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Biodiesel from safflower oil and its application in a diesel engine
Fuel Processing Technology 92 (2011) 356–362
Contents lists available at ScienceDirect
Fuel Processing Technology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / f u p r o c
Biodiesel from safflower oil and its application in a diesel engine Cumali Ilkılıç a, Selman Aydın b, Rasim Behcet b,⁎, Hüseyin Aydin b a b
Department of Automotive, Faculty of Technical Education, Fırat University, Elazığ 23119, Turkey Department of Automotive, Faculty of Technical Education, Batman University, Batman 72060, Turkey
a r t i c l e
i n f o
Article history: Received 3 September 2010 Received in revised form 23 September 2010 Accepted 25 September 2010 Available online 20 October 2010 Keywords: Diesel engine Biodiesel Alternative fuel Safflower oil
a b s t r a c t Safflower seed oil was chemically treated by the transesterification reaction in methyl alcohol environment with sodium hydroxide (NaOH) to produce biodiesel. The produced biodiesel was blended with diesel fuel by 5% (B5), 20% (B20) and 50% (B50) volumetrically. Some of important physical and chemical fuel properties of blend fuels, pure biodiesel and diesel fuel were determined. Performance and emission tests were carried out on a single cylinder diesel engine to compare biodiesel blends with petroleum diesel fuel. Average performance reductions were found as 2.2%, 6.3% and 11.2% for B5, B20 and B50 fuels, respectively, in comparison to diesel fuel. These reductions are low and can be compensated by a slight increase in brake specific fuel consumption (Bsfc). For blends, Bsfcs were increased by 2.8%, 3.9% and 7.8% as average for B5, B20 and B50, respectively. Considerable reductions were recorded in PM and smoke emissions with the use of biodiesel. CO emissions also decreased for biodiesel blends while NOx and HC emissions increased. But the increases in HC emissions can be neglected as they have very low amounts for all test fuels. It can be concluded that the use of safflower oil biodiesel has beneficial effects both in terms of emission reductions and alternative petroleum diesel fuel. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Two main concepts that have ever been taken into account in the investigation and development of compression ignition (CI) engine fuels are performance and emissions. Since it was realized that the petrol is not an infinitive source, sustainability, renewability and availability in any kind of fuel have gained a huge attention at the present. At present vegetable oils can be considered as candidates in this subject. However, vegetable oils can not be directly used in CI engines in pure or raw form due to their low volatility and diffusibility but higher viscosity and density. A study was carried out to investigate the performance and emission characteristics of some vegetable oils including linseed oil, mahua oil, rice bran oil and biodiesel obtained from linseed oil, in a stationary diesel engine and to compare them with diesel fuel [1]. The linseed oil, mahua oil, rice bran oil and linseed oil biodiesel were blended with diesel fuel in different proportions. Engine tests were performed by using all these blends of linseed, mahua, rice bran, and biodiesel. It was found that all of the vegetable oils posed operational and durability problems when subjected to long-term usage in CI engine. These problems were attributed to high viscosity, low volatility and polyunsaturated characteristics of vegetable oils.
⁎ Corresponding author. Tel.: + 90 488 217 3664; fax: + 90 4882157201. E-mail addresses: cilkilic@firat.edu.tr (C. Ilkılıç), [email protected] (S. Aydın), [email protected] (R. Behcet), [email protected] (H. Aydin). 0378-3820/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2010.09.028
However, these problems were not observed for biodiesel blends. Hence, the process of transesterification was found to be an effective method of reducing vegetable oil viscosity and eliminating operational and durability problems. In an experimental study, the performance and emissions of cottonseed oil methyl ester in a diesel engine were investigated [2]. It was concluded that with the increase of biodiesel percentage in the blend, the obtained power and torque decreased with a small increase in the brake specific fuel consumption. However, the exhaust emissions fairly reduced. In another work, the effects of cottonseed oil methyl esters on engine performance in a single cylinder diesel engine have been studied [3]. The experiments showed that there was little or no significant difference between the torque and power output of cotton seed oil methyl ester and diesel fuel usage especially at medium and higher speeds of the engine. Yücesu and Ilkiliç [4] reported reductions of 3–8%, in torque and power when they used pure cottonseed biodiesel, while they declared 5% reduction in heating value for biodiesel. They did not use the loss of heating value to justify the power loss, but difficulties in the fuel atomization, instead. A review study was made by Lapuerta et al. [5] and they reported that there were also some publications reporting surprising increases in rated power or torque when using biodiesel. Altiparmak et al. [6] measured a 6.1% increase in maximum torque when they used a blend with 70% tall-oil biodiesel, with respect to what was measured with diesel fuel. Similarly, Usta [7] observed an
C. Ilkılıç et al. / Fuel Processing Technology 92 (2011) 356–362
increase in torque and power when using biodiesel from tobacco seed oil (with a lower heating value of 39.8 MJ/kg) in different blends with diesel fuel in an indirect injection diesel engine at 1500 and 3000 rpm. The highest values of torque and power were obtained with a 17.5% blend, despite the reduced heating value of biodiesel. It was also reported in the review [5] that there were a consensus on NOx increase with the use of biodiesel, while sharp reductions in PM and CO emissions were generalized. When blends of biodiesel and diesel fuel were used in diesel engines, a significant reduction in hydrocarbons (HC) and particulate matter (PM) were observed but NOx emissions were found to have increased. In general, engine performance and power remained almost unchanged [8–11]. The various characteristics of bio-oils acquired under different pyrolysis conditions from safflower oil were identified [12]. Some chemical and physical fuel characteristics of safflower obtained biofuel were determined. It was found that the bio-oils obtained from safflower were an environmentally friendly feedstock candidate for biofuels and chemicals. In the present study, safflower seed oil was chemically processed by the transesterification reaction under methanol and NaOH environment to obtain biodiesel. The obtained biodiesel was then used in a single cylinder and four strokes diesel engine. The performance and emission tests were experimentally performed to investigate the biodiesel behavior as an alternative diesel fuel.
2. Material and method
357
Table 1 Technical specifications of the test engine. Type Injection system Cylinder number Stroke volume Compression ratio Maximum power Maximum engine speed Cooling system Injection pressure Mean effective pressure (Mep) Medium piston speed
Rainbow-186 diesel 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)
Engine tests were conducted on a BT-140 model hydraulic dynamometer. Technical specifications of the dynamometer and control unit are given in Tables 2 and 3. PM and smoke were measured with MDO 2-LON type gas analyzer and specification of this device is given in Table 4. The CAPELEC CAP 3200 brand exhaust gas analyzer was used to measure emissions of the test fuels. The technical specifications of the device have been presented in the Table 5. An infrared temperature measurement device was used to specify exhaust gas temperature. The technical specifications of the temperature measurement device are presented in the Table 6. The fuel consumption was measured with burettes with 50 and 100 ml volumes and a stopwatch. The Bsfc was calculated with following equation. :
Experiments were carried out in Engine Test Laboratory of Automotive Department of Technical Education Faculty at University of Batman. The schematic diagram of the experimental setup is shown in Fig. 1. Tests were conducted on a single cylinder, four strokes, air cooled diesel engine. Technical specifications of the test engine were given at Table 1.
be =
V d ρd 3600 Pe
ð1Þ :
Where “be” is the brake specific fuel consumption, “V ” is the flow rate of the fuel as cm3/sn, “ρ” is the density of the fuel as g/cm3 and “Pe” is the brake power as g/kWh.
