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Energy Recovery from Waste Plastics by Using Blends of Biodiesel and Polystyrene in Diesel Engines Najeeb Kuzhiyil and Song-Charng Kong* Department of Mechanical Engineering, 2025 Black Engineering Building, Iowa State UniVersity, Ames, Iowa 50011, USA ReceiVed December 18, 2008. ReVised Manuscript ReceiVed April 6, 2009
This study investigated diesel engine combustion and emissions characteristics using blends of biodiesel and polystyrene. As polystyrene accounts for approximately 22% by weight of all high volume plastics, it is attractive to develop methods to convert these waste plastics into energy. Biodiesel is a biorenewable fuel and a good solvent for certain materials. In this study, biodiesel was used as a recycling agent and polystyrene packing peanuts were dissolved in biodiesel in different concentrations as a means to recover energy from waste plastics. Test results showed that engine power increased initially with the polystyrene concentration and then decreased for concentrations higher than 5%. The initial increase in engine power was mainly due to the injection timing advancement caused by the increased bulk modulus and viscosity of fuel blends. The decline in engine power at high polystyrene concentrations could be caused by the poor spray atomization and deteriorated combustion efficiency due to the high viscosity of polystyrene mixtures. Emissions of NOx, soot, CO, and HC were found to increase with the polystyrene concentration if the injection timing was free to advance due to the increased bulk modulus and fuel viscosity. Parametric study was performed by varying engine operating parameters including the fuel injection timing and exhaust gas recirculation. For the same injection timing, higher polystyrene concentrations still resulted in higher soot, CO, and HC emissions but lower NOx emissions. This study demonstrated that polystyrene-biodiesel blends could be successfully used in diesel engines with minor modifications to the fuel system and appropriate adjustments to engine operating conditions.
1. Introduction Municipal and commercial solid wastes contain a large amount of plastics and most of these plastics are not biodegradable. Hence the disposal of waste plastics has been an important concern for the society. The most common method is to use a landfill. Incineration, on the other hand, burns the plastics, but it can cause air pollution. Therefore, energy recovery from waste plastics is gaining importance because of its potential to eliminate plastics and at the same time generate energy using free feedstock, that is, waste plastics. Millions of tons of waste plastics are generated every year worldwide. The U.S. generated 251 million tons of municipal solid wastes in 2006, of which plastics accounted for 11.7 wt % or 29.5 million tons.1 In addition, the U.S. generates approximately 7.6 billion tons of commercial and industrial wastes each year that also contains a considerable quantity of plastics.2 Polystyrene accounts for 22 wt % of all high volume plastics and it is very important to find a clean and efficient way of disposal.3 Ergut et al.4 showed that polystyrene plastic wastes could be burned in furnaces in both diffusion and premixed * Corresponding author. Phone: 515-294-3244; fax: 515-294-3261; e-mail:
[email protected]. (1) United States Environmental Protection Agency. Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2006; US EPA: 2006. (2) United States Environmental Protection Agency. Guide for Industrial Waste Management; US EPA: 1999; EPA 530-R-99-001. (3) Durlak, S. K.; Biswas, P.; Shi, J.; Bernhard, M. J. EnViron. Sci. Technol. 1998, (32), 2301–2307. (4) Ergut, A.; Levendis, Y. A.; Carlson, J. Fuel 2007, (86), 1789–1799.
flames with acceptable emissions levels. Barona et al.5 also showed that polystyrene pellets could be burned in a bubbling fluidized bed combustor. Using polystyrene as a fuel in diesel engines is an attractive option for energy recovery from waste plastics. This method has many advantages. Internal combustion engines can directly power automobiles, trucks, buses, generators, or farm equipment. Using waste plastics in engines can also replace petroleum fuels and thus benefit the environment. There are applications such as large marine vessels where fuel is scarce and expensive, and at the same time the waste plastics generated onboard are available at a negative cost. The polystyrene packing peanuts cannot be burned in a diesel engine in their original form. However, they can be dissolved in a solvent to produce a usable fuel mixture. Biodiesel is an excellent such solvent that is also a proven alternative fuel for diesel engines. Hence, polystyrene packing peanuts dissolved in biodiesel can be a viable fuel. The dissolution properties of polystyrene in various fuels and other solvents can be found in the literature.6,7 However, research using dissolved polystyrene as an engine fuel has not been found. In a carbon-constrained world, the combination of biodiesel and waste plastics as a fuel is of great importance. Biodiesel is an alternate fuel that has lower net carbon emissions than fossil fuels. Biodiesel contains about 11 wt % of oxygen and has a (5) Barona, J.; Bulewicza, E. M.; Kandeferb, S.; Pilawskab, M.; Z˚ukowskia, W.; Hayhurstc, A. N. Fuel 2006, (85), 2494–2508. (6) Narasimhan, B.; Peppas, N. A. J. Polym. Sci., Polym. Phys. Ed. 1996, (34), 947–961. (7) Narasimhan, B.; Peppas, N. A. Macromolecules 1996, (29), 3283– 3291.
