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Improving the usability of vegetable oils as a fuel in a low heat rejection diesel engine
Fuel Processing Technology 98 (2012) 59–64
Contents lists available at SciVerse ScienceDirect
Fuel Processing Technology journal homepage: www.elsevier.com/locate/fuproc
Improving the usability of vegetable oils as a fuel in a low heat rejection diesel engine Bahattin İşcan a,⁎, Hüseyin Aydın b a b
Department of Mechanics, Vocational School of Higher Education, Batman University, Batman 72060, Turkey Department of Automotive, Vocational School of Higher Education, Batman University, Batman 72060, Turkey
a r t i c l e
i n f o
Article history: Received 22 November 2011 Received in revised form 1 February 2012 Accepted 2 February 2012 Available online 25 February 2012 Keywords: Low heat rejection engine Vegetable oil Ceramic coating Diesel engine
a b s t r a c t Usability of a waste vegetable oil in coated diesel engines was experimentally investigated. Waste corn oil was blended with petroleum diesel fuel by ratios of 15% corn oil to %85 diesel fuel (B15), 35% corn oil to %65 diesel fuel (B35) and 65% corn oil to %35 diesel fuel (B65). The surfaces of the engine piston and both intake and exhaust valves were coated with ZrO2 layer in order to make the combustion chamber insulated. Thus heat transfer through the combustion chamber was aimed to be reduced with the purpose of increasing the thermal efficiency and performance of the engine and also maintain the usability of vegetable oil in diesel engines. B15, B35, B65 and standard diesel fuels were used in the coated test engine. Performance parameters and exhaust emissions characteristics of all the above mentioned fuels were clarified and compared with uncoated engine test values of normal diesel fuel. It is believed that the main purpose of this study has been achieved as the engine performance parameters such as power and torque of the engine were increased with simultaneous decreases in the brake specific fuel consumption (bsfc). Besides, many of exhaust emission parameters such as CO, HC, and smoke opacity were decreased. © 2012 Elsevier B.V. All rights reserved.
1. Introduction Availability of energy sources, energy utilization and accompanied problems such as, environmental pollution and sustainability are forming a good part of main research topics of scientific world. Diesel engine studies such as fuel availability, alternative fuel investigation and reduction of emissions are crucially ongoing. Diesel engines generally have better fuel consumption characteristics than gasoline engines. Besides, theoretically if the heat rejection can be reduced, then the thermal efficiency will be improved, at least up to the limit set by the second law of thermodynamics [1]. Low heat rejection engines aim to do this by reducing the heat transferred to the coolant. A review was presented in Ref. [1] and it concluded that many studies have been carried out on low heat rejection diesel engine performance but much more studies are needed to overcome the practical problems. Besides, different types of fuel or additives can be researched by means of utilizing them in diesel engines. 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 the exhaust gases, which could be also utilized [2,3]. Ceramic materials have a higher thermal durability than metals.
⁎ Corresponding author. E-mail addresses: [email protected] (B. İşcan), [email protected] (H. Aydın). 0378-3820/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2012.02.001
Therefore, they are not required to cool as fast as metals. Ceramic materials with low thermal conductivity can be used to control temperature distribution and heat flow in a structure [4–6]. Thermal barrier coatings can provide higher thermal efficiencies of the engine thus improve combustion and reduce emissions. Besides, these materials show better wear characteristics than conventional materials. It was reported that combustion characteristics of LHR diesel engines were different from standard diesel engines in four ways [7]: (a) Ignition delay period shortens; (b) diffusion burning period increases while premixed burning period decreases; (c) total combustion duration increases; (d) heat release rate in diffusion burning period decreases. In spite of the fact that the use of LHR engines is found to be promising, many of the reported studies showed contradictory results. Most of the researchers have reported that insulation can decrease heat transfer, increase thermal efficiency and improve energy availability in the exhaust. However, contrary to the above presentations some experimental studies showed that there was little or no improvement in thermal efficiency [8–9]. Different materials such as aluminum, silicon nitride, silicon carbide, magnesium silicate, molybdenum, and some other ceramic materials have been used to make a LHR engine. In the present study, the usability of waste vegetable oil in a conventional diesel engine and a thermally insulated diesel engine was experimentally investigated and compared with each other. The surfaces of the engine piston and both intake and exhaust valves were coated with ZrO2 layer in order to make the combustion chamber insulated.
B. İşcan, H. Aydın / Fuel Processing Technology 98 (2012) 59–64
60
Diesel Fuel Tank
Test Fuel Tank
Mixer
Exhaust Gas Analyzer
Dynamometer Control Panel Air Flow
CAMERA SELECT
1 2 3 4 5 6 7 8
NOx
2
4
5
3 6
7
8
9
0
9 10 11 12 13 14 15 16
CO, HC, CO2
1
Silencer
Air mass Speed Temperature Load
Dynamometer Coupling
Smoke Analyzer
Engine
Fig. 1. Schematic diagram of experimental setup.