Fig. 1. A schematic diagram of the engine setup.
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Table 2 Technical specifications of dynamometer.
Table 7 The fuel properties of pure biodiesel (B100) and raw safflower.
Brake motor Maximum brake power Maximum speed Maximum torque Capacity of load cell Water consumption for maximum power Brake water pressure Brake control type Electricity requirement
BT-140 50 HP 7500 rpm 250 Nm 1000 N V max. 0.75 m³/h 1–2 kg/cm² Slippery propeller 220/380 V. 50 Hz.
Parameters
ASTM test no
Safflower oil
B100
Carbon, % Kinematical viscosity (mm2/s) Heat value (MJ/kg) Density (15 C) (g/ml) Flash point (°C) Cloud point (°C) Cetane index
– D445 D2015 D1298 D93 – D613
67 28 39 0.95 225 -2 -
59.5 5.8 38.122 0.8885 148 -5 56
2.1. Biodiesel production from safflower oil The transesterification process of safflower oil to produce biodiesel is presented by the steps below:
Table 3 Technical specifications of the dynamometer control unit. Model Accuracy Precision Response time Weight measurement Speed measurement Screen type
PC101BMS 0.2% ±1 digit 600 μs Linear (load-cell) Sensor 3 × 6 unit, 7-region LED 2 × 16 character LCD 16 W 0–50 °C 220 ± 5% VAC Printer
Power Operation temperature Operation voltage Output
Table 4 Technical specifications of the PM and smoke detector (MDO 2 – LON). Parameter
Measuring range
Precision
Smoke factor (K, factor) PM, particular matters
0…9.99 1/m 0–70%
0.01 0.5
Table 5 Technical properties of the gas analyzing device. Parameter
Measuring range
Precision
HC CO2 CO O2 NOx
0–20,000 ppm 0–20% 0–15% 0–21.7% 0–5000 ppm
1 ppm 0.1% 0.001% 0.01% 1 ppm
Table 6 The technical specifications of the temperature measurement device. Type Temperature measurement range Laser type Diffusion rate Precision Response time
Raytek Raynger ST4 (−32 ile + 545 °C) (−25 ile + 950 °F) Single point 95% ± 1% 500 μsn
- The oil was heated to 55 °C in a 500 ml vessel. It was kept at this stable temperature. To obtain a homogenous mixture of reactants, a magnetic stirrer was used. The mixture of oil and alcoholcatalyzer was stirred at 1000 rev/min. in the vessel. - The heated safflower oil was filled into a cap. An amount of methyl alcohol equal to 20% of prepared oil was mixed with 0.4% NaOH, volumetrically. The mixture was heated and then stirred between 30 and 40 °C until the NaOH was completely solved and liquefied in the alcohol. Then the mixture of alcohol and NaOH was added to the cap containing safflower oil. - The mixture of oil-alcohol-catalyzer was heated at permanent temperature of 55–65 °C and it was stirred simultaneously at about 1000 rev/min. in the reaction cap for 2 h. - After 2 h of reaction time, the products were filled into a washing and separation funnel. The reaction products were separated into two layers, the top one was biodiesel and the bottom one was glycerol. The biodiesel was separated from glycerol. Then sulphuric acid (H2SO4) was added the biodiesel for depolarization. - The biodiesel was then washed with equal amount of water to separate the probably remained alcohol or catalyst from biodiesel. It was then kept for 4 h in the cap to separate the water. Finally, the biodiesel was heated above 100 °C to remove the remaining water from biodiesel fuel. - The obtained fuel, biodiesel, was added to petroleum diesel fuel volumetrically by 5%, 20% and 50%. The fuel mixtures that obtained from the addition of 5%, 20% and 50% of biodiesel were named here as B5, B20 and B50, respectively. The fuel properties of pure biodiesel and raw safflower oil are presented in the Table 7. Also the properties of B5, B20, B50 and a standard diesel fuel are given in the Table 8. The distillation curves of the fuel blends of safflower oil obtained methyl ester-diesel fuel and diesel fuel are illustrated with the Fig. 2. The distillation curves of test fuels are shown in the Fig. 2. The figure shows the amount of distilled volume versus temperature clarifies that the fuel samples were distilled homogenously, smoothly and gradually with temperature increases. This means the smooth,
Table 8 The properties of B5, B20, B50 and a standard diesel fuel. Parameters
ASTM B5 test no
B20
B50
B100
Diesel fuel
Kinematical viscosity (mm2/s) Heat value (MJ/kg) Density (15 C) (g/ml) Flash point (°C) Cetane index
D445 D2015 D1298 D93 D613
3.3764 41486 0.8482 73 52.82
4.0347 40078 0.8639 82 53.86
5.8068 38122 0.8885 148 56.82
3.6663 43350 0.8435 60 49
3.0738 42345 0.84039 69 46.23
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450
9
400
359
D2
B5
B20
B50
8
Engine power, kW
Temperature °C
350 300 250 200
B5 B10 B20 B50 D2
150 100 50 0%
7
6
5
4
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
3 1000
Distilled volume
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm Fig. 2. The distillation curves of D2, B5, B10, B20 and B50 fuels. Fig. 4. The power variation for the biodiesel blend and diesel fuels with engine speed.
