Environmental Engineering Reference
In-Depth Information
biodiesel blended fuels at both temperatures. At room temperature, the physical
adsorption and local hydrodynamic effects of the blended oils dominate the tribo-
logical behavior, and at 150
°
C, biodiesel seems to promote the growth of a reaction
film with anti-wear additives present in lubricating oil and enhances the growth rate
of chemical
films. However, an excessive biodiesel concentration causes tribo-
chemical wear and reduces anti-wear performance (Lin et al.
2013
). Molina et al.
(
2014
) concluded that any degree of mineral oil dilution by the tested biodiesels can
reduce the wear protection performance and the viscosity of the engine oil even at
small contaminating amounts, such as from 5 to 30 %.
3 Lubricating Oil Degradation
The lubricant transports protective chemicals to the sites where they are required and
transports waste products away from the sites, where they are generated (Tung and
McMillan
2004
). Fuel chemistry plays an extremely important role in the perfor-
mance and useful life of the lubricating oil (Fazal et al.
2011
; Truhan et al.
1995
).
Properties of lubricating oil change with usage due to changes in chemical com-
position of oil and addition of external contaminants. These contaminants include
(i) chemical constituents such as oil oxidation products and acids formed by com-
bustion gases, (ii) particulates from dust and dirt from external sources, (iii) wear
metal debris, and (iv) combustion soot (Truhan et al.
1995
). Oxygenated chemical
constituents of biodiesel make it more reactive than mineral diesel. Properties of
lubricating oil change with its usage due to fuel dilution and addition of contami-
nants from the engine due to wear, carbonaceous materials and impurities entering
along with intake air (Truhan et al.
1995
). Biodiesel is comparatively more chem-
ically reactive than mineral diesel due to presence of oxygen in the molecular
structure of the biodiesel (Schumacher et al.
1996
). Differences in physical prop-
erties of biodiesel and mineral diesel cause different levels of fuel dilution of
lubricating oil. Hence, the effect of biodiesel on the lubricating oil degradation needs
to be evaluated in long-duration engine tests before taking decision about their large-
scale usage. There are very few studies reporting the long-term effects of biodiesel
on the lubricating oil degradation in the open literature. Karanja and Jatropha oils are
being considered as important feedstocks with a potential of producing biodiesel on
large scale because they are available in surplus quantities throughout South Asia
and other parts of the world (Agarwal and Dhar
2010
,
2012
).
4 Effect of Biodiesel on Engine Wear and Durability
In diesel engines, components such as piston ring, cylinder liner, piston, bearings,
crankshaft, tappet, and valves are subjected to wear. The wear particles are removed
by the lubricating oil and
finally transported to the oil sump. Wear particles remain
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