Environmental Engineering Reference
In-Depth Information
in
uence of the driving cycle on NO
x
and CO emissions; it was found that the
emissions were reduced with the use of biofuels over certain parts of the cycle.
Hashimoto et al. (
2008
) studied the spray combustion of PME and diesel fuel at
atmospheric pressure. Both emission indices, NO
x
per unit mass of fuel (g-NO
x
/kg-
fuel) and NO
x
emission per unit heating value (g-NO
x
/MJ fuel) for PME, were
lower than those for diesel fuel. It was also found that the NO
x
emission level was
reduced with decreasing fuel kinematic viscosity for both fuels and was attributed
to the decrease in Sauter mean diameter (SMD) of the spray.
Studies of pollutant emissions from engines fueled with other biofuels and
biofuel blends have been carried out by several researchers (McCormick et al.
2001
;
Canakci and van Gerpen
2003
; Tsai et al.
2010
). These engine studies do not shed
light on the effects of chemical structure of the fuel on the combustion due to a
number of complexities, such as atomization, vaporization, and turbulent mixing
that occur in an engine. Hence, for this study, we adopted the technique developed
in the
fl
first phase of our program mentioned above.
4 Methods and Materials
4.1 Experiment Setup
A schematic diagram of the setup is presented in Fig.
1
. The experiments were
conducted in a large steel combustion chamber (76 cm by 76 cm and 150 cm in
height). The burner used for the experiments was housed within the chamber at its
bottom center. The walls of the chamber contained windows provided with
removable slotted metal sheet covers measuring 96 cm
25 cm to allow optical
access. The top of the combustion chamber was open to atmosphere through an
exhaust duct. The ambient pressure of the laboratory was maintained at slightly
above the atmospheric pressure (
×
20 Pa) to provide a positive draft inside the test
chamber to prevent leakage of the combustion products into the laboratory.
A stainless steel circular tube (ID of 9.5 mm and OD of 12.7 mm, Fig.
2
) with a
beveled rim served as the burner. This burner provided a stable, laminar, and
repeatable
*
fl
flame and has been used in previous studies (Love et al.
2009a
; Singh
et al.
2013
).
In order to vaporize the fuel completely without liquid-phase pyrolysis that
could lead to coking of the fuel, the liquid was injected into a high-temperature
air
ow was provided in a 12.7 mm (OD) steel feed line tubing with
heating tape wrapped around it. The heating tape was connected to a proportional
temperature controller which was continuously monitored; the air temperature
upstream and downstream of the fuel injection location was measured with K-type
thermocouples embedded in the feed line and was also monitored. The air
fl
ow. The air
fl
fl
ow
°
temperature at the fuel injection location was maintained at 390
C, which was
suf
ciently high above the
final boiling point of the fuels so as to completely
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