DOI : 10.17577/IJERTV2IS60379
- Open Access
- Total Downloads : 1085
- Authors : Dinesh Kumar. J., Harish. R. Sankar, Raja R
- Paper ID : IJERTV2IS60379
- Volume & Issue : Volume 02, Issue 06 (June 2013)
- Published (First Online): 11-06-2013
- ISSN (Online) : 2278-0181
- Publisher Name : IJERT
- License:
This work is licensed under a Creative Commons Attribution 4.0 International License
Influence of Thermal Barrier Coatings on S.I Engine Performance
Dinesh Kumar. J Scholar, Department Of Mechanical Engineering, The Oxford College Of Engineering, Bangalore, Karnataka, India.
Harish. R.Sankar Scholar, Department Of Mechanical Engineering, The Oxford College Of Engineering, Bangalore, Karnataka, India.
Raja R
Professor & Head, Department of Automobile Engineering, The Oxford College of Engineering, Bangalore, Karnataka, India.
ABSTRACT
The thermal efficiency of most commercially used engine ranges from 38% to 42%, as nearly 58% to 62
% of energy is lost in the form of waste heat. Nearly 30% is retained in exhaust gas and the remaining is removed in cooling water/air, in order to save energy the hot parts are insulated thermally. This will lead to reduction in heat transfer through the engine, involving an increased efficiency. Change in combustion process due to insulation also affects emissions. Higher gas temperature should reduce the concentration of incomplete combustion products at the expense of an increase in nitrogen oxides (NOx). However a decrease in carbon monoxide (CO) unburned hydrocarbons (HC) is observed. Also the highest temperature of any point on piston should not exceed 66% of the melting point temperature of the alloy. This limiting temperature of the piston alloy can be increased by using TBC. Ceramics have higher
thermal durability than metals, therefore it is usually not necessary to cool them as fast as metals.[6]
Thermal Barrier Coatings (TBC) provides the potential for higher thermal efficiencies of the engine, improved combustion and reduced emissions. In addition ceramics show better wear characteristics than conventional materials. A lot of experimental study has to be done to utilize these ceramic prosperities to improve thermal efficiency by reducing heat loss, and to improve mechanical efficiency by eliminating cooling system.[5]
Keywords : S.I Engine – Thermal Barrier Coatings (TBC) Piston Ceramics Emissions – Heat
Transfer Combustion Aluminium – Zirconium Dioxide – Titanium Dioxide.
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INTRODUCTION
The rapid increase in fuel expenses, the decreasing supply of high grade fuels on the market and environment concerns stimulated research on more efficient engines with acceptable emission characteristics. The state of art thermal barrier coating (TBC) provides the potential for higher thermal efficiencies of the engine, improved combustion and reduced emission. In addition ceramic shows better wear characteristics than conventional material.
There are contradictory reports on the effect of TBC on engine performance. Obtained results depend on the type of the engine and conditions of test. Measurement of temperatures and heat flux is difficult, thermal problems often interfere with temperature distribution and materials used to construct them can catalyze the combustion process.
Ceramics have a higher thermal durability than metals. Therefore it is usually not necessary to cool them as fast as metals. Lower heat rejection from the combustion chamber through thermally insulated components causes an increase in available energy that would increase the in-cylinder work and the amount of energy carried by exhaust gases, which could also be utilized.
The engine selected for evaluation of the thermal barrier coating was a two-stroke, single cylinder, petrol engine. First this engine was tested as equipped with anair cooled at different speeds and loads condition without a coating. Then the surface of the
engines piston crown was coated with ceramic materials. The piston crown was coated with 0.35mm thickness of ZrO2 over a 0.15mm thick NiCrAl bond coat. The material used on the pistons was aluminium alloy. The coating process was performed using the plasma spray technique. Finally the ceramic-coated engine was tested again under the same operation conditions as the standard engine.[5]
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IMPROVEMENT IN ENGINE PARAMETERS
The primary objectives that we like to achieve by adiabatizing the engine cylinder by using Thermal Barrier Coatings (TBC) are as follows:
-
To increase the thermal efficiency of the engine.
-
To increase the temperature of combustion in the engine cylinder for complete combustion.
-
To reduce the fuel consumption.
-
To reduce the exhaust emission gases.
-
To increase the performance of the engine.
-
To find which coating among ZrO2 and TiO2 gives better adiabatization of the engine.
-
-
EXPERIMENTAL TESTING
-
Engine testing with and without coated piston.
-
Comparison of results with & without coating.
