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Effect of injection timing on performance and emission characteristics of single cylinder diesel engine running on blends of diesel and waste plastic fuels
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 17 (2019) 209–215
www.materialstoday.com/proceedings
ICAMEES2018
Effect of injection timing on performance and emission characteristics of single cylinder diesel engine running on blends of diesel and waste plastic fuels Shashank pala, V Chintalaa*, Amit Kumar Sharmab, Praveen Ghodkec, Sagar Kumara, Pramesh Kumara a
Centre for Alternate Energy Research, and Department of Mechanical Engineering; School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, Uttarakhand, 248007 b Department of Chemistry; School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, Uttarakhand, 248007 c Department of Electrical Power and Energy; School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, Uttarakhand, 248007
Abstract
Environmental concern, increasing fossil fuel demands and depleting fossil fuel reserves have caused interests in the search for alternate fuels for internal combustion engines. Waste plastics are indispensable materials in the modern world and application in the industrial field is continually increasing. In this context, waste plastic solid is currently receiving renewed interest. the recycling of the waste plastic for renewable energy generation is receiving more attention nowadays. The present study deals with utilization of waste plastic pyrolysed oil in single cylinder diesel engine with varying injection timing. The pyrolysis of mixed waste plastic was carried out at 400oC-550oC in a fixed bed reactor. The physic chemical properties such as calorific value density, viscosity, cloud point, pour point, flash point of the plastic fuel and its blends with diesel (PF10,PF20,PF30) was analysed using standard methods and found under ASTM standards. To see the effect of injection timing on performance and emission, a single cylinder diesel engine was run on plastic fuel blends at the two different angles (10o retard and the 8o advance before the TDC). The results showed that at advanced condition BTE, CO, UHC, CO2 and smoke increased while BSFC and NOx decreased with the increasing load. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials, Energy & Environmental Sustainability, ICAMEES2018 Keywords: Plastic waste; Pyrolysis; Single cylinder diesel engine; Performance and emission characteristics.
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials, Energy & Environmental Sustainability, ICAMEES2018
210
S. Pal et al. / Materials Today: Proceedings 17 (2019) 209–215
1. Introduction: Use of plastics in various sectors such as construction, healthcare, electronic, automotive, packaging is exceedingly increasing due to rapid growth of the world population. Plastics are non-biodegradable polymers mostly containing carbon, hydrogen, and few other elements. Due to its non-biodegradable nature, the plastic waste is also increasing day by day and contributes significant health and pollution problems. In addition, treatment of mixed plastic waste is still problematic as compared to single plastics. Segregation of mixed plastic waste is involved with huge financial investments, because which treatment of mixed plastic at lower costs is gaining much importance [15]. Material variability and material compatibility are other significant problems to be addressed with mixed plastic waste [3, 6]. In order to overcome all these problems, in current study direct conversion of mixed plastic waste into liquid fuel by thermochemical pyrolysis was investigated. Pyrolysis process one of the most useful and most appropriate technique to delicacy the waste plastics and this process not also solve the problems of recycling but also help to get energy in the form of pyrolysis oil and syngas [7, 8]. Pyrolysis process is carried out in absence of the oxygen at higher temperature (300-500oC) and resulted into three products i.e. liquid, gas and solids (Char) [9]. According to literature, the physico-chemical properties of plastic pyrolysed liquid fuels are quite similar to fossil fuel hydrocarbon and can be used in spark plug ignition/compression ignition as alternative to gasoline/diesel fuel [10-12]. Waste plastic oil was used as a fuel candidate for different engine applications including irrigation, marine, and power generation. However, there is limited literature available investigating the effect of fuel injection timing on engine performance and emissions fuelled with waste plastic pyrolysis oil. Therefore, the objective of this paper is to study the influence of injection timing on performance and emissions of single cylinder diesel engine fuelled with diesel and waste plastic pyrolysis oil blends. 