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

Experimental and numerical laminar syngas combustion
1
r ⎡
γ
b ⎛Pi ⎞ Pv
− P ⎤
= ⎢1− r ⎜
v
P ⎟ ⎥
⎢ Pv − P
⎣ ⎝ ⎠
i ⎥⎦
1
3
(4.13)
Where P i and P v are the initial and maximum pressure, respectively. The maximum
pressure was obtained by the chemical equilibrium calculation in the constant volume
condition. γ is the specific heat ratio of the mixture. P v and γ were calculated by Gaseq
package, which values are shown in the appendix B. r v is the radius of the chamber.
The stretched burning velocity, S u , of the propagating flame is calculated by the
following expression (Lewis and von Elbe, 1987):
S
u
2
1 1
-
⎛
⎞ 3
v ⎛ γ
γ
i ⎞ ⎛ i ⎞ v
-
r P P P P dP
= ⎜1-
⎟
3( Pv - Pi) ⎜
P
⎟ ⎜
P
⎟
⎝ ⎠ ⎜ ⎝ ⎠ Pv -P i ⎟ dt
⎝
⎠
A typical pressure curve is shown in the figure 4.25:
(4.14)
tel-00623090, version 1 - 13 Sep 2011
P v
P i
Time
Typical inquiry
region
Figure 4.25 – Typical pressure curve and inquiry region for burning velocity calculation.
Burning velocity is calculated from this type of pressure records in all points of the
pressure curve within the inquiry region indicated in figure 4.25. Low pressures are
excluded due to imprecision of the pressure derivative. High pressures are excluded
due to the inflection of the pressure curve caused by increasing thermal losses when
the flame approaches the chamber walls.
4.1.2.1 Pressure evolution
Figure 4.26 to 4.28 shows pressure evolution for typical syngas-air mixtures under
various equivalence ratios.
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