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TRANSCRIPT
PPEERRFFOORRMMAANNCCEE TTEESSTTSS OONN 55HHPP DDIIEESSEELL EENNGGIINNEE WWIITTHH TTHHEERRMMAALL BBAARRRRIIEERR CCOOAATTIINNGGSS OONN PPIISSTTOONN AANNDD
IITTss AANNAALLYYSSIISS UUSSIINNGG FFEEMM
A Project Report submitted to Sri Krishna Devaraya University
in partial fulfillment of the requirements for the award of the degree of
BACHELOR OF TECHNOLOGY
IN MECHANICAL ENGINEERING
By
GG..NNAARREENNDDRRAA
HH..SSUUSSHHMMAA KK..SS..GGUURRUU CCHHAARRAANN
AA..KKOONNDDAA RREEDDDDYY BB..RRAAMMBBAABBUU
Under the guidance of
Sri V.MAHANANDI REDDY Asst. Professor
Department of Mechanical Engineering
G.PULLA REDDY ENGINEERING COLLEGE
KURNOOL – 518 002
(Affiliated to SRI KRISHNADEVARAYA UNIVERSITY, ANANTAPUR)
2005-2006
Department of Mechanical Engineering
G.PULLA REDDY ENGINEERING COLLEGE
KURNOOL - 518002
CERTIFICATE
This is to certify that this project work entitled
PPEERRFFOORRMMAANNCCEE TTEESSTTSS OONN 55HHPP DDIIEESSEELL EENNGGIINNEE WWIITTHH TTHHEERRMMAALL
BBAARRRRIIEERR CCOOAATTIINNGGSS OONN PPIISSTTOONN AANNDD IITT’’SS AANNAALLYYSSIISS UUSSIINNGG FFEEMM
is a bonafide record of work done
by
GG..NNAARREENNDDRRAA
HH..SSUUSSHHMMAA KK..SS..GGUURRUU CCHHAARRAANN
AA..KKOONNDDAA RREEDDDDYY DD..RRAAMMBBAABBUU
Under the guidance and supervision and submitted in partial fulfillment of
the requirements for the award of degree of
BACHELOR OF TECHNOLOGY
IN
MECHANICAL ENGINEERING
BY
SRI KRISHNADEVARAYA UNIVERSITY
Dr.B.SRINIVASA REDDY Sri V.MAHANANDI REDDY
Prof. & Head of the Dept. Assistant Professor & Guide
ACKNOWLEDGEMENTS
We sincerely express our gratitude to Sri B.Mahanandi Reddy, Asst. Professor in
Mechanical Engg. Dept.for his guidance and encouragement in the completion of this project
work.
We are very thankful to Dr. B. Srinivasa Reddy, Professor and Head of Mechanical
Dept. for guiding us to complete this project by providing us all the equipment in the laboratory.
We extend our thanks to Dr.P.Jayarami Reddy, Principal for giving this opportunity to
do this project work.
We are very grateful to Mr.Seshagiri Rao, the technician who has given us his
continuous support in this endeavor.
We are very much indebted to Mr.P.Sreenivasulu, Material Engineer in ARCI,
International Research Centre for Advanced Materials and Powder Metallurgy, for providing us
ceramic coatings on the piston which is crucial in our project work.
We take this occasion to express our acknowledgement to all the faculty members of
Mechanical Engineering Department and non-teaching staff for their cooperation and
encouragement throughout our graduation and to all our friends who have helped in one way or
other.
ABSTRACT
Low heat rejection engine with ceramic coated piston can be considered an effective
engine to maintain hot combustion chamber and reducing knocking tendency at the same time
allowing utilization of alcohols as an alternative fuels and increasing the efficiency and life of the
piston component. Ceramic coatings are achieved by thermal spraying techniques like powder
flame spraying and detonation spraying .The temperature distributions are obtained using
computer based FEM package named ANSYS without and with different ceramic coatings.
CHAPTER 1
INTRODUCTION
Energy conservation and efficiency have always been the quest of engineers concerned
with internal combustion engines .The diesel engine generally offers better fuel economy than its
counter part petrol engine. Even the diesel engine rejects about two thirds of the heat energy of
the fuel, one third to the coolant, and one third to the exhaust, leaving only about one third as
useful power output. Theoretically if the heat rejected could be reduced, then the thermal
efficiency would be improved, at least up to the limit set by the second law of thermodynamics.
Low Heat Rejection engines aim to do this by reducing this heat loss.
The diesel engines with its combustion chamber walls and the surface of the piston
insulated by ceramics is referred to as Low Heat Rejection engines. The insulation on the
cylinder walls reduces the heat loss to the coolant. But it is necessary to provide cooling
especially to the walls of combustion chamber since the physical and chemical changes in the
lubricating oil may also occur due to high temperatures thereby causing wear and sticking of the
piston rings, scoring of piston walls or seizure of the piston.
By providing insulation on the piston surface the heat loss through the piston to the crank
case can be reduced. Since the piston is made up of aluminum pistons, with high thermal
conductivity, the heat from the piston can be reduced by applying thermal barrier coatings like
ceramics whose thermal conductivity is less and can withstand high pressures and high
temperatures in the cylinder. These maintain high piston overhead temperatures which is
favorable for reducing knocking tendency, and to improve combustion efficiency.
HEAT EQUIVALENT TO BHP
(25-35%)
HEAT LOST TO COOLING MEDIUM
(35%)
HEAT TAKEN BY EXHAUST GASES
(20%)
UNACCOUNTED HEAT LOSSES
(20%)
HEAT SUPPLIED
PPIISSTTOONN TTEEMMPPEERRAATTUURREE DDIISSTTRRIIBBUUTTIIOONN
The piston crown is exposed to very high combustion temperatures (Figure-1) gives
the typical values of temperature at different parts of a cast iron piston. It may be noted that
the maximum temperature occurs at the centre of the crown and decreases with increasing
distance from the center. The temperature is the lowest at the bottom of the skirt. Poor design
may result in the thermal overloading of the piston outer edge and the crown. The
temperature difference between piston outer edge and the center of the crown is responsible
for the flow of heat to the ring belt through the path offered by metal section of the crown. It
is, therefore, necessary to increase the thickness of the crown from the center to the outer
edge in order to make a path of greater cross-section available for the increasing heat quality.
