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Energy & Fuels 2008, 22, 906–914
Emissions Characteristics of a Diesel Engine Fueled with Biodiesel and Fumigation Methanol C. S. Cheung,*,† Chuanhui Cheng,†,‡ T. L. Chan,† S. C. Lee,§ Chunde Yao,‡ and K. S. Tsang† Departments of Mechanical Engineering and CiVil and Structural Engineering, The Hong Kong Polytechnic UniVersity, Hong Kong, China, and State Key Laboratory of Engines, Tianjin UniVersity, Tianjin 300072, China ReceiVed July 10, 2007. ReVised Manuscript ReceiVed December 10, 2007
Currently, considerable attention has been given to the investigation of biofuels, including biodiesel, as alternative fuels for internal combustion engines. This study is aimed to investigate the effects of fumigation methanol on the emissions of a diesel engine fueled with biodiesel as the baseline fuel. The biodiesel used in this study was converted from waste cooking oil. Experiments were performed on a 4-cylinder naturally aspirated diesel engine operating at a constant speed of 1800 rev/min for three engine loads. The results indicate no significant change in brake thermal efficiency and carbon dioxide (CO2) emission, an increase in both carbon monoxide (CO) and unburned hydrocarbon (HC) emissions, and a decrease in both nitrogen oxides (NOx) and particulate matter (PM) emissions. In particular, there is also an increase in nitrogen dioxide (NO2) in the exhaust gas. The results obtained at a fumigation ratio of 0.1 are compared with those obtained with the engine operating on ultralow sulfur diesel: there is still an increase in CO and HC, by a factor of up to two, and an increase in NO2, by a factor of up to 5, while the NOx is reduced by up to 8% and the particulate mass is reduced by up to 50%, depending on the engine load.
Introduction Motor vehicles running on fossil fuels, in particular diesel vehicles, are major sources of street level air pollution in many cities. To improve air quality, more and more stringent emission regulations have been implemented for reducing exhaust emissions from new diesel vehicles. Correspondingly, there is a demand for reducing exhaust emissions from in-use diesel vehicles. One of the possible ways to reduce exhaust emissions from existing diesel vehicles is through improvement of the fuel being used or using alternative fuels.1–3 Recently, the emission of CO2 has also attracted greater and greater attention. To reduce CO2 emission, biofuels such as alcohols and biodiesel have been proposed as alternatives for internal combustion engines.4,5 Biofuels are considered to be renewable and more environmentally acceptable than the petroleum fuels.6,7 In particular, biodiesel has received wide attention for application to in-use diesel engines as a replacement of diesel fuel. * Corresponding author. E-mail address:
[email protected]. Tel.: +852-2766 7819. Fax: +852-2365 4703. † Department of Mechanical Engineering, The Hong Kong Polytechnic University. ‡ Tianjin University. § Department of Civil and Structural Engineering, The Hong Kong Polytechnic University. (1) Wang, W. G.; Clark, N. N.; Lyons, D. W.; Yang, R. M.; Gautam, M.; Bata, R. M.; Loth, J. L. EnViron. Sci. Technol. 1997, 31, 3132–3137. (2) Wang, W. G.; Lyons, D. W.; Clark, N. N.; Gautam, M. EnViron. Sci. Technol. 2000, 34, 933–939. (3) Lim, M. C. H.; Ayoko, G. A.; Morawska, L.; Ristovski, Z. D.; Jayaratne, E. R. Atmos. EnViron. 2005, 39, 7836–7848. (4) Agarwal, A. K. Prog. Energy Combust. Sci. 2007, 33, 233–271. (5) Demirbas, A. Prog. Energy Combust. Sci. 2007, 33, 1–18. (6) Cvengroš, J.; Považanec, F. Bioresour. Technol. 1996, 55, 145–152. (7) A comprehensiVe analysis of biodiesel impacts on exhaust emissions; EPA420-P-02-001, USEPA: Washington, D.C., 2002.
Biodiesel is biodegradable and nontoxic and can significantly reduce toxic emissions and overall life cycle emission of CO2 when used as a fuel for diesel engines. Several studies have found that the use of biodiesel in diesel engines results in significant reduction of hydrocarbon (HC), CO, and particulate matter (PM); however, emissions of NOx may increase, especially at high engine loadings.7–9 The increase in NOx emission is one of the disadvantages of using biodiesel in diesel engines; thus, some investigations have been carried out to mitigate the increase in NOx. Leung et al.10 studied and optimized the performance of a single-cylinder diesel engine fueled with biodiesel through adjusting engine setting to achieve HC and PM reduction while maintaining the same level of NOx emissions, compared with the diesel fuel. Szybist et al.11 suggested the use of cetane improving additives and modified feedstock composition to reduce NOx emission from biodiesel fueled diesel engines. One of the most effective ways to reduce NOx emission is to lower the temperature inside the engine cylinder using water injection, water emulsified biodiesel, ignition timing retardation, or exhaust gas recirculation.12 However, most of the methods will normally lead to deterioration in engine performance. Thus, further investigation on (8) Schumacher, L. G.; Borgelt, S. C.; Fosseen, D.; Goeta, W.; Hires, W. G. Bioresour. Technol. 1996, 57, 31–36. (9) Sharp, C. A.; Howell, S. A.; Jobe, J. The effect of biodiesel fuels on transient emissions from modern diesel engines, part 1 regulated emissions and performance; SAE paper 2000-01-1967, Society of Automotive Engineers: Warrendale, PA, 2000. (10) Leung, D. Y. C.; Luo, Y.; Chan, T. L. Energy Fuels 2006, 20, 1015–1023. (11) Szybist, J.; Simmons, J.; Druckenmiller, M.; Al-Qurashi, K.; Boehman, A.; Scaroni, A. Potential methods for NOx reduction from biodiesel; SAE paper 2003-01-3205, Society of Automotive Engineers: Warrendale, PA, 2003. (12) Fernondo, S.; Hall, C.; Jha, S. Energy Fuels 2006, 20, 376–382.
