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Fuel parameter testing, quality assessment and engine emissions evaluation of biodiesel (B100), diesel (D100) and its 20% blend (B20) under long term storage conditions

University of British Columbia

Diesel-powered vehicles have contributed to the emission of greenhouse gases into the atmosphere. Using biodiesel as a combustion fuel for use in diesel engines is advocated by engineers, environmentalists, industry and government for numerous reasons, including that it is derived from a renewable fuel source and can generate lower emissions than petroleum derived diesel fuel. However, biodiesel has reduced storage stability and is more prone to degradation reactions that can affect its fuel quality and cause changes in its fuel properties. The long-term ageing under real-time conditions of two different biodiesel (B100) fuels (from soybean oil and waste vegetable oils), two petroleum derived diesel (D100) fuels and their 20% vol. or B20 fuel blend was studied by storing these blends under cool (6 °C), ambient outdoor (X °C) and warm temperature (40 °C) conditions. The aged fuel samples were monitored via characterization of several fuel properties in accordance to ASTM and EN regulation standards up to 180 days and 300 days, in some cases. The purpose to meet the standards (e.g., ASTM, EN) is to ensure safe operation, good fuel quality and industrial longevity. The acid number (AN), kinematic viscosity (KV) and cetane number (CN) of the soy methyl ester (SME) after 300 days of ageing at 6 °C, X °C and 40 °C and waste methyl ester (WME) after 180 days of ageing at 6 °C and X °C did not change significantly. WME showed an increasing change in AN and KV after 180 days of ageing at 40 °C. Many of the fuel properties of aged SME and WME were comparable to its initial, un-aged values and were within the limits of technical specifications. The correlation between oxidative stability (OS) and iodine number (IN) was poor for both biodiesels. The analysis of the fatty acid methyl ester (FAME) profiles demonstrated the ineffectiveness of employing IN as a total measure of unsaturation for biodiesel fuels. The cloud point (CP) of WME was higher than SME and like KV, CN and OS; it strongly depended on the saturation and unsaturation content of the FAME. The D100 fuels displayed a near zero change in AN, minor increases in KV and adequate stability during storage. The CN of D100 decreased slightly and the measures were within the ASTM limits pre- and post-storage. Many fuel properties of the B20 pre-mix samples differed from the B20 after-mix samples, but these differences are not significant enough to conclusively deduce which B20 blend showed better stability. CN's of B20 were calculated from the measured cetane data of B100 and D100 and compared to the measured cetane data of B20. Select blends of aged Bl 00, D100 and B20 aged at 6 °C and 40 °C were tested for regulated pollutant emissions (HC, CO, NOx, CO₂) in a 1987 Volkswagen Jetta and a 2005 Mercedes Benz Smart Car. The vehicles were driven by the same driver for all test runs at cold start conditions. The effect of certain fuel properties and fuel composition was investigated on emission production. Relative to D100, the B100 and B20 fuels tested in the 1987 VW Jetta produced significantly lower emissions, with reductions in HC and CO of at least 40% and 15%, respectively. The B100 fuels showed a 12% increase in NOx. Storage temperature appeared to affect the produced emissions, particularly for B100 blends, but this effect is not as significant as the variations between the different fuel types (e.g., B100 versus D100). The emissions of B100 and B20 aged at 40 °C in the Smart car did not differ significantly and the results indicate the effect of fuel on emissions is small.

Text

2011-03-03

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http://hdl.handle.net/2429/31997

Chemical and Biological Engineering

University of British Columbia

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