3. Results and discussions 3.1. Engine performance 3.1.1. Engine torque For test fuels, the torque variations with engine speed were illustrated with Fig. 3. The maximum torque values were observed around 1600 rpm of engine, for all test fuels including D2. Similar to the power values, the torque for D2 fuel was higher than those of other fuels. It may be due to the higher calorific value of diesel fuel. Another reason for power and torque decrease for biodiesel blend may be higher viscosity of blend fuels. The average torque values for 35 33
D2
B5
B20
B50
31
Torque, N.m
29 27 25 23 21 19 17 15 1000
1250
1500
1750
2000
2250
2500
2750
3000
D2, B5, B20 and B50 fuels were 28.72 Nm, 28.06 Nm, 27.06 Nm and 25.63 Nm, respectively. The lowest torque value was obtained for B50 fuel for all speeds of engine. 3.1.2. Engine power Fig. 4 shows power variations of the test engine for test fuels. It is clear from the Fig. 4 that the power of D2 fuel was found higher than those obtained for biodiesel blends. For blend fuels, the power decreases were almost linear with biodiesel percentage in the blend. The main reason for power decrease may be lower heating values of blend fuels. However, at lower speeds of engine, the power for D2 was almost the same as B5 fuel. It can be attributed to higher thermal efficiency of the test engine with using biodiesel blends. Because biodiesel fuels have enough time to entirely be burned at lower speeds, the conversion of the fuel into energy was more sufficient. 3.1.3. Brake specific fuel consumption Fig. 5 shows the brake specific fuel consumption (Bsfc) variation with engine speed for D2, B5, B20 and B50 fuels. The highest Bsfc was observed for B50 with all speeds of the engine. On the other hand, the lowest Bsfcs were obtained for diesel fuel. The values of Bsfc's those obtained for B5 and B20 fuels were close to each other. Besides, the values for B5 were fairly lower than that of B50 fuel. Average Bsfcs for D2, B5, B20 and B50 fuels were observed about 315 g/kWh, 333 g/kWh, 357 g/kWh and 375 g/kWh, respectively. The main reason for the
Brake specific fuel consumption, g/kWh
gradual and homogenous evaporation of the fuel in the engine cylinder and crucially important in terms of combustion and performance. It also means that the fuel particles in the cylinder were homogenously, gradually and completely combusted. The Fig. 2 also shows that the distillation properties of the blend fuels were similar to that of diesel fuel. However, the primary distillation temperatures of biodiesel fuels were higher than that of diesel fuel since the biodiesel has higher boiling point than diesel fuel. Contrary to the primary distillation temperature, the final distillation temperature was lowest for B50, among all fuels, which contain higher biodiesel amount than the other fuels. It means that the final boiling point of biodiesel was lower than that of diesel fuel which may have a positive effect on the combustion of biodiesel. This affirmative property, as it will be supported by the results of the emission test in our study, led to a reduction in the HC, PM and smoke emissions in the biodiesel usage.
800 D2 B20
B5 B50
700 600 500 400 300 200 1000
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm
Engine speed, rpm Fig. 3. The torque variation for the biodiesel blend and diesel fuels with engine speed.
Fig. 5. The brake specific fuel consumption variation for the biodiesel blend and diesel fuels with engine speed.
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300
0,06 D2
B5
B20
B50
B20 B5
D2 B50
0,05
250
0,04
K, 1/m
Exhaust gas temperature (C)
350
200 150
0,03 0,02
100 0,01 50 1000
1250
1500
1750
2000
2250
2500
0 1000
Engine speed, rpm Fig. 6. The variation of the exhaust gas temperature for biodiesel blend and diesel fuels with engine speed.
increase in Bsfc for blend fuels is considered to be the lower calorific value biodiesel included in the blend. On the other hand, the loss of heating value of biodiesel can be compensated with higher fuel consumption. However the maximum increase was lower than the loss in heating value and this result implies a certain improvement of thermal efficiency with biodiesel. 3.1.4. Exhaust gas temperature The exhaust temperatures of the engine when using D2, B5, B20 and B50 fuels were presented in the Fig. 6. The exhaust temperature increased almost linearly with the increase in engine speed for all the test fuels. It can be seen clearly in the Fig. 6 that the higher temperature values were obtained for biodiesel blend fuels and the increase was observed the highest for B50 fuel. It can be attributed to the more complete combustion for biodiesel use thanks to the oxygen that was inherently contained in the biodiesel. 3.2. Exhaust emissions 3.2.1. Smoke factor (K Factor) and PM emissions The variation of PM emission and smoke opacity of the test fuels with speed are illustrated with Figs. 7 and 8. The emission device is able to measure total particulate emission generally less than or equal to 10 μm in diameter (PM10). It is clear from figures that both PM and smoke decreased with biodiesel use. Both PM and smoke were decreased in proportion to biodiesel concentration in the blend. Thus the lowest PM and smoke emissions obtained for B50 and then for B20
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm Fig. 8. The variation of the smoke factor for the biodiesel blend and diesel fuels with engine speed.
blends. The results show that biodiesel usage enables to reduce both PM emissions and smoke opacity. The main reason that we have used to explain the reductions of PM emission when using biodiesel can be the oxygen content of the biodiesel molecule which enables more complete combustion and promotes the oxidation of already formed soot. The advantage of fuel-oxygen is thought to be a consequence of its higher accessibility to the flame which leads more complete and diffusive combustion. Another reason that can be given is the different structure of soot particles between biodiesel and diesel fuel which may also favor the oxidation of soot from biodiesel. Diesel particulates consist principally of combustion generated carbonaceous material called soot on which some organic compounds have become absorbed [13]. Soot is a general term that refers to impure carbon restricted to the particles which are the residual pyrolyzed fuel particles resulting from the incomplete combustion of a hydrocarbon. The oxidation velocity of biodiesel soot is up to 6 times higher than that of diesel soot. One more explanation that can be given is that the lower sulphur content of safflower derived biodiesel which prevents sulfate formation which being a significant component of typical diesel PM. The usually lower final boiling point of biodiesel provides lower soot being formed from heavy hydrocarbon fractions unable to vaporize. Among the above mentioned reasons both oxygen content and sulphur content can be seen as significantly effect on both PM emissions and smoke opacity. The lowest PM emissions and smoke opacity values were obtained for B50 fuel with engine operation at any speed. 200
2,5 B20 B5
D2 B5
D2 B50
B20 B50
180
NOx, ppm
PM, %
2
1,5
1
140
120
0,5
0 1000
160
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm Fig. 7. The variation of PM emissions for the biodiesel blend and diesel fuels with engine speed.
100 1000
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm Fig. 9. The variation of NOx emissions for the biodiesel blend and diesel fuels with engine speed.
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50
361
5 B20 B5
D2 B50
D2 B5
4,5
40
B20 B50
4
30
CO, %
HC, ppm
3,5
20
3 2,5 2 1,5
10
1 0,5
0 1000
1250
1500
1750
2000
2250
2500
2750
3000
0 1000
1250
Engine speed, rpm
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm
Fig. 10. The variation of HC emissions for the biodiesel blend and diesel fuels with engine speed.
Fig. 11. The variation of CO emissions for the biodiesel blend and diesel fuels with engine speed.
3.2.2. Nitrogen oxides (NOx) The test results showed an increase in NOx emission when using biodiesel fuel. The obtained increase in NOx emissions was in proportion to the biodiesel concentration in the blend as can be seen in Fig. 9. The lowest NOx emissions were obtained with using diesel fuel and the highest NOx emissions were obtained with B50 fuel. The main reason for NOx increase is the oxygen content of biodiesel which improves combustion thus increases the temperature and resulting NOx production reaction which occurs after 1800 °K. Another argument is the increased cetane numbers of biodiesel which leads to advanced combustion by shortening ignition delay which promotes NOx formation reaction. Since cetane number of biodiesel blends increases in proportion to the concentration of biodiesel in the blend, B50 blend resulted in the highest NOx emission. One more parameter that effects on NOx is iodine number. Biodiesel has higher number of iodine which results in higher NOx emission.