The length of the path should no be too long or the thickness of the crown cross-section too
small for the heat to flow. This will cause the temperature at the center of crown to build up
and thereby excessive temperature difference between the crown and the outer edge of the
piston will result. This may even lead to cracking of piston during overload operation.
Piston Temperature Distribution
Figure 1.1
THEORY OF ENGINE HEAT TRANSFER
In spite of its high temperature, the cylinder gas is a poor radiator and almost all the
heat transfer to the cylinder walls from combustion space is by convection. In order to
understand the engine heat transfer, a simple analysis can be followed for the flow of hot gases
through a pipe.
For gases in pipes it can be shown by dimensional analysis and also through experiments that
m
pn
k
CCLZ
khL
Χ
Χ=
µµρ
----------------------- (1.1)
( ) ( ) ( ) ( ) 3.08.0 PrRe023.0 Χ=µN
Where h = coefficient of heat transfer
L = any characteristic length (say stroke)
k = thermal conductivity of gases
Z = constant
ρ = mass density of gases
C = velocity of gases
CP = specific heat of gas
µ = viscosity of gas
n, m = exponents
Combustion phenomenon in CI engines Three phases of CI engine combustion In the CI engine, combustion may be considered in three district stages as shown in
Fig 1.2
1. Ignition delay period.
2. Period of rapid or uncontrolled combustion
3. Period of controlled combustion
The third phase is followed by after burning (or burning on the expansion stroke), which may
be called the fourth phase of combustion.
1. Ignition delay period: - The delay period can be roughly sub-divided in to physical
delay and chemical delay. The period of physical delay is the time between the beginning
of injection and the attainment of chemical reaction conditions. In the physical delay
period, the fuel is atomized, vaporized, mixed with air, and raised in temperature. In the
chemical delay period reaction starts slowly and then accelerates until inflammation or
ignition takes place.
Figure 1.2
2. Period of rapid or uncontrolled combustion: - The second stage of combustion in CI
engines after the delay period is the period of rapid or uncontrolled combustion. This
period is counted from the end of the delay period to the posing of maximum pressure on
the indicator diagram. In this second stage of combustion, the point of maximum pressure
is rapid because during the delay period the droplets of fuel have had time to spread
themselves out over a wide area and they have fresh air all around them. About one –third
of heat is evolved during this process.
3. Period of controlled combustion: - At the end of second stage of combustion, the
temperature and pressure, are so high that the fuel droplets injected in the third stage burn
almost as they enter and any further pressure rise can be controlled by purely mechanical
mean, i.e. by the injection rate. The period of controlled combustion is assumed to end at
maximum cycle temperature. The heat evolved by the end of controlled is about 70 to 80
per cent.
Abnormal combustion in CI engines :
“Diesel knock” occurs when the delay period id excessively long so that there is a
large amount of fuel in the cylinder for the simultaneous explosion phase. The rate of
pressure ride per degree of crank angle is then so great than an audible knocking sounds
occurs. Running is rough and if allowed to become extreme the increase in mechanical
and thermal stresses may damage the engine. Knock is thus a function of the fuel chosen
and may be avoided by choosing a fuel with characteristics that do not give too long a
delay period.
Delay Period (or Ignition Lag) in CI Engines :
In CI (compression ignition) engine, the fuel which is in atomized form is considerably
colder than the hot compressed air in the cylinder. Although the actual ignition is almost
instantaneous, an appreciable time elapses before the combustion is in full progress. This
time is occupied is called the delay period or ignition lag. It is the time immediately
following injection of the fuel during which the ignition process is being initiated and the
pressure does not rise beyond the value it would have due to compression of air.
The delay period extends for about 13o, movement of the crank. The time for which it
occurs decreases with increase in engine speed.
The delay period depends upon the following:
1. Temperature and pressure in the cylinder at the time of injection.
2. Nature of the fuel mixture strength.
3. Relative velocity between the fuel injection and air turbulence.
4. Presence of residual gases.
5. Rate of fuel injection
6. To small extent the fines of the fuel spray.
The delay period increases with load but is not much effected by injection pressure. The
delay period should be as short as possible since a long delay period gives a more rapid rise
in pressure and thus causes knocking.
CETANE NUMBER :
• The cetane rating of a diesel fuel is a measure of its ability to auto ignite quickly
when it is injected into the compressed and heated air in the engine. Though ignition
delay is affected by several engine design parameters such as compression ratio,
injection rate, injection time, inlet air temperature etc., it is also dependent on
hydrocarbon composition of the fuel and to some extent on its volatility
characteristic. The cetane number is a numerical measure of the influence the diesel
fuel has in determining the ignition delay. Higher the cetane rating of the fuel lesser is
the propensity for diesel knock.
• For higher speed engines, the cetane number required is about 50, for medium speed
engines about 40, and for slow speed engines about 30.
• Cetane number is the most impartment single fuel property, which effects the exhaust
emissions, noise start ability of a diesel engine. In general, lower the cetane numbers
higher are the hydrocarbon emissions and noise levels. Low cetane fuels increase
ignition delay so that start of cumstion is neat to top dead center. This is similar to
retarding of injection timing, which is also known to result in higher hydrocarbon
levels.
--- In general, a high octane value implies a low cetane value.
MODES OF IIEAT TRANSFER
"Heat transfer”, which is defined as the transmission of energy from one region to
another as a result of temperature gradient takes place by the following three modes.
(I) Conduction; (ii) Convection; (iii) Radiation
Heat transmission, in majority of real situations occurs as a result of combinations of
these modes of heat transfer. Example: The water in a boiler shell receives Its heat from the
fire-bed by conducted, convected and radiated heat from the shell, conducted heat through
the shell and conducted and convected heat from the inner shell wall, to the water. Heat
always flows in the direction of lower temperature.
