Page 184 - Biofuels Refining and Performance

Processing of Vegetable Oils as Biodiesel and Engine Performance 167

Wagner et al. [13] have conducted tests on a number of diesel engines
with different blends of winter rape and safflower oil with diesel fuel.
The following specific conclusions were drawn from the results obtained:

High viscosity and tendency to polymerize within the cylinder were
major physical and chemical problems.
Attempt to reduce the viscosity of the oil by preheating the fuel by
increasing the temperature of the fuel at the injector to the required
value was not successful.
Short-term engine performance showed power output and fuel con-
sumption equivalent to diesel fuel.
Severe engine damage occurred within a very short duration when the
test was conducted for maximum power with varying engine rpm
(revolutions per minute).
A blend of 70% winter rape with 30% diesel was successfully used for
50 h. No adverse effect was noted.
A diesel injector pump when run for 154 h with safflower oil had no
abnormal wear, gumming, or corrosion.
Borgelt et al. [14] have conducted tests on three diesel engines con-
taining 25–75% and 50–50% soybean oil and diesel. The engines were
operated under 50% load for 1000 horsepower (HP); the output ranged
from 2.55 to 2.8 kW. Thermal efficiency ranged from 19.3 to 20%. Engine
performances were not significantly different. Carbon deposit increased
with increased percentage of soybean oil. Thus, Borgelt et al. concluded
that use of 25% or less soybean oil caused negligible changes in engine
performance.
Barsic and Humke [15] performed a study in which blends of unre-
fined peanut and sunflower with diesel fuel (50–50%) were used in a
single-cylinder engine. The engine produced equivalent power or a minor
increase (6%) with vegetable oils and blends, with a 20% increase in spe-
cific fuel consumption. Performance tests at equal energy showed that
the power level remained constant or decreased slightly, thermal effi-
ciency decreased slightly, and the exhaust temperature increased with
an increase in the percentage of vegetable oil in the fuel. Exhaust emis-
sion at equal energy input showed slightly higher NO for vegetable oils
x
and their blends. Unburned hydrocarbon emission was about 50% higher
than pure diesel fuel because the injection system was not optimized for
more viscous fuels. Ziejewski et al. [16] reported the results of an
endurance test using a 25–75% blend of alkali-refined sunflower oil with
diesel and 25–75% blend of safflower oil with diesel on a volume basis. The
major problems experienced were premature injection, determination of
nozzle performance, and heavier carbon deposits in the piston ring grooves.