This might have decreased the HC emissions for diesel fuel above those for biodiesel.
3.2.3. Hydrocarbon (HC) The variations of HC emission with engine speed for diesel fuel and biodesel–diesel blends fuels are presented in the Fig. 10. The total unburned hydrocarbons were measured as “ppm” with the gas analyzer. The HC emission which is one of the organic compounds is formed in the result of incomplete combustion. The exhaust gasses contain many different HC compounds. HC emissions fairly increase in the case of richer fuel–air ratios above the stoichiometric ratio. Besides, in the excessively leaned fuel–air ratio conditions, due to incomplete combustion that resulted from the lack of oxygen, HC emissions rapidly increase again. In many cases, the HC emissions for biodiesel have been reported higher than that of diesel fuel [11,14–18]. It can be attributed to the oxygen content in the biodiesel molecule, which leads to a more complete and cleaner combustion. The higher cetane number of biodiesel shortens the combustion delay and thus reduces HC emissions. Another reason may be higher final distillation point of diesel fuel as can be seen in Fig. 10, although biodiesel is less volatile than diesel fuel. This final fraction of the diesel may not be completely vaporized and burnt, thereby increasing HC emissions. In the present study, as can be seen in Fig. 10, the higher HC emissions have been found for B20 and B50 fuels. These surprising results may be due either to the very low HC emissions or to the lower detection limit of the detectors. It was absolutely concluded by the results of this study that the biodiesel had better combustion. It can be seen from the test result for CO, PM emissions and exhaust gas temperature, as well. It can be presented as one more reason for lower HC emission of diesel fuel usage that higher PM emissions of diesel fuel usage might have adsorbed the remaining unburned fuel molecules.
4. Conclusions
3.2.4. Carbon monoxide (CO) As the general trend the CO emissions fairly reduced when substituting diesel fuel with biodiesel and this can be seen in Fig. 11. The lowest CO emissions were found for B50 fuel in average. The decrease in CO emissions for B20 was similar to that for B50. Several reasons can be given for such decrease. Firstly, it may be due to the additional oxygen content in the fuel, which enhances a complete combustion of the fuel, thus reducing CO emissions. Secondly, it can be attributed to the higher cetane number of biodiesel fuel that puts the fuel-rich mixture zone away and improves combustion thus reducing CO emissions. Finally, the advanced injection time of biodiesel use due to molecular structure of biodiesel may also explain the reduction in CO emissions.
In this study, an alternative biodiesel fuel was obtained from safflower seed oil by the transesterification method. Some of important physical and chemical fuel properties of the oil, pure biodiesel and biodiesel blend fuels as well as diesel fuel were found. By the production process, the viscosity and density of the oil decreased while the calorific value slightly decreased. Biodiesel and its blends as well as diesel fuel were distilled and their distillation behaviors were clarified. It was found that the fuel properties of the biodiesel blends were fairly similar to that of diesel fuel. The distillation property of biodiesel fuels were also found to be similar to that of diesel fuel and within the acceptable limits while it was found to be proportional to the biodiesel amount in the blend. Importantly, the final boiling point of the biodiesel blends were found to be lower than that of diesel fuel as it will lead to a more complete combustion for biodiesel. The torque and power of the biodiesel decreased in comparison to that of diesel mainly due to the lower calorific value of biodiesel. The decrease in the torque and power was proportional to the amount of the biodiesel used in the blend. Thus the lowest toque and power values were obtained for B50 fuel then for B20 and B5 fuels, respectively. However, the decrease in the torque and power of the engine was not proportional to the decrement in the heating values of the biodiesel fuels. Thus the Bsfc values for the usage of biodiesel remained lower when compared with the decrease in heating value. All these arguments showed that due to the improved combustion with the use of biodiesel, it made the performance of the engine remain higher than expected.
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The positive effects of biodiesel were found in the reducing of PM, smoke and CO emissions. The decrease in these emissions was proportional to the biodiesel contained in the blends. The lowest PM, smoke and CO emissions were found for B50 fuel. The NOx and HC emissions were higher for biodiesel blend fuels than that of diesel fuel. References [1] D. Agarwal, L. Kumar, A.K. Agarwal, Performance evaluation of a vegetable oil fuelled compression ignition engine, Renewable Energy 33 (2008) 147–1156. [2] H. Aydin, H. Bayindir, Performance and emission analysis of cottonseed oil methyl ester in a diesel engine, Renewable Energy 35 (2010) 588–592. [3] C. Ilkılıç, H.S. Yücesu, The effect of cottonseed oil methyl ester diesel fuel blends on the performance of a diesel engine, Journal of Fırat University Natural and Engineering Sciences 14 (1) (2002) 199–205. [4] H.S. Yücesu, C. İlkiliç, Effect of cotton seed oil methyl ester on the performance and exhaust emission of a diesel engine, Energy Sources Part A 28 (2006) 389–398. [5] M. Lapuerta, O. Armas, J.R. Fernández, Effect of biodiesel fuels on diesel engine emissions, Progress in Energy and Combustion Science 34 (2008) 198–223. [6] D. Altiparmak, A. Deskin, A. Koca, M. Gürü, Alternative fuel properties of tall oil fatty acid methyl ester–diesel fuel blends, Bioresource Technology 98 (2007) 241–246. [7] N. Usta, An experimental study on performance and exhaust emissions of a diesel engine fuelled with tobacco seed oil methyl ester, Energy Conversion and Management 46 (2005) 2373–2386.