The above three modes are similar in that a temperature differential must exist and the
heat exchange is in the direction of decreasing temperature; each method, however, has
different controlling laws.
1. Conduction: 'Conduction' is the transfer of heat from one part of a substance another
part of the same substance, or from one substance to another in physical contact with it,
without appreciable displacement of molecules forming the substance.
In solids, the heat is conducted by the following two mechanisms:
(i) By lattice vibration: The faster moving molecules or atoms in the hottest part of a body
transfer heat by impacts some of their energy to adjacent molecules.
(ii) By transport of free electrons (Free electrons provide an energy flux in the direction of
decreasing temperature – For metals, especially good electrical conductors, the
electronic mechanism is responsible for the the major portion of the heat flux except at
low temperature).
In case of gases, the mechanism of heat conduction is simple. The kinetic energy of a
molecule is a function of temperature. These molecules are in a continuous random motion
exchanging energy and momentum. When a molecule from the high temperature region collides
with a molecule from the low temperature region. It loses energy by collisions.
In liquids, the mechanism of heat is nearer to that of gases. However, molecules are more
closely spaced and intermolecular force4s come to play.
2. Convection: ‘Convection’ is the transfer of heat within a fluid by mixing of one portion of the
fluid with another.
• Convection is possible only in a fluid medium and is directly linked with the transport of
medium itself.
• Convection constitutes the macroform of the heat transfer since macroscopic particles of
a fluid moving in space cause the heat exchange.
• The effectiveness of heat transfer by convection depends largely upon the mixing motion
of the fluid.
This mode of heat transfer is met which in situations where energy is transferred as heat
to a following fluid at any surface over which flow occurs. This mode is basically conduction in
a very thin fluid layer at the surface and then mixing caused by the flow. The heat flow depends
on the properties of fluid and is independent of the properties of the material of the surface.
However, the shape of the surface will influence the flow and hence the heat transfer.
Free of natural convection: Free or natural convection occurs where the fluid circulates
by virtue of the natural differences in densities of hot and cold fluids; the denser portions of the
fluid move downward because of the greater force of gravity, as compared with the force on the
less dense.
Forced Convection: when the work is done to blow or pump the fluid, it is said to be
forced convection.
3. Radiation: ‘Radiation’ is the transfer of heat through space or matter by means other than
conduction or convection.
Radiation heat is through of as electromagnetic waves or quanta (as convenient) an
emanation of the same nature is light and radio waves. All bodies radiate heat; so a transfer of
heat by radiation occurs because hot bodies emits. Radiant energy (being electromagnetic
radiation) requires no medium for propagation and will pass through a vacuum.
LAWS GOVERNING MODES OF HEAT TRANSFER
For better understanding of the different modes of heat transfer they should be studied
individually and separately. If one particular mode for example conduction dominates
quantitatively; some useful infonnation can be obtained by initially focusing exclusively on
Conduction. With this restriction in mind a brief description of the basic laws of conduction,
convection and radiation is given in this chapter.
FOURIER'S LAW: -A physical law for heat transfer by conduction was given by Fourier
according to which the rate of heat conduction is proportional to the area easured normal to the
direction of heat flow and to the temperature Gradient in that direction. Mathematically the
equation is given as follows:
Q = -kA .dT/dn
Where Q = Heat conducted in Watts
K= Coefficient of thermal conductivity which is defined as the ability of a
substance to conduct heat, W 1m k.
A = Area measured nonnal in the direction of heat flow, m2
dt/dn = Temperature gradient in the direction nonnal to the heat flow, m-'K
NEWTON'S LAW OF COOLING: -Convection follows the Newton's law of cooling.
According to this law for a fluid flowing at ambient temperature T a over a surface at a
temperature T s, the heat convected is given by
Q= h A (Ts -Ta)
Where h = Heat transfer coefficient, W/m2 K
A= Projected area of a heating tube, m2
STEFAN BOLTZMANN LAW: -Heat transfer through radiation follows the Stefan Boltzman
law to which the radiation energy emitted by a body is proportional to the fourth power of its
absolute temperature, so heat radiated is given by
Q = σ A T4
Where Q= Heat radiated, Watts
A= Area, m2
σ = Stefan Boltzmann constant, 5.6695 * 10 -8W/m2 K4
T = Absolute Temperature, K
The basic process of heat transfer -conduction, convection and radiation are often
combined both in nature and in engineering applications. The steam generating tubes of a
boiler, for instance, receive a heat from the products of heat combustion by all the three
modes of heat transfer. Therefore, it is not actually possible to isolate entirely one mode from
interactions with the other modes. Various phase changes take place during Boiling and
Condensation. These should be accounted for, because the heat transfer rate varies because of
the phase change from liquid to vapor during boiling and vapor to liquid during
condensation. The effect of boiling heat transfer is explained in the next chapter
EXPERIMENTAL METHOD Engine Specifications: Bore : 80mm
Stroke : 110mm
BHP : 5
Compression Ratio : 16.5: 1
Radius of Dynamometer : 215mm
Efficiency of dynamometer : 0.8
Type of Loading : DC generator loading
Orifice Diameter : 2cm
Co-efficient of Discharge : 0.6
Speed of the Engine : 1500rpm
Fuel Used : Diesel
Calorific Value : 10500 kcal/kg
Specific Gravity : 0.836
Piston Material : Aluminum
Ceramics Applied : Zirconia----0.35mm
Alumina----0.25mm
DESCRIPTION:
The engineers are vertical single cylinder water-cooled compression ignition type diesel
engine. The suction side of the engine cylinder is connected to the air intake orifice tank through
which the atmospheric air is drawn into the engine cylinder. A manometer is provided to
measure the pressure. The section of cylinder is connected to an air intake tank with a three way
cock connected between water manometer .The graduated fuel gage through a three way cock is
connected between the main tank and fuel further to the fuel pump. The cylinder jacket is water-
cooled and outlet temperature can be measured by a digital thermometer .The exhaust gas is
passed through a gas calorimeter and temperature of the exhaust gas at outlet of the calorimeter
can be measured.
