Basic Mech

7/29/2019 Basic Mech

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SASTRA UNIVERSITY

SCHOOL OF MECHANICAL

ENGINEERING

BASIC MECHANICAL

ENGINEERING


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BOILERS


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The function of the boiler is to generate steam

at the desired conditions efficiently and with

low operating costs.

Low pressure steam is used in cogeneration

plants for heating or process applications, and

high pressure superheated steam is used for

generating power via steam turbines.

Boilers form an important part of the plantutilities.


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Horizontal , Vertical And Inclined

According to the axis of the shellFire Tube And Water Tube

According to the flow of water and hot gasses

Externally And Internally Fired

According to the position of the furnaceForced Circulation And Natural Circulation

According to the circulation of water

High Pressure And Low Pressure

According to the pressure of steam developedStationary And Portable Boiler

Single Tube And Multy Tube BoilersAccording to the number of fire tubes

Natural Draught And Forced Draught

According to the movement of air circulation

BOILER CLASSIFICATION


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BOILERS

BABCOCK AND WILCOX BOILER

La MONT BOILEER

BENSON BOILER


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Boiler shell 9 meters length and 2 meters dia

Water tubes 5 to 15 and 10 cm dia

Up take header and Down take header

Grate

Furnace Baffles

Superheater

Mud box

Damper

Inspection door

BABCOCK AND

WILCOX BOILER


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SPECIFICATIONS

Diameter of drum 1.5 to 2 m

Length 6to 10m

Diameter of water tubes 7.5 to 10.5cm Diameter of superheater tubes 3.5 to 5.5cm

Working pressure 40 bar( max)

Efficiency 60 to 80%


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BABCOCK AND WILCOX BOILER


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La-M0NT BOILER

Feed tankEconomizer

Radiant evaporator

Convection evaporatorConvection superheater

Steam outlet

Capacity50000kg/hr , 170 bar , 5000C


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BENSON BOILER

Mark Benson

Critical pressure of steam 200 bar

Steam rate capacity is 1,50,000 kg/hr

Temp of steam is around 650

At the critical pressure , both water and steam have

the same density so bubbles will not form The first modern high pressure drumless boiler

developed by mark benson was put into operation in

1927 in a German power plant.


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BENSON BOILER

Feed tank

Economizer

Radiant evaporator

Convection evaporator

Convection superheater

Steam outlet Capacity

150000kg/hr , 200 bar , 6500C


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Boiler Mountings and Accessories

Fitting and devices which are necessary for the safety and control are

knows as boiler mountings

Fitting or devices which are provided to increase the efficiency of the boiler

and help in the smooth working of the plant are knows as boiler

accessories.

Fittings which are essential from the safety point of view

are as follows,

Water level indicators

Safety valves

Combined high steam and low water safety valve

Fusible plug


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Fittings which are essential from the controlpoint of view are as follows,

Pressure gauge Junction or stop valve

Feed check valve

Blow-off cock

Man hole and Mud Box

The important accessories are

SuperheaterEconomiser

Air-preheater

Feed pump or injector


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TURBINES


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Turbine is also called as a prime mover


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A turbine is a rotary engine that extracts

energy from a fluid flow and converts it into

useful work.


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The main components of an turbines are:

Nozzle

shaft

disc with curved blades fixed on its periphery

casing


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CLASSIFICATION

Impulse turbine

Simple impulse turbine( De- Laval turbine) Velocity compounded impulse turbine(Curtis

Turbine)

Pressure - compounded impulse turbine(Rateau

Turbine)

Pressure - Velocity compounded impulse

turbine

Reaction turbine or Impulse Reactionturbine ( Parsons Turbine)


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IMPULSE TURBINE

The turbine in which the impulse action ofhigh velocityjet of steam , due to its change in

direction, is used to rotate the turbine shaft is

known as impulse turbine.

In this turbine the kinematic energy of steam

is converted in to mechanical energy in the

moving blades.


