Environmental Engineering Reference
In-Depth Information
mm
3
1200˚C.
The total flow rate of the diluted air was maintained constant at 15.0 /h.
By maintaining a fixed flow rate of diluted air, a similarity in the flow pattern between
the diluted air and the fuel flow could be maintained over the temperature range of
interest. It is recognized that complete similarity will require compensation for the
temperature changes that occur during the test run. The switching device incorpo-
rated in the facility allowed the flow direction in the regenerator to be changed after
a prescribed time duration. In the results, the switching device was allowed to change
the flow direction after every 30 s. The LPG fuel flow rate was maintained constant
at an energy release rate of 1.28 kW. The results have been obtained at an overall
air ratio of 12.6 with 21.0% O
. These
conditions represent air ratio values significantly larger than the theoretical value
for stable combustion.
The results presented in
Figure 1.4
show stable flame combustion conditions
with low oxygen concentration air (less than 5%) at air temperatures above about
800˚C. However, for air temperatures below 800˚C the flame stability was signifi-
cantly affected at less than 15% oxygen concentration in the combustion air. For
example, a stable flame at 700˚C could only be achieved at much higher oxygen
concentration of about 16%.
The physical appearance of the flame (e.g., flame color, size, shape, and global
flame structure) was found to significantly change when the concentration of oxygen
was decreased from 21 to 3% (by volume) while maintaining the air temperature
constant at about 1000˚C.
Figure 2.2
shows the result of flame intensity profiles
in air and 2.40 with 4.0% O
diluted air
2
2
Combustion air
(50 C,21%vol O
2
Combustion air
(1010 C,3%vol O
2
Fuel LPG
Fuel LPG
Light intensity
Light intensity
0.0
1.0
0.0
1.0
(a) Low temperature/normal oxygen
(b) High temperature/low oxygen
FIGURE 2.2
V
isible light intensity profile of flame.
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