|Knothe, Gerhard - Gary|
Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/14/1997
Publication Date: N/A
Technical Abstract: Biodiesel blends, consisting of a mixture of vegetable oil ester and diesel fuel, are being seriously considered for use as fuel in diesel engines. Selection of the best formulation of biodiesel blends has been hampered by a lack of data regarding the ignition and combustion characteristics of the fatty acids and esters. The objective of this work was to determine the relationships between the ignition characteristics and the composition of the fatty acid and esters. For this purpose, the ignition delay times of several different fatty acids (stearic, oleic, linoleic, and linolenic) and their methyl, ethyl, propyl, and butyl esters were measured at three different temperatures (426, 482, and 585 deg C) as the materials were injected into a high temperature, high-pressure combustion bomb. The ignition delay data were used to develop Arrhenius-type rate expressions for the ignition process. In addition, the ignition delay data were used to determine the cetane numbers of the materials and the effects of various cetane improving additives on the cetane numbers of selected materials. The results indicate that ignition characteristics are highly dependent on the chemical structure of the acids and esters, and that the sensitivity of the various materials to cetane improvement is also highly dependent on the structure of the base material and the additive.