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IMPULSE TURBINE

De- Lavalturbine


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Impulse Stage


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P

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IMPULSE TURBINE


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REACTION TURBINE

The turbine in which the reaction force, due toexpansion of high pressure steam where it passesthrough sets of moving and fixed blades, is used torotate the turbine shaft is known as reaction turbine

Due to expansion of steam ,pressure drop occurscontinuously over both fixed and moving blades.

Because of this continuous pressure drop there isalways a difference of pressure between the two sidesof both fixed and moving blades.

This pressure difference exerts a thrust on the blades.The resulting reaction force imparts rotary motion.


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REACTION TURBINE

High pressure steam from the boiler is directly suppliedto the reaction turbine, without passing throughnozzles.

Steam expands as it flows through the fixed andmoving blades. Since the steam expands as it flowsthrough the moving blades, there will be continuousdrop of pressure of steam.

This produces a reaction on the blades and this reaction

force causes the rotor to rotate. Since the propulsiveforce causing the rotation of the rotor is the reactionforce ,the turbine is called reaction turbine.


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REACTION TURBINE


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Reaction Turbine
http://www.techhairball.com/engineering/mechanical-engineering/1522-compounding-methods


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Compounding methods.

The disadvantage of single stage impulse turbine

is that its extremely high speed, of the order ofabout 30,000 rpm , cannot be directly used forpractical purposes. To reduce the high speed,more than one set of moving blades are used. This

is called compounding of impulse turbine.

There are three main types of compounding.These are:

Pressure-compounding Velocity compounding

Pressure-velocity compounding
http://www.techhairball.com/engineering/mechanical-engineering/1522-compounding-methodshttp://www.techhairball.com/engineering/mechanical-engineering/1522-compounding-methods


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VELOCITY COMPOUNDING


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Velocity-compounded Stage


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Pressure-compounded Stage


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IMPULSE TURBINE


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Pressure-velocity Compounded Turbine


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http://www.awazpost.com/turbine-stages/88650/pressure/


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The difference between impulse and reactionturbine goes here......

In case of an impulse turbine the pressure

remains same in the rotor or runners, but incase of reaction turbine the pressure decreasesin runners as well as stators also.

In case of impulse turbine the pressure drophappens only in the nozzle part by means of itskinetic energy. In case of Reaction one the

stators those are fixed to the diaphragm act asa nozzle.


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COMPARISONS

1. It consists of nozzles and movingblades

2. Steam strikes the blades withKinetic energy

3. Pressure drops in nozzles

4. Because of large pressure dropthe blade speed and steam speedare high

5. Profile type blade shape

6. Not much power developed

7. Due to more pressure drop the

number of stages required is less8. Low efficiency

9. Suitable for small powerrequirements

10. Occupies less space per unitpower

1. It consists of moving blades andfixed blades

2. Steam passes over the movingblades with pressure and kineticenergy

3. Pressure in fixed blades as well asmoving blades

4. Because of small pressure drop theblade speed and steam speed areless

5. Aerofoil type blade shape

6. Power developed is considerable

7. Because of small pressure drop ineach the number of stages requireis more . Reaction turbines aremulti stage turbines only

8. Higher efficiency

9. Suitable for medium and highpower requirements

10. More space required


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POWER PLANTS The plant that produces electricity is called as

power plant

The working principle of all power plants is basedon First Law of Thermodynamics and Second Law

of Thermodynamics As per the first law of thermodynamics the energy

can neither be created nor it can be destroyed, butit can be converted from one form to the other

The second law of thermodynamics states that theheat flows from body as high temperature to thebody at low lower temperature.


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POWER PLANTS STEAM ( THERMAL)

HYDEL

NUCLEAR

GAS TURBINE

COMBINED CYCLE

SOLAR

WIND

TIDAL

GEOTHERMAL


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A generating station which converts heatenergy of coal combustion in to electrical

energy is known as Thermal power plant or

Steam power plant


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ADVANTAGES

The fuel used is quite cheap.

Less initial cost as compared to other generating plants.

