buletinul institutului politehnic din iaşi - Universitatea Tehnică ...
buletinul institutului politehnic din iaşi - Universitatea Tehnică ...
buletinul institutului politehnic din iaşi - Universitatea Tehnică ...
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Bul. Inst. Polit. Iaşi, t. LVIII (LXII), f. 4, 2012 143<br />
diagnostic engine combustion models. Additionally, it is necessary to know if<br />
the fuel resulting from the blen<strong>din</strong>g process meets the standard specifications<br />
for diesel fuels. Given the difficulty of obtaining the combustion properties of<br />
the blend by measurement, the ability to calculate these properties using<br />
blen<strong>din</strong>g or mixing rules is very useful.<br />
Some authors (Clements, 1996) proposed blen<strong>din</strong>g rules for estimating<br />
the density, heating value, viscosity, cetane number and cloud point of biodiesel<br />
as a function of its methyl esters profile. By comparing predicted values with<br />
experimental data, they found that the typical average errors were less than 2%,<br />
with the exception of viscosity, where the average error was 10%. Similar<br />
blen<strong>din</strong>g rules for calculating properties of methyl ester blends have also been<br />
used by other researchers for estimating properties of biodiesel–diesel blends.<br />
Tat and Van Gerpen (Tat & Van Gerpen, 1999, Tat & Van Gerpen, 2000)<br />
carried out a study on the density and kinematic viscosity of a commercial<br />
soybean oil biodiesel and its blends with two samples of diesel fuels at 75%,<br />
50% and 20% biodiesel (by weight). Results showed that both density and<br />
viscosity increased with the increase in the percentage of biodiesel. Blend<br />
kinematic viscosities were estimated by means of a blen<strong>din</strong>g rule. The<br />
maximum differences between predicted and measured viscosities were less<br />
than 3.74% of the measured values for the biodiesel blends with both diesel<br />
fuels. Experimental investigations have been carried out by Yuan, Hansen and<br />
Zhang (Yuan et al., 2004) to examine the density using three types of biodiesel<br />
(two produced from soybean oil and another biodiesel prepared from yellow<br />
grease). These were blended with diesel fuel at 75%, 50% and 25% biodiesel<br />
(by weight), and tested from close to the biodiesel crystallization onset<br />
temperature up to 100 o C. The measurements indicated that all biodiesel fuels<br />
and their blends with diesel fuel had a linear specific gravity–temperature<br />
relationship similar to pure diesel fuel. The densities of the blends estimated by<br />
a mixing rule showed an average absolute deviation (AAD) of less than 0.43%<br />
for all tested fuels in the temperature range studied.<br />
The present paper presents experimental density and viscosity data,<br />
together with the flash point and distillation curves for rapeseed oil biodiesel<br />
and its blends with diesel fuel. Additionally, the calculated cetane index and<br />
heating value of the tested neat fuels and their blends is obtained by ASTM<br />
D976 and ASTM D4737 for cetane index and ASTM D4868 for heating value<br />
recommended for hydrocarbon fuels. The aim of this work is to evaluate mixing<br />
rules for predicting the combustion properties of rapeseed oil biodiesel–diesel<br />
fuel blends as a function of biodiesel content (volume fraction). This approach<br />
is more likely to be applicable to other biodiesel fuels and blends than empirical<br />
correlations, which would be valid only for the specific blends tested.