2. Experimental methodology 2.1. Conversion of waste plastic to oil and analysis of its properties Mixed plastic waste fuel was produced by a batch-scale production plant of 100 g/batch at University of Petroleum and Energy Studies (UPES). The experiment was run for 400oC-550oC for 1 h in a fixed bed reactor. The fuel properties of this oil were examined according to ASTM standards and shown in table 1. These plastic-oils were tested in a single cylinder diesel engine with varying injection timing at different loads. 2.2. Engine experimental tests The engine tests were conducted on single cylinder four-stroke compression ignition (CI) engine of 3.7 kW connected with water-cooled eddy current dynamometer (Figure 1). Specifications of the CI engine are given in the Table 2. The engine was run with different blends e.g. PF 10 (diesel-90% and plastic fuel- 0%), PF 20 (diesel-80%
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and plastic fuel 20%) PF 30 (diesel-70% and plastic fuel 30%). The engine experiments were conducted at the rated speed of 1500 rpm at standard (27oCA), advanced (35o CA) and retard (-17o CA) fuel injection timings. Engine tailpipe pollutants such as NOx/HC/CO were analyzed using NDIR based Di-gas emission analyzer. Smoke was measured in % opacity by Smoke meter. 3. Results and discussion The test engine behavior in terms of performance (thermal efficiency) and emissions is assessed based on the experimental test results obtained by running the engine at 50% (1.8 kW) and 100% (3.7 kW) loads. 3.1. Effect of injection timing on performance characteristics of CI engine Figure 2 illustrates break thermal efficiency (BTE) of the test engine at retard, advance and ideal fuel injection timings at 1.8 kW and 3.7 kW loads. At a particular load, the efficiency decreased with increasing share of plastic oil in the blend. The efficiency was higher with advanced injection timing than the ideal condition. However, it decreased slightly with restarted injection timing as seen in the figure. Increase in efficiency with advanced timing is mainly due to improvement in combustion performance.
Figure 1: Experimental engine connected with eddy current dynamometer Table 1 Fuel properties of the plastic oils and its blends with diesel
Properties
Diesel
Plastic oil
PF10
PF20
PF30
Density (g/cm3)
0.817
0.792
0.815
0.813
Viscosity (cSt)
2.81
2.21
2.78
2.73
0.8104 2.69
Calorific value (kJ/kg)
43479
41457
43024
42894
42524
Cloud point (oC)
-1.3
14.3
2.1
3.4
7.2
Pour point (oC)
-3.7
9.7
-1.1
1.8
4.8
Flash point (oC)
51.4
30.2
37.3
35.5
33.2
PH
6.8
5.8
5.8
6.1
6.2
212
S. Pal et al. / Materials Today: Proceedings 17 (2019) 209–215
Table 2: Technical specifications of the test engine Particulars Engine Type Number of Cylinders Cubic Capacity Compression ratio Bore x stroke Specific fuel consumption Engine Cooling type Engine Cooling Water Flow Connecting Rod Length
Specification Compression Ignition 1 0.533L 16.7:1 80x110 mm 245g/kwh Water cooled 60 ml/sec 235 mm
Time available for homogeneous air-fuel mixture will increase with advanced timing, which further helped for improvement in combustion. At high load, combustion performance improved due to the higher cylinder temperature. The maximum efficiency obtained about 35.1% with advanced injection timing at 100% load operation. It was clearly observed that the efficiency of the test engine decreased with the use of plastic oil blends at all loads. Kaimal et al. also achieved lower thermal efficiency about 27.3% with plastic oil as compared to 31.2% with diesel fuel in a multi cylinder CI engine.
Figure 2: Effect of injection timing on brake thermal efficiency at different loads
3.2. Effect of injection timing on emissions characteristics of CI engine Figure 3 illustrates effect of injection timing on carbon monoxide (CO) emission at 1.8 kW and 3.7 kW loads on the test engine in ideal fuel injection condition, advance fuel injection and retard fuel injections. The maximum amount of CO was about 0.06% volume at 1.8 kW load with PF30 fuel as seen in the figure. At 3.7 kW load, the emission was higher with retarded injection timing than ideal timing. For example with PF30 fuel at 3.7 kW load, the emission was about 0.09% volume with retarded timing than 0.08% with ideal timing. The main reasons for higher CO emission could be less oxygen level, poor air entrainment during air fuel mixture formation and incomplete combustion. The incomplete oxidation of compound of aromatics and partial oxidation is the appropriate reasons to get the maximum amount of CO emission [13].