It can be installed at any place irrespective of theexistence of coal. The coal can be transported to thesite of the plant by rail or road.

It require less space as compared to Hydro power

plants. Cost of generation is less than that of diesel power

plants.

DISADVANTAGES

It pollutes the atmosphere due to production of largeamount of smoke and fumes.

It is costlier in running cost as compared to Hydroelectric plants.

STEAM TURBINE TO PRODUCE ELECTRICITY


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R. Shanthini 15Aug 2010

STEAM TURBINE TO PRODUCE ELECTRICITY

Oil could be used

instead of coal.

Steam engines are also used to power the train.

Steam Turbine Power Plant


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C

saturatedwater

Gen

compressedwater

superheatedsteam

cooling water

(WST)out

PumpSteamTurbine

Condenser

Steam Generator

Steam Turbine Power Plant

saturatedsteam

(QSG)in

hot gases

Heat Loss

WP in

Heat Loss


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HYDRO POWER PLANT


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HYDRO POWER PLANT


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How Hydropower Works

Water from the reservoir

flows due to gravity to

drive the turbine. Turbine is connected to a

generator.

Power generated is

transmitted over power

lines.


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How Hydropower Works (2)

A water turbine that cover the energy of flowing

or falling water into mechanical energy that

drives a generator, which generates electrical

power. This is a heart of hydropower power plant.

A control mechanism to provide stable electrical

power. It is called governor.

Electrical transmission line to deliver the power

to its destination.


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Sizes of Hydropower Plants

Pico hydroelectric plant

Up to 10kW, remote areas away from the grid

Micro hydroelectric plant

Capacity 10kW to 300kW, usually provided power for smallcommunity or rural industry in remote areas away from the

grid Small hydroelectric plant

Capacity 300kW to 1MW

Mini hydroelectric plant

Capacity above 1MW

Medium hydroelectric plant

15 - 100 MW usually feeding a grid

Large hydroelectric plant

More than 100 MW feeding into a large electricity grid


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Potential

Energy

Kinetic

Energy

Electrical

Energy

Mechanical

Energy

Electricity


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Gas Turbine Power Plant


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Comp-ressor

air

CombustionChamber

fuel

GasTurbine

gasesto thestack

Gen

compressedair

hotgases

Gas Turbine Power Plant

Gas Turbine to produce Electricity


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R. Shanthini 15Aug 2010

Gas Turbine to produce Electricity


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Gas turbine power plant

Gas turbine:

Working principle :

Air is compressed(squeezed) to high

pressure by a fan-like device called the

compressor.

Then fuel and compressed air are mixed

in a combustion chamber and ignited.

Hot gases are given off, which spin the

turbine wheels.

Most of the

turbinespower runs thecompressor. Part of it drives the

generator/machinery.

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Gas turbine:

Description:

Gas turbines burn fuels such as oil,nature gas and pulverised(powdered)

coal. Instead of using the heat to produce

steam, as in steam turbines, gas turbines

use the hot gases directly to turn the

turbine blades.

Gas turbines have three main parts:

i) Air compressor

ii) Combustion chamber

iii) Turbine



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Gas turbine:

Air compressor:

The air compressor and turbine are

mounted at either end on a common

horizontal axle(shaft), with the

combustion chamber between them.

Gas turbines are not self starting. A

starting motor initially drives the

compressor till the first combustion of

fuel takes place, later, part of the

turbines power runs the compressor.

The air compressor sucks in air andcompresses it, thereby increasing its

pressure.


G bi l


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Gas turbine:

Combustion chamber:

In the combustion chamber, the

compressed air combines with fuel and

the resulting mixture is burnt.

The greater the pressure of air, the better

the fuel air mixture burns.

Modern gas turbines usually use liquid

fuel, but they may also use gaseous fuel,

natural gas or gas produced artificially

by gasification of a solid fuel.

Note :

The combination of air compressor and

combustion chamber is called as gas

generator.