10.1021/ef801110j CCC: $40.75 2009 American Chemical Society Published on Web 04/21/2009
Diesel Engine Using Biodiesel-Polystyrene Table 1. Engine Specifications engine make engine model number of cylinders bore (mm) x stroke (mm) displacement (liter) compression ratio aspiration valves per cylinder engine type combustion system rated power fuel injection pump governor type
John Deere 4045TF270 4 106 × 127 4.5 17.0:1 turbocharged 1 intake and 1 exhaust in-line, 4-cycle direct injection 74 KW @ 1800 rpm Stanadyne DB4 mechanical
higher cetane number than regular diesel fuel. Combustion of biodiesel emits significantly less soot, carbon monoxde (CO), and unburned hydrocarbons (HC), but produces slightly higher nitrogen oxide (NOx) emissions when compared with regular diesel fuel.8-12 Various theories have been proposed to explain the higher NOx emissions using biodiesel including effects of flame temperature,13 soot radiative heat loss,14 and the advancement in injection timing.15 Strategies to reduce biodiesel NOx emissions also include exhaust gas recirculation (EGR) and multiple fuel injections.16,17 The blending of polystyrene plastics with biodiesel is a novel approach toward reducing the burden on the landfills, preventing pollution from incineration, recovering energy from waste, and at the same time improving carbon sequestration. In this work, studies were carried out to investigate the optimal concentration of polystyrene in biodiesel that can be successfully used in a diesel engine. Engine performance and emissions characteristics using various blends were assessed. Methods to optimize engine performance and emissions characteristics were devised and tested.
Energy & Fuels, Vol. 23, 2009 3247 Table 2. Properties of the Biodiesel Used in the Study test parameter
result
ASTM limit
units
test method
kinematic viscosity @ 40 °C relative density @ 60 °F sulfur oxidation stability (110 °C) distillation at 90% recovered cetane number higher heating value copper corrosion @ 50 °C, 3 h
4.06 0.885 1.1 6.48 348 49.7 39.1 1a*
1.9-6.0 n/a 15 3.0 min 360 max 47 min n/a 3 max
mm2/sec n/a ppm hrs °C n/a MJ/kg n/a
D445 D1298 D5453 EN14112 D1160-06 D613 D240-07 D130
* Based on ASTM standards.
Figure 1. Schematic of the fuel system.
2. Experimental Setup Engine System. Experiments were performed in a multicylinder turbocharged diesel engine. The engine specifications are listed in Table 1. The base engine was modified to incorporate an EGR system to explore strategies for NOx control. A separate fuel handling system was implemented in order to use multiple fuels during engine testing as shown in Figure 1. Dedicated fuel tanks for B100 and plastic blends were incorporated. Biodiesel used in this study was soy methyl ester (SME). A fuel dumpster for flushing the fuel system while switching between fuel blends was used. The original diaphragm fuel lift pump was replaced with a gear rotary pump to support the high viscosity plastic blends. A Coriolis fuel mass flow meter was used to measure the fuel flow rate. A weight scale was also employed to cross(8) Graboski, S. M.; Ross, J. D.; McCormick, R. L. SAE Tech. Pap. Ser. 1996, 961166. (9) Sharp, C. A.; Howell, S.; Jobe, J. SAE Tech. Pap. Ser. 2000, 200001-1967. (10) United States Environmental Protection Agency. A ComprehensiVe Analysis of Biodiesel Impacts on Exhaust Emissions; US EPA: 2002; EPA 420-P-02-001. (11) Zhang, Y.; Boehman, A. L. Energy Fuels. 2007, (21), 2003–2012. (12) Fang, T.; Lin, Y. C.; Foong, T. M.; Lee, C. F. SAE Tech. Pap. Ser. 2008, 2008-01-1390. (13) Ban-Weiss, G. A.; Chen, J.-Y.; Buchholz, B. A.; Dibble, R. W. Fuel Proc. Technol. 2007, (88), 659–667. (14) Cheng, A. S.; Upatnieks, A.; Mueller, C. J. Int. Jour. Engine Res. 2006, (7), 297–318. (15) Tat, M. E.; Van Gerpen, J. H.; Soylu, S.; Canakci, M.; Moneyem, A.; Wormley, S. J. American Oil Chem. Soc. 2000, (77), 285–289. (16) Choi, C. Y.; Bower, G. R.; Reitz, R. D. SAE Tech. Pap. Ser. 1997, 970218. (17) Karra, P. K.; Veltman, M. K.; Kong, S.-C. Energy Fuels 2009Accepted for publication.
