basic mech
TRANSCRIPT
-
7/29/2019 Basic Mech
1/146
SASTRA UNIVERSITY
SCHOOL OF MECHANICAL
ENGINEERING
BASIC MECHANICAL
ENGINEERING
-
7/29/2019 Basic Mech
2/146
BOILERS
-
7/29/2019 Basic Mech
3/146
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.
-
7/29/2019 Basic Mech
4/146
-
7/29/2019 Basic Mech
5/146
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
-
7/29/2019 Basic Mech
6/146
-
7/29/2019 Basic Mech
7/146
BOILERS
BABCOCK AND WILCOX BOILER
La MONT BOILEER
BENSON BOILER
-
7/29/2019 Basic Mech
8/146
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
-
7/29/2019 Basic Mech
9/146
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%
-
7/29/2019 Basic Mech
10/146
BABCOCK AND WILCOX BOILER
-
7/29/2019 Basic Mech
11/146
La-M0NT BOILER
Feed tankEconomizer
Radiant evaporator
Convection evaporatorConvection superheater
Steam outlet
Capacity50000kg/hr , 170 bar , 5000C
-
7/29/2019 Basic Mech
12/146
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.
-
7/29/2019 Basic Mech
13/146
BENSON BOILER
Feed tank
Economizer
Radiant evaporator
Convection evaporator
Convection superheater
Steam outlet Capacity
150000kg/hr , 200 bar , 6500C
-
7/29/2019 Basic Mech
14/146
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
-
7/29/2019 Basic Mech
15/146
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
-
7/29/2019 Basic Mech
16/146
TURBINES
-
7/29/2019 Basic Mech
17/146
Turbine is also called as a prime mover
-
7/29/2019 Basic Mech
18/146
A turbine is a rotary engine that extracts
energy from a fluid flow and converts it into
useful work.
-
7/29/2019 Basic Mech
19/146
The main components of an turbines are:
Nozzle
shaft
disc with curved blades fixed on its periphery
casing
-
7/29/2019 Basic Mech
20/146
-
7/29/2019 Basic Mech
21/146
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)
-
7/29/2019 Basic Mech
22/146
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.
-
7/29/2019 Basic Mech
23/146
IMPULSE TURBINE
De- Lavalturbine
-
7/29/2019 Basic Mech
24/146
Impulse Stage
-
7/29/2019 Basic Mech
25/146
P
R
E
SS
U
R
E
C
O
M
P
O
UN
D
I
N
G
IMPULSE TURBINE
-
7/29/2019 Basic Mech
26/146
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.
-
7/29/2019 Basic Mech
27/146
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.
-
7/29/2019 Basic Mech
28/146
REACTION TURBINE
-
7/29/2019 Basic Mech
29/146
Reaction Turbine
http://www.techhairball.com/engineering/mechanical-engineering/1522-compounding-methods -
7/29/2019 Basic Mech
30/146
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 -
7/29/2019 Basic Mech
31/146
VELOCITY COMPOUNDING
-
7/29/2019 Basic Mech
32/146
Velocity-compounded Stage
-
7/29/2019 Basic Mech
33/146
Pressure-compounded Stage
-
7/29/2019 Basic Mech
34/146
P
R
E
SS
U
R
E
C
O
M
P
O
UN
D
I
N
G
IMPULSE TURBINE
-
7/29/2019 Basic Mech
35/146
Pressure-velocity Compounded Turbine
-
7/29/2019 Basic Mech
36/146
http://www.awazpost.com/turbine-stages/88650/pressure/ -
7/29/2019 Basic Mech
37/146
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.
-
7/29/2019 Basic Mech
38/146
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
-
7/29/2019 Basic Mech
39/146
-
7/29/2019 Basic Mech
40/146
-
7/29/2019 Basic Mech
41/146
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.
-
7/29/2019 Basic Mech
42/146
POWER PLANTS STEAM ( THERMAL)
HYDEL
NUCLEAR
GAS TURBINE
COMBINED CYCLE
SOLAR
WIND
TIDAL
GEOTHERMAL
-
7/29/2019 Basic Mech
43/146
-
7/29/2019 Basic Mech
44/146
A generating station which converts heatenergy of coal combustion in to electrical
energy is known as Thermal power plant or
Steam power plant
-
7/29/2019 Basic Mech
45/146
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
-
7/29/2019 Basic Mech
46/146
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
-
7/29/2019 Basic Mech
47/146
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
-
7/29/2019 Basic Mech
48/146
HYDRO POWER PLANT
-
7/29/2019 Basic Mech
49/146
HYDRO POWER PLANT
-
7/29/2019 Basic Mech
50/146
-
7/29/2019 Basic Mech
51/146
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.
