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

Chapter 4
4.1.1.1 Flame morphology
tel-00623090, version 1 - 13 Sep 2011
Bradley et al., (1998) shown that flame speeds become independent of ignition energy
when flame radius is greater than 6 mm. The existence of the critical flame radius was
also observed by Lamoureux et al., (2003) and Liao et al., (2004). Their studies also
gave approximately the same value. Thus, the flame radius is analyzed only beyond
that radius, at which the spark effects could be discounted. In order to define the upper
limit of the flame radius data exploration, the spherical pattern of the flame expansion
and the corresponding pressure should be taking into account. The criterion used for
sphericity considerations was a 0.5 mm radius difference between horizontal and
vertical directions, which gives in our experimental conditions an upper limit for the
radius of 20.0 mm. The maximum estimated experimental uncertainty is 8% for the
radius 6.0 mm using this criterion. This also arises from the pixel resolution of the
digital camera. Figure 4.1 shows schlieren images of updraft syngas-air flames at
various equivalence ratios and initial pressure of 1.0 bar and 293 K.
P i = 1.0 bar , T i = 293 K, φ=0.6
Time (ms) 4 5 6 7 8 9 10 11 12 13 14
Radius (mm) 6.5 7.6 8.6 9.5 10.5 11.4 12.2 13.2 13.9 14.9 15.6
P i = 1.0 bar, T i = 293 K. φ=0.8
Time (ms) 3 4 5 6 7 8 9 10 11 12 13
Radius (mm) 6.5 7.9 9.4 10.9 12.3 13.6 15.0 16.3 17.4 18.7 21.1
P i = 1 bar, T i = 293 K. φ=1.0
Time (ms) 3 4 5 6 7 8 9 10 11
Radius (mm) 6.9 8.7 10.6 12.3 14.1 15.7 17.4 18.9 20.6
P i = 1.0 bar, T i = 293 K. φ=1.2
Time (ms) 3 4 5 6 7 8 9 10 11 12
Radius (mm) 6.7 8.0 9.7 11.1 12.6 14.1 15.5 16.9 18.3 19.7
Figure 4.1 – Schlieren images of updraft syngas-air mixture flames at 1.0 bar.
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