PRELIMINARIES:
1. Check the fuel level in the tank.
2. Check the lubricating oil level with the help of oil stick.
3. Open three way cock so that the fuel flows into the engine as well as in burette.
4. Adjust the cooling water valve so that water flows continuously.
5. Check the temperature with a standard thermometer and note if any correction.
PROCEDURE:
1. After carefully going through the preliminaries, the decompression lever is
pressed on so that there will be no trapping between the cylinder head and the
piston
2. The engine is started by rotating the crank by means of hand crank lever and by
throwing off the decompression lever at sufficient speed. The engine is allowed
and adjusted to pickup the speed and run at rated speed smoothly for few seconds
using the tachometer.
3. Find out time taken for 10cc of fuel consumption at no load.
4. Note the quantity of water running through the engine jacket at inlet and outlet
and also take the manometer difference.
5. The engine is loaded by applying the current the voltage developed is noted by
adjusting the field current after setting the load on the engine at a fixed point, the
time taken for 10cc of fuel is measured. Also note manometer difference,
6. Water flow rate in the calorimeter is kept constant.
7. Temperature of the engine jacket water at inlet and outlet of the calorimeter,
exhaust gas temperature are measured by using thermocouples.
8. The sequence repeated after several values of load for piston without ceramic
coating and for ceramic coating of Zirconia and Alumina.
Sample Calculations:
Voltage V = 207 V
Load I = 13.4 A
Manometer difference h = 5.4 cm
Time taken for 10cc fuel consumption = 31.6 sec
Temperature of exhaust gas in T1 = 389OC
Temperature of exhaust gas out T2 = 70 OC
Temperature of calorimeter water in T3 = 26 OC
Temperature of calorimeter water out T4 = 29 OC
Temperature of engine water out T5 = 37 OC
Temperature of engine water in T6 = 26 OC
Total fuel consumption TFC= (measured fuel*sp.gravity*3600)/ (time taken*1000)
= (10*0.836*3600)/ (31.6*1000)
= 0.9520 kg/hr
Brake Horse Power BHP = (V*I)/ (ηgen*746)
= (207*13.4)/ (0.8*746)
= 4.648
Specific Fuel Consumption SFC = (TFC)/ (BHP)
= 0.952/4.648
= 0.205 kg/hr-bhp
Brake Thermal Efficiency ηb = (BHP*4500*60)/ (TFC*CV*J)
= (4.648*4500*60)/ (0.952*10500*427)
= 29.4%
FHP BHP
TFC William’s Line Method
From Graph, FHP = 1.1
Indicated Horse Power = BHP+ FHP
= 4.648+1.1
= 5.748
Mechanical Efficiency ηm = BHP/IHP
= 4.648/5.748
= 80.56%
Indicated Thermal Efficiency ηi = (IHP*4500*60)/(TFC*CV*J)
= (5.748*4500*60)/(0.952*10500*427)
= 36.36%
Actual Discharge Qa = Cd*A*√(2g*h*10/ρa)
= 0.6*π/4*(0.02)2 * √(2*9.81*5.4*10/1.176)
= 5.658*10-3 m3/s
Theoretical Discharge Qt = ΠD2LNk/ (4*60)
= (Π*0.082*.11*1500*0.5)/240
= 6.939*10-3 m3/s
Volumetric Efficiency ηv = Qa/ Qt
= (5.658*10-3)/ (6.939*10-3)
= 81.55%
Mass flow rate of fuel mf = 2.644*10-4 kg/s
Mass flow rate of air ma = 6.836*10-3 kg/s
Mass flow rate of exhaust mg = 7.090*10-3 kg/s
Air Fuel Ratio A/F = ma/ mf
= 25.84
Preparation of heat balance sheet:
Heat supplied = mf* CVdiesel
= 2.644*10-4 *43000
= 11377.8 J/s
Heat Equivalent to BHP = BHP*746
= 3467.8 J/s
Heat given to cooling water = mw (cooling)*Cpw*(T5-T6)
= 3265.4 J/s
Heat taken away by exhaust gases = mw (calorimeter)*Cpw*(T4-T5) +mg*Cpg*(T1-T2)
= 2043.0 J/s
Unaccounted heat losses = 2602.0 J/s
• WITHOUT CERAMIC DIESEL:- Speed (N) = 1500rpm, mw (cooling) = 0.0709kg/sec, mw(calorimeter) = 0.1389kg/sec
V
I
TFC
BSFC
A/F
BHP
FHP
IHP
ηb
ηv
ηi
ηm
258
236
226
217
207
199
193
2.1
5.2
8.3
11.0
13.4
15.8
17.2
0.542
0.634
0.772
0.853
0.952
1.063
1.131
0.597
0.308
0.246
0.213
0.205
0.202
0.203
45.39
38.84
31.88
28.87
25.84
23.14
21.75
0.908
2.056
3.143
4.000
4.648
5.268
5.562
1.1
1.1
1.1
1.1
1.1
1. 1
1.1
2.008
3.156
4.243
5.100
5.748
6.368
6.662
10.09
19.53
24.52
28.24
29.40
29.84
29.62
83.78
83.04
83.04
82.29
81.55
80.78
80.78
22.31
29.98
33.10
36.00
36.36
36.08
35.47
45.22
65.15
74.07
78.43
80.56
82.73
83.49
• HEAT BALANCE SHEET:-
Heat supplied
BHP
Heat carried away
By cooling water
Heat carried away
By exhaust gases
Unaccounted
Heat losses
(J/S) (J/S) %ge (J/S) %ge (J/S) %ge (J/S) %ge
6475.8
7568.0
9219.2
10182.4
11377.8
12702.2
13514.9
677.4
1533.8
2344.7
2984.0
3467.4
3929.9
4149.3
10.46
20.27
25.43
29.30
30.48
30.94
30.70
1781.1
2078.0
2671.7
2968.6
3265.4
3562.43
3859.2
27.80
27.46
28.98
29.15
28.70
28.04
28.56
1281.9
1317.4
1367.6
1992.3
2043.0
2668.6
2705.2
19.80
17.40
14.80
19.57
17.96
21.00
20.02
2735.4
2638.8
2835.2
2287.5
2602.0
2541.2
2801.2
42.24
34.86
30.79
21.98
22.86
20.02
20.72
• WITH CERAMIC (ZrO2) DIESEL:- Speed (N) = 1500rpm, mw(cooling) = 0.0709kg/sec, mw(calorimeter) = 0.1389kg/sec.