G bi l


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Gas turbine:

Turbine:

o The burning gases expand rapidly and

rush into the turbine, where they cause

the turbine wheels to rotate.

o Hot gases move through a multistage gas

turbine.

o Like in steam turbine, the gas turbine

also has fixed(stationary) and

moving(rotor) blades.

o The stationary blades guide the moving

gases to the rotor blades and adjust its

velocity.

o The shaft of the turbine is coupled to a

generator or machinery to drive it.


G t bi l t


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Applications of gas turbine:

Gas turbines are used to drive pumps, compressors and high speed cars.

Used in aircraft and ships for their propulsion. They are not suitable for

automobiles because of their very high speeds.

Power generation(used for peak load and as stand-by unit).

Note :

Gas turbines run at even higher temperatures than steam turbines, the

temperature may be as high as 1100 12600C.

The thermal efficiency of gas turbine made of metal components do not

exceed 36%. Research is underway to use ceramic components at turbine inlet

temperature of 13500C or more, and reach thermal efficiencies over 40% in a

300 kW unit.



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Layout of a gas turbine power plant



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Layout of gas turbine power plant

Starting motor:

Gas turbines are not self starting.They require a starting motor to

first bring the turbine to the

minimum speed called coming in

speed, for this purpose a starting

motor is required.

Low pressure compressor(LPC):

The purpose of the compressor is

to compress the air. Air from the

atmosphere is drawn into the LPCand is compressed.


Intercooler:The air after compression in the LPC is

hot. It is cooled by the intercooler. The

intercooler is circulated with cooling

water.



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High pressure compressor(HPC):

The air from the intercooler enters

the HPC where it is furthercompressed to a high pressure.

The compressed air passes

through a regenerator.

Regenerator(Heat exchanger):

The air entering the combustion

chamber(CC) for combustion

must be hot. The heat from the

exhaust gases is picked up by the

compressed air entering thecombustion chamber.


Combustion chamber:

The fuel(natural gas, pulverized coal,

kerosene or gasoline) is injected into the

combustion chamber.The fuel gets ignited because of the

compressed air.

The fuel along with the compressed air is

ignited sometimes with a spark plug.



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High pressure compressor(HPC):

The air from the intercooler enters

the HPC where it is furthercompressed to a high pressure.

The compressed air passes

through a regenerator.

Regenerator(Heat exchanger):

The air entering the combustion

chamber(CC) for combustion

must be hot. The heat from the

exhaust gases is picked up by the

compressed air entering thecombustion chamber.


Combustion chamber:

The fuel(natural gas, pulverized coal,

kerosene or gasoline) is injected into the

combustion chamber.The fuel gets ignited because of the

compressed air.

The fuel along with the compressed air is

ignited sometimes with a spark plug.



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High pressure turbine (HPT):

In the beginning the startingmotor runs the compressor shaft.

The hot gases(products ofcombustion) expands through thehigh pressure turbine.

It is important to note that whenthe HPT shaft rotates it infact

drives the compressor shaft whichis coupled to it. Now the HPTruns the compressor and thestarting motor is stopped.

Note :

About 66% of the powerdeveloped by the gas turbine

power plant is used to run thecompressor.


Only 34% of the power developed by the

plant is used to generate electric power.



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Low pressure turbine (LPT):

The purpose of the LPT is to

produce electric power. The shaft of the LPT is directly

coupled with the generator for

producing electricity.

The hot gases(products of

combustion) after leaving theHPT is again sent to a combustion

chamber where it further

undergoes combustion.

The exhaust gases after leaving

the LPT passes through theregenerator before being

exhausted through the chimney

into the atmosphere.


The heat from the hot gases is used to

preheat the air entering the combustionchamber. This preheating of the air

improves the efficiency of the combustion

chamber.



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Advantages of gas turbine power plant : Storage of fuel requires less area and handling is easy.

The cost of maintenance is less.

It is simple in construction. There is no need for boiler, condenser and otheraccessories as in the case of steam power plants.

Cheaper fuel such as kerosene , paraffin, benzene and powdered coal can

be used which are cheaper than petrol and diesel.