[8] A.K. Agarwal, Vegetable oils versus diesel fuel: development and use of biodiesel in a compression ignition engine, TERI Inf Digest on Energy 8 (1998) 191–204. [9] Y. Akasaka, T. Ssuzaki, Y. Saurai, Exhaust emissions of a DI diesel engine fuelled with blends of biodiesel and low sulfur diesel fuel, SAE paper 972998; 1997. [10] W. Marshall, L.G. Schumacher, S. Howell, Engine exhaust emissions evaluation of a Cummins L10E when fuelled with biodiesel blend, SAE paper 952363; 1995. [11] K.W. Scholl, C.S. Spencer, Combustion of soybean oil methyl ester in a direct injection diesel engine, SAE paper 930934; 1993. [12] S. Şensöz, D. Angın, Pyrolysis of safflower (Charthamus tinctorius L.) seed press cake in a fixed-bed reactor: Part 2. Structural characterization of pyrolysis bio-oils, Bioresource Technology 99 (2008) 5498–5504. [13] J.B. Heywood, Internal combustion engine fundamentals, McGraw-Hill, New York, 1989. [14] A. Monyem, J.H. Van Gerpen, The effect of biodiesel oxidation on engine performance and emissions, Biomass Bioenergy 20 (2001) 317–325. [15] F. Staat, P. Gateau, The effects of rapeseed oil methyl ester on diesel engine performance, exhaust emissions and long term behaviour—a summary of three years of experimentation, SAE paper, 1995, p. 950053. [16] K. Schmidt, J.H. Van Gerpen, The effect of biodiesel fuel composition on diesel combustion and emissions, SAE paper, 1996, p. 961086. [17] A.C. Pinto, L.L.N. Guarieiro, J.C. Rezende, N.M. Ribeiro, E.A. Torres, E.A. Lopes, et al., Biodiesel: an overview, Journal of the Brazilian Chemical Society 16 (2005) 1313–1330. [18] H. Masjuki, A.M. Zaki, S.M. Sapuan, Methyl ester of palm oil as an alternative diesel fuel, Fuels for Automotive and Industrial Diesel Engines 104 (1993).
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Fuel Processing Technology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / f u p r o c
Biodiesel from safflower oil and its application in a diesel engine Cumali Ilkılıç a, Selman Aydın b, Rasim Behcet b,⁎, Hüseyin Aydin b a b
Department of Automotive, Faculty of Technical Education, Fırat University, Elazığ 23119, Turkey Department of Automotive, Faculty of Technical Education, Batman University, Batman 72060, Turkey
a r t i c l e
i n f o
Article history: Received 3 September 2010 Received in revised form 23 September 2010 Accepted 25 September 2010 Available online 20 October 2010 Keywords: Diesel engine Biodiesel Alternative fuel Safflower oil
a b s t r a c t Safflower seed oil was chemically treated by the transesterification reaction in methyl alcohol environment with sodium hydroxide (NaOH) to produce biodiesel. The produced biodiesel was blended with diesel fuel by 5% (B5), 20% (B20) and 50% (B50) volumetrically. Some of important physical and chemical fuel properties of blend fuels, pure biodiesel and diesel fuel were determined. Performance and emission tests were carried out on a single cylinder diesel engine to compare biodiesel blends with petroleum diesel fuel. Average performance reductions were found as 2.2%, 6.3% and 11.2% for B5, B20 and B50 fuels, respectively, in comparison to diesel fuel. These reductions are low and can be compensated by a slight increase in brake specific fuel consumption (Bsfc). For blends, Bsfcs were increased by 2.8%, 3.9% and 7.8% as average for B5, B20 and B50, respectively. Considerable reductions were recorded in PM and smoke emissions with the use of biodiesel. CO emissions also decreased for biodiesel blends while NOx and HC emissions increased. But the increases in HC emissions can be neglected as they have very low amounts for all test fuels. It can be concluded that the use of safflower oil biodiesel has beneficial effects both in terms of emission reductions and alternative petroleum diesel fuel. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Two main concepts that have ever been taken into account in the investigation and development of compression ignition (CI) engine fuels are performance and emissions. Since it was realized that the petrol is not an infinitive source, sustainability, renewability and availability in any kind of fuel have gained a huge attention at the present. At present vegetable oils can be considered as candidates in this subject. However, vegetable oils can not be directly used in CI engines in pure or raw form due to their low volatility and diffusibility but higher viscosity and density. A study was carried out to investigate the performance and emission characteristics of some vegetable oils including linseed oil, mahua oil, rice bran oil and biodiesel obtained from linseed oil, in a stationary diesel engine and to compare them with diesel fuel [1]. The linseed oil, mahua oil, rice bran oil and linseed oil biodiesel were blended with diesel fuel in different proportions. Engine tests were performed by using all these blends of linseed, mahua, rice bran, and biodiesel. It was found that all of the vegetable oils posed operational and durability problems when subjected to long-term usage in CI engine. These problems were attributed to high viscosity, low volatility and polyunsaturated characteristics of vegetable oils.
⁎ Corresponding author. Tel.: + 90 488 217 3664; fax: + 90 4882157201. E-mail addresses: cilkilic@firat.edu.tr (C. Ilkılıç), [email protected] (S. Aydın), [email protected] (R. Behcet), [email protected] (H. Aydin). 0378-3820/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.fuproc.2010.09.028
However, these problems were not observed for biodiesel blends. Hence, the process of transesterification was found to be an effective method of reducing vegetable oil viscosity and eliminating operational and durability problems. In an experimental study, the performance and emissions of cottonseed oil methyl ester in a diesel engine were investigated [2]. It was concluded that with the increase of biodiesel percentage in the blend, the obtained power and torque decreased with a small increase in the brake specific fuel consumption. However, the exhaust emissions fairly reduced. In another work, the effects of cottonseed oil methyl esters on engine performance in a single cylinder diesel engine have been studied [3]. The experiments showed that there was little or no significant difference between the torque and power output of cotton seed oil methyl ester and diesel fuel usage especially at medium and higher speeds of the engine. Yücesu and Ilkiliç [4] reported reductions of 3–8%, in torque and power when they used pure cottonseed biodiesel, while they declared 5% reduction in heating value for biodiesel. They did not use the loss of heating value to justify the power loss, but difficulties in the fuel atomization, instead. A review study was made by Lapuerta et al. [5] and they reported that there were also some publications reporting surprising increases in rated power or torque when using biodiesel. Altiparmak et al. [6] measured a 6.1% increase in maximum torque when they used a blend with 70% tall-oil biodiesel, with respect to what was measured with diesel fuel. Similarly, Usta [7] observed an
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increase in torque and power when using biodiesel from tobacco seed oil (with a lower heating value of 39.8 MJ/kg) in different blends with diesel fuel in an indirect injection diesel engine at 1500 and 3000 rpm. The highest values of torque and power were obtained with a 17.5% blend, despite the reduced heating value of biodiesel. It was also reported in the review [5] that there were a consensus on NOx increase with the use of biodiesel, while sharp reductions in PM and CO emissions were generalized. When blends of biodiesel and diesel fuel were used in diesel engines, a significant reduction in hydrocarbons (HC) and particulate matter (PM) were observed but NOx emissions were found to have increased. In general, engine performance and power remained almost unchanged [8–11]. The various characteristics of bio-oils acquired under different pyrolysis conditions from safflower oil were identified [12]. Some chemical and physical fuel characteristics of safflower obtained biofuel were determined. It was found that the bio-oils obtained from safflower were an environmentally friendly feedstock candidate for biofuels and chemicals. In the present study, safflower seed oil was chemically processed by the transesterification reaction under methanol and NaOH environment to obtain biodiesel. The obtained biodiesel was then used in a single cylinder and four strokes diesel engine. The performance and emission tests were experimentally performed to investigate the biodiesel behavior as an alternative diesel fuel.