2. Engine test materials and experimental procedure Performance and emission tests were performed at the engine test laboratory of Automotive Department at University of Batman. Schematic diagram of experimental setup was presented in Fig. 1. A BT140 model hydraulic dynamometer was used for performance tests. The engine test specifications were presented in Table 1. Exhaust emission test was carried out with a Capellec CAP 3200 model emission analysis device. Technical properties of emission test device were given in Table 2. The fuel consumption was measured in burettes with 50 and 100 ml volumes and a stopwatch. The brake specific fuel consumption was calculated with the following equation. be ¼
V_ :ρ:3600 Pe
ð1Þ
Where “be” is the brake specific fuel consumption as g/kWh, “V_ ” is the flow rate of the fuel as cm 3/sn, “ρ” is the density of the fuel as g.cm − 3 and “Pe” is the brake power as kW. Table 1 Technical specifications of the test engine. Type
Rainbow-186 diesel
Injection system Cylinder number Stroke volume Compression ratio Maximum power Maximum engine speed Cooling system Injection pressure Mean effective pressure (Mep) Medium piston speed
Direct injection 1 406 cc 18/1 10 HP 3600 rpm ±20 Air cooling 19.6 ± 0.49 MPa (200 ± 5 Kgf/cm2) 561.6 KPa 7.0 m/s (at 3000 rpm)
Waste corn oil was blended with petroleum diesel fuel and was tested in coated diesel engine. Some of important properties of corn oil, B15, B35, B65 blend fuels and diesel fuel were presented in Table 3. The test engine's piston surface with combustion chamber and both exhaust and intake valves were coated with a ZrO2 layer. The photo of coated and uncoted forms of the mentioned parts of the test engine was presented in Fig. 2. According to the piston stress analysis presented in Figs. 3 and 4, the maximum piston surface temperature occurs at the areas surrounding the edges of combustion chamber. The coated test engine was dismantled after 100 h of engine operation at conditions of 1500 rpm and full load. The photos of combustion chamber, piston surface and both exhaust and intake valves were taken and presented in Figs. 5 and 6. As can be seen in Fig. 5, there were no abnormalities on the coating layer on combustion chamber parts after 100 h of engine operation. However, the surface of the piston was seen to have minor cracks only on the coating layer surroundings of the edges of combustion chamber. When both two figures were compared, the surface temperature of piston was increased with coating processes. Accordingly, cracks occurred at the areas surrounding the edges of combustion chamber. There was neither a crack nor an abnormality at the remaining parts on piston surface coating layer.
Table 2 Technical properties of the gas analyzing device. Parameter
Measuring range
Precision
HC CO2 CO Smoke NOx
0–20,000 ppm %0–21 %0–10.5 0…99.99% 0–10,000 ppm
1 ppm %0.1 %0.001 %1 1 ppm
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Table 3 Technical properties of diesel fuel, corn oil, and blend fuels. Fuel
Heating value kJ.kg− 1
Density g.cm− 3 (15 °C)
Flash point ( °C)
Viscosity mm2.sn− 1 (40 °C)
Cetane index
Diesel fuel Waste corn oil B15 B35 B65
42,440 39,680 42,200 41,750 41,160
0.836 0.925 0.845 0.856 0.880
72 285 94 135 173
2.96 28 5,76 10,6 16,21
47 51 47 49 50
The valve surface was pictured after 100 h of coated engine operation and presented in Fig. 6. As can be seen in Fig. 6, there was no any crack on the coating layer on the valves surfaces. 3. Engine test results and discussion Power curves of test fuel usage in coated engine operation and uncoated engine with normal diesel fuel operation were presented in Fig. 7. The highest power values were obtained for D2 fuel in coated engine for at all the engine speeds. All the vegetable oil blends were used in the coated engine without any problems in engine operation and no abnormalities occurred during the tests. The power values of the oil blends in coated engine were almost the same with the values of diesel fuel values in the uncoated engine operation. Therefore the main purpose of the present work is seen to have been achieved as the performance of the engine was improved. Namely, power values obtained from vegetable oil blends were increased probably due to the hotter in-cylinder combustion environment which helps to better vaporization of fuel drops and resulting in a shorter ignition delay and thus better combustion. The highest power values were obtained for all of test fuels at 2500 rpm engine speed. After the mentioned speed of the engine operation power values for the entire test fuels were sharply decreased. The main reasons for such decrease are thought to be the decrease in volumetric efficiency and increase in friction losses in engine. The variation of torque values with engine speed for different fuels in coated engine operation and uncoated engine diesel operation is illustrated in Fig. 8. At medium and higher engine speed the highest torque values were obtained for coated diesel operation. As can be seen in Fig. 8, at the 1250 rpm and 1500 rpm engine speed the torque values for B35 operation in coated engine were higher than those for other fuels and coated diesel operation as well. At lower speeds of engine the torque values obtained for D2 operation in uncoated diesel engine were lowest among all of the test fuels. If all of torque values for all of test fuels in every condition are taken into consideration, it will be seen that the D2 operation in coated engine has resulted in higher torque values and the torque values for oil–diesel blends increased and reached to normal diesel engine operation.
