Environmental Engineering Reference
In-Depth Information
1600
2
0
0
1600
0
2
1600
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0
1600
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50
1600
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0.5
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1600
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1600
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COAL Flame
HFO Flame
FIGURE 2.107
Hydrocarbon concentration (ppmvd for coal flame at HTAC99 and vol% dry
for HFO flame at HTAC98).
tively), where velocity remains equal to the initial velocity. The measured low
velocities may be explained considering that during the measurements the central
air jet was not seeded. In the first two traverses, only a small amount of coal particles
is entrained by the air and accelerated from the recirculation velocity up to a high
inlet air velocity. That resulted in a poor signal in the LDA measurements in the
center of the air jet at the first two measured traverses and in a lower measured
velocity.
These considerations are confirmed by the calculation of the entrained mass flow
in the air jet.
Figure 2.110
shows the entrained mass flow in the central jet calculated
as the integral of the measured velocity within the jet boundary.
The calculation was performed only in the first four traverses because farther
downstream it was not possible to define the central air jet boundary. In the first
traverses the central jet boundary was considered the zero tangent condition in the
velocity profile. Such an integration is always associated with inaccuracies due to
the integration procedure, the assumption of the jet axial-symmetry and the errors
associated with temperature and gas composition measurements.
56
In the calculation
the gas composition is assumed to be similar to the flue gas, which has a density of
0.2 g/m
3
. Finally, the mass flow is corrected for the temperature effect of density.
Figure 2.109
shows that in the first two traverses the calculated mass flow is less
than the input mass flow. At the third and fourth traverses, the calculated entrainment
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