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Energy & Fuels 2008, 22, 652–656
Experimental Investigation on the Fuel Properties of Biodiesel and Its Blends at Various Temperatures Seung Hyun Yoon,† Su Han Park,† and Chang Sik Lee*,‡ Graduate School of Hanyang UniVersity, 17 Haengdang-dong, Sungdong-gu, Seoul 133-791, Korea Department of Mechanical Engineering, Hanyang UniVeristy, 17 Haengdang-dong, Sungdong-gu, Seoul 133-791, Korea ReceiVed April 25, 2007. ReVised Manuscript ReceiVed September 13, 2007
An experimental investigation was performed to find out the fuel properties including specific gravity, density, and viscosity of diesel and biodiesel fuel in the temperature range from 0 to 200 °C. Test fuels used were a conventional diesel, neat biodiesel (100% methyl ester of soybean oil), and their blends with blending ratios of 20%, 40%, 60%, and 80%. In order to analyze the fuel properties, the experiments were carried out at various temperatures for each of the six test fuels and the resulting measurements of the biodiesel and its blends were compared with the properties of conventional diesel fuel. In this work, the specific gravity of biodiesel fuel increased with the increase of the blending ratio of biodiesel and gradually decreased as the fuel temperature increased linearly. The density value measurement was correlated as a function of fuel temperature and blending ratio by an empirical equation. The viscosity of the test fuels was found to decrease linearly with increasing temperature and decreasing blending ratio. The kinematic viscosity obtained by this investigation agrees well with the empirical equation which is derived from the measured results.
1. Introduction Biodiesel fuels derived from vegetable oils or animal fats and which are used as substitutes for conventional petroleum fuel in diesel engines have recently received increased attention. This interest is based on a number of properties of biodiesel including its biodegradability and the fact that it is produced from a renewable resource. These features of biodiesel lead to its greatest advantage, which is its potential for emission reduction. Though the environmental potential for emissions reduction exists, vegetable oils have high viscosity and high pour points relative to diesel fuel. The high viscosity of vegetable oils such as biodiesel and its blends tend to alter the injector spray pattern inside the engine, causing fuel impingement on the piston and other combustion chamber surfaces. This leads to the formation of carbon deposits in the engine, eventually resulting in problems such as stuck piston rings in the cylinder and subsequent engine failures, which would not otherwise occur using diesel fuel. The undesirable characteristics of vegetable oils can be substantially mitigated by replacing the triglyceride molecules present in the oils with lighter alcohol molecules such as methanol or ethanol. This reaction is carried out in the presence of a catalyst and produces glycerol in addition to transesterfied vegetable oils that are given the generic name of biodiesel.1,2 The positive effects of biodiesel on diesel engine emissions have been demonstrated by a number of previous studies.3–6 The regulated and unregulated exhaust emissions from diesel engines * Corresponding author. Tel.: +82-2-2220-0427. Fax: +82-2-2281-5286. E-mail:
[email protected]. † Graduate School of Hanyang University. ‡ Hanyang Univeristy. (1) Bechtold R. L. AlternatiVe Fuels; Society of Automotive Engineers: Warrendale, PA, 2002. (2) McDonald, J.; Kittelson, D. B. 950400, Society of Automotive Engineers: Warrendale, PA, 1995. (3) Sharp, C. A.; Howell, S. A.; Jobe, J. 2000-01-1967, Society of Automotive Engineers: Warrendale, PA, 2000.
with biodiesel and blended fuel were measured by Sharp et al.3,4 In their research, it was shown that the measurable HC emissions were generally eliminated, while CO was reduced roughly 40% by using a neat biodiesel. However, the NOx emissions increased by 12% due to the oxygen content in biodiesel. Dorado et al.5 investigated the reduction characteristics of biodiesel fuel in a diesel engine in a comparison between the emissions of diesel fuel and the exhaust emissions of biodiesel derived from waste olive oil. This revealed that used olive oil methyl ester can significantly reduce emissions of CO (emission reduction of 58.9%), CO2 (8.6%), NO (37.5%), and SO2 (57.7%) compared to diesel fuel. While biodiesel does have numerous advantages, it has different properties compared with diesel fuel, as listed in Table 1. It has a higher viscosity, specific gravity, density, cloud point, and pour point than petroleum diesel fuel, and these specificities have a significant influence on the fuel spray atomization and evaporation characteristics, resulting in changes in the combustion process.6,7 In actual engine operation, fuel temperature in the injector nozzle sac ranges from 160 to 260 °C.8 Therefore, the effect of fuel temperature on fuel properties such as specific gravity, density, and viscosity behavior is very important. Many researchers have developed methods and empirical models for measuring and predicting specific gravity,9,10 den(4) Sharp, C. A.; Howell, S. A.; Jobe, J. 2000-01-1968, Society of Automotive Engineers: Warrendale, PA, 2000. (5) Dorado, M. P.; Ballesteros, E.; Arnal, J. M.; Gomez, J.; Lopez, F. J. Fuel 2003, 82, 1311–1315. (6) Lee, C. S.; Park, S. W.; Kwon, S. I. Energy Fuels. 2005, 19, 2201– 2208. (7) Arregle, J. M.; Desantes, J. M.; Pastor, J. V.; Delage, A. 980802, Society of Automotive Engineers: Warrendale, PA, 1998. (8) Kato, M.; Takeuchi, H.; Koie, K.; Sekijima, H.; Kajitani, S.; Chen, Z. L.; Hashimoto, S. 2004-01-0081, Society of Automotive Engineers: Warrendale, PA, 2004.
10.1021/ef7002156 CCC: $40.75 2008 American Chemical Society Published on Web 11/15/2007
Properties of Biodiesel and Blends
Energy & Fuels, Vol. 22, No. 1, 2008 653
Table 1. Specifications of Diesel and Biodiesel Fuels16
Table 2. Test Fuels
fuel property
diesel
biodiesel
fuel type
abbreviation
fuel standard lower heating value, Btu/gal kinematic viscosity, @ 40 °C specific gravity, kg/L @ 60 °F density, lb/gal @ 15 °C water and sediment, vol % carbon, wt % hydrogen, wt % oxygen, by dif. wt % sulfur, wt % boiling point, °C flash point, °C cloud point, °C pour point, °C cetane number lubricity SLBOCLE, g lubricity HFRR, µm
ASTM D 975 ∼129050 1.3–4.1 0.85 7.079 0.05 max 87 13 0 0.05 max 180–340 60–80 -15 to 5 -35 to -15 40–55 2000–5000 300–600
ASTM D 6751 ∼118170 4.0–6.0 0.88 7.328 0.05 max 77 12 11 0.01–0.0024 315–350 100–170 -3 to 12 -15 to 10 48–65 >7000