10.1021/ef7003915 CCC: $40.75 2008 American Chemical Society Published on Web 02/09/2008
Emissions with Biodiesel and Fumigation Methanol
reducing NOx emission from compression ignition engine fueled with biodiesel is required. Methanol and ethanol have been widely investigated for use in combination with diesel fuel to reduce pollution. The alcohol additives can lead to lower NOx emission due to reduction of in-cylinder gas temperature. Kumar et al.13,14 applied methanol in jatropha oil and ethanol in animal fat to a diesel engine, and found reduction of NO emission as well. Kowalewicz15–17 investigated the performance and emissions of a diesel engine fueled with biodiesel and fumigation ethanol and concluded that there was a reduction of NOx at low loads. Thus, the NOx reduction effect of the alcohol additives can extend to fuels other than the diesel fuel. Alcohol can be applied to a diesel engine either by blending together with the base fuel or by injecting it into the engine through the air intake ports. Chao et al.18 and Huang et al.19,20 investigated the exhaust emissions of a diesel engine using diesel fuel blended with methanol. However, due to poor miscibility between diesel fuel and methanol, the amount of methanol that can be applied is limited. On the other hand, Popa et al.21 and Yao et al.22 injected methanol to the air intake port of the diesel engine. In these cases, the amount of methanol that can be injected is limited by the occurrence of engine knocking; but normally, a higher amount of alcohol can be applied. Biodiesel is made from renewable resources such as vegetable oils or animal fats through the transesterification process.23 It can also be converted from waste cooking oil.24 There are increasing interests in applying biodiesel converted from waste cooking oil for its lower cost and its added advantage of reducing waste oil disposal.25,26 This study investigated the performance of a diesel engine operating on biodiesel converted from waste cooking oil for different quantities of fumigation methanol. The engine performance in terms of brake thermal efficiency, the gaseous emissions of CO2, CO, HC, NOx, NO, and NO2, and the particulate mass concentration, as well as the particulate number concentration and size distributions, were compared. This study investigated in particular the benefits in NOx reduction using biodiesel with fumigation methanol, which has not been reported in the literature. Finally, the performance of the engine operating (13) Kumar, M. S.; Ramesh, A.; Nagalingam, B. Biomass Bioenerg. 2003, 25, 309–318. (14) Kumar, M. S.; Kerihuel, A.; Bleelttre, J.; Tazerout, M. Fuel 2006, 85, 2646–2652. (15) Kowalewicz, A. Proc. Inst. Mech. Eng. Part D-J. Automobile Eng. 2005, 219, 715–723. (16) Kowalewicz, A. Proc. Inst. Mech. Eng. Part D-J. Automobile Eng. 2006, 220, 1275–1282. (17) Kowalewicz, A. Proc. Inst. Mech. Eng. Part D-J. Automobile Eng. 2006, 220, 1283–1291. (18) Chao, M. R.; Lin, T. C.; Chao, H. R.; Chang, F. H.; Chen, C. B. Sci. Total EnViron. 2001, 279, 167–179. (19) Huang, Z. H.; Lu, H. B.; Jiang, D. M.; Zeng, K.; Liu, B.; Zhang, J. Q.; Wang, X. B. Proc. Inst. Mech. Eng. Part D-J. Automobile Eng. 2004, 218, 435–447. (20) Huang, Z. H.; Lu, H. B.; Jiang, D. M.; Zeng, K.; Liu, B.; Zhang, J. Q.; Wang, X. B. Bioresour. Technol. 2004, 95, 331–341. (21) Popa, M. G.; Negurescu, N.; Pana, C.; Racovitza, A. Results obtained by methanol fuelling diesel engine; SAE paper 2001-01-3748, Society of Automotive Engineers: Warrendale, PA, 2001. (22) Yao, C. D.; Cheung, C. S.; Cheng, C. H.; Wang, Y. S. Energy Fuels 2007, 21, 686–691. (23) Ma, F.; Hanna, M. A. Bioresour. Technol. 1999, 70, 1–15. (24) Kulkarni, M. G.; Dalai, A. K. Ind. Eng. Chem. Res. 2006, 45, 2901– 2913. (25) Wang, Y.; Ou, S. Y.; Liu, P. Z.; Zhang, Z. S. Energy ConVers. Manage. 2007, 48, 184–188. (26) Canakci, M. Bioresour. Technol. 2007, 98, 183–190.
Energy & Fuels, Vol. 22, No. 2, 2008 907
Figure 1. Schematic of the experimental system. Table 1. Specifications of the Test Engine model
Isuzu 4HF1
type max. power/speed (kW/rpm) max. torque/speed (Nm/rpm) bore/stroke (mm) displacement(cc) compression ratio
In-line 4-cylinder 88/3200 285/1800 112 × 110 4334 19.0:1
Table 2. Properties of Biodiesel, Methanol, and ULSD property
biodiesel
methanol
ULSD
cetane number lower heating value (MJ/kg) density (kg/m3)@20 °C viscosity (mPa · s)@40 °C flash point (°C) carbon content (% mass) hydrogen content (% mass) oxygen content (% mass) sulfur content (mg/kg)
51 37.5 871 4.6 210 80.0 10.2 9.8
