Environmental Engineering Reference
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measured instantaneously with a char
ge-coupled device (CCD) camera. The global
flame features observed under conditions of 21% O
showed the flame to be short and compact having the expected flame luminosity
and blue flame color; see
Figure 2.2a
.
In contrast, the flame observed with air having 3% O
and 50˚C air temperature
2
had extremely low luminosity and a very large volume; see
Figure 2.2b
.
The color
of the flame was found to be bluish green to green depending on the input conditions
of the air. (See the color pictures in preface.) These results suggest that combustion
under high temperature and low oxygen concentration air provide lower heat release
rates per unit volume compared to the flames obtained with 21% oxygen in the
combustion air. The low oxygen concentration and high temperature air flames had
very good flame stability limits compared to the normal air combustion case.
and 1010˚C temperature
2
2.2.1.1
Temperature Profiles
ame was measured with an R-type thermocouple (Pt-
Pt/Rh 13%) with a wire diameter of 0.05 mm. The thermocouple was coated with a
ceramic layer to alleviate catalytic effects of Pt in the flame. The temperature of diluted
(low oxygen concentration) and preheated air was measured at a location of 105.0 mm
upstream from the fuel nozzle using the R-type thermocouple. Then, 36 measurement
positions were selected in the test section and are shown in
Figure 2.3
. The X-axis is
along the direction of the fuel injection and the Y-axis is along the direction of airflow.
The results obtained with 21% oxygen in air at 35˚C are shown in
Figure 2.3a
,
and
The mean temperature of the fl
X mm
X mm
40
60
80
100 120 140
40
60
80
100 120 140
225
225
200
200
200
1100
400
175
175
1200
150
150
125
125
1300
600
100
100
800
75
75
1000
50
50
1100
25
25
Combustion air
(35 C,21%vol O )
2
Combustion air
(1200 C,4%vol O )
2
Fuel LPG
Fuel LPG
FIGURE 2.3
T
emperature distribution.
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