Etude de la combustion de gaz de synthèse issus d'un processus de ...

Chapter 4
Pressure (bar)
7
6
5
4
3
2
1
Experimental P
Numerical P
Qw
500
400
300
200
100
Qw (kW/m 2 )
0
0 50 100 150 200 250 300
Time (ms)
0
Figure 4.46 – Pressure and heat flux for fluidized bed syngas-air at φ=0.8, P=1.0 bar, T= 293 K.
tel-00623090, version 1 - 13 Sep 2011
Pressure (bar)
7
6
5
4
3
2
1
0
Experimental P
Numerical P
Qw
0 50 100 150 200 250 300
Time (ms)
500
400
300
200
100
0
Qw (kW/m 2 )
Figure 4.47 – Pressure and heat flux for fluidized bed syngas-air at φ=1.0, P=1.0 bar, T= 293 K.
From these figures, it is possible to conclude that the code over-estimates the pressure
for fluidized bed syngas. The extremely low burning velocity of this syngas composition
makes gravity forces being felt within the chamber, which makes the burned gases to
move to the top of the chamber and the flame to propagate to the bottom as shown in
the figure 4.5. Therefore, the assumption of spherical combustion is no longer valid.
4.2.3.3 Influence of the pressure
Let us now verify if pressure effect is accurately reproduced by the code. Figures 4.48 -
4.49 shows pressure and heat flux for stoichiometric syngas-air mixtures at 5.0 bar.
133