fluid flow circuit.

2. A HEAT ENGINEis a system that converts heator thermal energy to mechanical energy,

which can then be used to do mechanical work. It does this by bringing a working substance

from a higher state temperature to a lower state temperature.

3. CLASSIFICATION OF I.C. ENGINE

1. CYCLE OF OPERATION a. Two stroke engine B. Four stroke engine

2. THERMODYNAMIC CYCLE Otto cycleDiesel cycleDual cycle

3. METHOD OF IGNITION S.I. ENGINEC,I. ENGINE

4. NO. OF CYLINDERS SingleMulti

5. COOLING SYSTEM Air cooledWater cooledOil cooled

6. FUEL USED PetrolDieselGas7. SPEED High speed Lows peed Medium speed

4. ACCORDING TO ARRANGEMENT OF CYLINDERS

VerticalHorizantalV- engineRadial engineOpposed cylinderOpposed piston

5. APPLICATIONAutomotive engines, Aircraft engines, Marine application, Generatorsets

6. PETROL V/S DIESEL ENGINE

Otto Cycle Diesel Cycle

AirFuel Mixture Suction Stroke Only Air Sucked During Suction Stroke

Spark Plug Is Needed No Spark Plug Needed

C.R.=6-12 C.R.= 14-22

Low Efficiency High Efficiency

Light Weight Heavy

Cheap Costly

Less Vibration & Noise More

Motor Cycles, Cars, Light Duty VehTrucks,Buses,GensetsCONSIDERATION CYLINDER GASES

The theoretical cycle based on the actual properties of the cylinder contents is called thefuelair cycle.The fuelair cycle take into consideration the following:

1. The actual composition of the cylinder contents.

2. The variation in the specific heat of the gases in the cylinder.

3. The dissociation effect.
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4. Compression & expansion processes are frictionless5. No chemical changes in either fuel or air prior to combustion.6. Combustion takes place instantaneously at top dead center.8. All processes are adiabatic.9. The fuel is mixed well with air.10. Subsequent to combustion, the change is always in chemical equilibrium.

COMPOSITION OF CYLINDER GASES The effect of cylinder composition on theperformance of the engine caneasily computed by means of suitable numericaltechniques. The computer analysis can produce fast and accurate results.

Process SI Engine

Intake Air, Fuel, Recycled exhaust & Residual gas Air, Recycl

Compression Air, Fuel Vapor, Recycled exhaust & Residualgas

Air, Recyc

Expansion Composition products (CO2,CO,H2,O2,NO,OH,O,H,)

CompositioOH,H2O,O

Exhaust Composition products (mainlyN2,CO2,H2O) Compositio

FUEL TYPES FOR IC ENGINE1.CONVENTIONAL:(a) Crude oil derived(i) Petrol

(ii) Diesel(b) Other sources:(i) Coal(ii) Wood (includes bio-mass)(iii)Tar Sands(iv)Shale

2. Alternate:(A) PETROLEUM DERIVED(i) CNG

(Total Replacement)(ii) LPG

(B) BIO-MASS DERIVED (iii) Producer gas(i) Ethanol (iv) Biogas(ii) Vegetable oils iv) Hydrogen


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PENTROLEUM COMPONENTS/ELEMENTSPetroleum or crude oil is a complex mixture of hydrocarbons and other chemicals. Thecomposition varies widely depending where and how the petroleum was formed. In fact, achemical analysis can be used to fingerprint the source of the petroleum. However, rawpetroleum or crude oil has characteristic properties and composition.

Hydrocarbons in Crude Oil

There are four main types of hydrocarbons found in crude oil.1. PARAFFINS (15-60%)1. NAPHTHENES (30-60%)2. AROMATICS (3-30%)3. ASPHALTICS (remainder)

The hydrocarbons primarily are alkanes, cycloalkanes and aromatic hydrocarbons.