Gas turbine plants can be used in water scarcity areas.

Less pollution and less water is required.

Disadvantages of gas turbine power plant : 66% of the power developed is used to drive the compressor. Therefore

the gas turbine unit has a low thermal efficiency.

The running speed of gas turbine is in the range of (40,000 to 100,000

rpm) and the operating temperature is as high as 1100 12600C. For this

reason special metals and alloys have to be used for the various parts ofthe turbine.

High frequency noise from the compressor is objectionable.


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NUCLEAR POWER PLANTS

PRESSURISED WATER REACTOR ( PWR) BOILING WATER REACTOR ( BWR)

NUCLEAR REACTOR


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NUCLEAR REACTOR

A nuclear reactor is a device in which nuclear chain

reactions are initiated, controlled, and sustained at a

steady rate, as opposed to a nuclear bomb, in which

the chain reaction occurs in a fraction of a second and

is uncontrolled causing an explosion.


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U235+ n fission + 2 or 3 n + 200 MeV

If each neutron releases two more neutrons, then the

number of fissions doubles each generation. In that case, in

10 generations there are 1,024 fissions and in 80 generations

about 6 x 10 23 (a mole) fissions.


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Outline of BWR Power Plant

Nuclear Power Plant to produce Electricity


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R. Shanthini 15

Aug 2010


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COMBINED CYCLE GAS TURBINE

POWER PLANT ( GAS AND THERMAL )

TOPPING CYCLIC

BOTTOM CYCLIC


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R. Shanthini 15

Aug 2010

Gas

Turbine (GT)

Steam

Turbine

(ST)

Combined

Power Plant

(GT & ST)

Steam / Gas

entry

Steam / Gas

outlet


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Auto (Self) Ignition Temperature

Ignition

combustion

2002 John Wiley & Sons, Inc.

M. P. Groover, Fundamentalsof Modern Manufacturing 2/e

IC E i


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IC Engine

4S and 2S engines

CI and SI engines

Gasoline (Otto) engine

Spark ignition

Compresses air-fuel mixture

Diesel engine

Compressed ignition

Compresses air only


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Compression ratio

Scavanging




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Comparison (power, efficiency and pollutants)




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Four stroke cycle theory

Each stroke takes 180 of crankshaft rotation

to complete

All cylinders fire in 720 of crankshaft rotation

720 divided by number of cylinders = firing interval

Odd fire V-6 engine (90 block with 120 rod

journals)

