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Exhaust Emissions From a Biodiesel-Fueled Direct Injection Industrial Diesel Engine
Published October 22, 2006 by Society of Automotive Engineers of Japan in Japan
Oils derived from vegetable-derived sources have long been considered as fuels for internal combustion engines but only recently have they received considerable recognition as alternate fuels for spark-ignition and compression-ignition engines. While there has been some interest in the 1980s in vegetable oils as diesel engine fuel, the motivation for its use subsided as the price of petroleum diesel decreased over the years. The new interest in biodiesel stems for the same reason as before but the increasing demand for petroleum fuels in the world is expected to keep interest in biodiesel fuel strong for years to come.
Soy-based methyl ester (transesterified soy oil) or soy-based biodiesel has properties that make the fuel viable for use in diesel engines. It has higher cetane number than diesel No 2 and contains oxygen by as much as 12% by weight. These and other differences in chemical and physical properties of biodiesel are expected to influence diesel engine performance. While B20 or biodiesel containing 20% soy methyl ester has been used in some commercial applications higher concentrations of soy methyl ester are uncommon. This investigation was conducted to evaluate the effects of biodiesel, containing up to 50% soy methyl ester, in an industrial type, naturally aspirated, DI diesel engine.
A 3-cylinder, naturally aspirated DI diesel engine was used in the investigation. Biodiesel fuels containing up to 50% soy methyl ester were used to fuel the engine up to its full calibrated load. Exhaust emissions of HC, NOx and smoke were measured at constant engine speed. The results show (a) higher concentration of biodiesel fuel reduced maximum bmep produced by the engine, (b) the exhaust concentration of oxides of nitrogen increased slightly as the biodiesel content in the blend increased, and (c) smoke and hydrocarbon emissions decreased as concentration of soy methyl ester in the blend increased.
The small reduction in power output is related to lower energy content of biodiesel blends while a detectable increase in oxides of nitrogen appeared to be related to fuel properties, which may tend to advance injection timing relative to pure diesel fuel.