Environmental Engineering Reference
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10 -2
10 -2
Two-dimensional Air Flow
Two-dimensional Air Flow
12
a=40000s -1
a=1300s -1
2
10
8
a=24000s -1
a=640s -1
6
11
a=6900s -1
4
a=200s -1
2
0
0
1000
1500
2000
2500
1000
1500
2000
2500
Surface temperature, K
Surface temperature, K
(a)
(b)
FIGURE 2.129 Influence of the surface temperature on the combustion rate of a solid carbon
in room temperature airflow. (A. Makino, Combust. Flame, 81(2):166, 1990).The parameter
is velocity gradient. Data points are based on the test results, and the solid line indicates the
results of calculation.
combustion rate increased homogeneously and continuously with surface tempera-
ture toward a certain value.
The figure also shows the results of a case (for the velocity gradient of 10,000
s -1 ) in which the amount of supplied air was kept at a fixed level and the high
temperature air generator was kept out of operation. It is obvious that the combustion
rate was almost doubled due to increases in the flow rate of the oxidizing agent due
to thermal expansion when the high temperature air generator was operated. The
figure also includes the results of the test using room temperature airflow in which
the velocity gradient was maintained at 40,000 s -1 . The results show that the com-
bustion rate in high temperature airflow is lower than that in room temperature
airflow by about 15%.
2.5.4.5
Dynamic Analysis of Reactive Gas
2.5.4.5.1 Combustion Rate
The combustion of solid carbon (graphite) involves a surface reaction (2C + O 2
2CO and C + CO 2 → 2CO, for example) and a gas-phase reaction (2CO + O 2
2CO 2 ). These reactions influence each other and also influence the combustion rate. 68
In addition, it is also known that the formation of a CO flame is influenced by the
velocity gradient, the surface temperature, and oxygen concentration 69 and that the
combustion rate at the same surface temperature changes when a CO flame is
 
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