F k di l h


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Four stroke diesel theory

Compression ignitionUses high compression ratios instead of

spark plugs

Engine components are more robust

Diesel fuel low has volatility

F t k di l th


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Indirect Injection

Indirect injection begins in a pre-chamber

Initial combustion takes place there

Slows the rate of combustion to reduce

noise Glow plugs are needed to provide heat

F t k di l th


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Direct Injection

Fuel is injected directly into cylinder

The piston has a chamber built into it

More reliable than indirect

More noisy than indirect

Di l f l


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Diesel fuels

Cetane volatility numbers 50-55Higher cetane #1 fuel for cold weather

Lower cetane #2 fuel for warm weather

Paraffin separates from fuel at 20F

F t k di l th


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Diesel advantages

Higher engine torque

Better fuel economy

Long engine life

Engine noise

Diesel disadvantages

Exhaust smell

Hard start

cold Heavier

Fuel availability

V l t


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Valve events

Intake valve openingBTDC

Low pressure in cylinder

Intake valve closing

ABDCCylinder pressure is effected by timing

Exhaust valve opening

BBDC

Residual pressure helps blowdownExhaust valve closing

ATDC

Low pressure in exhaust port draws air in

Eff t l ti i


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Effects on valve timing

Intake valve openingLate Reduced VE

Early Dilution of intake with exhaust

Intake valve closing

Late Reduces cylinder pressureEarly Increases cylinder pressure

Exhaust valve opening

Late Pumping losses

Early Power reductionExhaust valve closing

Late Reduces vacuum

Early Reduces VE

C b ti


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Combustion

Spark ignitionMaximum cylinder pressure 15 ATDC

Tumble and swirl

Motion reduces misfires

Excess motion inhibits flowAFR 14.7:1 at part throttle, 12.5:1 under load

Compression ignition

18:1 direct injection23:1 pre-chambers for better starting

Compression heats to 800-1200 F

Fo r stroke diesel theor


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Combustion

Ignition is delayedafter fuel is injected

Rapidcombustion when fuel 1st starts to

burn Cylinder pressure rises quickly

Engine knock (almost always

detonating) Control led combustion as injection

continues

Piston dwell time


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Piston dwell time

Piston travel is at a minimum. . .

TDC and BDC

Crank moves horizontallyPiston velocity

Maximum when rod is 90 to crank

Acceleration

Maximum 30 earlierBest VE is obtained by synchronizing valve opening

with piston speeds

Other engine cycles


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Other engine cycles

Overlap

Both valves are open

End of exhaust & start of intakeLow pressure in exhaust port

Blowdown

Exhaust valve opens before BDC

To help evacuate cylinder before piston revers

Pumping losses at end of exhaust stroke


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Simple Carburettor Fuel

System for a PistonEngine

WHERE ARE THE FUEL TANKS IN AIRCRAFT?


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IN THE OTHERWISE EMPTY WING SECTIONS

CI30

HERCULES

PISTON ENGINE Carburettor Fuel System - Aircraft Tanks


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We are now going to look at how the carburettor controls the flow to the engine

THE FLOAT CHAMBER

This is done by the: -


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SIMPLIFIED PISTON ENGINE FUEL SYSTEM

FLOAT CHAMBER

NEEDLE VALVE AIR VENTVENTURI

FUEL

FEED

FUEL

NOZZLE

SIMPLIFIED PISTON ENGINE FUEL SYSTEM

FLOAT

FUEL

LEVEL

AIR IS SUCKED THROUGH VENTURI BY..

AIR/FUEL

MIXTURE

FLOWS TO


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A PISTON MOVING DOWN ON INDUCTION STROKE

SIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEMSIMPLIFIED PISTON ENGINE FUEL SYSTEM

MOVING AIR HAS LOWER PRESSURE

FUELFLOWA

IR

FLOW

AIR

FLOW

THE LOWER AIR PRESSURE PULLS FUEL THROUGH THE JET

ENGINE

FUEL LEVEL DROPS


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We now need to look at controlling the air/fuel mixture flowing into the engine

THE THROTTLE

Controlling the air/fuel mixture means controlling the engine

The carburettor part which controls the flow is.

Carburetion


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Carburetors were the predominant method used

to meter fuel on gasoline engines before the

widespread use of fuel injection. A variety of

injection systems have existed since the earliest

usage of the internal combustion engine.

Fuel Injection


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Fuel injection is a system which is replacedby carburetors in an internal combustion

engines.

The primary difference betweencarburetors and fuel injection is that fuel

injection atomizes the fuel by forcibly

pumping it through a small nozzle under

high pressure, while a carburetor relies on

low pressure created by intake air rushing

through it to add the fuel to the airstream.2002 John Wiley & Sons, Inc.

M. P. Groover, Fundamentals

of Modern Manufacturing 2/e

Objectives


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j

1. Meter - the appropriate quantity of fuel, as demanded

(speed and the load on the engine)

2. Distribute - the metered fuel equally among cylinders in a multi-cylinder engine.

3. Inject the fuel at the correct time (with respect to crank angle)

4. Inject the fuel at the correct rate (per unit time or crank angledegree).

5. Inject the fuel with the correct spray pattern and sufficient

atomization as demanded by the design of the combustionchamber

6. Begin and end injection sharply without dribbling or afterinjection.


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Pintle nozzle

Hole type


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Pintaux Pintle auxiliary


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Injector


M. P. Groover, Fundamentals

of Modern Manufacturing 2/e

CRDI (Common Rail Diesel


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Injection)