The variation of brake specific fuel consumption values with engine speed for different fuels in coated engine operation and uncoated engine diesel operation is illustrated in Fig. 9. At medium and higher engine speeds the lowest brake specific fuel consumption values were obtained for diesel fuel in coated engine test. The brake specific fuel consumption values of the oil blends in coated engine were almost the same with the values of diesel fuel values in the uncoated engine operation. Besides, brake specific fuel consumption values for all test fuels were quite similar at 1000 rpm and 1500 rpm engine speeds. As can be seen in Fig. 9, the engine performance can be said to have been improved with coating the mentioned parts of combustion chamber. HC and CO emissions are main products of incomplete combustion [11]. CO emission variation for test fuels with engine speed is presented in Fig. 10. As can be expected the CO emission values of vegetable oil–diesel blends were quite lower than those obtained for diesel fuel. At engine speed of 2750 rpm the CO emissions were strictly reduced for diesel fuel operation in coated engine. Besides, at higher speeds of engine CO emissions were quite lower for blend fuels in coated engine. Almost no CO emissions were measured at 2500 rpm of coated engine operation with B35 and B65 blend fuels. The main reason is considered to that the increased engine speed caused to increased air movements in the engine cylinder which lead to more homogeneous air–fuel charge and thus resulted in an improved combustion and consequently lowered CO emissions. Therefore, when the engine speed increased CO emissions were decreased for all of test fuels, especially B35 and B65 fuels.
Fig. 2. Coated and uncoated piston surface with combution chamber and both valves.
Fig. 4. Temperature distribution of ceramic coating steel piston [10].
Fig. 3. Temperature distribution conventional steel piston [10].
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Fig. 5. The combustion chamber and piston surface after 100 h of engine operation.
Fig. 8. Variation of engine torque with engine speed for test fuels with coated engine operation.
Besides CO emissions, hydrocarbons, which are known as organic emissions, are also the consequence of incomplete combustion of fuels. The level of unburned hydrocarbons in the exhaust gases is generally specified in terms of the total unburned hydrocarbon concentration expressed in parts per million (ppm) carbon atoms [12]. HC emissions for fuels that were used in coated engine tests and for uncoated diesel fuel operation with different engine speeds is presented in Fig. 11. The HC emissions obtained for vegetable oil blends were considerably lower than that of standard diesel fuel in both coated and uncoated diesel engine operation. However, HC emissions
obtained with coated engine D2 operation were lower than those obtained with normal D2 operation, as can be seen in Fig. 11. When engine speed was increased HC emissions decreased for all of test fuels. For vegetable oil blends HC emission were considerably lower and almost no HC emissions were obtained at higher engine speeds. The main reason is considered to that the increased engine speed caused to increased air movements in the engine cylinder which lead to more homogeneous air–fuel charge and thus resulted in an improved combustion and consequently lowered HC emissions.
Fig. 6. The valves surface after 100 h of engine operation.
Fig. 9. Variation of bsfc with engine speed for test fuels with coated engine operation.
Fig. 7. Variation of engine power with engine speed for test fuels with coated engine operation.
Fig. 10. Variation of CO emissions with engine speed for test fuels with coated engine operation.
B. İşcan, H. Aydın / Fuel Processing Technology 98 (2012) 59–64
Fig. 11. Variation of HC emissions with engine speed for test fuels with coated engine operation.
Therefore, when the engine speed increased HC emissions decreased for all of test fuels, especially B35 and B65 fuels. As the reaction temperature increases and with the increasing of reaction time at this high temperature, the concentration of NOx emissions becomes larger [11]. Variation of NOx emission versus engine speed for all test fuels used in coated engine and uncoated D2 fuel operation is presented in Fig. 12. The lowest NOx emissions were obtained for uncoated D2 operation in all of engine operation conditions. When the test engine was coated NOx emissions were increased for D2 operation. The main reason is considered to be the increased in-cylinder temperature for coated diesel engine. The NOx emissions for vegetable oil–diesel blend were generally higher than those for diesel fuel operation. It is considered to be due to the increased O2 content which led to higher combustion temperature and more complete combustion. When engine speed was increased NOx emission for all the test fuels were also increased probably due to the improved combustion with improved more homogenous air– fuel mixture. Fig. 13 shows the variation of smoke opacity with engine speed for B15, B35, B65, coated D2 and normal D2 engine operation. Smoke opacity is important because it gives an indication of the concentration of pollutants leaving a smokestack. Smoke level for vegetable oil blends was always lower than those of both coated and normal diesel engine operation. Besides, the smoke opacity level was decreased with insulation engine combustion chamber. When engine speed was increased smoke opacity level for all the test fuel was simultaneously decreased. Fig. 14 shows the CO2 variation for test fuels in coated engine and uncoated diesel operation with change in engine speed. At higher engine speeds CO2 emissions were higher for all test fuels. This may be
Fig. 12. Variation of NOx emissions with engine speed for test fuels with coated engine operation.
