Environmental Engineering Reference
In-Depth Information
can lead to formation of complexes between oxidized biodiesel (i.e., aged biodiesel)
components and ZDDP. They also reported that lubricating oil dilution with aged
biodiesel may increase wear even with 5 % concentration (B05) or lower. Watson
and Wong (
2008
) found in oxidation test that there is substantial increase in lubri-
cant
s acidity upon dilution by B100. Jech et al. (
2008
) used a model tribometer
based on nanoscale wear volume coherence (nVCT) to investigate the lubricity
(i.e., wear volume) effect of biodiesel dilution. They reported that biodiesel con-
centrations of 10 % in the mineral diesel (B10) increased the wear slightly, but
higher concentrations (from 30 % upwards) induced lower progressive wear. Sulek
et al. (
2010
) presented results on the effects of methyl esters derived from rapeseed
bio-oils as additives of fuel, and they suggested that as little as 5 % of such additions
may decrease wear by up to 50 % and coef
'
cient of friction by up to 20 %.
A bus diesel engine with a mechanically controlled fuel injection system was
tested with biodiesel (B100) produced from rapeseed. Biodiesel usage improved the
pump plunger lubrication and reduced wear. Further, carbon deposits in the com-
bustion chambers did not vary signi
cantly, but they were noticeably redistributed.
In a computational study, it was reported that variations in the nozzle discharge
coef
cient have to be taken into account, if high accuracy of numerical simulations
is desired (Pehan et al.
2009
).
Although the compatibility of biodiesel with key components of an engine such
as cylinder, piston, piston rings, connecting rod, and bearings has posed a serious
challenge to the tribologists, they are yet to come up with a solution to control/
reduce tribological degradation of different metallic components. Some efforts have
been made to understand the corrosion and wear of automotive materials in diesel
and biodiesel. It was concluded beyond reasonable doubt that though biodiesel is
more corrosive than mineral diesel, it provides better lubricity in terms of wear and
friction (Fazal et al.
2014
).
Continued legislative pressure to reduce exhaust emissions from CI engines has
resulted in development of advanced fuel injection equipment. These advanced
injection systems generate higher fuel pressures and temperatures at the injector tip,
where deposit formation is initiated. In a research, an endurance test was carried out
for 250 h on 2 fuel samples, namely mineral diesel as baseline fuel and JB20 (20 %
Jatropha biodiesel and 80 % diesel) in a single-cylinder CI engine. Visual
inspection of the in-cylinder components showed carbon deposits on injectors for
both fuels. Scanning electron microscopy (SEM) and energy-dispersive X-ray
spectroscopy (EDX) analysis showed greater carbon deposits on and around the
injector tip for JB20-fueled engine compared to the mineral diesel-fueled engine.
Similarly, lubricating oil analysis revealed excessive wear metal concentration and
reduced viscosity for the engine fueled with JB20 (Liaquata et al.
2014
).
In an experimental study done by Lin et al. (
2013
), petro-diesel (D100) and
different concentrations of commercial biodiesel (B100, B50, B5) were blended
with a commercial engine oil at a
fixed volume ratio of 1:9 at two different tem-
peratures (room temperature and 150
C) to investigate the tribological effects of
biodiesels on the anti-wear performance of the engine oil. The anti-wear perfor-
mance of the engine oil blended with mineral diesel was reported to be worse than
°
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