V
I
TFC
BSFC
A/F
BHP
FHP
IHP
ηb
ηv
ηi
ηm
256
237
226
216
208
199
193
2.2
5.3
8.3
11.0
13.5
15.8
17.2
0.494
0.620
0.768
0.904
1.034
1.142
1.228
0.523
0.294
0.244
0.227
0.220
0.217
0.221
53.62
42.72
34.49
29.30
25.61
23.19
21.56
0.944
2.106
3.143
3.981
4.705
5.268
5.562
1.4
1.4
1.4
1.4
1.4
1.4
1.4
2.344
3.506
4.543
5.381
6.105
6.668
6.962
11.51
20.46
24.62
26.52
27.40
27.78
27.28
90.15
90.15
89.47
88.78
88.08
87.38
87.38
28.57
34.05
35.62
35.85
35.56
35.16
34.14
40.27
60.07
69.19
73.98
77.07
79.00
79.89
• HEAT BALANCE SHEET:-
Heat supplied BHP Heat carried away
By cooling water
Heat carried away
By exhaust gases
Unaccounted
Heat losses
(J/S) (J/S) %ge (J/S) %ge (J/S) %ge (J/S) %ge
5899.6
7404.6
9071.9
10797.3
12349.6
13639.6
14667.3
703.90
1570.44
2343.70
2968.60
3508.50
3928.30
4147.90
11.93
21.21
25.55
27.49
28.41
28.80
28.23
2078.0
2671.7
2968.6
3562.3
3859.2
4156.0
4452.9
35.22
36.08
32.37
32.99
31.25
30.47
30.36
1328.0
1389.0
2024.8
2071.8
2708.4
2763.6
3392.8
22.51
18.76
22.08
19.19
21.93
20.26
23.13
1789.7
1773.4
1814.38
2195.09
2273.56
2792.02
2681.2
30.34
23.95
20.00
20.33
18.41
20.47
18.28
• WITH CERAMIC (Al2O3) DIESEL:-
Speed (N) = 1500rpm,mw(cooling) = 0.0709kg/sec, mw(calorimeter) = 0.1389kg/sec.
V
I
TFC
BSFC
A/F
BHP
FHP
IHP
ηb
ηv
ηi
ηm
258
236
226
217
208
199
193
2.1
5.2
8.3
11.0
13.5
15.8
17.2
0.522
0.618
0.729
0.836
0.946
1.034
1.110
0.575
0.300
0.232
0.209
0.201
0.196
0.199
46.70
39.46
33.48
29.18
25.77
23.58
21.96
0.908
2.056
3.143
4.000
4.705
5.268
5.562
1.05
1.05
1.05
1.05
1.05
1.05
1.05
1.958
3.106
4.193
5.050
5.755
6.318
6.612
10.46
20.03
25.96
28.81
29.95
30.68
30.18
83.04
83.04
81.55
80.78
80.78
80.02
79.25
22.57
30.27
34.64
36.38
36.64
36.80
35.87
46.37
66.79
74.96
79.21
81.75
83.38
84.12
• HEAT BALANCE SHEET:-
Heat supplied BHP Heat carried away
By cooling water
Heat carried away
By exhaust gases
Unaccounted
Heat losses
(J/S) (J/S) %ge (J/S) %ge (J/S) %ge (J/S) %ge
6239.3
7383.1
8703.2
9984.6
11304.7
12353.9
13265.5
677.4
1533.8
2344.7
2984.0
3508.5
3929.9
4149.3
10.86
20.77
26.94
29.89
31.04
31.81
31.28
2078.0
2374.9
2671.7
2968.6
3562.3
3562.3
3859.2
33.30
32.17
30.70
29.73
31.51
28.84
29.09
1370.8
1378.5
1449.3
2067.1
2131.9
2736.0
2758.4
21.97
18.67
16.65
20.70
18.86
22.15
20.79
2113.2
2012.6
2011.3
1960.0
2101.5
2124.9
2499.2
33.87
27.26
23.11
19.63
18.59
17.20
18.84
0
10
20
30
40
50
60
70
80
90
0 1 2 3 4 5 6
BHP
Mechanical Efficiency
without ceramic with zirconia 0.35mm with alumina 0.25mm
0
5
10
15
20
25
30
35
40
0 1 2 3 4 5 6
BHP
Indicated Thermal Efficiency
without ceramic with zirconia 0.35mm with alumina 0.25mm
0
5
10
15
20
25
30
35
0 1 2 3 4 5 6
BHP
Brake Thermal Efficiency
without ceramic with zirconia 0.35mm with alumina 0.25mm
78
80
82
84
86
88
90
92
0 1 2 3 4 5 6
BHP
Volumetric Efficiency
w ithout ceramic w ith zirconia 350mm w ith alumina 250mm
HEAT BALANCE SHEET WITHOUT CERAMIC
USEFUL WORK
COOLANT LOSSES
EXHAUST LOSSES
UNACCOUNTED LOSSES
HEAT BALANCE SHEET WITH ZIRCONIA
USEFUL WORK
COOLANT LOSSES
EXHAUST LOSSES
UNACCOUNTED LOSSES
HEAT BALANCE SHEET WITH ALUMINA
USEFUL WORK
COOLANT LOSSES
EXHAUST LOSSES
UNACCOUNTED LOSSES
EFFECT OF INSULATION ON COMBUSTION:
The combustion chamber wall temperature of al LHR engine is higher than that of
a conventional water-cooled engine. Hence the charged air in cylinder absorbs heat emanating
from the high temperature chamber wall. Therefore the charged aired expands, this lessening the
amount of intake air. However if the increase in posit output is to be realized, a turbocharger
using higher exhaust energy and which increase the amount of intake air, or better still, a turbo
compound system that recovers that exhaust energy and converts it into additional power should
be connected with the LHR diesel engines.