63
Fig. 13. Variation of smoke opacity with engine speed for test fuels with coated engine operation.
Fig. 14. Variation of CO2 emissions with engine speed for test fuels with coated engine operation.
due to the homogenously improved air–fuel mixture at higher speeds of engine. Besides, CO2 emissions were generally higher for vegetable oil–diesel blends probably due to improved combustion thanks to higher oxygen inherently contended in vegetable oil. 4. Conclusions In the present study, the usability of a waste vegetable oil in a conventional diesel engine and a thermally insulated diesel engine was experimentally investigated and compared with each other. Waste vegetable oil was blended with standard diesel fuel to reduce viscosity. Then the blend fuels were tested in a coated diesel engine. No abnormalities were observed during engine operation. Comparisons were made in the view of engine performance parameters and exhaust emissions characteristics. The surfaces of the engine piston and both intake and exhaust valves were coated with ZrO2 layer in order to make the combustion chamber insulated. Thus heat transfer through the combustion chamber was aimed to be reduced with the purpose of increasing the thermal efficiency and performance of the engine and also maintain the usability of waste vegetable oil in diesel engines. The most important obtained results were presented below; — There were no abnormalities on the coating layer on the combustion chamber after 100 h of engine operation. However, the surface of the piston was seen to have minor cracks only on the coating layer surroundings of the edges of combustion chamber. — Therefore the main purpose of the present work is seen to have been achieved as the performance of the engine was improved.
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Also, torque values of test engine were increased accordingly in coated engine. The brake specific fuel consumption values of the oil blends in coated engine were almost the same with the values of diesel fuel values in the uncoated engine operation. Thus usability of vegetable oils was increased in diesel engine. — CO emissions were quite lower for blend fuels in coated engine. The HC emissions obtained for vegetable oil blends were considerably lower than that of standard diesel fuel in both coated and uncoated diesel engine operation. However, HC emissions obtained with coated engine diesel operation were lower than those obtained with uncoated diesel operation. When the test engine was coated NOx emissions were increased for D2 operation in comparison to normal engine diesel operation. The main reason is considered to be the increased in-cylinder temperature for coated diesel engine. The NOx emissions for vegetable oil–diesel blend were generally higher than those for diesel fuel operation. Smoke level for vegetable oil blends was always lower than those of both coated and normal diesel engine operation References [1] S. Jaichandar and P. Tamilporai. Low Heat Rejection Engines – An Overview, SAE TECHNICAL APER SERIES. 2003–01–0405.
[2] T. Hejwowski, A. Weronski, The effect of thermal barrier coatings on diesel engine performance, Vacuum 65 (2002) 427. [3] K. Toyama, T. Yoshimitsu, T. Nishiyama, Heat insulated turbo compound engine, SAE Transactions 92 (1983) 3.1086. [4] A.C. Alkidas, Performance and emissions achievements with an uncooled heavy duty, single cylinder diesel engine, SAE 890141 (1989). [5] A.C. Alkidas, Experiments with an uncooled single cylinder open chamber diesel, SAE Paper, vol. 870020, 1987. [6] A. Uzun, I. Cevik, M. Akcil, Effects of thermal barrier coating material on a turbocharged diesel engine performance, Surface and Coatings Technology 116–119 (1999) 505. [7] X. Sun, W. Wang, R. Bata, Performance evaluation of low heat rejection engines, ASME Transactions 116 (1994) 758e64. [8] W.K. Cheng, V.M. Wong, F. Gao, Heat transfer measurement comparisons in insulated and non-insulated diesel engines, SAE Transactions, 1989 Paper No.890570. [9] D.W. Dickey, The effect of insulated combustion chamber surfaces on direct injected diesel engine performance, emissions and combustion, SAE Transactions, 1989 Paper No. 890292. [10] Ekrem Buyukkaya, Muhammet Cerit, Thermal analysis of a ceramic coating diesel engine piston using 3-D finite element method, Surface and Coatings Technology 202 (2007) 398–402. [11] Cumali İlkılıç, Hüseyin Aydın, Fuel production from waste vehicle tires by catalytic pyrolysis and its application in a diesel engine, Fuel Processing Technology 92 (2011) 1129–1135. [12] J.B. Heywood, Internal combustion engine fundamentals, McGraw Hill, New York, 1988.
