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

Chapter 3
Three global parameters that characterize the quality of the combustion can be
obtained from pressure curves:
- Pressure gain:
- Combustion efficiency:
g
P
max
p
= (3.8)
Pi
P
max
η = (3.9)
P
v
- Combustion time, τ, is defined as the time since the spark plug to the peak of
pressure.
Table 3.2 shows the above combustion parameters for typical syngas-air mixtures
under various initial conditions in spherical chamber.
tel-00623090, version 1 - 13 Sep 2011
Table 3.2 – Syngas-air combustion parameters in spherical chamber.
Pi=0.5 bar P i = 1.0 bar P i = 5.0 bar
Parameter
φ=0.6 φ=0.8 φ=1.0 φ=1.2 φ=0.6 φ=0.8 φ=1.0 φ=1.2 φ=0.6 φ=0.8 φ=1.0 φ=1.2
Updraft
g p 5.39 5.61 6.08 5.81 4.87 5.65 6.09 5.79 4.42 6.28 6.73 6.22
τ (ms) 161.2 129.0 61.7 58.84 172.2 93.7 71.0 65.0 650.3 167.2 119.1 143.2
η 90% 85% 87% 86% 70% 85% 87% 86% 74% 90% 95% 92%
Downdraft
g p 5.40 6.11 6.35 5.90 5.45 6.16 6.44 6.04 5.34 6.21 6.60 6.15
τ (ms) 114.3 64.8 54.5 49.9 126.6 71.7 57.7 58.0 226.1 107.2 84.3 98.8
η 93% 95% 94% 91% 94% 96% 95% 93% 92% 96% 96% 94%
Fluidized bed
g p n.d. n.d. n.d. n.d. n.d. 5.58 5.70 n.d. n.d. 4.44 4.54 n.d.
τ (ms) n.d. n.d. n.d. n.d. n.d. 200.7 187.5 n.d. n.d. 753 713.5 n.d.
η n.d. n.d. n.d. n.d. n.d. 84% 88% n.d. n.d. 66% 71% n.d.
These parameters show that the combustion of stoichiometric syngas-air mixtures is
generally more efficient and faster than for other equivalence ratios.
Comparing the three typical syngas-air mixtures conclusion can be drawn that
downdraft syngas-air mixture has higher pressure gains, higher efficiency and lower
combustion times than remain syngas-air mixtures. These results could be endorsed to
the higher heat of reaction and hydrogen content of the downdraft composition.
3.2.4 Pressure measurement on RCM
The RCM described on 3.1.4 can work on two distinctive modes: single compression
and compression and expansion. Single compression is generally used for the study of
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