Elemental Composition of Petroleum

Although there is considerable variation between the ratios of organic molecules, theelemental composition of petroleum is well-defined:

1. Carbon - 83 to 87%

2. Hydrogen - 10 to 14%

3. Nitrogen - 0.1 to 2%

4. Oxygen - 0.05 to 1.5%

5. Sulfur - 0.05 to 6.0%

6. Metals - < 0.1%

REFINING PRODUCTS

The primary end-products

produced in petroleum refining

may be grouped into four

categories: light distillates,

middle distillates, heavy distillates

and others.
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Light distillates[edit]

Liquid petroleum gas (LPG)

Gasoline (also known as petrol)

Heavy Naphtha

Ligh

Middle distillates[edit]

Kerosene Automotive and rail-road diesel fuels

Residential heating fuel

Other light fuel oils

Heavy distillates[edit]

Heavy fuel oils

Bunker fuel oil and other residual fuel oils

octane and other stuff

SI DESIRED QUALITY OF FUEL FOR SPARK IGNITION (SI) ENGINES1) Volatility: The gasoline should be volatile; a certain part of it should vaporize at room

temperature to allow easy starting of the engine. Better vaporization of the fuel facilitates

its even distribution inside the cylinders, which in turn leads to better acceleration of the

vehicle.

2) Dilution of the lubricating oil in crankcase: As the fuel is splashed in the cylinder,

some lubricating oil from the crankcase is also washed away with it. This leads to overall

decrease in the quantity of the lubricating oil and poor lubrication of the engine's moving

parts. To prevent such possibilities, it is important that the type of gasoline used for the

engine should vaporize before it gets combusted.

3)Antiknock qualities of the fuel: Abnormal burning or detonation of the fuel inside the

engine leads to the effect known as engine knock. During detonation large amounts of

heat is released inside the engine which excessively increases the temperature and

pressure inside the engine, drastically reducing its thermal efficiency. The fuel should

have the tendency to avoid creating the situation of detonation; this quality of the fuel is

the antiknock property of the fuel.

4) Gum deposits formed from the fuel: When gasoline is stored for longer periods of

time, it has the tendency to oxidize and form gummy, solid substances. When used with

an engine, such gasoline will cause sticky valves and piston rings, carbon deposits in the

engine, gum deposits in the manifold, clogging of carburetor jets, and enlarging of

cylinders and pistons. The gasoline used in the engine should have a tendency to form

lower gum content and have a lower tendency to form gum during storage.

5) Low sulfur content: Hydrocarbon fuels may contain sulfur in various forms like

hydrogen sulfide and other compounds. Sulfur is corrosive in nature and it can cause fuel

line corrosion, carburetor parts, injection pumps, etc. Sulfur also promotes knocking of

engine; hence its content in the gasoline fuel should be kept to a minimum.
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CI FUEL

1) Knocking characteristics: In case of the CI engine the burning of fuel occurs

due to compression of air. It is desired that as soon as the fuel is injected into

the cylinder, it starts burning, but in practical situations this never happens as there is

always a time lag between the injection of the fuel and burning of the fuel. As the

duration of ignition lag increases, more and more amounts of fuel get accumulated in thecylinder head. When the fuel is finally burnt, excessively large amounts of energy is

released, which produces extremely high pressure inside the engine. This causes the

knocking sound inside the engine, which can be clearly heard. Thus the engines should

have a short ignition lag so that the energy is produced uniformly inside the engine and

there is no abnormal sound. The ignition of the fuel also affects starting, warming, and

production of exhaust gases in the engine.

The knocking capacity of the fuel is measured in terms of cetane rating of the fuel. The

fuel you are using for your CI engine should have a cetane number high enough to avoid

knocking of engine.2) Volatility of the fuel: Thorough mixing of the fuel and air when fuel is injected in the

cylinder head ensures uniform burning of the fuel. The fuel should be volatile in nature

within the operating temperature range of the cylinder head so that it gets converted into

a gaseous state and mixes thoroughly with compressed air.

3) Starting characteristics of the fuel:

4) Smoke produced by the fuel and its odor:

5) Viscosity of the fuel:.

6) Corrosion and wear:

7) Easy to handle:

DETERMINATION OF CALORIFIC VALUE FROM DULONG FORMULA

Calorific value =1/100[8080 C + 34500 {H O/8 } +2240 S] kcal/kg

where C, H, O, S refer to % of carbon, hydrogen, oxygen and sulphur respectively.

HYDROCARBON COMBUSTIONrefers to the type of reactionwhere a

hydrocarbonreacts with oxygen to create carbon dioxide, water, and

heat. Hydrocarbonsare molecules consisting of both hydrogen and carbon. They aremost famous for being the primary constituent of fossil fuels, namely natural gas,

petroleum, and coal.