-
7/29/2019 Basic Mech
52/146
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.
-
7/29/2019 Basic Mech
53/146
-
7/29/2019 Basic Mech
54/146
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
-
7/29/2019 Basic Mech
55/146
Potential
Energy
Kinetic
Energy
Electrical
Energy
Mechanical
Energy
Electricity
-
7/29/2019 Basic Mech
56/146
Gas Turbine Power Plant
-
7/29/2019 Basic Mech
57/146
Comp-ressor
air
CombustionChamber
fuel
GasTurbine
gasesto thestack
Gen
compressedair
hotgases
Gas Turbine Power Plant
Gas Turbine to produce Electricity
-
7/29/2019 Basic Mech
58/146
R. Shanthini 15Aug 2010
Gas Turbine to produce Electricity
-
7/29/2019 Basic Mech
59/146
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.
24 September 2013 59
-
7/29/2019 Basic Mech
60/146
Gas turbine power plant
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
24 September 2013 60
-
7/29/2019 Basic Mech
61/146
Gas turbine power plant
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.
24 September 2013 61
G bi l
-
7/29/2019 Basic Mech
62/146
Gas turbine power plant
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.
24 September 2013 62
G bi l
-
7/29/2019 Basic Mech
63/146
Gas turbine power plant
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.
24 September 2013 63
G t bi l t
-
7/29/2019 Basic Mech
64/146
Gas turbine power plant
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.
24 September 2013 64
-
7/29/2019 Basic Mech
65/146
Layout of a gas turbine power plant
24 September 2013 65
-
7/29/2019 Basic Mech
66/146
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.
24 September 2013 66
Intercooler:The air after compression in the LPC is
hot. It is cooled by the intercooler. The
intercooler is circulated with cooling
water.
Layout of gas turbine power plant
-
7/29/2019 Basic Mech
67/146
Layout of gas turbine power plant
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.
24 September 2013 67
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.
Layout of gas turbine power plant
-
7/29/2019 Basic Mech
68/146
Layout of gas turbine power plant
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.
24 September 2013 68
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.
Layout of gas turbine power plant
-
7/29/2019 Basic Mech
69/146
Layout of gas turbine power plant
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.
24 September 2013 69
Only 34% of the power developed by the
plant is used to generate electric power.
Layout of gas turbine power plant
-
7/29/2019 Basic Mech
70/146
Layout of gas turbine power plant
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.
24 September 2013 70
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.
Gas turbine power plant
-
7/29/2019 Basic Mech
71/146
Gas turbine power plant
24 September 2013 71
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.
-
7/29/2019 Basic Mech
72/146
NUCLEAR POWER PLANTS
PRESSURISED WATER REACTOR ( PWR) BOILING WATER REACTOR ( BWR)
NUCLEAR REACTOR
-
7/29/2019 Basic Mech
73/146
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.
-
7/29/2019 Basic Mech
74/146
-
7/29/2019 Basic Mech
75/146
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.
-
7/29/2019 Basic Mech
76/146
Outline of BWR Power Plant
Nuclear Power Plant to produce Electricity
-
7/29/2019 Basic Mech
77/146
R. Shanthini 15
Aug 2010
-
7/29/2019 Basic Mech
78/146
-
7/29/2019 Basic Mech
79/146
COMBINED CYCLE GAS TURBINE
POWER PLANT ( GAS AND THERMAL )
TOPPING CYCLIC
BOTTOM CYCLIC
-
7/29/2019 Basic Mech
80/146
-
7/29/2019 Basic Mech
81/146
R. Shanthini 15
Aug 2010
Gas
Turbine (GT)
Steam
Turbine
(ST)
Combined
Power Plant
(GT & ST)