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Figure 3: Effect of injection timing on carbon monoxide emissions
Figure 4 illustrates the emission of the unburned hydrocarbon (UHC) emission at 1.8 kW and 3.7 kW loads. At 1.8 kW load, the maximum unburned hydrocarbon was 40ppm for PF30 under the advance fuel injection condition while minimum was 17ppm for diesel under ideal condition. The UHC emission also followed the similar trends as CO emissions. The emissions increased with retard timing and decreased with advanced timing as compared to conventional timing at all loads. It may be concluded that on increasing the load, the amount of UHC increased with advanced fuel injection timing. The main reason of the producing the unburn hydrocarbon is the insufficient temperature during combustion in cylinder chamber. It depends upon the flame quenching, less temperature of the combustion, poor air-fuel mixing, over lean and rich mixture, misfiring. In case of plastic oil blends combustion, bulk flame quenching and misfiring combustion could be the initial source because of the aromatic compounds. In the experiments of Kumar et al., UHC emissions increased from 0.1g/kwh with pure diesel to 0.4 g/kwh with waste plastic oil in a CI engine at 5.4 kW load [14]. The reason behind of producing UHC may be the presence of higher aromatic compounds in the plastic oil and longer ignition delay.
Figure 4: Effect of injection timing unburnt hydrocarbon emissions Figure 5 shows that Nitrogen oxides (NOx) emissions from the test engine under ideal fuel injection condition i.e. 27o CA, advance fuel injection (8oCA bTDC) and retard fuel injection (10oCA bTDC) timings. At 1.8 kW of load, the NOx emission was 807 ppm under advance fuel injection condition for PF10 in comparison to minimum NOx of 243 ppm under retard condition. At the maximum load of 3.7 kW, maximum NOx was found to be 813 ppm under advance condition. On the other hand, minimum amount of NOx about 342 ppm was emitted under retard condition for PF30. Basically the formation of the NOx emission in CI engines depends upon the three parameters (i) temperature of combustion inside the cylinder (ii) content of oxygen available in the engine Cylinder (iii) Reaction time [15-17]. For constant speed engine, higher combustion temperature is the main reason for formation of NOx emission [18, 19].
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Figure 6 explains the effect of injection timing on smoke emissions at 1.8 kW and 3.7 kW loads. In case of 1.8 kW load, maximum smoke opacity about 54.1% was observed for diesel under ideal condition while minimum smoke opacity was 24.3% for PF30 under ideal condition. Similarly, at 3.7 kW load, the maximum smoke opacity was found to be 49.1% under ideal condition for pure diesel and minimum smoke opacity was 24% for PF30 under advanced condition. On increasing the load, the smoke quantity increased significantly. The formation of the smoke pollutants occur in the combustion chamber where the sufficient air/oxygen is unavailable. The ratio of air-fuel in the chamber promote pollutant formation largely. On using the plastic oil, smoke pollutant is much higher with increasing engine load as compare to the pure diesel. Improper mixing of vaporised fuel particles with air led the heterogeneous combustion with the use of plastic oil in CI engines [20].
Figure 5: Effect of injection timing on oxides of nitrogen emissions
Figure 6: Effect of injection timing on smoke emissions 4. Conclusions It was concluded that the test engine operation was smooth until certain percentage of plastic fuel blending with diesel i.e., 30% beyond which the operation was not smooth. Retarded fuel injection timing resulted in lower efficiency and higher emissions. However, advancing the fuel injection timing is the viable option to solve the problem of lower thermal efficiency and higher carbon-based emissions. Acknowledgements Authors would like to thank the Department of Science and Technology, New Delhi, India for the financial support (Grant No: ECR/2017/000185) to carry out the experiments.