GENERAL REACTIONEQUATION


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PETROLEUM PRODUCTS (NET CALORIFIC VALUE)

LPG--- ---10800

GASOLINE/NAPTHA--- ---10500

KEROSENE----- -10300

JET FUEL--- ---10300

FUEL OIL--- ---9600

NATURAL GAS---- --8000 - 9480

ELECTRICITY---- -860

A fuel pumpis a frequently (but not always) essential component on acar or

otherinternal combustion engined device. Many engines (older motorcycle engines in

particular) do not require any fuel pump at all, requiring only gravity to feed fuel from the

fuel tank through a line or hose to the engine. But in non-gravity feed designs, fuel has to

be pumped from thefuel tank to the engine and delivered under low pressure to

thecarburetor or under high pressure to thefuel injection system. Often, carbureted

engines use low pressure mechanical pumps that are mounted outside the fuel tank,

whereas fuel injected engines often use electric fuel pumps that are mounted inside the

fuel tank (and some fuel injected engines have two fuel pumps: one low pressure/high

volume supply pump in the tank and one high pressure/low volume pump on or near the

engine).[1]

MECHANICAL

ELECTRICAL

LIMITATIONS OF A SIMPLE CARBURETTOR.

01)At a very low speed, the mixture supplied by a Simple Carburetor is so weak that it
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will not ignite properly and for its enrichment, at such conditions some arrangement in

the Carburettor is required to be made.

02)The working of Simple Carburetor is effected by changes of Atmospheric

Pressure.Carburettors used in Aircraft are to be provided with Altitude control, as the rich

mixture is unnecessarily available,due to less Density of Air.

03)The working of Simple Carburettor is effected by changes of Atmospheric

Temperature.If the setting is done in Winter season,it will be found to give too rich

mixture in the Summer.This is happened due to less Density of Air with the rise of

Temperature to a grater extent than the Density of fuel.

04)It gives the proper mixture at only one engine speed and load,therefore,suitable only

for Engines running at constant speed increase or decrease ,the quantity of Fuel issuing

out will change and not match the Velocity of Air flowing through the Venturi and proper

mixture is not take place.To overcome this various modifications have to be made in

Simple Carburettor.

FUEL INJECTION SYSTEM

The purpose of the fuel injection system is to deliver fuel into the engine cylinders, while

precisely controlling the injection timing, fuel atomization, and other parameters. The main

types of injection systems include pump-line-nozzle, unit injector, and common rail.

Modern injection systems reach very high injection pressures, and utilize sophisticated

electronic control methods.

The primary purposes of the diesel fuel injection system are graphically represented in

Figure 1. FUNCTIONS OF DIESEL FUEL INJECTION SYSTEM

Injection Timing Control

Atomization, Bulk Mixing & Air Utilization

Injection Quality Control


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THE FUEL INJECTOR

The diesel engine, unlike some gasoline engines, does not use a carburetor to mix thefuel and air nor does it use a spark to ignite the fuel-air mixture. Instead, the diesel usesan injection system to spray the fuel into the engine cylinder. The fuel must enter againstthe pressure of the air that has been compressed in the cylinder by the engine piston. Theair may be at a pressure of 3100 kPa and at a temperature of 540C. Therefore, when thefuel is injected into this high temperature air, it will ignite and burn. This type of fuelinjection is called a solid injection system, as the fuel is pumped directly into eachcylinder.

The solid injection method has three different designs or variations. They are:

(1) The individual pump system

(2) The distributor system

(3) The common rail system

The Individual Pump System

The basic components of this system are shown in Fig.17.
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The Distributor SystemIn the distributor system shown in Fig. 18, the fuel is pumped from the storagetank to a single high-pressure pump by a low-pressure transfer pump. The high-pressurepump then injects the fuel to each cylinder nozzle in the proper firing order by means ofa distributor. The distributor contains a rotating channel, which lines up the pumpdischargewith the fuel line to the desired fuel nozzle or injector.

The Common Rail System

The common rail system is illustrated in Fig. 19. A low-pressure pump, pumps thefuel from the tank to the injectors. A separate injector is located at each enginecylinder. Most of the fuel returns from the injector to the tank via the drain orifice B in theinjector and via the drain manifold. Some fuel, however, passes through the meteringorifice C into the cavity D under the injector plunger. When the proper firing point occurs ineach cylinder, the injector lever, driven by the camshaft, pushes the injector plunger downand forces the fuel under high pressure into the cylinder.
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FUEL PUMPS AND INJECTORS

