Environmental Engineering Reference
In-Depth Information
samples were treated to remove the moisture and particulates before sending them
into a portable
flue gas analyzer that was used for the global emission measurement.
The sampling probe was mounted on a two-dimensional linear traverse mechanism
which facilitated the axial and radial movement of the probe across the
fl
field.
Measurements were taken at 2 mm radial distance intervals at three different heights
corresponding to 25, 50, and 75 % of the visible
fl
ame
fl
flame length.
4.2.5 In-Flame Temperature Measurement
The in-
Pt/13 % Rh)
thermocouple with a bead diameter of 0.4 mm. Catalytic action was reduced by
coating the tip of the thermocouple with a
fl
ame temperature pro
les were measured using an R-type (Pt
-
fine layer of silica. The thermocouple
was positioned along the length of the
flame using a manually guided traverse
mechanism. Data acquisition was accomplished using LabView software. The
temperature readings were averaged over a period of 30 s with 1 Hz of sampling
rate and corrected for radiation, conduction, and convection losses (Jha et al.
2008
).
fl
4.2.6 Soot Volume Fraction
The path-integrated soot volume fraction was measured using laser attenuation
along with the application of Beer
s law and Mie scattering theory, as presented by
Yagi and Iino (
1962
). The soot volume fraction was computed using Eq. (
3
):
'
k
ln
I
0
I
s
F
v
¼
ð
3
Þ
k
k
d
where I
s
and I
o
are the incident and attenuated laser intensities, respectively; k
λ
is
the spectral extinction coefficient based on the refractive indices of the soot (Bryce
et al.
2000
);
flame thickness (beam
path) obtained from photographs. The spectral extinction coef
λ
is the employed laser wavelength; and
δ
is
fl
cient (k
λ
) was
assumed to be constant, corresponding to that of diesel soot. Previous measure-
ments have indicated that the refractive index of diesel soot was not signi
cantly
different from that of the soot formed in soy methyl ester
fl
flames (Choi
2009
).
A 5-mW helium
= 632.8 nm) was used as a light source with a power
detector. The beam attenuation due to the presence of soot was obtained by mea-
suring the intensity of light with and without
neon laser (
λ
-
field. The burner remained
stationary, with the laser and power detector aligned on a traversing mechanism to
obtain radial and axial pro
fl
ame
les. The voltage readings from the power detector were
digitally sampled at the rate of 10 Hz for 30 s using LabView software.
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