On the Formation of Nitrogen Oxides During the Combustion of ...

5.1 Droplets in Exhaust Gas Atmosphere
The main droplet simulations are conducted in the second step using the single
droplet model of Chapter 4.5. For all investigated equivalence ratios, the
initial conditions of the droplet atmosphere are preset with temperature T 0
and species mass fraction Y m,0 according to the exhaust gas of the respective
premixed flame. As the temperature of the exhaust gas atmosphere is well
above the auto-ignition temperature of C 10 H 22 [276], no particular ignition
modeling by an external heat source is required here (cf. Chap. 4.3).
Figure 5.1 depicts spatial profiles of temperature T and NO mole fraction X NO
for droplet combustion in such a hot exhaust gas atmosphere. The particular
2200
K
Temperature T
2150
2100
2050
Mole fraction of NO XNO
2000
2.0 x 10 −4
1.5 x 10 −4
1.0 x 10 −4
0.5 x 10 −4
t = 0.118 x 10 −3 s, D/D 0 = 99%
t = 0.427 x 10 −3 s, D/D 0 = 97%
t = 1.627 x 10 −3 s, D/D 0 = 90%
t = 7.026 x 10 −3 s, D/D 0 = 50%
t = 9.397 x 10 −3 s, D/D 0 = 1%
2.5 x 10 −4 Radial distance r
0.0 x 10 −4
0.000 0.002 0.004 0.006 0.008 m
Figure 5.1: Spatial Profiles of Temperature and NO Mole Fraction at Selected Times. A
droplet of the initial diameter D 0 = 100µm vaporizes and ignites in the hot exhaust
gas of a premixed flame, which itself has an equivalence ratio of φ= 0.8 [298].
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