Abstract:
Vegetable oils are emerging as promising fuel substitutes to the conventional
petroleum fuels from the viewpoint of the energy crisis and emission problems.
These seem to be attractive substitute of diesel fuels. Vegetable oils have the
advantage of being geographically widely produced, in a variety of products and are
renewable in nature and thereby not contributing to the net atmospheric
concentrations of green house gas carbon dioxide.
However, higher viscosity and low volatility are identified as the main reasons for
the unsuitability of straight vegetable oils as the substitute of diesel fuel. Researchers
have reported that the problem of high fuel viscosity can be overcome by using
esters, blending and heating. In this study, attempts have been made to evaluate the
possibility of using vegetable oils as diesel f!lel substitute by modifying their
properties by means of preheating.
Engine performance evaluation has been carried out on the basis of both the first and
the second laws of thermodynamics. The first law of thermodynamics has been
employed to give a general macroscopic performance evaluation. In order to render a
critical look into the performance of the engine using preheated soybean oil fuel, the
second law of thermodynamics is also utilized. Although conventional performance
analysis shows an improvement in engine performance (especially, brake thermal
efficiency) due to preheating of soybean oil, the second-law analysis (known as
'availability analysis' or 'exergy analysis') reveals rather a different picture. It shows
that the second-law efficiency (known as 'availability efficiency') of the engine
running on. preheated soybean oil fuel is somewhat less than the brake thermal
efficiency of the same. Availability analysis also pinpoints the leakages of major
energy losses in terms of 'availability destruction' or 'availability loss' that is a
strong tool to ensure the best utilization of the energy input.