Common rail - common fuel rail/pressure resv. Robert Huber ofSwitzerland 1960

Engine control unit (ECU) which opens each

injector electronically rather mechanically

Robert Bosch , Delphi Systems, Denso

Corporation

Brand name

CRDe / DICOR /

Multijet / DDiS
http://en.wikipedia.org/wiki/Switzerlandhttp://en.wikipedia.org/wiki/Engine_control_unithttp://en.wikipedia.org/wiki/Robert_Bosch_GmbHhttp://en.wikipedia.org/wiki/Delphi_Automotive_Systemshttp://en.wikipedia.org/wiki/Denso_Corporationhttp://en.wikipedia.org/wiki/Denso_Corporationhttp://en.wikipedia.org/wiki/Denso_Corporationhttp://en.wikipedia.org/wiki/Denso_Corporationhttp://en.wikipedia.org/wiki/Delphi_Automotive_Systemshttp://en.wikipedia.org/wiki/Robert_Bosch_GmbHhttp://en.wikipedia.org/wiki/Engine_control_unithttp://en.wikipedia.org/wiki/Switzerland


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Sub functions of a CRFI system

Low pressure circuit High pressure circuit ECU with sensors

COMMON RAIL FUEL INJECTION SYSTEM


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COMMON RAIL FUEL INJECTION SYSTEM


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SUMMARY

1. The basic functional groups: Low pressure

circuit , high pressure circuit ECU and sensors.

2. In the low

pressure circuit, the fuel is cleaned bya filter and then transported to the high pressure

circuit

3. Maximum pressure of 1,350 bar is generated in

the accumulator (Rail), maintained at a constantlevel , and the fuel is taken - every time an injection

takes place.

4. The ECU controls and monitors the complete

MPFI - Multi Point Fuel Injection


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(Direct Injection)

Each cylinder has number of injectors tosupply/spray fuel in the cylinders in contrast

to one injector located centrally to

supply/spray fuel in case of single pointinjection system.


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Stage 1

Stage 2

Stage 3 Stage 4

MPFI - Advantages


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MPFI Advantages

More uniform A/F mixture will be supplied to each cylinder,hence the difference in power developed in each cylinder is

minimum

No need to crank the engine twice or thrice in case of cold

starting Immediate response, in case of sudden acceleration /

deceleration

More accurate amount of A/F mixture will be supplied and as

a result complete combustion will take place

MPFI


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MPFI

For Fuel Injection MPFI (Multi Point FuelInjection System) Used in Petrol cars In Hero

Honda Glamour electronic fuel injection (EFI),

unit is used which is Electronically Regulatedthe Air Fuel Ratio.

Ignition Parts
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BATTERY provides power for system.

IGNITION SWITCH allows driver to turn ignition on and off.

IGNITION COIL changes battery voltage to 30,000V during

normal operation and has a potential to produce up to 60,000V.

SWITCHING DEVICE mechanical or electronic switch that operates

Ignition coil(Pick-up coil, Crank sensor, Cam sensor).

SPARK PLUG uses high voltage from ignition coil to produce an arcin the combustion chamber.

IGNITION SYSTEM WIRES connect components.

Ignition CircuitsPRIMARY CIRCUIT
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PRIMARY CIRCUIT

Includes all the components

working on low voltage(Battery,Alternator).

SECONDARY CIRCUIT

Consists of wires and points

between coil out-put and the

spark plug ground.

Ignition Coil


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Primary Windings are made up of several

hundred turns of heavy wire wrapped around

or near the secondary windings.

Secondary Windings consist of several thousand

turns of very fine wire, located inside or near

the secondary windings.

Distributor


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Actuates the on/off cycle of current flow through the ignition coilprimary windings.

It distributes the coils high voltage to the plugs wires.

