Combustion Phenomena of High Temperature Air Combustion - High Temperature Air Combustion: From Energy Conservation to Pollution Reduction - page 74

3000

2000

1000

0

0 500 1000 1500 2000

Preheating temperature, K

FIGURE 2.47 NO concentration in preheated flames with α = 0.2095.

varied to obtain flames with those values for the adiabatic flame temperature and T 0
> 298 K. For example, for T a = 1600 K, α ≤ 0.13; for T a = 1800 K, α ≤ 0.15.
2.3.2.2.3 Fuel Flux
Figure 2.48 shows the variation of burning velocity with α and air preheat temper-
ature for T a < 2200 K. The burning velocity for α = 0.15 is 1/9 of the value for α
= 0.06. From the figure, self-ignition can be thought to occur for conditions where
α ≤ 0.09.
The variation of the fuel flux is similar to that of the burning velocity: from 5.42
× 10 -4 mol/cm 2 ·s for α = 0.06 to 2.93 × 10 -4 mol/cm 2 ·s for α = 0.15. The fuel flux
is the product of the concentration of methane in the unburned mixture and the

30 2000

1500

20

1000

10

500

0 0

0 0.05 0.10 0.15 0.20

Oxygen ratio

FIGURE 2.48 Burning velocity and preheating temperature of flames with T a = 2200 K.