Figure 2. Schematic of the test procedure.
check the flow rate because the high viscosity plastic blends were relatively difficult to flow through the flow meter under certain conditions. The exhaust gas was analyzed for NOx, CO, HC, and CO2 using an online emissions analyzer by DeJaye Electronics while the inlet CO2 due to EGR was measured using a Horiba Mexa-554J gas analyzer. It is known that combustion of polystyrene can result in different hydrocarbons such as various aromatic compounds (e.g., styrene, toluene, benzene, kumene, and polycyclic aromatic hydrocarbons) and light hydrocarbons in different temperature ranges. The detailed speciation of exhaust hydrocarbons was not performed, and only the total unburned hydrocarbon was reported as is the general practice of engine exhaust emissions measurement. CO2 emission was not reported as it is not regulated. The measurement of CO2 was for determining the EGR level, which was defined as the ratio of intake CO2 concentration to the exhaust CO2 concentration. An AVL-415S smoke meter was used to measure the smoke number to determine soot emissions. The smoke number is a measure of the blackness of the filter sample resulting from the passing of the exhaust gas. The smoke number was converted to soot density (mg/m3) in the exhaust by a built-in correlation considering the volume of the exhaust gas sample. The soot density was further converted to the reported emission data (g/kW · hr) by multiplying the soot density in appropriate unit (g/m3) by exhaust volumetric flow rate (m3/hr) and normalized by the engine brake
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Kuzhiyil and Kong Table 5. Properties of the Biodiesel-Plastic Blends fuel blend B100 PS2 PS5 PS10 PS15 PS20
Figure 3. Engine power and BSFC vs PS concentration.
Figure 4. Fuel injection timing shift with respect to PS concentration. Table 3. Properties of the Packing Peanut Used in the Study property
specification
density polystyrene content pentane color concentrate flash point autoignition temperature
2.93-3.91 kg/m3 92-94% 5.5-5.6% 0.5% 266 °C 465 °C
power (kW). The conversions of emissions data were in accordance with SAE standard J1003 (2002). A Superflow water brake dynamometer was coupled with the engine for torque and speed measurements. As experiments were also carried out at different injection timings, a fuel injection timing meter by Time-Tech was used to determine the injection timing. When the change in the injection timing was desired, the injection
flash points of PS blends flash (°C) ASTM limit 139 114 102 96 96 84
oxidative stability of fuel blends temp (°C) h
130 min 130 min 130 min 130 min 130 min 130 min
25-110 25-110 25-110 25-110 25-110 25-110
6.09 4.69 3.50 2.30 0.42 0.52
timing was changed manually by rotating the injection pump until the desirable timing was detected by the timing meter. The Windyn software by a Superflow dynamometer system was used for system control and data acquisition. Fuel Preparation. Polystyrene (PS) packing peanuts can dissolve in biodiesel at room temperature. To create the fuel blend, the peanuts were added to biodiesel in a stainless steel tank with mild agitation. Polystyrene concentrations of 2, 5, 10, 15, and 20 wt % were tested in this study and the fuel blends will be denoted as PS2, PS5, PS10, PS15 and PS20, respectively. Typical properties of the biodiesel and polystyrene used in this study are given in Tables 2 and 3, and those of the fuel blends are given in Tables 4 and 5. Note that some of the fuel blend properties are not available due to the difficulties in testing these highly viscous polymer mixtures. Cetane number is an important property of diesel fuel. The cetane numbers of B100 and PS2 were very similar due probably to the small amount of PS in the PS2 blend. Despite that the cetane number for the higher PS blends were not available, it was speculated that the presence of PS might lower the cetane number due to the complex polymeric structure of the fuel and the formation of PAH due to polystyrene combustion. On the other hand, the cloud point and cold filter plugging point were not investigated since the application of this study was on stationary power generation and the fuel was likely to be stored indoors. Experimental Conditions. The purpose of the present study was to understand the steady-state performance of the engine using various biodiesel-polystyrene blends. Engine tests were performed at the rated speed of 1800 rev/min at full load conditions. During the test, the engine was allowed to reach steady state with respect to power, operating temperatures, and fuel flow rate. On the other hand, increases in certain pollutants were anticipated while burning the plastic blends. EGR was