Environmental Engineering Reference
In-Depth Information
particularly useful because it unambiguously expresses the amount of pollutant
formed per unit mass of fuel, independent of any dilution of the product stream
(Turns
2011
). The emission index is expressed as
v
i
v
co
þ v
co
2
N
MW
i
MW
fuel
EI
i
¼
ð
Þ
1
;
000
1
where
v
i
,
v
co
and
v
co
2
are the mole fraction of the species, CO and CO
2
, respec-
tively, N is the number of atoms of carbon in a mole of fuel, and MWi
i
and MW
fuel
are the molecular weights of the species, i and fuel, respectively. It is assumed that
all the carbon in the fuel is converted into CO and CO
2
with negligible amounts of
soot. This assumption was found to be valid since the
fl
ames tested were not
smoking enough to produce signi
cant amount of solid carbon in the exhaust.
4.2.3 Radiative Heat Fraction
A wide view angle (150
°
) high-sensitivity pyrheliometer was used to measure the
total radiation from the
flame. The pyrheliometer had a linear output with a
responsivity of 44.56 mV per kW/m
2
and was located far enough (50 cm) from the
burner so that its view angle covered the entire
fl
fl
flame length and the
fl
flame could be
assumed as a point source. The measured radiative heat
flux was sampled at 1 Hz
for time duration of 3 min using LabView software. The background radiation was
subtracted from the total radiation to obtain the
fl
fl
flame radiation and was expressed
as the radiative fraction of heat release, F:
2
4
p
L
Q
mLHV
F
¼
ð
2
Þ
Here, L is the distance from the
fl
flame centerline to the pyrheliometer, Q is the
corrected radiative heat
flow rate of the liquid fuel,
and LHV is the lower heating value of the liquid fuel tested. The radiative fraction
of heat release is the fraction of the heat content of the fuel that is lost as radiation
from the
fl
ux measured,
is the mass
fl
ṁ
fl
flame and is an indirect measure of the soot content in the
fl
ames.
4.2.4 In-flame Species Concentration
The in-
ame gas concentration measurements were performed using a stainless
steel sampling probe (1.75 mm ID and 3.2 mm OD); the diameter of the sampling
probe was large enough to prevent clogging due to soot accumulation. The gas
fl
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