Contents lists available at SciVerse ScienceDirect
Fuel Processing Technology journal homepage: www.elsevier.com/locate/fuproc
Improving the usability of vegetable oils as a fuel in a low heat rejection diesel engine Bahattin İşcan a,⁎, Hüseyin Aydın b a b
Department of Mechanics, Vocational School of Higher Education, Batman University, Batman 72060, Turkey Department of Automotive, Vocational School of Higher Education, Batman University, Batman 72060, Turkey
a r t i c l e
i n f o
Article history: Received 22 November 2011 Received in revised form 1 February 2012 Accepted 2 February 2012 Available online 25 February 2012 Keywords: Low heat rejection engine Vegetable oil Ceramic coating Diesel engine
a b s t r a c t Usability of a waste vegetable oil in coated diesel engines was experimentally investigated. Waste corn oil was blended with petroleum diesel fuel by ratios of 15% corn oil to %85 diesel fuel (B15), 35% corn oil to %65 diesel fuel (B35) and 65% corn oil to %35 diesel fuel (B65). The surfaces of the engine piston and both intake and exhaust valves were coated with ZrO2 layer in order to make the combustion chamber insulated. Thus heat transfer through the combustion chamber was aimed to be reduced with the purpose of increasing the thermal efficiency and performance of the engine and also maintain the usability of vegetable oil in diesel engines. B15, B35, B65 and standard diesel fuels were used in the coated test engine. Performance parameters and exhaust emissions characteristics of all the above mentioned fuels were clarified and compared with uncoated engine test values of normal diesel fuel. It is believed that the main purpose of this study has been achieved as the engine performance parameters such as power and torque of the engine were increased with simultaneous decreases in the brake specific fuel consumption (bsfc). Besides, many of exhaust emission parameters such as CO, HC, and smoke opacity were decreased. © 2012 Elsevier B.V. All rights reserved.
1. Introduction Availability of energy sources, energy utilization and accompanied problems such as, environmental pollution and sustainability are forming a good part of main research topics of scientific world. Diesel engine studies such as fuel availability, alternative fuel investigation and reduction of emissions are crucially ongoing. Diesel engines generally have better fuel consumption characteristics than gasoline engines. Besides, theoretically if the heat rejection can be reduced, then the thermal efficiency will be improved, at least up to the limit set by the second law of thermodynamics [1]. Low heat rejection engines aim to do this by reducing the heat transferred to the coolant. A review was presented in Ref. [1] and it concluded that many studies have been carried out on low heat rejection diesel engine performance but much more studies are needed to overcome the practical problems. Besides, different types of fuel or additives can be researched by means of utilizing them in diesel engines. 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 the exhaust gases, which could be also utilized [2,3]. Ceramic materials have a higher thermal durability than metals.
⁎ Corresponding author. E-mail addresses: [email protected] (B. İşcan), [email protected] (H. Aydın). 0378-3820/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2012.02.001
Therefore, they are not required to cool as fast as metals. Ceramic materials with low thermal conductivity can be used to control temperature distribution and heat flow in a structure [4–6]. Thermal barrier coatings can provide higher thermal efficiencies of the engine thus improve combustion and reduce emissions. Besides, these materials show better wear characteristics than conventional materials. It was reported that combustion characteristics of LHR diesel engines were different from standard diesel engines in four ways [7]: (a) Ignition delay period shortens; (b) diffusion burning period increases while premixed burning period decreases; (c) total combustion duration increases; (d) heat release rate in diffusion burning period decreases. In spite of the fact that the use of LHR engines is found to be promising, many of the reported studies showed contradictory results. Most of the researchers have reported that insulation can decrease heat transfer, increase thermal efficiency and improve energy availability in the exhaust. However, contrary to the above presentations some experimental studies showed that there was little or no improvement in thermal efficiency [8–9]. Different materials such as aluminum, silicon nitride, silicon carbide, magnesium silicate, molybdenum, and some other ceramic materials have been used to make a LHR engine. In the present study, the usability of waste vegetable oil in a conventional diesel engine and a thermally insulated diesel engine was experimentally investigated and compared with each other. The surfaces of the engine piston and both intake and exhaust valves were coated with ZrO2 layer in order to make the combustion chamber insulated.
B. İşcan, H. Aydın / Fuel Processing Technology 98 (2012) 59–64
60
Diesel Fuel Tank
Test Fuel Tank
Mixer
Exhaust Gas Analyzer
Dynamometer Control Panel Air Flow
CAMERA SELECT
1 2 3 4 5 6 7 8
NOx
2
4
5
3 6
7
8
9
0
9 10 11 12 13 14 15 16
CO, HC, CO2
1
Silencer
Air mass Speed Temperature Load
Dynamometer Coupling
Smoke Analyzer
Engine
Fig. 1. Schematic diagram of experimental setup.