Individual fuel pumps are mounted on the top face of the frame at each cylinderand are directly actuated by the camshafts. This allows individual adjustment of eachpump to equalize the load over all the cylinders. The proximity of each pump to its

corresponding fuel injector and the use of short connecting pipes ensure that equaldistribution of the load is maintained under all conditions. The individual fuel pumps are ofthe reciprocating plunger type. Each has a rotating outer sleeve, which controls the fueldelivered per stroke. An anti-dribble, spring loaded, non return delivery valve is part of thefuel pump discharge. The pump is designed to allow easy adjustment of both timing andquantity of fuel injected. A large diameterskirt over the cam follower prevents fuel from leaking into the lubrication system. Injectorsare of the multi-hole nozzle type, centrally located in the cylinder heads, and connected tothe fuel pumps by short, rigid lengths of fuel delivery pipe. Atomization of the fuel at thenozzle is a result of passing through a spring-loaded needle valve.

SUPERCHARGINGSupercharging involves the use of a blower to force more air into the cylinderof a diesel engine or more air-fuel mixture into the cylinder of a gasoline engine. In bothcases the result is an increase in the power output, because the amount of fuel burned isincreased.The blowers used are usually the rotary lobe type or the centrifugal type.Gearing or a belt connects the lobe type blower to the engine shaft. The centrifugal typeblower may be similarly driven or it may be driven by an exhaust gas turbine in whichcase it is called a turbocharger.
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The roots or lobe type of blowers are positive displacement air pumps. Theairflow is proportional to engine speed. This is an advantage at low engine speeds, butmaybe a disadvantage if the engine starts to overload and slow down. The blower alsoslows down,further reducing power output.

Supercharging should not be confused with scavenging.Scavenging refers to

the removal of the exhaust gases from the cylinder by blowing air through, as in Fig. 4A.The air left in the cylinder when the compression stroke commences, however, is not

already compressed to any extent as it is with the supercharger. Roots blowers are used

on some two-stroke diesels for scavenging.

AN INJECTION PUMPis the device that pumps diesel (as the fuel) into the cylinders of

adiesel engine.Traditionally, the injection pump is driven indirectly from thecrankshaft by

gears, chains or a toothed belt (often thetiming belt)that also drives thecamshaft.It

rotates at half crankshaft speed in a conventionalfour-stroke diesel engine.Its timing is

such that the fuel is injected only very slightly beforetop dead centre of that cylinder's

compression stroke. It is also common for the pump belt on gasoline engines to be driven

directly from the camshaft. In some systems injection pressures can be as high as

200 MPa (30,000 PSI).

A GOVERNOR, OR SPEED LIMITER, is adevice used to measure and regulate

thespeed of amachine,such as anengine.A classic example is thecentrifugal

governor,also known as theWatt or fly-ball governor, which uses weights mounted onspring-loaded arms to determine how fast a shaft is spinning, and then usesproportional

control to regulate the shaft speed.

GOVERNORGovernor is a mechanical device designed to control the speed of an engine withinspecified limit used ontractor or stationary engines for:(i) Maintaining a nearly constant speed of engine under different load conditions(ii) Protecting the engine and the attached equipments against high speeds, when theload is reduced

or removed. Tractor engines are always fitted with governor. There is an importantdifference in principle between the controls of a tractor engine and that of a motor car. Incase of motor car, the fuel supply is under direct control of the accelerator pedal, but intractor engine, the fuel supply is controlled by the governor. The operator changes theengine speed by moving the governor control lever. A governor is essential on a tractorengine for the reason that load on the tractor engine is subjected to rapid variation in thefield and the operator cannot control the rapid change of the engine speed without anyautomatic device. For example, if the load on the tractor is reduced, the engine wouldtend to race suddenly. If the load is increased, the engine would tend to slow downabruptly. Under these circumstances, it becomes difficult for the operator to regulate
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always the throttle lever to meet the temporary changes in the engine load. A governorautomatically regulates the engine speed on varying load condition and thus the operatoris relieved of the duty of constant regulating the throttle lever to suit different loadconditions.

CENTRIFUGAL GOVERNORS :

In centrifugal governors, multiple masses know as governor balls, are responsible to

revolve about the axis of a shaft, which is driven through suitable gearing from the engine

crankshaft. Each ball is acted upon by a force which acts in the radially inward direction

and is provided by dead weight, a spring or a combination of two. This force is commonly

called as the controlling force and it will increase as the distance of the ball from the axis

of rotation increases. The inward or outward movement of the ball is transmitted by the

governor mechanism to the valve which controls the amount of energy supplied to the

engine.INERTIA GOVERNOR :

In inertia governors, the balls are arranged in manner that the inertia forces caused by

angular acceleration or retardation of the governor shaft tend to change their position. The

obvious advantage of inertia governor lies in its rapid response to the effect of a change of

load. This advantage is small, however by the practical difficulty of arranging for the

complete balance of the revolving parts of the governor. For this reason Centrifugal

governors are preferred over the inertia governors.