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References 1. 2. 3. 4. 5. 6.
7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.
Maris, J., et al., Mechanical recycling: Compatibilization of mixed thermoplastic wastes. Polymer Degradation and Stability, 2017. Wang, J., et al., A novel process for separation of hazardous poly(vinyl chloride) from mixed plastic wastes by froth flotation. Waste Management, 2017. 69(Supplement C): p. 59-65. Suresh, S.S., et al., A review on computer waste with its special insight to toxic elements, segregation and recycling techniques. Process Safety and Environmental Protection, 2018. 116: p. 477-493. Andersson, C. and J. Stage, Direct and indirect effects of waste management policies on household waste behaviour: The case of Sweden. Waste Management, 2018. Zhao, P., et al., Separation of mixed waste plastics via magnetic levitation. Waste Manag, 2018. Sudershan, B.G., et al., Experimental Studies on the Use of Pyrolysis Oil for Diesel Engine Applications and Optimization of Engine Parameters of Injection Timing, Injector Opening Pressure and Injector Nozzle Geometry. Arabian Journal for Science and Engineering, 2018. 43(9): p. 4517-4530. Kalargaris, I., G. Tian, and S. Gu, Combustion, performance and emission analysis of a DI diesel engine using plastic pyrolysis oil. Fuel Processing Technology, 2017. 157: p. 108-115. Kapilan, N. and N. Jullya, Studies on Improvement of Performance of Compression Ignition Engine Fuelled with Mixture of Honge Biodiesel and Tire Pyrolysis Oil. Strojnícky casopis – Journal of Mechanical Engineering, 2018. 68(1): p. 15-24. Hopewell, J., R. Dvorak, and E. Kosior, Plastics recycling: challenges and opportunities. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 2009. 364(1526): p. 2115-2126. Wong, S., et al., Current state and future prospects of plastic waste as source of fuel: A review. Renewable and sustainable energy reviews, 2015. 50: p. 1167-1180. Damodharan, D., et al., Combined influence of injection timing and EGR on combustion, performance and emissions of DI diesel engine fueled with neat waste plastic oil. Energy Conversion and Management, 2018. 161: p. 294-305. Pradhan, D., et al., Mahua seed pyrolysis oil blends as an alternative fuel for light-duty diesel engines. Energy, 2017. 118: p. 600-612. Chintala, V., et al., A comparative assessment of single cylinder diesel engine characteristics with plasto-oils derived from municipal mixed plastic waste. Energy Conversion and Management, 2018. 166: p. 579-589. Kumar, S., et al., Performance and emission analysis of blends of waste plastic oil obtained by catalytic pyrolysis of waste HDPE with diesel in a CI engine. Energy conversion and management, 2013. 74: p. 323-331. Heywood, J.B., Internal combustion engine fundamentals; Chapter 10: Combustion in Compression-Ignition Engines. 1988, New York: McGraw-Hill. Chintala, V. and K. Subramanian, Hydrogen energy share improvement along with NOx (oxides of nitrogen) emission reduction in a hydrogen dual-fuel compression ignition engine using water injection. Energy Conversion and Management, 2014. 83: p. 249-259. Chintala, V. and K. Subramanian, CFD analysis on effect of localized in-cylinder temperature on nitric oxide (NO) emission in a compression ignition engine under hydrogen-diesel dual-fuel mode. Energy, 2016. 116: p. 470-488. Turns, S.R., An introduction to combustion. Vol. 499. 1996: McGraw-hill New York. Chintala, V. and K. Subramanian, A comprehensive review on utilization of hydrogen in a compression ignition engine under dual fuel mode. Renewable and Sustainable Energy Reviews, 2017. 70: p. 472-491. Chintala, V. and K. Subramanian, Experimental investigations on effect of different compression ratios on enhancement of maximum hydrogen energy share in a compression ignition engine under dual-fuel mode. Energy, 2015. 87: p. 448-462.
