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320 Advances in Eco-Fuels for a Sustainable Environment

Fig. 11.3 Fatty acid composition of AMC biodiesel.

11.3.3 Physicochemical characterization of AMC oil and biodiesel
The determined physicochemical properties of diesel, AMC oil, and AMC biodiesel
are listed in Table 11.2.

11.3.3.1 Cetane number

The cetane number is the percentage by volume of hexadecane (known as cetane) in a
combustible mixture that contains cetane and 1-methylnaphthalene whose ignition
properties are similar or match with the fuel that is being tested. The one ignition prop-
erty that is compared here is engine knock.
Cetane (Hexadecane)—C 16 H 34
Alpha-methyl naphthalene—C 11 H 10
Ignition delay in fuel is defined as the approximate period between the start of
injection of fuel and the first observed pressure rise during combustion of the fuel,
and according to experimental studies, the cetane number is inversely proportional
to the fuel’s ignition delay. When the fuel enters the cylinder, it needs to be atomized,
then mixed with air. Then its temperature must be raised, and the chemical reaction of
combustion takes its time. All these times added is the ignition delay. So the cetane
number is a rating that indicates how long the ignition delay of the fuel as compared to
that of cetane. The cetane number of AMC biodiesel, Karanja, and Jatropha were
found to be 58, 42.9, and 49.5, respectively.
The following observations can be made from Fig. 11.4.