2. Engine test materials and experimental procedure Performance and emission tests were performed at the engine test laboratory of Automotive Department at University of Batman. Schematic diagram of experimental setup was presented in Fig. 1. A BT140 model hydraulic dynamometer was used for performance tests. The engine test specifications were presented in Table 1. Exhaust emission test was carried out with a Capellec CAP 3200 model emission analysis device. Technical properties of emission test device were given in Table 2. The fuel consumption was measured in burettes with 50 and 100 ml volumes and a stopwatch. The brake specific fuel consumption was calculated with the following equation. be ¼
V_ :ρ:3600 Pe
ð1Þ
Where “be” is the brake specific fuel consumption as g/kWh, “V_ ” is the flow rate of the fuel as cm 3/sn, “ρ” is the density of the fuel as g.cm − 3 and “Pe” is the brake power as kW. Table 1 Technical specifications of the test engine. Type
Rainbow-186 diesel
Injection system Cylinder number Stroke volume Compression ratio Maximum power Maximum engine speed Cooling system Injection pressure Mean effective pressure (Mep) Medium piston speed
Direct injection 1 406 cc 18/1 10 HP 3600 rpm ±20 Air cooling 19.6 ± 0.49 MPa (200 ± 5 Kgf/cm2) 561.6 KPa 7.0 m/s (at 3000 rpm)
Waste corn oil was blended with petroleum diesel fuel and was tested in coated diesel engine. Some of important properties of corn oil, B15, B35, B65 blend fuels and diesel fuel were presented in Table 3. The test engine's piston surface with combustion chamber and both exhaust and intake valves were coated with a ZrO2 layer. The photo of coated and uncoted forms of the mentioned parts of the test engine was presented in Fig. 2. According to the piston stress analysis presented in Figs. 3 and 4, the maximum piston surface temperature occurs at the areas surrounding the edges of combustion chamber. The coated test engine was dismantled after 100 h of engine operation at conditions of 1500 rpm and full load. The photos of combustion chamber, piston surface and both exhaust and intake valves were taken and presented in Figs. 5 and 6. As can be seen in Fig. 5, there were no abnormalities on the coating layer on combustion chamber parts after 100 h of engine operation. However, the surface of the piston was seen to have minor cracks only on the coating layer surroundings of the edges of combustion chamber. When both two figures were compared, the surface temperature of piston was increased with coating processes. Accordingly, cracks occurred at the areas surrounding the edges of combustion chamber. There was neither a crack nor an abnormality at the remaining parts on piston surface coating layer.
Table 2 Technical properties of the gas analyzing device. Parameter
Measuring range
Precision
HC CO2 CO Smoke NOx
0–20,000 ppm %0–21 %0–10.5 0…99.99% 0–10,000 ppm
1 ppm %0.1 %0.001 %1 1 ppm
B. İşcan, H. Aydın / Fuel Processing Technology 98 (2012) 59–64
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Table 3 Technical properties of diesel fuel, corn oil, and blend fuels. Fuel
Heating value kJ.kg− 1
Density g.cm− 3 (15 °C)
Flash point ( °C)
Viscosity mm2.sn− 1 (40 °C)
Cetane index
Diesel fuel Waste corn oil B15 B35 B65
42,440 39,680 42,200 41,750 41,160
0.836 0.925 0.845 0.856 0.880
72 285 94 135 173
2.96 28 5,76 10,6 16,21
47 51 47 49 50
The valve surface was pictured after 100 h of coated engine operation and presented in Fig. 6. As can be seen in Fig. 6, there was no any crack on the coating layer on the valves surfaces. 3. Engine test results and discussion Power curves of test fuel usage in coated engine operation and uncoated engine with normal diesel fuel operation were presented in Fig. 7. The highest power values were obtained for D2 fuel in coated engine for at all the engine speeds. All the vegetable oil blends were used in the coated engine without any problems in engine operation and no abnormalities occurred during the tests. The power values of the oil blends in coated engine were almost the same with the values of diesel fuel values in the uncoated engine operation. Therefore the main purpose of the present work is seen to have been achieved as the performance of the engine was improved. Namely, power values obtained from vegetable oil blends were increased probably due to the hotter in-cylinder combustion environment which helps to better vaporization of fuel drops and resulting in a shorter ignition delay and thus better combustion. The highest power values were obtained for all of test fuels at 2500 rpm engine speed. After the mentioned speed of the engine operation power values for the entire test fuels were sharply decreased. The main reasons for such decrease are thought to be the decrease in volumetric efficiency and increase in friction losses in engine. The variation of torque values with engine speed for different fuels in coated engine operation and uncoated engine diesel operation is illustrated in Fig. 8. At medium and higher engine speed the highest torque values were obtained for coated diesel operation. As can be seen in Fig. 8, at the 1250 rpm and 1500 rpm engine speed the torque values for B35 operation in coated engine were higher than those for other fuels and coated diesel operation as well. At lower speeds of engine the torque values obtained for D2 operation in uncoated diesel engine were lowest among all of the test fuels. If all of torque values for all of test fuels in every condition are taken into consideration, it will be seen that the D2 operation in coated engine has resulted in higher torque values and the torque values for oil–diesel blends increased and reached to normal diesel engine operation.
