Oil with high free fatty acid (FFA) content may not be an
appropriate contestant for biodiesel production due to poor process
yield. The high FFA content (≻1%) will cause soap formation and the
separation of products will be exceedingly difficult, and as a
result, it has low yield of biodiesel product. In order to increase
the process yield, pretreatment setup is required. This involves
additional cost and will increase overall fuel price. Hence crude
vegetable oils having high FFA can be blended with diesel for
effectual employment in diesel engines. In this context, Jatropha
Curcas L, non-edible tree-based oil with higher FFA content, can be
considered as one of the prominent blending sources for diesel. The
primary objective of the present work is to analyze the effect of
FFA content of crude Jatropha Curcas L oil (CJO) on performance and
emission characteristics of a direct injection (DI) diesel engine.
The effect of FFA on some of the critical fuel properties was also
investigated.
In the present study, the CJO with five different FFA
percentages (5.1, 7.6, 10.1, 12.7, and 14.9 %) were collected and
blended in the ratio of 80:20 (diesel:CJO) on volume basis. The
effect of FFA content on density, viscosity, cetane number, heating
value, volatility characteristics, and oxidative stability was
investigated. From the measurements it was observed that the
density, viscosity, and distillation temperatures were found to
increase with increase in FFA content in the blend; while cetane
number, heating value, and oxidative stability were observed to
decrease with increase in FFA content. As compared to diesel,
density, kinematic viscosity, and distillation temperatures were
higher for such blends and the difference in magnitude ranges by 3
to 7.5% for density, 2.2 to 4.6 times in kinematic viscosity, and
by 24 to 58°C in T50 temperature. However, cetane number of the
blends increased while the heating value decreased when compared to
diesel. The cetane number of blends was found to be higher by 4.3
to 19.1%; whereas heating value was observed to be decreased by 3
to 7.9% as compared to diesel. To study the performance and
emissions, tests were carried out in a DI diesel engine at
different loads. The effect of FFA content on brake specific fuel
consumption, brake thermal efficiency, oxides of nitrogen, and
smoke was investigated. It is found that the brake thermal
efficiency and smoke decrease; while oxides of nitrogen increases
with increase in FFA content. The magnitude ranges by 0.33 to 2.04%
in brake thermal efficiency, 5.4 to 27% in smoke, and 3.4 to 21.7%
in oxides of nitrogen for blends as compared to diesel. From the
present study, it can be concluded that the blend of CJO (80:20
diesel:CJO) up to 5.1% FFA content can be considered as a potential
blending agent for diesel fuel.