Environmental Engineering Reference
In-Depth Information
partial substitute for mineral diesel in developing economies. Transesteri
cation is
an appropriate and well-established method for chemical modi
cation of vegetable
oils, which produces a suitable diesel fuel alternative
. Biodiesel has
proved to be an engine friendly and environment friendly substitute for mineral
diesel. However, increased use of biodiesel has led to need of investigating the
effect of biodiesel on engine durability, lubricating oil as well as hardware com-
patibility. The effect of biofuels and of their blends with diesel on engine tribology
is not completely understood. Use of biodiesel as replacement fuel may lead to
substantial lubricating oil dilution, because biodiesel has higher boiling range than
mineral diesel. Since fuel interacts with the lubrication oil in the sump via fuel
dilution, it is necessary to understand the impact of biodiesel on the lubricant
properties. Oil consumption in heavy-duty diesel engines lies in ranges of
0.1
“
Biodiesel
”
0.2 % of the total fuel consumption.
Several studies have been performed to evaluate the feasibility of biodiesel
fueling in the vehicles. Materials compatibility issues observed with biodiesel
showed are largely related to enhanced corrosion of engine components, primarily
due to compositional differences among these fuels. On performance, emission, and
engine durability aspect, there is a general higher consensus among researchers
about reduced emissions as well as higher stickiness among components in addition
to issues such as injector coking and fuel
-
filter plugging (Fazal et al.
2011
).
2 Tribological Behavior of Biodiesels
The tribological behavior of various types of biodiesels has been examined in bench
tests, laboratory engine tests, and vehicle tests by several researchers (Arumugam
and Sriram
2012
; Uy et al.
2011
; Celik and Aydin
2011
; Sukjit and Dearn
2011
;
Haseeb et al.
2010
; Wain et al.
2005
). Few studies have investigated the effect of
biodiesels on engine durability, but they focused mostly on the viscosity and
neutralization number (total acid number [TAN] and total base number [TBN]) of
the oils or on the amount of metallic debris in the tested oils (Munoz et al.
2011
;
Sinha and Agarwal
2010
; Yuksek et al.
2009
; Agarwal
2005
).
Inspite of these studies looking at speci
c aspects, the tribological effects of
biodiesel vis-a-vis mineral diesel are not well understood. During combustion in a
diesel engine, biodiesel may be scrapped to the engine oil sump along with blow-by
gases and can dilute the lubricating oil and severely affect its lubrication performance.
Agarwal (
2005
) reported that viscosity of lubricating oil decreases with engine
run time, primarily due to increased dilution by biofuels. Fang et al. (
2007
) examined
the wear effects of biodiesel (B100) using various methods such as electrical contact
resistance measurement, high-frequency reciprocating rig, and four-ball testing.
They consistently observed that while fresh biodiesel might actually decrease wear,
aged biodiesel degradation products can interact with lubricating oil additives such
as zinc-di-alkyl-di-thio-phosphate (ZDDP) and adversely affect lubricant
s perfor-
mance. They concluded that excessive fuel dilution in lubricating oil by biodiesel
'
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