The variation of brake specific fuel consumption values with engine speed for different fuels in coated engine operation and uncoated engine diesel operation is illustrated in Fig. 9. At medium and higher engine speeds the lowest brake specific fuel consumption values were obtained for diesel fuel in coated engine test. The brake specific fuel consumption values of the oil blends in coated engine were almost the same with the values of diesel fuel values in the uncoated engine operation. Besides, brake specific fuel consumption values for all test fuels were quite similar at 1000 rpm and 1500 rpm engine speeds. As can be seen in Fig. 9, the engine performance can be said to have been improved with coating the mentioned parts of combustion chamber. HC and CO emissions are main products of incomplete combustion [11]. CO emission variation for test fuels with engine speed is presented in Fig. 10. As can be expected the CO emission values of vegetable oil–diesel blends were quite lower than those obtained for diesel fuel. At engine speed of 2750 rpm the CO emissions were strictly reduced for diesel fuel operation in coated engine. Besides, at higher speeds of engine CO emissions were quite lower for blend fuels in coated engine. Almost no CO emissions were measured at 2500 rpm of coated engine operation with B35 and B65 blend fuels. The main reason is considered to that the increased engine speed caused to increased air movements in the engine cylinder which lead to more homogeneous air–fuel charge and thus resulted in an improved combustion and consequently lowered CO emissions. Therefore, when the engine speed increased CO emissions were decreased for all of test fuels, especially B35 and B65 fuels.
Fig. 2. Coated and uncoated piston surface with combution chamber and both valves.
Fig. 4. Temperature distribution of ceramic coating steel piston [10].
Fig. 3. Temperature distribution conventional steel piston [10].
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Fig. 5. The combustion chamber and piston surface after 100 h of engine operation.
Fig. 8. Variation of engine torque with engine speed for test fuels with coated engine operation.
Besides CO emissions, hydrocarbons, which are known as organic emissions, are also the consequence of incomplete combustion of fuels. The level of unburned hydrocarbons in the exhaust gases is generally specified in terms of the total unburned hydrocarbon concentration expressed in parts per million (ppm) carbon atoms [12]. HC emissions for fuels that were used in coated engine tests and for uncoated diesel fuel operation with different engine speeds is presented in Fig. 11. The HC emissions obtained for vegetable oil blends were considerably lower than that of standard diesel fuel in both coated and uncoated diesel engine operation. However, HC emissions
obtained with coated engine D2 operation were lower than those obtained with normal D2 operation, as can be seen in Fig. 11. When engine speed was increased HC emissions decreased for all of test fuels. For vegetable oil blends HC emission were considerably lower and almost no HC emissions were obtained at higher engine speeds. The main reason is considered to that the increased engine speed caused to increased air movements in the engine cylinder which lead to more homogeneous air–fuel charge and thus resulted in an improved combustion and consequently lowered HC emissions.
Fig. 6. The valves surface after 100 h of engine operation.
Fig. 9. Variation of bsfc with engine speed for test fuels with coated engine operation.
Fig. 7. Variation of engine power with engine speed for test fuels with coated engine operation.
Fig. 10. Variation of CO emissions with engine speed for test fuels with coated engine operation.
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Fig. 11. Variation of HC emissions with engine speed for test fuels with coated engine operation.
Therefore, when the engine speed increased HC emissions decreased for all of test fuels, especially B35 and B65 fuels. As the reaction temperature increases and with the increasing of reaction time at this high temperature, the concentration of NOx emissions becomes larger [11]. Variation of NOx emission versus engine speed for all test fuels used in coated engine and uncoated D2 fuel operation is presented in Fig. 12. The lowest NOx emissions were obtained for uncoated D2 operation in all of engine operation conditions. When the test engine was coated NOx emissions were increased for D2 operation. The main reason is considered to be the increased in-cylinder temperature for coated diesel engine. The NOx emissions for vegetable oil–diesel blend were generally higher than those for diesel fuel operation. It is considered to be due to the increased O2 content which led to higher combustion temperature and more complete combustion. When engine speed was increased NOx emission for all the test fuels were also increased probably due to the improved combustion with improved more homogenous air– fuel mixture. Fig. 13 shows the variation of smoke opacity with engine speed for B15, B35, B65, coated D2 and normal D2 engine operation. Smoke opacity is important because it gives an indication of the concentration of pollutants leaving a smokestack. Smoke level for vegetable oil blends was always lower than those of both coated and normal diesel engine operation. Besides, the smoke opacity level was decreased with insulation engine combustion chamber. When engine speed was increased smoke opacity level for all the test fuel was simultaneously decreased. Fig. 14 shows the CO2 variation for test fuels in coated engine and uncoated diesel operation with change in engine speed. At higher engine speeds CO2 emissions were higher for all test fuels. This may be
Fig. 12. Variation of NOx emissions with engine speed for test fuels with coated engine operation.