ScienceDirect Materials Today: Proceedings 17 (2019) 209–215
www.materialstoday.com/proceedings
ICAMEES2018
Effect of injection timing on performance and emission characteristics of single cylinder diesel engine running on blends of diesel and waste plastic fuels Shashank pala, V Chintalaa*, Amit Kumar Sharmab, Praveen Ghodkec, Sagar Kumara, Pramesh Kumara a
Centre for Alternate Energy Research, and Department of Mechanical Engineering; School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, Uttarakhand, 248007 b Department of Chemistry; School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, Uttarakhand, 248007 c Department of Electrical Power and Energy; School of Engineering, University of Petroleum and Energy Studies (UPES), Dehradun, Uttarakhand, 248007
Abstract
Environmental concern, increasing fossil fuel demands and depleting fossil fuel reserves have caused interests in the search for alternate fuels for internal combustion engines. Waste plastics are indispensable materials in the modern world and application in the industrial field is continually increasing. In this context, waste plastic solid is currently receiving renewed interest. the recycling of the waste plastic for renewable energy generation is receiving more attention nowadays. The present study deals with utilization of waste plastic pyrolysed oil in single cylinder diesel engine with varying injection timing. The pyrolysis of mixed waste plastic was carried out at 400oC-550oC in a fixed bed reactor. The physic chemical properties such as calorific value density, viscosity, cloud point, pour point, flash point of the plastic fuel and its blends with diesel (PF10,PF20,PF30) was analysed using standard methods and found under ASTM standards. To see the effect of injection timing on performance and emission, a single cylinder diesel engine was run on plastic fuel blends at the two different angles (10o retard and the 8o advance before the TDC). The results showed that at advanced condition BTE, CO, UHC, CO2 and smoke increased while BSFC and NOx decreased with the increasing load. © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials, Energy & Environmental Sustainability, ICAMEES2018 Keywords: Plastic waste; Pyrolysis; Single cylinder diesel engine; Performance and emission characteristics.
2214-7853 © 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International Conference on Advanced Materials, Energy & Environmental Sustainability, ICAMEES2018
210
S. Pal et al. / Materials Today: Proceedings 17 (2019) 209–215
1. Introduction: Use of plastics in various sectors such as construction, healthcare, electronic, automotive, packaging is exceedingly increasing due to rapid growth of the world population. Plastics are non-biodegradable polymers mostly containing carbon, hydrogen, and few other elements. Due to its non-biodegradable nature, the plastic waste is also increasing day by day and contributes significant health and pollution problems. In addition, treatment of mixed plastic waste is still problematic as compared to single plastics. Segregation of mixed plastic waste is involved with huge financial investments, because which treatment of mixed plastic at lower costs is gaining much importance [15]. Material variability and material compatibility are other significant problems to be addressed with mixed plastic waste [3, 6]. In order to overcome all these problems, in current study direct conversion of mixed plastic waste into liquid fuel by thermochemical pyrolysis was investigated. Pyrolysis process one of the most useful and most appropriate technique to delicacy the waste plastics and this process not also solve the problems of recycling but also help to get energy in the form of pyrolysis oil and syngas [7, 8]. Pyrolysis process is carried out in absence of the oxygen at higher temperature (300-500oC) and resulted into three products i.e. liquid, gas and solids (Char) [9]. According to literature, the physico-chemical properties of plastic pyrolysed liquid fuels are quite similar to fossil fuel hydrocarbon and can be used in spark plug ignition/compression ignition as alternative to gasoline/diesel fuel [10-12]. Waste plastic oil was used as a fuel candidate for different engine applications including irrigation, marine, and power generation. However, there is limited literature available investigating the effect of fuel injection timing on engine performance and emissions fuelled with waste plastic pyrolysis oil. Therefore, the objective of this paper is to study the influence of injection timing on performance and emissions of single cylinder diesel engine fuelled with diesel and waste plastic pyrolysis oil blends. 