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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASAE.  VOL. 43(6): 1309-1316 . (doi: 10.13031/2013.3027) @2000
Authors:   K. P. McDonnell, S. M. Ward, P. B. McNulty, R. Howard-Hildige
Keywords:   Biodiesel, Engine testing, Rapeseed oil, SRO

The renewed interest in environmentally compatible fuels has led to the choice of rapeseed oil as the main alternative to diesel fuel in Europe. Transesterified rapeseed oil (viz. rape methyl ester) has been the predominant vegetable oil fuel used because its characteristics are quite similar to diesel. However, it is an expensive product due to high feedstock costs. The objective of this research was to produce and test an economic and high quality nonesterified rapeseed oil suitable for use as a diesel fuel extender. This was achieved by acidified hot water degumming combined with filtration to five microns. This rapeseed oil, designated as a Semi Refined Oil (SRO), has a high viscosity in comparison with diesel (589 mPas vs 22 mPas at 12C). Hence, SRO fuel can be used only as a diesel fuel extender at inclusion rates up to 25%, the resultant blend having a viscosity of 55 mPas at 12C. When used with direct injection (DI) engines, power output (at 540 rpm at the power take-off shaft) was reduced by c. 0.06% for every 1% increase in SRO inclusion rate, and brake specific fuel consumption (BSFC) increased by c. 0.14%/1% increase in SRO inclusion rate (viz. a 25% SRO/diesel blend had a 1.5% decrease in power and a 3.5% increase in BSFC compared with diesel). These values are in accordance with the lower energy density of rapeseed oil fuels compared with diesel. Chemical and viscosity analyses of engine lubrication oil using both diesel and a 15% SRO inclusion rate (after c. 170 h/fuel tested), including metal contamination as an indicator of engine wear, showed that there was no measurable effect on engine lubricating oil due to SRO inclusion in diesel oil. However, the injector fouling results showed that shorter injector service intervals are required. In contrast to the DI results, above, when SRO was used to fuel indirect injection (IDI) engines, power was considerably reduced mainly due to inadequate air/fuel mixing. As most agricultural tractors are DI, SRO has a potential as a diesel fuel extender for agricultural equipment.

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