2. Material and method
357
Table 1 Technical specifications of the test engine. Type Injection system Cylinder number Stroke volume Compression ratio Maximum power Maximum engine speed Cooling system Injection pressure Mean effective pressure (Mep) Medium piston speed
Rainbow-186 diesel 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)
Engine tests were conducted on a BT-140 model hydraulic dynamometer. Technical specifications of the dynamometer and control unit are given in Tables 2 and 3. PM and smoke were measured with MDO 2-LON type gas analyzer and specification of this device is given in Table 4. The CAPELEC CAP 3200 brand exhaust gas analyzer was used to measure emissions of the test fuels. The technical specifications of the device have been presented in the Table 5. An infrared temperature measurement device was used to specify exhaust gas temperature. The technical specifications of the temperature measurement device are presented in the Table 6. The fuel consumption was measured with burettes with 50 and 100 ml volumes and a stopwatch. The Bsfc was calculated with following equation. :
Experiments were carried out in Engine Test Laboratory of Automotive Department of Technical Education Faculty at University of Batman. The schematic diagram of the experimental setup is shown in Fig. 1. Tests were conducted on a single cylinder, four strokes, air cooled diesel engine. Technical specifications of the test engine were given at Table 1.
be =
V d ρd 3600 Pe
ð1Þ :
Where “be” is the brake specific fuel consumption, “V ” is the flow rate of the fuel as cm3/sn, “ρ” is the density of the fuel as g/cm3 and “Pe” is the brake power as g/kWh.
Fig. 1. A schematic diagram of the engine setup.
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Table 2 Technical specifications of dynamometer.
Table 7 The fuel properties of pure biodiesel (B100) and raw safflower.
Brake motor Maximum brake power Maximum speed Maximum torque Capacity of load cell Water consumption for maximum power Brake water pressure Brake control type Electricity requirement
BT-140 50 HP 7500 rpm 250 Nm 1000 N V max. 0.75 m³/h 1–2 kg/cm² Slippery propeller 220/380 V. 50 Hz.
Parameters
ASTM test no
Safflower oil
B100
Carbon, % Kinematical viscosity (mm2/s) Heat value (MJ/kg) Density (15 C) (g/ml) Flash point (°C) Cloud point (°C) Cetane index
– D445 D2015 D1298 D93 – D613
67 28 39 0.95 225 -2 -
59.5 5.8 38.122 0.8885 148 -5 56
2.1. Biodiesel production from safflower oil The transesterification process of safflower oil to produce biodiesel is presented by the steps below:
Table 3 Technical specifications of the dynamometer control unit. Model Accuracy Precision Response time Weight measurement Speed measurement Screen type
PC101BMS 0.2% ±1 digit 600 μs Linear (load-cell) Sensor 3 × 6 unit, 7-region LED 2 × 16 character LCD 16 W 0–50 °C 220 ± 5% VAC Printer
Power Operation temperature Operation voltage Output
Table 4 Technical specifications of the PM and smoke detector (MDO 2 – LON). Parameter
Measuring range
Precision
Smoke factor (K, factor) PM, particular matters
0…9.99 1/m 0–70%
0.01 0.5
Table 5 Technical properties of the gas analyzing device. Parameter
Measuring range
Precision
HC CO2 CO O2 NOx
0–20,000 ppm 0–20% 0–15% 0–21.7% 0–5000 ppm
1 ppm 0.1% 0.001% 0.01% 1 ppm
Table 6 The technical specifications of the temperature measurement device. Type Temperature measurement range Laser type Diffusion rate Precision Response time
Raytek Raynger ST4 (−32 ile + 545 °C) (−25 ile + 950 °F) Single point 95% ± 1% 500 μsn
- The oil was heated to 55 °C in a 500 ml vessel. It was kept at this stable temperature. To obtain a homogenous mixture of reactants, a magnetic stirrer was used. The mixture of oil and alcoholcatalyzer was stirred at 1000 rev/min. in the vessel. - The heated safflower oil was filled into a cap. An amount of methyl alcohol equal to 20% of prepared oil was mixed with 0.4% NaOH, volumetrically. The mixture was heated and then stirred between 30 and 40 °C until the NaOH was completely solved and liquefied in the alcohol. Then the mixture of alcohol and NaOH was added to the cap containing safflower oil. - The mixture of oil-alcohol-catalyzer was heated at permanent temperature of 55–65 °C and it was stirred simultaneously at about 1000 rev/min. in the reaction cap for 2 h. - After 2 h of reaction time, the products were filled into a washing and separation funnel. The reaction products were separated into two layers, the top one was biodiesel and the bottom one was glycerol. The biodiesel was separated from glycerol. Then sulphuric acid (H2SO4) was added the biodiesel for depolarization. - The biodiesel was then washed with equal amount of water to separate the probably remained alcohol or catalyst from biodiesel. It was then kept for 4 h in the cap to separate the water. Finally, the biodiesel was heated above 100 °C to remove the remaining water from biodiesel fuel. - The obtained fuel, biodiesel, was added to petroleum diesel fuel volumetrically by 5%, 20% and 50%. The fuel mixtures that obtained from the addition of 5%, 20% and 50% of biodiesel were named here as B5, B20 and B50, respectively. The fuel properties of pure biodiesel and raw safflower oil are presented in the Table 7. Also the properties of B5, B20, B50 and a standard diesel fuel are given in the Table 8. The distillation curves of the fuel blends of safflower oil obtained methyl ester-diesel fuel and diesel fuel are illustrated with the Fig. 2. The distillation curves of test fuels are shown in the Fig. 2. The figure shows the amount of distilled volume versus temperature clarifies that the fuel samples were distilled homogenously, smoothly and gradually with temperature increases. This means the smooth,
Table 8 The properties of B5, B20, B50 and a standard diesel fuel. Parameters
ASTM B5 test no
B20
B50
B100
Diesel fuel
Kinematical viscosity (mm2/s) Heat value (MJ/kg) Density (15 C) (g/ml) Flash point (°C) Cetane index
D445 D2015 D1298 D93 D613
3.3764 41486 0.8482 73 52.82
4.0347 40078 0.8639 82 53.86
5.8068 38122 0.8885 148 56.82
3.6663 43350 0.8435 60 49
3.0738 42345 0.84039 69 46.23
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450
9
400
359
D2
B5
B20
B50
8
Engine power, kW
Temperature °C
350 300 250 200
B5 B10 B20 B50 D2
150 100 50 0%
7
6
5
4
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
3 1000
Distilled volume
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm Fig. 2. The distillation curves of D2, B5, B10, B20 and B50 fuels. Fig. 4. The power variation for the biodiesel blend and diesel fuels with engine speed.
