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

5 Results
Ψ = 0.1695 (t Ψ = 5 s): Ψ = 0.2728 (t Ψ = 10 s): Ψ = 0.5378 (t Ψ = 18 s):
t = 0.938 s
t = 0.656 s
t = 0.656 s
t = 0.952 s
t = 0.666 s
t = 0.666 s
t = 0.966 s
t = 0.676 s
t = 0.676 s
t = 1.016 s
t = 0.734 s
t = 0.734 s
Figure 5.14: Flame Spread Sequence for Different Pre-Vaporization Rates. Flame spread occurs
from left to right. Time t = 0.000s corresponds to the start of ignition [208].
flame follows the blue flame region (cf. Chap. 2.1.1). The shape of this luminous
flame around each droplet tends to change from a wake flame during its
early phase to a quasi-spherical envelope flame for the rest of droplet burning.
The observable flattening of the flames in the horizontal direction is a result of
a decreased oxygen mass fraction [20]. If the droplets were moved closer, the
individual flames would increase in size until they merge and form a common
envelope flame or group flame with the droplets at the center simply vaporizing
(see Chap. 2.1.3). The area of the visible blue flame is larger for larger
pre-vaporization rates Ψ. On the other hand, the brightness of the blue flame
appears to be lower for Ψ= 0.5378 than for the other conditions. Additionally,
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