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

Chapter 7
(Updtraft)
(Downdraft)
⎧ Su
0
=− φ + φ −
⎪
⎨α = φ − φ +
⎪
⎪⎩
β =− φ + φ −
2
0.413 1.056 0.355
2
4.881 9.952 6.731
2
1.469 2.786 1.561
2
⎧ S u 0
=− 0.45φ
+ 1.152φ
−0.354
⎪
⎨α =
2
0.988φ − 1.936φ
+ 2.502
⎪
2
⎪⎩
β =− 1.194φ + 1.967φ
−0.931
tel-00623090, version 1 - 13 Sep 2011
⎧Su
0
= 0.21φ
−0.073
⎪
(Fluidized bed) ⎨α
= 1.485φ
+ 0.639
⎪
⎩β
=− 1.4φ
+ 0.882
Conclusion can be drawn that the burning velocity decreases with the increase of
pressure. In opposite, an increase in temperature induces an increase of burning
velocity. The higher burning velocity value is obtained for downdraft syngas. This result
is endorsed to the higher heat value, lower dilution and higher volume percentage of
hydrogen in the downdraft syngas.
This information about laminar burning velocity of syngas-air flames is then applied on
a multi-zone numerical heat transfer simulation code of the wall-flame interaction
developed at the Laboratoire de Combustion et Détonique. The adapted code allows
simulating the combustion of homogeneous premixed gas mixtures within constant
volume spherical chamber in order to predict the quenching distance of typical syngasair
flames. Thus, it was possible to establish analytical expressions of quenching
distance for typical stoichiometric syngas-air flames.
δ q =450 P -0.79 (μm), P>0.3 MPa (Updraft)
δ q =300 P -0.89 (μm), P>0.3 MPa
(Downdraft)
Another major finding is that the code reproduces well the pressure evolution beyond
the validity of the burning velocity correlation established in this work for updraft and
downdraft syngas compositions. Fluidized bed syngas composition due to cellular
flame development, which violates the assumption of spherical flame was removed
from this study.
Engine-like conditions were experimentally reproduced in a rapid compression machine
(RCM) when working on two strokes mode simulating a single cycle of an internal
combustion engine. Stationary power applications usually use natural gas as fuel, thus
a methane-air mixture is also included in this work as a reference fuel for comparison
with the typical syngas compositions under study. A common practice in engine testing
for combustion diagnostic is, prior to the usual firing tests, to test the engine in motored
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