The results if many past investigations on combustion show decrease in the
proportion of premixed combustion due to the shortening of the ignition delay and an increase in
the proportion diffusion combustion .The rate of heat release in the diffusion combustion phase
shows a decreasing trend form the early to middle period and lengthening of the subsequent
after-burring period. The decrease in volumetric efficiency and shortening of ignition delay
seem to be two of the reasons fro the slow and deteriorating combustion.
EFFECT OF INSULATION ON ENGINE PERFORMANCE :
Volumetric efficiency:
Volumetric efficiency is an indication of breathing ability of the engine. It
depends on the ambient conditions and op0erating conditions of the engine. Reducing heat
rejections with the addition of ceramic insulation causes and increases in the temperature of the
combustion chamber walls of an LHR engine. The volumetric efficiency should drop, as the
hotter walls and residual gas decrease the density of the inducted air.
Thermal efficiency:
Thermal efficiency is the true indication of the efficiency with which the chemical
energy input in the form of fuel is converted into useful work. Improvement in engine thermal
efficiency by reduction of in-cylinder heat transfer is the key objective of LHR engine research.
Much work has been done at many researches instituted to examine the potential of LHR engine
for reducing beat rejection and achieving high thermal efficiency. The in-cylinder heat transfer
characteristics of Let engine are still not clearly understood. Thus the effect of combustion
chamber insulation on reducing hears rejection and hence on thermal efficiency is not clearly
understood as on date.
Effect of injection characteristics on LHRE performance:
In heavy-duty diesel engines, rather than air motion-the momentum and energy of
the injected fuel are the major physical factors, which control the air fuel mixing process.
Accordingly it is necessary to optimize the fuel injection system of the heavy-duty uncooled
LHR diesel engines that the fuel economy of the LHR engine is of the same level as that of
waster cooled engine at the medium load but deteriorated significantly at the high load condition.
This to increased temperature of the combustion chamber walls, thus also increasing the
temperature of the fuel issuing from the heated nozzle orifice resulting in the reduced fuel
viscosity. This caused a heavy leakage fuel inside the nozzle and extended injection duration as
well. Admitting the need for tuning of the fuel injection system for LHR engine operation, be
optimized an injector tip configuration and achieved equal or superior fuel consumption.
EFFECT OF INSULATION ON EMISSION:
Unburned hydrocarbon
The emission of unburned Hydrocarbon forms the LHR engines is more likely to
be reduced because of the decreased quenching distance and the increased lean flammability
limit. The higher temperatures both in the gases and at the combustion chamber walls of the
LHR engine assist in permitting the oxidation reaction to proceed close to completion. The
burring of lubricating oil due to high wall temperature is believed to be the other reason for
increased UBHC level.
Carbon monoxide
It might be expected that LHR engines would produce less Carbon monoxides, for
reasons similar to those for unburned Hydrocarbon. In fact many investigations indicate lower
level of CO emissions. They attribute this to high gas temperature and combustion chambers
walls. The reduced level of pre-mixed combustion in the insulated engine decreases the initial
production CO and the higher temperatures during diffusion combustion accelerate the oxidation
of CO.
Nitrogen oxides:
NOx is formed by chain reactions involving Nitrogen and Oxygen in the air.
These reactions are highly temperature dependent. Since diesel engines always operate with
excess air, NOx emissions are mainly a function of gas temperature and residence time. Most of
the earlier investigation shows that NOx emission from LHR engines is generally higher than that
in water-cooled engines. They say this is due to higher combustion temperature and longer
combustion duration.
Smoke and particulates:
It might be expected that LHR engines would produce less smoke and particulates
than standard engines for reasons such as high temperature gas and high temperature combustion
chamber wall. Earlier investigations show that smoke and particulate emission level increased in
some cases and decreased in few others.
FINITE ELEMENT ANALYSIS
Introduction
Finite element structural analysis is a method of predicting the behavior of a real structure
under specified load and displacement conditions. The finite element modeling is generalization
of the displacement or matrix method of structural analysis to two and three-dimensional
problems and three-dimensional problems. The basic concept of FEM that structure to be
analyzed is considered to be an assemblage of discrete pieces called “elements” that are
connected together at a finite number of points or nodes. The finite element is a geometrically
simplified representation of a small part of the physical structure.
Discretising the structure requires experience and complete understanding of the behavior
of the structure can behave like a beam, truss, plate, and shell.
WWHHYY FFEEMM:-
• FEA is applicable to any field problem: heat transfer, stress analysis, magnetic fields
and so on.
• There is no geometric restriction. the body or region analyzed has any shape.
• Boundary conditions and loading are not restricted.
• Material properties are not restricted to isotropy and may change from one element to
another or even within an element.
• Components that have different behaviors, and different mathematical descriptions,
can be combined.
• An FE structure closely resembles the actual body or region to be analyzed.
• The approximation is easily improved by grading the mesh so that more elements
appear where field gradients are high and more resolution is required.
ENGINEERING APPLICATIONS OF THE FINITE ELEMENT METHOD:
The finite element method was developed originally for the analysis of aircraft
Structures. However the general nature of its theory makes it applicable to a wide Variety of
boundary value problems in engineering. A boundary value problem is One in which a solution
is sought in the domain (or region) of a body subject to the Satisfaction of prescribed boundary
(edge) conditions on the dependent variables or their derivatives.