Steam / Gas
entry
Steam / Gas
outlet
-
7/29/2019 Basic Mech
82/146
-
7/29/2019 Basic Mech
83/146
Auto (Self) Ignition Temperature
Ignition
combustion
2002 John Wiley & Sons, Inc.
M. P. Groover, Fundamentalsof Modern Manufacturing 2/e
IC E i
-
7/29/2019 Basic Mech
84/146
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
-
7/29/2019 Basic Mech
85/146
2002 John Wiley & Sons, Inc.
M. P. Groover, Fundamentalsof Modern Manufacturing 2/e
-
7/29/2019 Basic Mech
86/146
Compression ratio
Scavanging
2002 John Wiley & Sons, Inc.
M. P. Groover, Fundamentalsof Modern Manufacturing 2/e
-
7/29/2019 Basic Mech
87/146
Comparison (power, efficiency and pollutants)
2002 John Wiley & Sons, Inc.
M. P. Groover, Fundamentalsof Modern Manufacturing 2/e
-
7/29/2019 Basic Mech
88/146
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
-
7/29/2019 Basic Mech
89/146
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
-
7/29/2019 Basic Mech
90/146
Four stroke diesel theory
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
-
7/29/2019 Basic Mech
91/146
Four stroke diesel theory
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
-
7/29/2019 Basic Mech
92/146
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
-
7/29/2019 Basic Mech
93/146
Four stroke diesel theory
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
-
7/29/2019 Basic Mech
94/146
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
-
7/29/2019 Basic Mech
95/146
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
-
7/29/2019 Basic Mech
96/146
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
-
7/29/2019 Basic Mech
97/146
Four stroke diesel theory
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
-
7/29/2019 Basic Mech
98/146
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
-
7/29/2019 Basic Mech
99/146
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
-
7/29/2019 Basic Mech
100/146
Simple Carburettor Fuel
System for a PistonEngine
WHERE ARE THE FUEL TANKS IN AIRCRAFT?
-
7/29/2019 Basic Mech
101/146
IN THE OTHERWISE EMPTY WING SECTIONS
CI30
HERCULES
PISTON ENGINE Carburettor Fuel System - Aircraft Tanks
-
7/29/2019 Basic Mech
102/146
We are now going to look at how the carburettor controls the flow to the engine
THE FLOAT CHAMBER
This is done by the: -
-
7/29/2019 Basic Mech
103/146
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
-
7/29/2019 Basic Mech
104/146
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
-
7/29/2019 Basic Mech
105/146
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
-
7/29/2019 Basic Mech
106/146
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
-
7/29/2019 Basic Mech
107/146
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
-
7/29/2019 Basic Mech
108/146
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.
-
7/29/2019 Basic Mech
109/146
-
7/29/2019 Basic Mech
110/146
Pintle nozzle
Hole type
-
7/29/2019 Basic Mech
111/146
Pintaux Pintle auxiliary
-
7/29/2019 Basic Mech
112/146
Injector
2002 John Wiley & Sons, Inc.
M. P. Groover, Fundamentals
of Modern Manufacturing 2/e
CRDI (Common Rail Diesel
-
7/29/2019 Basic Mech
113/146
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 -
7/29/2019 Basic Mech
114/146
Sub functions of a CRFI system
Low pressure circuit High pressure circuit ECU with sensors
COMMON RAIL FUEL INJECTION SYSTEM
-
7/29/2019 Basic Mech
115/146
COMMON RAIL FUEL INJECTION SYSTEM
-
7/29/2019 Basic Mech
116/146
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
-
7/29/2019 Basic Mech
117/146
(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.
