Page 388 - Advances in Eco-Fuels for a Sustainable Environment

342 Advances in Eco-Fuels for a Sustainable Environment

influence on lubrication behavior is kinematic viscosity [14]. The study identified
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higher viscosity in pure ecofuel (about 6.04mm /s) at 40°C using the ASTM D445
standard. On the other hand, the kinematic viscosities of the diesel and B20 blend were
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found to be about 4.10mm /s and 4.49mm /s, respectively, at the same condition. The
higher viscosity of the ecofuel indicates that the ecofuel can strengthen the lubrication
film between two metal surfaces, as reported in the literature [15]. It has a strong influ-
ence to reduce the coefficient of friction. In addition, flashpoint temperature is another
property of the fuel that indicates the safety of the lubrication film and sustainability at
a high temperature, which is generated due to friction [8, 16]. The result revealed that
the ecofuel and its blend have a higher flash point compared to diesel fuel. The key
index of the lubricating characteristics is the lubricity in μm of the fuel, which is mea-
sured using the ASTM D6079 standard for the tested fuel. The study revealed that the
lubricity of the pure ecofuel is 345μm whereas the diesel and B20 blend are found to
be 122μm and 253μm, respectively. Furthermore, the study found the lower acid
value of the ecofuel compared to the standard range, which indicates the fuel is very
close to neutral and is safe for the metal surface. Moreover, other important fuel prop-
erties such as cetane number, glycerol, and metal content are identified, which have a
direct and indirect influence on engine emission [17, 18]. The literature reported that
the ecofuel could be used up to 20% by blending with diesel fuel in the modern diesel
without any modification of the engine system [19–22]. Therefore, the study investi-
gated the tribological behavior of B20 blend and diesel fuel, as discussed briefly in the
following section.

12.3.2 Analysis of coefficient of friction
The coefficient of friction (COF) is one of the key parameters to analyze the tribolog-
ical characteristics of the tested fuels. In this study, COF was evaluated for both B20
ecofuel and diesel using the ASTM D4172 standard for a period of 1h. The first 10s of
the test were considered as the run-in period. In this period, COF was unstable and
exhibited a higher magnitude. The study also identified the transition period (before
reaching the steady state condition) after 10s to 200s of the test period due to several
reasons as reported by Fazal and Haseeb [11]. The variation of COF became stable
after 200s and followed a steady-state condition until the end of the test. After the
run-in period, the contact surface of the tested balls became smoother and prominent
asperities were flattened or removed.
Fig. 12.2 demonstrates the comparison of the variation of COF for diesel and B20
ecofuel during the run-in period of the test. The figure shows a similar trend of COF
for both fuels, but ecofuel exhibited a lower magnitude of COF compared to diesel due
to the higher density, viscosity, and lubricating properties of the ecofuel, as shown in
Table 12.2. Similar reasons are also reported in the literature [4]. It has been noted that
diesel exhibits a higher COF compared to the ecofuel blend with a longer run-in period
as well as a transitional period, as shown in Fig. 12.3. The lower COF for ecofuel
implies the capability of ecofuel to prompt a change of unsteady state to steady state
by reducing friction (Fig. 12.3).