Engineering applications of the finite element method:
1. Civil engineering structures.
2. Air craft structures
3. Heat conduction
4. Nuclear engineering
5. Mechanical design.
FINITE ELEMENT METHOD CONCEPT:
The finite element method is defined as discretization whole region (model) in to small
finite number of elements. These small elements connected to each other at node points. Finite
element analysis grew out of matrix methods for the analysis of structure when the widespread
availability of the digital computer made it possible to solve systems of hundreds of
simultaneous equations using FEA software like Nastran, Ansys etc.
Types of Analysis:
Static analysis
A structural model thus created can be used to predict the behavior of their real structure,
under the action of external forces. The response is usually measured in terms of deflection and
stress. The response is static if the loads are steady. This analysis is called static analysis.
Dynamic analysis
When the loads vary with time, the analysis is called dynamic analysis. A dynamic force
will excite velocities and accelerations that produce appreciable variations of displacement and
stresses. These are computed over time and the response history is called transient response
analysis.
Another type of dynamic analysis is the computation of model’s natural frequencies of
vibration and associated mode shapes. For example, such a type of analysis can be used to study
the response of an automobile traveling over a bumpy road at a particular speed. The dynamic
force may be create uncomfortable vibrations of the steering mechanism or door panel or the
cabin or a truck amplitudes of vibration to ensure good surface finish on work pieces and better
tool life. When designing such components, it is important to avoid natural frequencies, which
might be exited in the course of normal operation.
Linear and Non-linear analysis
If the properties of the structure, such as stiffness remain constant during the entire
analysis, the analysis is called linear. If these properties vary, the analysis is non-linear. Such
variation can be due to large displacement in the structures (geometric non-linearity), large scale
yielding in the material (material non-linearity) or changes in boundary conditions.
Thermal analysis
Finite element analysis can be used for several design and analysis problems involving
thermal stresses, thermal displacement, heat flow, temperature distribution etc.
Fluid flow analysis
Finite element analysis can solve several types of fluid flow problems.
Field analysis
Problems in magnetic and acoustics can be solved by finite element analysis.
Degree of Freedom
The deformations of the structure are represented by the displacements in the nodes.
These displacements are referred to as degrees of freedom which can be either transnational or
rotational. Each element type will have a predetermined set of degrees or freedom assigned to it.
GENERAL PROCEDURE OF THE FINITE ELEMENT METHOD
The following are the general steps included in a finite element method formulation and
solution to an engineering problem.
STEP 1:
Discretize and select the element types:
Discretization means dividing the body into an equivalent system of finite Elements
with associated nodes and choosing the most appropriate element type to model most closely the
actual physical behavior. The total numbers of elements used and their Variation number, size
and types with in a given body are primarily matter of engineering Judgment. The elements must
be made small enough to give usable results and at large enough to reduce computational effort.
Small elements (and possibly higher order elements) are generally desirable where the results are
changing rapidly, such as where changes in geometry occur; large elements can be used where
results are relatively constant. The discretized body or mesh is often created with mesh-
generation programs or pre-processor programs available to the user.
STEP 2:
Select a Temperature model/Interpolation function:
The function is defined with in the element using the nodal values of the element.
Linear, quadratic, cubic polynomials are frequently used functions because they are Simple to
work with in finite element formulation. For a two-dimensional element, the Temperature
/temperature function is a function of the co-ordinates in its plane (say x-plane). The functions
are expressed in terms of the nodal unknowns (in the 2-D problems In terms of x and y
component). The same general temperature/functions can be used repeatedly for ach element.
Hence the finite element method is one which a continuous quantity such as the temperature
through out the body, is approximated by a discrete model composed of a set of piecewise
continuous functions defined with in each domain or finite element.
STEP 3:
Deriving the element conductivity matrices and equations:
Initially, the development of element conductivity matrices and element equations are
based on the concept of influence coefficients, which presupposes a background in Thermal
analysis. These equations are written conveniently in matrix from or in compact Matrix from as:
[Key]=∫ ∫ ∫v [Be] T [De] [Be] Dv
Where K is element conductivity matrix, B is nodal displacement matrix and D is
called properties matrix.
STEP 4:
Assembly of the element conductivity matrices/equations to obtain the
Global or total matrix/equations and introduce boundary conditions:
The individual element equations generated in step 3 can now be added together to
Obtain the global matrix /equations for the whole continuum
[K] {T} = {P} -------------eq (2)
Where {P} is the vector of global nodal Heat flow rate, [K]is the continuum global or Total
matrix and {T} are now the vectors of known and unknown continuum nodal Degree of freedom
or generalized temperatures. It can be shown that at this stage, the global conductivity matrix is a
singular matrix because its determinant is equals to zero
To remove this singularity problem, we must invoke boundary conditions (or constraints or
supports) so that the continuum remains in place instead of moving as a rigid body.
STEP 5:
Solve for unknown degrees of freedom (or generalized temperatures):
Eq (2) modified to account for the boundary conditions, is a set of simultaneous algebraic
equations that can be solved for the P or T by using an elimination method.