3. Results and discussions 3.1. Engine performance 3.1.1. Engine torque For test fuels, the torque variations with engine speed were illustrated with Fig. 3. The maximum torque values were observed around 1600 rpm of engine, for all test fuels including D2. Similar to the power values, the torque for D2 fuel was higher than those of other fuels. It may be due to the higher calorific value of diesel fuel. Another reason for power and torque decrease for biodiesel blend may be higher viscosity of blend fuels. The average torque values for 35 33
D2
B5
B20
B50
31
Torque, N.m
29 27 25 23 21 19 17 15 1000
1250
1500
1750
2000
2250
2500
2750
3000
D2, B5, B20 and B50 fuels were 28.72 Nm, 28.06 Nm, 27.06 Nm and 25.63 Nm, respectively. The lowest torque value was obtained for B50 fuel for all speeds of engine. 3.1.2. Engine power Fig. 4 shows power variations of the test engine for test fuels. It is clear from the Fig. 4 that the power of D2 fuel was found higher than those obtained for biodiesel blends. For blend fuels, the power decreases were almost linear with biodiesel percentage in the blend. The main reason for power decrease may be lower heating values of blend fuels. However, at lower speeds of engine, the power for D2 was almost the same as B5 fuel. It can be attributed to higher thermal efficiency of the test engine with using biodiesel blends. Because biodiesel fuels have enough time to entirely be burned at lower speeds, the conversion of the fuel into energy was more sufficient. 3.1.3. Brake specific fuel consumption Fig. 5 shows the brake specific fuel consumption (Bsfc) variation with engine speed for D2, B5, B20 and B50 fuels. The highest Bsfc was observed for B50 with all speeds of the engine. On the other hand, the lowest Bsfcs were obtained for diesel fuel. The values of Bsfc's those obtained for B5 and B20 fuels were close to each other. Besides, the values for B5 were fairly lower than that of B50 fuel. Average Bsfcs for D2, B5, B20 and B50 fuels were observed about 315 g/kWh, 333 g/kWh, 357 g/kWh and 375 g/kWh, respectively. The main reason for the
Brake specific fuel consumption, g/kWh
gradual and homogenous evaporation of the fuel in the engine cylinder and crucially important in terms of combustion and performance. It also means that the fuel particles in the cylinder were homogenously, gradually and completely combusted. The Fig. 2 also shows that the distillation properties of the blend fuels were similar to that of diesel fuel. However, the primary distillation temperatures of biodiesel fuels were higher than that of diesel fuel since the biodiesel has higher boiling point than diesel fuel. Contrary to the primary distillation temperature, the final distillation temperature was lowest for B50, among all fuels, which contain higher biodiesel amount than the other fuels. It means that the final boiling point of biodiesel was lower than that of diesel fuel which may have a positive effect on the combustion of biodiesel. This affirmative property, as it will be supported by the results of the emission test in our study, led to a reduction in the HC, PM and smoke emissions in the biodiesel usage.
800 D2 B20
B5 B50
700 600 500 400 300 200 1000
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm
Engine speed, rpm Fig. 3. The torque variation for the biodiesel blend and diesel fuels with engine speed.
Fig. 5. The brake specific fuel consumption variation for the biodiesel blend and diesel fuels with engine speed.
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300
0,06 D2
B5
B20
B50
B20 B5
D2 B50
0,05
250
0,04
K, 1/m
Exhaust gas temperature (C)
350
200 150
0,03 0,02
100 0,01 50 1000
1250
1500
1750
2000
2250
2500
0 1000
Engine speed, rpm Fig. 6. The variation of the exhaust gas temperature for biodiesel blend and diesel fuels with engine speed.
increase in Bsfc for blend fuels is considered to be the lower calorific value biodiesel included in the blend. On the other hand, the loss of heating value of biodiesel can be compensated with higher fuel consumption. However the maximum increase was lower than the loss in heating value and this result implies a certain improvement of thermal efficiency with biodiesel. 3.1.4. Exhaust gas temperature The exhaust temperatures of the engine when using D2, B5, B20 and B50 fuels were presented in the Fig. 6. The exhaust temperature increased almost linearly with the increase in engine speed for all the test fuels. It can be seen clearly in the Fig. 6 that the higher temperature values were obtained for biodiesel blend fuels and the increase was observed the highest for B50 fuel. It can be attributed to the more complete combustion for biodiesel use thanks to the oxygen that was inherently contained in the biodiesel. 3.2. Exhaust emissions 3.2.1. Smoke factor (K Factor) and PM emissions The variation of PM emission and smoke opacity of the test fuels with speed are illustrated with Figs. 7 and 8. The emission device is able to measure total particulate emission generally less than or equal to 10 μm in diameter (PM10). It is clear from figures that both PM and smoke decreased with biodiesel use. Both PM and smoke were decreased in proportion to biodiesel concentration in the blend. Thus the lowest PM and smoke emissions obtained for B50 and then for B20
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm Fig. 8. The variation of the smoke factor for the biodiesel blend and diesel fuels with engine speed.
blends. The results show that biodiesel usage enables to reduce both PM emissions and smoke opacity. The main reason that we have used to explain the reductions of PM emission when using biodiesel can be the oxygen content of the biodiesel molecule which enables more complete combustion and promotes the oxidation of already formed soot. The advantage of fuel-oxygen is thought to be a consequence of its higher accessibility to the flame which leads more complete and diffusive combustion. Another reason that can be given is the different structure of soot particles between biodiesel and diesel fuel which may also favor the oxidation of soot from biodiesel. Diesel particulates consist principally of combustion generated carbonaceous material called soot on which some organic compounds have become absorbed [13]. Soot is a general term that refers to impure carbon restricted to the particles which are the residual pyrolyzed fuel particles resulting from the incomplete combustion of a hydrocarbon. The oxidation velocity of biodiesel soot is up to 6 times higher than that of diesel soot. One more explanation that can be given is that the lower sulphur content of safflower derived biodiesel which prevents sulfate formation which being a significant component of typical diesel PM. The usually lower final boiling point of biodiesel provides lower soot being formed from heavy hydrocarbon fractions unable to vaporize. Among the above mentioned reasons both oxygen content and sulphur content can be seen as significantly effect on both PM emissions and smoke opacity. The lowest PM emissions and smoke opacity values were obtained for B50 fuel with engine operation at any speed. 200
2,5 B20 B5
D2 B5
D2 B50
B20 B50
180
NOx, ppm
PM, %
2
1,5
1
140
120
0,5
0 1000
160
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm Fig. 7. The variation of PM emissions for the biodiesel blend and diesel fuels with engine speed.
100 1000
1250
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm Fig. 9. The variation of NOx emissions for the biodiesel blend and diesel fuels with engine speed.