introduced in order to mitigate the NOx emissions using the fuel blends. Another engine parameter that can affect emissions is the fuel injection timing. Hence tests were also carried out with different fuel injection timings. A schematic of the test procedure is shown in Figure 2. The chosen fuel injection timing was set first using the timing meter. The engine was run on biodiesel (B100) to reach steady-state conditions, especially with respect to oil, coolant, and exhaust temperatures. Then the fuel was switched to the desirable plastic blend and the engine was run until the new steady state was attained. The required EGR was obtained by operating the EGR valve. The EGR rate was defined as the ratio of the inlet to exhaust CO2 concentrations. Once the engine reached the steady state, performance data were recorded. The baseline engine data using No. 2 diesel fuel (DN2) and B100 were also obtained for comparison with those using PS blends. These baseline tests were carried out with the factory-set fuel injection timing. It was particularly important to rinse the fuel system using B100 at the end of each test to prevent any deposition
Table 4. Properties of the Biodiesel-Plastic Blends test parameter
ASTM limit
units
test method
DN2
B100
PS2
PS5
PS10
kinematic viscosity @ 40 °C relative density @ 60 °F distillation at 90% recovered cetane number higher heating value copper corrosion @ 50 °C, 3 h
1.9-6.0 n/a 360 max 47 min n/a 3 max
mm2/sec n/a °C n/a MJ/kg n/a
D445 D1298 D1160-06 D613 D240-07 D130
2.50 0.839 314 46.0 44.8 1a
4.06 0.885 348 49.7 39.10 1a
6.38 0.8893 342 51.4 39.64 1a
12.9 0.894 343 n/a 38.72 1a
29 0.902 342 n/a 40.02 1a
Diesel Engine Using Biodiesel-Polystyrene
Figure 5. NOx, soot, CO, and HC emissions vs PS concentration.
of the fuel mixture that could occur during the engine cooling down. A 30 min rinse cycle was used.
3. Results and Discussion Engine combustion and emissions data using various PS blends were presented. Note that due to the difficulties in using these viscous biodiesel-polystyrene blends, some of the tests using high PS concentrations were not possible to carry out. Engine Performance. When the engine was run with the factory-set fuel injection timing, it was found that engine power varied with the PS concentration as shown in Figure 3. Engine power increased with PS concentration for 2 and 5%, but decreased for 10 and 15%. The reason for the increase was the advancement in the fuel injection timing caused by the addition of polystyrene. On the other hand, power decreased with 10 and 15%, possibly due to the poor spray atomization and deteriorated combustion efficiency using high -viscosity fuel blends. Additionally, high PS blends also resulted in very advanced injection timings (Figure 4) that produced early ignition and could cause the piston to work against the expanding gas and thus reduce power output. Figure 3 also shows the variation of brake specific fuel consumption (BSFC) with respect to PS blends. Basically, BSFC followed the inverse of the power curve except in the case of PS15. As the power increased, the specific fuel consumption
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Figure 6. Comparisons of emissions and engine performance using No. 2 diesel (DN2), B100, and PS5 with the factory-set injection timings.
decreased and vice versa when power decreased. In the case of PS15, the fuel flow was very much strained and the fuel pump was not able to inject normal amount of fuel, thus resulting in lower specific fuel consumption. It was documented that biodiesel could cause the advancement in fuel injection due to their higher bulk modulus than diesel fuel when a mechanical injection pump was used.15,18 During the present study, it was observed that the fuel injection timing was further advanced with the addition of polystyrene to biodiesel, as shown in Figure 4. It can be seen that the injection timing was advanced considerably with the increase in the PS concentration. A slight advancement in injection timing using PS2 and PS5 resulted in an increase in engine power. However, a fuel blend higher than PS10 would advance the timing significantly which could have adverse effects on engine power due to the high in-cylinder pressure during the piston compression. A previous study indicated that the injection timing was advanced by a few crank angle degrees when biodiesel was used due to the higher bulk modulus that was proportional to the fuel density.18 Despite that the bulk modulus of the PS blend (18) SAE. Diesel Engine Emission Measurement Procedure, Recommended Practice. In SAE Handbook, SAE J1003; Society of Automotive Engineers: 2002. (19) Boehman, A. L.; Morris, D.; Szybist, J. Energy Fuels 2004, 18 (6), 1877–1882.