A FUEL FILTERis afilter in the fuel line that screens outdirt andrust particles from the

fuel, normally made into cartridges containing afilter paper. They are found in

mostinternal combustion engines
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A SUPERCHARGER is an air compressor that increases the pressure or density of air

supplied to an internal combustion engine. This gives each intake cycle of the engine

more oxygen, letting it burn more fuel and do more work, thus increasing power.

Power for the supercharger can be provided mechanically by means of a belt, gear, shaft,

or chain connected to the engine'scrankshaft. When power is provided by

aturbine powered byexhaust gas,a supercharger is known as a turbo supercharger

Types of supercharger

There are two main types of superchargers defined according to the method of gas

transfer:positive displacement and dynamic compressors.

1. Positive displacement blowers and compressors deliver an almost constant level of

pressure increase at all engine speeds (RPM).

2. Dynamic compressors do not deliver pressure at low speeds; above a threshold

speed, pressure increases with engine speed.[6]

POSITIVE-DISPLACEMENTpumps deliver a nearly fixed volume of air per revolution at

all speeds (minus leakage, which is almost constant at all speeds for a given pressure,

thus its importance decreases at higher speeds).

Major types of positive-displacement pumps include:

Roots

Lysholm twin-screw

Sliding vane

Scroll-type supercharger,also known as the G-Lader

DYNAMIC

Dynamic compressors rely on accelerating the air to high speed and then exchanging that

velocity for pressure by diffusing or slowing it down.

Major types of dynamic compressor are:

Centrifugal

Multi-stage axial-flow

Pressure wave supercharger
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TURBOCHARGERS

In the turbocharger, Fig.22, exhaust gases from the engine drive the gas

turbine, which drives the centrifugal blower as they are connected to the same shaft. This

arrangement forces more air into the engine. As the engine load and speed increases the

speed of the turbocharger increases. Turbochargers on medium size diesel engines turn

at speeds of 70 000 r/min. At peak load the turbocharger speed can go as high as 130

000 r/min.

As the turbocharger rotor speed increases the compressor forces more air into

the engine. As more air is forced into the engine more fuel can be burned. The maximum

power of an enginemay be increased by up by 50%-70% using a turbocharger. The heat

of compression is removed from the air in the intercooler and this reduces the specific

volume of the air and allows a greater weight to be forced into the cylinder. The engine

depicted is a four-stroke cycle diesel.

CI ENGINE TUROCHARGER

Turbocharger is a super-charging device that uses exhaust gases to turn a turbine toforce extra air into the cylinders.

Turbo-charging has been very common on large CI engines for many years because thistype of engine is particularly suited to pressure charging. Unlike the SI engine, the CIengine does not suffer from compression limitations. In addition, since only air being in theinduction system and more under-bonnet space is available on a CI unit, fitting of a

turbocharger is much easier.
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TURBO VS SUPERCHARGER

The supercharger can be powered by a belt, gear, shaft, or chain. There are quite a fewdifferent types of superchargers but the take-away point is thisa supercharger isconnected to the crankshaft. Meaning, a supercharger is always driven by the carsengine.

A turbo does the same job as the superchargerforce more air into the cars engine tomake more power. However, a turbo uses a turbine and is NOT connected to thecrankshaft. Instead of the engine, the turbo gets driven by the cars exhaust gases.

The advantages and disadvantages are obvious. Supercharger, being attached at thecrankshaft, equals less efficiencymore fuel to power it. With a turbo, you dont affectefficiency because it is exhaust drivenno additional stress on the engine.

It is important to note advances in both supercharger and turbo technologies are makinggreat progress. New turbos have all but eliminated turbo lag and there are highly efficientsuperchargers on the market as well.

TURBOCHARGER ON A NORMALLY ENGINE PROVIDES FOLLOWINGADVANTAGES :(a) Greater torque and power are produced. Since the increase in power can be as highas 60 percent, the engine is smaller and lighter than an un-supercharged unit of equalpower output.(b) Fuel consumption is improved by about 10 percent.(c) Exhaust noise is reduced due to the smoothing out of the exhaust pulsations.

