Energy Fuels 2010, 24, 6156–6165 Published on Web 10/14/2010
: DOI:10.1021/ef100899z
Reducing Emissions of a Diesel Engine Using Fumigation Ethanol and a Diesel Oxidation Catalyst K. S. Tsang,† Z. H. Zhang,‡ C. S. Cheung,*,† and T. L. Chan† †
Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China, and ‡State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China Received July 14, 2010. Revised Manuscript Received September 24, 2010
Experiments were conducted on a four-cylinder direct-injection diesel engine with part of the engine load taken up by fumigation ethanol, which was injected into the air intake of each cylinder, to investigate the combustion and emissions of the engine under five engine loads at an engine speed of 1800 rpm. Fumigation ethanol was injected to top up 5, 10, 15, and 20% of the engine loads under different engine-operating conditions. In comparison to Euro V diesel fuel, fumigation ethanol gives a higher peak in-cylinder pressure and heat release rate. Increasing the fumigation ethanol would increase the ignition delay. More fuel is burned in the premixed mode, and less fuel is burned in the diffusion mode. The brake thermal efficiency decreases with an increase in fumigation ethanol at low and medium engine loads but does not change significantly at high engine loads. On the emission side, the application of fumigation ethanol results in a significant increase in hydrocarbon (HC), carbon monoxide (CO), and nitrogen dioxide (NO2) emissions. However, there is a decrease in nitrogen oxides (NOx), smoke, and particulate mass and number concentrations. The diesel oxidation catalyst is able to reduce the high emissions of CO and HC arising from fumigation ethanol and, in addition, further reduce the particulate emissions.
(CO2), but carbon monoxide (CO), acetaldehyde, and unburned ethanol increased at most operating conditions. Can et al.5 analyzed the effects of ethanol addition on the performance and emissions of a turbocharged indirect-injection (IDI) diesel engine. Their results showed that the ethanol addition reduced CO, soot, and sulfur dioxide (SO2) but caused an increase in NOx emission and approximately 12.5 and 20% power reduction, respectively, for 10 and 20% ethanol addition. Merritt et al.7 investigated three Tier II non-road diesel engines on emissions and found that smoke and particulate emissions decreased with increasing ethanol content. Changes to CO and NOx varied with engine design, with some increased and some decreased. Alcohol fumigation is a form of dual-fuel engine operation in which the alcohol is premixed with the intake air by injection or vaporization of alcohol, while the diesel fuel is injected directly into the cylinder as in a traditional diesel engine. The fumigation method requires minor modification of the engine, so that the alcohol can be injected into the air intake using low-pressure fuel injectors. The application of fumigation methanol on diesel engines is available in the literature.8-12 Cheng et al.10 conducted investigations on the performance and gaseous and particulate emissions using
1. Introduction The application of alternative fuels in diesel engines has drawn increasing interest because of the decrease in world petroleum reserves, the increase in the price of conventional petroleum fuels, and the tightening of exhaust emission standards on diesel engines. Among the alternative fuels, ethanol is one of the most widely investigated for use in combination with diesel fuel.1,2 Saeed and Henein3 reviewed the combustion of ethanol in compression ignition engines and suggested that there are difficulties in the use of ethanol because of its low cetane number, long ignition delay, high latent heat of vaporization, and poor autoignition capability. Several techniques can be applied to tackle these problems,4,5 which include alcohol fumigation, dual injection, and alcoholdiesel blends. Many researchers have investigated the effect of ethanoldiesel blends on the performance and emissions of diesel engines. He et al.6 tested different proportions of ethanoldiesel blends on regulated and unregulated emissions from a diesel engine. They concluded that the blended fuel could reduce smoke, nitrogen oxides (NOx), and carbon dioxide *To whom correspondence should be addressed: Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong. Telephone: þ852-2766-7819. Fax: þ852-2365-4703. E-mail:
[email protected]. (1) Hansen, A. C.; Zhang, Q.; Lyne, P. W. L. Bioresour. Technol. 2005, 96, 277–285. (2) Demirbas, A. Prog. Energy Combust. Sci. 2007, 33, 1–18. (3) Saeed, M. N.; Henein, N. A. J. Eng. Gas Turbines Power 1989, 111, 439–444. (4) Abu-Qudais, M.; Haddad, O.; Qudaisat, M. Energy Convers. Manage. 2000, 41, 389–399. (5) Can, O.; Celikten, I.; Usta, N. Energy Convers. Manage. 2004, 45, 2429–2440. (6) He, B. Q.; Shuai, S. J.; Wang, J. X.; He, H. Atmos. Environ. 2003, 37, 4965–4971. r 2010 American Chemical Society
(7) Merritt, P. M.; Ulmet, V.; McCormick, R. L.; Mitchell, W. E.; Baumgard, K. J. SAE Tech. Pap. 2005-01-2193; Society of Automotive Engineers (SAE) International: Warrendale, PA, 2005. (8) Yao, C. D.; Cheung, C. S.; Cheng, C. H.; Wang, Y. S. Energy Fuels 2007, 21, 689–691. (9) Yao, C. D.; Cheung, C. S.; Cheng, C. H.; Wang, Y. S.; Chan, T. L.; Lee, S. C. Energy Convers. Manage. 2008, 49, 1696–1704. (10) Cheng, C. H.; Cheung, C. S.; Chan, T. L.; Lee, S. C.; Yao, C. D. Sci. Total Environ. 2008, 389, 115–124. (11) Song, R. Z.; Liu, J.; Wang, L. J.; Liu, S. H. Energy Fuels 2008, 22, 3883–3888. (12) Zhang, Z. H.; Cheung, C. S.; Chan, T. L.; Yao, C. D. Sci. Total Environ. 2009, 407, 4497–4504.