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50
361
5 B20 B5
D2 B50
D2 B5
4,5
40
B20 B50
4
30
CO, %
HC, ppm
3,5
20
3 2,5 2 1,5
10
1 0,5
0 1000
1250
1500
1750
2000
2250
2500
2750
3000
0 1000
1250
Engine speed, rpm
1500
1750
2000
2250
2500
2750
3000
Engine speed, rpm
Fig. 10. The variation of HC emissions for the biodiesel blend and diesel fuels with engine speed.
Fig. 11. The variation of CO emissions for the biodiesel blend and diesel fuels with engine speed.
3.2.2. Nitrogen oxides (NOx) The test results showed an increase in NOx emission when using biodiesel fuel. The obtained increase in NOx emissions was in proportion to the biodiesel concentration in the blend as can be seen in Fig. 9. The lowest NOx emissions were obtained with using diesel fuel and the highest NOx emissions were obtained with B50 fuel. The main reason for NOx increase is the oxygen content of biodiesel which improves combustion thus increases the temperature and resulting NOx production reaction which occurs after 1800 °K. Another argument is the increased cetane numbers of biodiesel which leads to advanced combustion by shortening ignition delay which promotes NOx formation reaction. Since cetane number of biodiesel blends increases in proportion to the concentration of biodiesel in the blend, B50 blend resulted in the highest NOx emission. One more parameter that effects on NOx is iodine number. Biodiesel has higher number of iodine which results in higher NOx emission.
This might have decreased the HC emissions for diesel fuel above those for biodiesel.
3.2.3. Hydrocarbon (HC) The variations of HC emission with engine speed for diesel fuel and biodesel–diesel blends fuels are presented in the Fig. 10. The total unburned hydrocarbons were measured as “ppm” with the gas analyzer. The HC emission which is one of the organic compounds is formed in the result of incomplete combustion. The exhaust gasses contain many different HC compounds. HC emissions fairly increase in the case of richer fuel–air ratios above the stoichiometric ratio. Besides, in the excessively leaned fuel–air ratio conditions, due to incomplete combustion that resulted from the lack of oxygen, HC emissions rapidly increase again. In many cases, the HC emissions for biodiesel have been reported higher than that of diesel fuel [11,14–18]. It can be attributed to the oxygen content in the biodiesel molecule, which leads to a more complete and cleaner combustion. The higher cetane number of biodiesel shortens the combustion delay and thus reduces HC emissions. Another reason may be higher final distillation point of diesel fuel as can be seen in Fig. 10, although biodiesel is less volatile than diesel fuel. This final fraction of the diesel may not be completely vaporized and burnt, thereby increasing HC emissions. In the present study, as can be seen in Fig. 10, the higher HC emissions have been found for B20 and B50 fuels. These surprising results may be due either to the very low HC emissions or to the lower detection limit of the detectors. It was absolutely concluded by the results of this study that the biodiesel had better combustion. It can be seen from the test result for CO, PM emissions and exhaust gas temperature, as well. It can be presented as one more reason for lower HC emission of diesel fuel usage that higher PM emissions of diesel fuel usage might have adsorbed the remaining unburned fuel molecules.
4. Conclusions
3.2.4. Carbon monoxide (CO) As the general trend the CO emissions fairly reduced when substituting diesel fuel with biodiesel and this can be seen in Fig. 11. The lowest CO emissions were found for B50 fuel in average. The decrease in CO emissions for B20 was similar to that for B50. Several reasons can be given for such decrease. Firstly, it may be due to the additional oxygen content in the fuel, which enhances a complete combustion of the fuel, thus reducing CO emissions. Secondly, it can be attributed to the higher cetane number of biodiesel fuel that puts the fuel-rich mixture zone away and improves combustion thus reducing CO emissions. Finally, the advanced injection time of biodiesel use due to molecular structure of biodiesel may also explain the reduction in CO emissions.
In this study, an alternative biodiesel fuel was obtained from safflower seed oil by the transesterification method. Some of important physical and chemical fuel properties of the oil, pure biodiesel and biodiesel blend fuels as well as diesel fuel were found. By the production process, the viscosity and density of the oil decreased while the calorific value slightly decreased. Biodiesel and its blends as well as diesel fuel were distilled and their distillation behaviors were clarified. It was found that the fuel properties of the biodiesel blends were fairly similar to that of diesel fuel. The distillation property of biodiesel fuels were also found to be similar to that of diesel fuel and within the acceptable limits while it was found to be proportional to the biodiesel amount in the blend. Importantly, the final boiling point of the biodiesel blends were found to be lower than that of diesel fuel as it will lead to a more complete combustion for biodiesel. The torque and power of the biodiesel decreased in comparison to that of diesel mainly due to the lower calorific value of biodiesel. The decrease in the torque and power was proportional to the amount of the biodiesel used in the blend. Thus the lowest toque and power values were obtained for B50 fuel then for B20 and B5 fuels, respectively. However, the decrease in the torque and power of the engine was not proportional to the decrement in the heating values of the biodiesel fuels. Thus the Bsfc values for the usage of biodiesel remained lower when compared with the decrease in heating value. All these arguments showed that due to the improved combustion with the use of biodiesel, it made the performance of the engine remain higher than expected.
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The positive effects of biodiesel were found in the reducing of PM, smoke and CO emissions. The decrease in these emissions was proportional to the biodiesel contained in the blends. The lowest PM, smoke and CO emissions were found for B50 fuel. The NOx and HC emissions were higher for biodiesel blend fuels than that of diesel fuel. References [1] D. Agarwal, L. Kumar, A.K. Agarwal, Performance evaluation of a vegetable oil fuelled compression ignition engine, Renewable Energy 33 (2008) 147–1156. [2] H. Aydin, H. Bayindir, Performance and emission analysis of cottonseed oil methyl ester in a diesel engine, Renewable Energy 35 (2010) 588–592. [3] C. Ilkılıç, H.S. Yücesu, The effect of cottonseed oil methyl ester diesel fuel blends on the performance of a diesel engine, Journal of Fırat University Natural and Engineering Sciences 14 (1) (2002) 199–205. [4] H.S. Yücesu, C. İlkiliç, Effect of cotton seed oil methyl ester on the performance and exhaust emission of a diesel engine, Energy Sources Part A 28 (2006) 389–398. [5] M. Lapuerta, O. Armas, J.R. Fernández, Effect of biodiesel fuels on diesel engine emissions, Progress in Energy and Combustion Science 34 (2008) 198–223. [6] D. Altiparmak, A. Deskin, A. Koca, M. Gürü, Alternative fuel properties of tall oil fatty acid methyl ester–diesel fuel blends, Bioresource Technology 98 (2007) 241–246. [7] N. Usta, An experimental study on performance and exhaust emissions of a diesel engine fuelled with tobacco seed oil methyl ester, Energy Conversion and Management 46 (2005) 2373–2386.
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