2. Experimental methodology 2.1. Conversion of waste plastic to oil and analysis of its properties Mixed plastic waste fuel was produced by a batch-scale production plant of 100 g/batch at University of Petroleum and Energy Studies (UPES). The experiment was run for 400oC-550oC for 1 h in a fixed bed reactor. The fuel properties of this oil were examined according to ASTM standards and shown in table 1. These plastic-oils were tested in a single cylinder diesel engine with varying injection timing at different loads. 2.2. Engine experimental tests The engine tests were conducted on single cylinder four-stroke compression ignition (CI) engine of 3.7 kW connected with water-cooled eddy current dynamometer (Figure 1). Specifications of the CI engine are given in the Table 2. The engine was run with different blends e.g. PF 10 (diesel-90% and plastic fuel- 0%), PF 20 (diesel-80%
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and plastic fuel 20%) PF 30 (diesel-70% and plastic fuel 30%). The engine experiments were conducted at the rated speed of 1500 rpm at standard (27oCA), advanced (35o CA) and retard (-17o CA) fuel injection timings. Engine tailpipe pollutants such as NOx/HC/CO were analyzed using NDIR based Di-gas emission analyzer. Smoke was measured in % opacity by Smoke meter. 3. Results and discussion The test engine behavior in terms of performance (thermal efficiency) and emissions is assessed based on the experimental test results obtained by running the engine at 50% (1.8 kW) and 100% (3.7 kW) loads. 3.1. Effect of injection timing on performance characteristics of CI engine Figure 2 illustrates break thermal efficiency (BTE) of the test engine at retard, advance and ideal fuel injection timings at 1.8 kW and 3.7 kW loads. At a particular load, the efficiency decreased with increasing share of plastic oil in the blend. The efficiency was higher with advanced injection timing than the ideal condition. However, it decreased slightly with restarted injection timing as seen in the figure. Increase in efficiency with advanced timing is mainly due to improvement in combustion performance.
Figure 1: Experimental engine connected with eddy current dynamometer Table 1 Fuel properties of the plastic oils and its blends with diesel
Properties
Diesel
Plastic oil
PF10
PF20
PF30
Density (g/cm3)
0.817
0.792
0.815
0.813
Viscosity (cSt)
2.81
2.21
2.78
2.73
0.8104 2.69
Calorific value (kJ/kg)
43479
41457
43024
42894
42524
Cloud point (oC)
-1.3
14.3
2.1
3.4
7.2
Pour point (oC)
-3.7
9.7
-1.1
1.8
4.8
Flash point (oC)
51.4
30.2
37.3
35.5
33.2
PH
6.8
5.8
5.8
6.1
6.2
212
S. Pal et al. / Materials Today: Proceedings 17 (2019) 209–215
Table 2: Technical specifications of the test engine Particulars Engine Type Number of Cylinders Cubic Capacity Compression ratio Bore x stroke Specific fuel consumption Engine Cooling type Engine Cooling Water Flow Connecting Rod Length
Specification Compression Ignition 1 0.533L 16.7:1 80x110 mm 245g/kwh Water cooled 60 ml/sec 235 mm
Time available for homogeneous air-fuel mixture will increase with advanced timing, which further helped for improvement in combustion. At high load, combustion performance improved due to the higher cylinder temperature. The maximum efficiency obtained about 35.1% with advanced injection timing at 100% load operation. It was clearly observed that the efficiency of the test engine decreased with the use of plastic oil blends at all loads. Kaimal et al. also achieved lower thermal efficiency about 27.3% with plastic oil as compared to 31.2% with diesel fuel in a multi cylinder CI engine.
Figure 2: Effect of injection timing on brake thermal efficiency at different loads
3.2. Effect of injection timing on emissions characteristics of CI engine Figure 3 illustrates effect of injection timing on carbon monoxide (CO) emission at 1.8 kW and 3.7 kW loads on the test engine in ideal fuel injection condition, advance fuel injection and retard fuel injections. The maximum amount of CO was about 0.06% volume at 1.8 kW load with PF30 fuel as seen in the figure. At 3.7 kW load, the emission was higher with retarded injection timing than ideal timing. For example with PF30 fuel at 3.7 kW load, the emission was about 0.09% volume with retarded timing than 0.08% with ideal timing. The main reasons for higher CO emission could be less oxygen level, poor air entrainment during air fuel mixture formation and incomplete combustion. The incomplete oxidation of compound of aromatics and partial oxidation is the appropriate reasons to get the maximum amount of CO emission [13].