-
Tabulation and Generating graphical representations.
A two-stroke, single cylinder, and air-cooled petrol engine is selected to conduct the study. The engine is to be tested for its performance at various operating conditions without piston crown coating. Then the surface of the piston crown is coated with two different TBCs materials. Four pistons are selected for TBCs two pistons (P2, P3) are coated with ZrO2 of various thicknesses as given in table. The other two pistons (P4, P5) are coated with TiO2 of various thicknesses as given in table. The coating process is performed using the plasma spray technique. The engine is to be tested for its performance at various operating conditions. The results for both cases are to be analysed and then compared.
Fig.1: The Experimental Setup Table.1: Coating Thickness of Materials Used
3.1 PLASMA SPRAY PROCESS
The plasma spraying process uses a DC electric arc to generate a stream of high temperature ionised plasma gas, which acts as the spraying heat source. The coating material, in powder form, is carried in an inert gas stream into plasma jet where it is heated and propelled towards the substrate. Because of the high temperature and high thermal energy of plasma jet, material with high melting points can be sprayed.
Using the plasma spray process the TBC materials where sprayed on to the head of the piston at various thickness as mentioned in the above table.[2] [3]
-
PISTON& COATING MATERIALS
-
ALUMINIUM
The principleuses of aluminium are for aircraft, machinery, electrical conductors, and cooking utensils. Aluminium has largely created its own uses,
and has not replaced steel in its traditional uses, as was once anticipated. The two principal structural metals are complementary more than competitive. Aluminium is very easy to work with in the shop, and has indeed replaced the more expensive brass in many applications. Aluminium, however, cannot be soldered, which is a severe disadvantage. It is very easy to make aluminium castings.[1]
-
ZIRCONIUM DIOXIDE (ZrO2)
Pure zirconia exists in three crystal phases at different temperatures. At very high temperatures (>2370°C) the material has a cubic structure. At intermediate temperatures (1170 to 2370°C) it has a tetragonal structure. This behaviour destroys the mechanical properties of fabricated components during cooling and makes pure zirconia useless for any structural or mechanical application. Several oxides which dissolve in the zirconia crystal structure can slow down or eliminate these crystal structure changes. Commonly used effective additives are MgO, CaO, and Y2O3. With sufficient amounts added, the high temperature cubic structure can be maintained to room temperature. Cubic stabilized zirconia is a useful refractory and technical ceramic materal because it does not go through destructive phase changes.
Zirconia is an extremely refractory material. It offers chemical and corrosion inertness to temperatures well above the melting point of alumina. The material has low thermal conductivity. It is electrically conductive above 600°C and is used in oxygen sensor cells and as the heater in high temperature induction furnaces. [1]
Fig.2: Zirconium Dioxide Coated Piston
-
TITANIUM DIOXIDE (TiO2)
Titanium dioxide has its systematic name of Dioxotitanium. With its molecular formula of TiO2 and molecular weight of 79.87, it occurs in nature as well-known minerals rutile, anatase and brookite. Recently, Ries crater in Bavaria found two high
pressure forms additionally, a monoclinic baddeleyite- like form and an orthorhombic -PbO2-like form. But the most common form is rutile that is also the equilibrium phase at all temperatures. Titanium dioxide is insoluble in water and organic solvents, but slowly soluble in hydrofluoric acid and hot strong sulphuric acid. When you need to store it, it should be kept sealed in the cool, dry and well-ventilated place.
Pure titanium dioxide does not occur in nature but is derived from ilmenite or leuxocene ores. It is also readily mined in one of the purest forms, rutile beach sand. These ores are the principal raw materials used in the manufacture of titanium dioxide pigment. The first step is to purify the ore, and is basically a refinement step. Either the sulphate process, which uses sulphuric acid as an extraction agent or the chloride process, which uses chlorine, may achieve this. After purification the powders may be treated (coated) to enhance their performance as pigments.[1]
Fig.3: Titanium Dioxide Coated Piston
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NICKEL CHROMIUM ALLOY (NiCrAl) [BOND COAT]
The nickel-chromium system shows that chromium is quite soluble in nickel. This is a maximum at 47% at the eutectic temperature and drops off to about 30% at room temperature. A range of commercial alloys is based on this solid solution. Such alloys have excellent resistance to high temperature oxidation and corrosion and good wear resistance.