Functions of Lubricants


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Lubrication, thus reducing friction

Cools various engine parts

Seals the combustion chamber

Cleans the engine

Aids in preventing corrosion

Serves as a cushion between impacting parts


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Pressure Lubrication


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In a pressure lubrication system, a mechanicalpump supplies oil under pressure to the

bearings

Oil flows into the inlet of the pump throughthe pump and into an oil manifold which

distributes it to the crankshaft bearings


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Splash Lubrication and

C bi ti S t


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Combination Systems

Although pressure lubrication is the principlemethod of lubrication on all aircraft engines,

some engines use splash lubrication also

Splash lubrication is never used by itself All lubrication systems are pressure systems or

combination pressure/splash systems


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Reduces strength of materials


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Reduces strength of materials

used in piston and piston rings Unusual expansion of engine

parts

Decomposition of lubricants Burning of valves and valve seats

Pre ignition of spark plugs

Reduction of efficiency of engine


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DIRECT OR

AIR COOLING

INDIRECT OR

WATERCOOLING


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Direct method of cooling


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Direct method of cooling

Metallic fins are provided on theoutside surface of the cylinder

Fins:

Fixed to cylinder block Height:2-5cms

Increases heat tranfer surface by 5

to 10 times of original value


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Used widely in small engines like scooters

and motor cycle engines Light weight, hence used in aircraft

engines

Coolant is not required

This system can be used in cold climates,where if water is used it may freeze.

Comparatively it is less efficient


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Types of Water CoolingSystem


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System

There are two types of water cooling system :

Thermo Siphon System

In this system the circulation of water is due to

difference in temperature (i.e. difference in densities) of water. So in this

system pump is not required but water is circulated because of density

difference only.

Pump Circulation System


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In this system circulation of water is obtained by a pump. This pump is

driven by means of engine output shaft through V-belts.


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Uniform cooling of cylinder, cylinder head and valves.

If we employ water cooling system,then engine need not be provided at the

front end of moving vehicle.

Engine is less noisy as compared with air cooled engines,

as it has water for damping noise

If the water cooling system fails then it will

result in severe damage of engine. The water cooling system is costlier as it has

more number of parts. Also it requires more

maintenance and care for its parts.

S.NO FACTOR AIR COOLING WATER COOLING1 METHOD DIRECT INDIRECT

2 DESIGN SIMPLE AND COSTLY COMPLICATED AND


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2 DESIGN SIMPLE AND COSTLY COMPLICATED AND

COSTLIER

3 COOLANT DOES NOT NEED ACOOLANT WATER IS THE COOLANT

4 LEAKAGE NIL PROBABILITY IS MORE

5 INSTALLATION EASY DIFFICULT

6 WORKING SMOOTH WORKING,CAN

WITHSTAND TO CERTAIN

DEGREE OF DAMAGE

CANNOT WITHSTAND ANY

DAMAGE IN THE SETUP

7 MAINTANENCE EASY DIFFICULT

8 USES SCOOTERS,AIRCRAFTENGINES

CARS,TRUCKS,BUSSES

9 COOLING NON UNIFORM UNIFORM

10 HEAT

TRANSFER

LESS 350 TIMES OF AIR COOLING

SYSTEM

COMPONENTSLETS GET THESE IN OUR NOTES UNDER LIQUID COOLING


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WATER JACKETS

PASSAGES MADE (CAST) INTO CYLINDER BLOCKS AND

HEADS

SPACES WHERE COOLANT FLOWS

CAUSES COOLANT TO FLOW

USUALLY DRIVEN BY BELT FROM CRANK

WATER PUMP


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USUALLY DRIVEN BY BELT FROM CRANK

SHAFT SUPPORTED BY BEARNING

SEAL PREVENTS COOLANT LEAKAGE

WEEP HOLE TO PREVENT LEAKING COOLANT AWAY FROM BEARING

OVER TIGHTING BELT WILL CAUSE BEARING FAILURE

UNDER TIGHTING WILL CAUSE BELT SLIPAGE


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UNDER TIGHTING WILL CAUSE BELT SLIPAGE

ENGINE OVER HEAT WILL RESULT

BELT FAILURE WILL RESULT

RADIATORS


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Documents

Basic Mech