Page 414 - Advances in Eco-Fuels for a Sustainable Environment

Engine modification for alternative fuels usage in diesel engine 367

measure of degree of saturation in the biodiesel. The iodine value of biodiesel is
49.49gI 2 /100g. The lesser iodine value showed more saturated fatty acid presence
in the biodiesel. Saturated fatty acid improves the fuel properties such as oxidation
stability, calorific value, and cloud and pour point. The saponification value of bio-
diesel is 98.11mgKOH/g oil. The saponification value is the mg of KOH required to
neutralize the amount (g) of oil. The cetane index is the indication of the ignition
quality of fuel. For the biodiesel, it is 65, which is higher than the diesel. Higher
cetane index leads to decreased ignition delay period and increased combustion
duration.

13.2.7 Fuel modification and selection of ternary blends

Biodiesel has high viscosity and lower calorific value but it has a high cetane number.
Higher viscosity increases the droplet size of the fuel due to poor atomization which
results in incomplete combustion and more exhaust emissions. To overcome those
problems, biodiesel was blended with alcohols.
The kinematic viscosity, cloud and pour point, and density of biodiesel improved
while blending with n-pentanol and n-hexanol. Various proportions of biodiesel-
diesel-n-pentanol and biodiesel-diesel-n-hexanol were mixed in a round-bottom flask
with a magnetic stirrer to get homogenous composition. Fuel quantity has varied from
0% to 100% in the range of 5% increments. The stability test was performed for all
combinations for 4weeks at atmospheric condition. Among the various proportions of
biodiesel-diesel-n-pentanol fuels, blends having above 75% of biodiesel and 5% die-
sel and <20% of n-pentanol were selected for further property characterization as the
other blends had a limitation of less flash and fire point, less miscibility, and less cal-
orific value. A ternary diagram of the biodiesel-diesel-n-pentanol fuel is shown in
Fig. 13.3.
Similar behavior was exhibited by various proportions of biodiesel-diesel-n-
hexanol blends. Blends having above 75% of biodiesel and 5% diesel and <20%
of n-hexanol were selected for further property characterization, as the other blends
had a limitation of less flash and fire point, less miscibility, and less calorific value.
Blends having n-hexanol content >20% have flash and fire point temperatures <32°
C. Therefore, it is highly unsafe to use higher n-hexanol content blends. A ternary dia-
gram of the biodiesel-diesel-n-hexanol blends is given in Fig. 13.4.
The biodiesel was perfectly miscible with diesel-n-pentanol and n-hexanol at an
atmosphere temperature of 32°C. The alcohols showed less miscibility with diesel.
However, in the ternary blends, the biodiesel acts as a surfactant and it creates micelles
having polar heads and nonpolar tails. These micelles are attracted to the polar or non-
polar solutes based on the direction of biodiesel molecules. The polar head of biodiesel
molecules was directed to the alcohol and biodiesel nonpolar tail was directed to die-
sel. As the biodiesel concentration was lower in the ternary blends, it led to
immiscibility.
From Table 13.3, it can be observed that the density of blends decreases with
an increase in the percentage of n-pentanol and n-hexanol concentration. Higher