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213
Figure 3: Effect of injection timing on carbon monoxide emissions
Figure 4 illustrates the emission of the unburned hydrocarbon (UHC) emission at 1.8 kW and 3.7 kW loads. At 1.8 kW load, the maximum unburned hydrocarbon was 40ppm for PF30 under the advance fuel injection condition while minimum was 17ppm for diesel under ideal condition. The UHC emission also followed the similar trends as CO emissions. The emissions increased with retard timing and decreased with advanced timing as compared to conventional timing at all loads. It may be concluded that on increasing the load, the amount of UHC increased with advanced fuel injection timing. The main reason of the producing the unburn hydrocarbon is the insufficient temperature during combustion in cylinder chamber. It depends upon the flame quenching, less temperature of the combustion, poor air-fuel mixing, over lean and rich mixture, misfiring. In case of plastic oil blends combustion, bulk flame quenching and misfiring combustion could be the initial source because of the aromatic compounds. In the experiments of Kumar et al., UHC emissions increased from 0.1g/kwh with pure diesel to 0.4 g/kwh with waste plastic oil in a CI engine at 5.4 kW load [14]. The reason behind of producing UHC may be the presence of higher aromatic compounds in the plastic oil and longer ignition delay.
Figure 4: Effect of injection timing unburnt hydrocarbon emissions Figure 5 shows that Nitrogen oxides (NOx) emissions from the test engine under ideal fuel injection condition i.e. 27o CA, advance fuel injection (8oCA bTDC) and retard fuel injection (10oCA bTDC) timings. At 1.8 kW of load, the NOx emission was 807 ppm under advance fuel injection condition for PF10 in comparison to minimum NOx of 243 ppm under retard condition. At the maximum load of 3.7 kW, maximum NOx was found to be 813 ppm under advance condition. On the other hand, minimum amount of NOx about 342 ppm was emitted under retard condition for PF30. Basically the formation of the NOx emission in CI engines depends upon the three parameters (i) temperature of combustion inside the cylinder (ii) content of oxygen available in the engine Cylinder (iii) Reaction time [15-17]. For constant speed engine, higher combustion temperature is the main reason for formation of NOx emission [18, 19].
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S. Pal et al. / Materials Today: Proceedings 17 (2019) 209–215
Figure 6 explains the effect of injection timing on smoke emissions at 1.8 kW and 3.7 kW loads. In case of 1.8 kW load, maximum smoke opacity about 54.1% was observed for diesel under ideal condition while minimum smoke opacity was 24.3% for PF30 under ideal condition. Similarly, at 3.7 kW load, the maximum smoke opacity was found to be 49.1% under ideal condition for pure diesel and minimum smoke opacity was 24% for PF30 under advanced condition. On increasing the load, the smoke quantity increased significantly. The formation of the smoke pollutants occur in the combustion chamber where the sufficient air/oxygen is unavailable. The ratio of air-fuel in the chamber promote pollutant formation largely. On using the plastic oil, smoke pollutant is much higher with increasing engine load as compare to the pure diesel. Improper mixing of vaporised fuel particles with air led the heterogeneous combustion with the use of plastic oil in CI engines [20].
Figure 5: Effect of injection timing on oxides of nitrogen emissions
Figure 6: Effect of injection timing on smoke emissions 4. Conclusions It was concluded that the test engine operation was smooth until certain percentage of plastic fuel blending with diesel i.e., 30% beyond which the operation was not smooth. Retarded fuel injection timing resulted in lower efficiency and higher emissions. However, advancing the fuel injection timing is the viable option to solve the problem of lower thermal efficiency and higher carbon-based emissions. Acknowledgements Authors would like to thank the Department of Science and Technology, New Delhi, India for the financial support (Grant No: ECR/2017/000185) to carry out the experiments.
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215
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7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20.
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