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Energy Fuels 2010, 24, 6156–6165
: DOI:10.1021/ef100899z
Tsang et al.
fumigation methanol and concluded that there was an increase in hydrocarbon (HC), CO, and nitrogen dioxide (NO2) and a decrease in NOx, smoke opacity, and particulate mass concentrations. Similar results were obtained by Song et al.11 and Zhang et al.12 There were active investigations on diesel engines operating with fumigation ethanol in the 1980s. Broukhiyan and Lestz13 have determined the effect of ethanol fumigation on engine fuel efficiency, gaseous emissions, smoke, raw particulate, and engine knocking. Hayes et al.14 also conducted similar tests on the effect of fumigation ethanol on gaseous emissions and in-cylinder pressure. They showed that HC and CO increased several times over diesel-only operation. The maximum rate of pressure rise and peak pressure was also significantly higher with fumigation ethanol. The NOx emissions were lower than diesel. Jiang et al.15 investigated the effect of ethanol fumigation on the performance and emissions of a four-cylinder, turbocharged diesel engine. They found that NOx decreased but CO and HC increased greatly with ethanol fumigation in comparison to diesel fuel. More recently, Abu-Qudais et al.4 compared the diesel engine performance and emissions using separately fumigation ethanol and ethanol-diesel blends. The results showed that both methods have similar effects on engine performance and emissions, but the improvement in using the fumigation method is better. Leahey et al.16 also suggested that fumigation ethanol could be a viable method of offsetting petroleum diesel while lowering diesel soot emissions and avoiding lubricity problems potentially associated with ethanol-diesel blended fuel. Surawski et al.17 focused their work on particle emissions and their toxicity from an ethanol-fumigated compression ignition engine. Previous research pays more attention to test the gaseous emissions and smoke on the application of fumigation ethanol to diesel engine. However, there is lack of investigation on the particulate emissions on mass or number concentration. In addition, the diesel fuel used in previous research has a high sulfur content of 0.25% by weight.15 Moreover, none of them applied the diesel oxidation catalyst to reduce the increase in HC and CO emissions. The objective of this study is, therefore, to investigate the effects of different percentages of fumigation ethanol, using Euro V diesel fuel as the baseline fuel, on the performance and gaseous and particulate emissions of a diesel engine, with and without using a diesel oxidation catalyst. Combustion characteristics are also analyzed to relate to the changes in particulate and NOx.
Table 1. Engine Specifications model type maximum power maximum torque bore stroke displacement compression ratio fuel injection timing (BTDC) injection pump type injection nozzle
Isuzu 4HF1 in-line four-cylinder 88 kW/3200 revolutions/min 285 N m/1800 revolutions/min 112 110 mm 4334 cm-3 19.0:1 8° Bosch in-line type hole type (with five orifices)
Table 2. Properties of Euro V Diesel Fuel and Ethanol properties
Euro V diesel
ethanol
molecular weight (g/mol) cetane number density (kg/m3) heat of vaporization (kJ/kg) lower heating value (MJ/kg) viscosity at 40 °C (mPa s) carbon content (wt %) hydrogen content (wt %) oxygen content (wt %) sulfur content (mg/kg)
190-220 >51 830 270 42.5 2.8 86.9 13.1 0