SI ADVANTAGES AND DISADVANTAGES OF SUPER CHARGER

The advantages of turbo-charging a SIengine include:

(a) Higher torque for acceleration from low speed.

(6) Lower exhaust noise and emission.

(c) Better fuel economy due to a reduction in the pumping energy expended during the

induction stroke. Generally this advantage is seldom achieved in practice because many

drivers alter their driving technique of take full advantage of the extra power of a

turbocharged engine.

The main disadvantages of a turbocharged SI engine, in addition to the extra hazards

created by the incompetent drivers when they attempt to demonstrate the extra

performance, are:

(a) Higher initial cost of turbocharger and allied equipment.

(6) Higher repair and servicing costs especially when a defective unit damages other


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engine components.

(c) Delayed engine response after depressing the accelerator. Since the turbine takes a

time to reach its effective speed, an acceleration delay occurs with older type units.

Temperature effects and intercoolers[edit]

One disadvantage of supercharging is that compressing the air increases its temperature.

When a supercharger is used on an internal combustion engine, the temperature of the

fuel/air charge becomes a major limiting factor in engine performance. Extreme

temperatures will causedetonation of the fuel-air mixture (spark ignition engines) and

damage to the engine. In cars, this can cause a problem when it is a hot day outside, or

when an excessive level of boost is reached.

PRE-IGNITION :

Pre-ignition means a burning of fuel is form the spark it happens due to hot spot in

combustion chamber like carbon deposition.

Heated spark plug, heated valve and high compression ratio due to occur.

Pre-ignition will develop excessive pressure before the end of compression stroke which

has a tendency to push the piston in opposite direction to which it is moving.

Due to pre-ignition there is loss of power and violent thumping and may stop the engine.

Pre-ignition will cause still higher temperature and pressure then occurs earlier power

stroke.

DETONATION :

Fuel should burn in single stroke but due to above said problem the fuel could not burn

single stroke the fuel to spark plug will get burn plug get burn after some time, this create

high surge with produce noise that is known as detonation.

Pressure waves strike the cylinder walls producing pinking or ranking sound with

vibration.

This hammering noise is known as detonation.EFFECT OF DETONATION :1) Noise.2) Mechanical damage.3) Increase heat transfer.4) Pre-ignition5) Decrease in power output and efficiency.
https://en.wikipedia.org/w/index.php?title=Supercharger&action=edit&section=11https://en.wikipedia.org/wiki/Engine_knockinghttps://en.wikipedia.org/wiki/Engine_knockinghttps://en.wikipedia.org/w/index.php?title=Supercharger&action=edit&section=11


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THREE STAGE OF COMBUSTION

There are three stages of combustion in SI Engine as shown

1. Ignition lag stage 2. Flame propagation stage 3. After burning stage

THE FACTORS WHICH AFFECT THE FLAME PROPAGATIONS ARE

1. Air fuel ratio 2. Compression ratio

3. Load on engine 4. Turbulence and engine speed5. Other factors-----Self ifnition----Knocking

KNOCKING (also knock, detonation, spark knock, pinging or pinking) in spark-ignition

internal combustion engines occurs when combustion of the air/fuel mixture in the cylinder

does not start off correctly in response to ignition by the spark plug, but one or more

pockets of air/fuel mixture explode outside the envelope .

THE TYPICAL ANTIKNOCK AGENTS IN USE ARE:

Tetraethyllead (Still in use as a high octane additive)

Alcohol

Methylcyclopentadienyl manganese tricarbonyl (MMT)

Ferrocene

Iron pentacarbonyl

Toluene

Isooctane
https://en.wikipedia.org/wiki/Tetraethylleadhttps://en.wikipedia.org/wiki/Methylcyclopentadienyl_manganese_tricarbonylhttps://en.wikipedia.org/wiki/Ferrocenehttps://en.wikipedia.org/wiki/Iron_pentacarbonylhttps://en.wikipedia.org/wiki/Toluenehttps://en.wikipedia.org/wiki/Isooctanehttps://en.wikipedia.org/wiki/Isooctanehttps://en.wikipedia.org/wiki/Isooctanehttps://en.wikipedia.org/wiki/Toluenehttps://en.wikipedia.org/wiki/Iron_pentacarbonylhttps://en.wikipedia.org/wiki/Ferrocenehttps://en.wikipedia.org/wiki/Methylcyclopentadienyl_manganese_tricarbonylhttps://en.wikipedia.org/wiki/Tetraethyllead


