Properties of biodiesel
The fuel properties of raw vegetable oil as listed in
Table 1 indicate that the kinematic viscosity of vegetable oil
varies in the range of 30–40 cSt at 38°C. The high viscosity of
these oils is because of their large molecular mass in the range
of 600–900 kg/m
3
. This is about 20 times higher than that of
diesel fuel. The flash point of vegetable oil is very high (above
200°C). The heating values are in the range of 39–40 MJ/kg
compared to 45 MJ/kg for diesel fuel. Heating values of various
vegetable oils are nearly 90% of diesel fuel. The presence of
chemically bound oxygen in vegetable oil lowers their heating
values by about 10%. The cetane numbers are in the range of
35–50 [6] and is similar or close to that of diesel fuel. Long
chain saturated, unbranched hydrocarbons are especially suitable
for conventional diesel fuel. The long, unbranched hydrocarbon
chains in the fatty acids meet this requirement. The above unique
properties of vegetable oils helpus to replace the conventional
diesel fuel. Wang et al. [7] reported that the major disadvantage
of vegetable oils is their inherent high viscosity. Modern diesel