Increase in electrical resistivity is observed with increasing chromium additions. An addition level of 20% chromium is considered the optimum for electrical resistance wires suitable for heating elements. This composition combines good electrical properties with good strength and ductility, making it suitable for wire drawing. Small modifications of to
this composition may be made to optimise it for particular applications. [1]
Table.2: Properties of Ceramic Materials Used [4]
-
-
EXPERIMENTAL RESULTS
The following table shows the change in different efficiencies depending of the material used as TBC.
Table.3: Tabulation for Efficiency for Different TBC Materials
The following graphs show the change in efficiency and performance for different material used as TBC.
SFC vs BP
SFC vs BP
0.05
0.045
0.04
0.035
0.03
0.025
AL ALLOY PISTON
ZrO2 PISTON
0.05
0.045
0.04
0.035
0.03
0.025
AL ALLOY PISTON
ZrO2 PISTON
0
0.2
0.4 0.6
0.8
1
0
0.2
0.4 0.6
0.8
1
BP in kw
BP in kw
0.02
0.02
TiO2 PISTON
TiO2 PISTON
0.015
0.01
0.005
0
0.015
0.01
0.005
0
SFC in Kg/KW.Min
SFC in Kg/KW.Min
BTE in %
BTE in %
Fig.4: Specific Fuel Consumption vs Brake Power
BTE vs BP
14
12
10
8
6
AL ALLOY PISTON
ZrO2 PISTON
BTE vs BP
14
12
10
8
6
AL ALLOY PISTON
ZrO2 PISTON
4
TiO2 PISTON
4
TiO2 PISTON
2
0
2
0
0
0.2
0.4
0.6
0.8
1
0
0.2
0.4
0.6
0.8
1
BP in kw
BP in kw
45
40
35
30
25
45
40
35
30
25
AL ALLOY PISTON
ZrO2 PISTON
AL ALLOY PISTON
ZrO2 PISTON
ME in %
ME in %
Fig.5: Brake Thermal Efficiency vs Brake Power
ME vs BP
ME vs BP
10
5
0
10
5
0
0
0.2
0.4
0.6
0.8
1
0
0.2
0.4
0.6
0.8
1
BP in kw
BP in kw
20
15
20
15
TiO2 PISTON
TiO2 PISTON
Fig.6: Mechanical Efficiency vs Brake Power
The following tables give the change is emission observed when different material are used as TBC.
Table.4: Tabulation for Al Alloy Piston
SL NO
BP
Load
CO
CO2
HC
NOX
in Kw
in kg
in ppm
1
0.18701
0.8
8.02
1.6
4385
43
2
0.27013
1.4
8.82
1.82
3766
39
3
0.41558
2.2
9.3
2.1
3448
36
4
0.56104
2.9
9.37
2.29
3136
33
5
0.81039
3.7
9.58
2.38
3112
31
Table.5: Tabulation for Zirconium Dioxide Coated Piston
SL NO
BP
Load
CO
CO2
HC
NOX
in Kw
in kg
in ppm
1
0.1870
0.75
2.02
2.3
1694
26
2
0.2701
1.5
3.2
3.34
1495
45
3
0.4155
2.25
4.05
4.55
1428
54
4
0.6026
3
4.79
5.42
1380
61
5
0.8311
3.75
5.09
5.81
1350
67
Table.6: Tabulation for Titanium Di Oxide Coated Piston
SL NO
BP
Load
CO
CO2
HC
NOX
in Kw
in kg
in ppm
1
0.166235
0.9
2.13
3.53
2586
28
2
0.290912
1.5
4.65
4.45
2365
40
3
0.415588
2.3
5.86
4.92
2112
47
4
0.602603
2.85
7.10
5.21
1986
53
5
0.831176
3.85
7.11
5.07
1852
58
HC in ppm
HC in ppm
The following graphs sho the change in emissions for different material used as TBC.