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Figure 7. Comparisons of NOx, CO, soot, and engine brake power using different PS blends with the factory-set injection timings.
was not measured in this study, the increase in the fuel density (Table 4) for the PS blends implied an increase in the bulk modulus which in turn could cause the injection timing to advance. Another study also noted that the fuel viscosity also influenced the injection timing.15 The fuel leakage past the plunger decreased as the viscosity increased causing the injection timing to advance. It can be seen in Table 4 that the PS blend had a significantly higher viscosity than biodiesel and thus the injection timing could be advanced significantly (Figure 4). Emission Characteristics. It was anticipated that the high viscosity of the PS blends would affect the spray atomization which in turn would influence combustion. Additionally, the high molecular weight polymers in the fuel mixture could also alter engine emissions characteristics. Figure 5 shows the exhaust emissions using various PS blends. CO and HC emissions increased slightly with a slight increase in the PS concentration and then increased significantly as the PS concentration increased to 10 and 15%. Note that CO and HC are products of incomplete combustion, and the advancement in the injection timing will normally result in more premixed burn with higher combustion temperature for reduced CO and HC emissions. However, as the PS concentration increased to 10%, high viscosity of the PS fuel blend could result in poor spray atomization, and the presence of heavy polymer molecules could also further deteriorate combustion. Therefore, CO and HC emissions increased significantly for PS10 and PS15. NOx emission increased with the PS concentration up to 10% and then remained nearly the same for PS15 as shown in Figure 5. It is known that NOx emissions increase as the injection timing is advanced for the same fuel. The advancement in the fuel injection timing using PS blends and the resultant increase in the premixed burn portion could cause the increase in NOx
emissions. However, from the lower-than-expected BSFC and higher CO, HC, and soot emissions for PS15, it can be inferred that the plateau effect could be caused by two reasons. First, PS15 was highly viscous and the fuel flow rate was reduced so that combustion was not as vigorous. Second, there could be significant incomplete combustion that resulted from poor spray atomization as seen from the increased CO and HC emissions. As a result, the flame temperature was lower than expected with the highly advanced fuel injection timing. Therefore, NOx emissions using PS15 did not increase significantly. The trend of soot emissions was similar to that of CO and HC emissions. Soot emissions increased at high PS concentrations. In the case of PS10 and PS15, poor atomization and incomplete combustion could occur due to the presence of a large number of polymer molecules in the fuel mixture, causing soot emissions to increase. Comparison with Diesel and Biodiesel. Engine performance using No. 2 diesel (DN2) and B100 was compared to that using PS5, which appeared to be a preferable fuel blend. Figure 6 shows engine power and emissions for the three fuels for various EGR conditions. It can be seen that B100 produced higher NOx and lower soot and CO emissions. Engine power decreased slightly using B100 due to the lower energy content. The increase in NOx emissions was approximately 14% and the decrease in soot emissions was approximately 59% without using EGR. Figure 6 also shows that PS5 increased NOx emissions compared to B100 when the factory-set injection timing was used. The results in Figure 6 indicated that a 10% EGR could be used to reduce NOx emissions using PS5 to reach the same level of NOx emissions using DN2 with the expense of increased soot and CO emissions. Another alternative to reduce NOx
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Figure 8. Comparisons of NOx, CO, soot, and engine brake power using different PS blends with different actual injection timings.
