[Back]

C. Roßboth, P. Hofmann, B. Geringer:
"Investigations in using higher FAME-blends in DI-CR-Dieselengines";
Talk: Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart, Haus der Wirtschaft, Stuttgart, Germany (invited); 2015-03-17 - 2015-03-18; in: "15.Internationales Stuttgarter Symposium,", (2015), 369 - 386.

Due to international market´s demand for higher blending rates of biogenic fuels, these
fuels came more and more into the focus of development requirements. Currently,
the biogenic components in diesel fuel mainly contain fatty acid methyl esters
(FAME). By now, in using these biofuels with higher blending rates (up from 7%)
various problems have been observed in the field, which are primarily caused by the
lower oxidation stability of FAME [1]. For this reason, the problem areas in motor
operation caused by highly advanced oxidation of the fatty acid chains in the biodiesel
have been systematically evaluated as part of a funded research project at the Institute
for Powertrains and Automotive Technology (IFA) of the Vienna University of Technology
in cooperation with a partner from the automotive industry. The special focus
of this paper lies in the main problematic aspect in using FAME fuels with higher
blending rates: the fuel aging. This oxidative ageing causes a possible polymerization
of the fatty acid structure which transforms these components in the fuel into a phase
characterized as viscous liquid or even solid [2]. As a result, the function of the fuel
supply system in the car - from the tank to the injectors - can be severely affected, or
at worst a total damage of the internal combustion engine can occur.
One aim of this study was to develop a methodology for accelerated aging of biodiesel
fuels with a continuous monitoring of the oxidation status. This ageing had to
be stopped shortly before the threshold state of building solid, polymeric structures in
the fuel was reached. For this purpose, a heated tank reactor system was constructed
and erected. With this chemical model experiment the naturally occurring aging of the
test fuels could be simulated under defined conditions.
Here the decrease of the oxidation stability was documented by periodic sampling and
chemical analyzes. The thus aged fuels were then subjected by a detailed analysis on
the engine test bench. The different fuels in different stages of aging were fired in
identical, direct-injection, turbocharged common rail diesel engines and their combustion
and emission behavior was examined based on motor parameter variations. At the
end of each experimental series with one fuel batch a 200-hour continuous test-run
was performed, to observe the behavior of biofuels with high FAME percentage in a
highly aged oxidation state with regard to long term operation. Special attention was
paid to the coking, sooting and forming of viscous residues at engine parts, in particular
the fuel injection system.

http://dx.doi.org/10.1007/978-3-658-08844-6_25