HC vs LOAD
HC vs LOAD
5000
4500
4000
3500
3000
2500
AL ALLOY PISTON
ZrO2 PISTON
5000
4500
4000
3500
3000
2500
AL ALLOY PISTON
ZrO2 PISTON
2000
TiO2 PISTON
2000
TiO2 PISTON
1500
1000
500
0
1500
1000
500
0
0
0.2
0.4
0.6
0.8
1
0
0.2
0.4
0.6
0.8
1
LOAD in kw
LOAD in kw
30
30
NOX in ppm
NOX in ppm
Fig.7: HC vs LOAD
NOX vs LOAD
80
70
60
50
40
AL ALLOY PISTON
ZrO2 PISTON
NOX vs LOAD
80
70
60
50
40
AL ALLOY PISTON
ZrO2 PISTON
20
10
0
20
10
0
0
0.1 0.2 0.3 0.4 0.5 0.6
0.7 0.8 0.9
0
0.1 0.2 0.3 0.4 0.5 0.6
0.7 0.8 0.9
LOAD in kw
LOAD in kw
TiO2 PISTON
TiO2 PISTON
Fig.8: NOX vs LOAD
CO2 vs LOAD
CO2 vs LOAD
7
6
5
4
AL ALLOY PISTON
ZrO2 PISTON
7
6
5
4
AL ALLOY PISTON
ZrO2 PISTON
2
1
0
2
1
0
0
0.2
0.4
0.6
0.8
1
0
0.2
0.4
0.6
0.8
1
LOAD in kw
LOAD in kw
3
3
TiO2 PISTON
TiO2 PISTON
CO in ppm
CO in ppm
CO2 in ppm
CO2 in ppm
Fig.9: CO2 vs LOAD
CO vs LOAD
CO vs LOAD
12
10
8
6
AL ALLOY PISTON
ZrO2 PISTON
TiO2 PISTON
12
10
8
6
AL ALLOY PISTON
ZrO2 PISTON
TiO2 PISTON
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
LOAD in kw
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
LOAD in kw
4
2
0
4
2
0
Fig.10: CO vs LOAD
-
RESULT ANALYSIS
Two sets of experiments were conducted with conventional and TBC coating of zirconiumdioxide (ZrO2) and titanium dioxide (TiO2) coated pistonon the piston crown. In each set of tests, readings of engine speed, load torque, engine power, fuel consumption, exhaust gas temperature, gas emission concentration, readings were taken with various engine loads and various engine speeds (1000 to 4500rpm).
Total fuel consumption has comparatively reduced in TBC over conventional AL Alloy piston and also increase in brake thermal efficiency,Indicated thermal efficiency and also increase in volumetric efficiency. ZrO2has a better performance over TiO2 and AL Alloy piston.
When comparing piston coated with ZrO2 and piston coated with TiO2 it was found that the piston with
ZrO2 coating provided better results than the TiO2 coated piston. The piston with ZrO2 coating provides better efficiency and performance when compared with the TiO2 coated piston. The difference in the efficiency between ZrO2 coated piston and TiO2 coated piston was in the range of 1% to 2%. In the case of air-fuel ratio it was found that ZrO2 coated piston had an air-fuel ratio of 13.26. But the air-fuel ratio of TiO2 coated piston was 11.61. The engine with ZrO2 coated piston also shows better result in fuel consumption when compared with TiO2 coated piston.
In the case of emissions it was found that the ZrO2 coated piston emits less CO and HC when compared with TiO2 coated piston. But it is to be noted that both ZrO2 and TiO2 coated piston showed an increase in NOx and CO2 when compared with plain AL alloy piston. The ZrO2 coated piston engine showed a slight increase in NOx and CO2 emissions when compared with TiO2 coated piston engine.
-
ACKNOWLEDGEMENT
We would like to express our gratitude to Dr.NageswaraRao, Professor and Head, Dept. of Mechanical Engineering, The Oxford College of Engineering, for providing a congenial environment and surroundings to work in. We express our thanks to Dr Raja R, HOD, Dept. Automobile engineering, who provided us with theguidance, support and continuous encouragement. Last but not least, I would like to thank the teaching and non-teaching staff of TOCE for extending their co-operation and help.
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CONCLUSION
Experimental investigation of the effect of ceramic coating on petrol engine performance and exhaust emissions was conducted.
-
The TBC, using ZrO2 and TiO2 applied on the piston crown of internal combustion engine showed some improvement in fuel economy
-
The unburned hydrocarbon concentration was increased mostly at low engine speed or low engine power output with a TBC piston engine.
-
CO emission and HC were lower in the coated engine.
-
The specific fuel consumption shows a 1% decrease in the engine with TBC
-
Significant increase in engine performance was observed.
-
The performance of thermally coated engine was found to be satisfactory.
-
The NOX and CO2 can be reduced by using catalytic converter or EGR systems.
-
-
REFERENCES
-
http://www.wikipedia.org/
-
-
http://www.pistoncoating.cc/
-
Dr .K. Lingaiaha Design Data Hand Book,
Vol I and II, Suma publishers 2006
-
P.M. Pierz
Thermal barrier coating development for diesel engine aluminium pistons
-
Georges Descombes, FadilaMaroteaux and Michel Feidt
Study of the interaction between mechanical energy and heat exchanges applied to IC engines