-
7/29/2019 Basic Mech
118/146
Stage 1
Stage 2
Stage 3 Stage 4
MPFI - Advantages
-
7/29/2019 Basic Mech
119/146
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
-
7/29/2019 Basic Mech
120/146
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
http://images.google.com/imgres?imgurl=http://www.acdelco.com/i/parts/battery/sidebar/hd_heavy_duty.jpg&imgrefurl=http://www.acdelco.com/parts/battery/heavy-duty-battery.htm&h=245&w=282&sz=23&hl=en&start=4&tbnid=IiXp-5Fuc_kqSM:&tbnh=99&tbnw=114&prev=/images%3Fq%3Dbattery%26svnum%3D10%26hl%3Den%26rlz%3D1T4GFRC_enCA204CA205%26sa%3DN -
7/29/2019 Basic Mech
121/146
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
http://images.google.com/imgres?imgurl=http://www.quantumcars.co.uk/res/user/111_spark-plug.jpg&imgrefurl=http://www.quantumcars.co.uk/products/ignition/&h=666&w=1000&sz=62&hl=en&start=14&tbnid=Mb3FCmZdzfFcGM:&tbnh=99&tbnw=149&prev=/images%3Fq%3Dspark%2Bplug%26svnum%3D10%26hl%3Den%26rlz%3D1T4GFRC_enCA204CA205http://images.google.com/imgres?imgurl=http://www.ctcautoranch.com/NOS%2520Parts/Nos%2520Parts/Dist%2520Pickup%2520Coil,%2520Buick,%2520Cad,%2520Olds,%2520Chev,%2520Pontiac.JPG&imgrefurl=http://www.ctcautoranch.com/NOS%2520Parts/NOS%2520Parts.htm&h=239&w=295&sz=66&hl=en&start=1&tbnid=yo0l2EAX0p9-3M:&tbnh=93&tbnw=115&prev=/images%3Fq%3Ddistributor%2Bpick%2Bup%2Bcoil%26svnum%3D10%26hl%3Den%26rlz%3D1T4GFRC_enCA204CA205http://images.google.com/imgres?imgurl=http://www.sentex.net/~mwandel/cannon/coil.jpg&imgrefurl=http://www.sentex.net/~mwandel/cannon/sparky.html&h=288&w=154&sz=10&hl=en&start=5&tbnid=0d0CeyTV36Mr0M:&tbnh=115&tbnw=61&prev=/images%3Fq%3Dignition%2Bcoil%26svnum%3D10%26hl%3Den%26rlz%3D1T4GFRC_enCA204CA205http://images.google.com/imgres?imgurl=http://www.ronfrancis.com/images/part-pic457.jpg&imgrefurl=http://www.ronfrancis.com/synergyseries.htm&h=215&w=216&sz=16&hl=en&start=29&tbnid=zgVbS7kAur2V8M:&tbnh=107&tbnw=107&prev=/images%3Fq%3Dignition%2Bswitch%26start%3D20%26ndsp%3D20%26svnum%3D10%26hl%3Den%26rlz%3D1T4GFRC_enCA204CA205%26sa%3DNhttp://images.google.com/imgres?imgurl=http://www.acdelco.com/i/parts/battery/sidebar/hd_heavy_duty.jpg&imgrefurl=http://www.acdelco.com/parts/battery/heavy-duty-battery.htm&h=245&w=282&sz=23&hl=en&start=4&tbnid=IiXp-5Fuc_kqSM:&tbnh=99&tbnw=114&prev=/images%3Fq%3Dbattery%26svnum%3D10%26hl%3Den%26rlz%3D1T4GFRC_enCA204CA205%26sa%3DN -
7/29/2019 Basic Mech
122/146
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
-
7/29/2019 Basic Mech
123/146
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
-
7/29/2019 Basic Mech
124/146
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
-
7/29/2019 Basic Mech
125/146
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
-
7/29/2019 Basic Mech
126/146
Pressure Lubrication
-
7/29/2019 Basic Mech
127/146
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
-
7/29/2019 Basic Mech
128/146
Splash Lubrication and
C bi ti S t
-
7/29/2019 Basic Mech
129/146
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
-
7/29/2019 Basic Mech
130/146
-
7/29/2019 Basic Mech
131/146
-
7/29/2019 Basic Mech
132/146
Reduces strength of materials
-
7/29/2019 Basic Mech
133/146
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
-
7/29/2019 Basic Mech
134/146
DIRECT OR
AIR COOLING
INDIRECT OR
WATERCOOLING
-
7/29/2019 Basic Mech
135/146
Direct method of cooling
-
7/29/2019 Basic Mech
136/146
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
-
7/29/2019 Basic Mech
137/146
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
-
7/29/2019 Basic Mech
138/146
Types of Water CoolingSystem
-
7/29/2019 Basic Mech
139/146
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
-
7/29/2019 Basic Mech
140/146
In this system circulation of water is obtained by a pump. This pump is
driven by means of engine output shaft through V-belts.
-
7/29/2019 Basic Mech
141/146
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
-
7/29/2019 Basic Mech
142/146
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
-
7/29/2019 Basic Mech
143/146
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
-
7/29/2019 Basic Mech
144/146
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
-
7/29/2019 Basic Mech
145/146
UNDER TIGHTING WILL CAUSE BELT SLIPAGE
ENGINE OVER HEAT WILL RESULT
BELT FAILURE WILL RESULT
RADIATORS
-
7/29/2019 Basic Mech
146/146