emissions using PS blends is to use appropriate additives in order to prevent a significant increase in other emissions. Effects of EGR. Figure 6 also shows that for DN2, B100, and PS5, EGR will decrease NOx emissions and engine power but increase soot and CO emissions due to lower combustion temperatures. The combined effects of EGR and the PS concentration are shown in Figure 7. The trends of emissions with respect to the PS concentration and EGR were within expectation. NOx and CO emissions using PS10 were significantly higher than those using other fuels for the same operating conditions. Soot emissions were comparable using B100, PS2, and PS5, and soot emissions using PS10 were noticeably higher for 10 and 15% EGR conditions. It appeared that soot emissions were within the reasonable range for all PS blends if the EGR rate was lower than 10%. This is because the base fuel (i.e., B100) produced relatively low soot emissions, and the advancement in the injection timing using high PS blends can further benefit soot reduction. It is known that soot emissions decrease with early injection timings. On the other hand, engine power increased with the PS concentration for PS2 and PS5, but it decreased drastically in the case of PS10 resulting from fuel starvation due to high viscosity. The trend of BSFC was opposite to that of emissions, as shown later in Figure A-2A-2 in the Appendix. Effect of Injection Timing. The fuel injection timing was advanced when PS blends were used. As discussed earlier, the advancement increased with the PS concentration. To determine the effects of the timing advancement, tests were carried out with different injection timings for different PS blends. The trend of engine performance and emissions were the same for different
PS blends, and only results using PS5 are shown in Figure 8. Notice that the axis for EGR was reversed in order to show the entire data surface. As fuel injection was advanced, NOx emissions increased and soot emissions decreased. Results were consistent with the common understanding that early injection would produce higher cylinder pressures and overall combustion temperatures, resulting in higher NOx but lower soot emissions. On the other hand, CO emissions increased with advanced injection timing. It is known that CO emissions are the lowest at certain injection timing (before top-dead-center) when the combustion efficiency is the highest. All of the injection timings tested in this study appeared to be more advanced than the timing that was optimal for low CO emissions. Engine power increased with advanced fuel injection initially and then decreased with further advancement as also shown in Figure 8. The initial increase was attributed to the higher cylinder pressure during the piston expansion that produced more work output while the decrease was due to the higher cylinder pressure during compression that resulted in more negative work. On the other hand, the BSFC followed the opposite trend of engine power, as shown later in Figure A-3 in the Appendix. It can be seen that most of the emissions and performance characteristics were largely affected by the shift in the injection timing. Meanwhile, soot emissions were also significantly influenced by the PS content as the combustion of the very large polymer molecules could produce complex PAHs that resulted in higher soot emissions. Combustion of the high PS blends might require a longer time to complete, which could also have implications on exhaust emissions. Therefore, tests were carried
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and reached a maximum at 5% polystyrene concentration, then the power decreased for higher concentrations. NOx emissions increased as a result of injection timing advancement. However, NOx emissions were reduced slightly for increased polystyrene concentrations if the same injection timing was used. An appropriate combination of power and emissions can be obtained by setting the initial fuel injection timing as retarded as possible using B100 so that the advancement effect caused by polystyrene can be mitigated. Increased polystyrene concentrations resulted in higher CO and soot emissions, indicating more incomplete combustion due possibly to poor fuel spray atomization. Exhaust gas recirculation was used to mitigate the high NOx emissions using biodiesel-polystyrene mixture as compared to those using regular diesel fuel, with the expense of increasing CO and soot emissions. It was found that an EGR rate of 10% can give appropriate power and emissions of NOx, CO, and soot. Acknowledgment. The authors acknowledge the financial support of Renewable Energy Group.
Appendix
Figure 9. Comparisons of NO, CO, soot, and engine brake power using different PS blends at the same injection timing.
out to investigate the effects of the PS concentration alone under the same injection conditions. Figure 9 shows the results of emissions using different PS blends at 13 BTDC injection. As the PS concentration increased, NOx decreased and soot and CO increased. Such characteristics could result from more incomplete combustion and lower flame temperatures due to the increase in the heavier polymer molecules in the fuel that required longer time for combustion to complete. Interestingly, the engine power showed a slight increase for PS5 and then a decrease as the PS concentration further increased. This can be due to the increase in the density of the fuel blend when the PS concentration increased. The power drop for PS10 can be attributed to the high viscosity and the associated flow problems.
Figure A-1. Comparisons of BSFC using DN2, B100, and PS5 with the factory-set injection timings.
4. Summary and Conclusions Engine testing was carried out with various polystyrenebiodiesel blends. It was found that the feasible limit of polystyrene concentration was 10% by weight, beyond which the fuel mixture became too viscous for proper fuel pump operation. Results indicated that the optimal polystyrene concentration that could be used without difficulties in fuel flow and injection was 5% by weight. Higher concentrations caused poor fuel flow through the injection system and higher emissions. Polystyrene in the fuel mixture caused the fuel injection timing to advance due to their higher bulk modulus and affected engine power and emissions. Engine power increased slightly
Figure A-2. Comparisons of BSFC using different PS blends with the factory-set injection timings.
Diesel Engine Using Biodiesel-Polystyrene
Figure A-3. Comparisons of BSFC using different PS blends with different injection timings.
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Figure A-4. Comparisons of BSFC using different PS blends at the same injection timing. EF801110J