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THE BASIC REQUIREMENTS OF A GOOD COMBUSTION CHAMBER ARE TO

PROVIDE:

_ High power output

_ High thermal efficiency and low specific fuel consumption

_ Smooth engine operation

_ Reduced exhaust pollutants

FUEL & FUEL SYSTEM

PROPERTIES OF FUELFuel is a substance consumed by the engine to produce energy. The common fuels forinternal combustionengines are:1. Petrol2. Power kerosene

3. High speed diesel oil4. Light diesel oil.The important properties of these fuels are given below:

QUALITY OF FUELThe quality of the fuel mainly depends upon the following properties:1. Volatility of the fuel2. Calorific value of the fuel3. Ignition quality of the fuel

Volatility: Volatility of fuel has considerable effect on the performance of the engine byaffecting thefollowing:(i) Ease of starting the engine.(ii) Degree of crankcase oil dilution,(iii) Formation of vapour lock in the fuel system,(iv) Accelerating characteristics of the engine,(v) Distribution of fuel in multi-cylinder engine.

In I. C. engine, all the liquid fuel must be converted into vapour fuel before burning. Highspeed diesel oilis most difficult to vapourise. Vapourising temperature of high speed diesel

oil is higher than that of the petrol, hence the petrol vapourises quicker than diesel oil inthe engine cylinder. This helps in easy starting of petrol engines.Calorific value: The heat liberated by combustion of a fuel is known as calorific value orheat value of the fuel. It is expressed in kcal /kg of the fuel. The heat value of a fuel is animportant measure of its worth, since this is the heat which enables the engine to do thework.Ignition quality: Ignition quality refers to ease of burning the oil in the combustionchamber. Octanenumber and cetane number are the measures of ignition quality of the fuel.


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(a) Octane numb er: It is a measure of knock characteristics of a fuel. The percentage ofiso-octane (C8 H18) in the reference fuel consisting of a mixture of iso-octane and normalheptane (C7H16), when it produces the same knocking effect as the fuel under test, iscalled octane number of the fuel. Iso-octane has excellent antiknock qualities and is givena rating of 100. Normal heptane would knock excessively and hence it is assigned a valueof zero.(b) Cetane numb er: The percentage of cetane in a mixture of cetane (C16 H34) andalphamethylnaphthelene (C11 H16) that produces the same knocking effect as the fuel under test iscalled cetane numberof the fuel. Diesel fuels are rated according to cetane number which is the indication ofignition quality of the fuel. The higher the cetane number the better the ignition quality ofthe diesel fuel. The commercial diesel fuels have got cetane rating varying from 30 to 60.

Detonat ion (Knock ing): Detonation or engine knocking refers to violent noises, heard inan engine, giving a pinging sound during the process of combustion. It occurs during the

process of combustion of the

S.NoName of fuel oil A. P. I. degree , Specific Gravity CALORIFIC VALUE. kcal/kg and B.T.U./lb(i) Light diesel oil (L.D.O.) 22 0.920 10300 18600(ii) High speed diesel oil (HSD) 31 0.820 10550 19000(iii) Power kerosene 40 0.827 10850 19500(iv) Petrol 63 0.730 11100 20000

PRE-IGNITION:

Burning of air-fuel mixture in the combustion chamber before the pistonhas reached the top dead centre is called pre-ignition. Pre-ignition occurs when thecharge is fired too far ahead of the top dead centre of the piston due to excessive sparkadvance or excessive heat in the cylinder.CARBURETTOR:The process of preparing an air-fuel mixture away from the cylinders of an engine is calledcarburetion andthe device in which this process take place is called carburettor.Principle of carburettor: The basic principle of all carburettor design that when air flowsover the end of a narrow tube or jet containing liquid, some liquid is drawn into the airstream. The quantity of liquid drawn into the air stream increases as the speed of air flowover the jet increases and also the quantity is greater if the jet is made larger.

Function of Carburettor: The main functions of the carburettor are:(i) To mix the air and fuel thoroughly(ii) To atomise the fuel(iii) To regulate the air-fuel ratio at different speeds and loads and(iv) To supply correct amount of mixture at different speeds and loads.