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Fig. 13. Variation of smoke opacity with engine speed for test fuels with coated engine operation.
Fig. 14. Variation of CO2 emissions with engine speed for test fuels with coated engine operation.
due to the homogenously improved air–fuel mixture at higher speeds of engine. Besides, CO2 emissions were generally higher for vegetable oil–diesel blends probably due to improved combustion thanks to higher oxygen inherently contended in vegetable oil. 4. Conclusions In the present study, the usability of a waste vegetable oil in a conventional diesel engine and a thermally insulated diesel engine was experimentally investigated and compared with each other. Waste vegetable oil was blended with standard diesel fuel to reduce viscosity. Then the blend fuels were tested in a coated diesel engine. No abnormalities were observed during engine operation. Comparisons were made in the view of engine performance parameters and exhaust emissions characteristics. The surfaces of the engine piston and both intake and exhaust valves were coated with ZrO2 layer in order to make the combustion chamber insulated. Thus heat transfer through the combustion chamber was aimed to be reduced with the purpose of increasing the thermal efficiency and performance of the engine and also maintain the usability of waste vegetable oil in diesel engines. The most important obtained results were presented below; — There were no abnormalities on the coating layer on the combustion chamber after 100 h of engine operation. However, the surface of the piston was seen to have minor cracks only on the coating layer surroundings of the edges of combustion chamber. — Therefore the main purpose of the present work is seen to have been achieved as the performance of the engine was improved.
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Also, torque values of test engine were increased accordingly in coated engine. The brake specific fuel consumption values of the oil blends in coated engine were almost the same with the values of diesel fuel values in the uncoated engine operation. Thus usability of vegetable oils was increased in diesel engine. — CO emissions were quite lower for blend fuels in coated engine. The HC emissions obtained for vegetable oil blends were considerably lower than that of standard diesel fuel in both coated and uncoated diesel engine operation. However, HC emissions obtained with coated engine diesel operation were lower than those obtained with uncoated diesel operation. When the test engine was coated NOx emissions were increased for D2 operation in comparison to normal engine diesel operation. The main reason is considered to be the increased in-cylinder temperature for coated diesel engine. The NOx emissions for vegetable oil–diesel blend were generally higher than those for diesel fuel operation. Smoke level for vegetable oil blends was always lower than those of both coated and normal diesel engine operation References [1] S. Jaichandar and P. Tamilporai. Low Heat Rejection Engines – An Overview, SAE TECHNICAL APER SERIES. 2003–01–0405.
[2] T. Hejwowski, A. Weronski, The effect of thermal barrier coatings on diesel engine performance, Vacuum 65 (2002) 427. [3] K. Toyama, T. Yoshimitsu, T. Nishiyama, Heat insulated turbo compound engine, SAE Transactions 92 (1983) 3.1086. [4] A.C. Alkidas, Performance and emissions achievements with an uncooled heavy duty, single cylinder diesel engine, SAE 890141 (1989). [5] A.C. Alkidas, Experiments with an uncooled single cylinder open chamber diesel, SAE Paper, vol. 870020, 1987. [6] A. Uzun, I. Cevik, M. Akcil, Effects of thermal barrier coating material on a turbocharged diesel engine performance, Surface and Coatings Technology 116–119 (1999) 505. [7] X. Sun, W. Wang, R. Bata, Performance evaluation of low heat rejection engines, ASME Transactions 116 (1994) 758e64. [8] W.K. Cheng, V.M. Wong, F. Gao, Heat transfer measurement comparisons in insulated and non-insulated diesel engines, SAE Transactions, 1989 Paper No.890570. [9] D.W. Dickey, The effect of insulated combustion chamber surfaces on direct injected diesel engine performance, emissions and combustion, SAE Transactions, 1989 Paper No. 890292. [10] Ekrem Buyukkaya, Muhammet Cerit, Thermal analysis of a ceramic coating diesel engine piston using 3-D finite element method, Surface and Coatings Technology 202 (2007) 398–402. [11] Cumali İlkılıç, Hüseyin Aydın, Fuel production from waste vehicle tires by catalytic pyrolysis and its application in a diesel engine, Fuel Processing Technology 92 (2011) 1129–1135. [12] J.B. Heywood, Internal combustion engine fundamentals, McGraw Hill, New York, 1988.