STEP 6:
Interpret the results:
The final goal is to interpret and analyze the results for use in the design or analysis
process. Determination of location in the continuum where large temperatures and large heat
fluxes occur is generally important in making design or analysis decisions. Post-processor
computer programs help the user to interpret results by displaying them in graphical form
THERMAL ANALYSIS OF CERAMIC COATED PISTON
USING ANSYS
PROCEDURE:
Preferences→thermal
Preprocessor→element type→solid →plane 82
Element behavior → axi symmetric
Material properties→isotropic
Cast iron Aluminium Zirconia Alumina
Young’s modulus
(GPa)
170
71
200
370
Thermal conductivity
(W/m-k)
51.9
174
2.5
30
Thermal Expansion Coefficient (10-6 /0c)
6.16
23.4
9.8
7.4
Density (kg/m3)
7800
3000
5700
3960
Poisson’s
ratio
0.29
0.3
0.33
0.22
Modeling→create key points→
1) (0,0) 2) (0.025,0) 3) (0.04,0) 4) (0.04,-0.015) 5) (0.036,-0.015) 6) (0.036,-0.018) 7) (0.04,-0.018) 8) (0.04,-0.024) 9) (0.036,-0.024) 10) (0.036,-0.027) 11) (0.04,-0.027) 12) (0.04,-0.033) 13) (0.036,-0.033) 14) (0.036,-0.036) 15) (0.04,-0.036) 16) (0.04,-0.086) 17) (0.036,-0.086) 18) (0.036,-0.09) 19) (0.04,-0.09) 20) (0.04,-0.11) 21) (0.034,-0.11) 22) (0.034,-0.1) 23) (0.034,-0.096) 24) (0.034,-0.082) 25) (0.034,-0.078) 26) (0.03,-0.078) 27) (0.03,-0.028) 28) (0,-0.025) 29) (0,-0.03) 30) (0.04,-0.055) 31) (0.04,-0.065) 32) (0.03,-0.065) 33) (0.03,-0.055) 34) (0.026,-0.021) 35) (0.03,-0.024) 36) (0.0248, 0.0002) 37) (0.04, 0.0002) 38) (0,-0.0248) 39) (0.0248,0) 40) (0.038,-0.06)
for ceramic coatings :
Thickness key points
0.35mm 41) (0,-0.02465) 42) (0.02465, 0.00035) 43) (0.04, 0.00035)
0.25mm 41) (0,-0.02475) 42) (0.02475, 0.00025) 43) (0.04, 0.00025)
Create→ areas →by lines
Mesh tool → Mesh areas
Solution → Apply → Loads
→ Heat flow on nodes <select nodes> heat flow =0
→ Apply convention on lines
W/m2-k temp
83.05 823o c
72.09 300o c
66.72 165o c
66 150o c
→ Solve → current L.S.
General post processor → plot results → DOF solution (temp distribution).
Finding the Boundary conditions:
Diesel Cycle
From P-V& T-S diagrams:-
Process 1→ 2:- adiabatic compression
γγ== VV11//VV22;; TT22 == TT11 γγ((γγ--11))..
PPrroocceessss 22→→ 33::-- ccoonnssttaanntt pprr hheeaatt aaddddiittiioonn
TT33//TT22 ==VV33//VV22 == γγCC ((ccuutt--ooffff rraattiioo))
TT33 ==TT22 γγCC
PPrroocceessss 33→→ 44::-- aaddiiaabbaattiicc eexxppaannssiioonn
TT44//TT33== ((VV33//VV44))((γγ--11))..
1166..55 == (( vvss++vvcc))//vvcc..
VV11 ==VV44==558888..5599cccc
VV22==3355..6677cccc..
TT11 == 228800CC==330011 KK
TT22== ((330011)) ((1166..55))00..44==992233..776622 KK..
PPrroocceessss 44→→11:: -- ccoonnssttaanntt vvoolluummee hheeaatt rreejjeeccttiioonn
WWee kknnooww tthhaatt
CCpp ((TT33--TT22)) ==HHeeaatt ssuupppplliieedd//kkgg ooff aaiirr ((kkjj//kkgg))
11..000044((TT33--992233..776622)) == 1100992266..33//66..883366==11559988..3355
((TT33--992233..776622))==11559911..9988
══>>TT33==22551155..7744 KK;; TT44== 664422 KK..
TTmmeeaann == ((330011++992244++664422++22551166))//44 ══>> 11009966kk
==88223300CC
v→
↑ P
1
4
3 2
s→→
↑ T
1
2
3
4
PPrrooppeerrttiieess ooff aaiirr aatt 88223300cc:: --
ρρ==00..3322225566 kkgg//mm33,, νν==113399..4477ee--66mm22//sseecc
PPrr==00..771144,,KK==7722..88ee--33ww//mm--kk..
mm.. ==ρρaavv ==>>vv==66..883366ee--33// ((00..3322225566**ΠΠ//44**((00..000022))22)) ==6677..4466 mm//sseecc..
RRee==6677..4466**00..1111// ((113399..4477ee--66)) ==>>5533220055..77
FFrroomm hheeaatt aann mmaassss ttrraannssffeerr ddaattaa hhaanndd bbooookk
hhll//kk== 00..002233**((RRee))00..88**((PPrr))00..33..
hh== ((00..002233**7722..88ee--33))// ((00..1111))**((553322220066))00..88**((00..771144))00..33..
==8833..0055ww//mm22--kk..
TThheerrmmaall AAnnaallyyssiiss ooff PPiissttoonn::
PPiissttoonn FFrroonntt VViieeww
PPiissttoonn IIssoommeettrriicc VViieeww
PPiissttoonn 22--DD vviieeww
PPiissttoonn wwiitthh mmeesshh
Al without coating
CI without coating
CI with alumina .250mm
CI with Zirconia .350mm
Al with alumina .250mm
Al with Zirconia .350mm
Results
Effect of ZrO2 (0.35mm): -
1. Increase in Volumetric efficiency by 7%.
2. Decrease in Knocking by 29.06%.
3. Decrease in Brake Thermal efficiency by 1.5--2%.
4. Increase in FHP by 27.3%.
5. Decrease in Mechanical Efficiency by 4--5%.
6. Decrease in Unaccounted heat losses by 12%.
7. Heat carried by exhaust gases increases by 3%.
Effect of Al2O3 (0.25mm): -
1. Decrease in Volumetric Efficiency by 1.2%.
2. Increase in Knocking by 5.93%.
3. Increase in Brake Thermal Efficiency by 4.5%.
4. Decrease in FHP by 4.5%.
5. Increase in Mechanical Efficiency by 1--2.5%.
6. Decrease in Unaccounted heat losses 4-8%.
7. Heat carried away by exhaust gases increases by 1--2%.