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FUEL SYSTEM OF DIESEL ENGINEDuring engine operation, the fuel is supplied by gravity from fuel tank to the primary filterwhere coarse impurities are removed. From the primary filter, the fuel is drawn by fueltransfer pump and is delivered to fuel injection pump through second fuel filter. The fuelinjection pump supplies fuel under high pressure to the injectors through high pressurepipes. The injectors atomise the fuel and inject it into the combustion chamber of theengine. The fuel injection pump is fed with fuel in abundance. The excess fuel is by-passed to the intake side of the fuel transfer pump through a relief valve.The maincomponents of the fuel system in diesel engine are:(1)fuel filter (2) fuel lift pump (3) fuel injection pump (4) atomisers and (5) high pressure

pipe.

FUEL LIFT PUMP (FEED PUMP OR TRANSFER PUMP)It is a pump, which transfers fuel from the fuel line to the fuel injection pump. It is mountedon the body offuel injection pump. It delivers adequate amount of fuel to the injection pump. The pumpconsists of:

(I)BODY (2) PISTON (3) INLET VALVE AND (4) PRESSURE VALVE.The valves are tightly pressed against their seats by springs. The piston is free to slide inthe bore. The fuel contained in the space below the piston is forced to flow through

secondary fuel filter to the injection pump. At the same time downward movement of thepiston creates a depression in the space above the piston which, causes the fuel to bedrawn in the transfer pump from the fuel tank through the inlet valve and the primary filter.

FUEL INJECTING PUMP


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It is a pump, which delivers metered quantity of fuel to each cylinder at appropriate timeunder highpressure. Tractor engines may use two types of fuel injection pump:

(i) Multi-element pump and (ii) Distributor (Rotary) type pump.

FUEL INJECTOR: It is the component, which delivers finely atomised fuel under highpressure to thecombustion chamber of the engine. Modern tractor engines use fuel injectors, which havemultiple holes.

Main parts of injector are: nozzle body and needle valve. The nozzle body and needlevalve are fabricated from alloy steel. The needle valve is pressed against a conical seat inthe nozzle body by a spring. Theinjection pressure is adjusted by adjusting the screw.IHPis the power made by the engine, inside the cylinder due to the fuel burning, without

accounting any transmission losses.

BHPis the power made at the wheels of the vehicle. Losses due to the transmission and

driveline affect it. The values obtained in chassis dynamometer testing is the BHP.

IN SIMPLE TERMS BHP= IHP - FP,

where FP is the frictional power loss. Frictional loss is directly proportional to square of

the engine speed.

FUEL INJECTION SYSTEMDiesel fuel is injected in diesel engine through injectors with the help of fuel injection

pump. The systemusing injectors, fuel injection pump, fuel filter, and fuel lines is called fuel injection system.The mainfunctions of fuel injection system are:(i) To measure the correct amount of fuel required by engine speed and load,(ii) To maintain correct timing for beginning and end of injection,(iii) To inject the fuel into the combustion space against high compression pressure.(iv) To atomise the fuel for quick ignition.Process of fuel injection in diesel engine is of two types: (i) Air injection (ii) Solid injection.


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Air injection: In this process, the engine uses compressed air to force the fuel into thecylinder. It is a bulky system and hence it is not considered very suitable for vehicles andtractors. It is mostly used on heavy-duty stationary engines.

Solid injection:A high-pressure pump is used for forcing the fuel into the combustionchamber.

COMBUSTION CHAMBERA combustion chamber is a space inside the engine, where the combustion of fuel takesplace. In dieselengine, the fuel is atomised, vapourised and burnt inside combustion chamber, whereasin spark ignitionengine, atomisation of fuel takes place in the carburettor and vaporisation occurs incarburettor as well asthe inlet manifold. Combustion chamber is classified as:(a) Direct injection chamber

(b) Indirect injection chamber

FUEL FILTERIt is a device to remove dirt from fuel oil. Solid particles and dust in diesel fuel are veryharmful for giving a fine degree of filtration. Fuel injection equipment in diesel engines isextremely sensitive to dirt and solid particles present in fuel. A filter is used to remove thedirt and solid particles from the fuel to ensure trouble free fuel supply. It consists of ahollow cylindrical element contained in a shell, an annular space being left between theshell and the element. The filtering element consists of metal gauge in conjunction withvarious media such as packed fibres, woven cloth, felt, paper etc. These filters are

replaced at certain intervals, specified by the manufacturer.

Usually there are two filters in diesel engine: (1) Primary filter and (2) Secondary filter.The primary filter removes water and coarse particle of dirt from the fuel. The secondaryfilter removes fine sediments from the fuel.

IC Engine in autmobile engineering

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